A visible light-responsive monolithic tungsten trioxide-based photocatalytic foam ceramic, its preparation method and application

Abstract

This application discloses a visible light-responsive monolithic tungsten trioxide-based photocatalytic foam ceramic, its preparation method, and its application. The method includes: uniformly dispersing organic additives and pH adjusters in deionized water to form a homogeneous solution; adding tungsten trioxide powder, sintering aids, defect control agents, and photocatalytically active components to the solution in batches, uniformly dispersing them to form a suspension slurry; adding fiber / whisker reinforcement phases to form a composite slurry; impregnating organic foam in the composite slurry, followed by desizing and drying to form a composite; subjecting the composite to gradient-heating heat treatment to remove organic matter, forming a green body; and finally sintering to obtain the finished product. Furthermore, based on the electronic characteristics and molecular structure of the target pollutant, specific heterojunction systems can be matched and constructed to achieve highly efficient targeted degradation of emerging pollutants such as antibiotics, perfluorinated compounds, and phenols. The resulting photocatalytic foam ceramic possesses high structural strength, high visible light photocatalytic activity, and excellent environmental stability.

Description

Technical Field

[0001] This application relates to a visible light responsive monolithic tungsten trioxide-based photocatalytic foam ceramic, its preparation method and application, belonging to the field of inorganic non-metallic functional materials technology. Background Technology

[0002] Photocatalysis, with its advantages of mild reaction conditions, no secondary pollution, and controllable treatment costs, has become a core technological support for purifying emerging pollutants in water bodies. In the evolution of this technology, monolithic photocatalytic foam ceramics have emerged as a research frontier and a new application direction in the field of photocatalytic water treatment. These materials, prepared from photocatalytic powders, possess a three-dimensional interconnected porous structure. Their core essence lies in effectively overcoming the bottlenecks of traditional photocatalysis technologies, such as the difficulty of separating nanoparticle slurries, the low specific surface area of ​​immobilized catalysts, and the easy loss of active components from supported photocatalytic foam ceramics, through a "structure-function integration" design concept. This provides feasible support for the large-scale implementation of water treatment technologies.

[0003] Tungsten trioxide (WO3), a typical visible-light-responsive photocatalyst, has a band gap of 2.6–2.8 eV, enabling it to efficiently capture visible light wavelengths less than 460 nm in the solar spectrum. Its photon utilization efficiency is far superior to that of titanium dioxide (TiO2), which is only responsive to ultraviolet light and can only utilize about 5% of the solar spectrum. From a band structure perspective, WO3's valence band position is as high as +3.1 eV (vs NHE), generating highly oxidizing photogenerated holes, thereby inducing high concentrations of photogenerated vacancies. The generation of OH hydroxyl radicals endows it with efficient and broad-spectrum oxidative degradation performance against various organic pollutants.

[0004] However, the preparation and application of monolithic WO3-based photocatalytic foam ceramics still face multiple unique technical bottlenecks, which overlap with the common problems of existing photocatalytic foam ceramics: on the one hand, existing photocatalytic foam ceramics generally suffer from low mechanical strength, easy loss of active components, and insufficient catalytic specificity; on the other hand, the WO3-based system faces specific challenges—firstly, WO3 is prone to thermal decomposition and the formation of WO3 vapor at temperatures above 900℃, which significantly compresses the controllable sintering temperature window; secondly, during high-temperature sintering, W... 6 + Easily over-reduced to W 5 +, generating tungsten bronze-type defect phase (WO3) 3-x ( ), induces lattice distortion and color center formation, significantly weakens the separation efficiency of photogenerated carriers, and seriously damages photocatalytic activity; third, there is still a lack of systematic defect control strategies for WO3-based foam ceramics, as well as a precise matching design mechanism based on the characteristics of pollutant molecules and the heterojunction structure of catalysts.

[0005] To address the overlapping challenges of common problems and specific issues mentioned above, there is an urgent need to develop a type of monolithic tungsten trioxide-based photocatalytic foam ceramic that combines high mechanical strength, excellent structural stability, visible light response characteristics, and targeted pollutant degradation capabilities. The applicant previously developed a method for preparing monolithic BiVO4 photocatalytic foam ceramics. This method utilizes an organic foam impregnation-high-temperature sintering process to achieve an effective in-situ integrated construction of active components and a ceramic matrix. This method can significantly improve mechanical strength, inhibit the loss of active components, and optimize mass transfer efficiency while imparting visible light response properties to the material. However, this method is specific to the BiVO4 system and does not address the high-temperature volatilization of WO3 in monolithic WO3-based photocatalytic foam ceramics. 6 + The specific problem of over-reduction, and the lack of a precise matching mechanism between pollutants and heterojunctions.

[0006] To address the aforementioned technical problems of existing WO3-based photocatalysts, this application aims to overcome the material bottleneck in the engineering application of photocatalytic water treatment technology by further optimizing sintering parameters, introducing targeted defect control strategies, and constructing material design principles based on pollutant molecular characteristics. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a visible light-responsive monolithic tungsten trioxide-based photocatalytic foam ceramic, its preparation method, and its application. This invention significantly improves the material's mechanical properties by in-situ introducing a high aspect ratio reinforcing phase to construct a three-dimensional interlocking network; it also lowers the sintering temperature by introducing sintering aids, and fixes the W phase by in-situ reaction between the photocatalytic active component and tungsten trioxide to generate a new tungstate phase. 6+ This synergistically suppresses the high-temperature volatilization of tungsten trioxide; simultaneously, a defect control agent is introduced to suppress W through solid solution substitution and grain boundary segregation mechanisms. 6+ Excessive reduction, excessive oxygen vacancy generation, lattice distortion, and abnormal grain growth maintain the material's high specific surface area and porosity. By precisely designing photocatalytic heterojunctions, the separation efficiency of photogenerated carriers is optimized. At the same time, based on the matching mechanism between pollutant molecular characteristics and photocatalytic heterojunctions, targeted and efficient degradation of different emerging pollutants is achieved, providing a material solution with both structural robustness and functional specificity for the engineering application of photocatalytic water treatment technology.

[0008] To achieve the above objectives, the technical solution adopted in this application is as follows:

[0009] This application provides a method for preparing a visible light-responsive monolithic tungsten trioxide-based photocatalytic foam ceramic, comprising the following steps: Step S1: Preparation of tungsten trioxide-based composite slurry Organic additives and pH adjusters are added to deionized water and dispersed evenly to form a homogeneous solution; tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents are added to the homogeneous solution in batches and dispersed evenly to form a tungsten trioxide-based suspension slurry; fiber and / or whisker reinforcing phases are added to the suspension slurry and dispersed evenly to form a tungsten trioxide-based composite slurry; Step S2: Preparation of tungsten trioxide-based foam ceramic wet blank The organic foam is completely immersed in the tungsten trioxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and excess slurry on the surface is removed by squeezing or centrifugation; then drying treatment is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the tungsten trioxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a wet tungsten trioxide-based foam ceramic blank. Step S3: Preparation of tungsten trioxide-based foam ceramic green body The tungsten trioxide-based foam ceramic green body obtained in step S2 is first air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried green body is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while tungsten trioxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phases are initially sintered together to form a tungsten trioxide-based foam ceramic green body with a three-dimensional interconnected pore structure. Step S4: Sintering and Heterogeneous Structure Construction The green body obtained in step S3 is subjected to controlled sintering heat treatment. Under the action of sintering aids, tungsten trioxide and photocatalytic active components form a continuous and dense ceramic skeleton network through particle fusion and phase boundary bonding, effectively reducing the sintering temperature and ensuring the structural integrity of the three-dimensional interconnected channels. At the same time, the defect control agent inhibits W during high-temperature sintering through solid solution substitution and grain boundary segregation mechanisms. 6+ Excessive reduction, excessive generation of oxygen vacancies, lattice distortion, and abnormal growth of WO3 grains are controlled to keep the grain size within a small range, maintaining a high specific surface area and porosity of the material. During sintering, the reinforcing phase and the foam ceramic skeleton are firmly bonded together. The components construct band-matched heterojunction interfaces or generate new photocatalytically active phases in situ through solid-phase diffusion and interfacial reactions. The electronic structure of the heterojunction interface or the new photocatalytically active phase is precisely matched with the molecular characteristics of the target pollutant, significantly improving the separation efficiency of photogenerated carriers and the interfacial reaction activity. Finally, a visible light-responsive monolithic tungsten trioxide-based photocatalytic foam ceramic is obtained. The three-dimensional skeleton of this ceramic is composed of a continuous network of photocatalytic functional phases, which has excellent mechanical strength, high photocatalytic activity, and specific and efficient degradation ability for the target pollutant.

[0010] In some embodiments, in step S1, the average particle size of the WO3 powder is 10 nm-80 μm, preferably 500 nm-20 μm, and can be selected from any one or a combination of γ-WO3 (monoclinic phase, room temperature stable phase), β-WO3 (tetragonal phase), commercial WO3 powder, or modified powder thereof; the modified WO3 powder is a powder obtained by any of the following modification methods: (1) Cation doping, wherein the cation is selected from Li + Na + K + 、Rb + Cs + Mg² + Ca² + Sr² + Ba² + Al³ + Ga³ + In³ + Sn 4+ Sb³ + Sb 5+ Bi³ + ,Sc³ + Ti 4+ V³ + V 4+ V 5+ Cr³ + Cr 4+ Mn² + Mn³ + Mn 4+ Fe² + Fe³ + Co² + Co³ + Ni² + Ni³ + Cu² + Zn² + Y³ + Zr 4+ 、Nb 5+ Mo 6+ Ru 4+ 、Rh³ + Pd² + Ag + La³ + Ce³ + Ce 4 + Pr³ + Pr 4+ 、Nd³ + Sm³ + Eu³ +Gd³ + Tb³ + 、Tb 4+ Dy³ + Ho³ + Er³ + Tm³ + Yb³ + Lu³ + Hf 4+ Ta 5+ Re 4+ Re 6+ Os 4+ Ir 4+ Pt² + Pt 4+ and Au³ + Any one or more of the following, with a doping concentration of 0.1-15 at% (2) Anion doping, wherein the anion is selected from any one or more of B, C, N, F, P, S, Cl, Br and I, and the doping concentration is 0.5-10 at% (3) Oxygen vacancy regulation, with an oxygen vacancy concentration of 10 18 -10 21 cm -3 ; (4) Defect engineering modification, dislocation / grain boundary density 10 14 -10 16 cm -2 ; The modified powder still possesses semiconductor properties, with a band gap ranging from 1.5 to 5.5 eV; The photocatalytic active component is an inorganic oxide powder with semiconductor properties, and its band gap ranges from 1.5 to 5.5 eV; it is selected from at least one component from the following I) - V); I) Single metal oxides The general chemical formula is M m O n M is a single metallic element, m = 1-3, n = 1-5; including one or more of TiO2, ZnO, Bi2O3, Fe2O3, Cu2O, V2O5, MoO3, SnO2, MnO2, ZrO2, Ga2O3, Nb2O5, Ta2O5, In2O3, GeO2, RuO2, IrO2, Co3O4, NiO, Mn3O4, CuO, Ag2O, CoO, MnO, SnO, Sb2O3, Fe3O4, and Au2O and their modified derivatives; II) Composite metal oxides Composed of two or more metal cations, and further subdivided according to crystal structure as: a) Perovskites and their derived phases: general formula ABO3 or A (n+1) B n O (3n+1) , where n is an integer from 1 to 3, A is selected from at least one of La, Bi, Ba, Sr, Ca, Pb, Na and K, and B is selected from at least one of Ti, Zr, Hf, Nb, Ta, W, Mo, V, Cr, Mn, Fe, Co, Ni, Al, Ga and Sn; b) Spinel-type oxides: with the general formula AB2O4, wherein A is selected from at least one of Mg, Zn, Ni, Co, Cu, Fe, Mn and Li, and B is selected from at least one of Al, Ga, Cr, Fe, Mn, Co and Ti; c) Layered oxyacid salts having a layered crystal structure with an interlayer spacing of 0.5 nm to 1.5 nm, selected from at least one of the following: c1) Layered titanates, with the general formula A2Ti3O7 or ATi2O5, wherein A is selected from H, Li, Na, K, Rb or Cs; c2) Protonated layered niobates or tantalates, with the general formula HNb3O8 or HTa2O6; c3) Aurivillius phase bismuth-based oxides, selected from Bi2WO6, Bi2MoO6, Bi4Ti3O 12 At least one of them; c4) Layered nickelates, with the general formula ANiO2, wherein A is selected from Li or Na; d) Other functional oxoacid salts, selected from at least one of the following groups: d1) Scheelite-type oxides, with the general formula AWO4, AMoO4 or AVO4, wherein A is selected from Bi, Ca, Sr, Zn or Pb; d2) Perovskite-type rare earth ferrates, with the general formula LnFeO3, wherein Ln is selected from La, Pr, Nd or Sm; d3) Pyrochlore-type oxides, with the general formula Ln2B2O7, wherein Ln is selected from La, Gd, Sm or Nd, and B is selected from Ti, Zr or Sn; d4) Tungsten bronze type oxide, with the general formula M x TO3, where T is selected from W, Nb, or Ta, M is selected from Na or K, and 0.1 ≤ x ≤ 1.0; d5) Olivine-type oxides, with the general formula M2SiO4 or M2GeO4, wherein M is selected from Mg, Zn, Fe or Mn; d6) Inverse spinel-type stannate Zn2SnO4; d7) Copper-iron ore type oxides, with the general formula CuMO2, wherein M is selected from Fe, Al, Ga or Cr; III) Rare earth-based oxides a) Single rare earth oxide Ln a O x It covers all oxide systems corresponding to rare earth elements (except Pm), including: where Ln is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, a = 1–2, x = 1.5–3; b) Rare earth composite oxides: including perovskite-type LaMO3, NdMO3, ScMO3, YMO3, PrMO3, SmMO3, EuMO3, GdMO3, TbMO3, DyMO3, HoMO3, ErMO3, TmMO3, YbMO3, and LuMO3, where M is selected from transition metals Fe, Co, Sc, Ti, V, Cr, Mn, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, and W. Re, Os, Ir, Pt, Au, or Hg; pyrochlore-type Gd₂Ti₂O₇, Y₂Zr₂O₇, Sc₂Ti₂O₇, La₂Ti₂O₇, Ce₂Ti₂O₇, Pr₂Ti₂O₇, Nd₂Ti₂O₇, Sm₂Ti₂O₇, Eu₂Ti₂O₇, Tb₂Ti₂O₇, Dy₂Ti₂O₇, Ho₂Ti₂O₇, Er₂Ti₂O₇, Tm₂Ti₂O₇, Yb₂Ti₂O₇, Lu₂Ti₂O₇; bismuth rare earth co-doped oxides Bi. 1-x Ln x VO4, wherein Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y, x = 0.1-0.5, and at least one of the layered rare earth oxides La2O2CO3, Pr4O7, Ce2O2CO3, Nd2O2CO3, Sm2O2CO3, Eu2O2CO3, Gd2O2CO3, Tb2O2CO3, Dy2O2CO3, Ho2O2CO3, Er2O2CO3, Tm2O2CO3, Yb2O2CO3, Lu2O2CO3, Sc2O2CO3, Y2O2CO3; the interlayer spacing of the layered rare earth oxide structure is 0.8-1.2 nm; IV) Frontier structural metal oxides a) High-entropy oxides: general formula is (M1, M2, ... M n ) a O M1, M2, ..., Mn are at least five different metallic elements, each independently selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mg, Al, Li, Zr, Nb, Mo, Sn, Hf, Ta, W, or Ce, with each metallic element accounting for 5% to 35% of the total metallic elements, and the configuration entropy ΔS of the high-entropy oxide is... mix ≥ 1.5R, where R is the ideal gas constant 8.314 J·mol - ¹·K - ¹; (b) A two-dimensional nano-metal oxide, wherein the matrix material of the two-dimensional nano-metal oxide is selected from at least one of TiO2, MnO2, MoO3, V2O5, Co3O4, Fe2O3, SnO2, ZnO and Nb2O5, has a plate-like or layered morphology, has a thickness of 0.5 nm to 10 nm, has a lateral dimension to thickness ratio ≥ 50, and the two-dimensional nano-metal oxide has preferentially exposed crystal planes, wherein the crystal planes are selected from at least one of the {001}, {010}, {100} and {110} plane families; c) MOF-derived porous oxides, wherein the MOF-derived porous oxides are obtained by heat treatment conversion of metal-organic framework precursors, wherein the metal center of the precursor is selected from at least one of Zn, Co, Fe, Cu, Zr, Ti, Ni and Al, and the resulting oxides retain the morphological characteristics and pore structure of the precursors, with a specific surface area ≥ 50 m² / g, pore volume ≥ 0.1 cm³ / g, and pore size distribution spanning from micropores to mesopores, ranging from 0.5 nm to 50 nm; (5) Precursor compounds: the water-insoluble oxalates and / or carbonates corresponding to each single metal oxide in the photocatalytic active components, wherein the precursor compounds decompose in situ during sintering heat treatment to generate the corresponding photocatalytic active oxides; specifically including but not limited to: zinc oxalate (ZnC2O4), ferrous oxalate (FeC2O4), copper oxalate (CuC2O4), nickel oxalate (NiC2O4), cobalt oxalate (CoC2O4), manganese oxalate (MnC2O4), tin oxalate (SnC2O4), bismuth carbonate (Bi2(CO3)3), lanthanum carbonate (La2(CO3)3), cerium carbonate (Ce2(CO3)3); wherein, “insoluble in water” means: solubility in deionized water at 25°C ≤ 0.1 g / 100 mL; the precursor compounds must meet the following requirements: decomposition temperature between 200-1200°C, residual carbon content after decomposition < 0.1 wt.%, and no introduction of impurity anions harmful to photocatalytic activity; V) The photocatalytic active component described in any of I) to IV) above is modified using one or more of the following methods, and the resulting powder satisfies a band gap of 1.5-5.5 eV: a) Cation doping, wherein the cation is selected from Li + Na + K + 、Rb + Cs + Mg² + Ca² + Sr² + Ba² + Al³ + Ga³ + In³ + Sn 4+ Sb³ + Sb 5+ Bi³ + ,Sc³ + Ti 4+ V³ + V 4+ V 5+ Cr³ + Cr 4+ Mn² + Mn³ + Mn 4+ Fe² + Fe³ + Co² + Co³ + Ni² + Ni³ + Cu² + Zn² + Y³+ Zr 4+ 、Nb 5+ Mo 6+ Ru 4+ 、Rh³ + Pd² + Ag + La³ + Ce³ + Ce 4 + Pr³ + Pr 4+ 、Nd³ + Sm³ + Eu³ + Gd³ + Tb³ + 、Tb 4+ Dy³ + Ho³ + Er³ + Tm³ + Yb³ + Lu³ + Hf 4+ Ta 5+ Re 4+ Re 6+ Os 4+ Ir 4+ Pt² + Pt 4+ and Au³ + At least one of them, with a doping ratio of 0.1-15 at%; b) Anion doping, wherein the anion is selected from one or more of B, C, N, F, P, S, Cl, Br and I, and the doping ratio is 0.5-10 at% c) Oxygen vacancy regulation, with an oxygen vacancy concentration of 10. 18 -10 21 cm -3 ; d) Defect engineering modification, dislocation / grain boundary density 10 14 -10 16 cm -2 ; The amount of the photocatalytic active component added is 5-80 wt.% of the tungsten trioxide powder mass; the amount of the precursor compound added is based on the theoretical mass of the corresponding photocatalytic active oxide generated by its complete thermal decomposition, i.e., oxide equivalent. The sintering aid is selected from at least one of the following components: (a) Low melting point oxides These sintering aids partially melt within the sintering temperature window, providing a transient liquid phase to promote mass transfer and densification between WO3 particles. They include the following components: bismuth trioxide (Bi2O3), vanadium pentoxide (V2O5), boron trioxide (B2O3), molybdenum trioxide (MoO3), tellurium dioxide (TeO2); antimony trioxide (Sb2O3), and silver oxide (Ag2O). (b) Eutectic oxides These sintering aids may have individual melting points higher than 900°C, but when they form a binary or multi-component system with WO3, their eutectic temperature is significantly lower than the melting points of each component, thus forming an activated liquid phase within the sintering temperature window. This phase includes the following components: copper oxide (CuO), nickel oxide (NiO), zinc oxide (ZnO), iron oxide (Fe2O3), tin oxide (SnO2), cobalt oxide (CoO / Co3O4), manganese oxide (MnO2 / Mn2O3 / MnO / Mn3O4), indium oxide (In2O3), gallium oxide (Ga2O3), titanium oxide (TiO2), cadmium oxide (CdO), silver oxide (Ag2O), and germanium oxide (GeO2). (c) Network forming agent These sintering aids form a low-viscosity glassy liquid phase at the sintering temperature, filling the gaps between WO3 particles. Surface tension drives the rearrangement of the WO3 particles, achieving low-temperature liquid-phase sintering. Simultaneously, the W3 in the glass network... 6+ It can be bonded to Si-OW or POW bridging bonds to stabilize the valence state of W, and includes the following components: silicon dioxide (SiO2), phosphorus pentoxide (P2O5), germanium dioxide (GeO2), tellurium dioxide (TeO2), boron trioxide (B2O3), vanadium pentoxide (V2O5), antimony pentoxide (Sb2O5), and antimony trioxide (Sb2O3). (d) Network modifiers These sintering aids reduce liquid phase viscosity by breaking the oxygen-bridged bonds (WOW) in the glass network, promoting the rearrangement and densification of WO3 particles in the liquid phase; at the same time, they can form alkali metal / alkaline earth metal tungstates with WO3 to regulate the sintering path, including the following components: magnesium oxide (MgO), calcium carbonate (CaCO3), lithium carbonate (Li2CO3), barium carbonate (BaCO3), and strontium carbonate (SrCO3). (e) Pre-synthesized tungstate These sintering aids are pre-synthesized tungstates that are directly introduced into the system. They preferentially melt in the neck region of WO3 or form a liquid phase through a solid-state reaction, promoting mass transfer and densification between WO3 particles. Simultaneously, they can construct WO3 heterojunction interfaces in situ. The components include: bismuth tungstate (Bi2WO6), zinc tungstate (ZnWO4), copper tungstate (CuWO4), calcium tungstate (CaWO4), strontium tungstate (SrWO4), barium tungstate (BaWO4), silver tungstate (Ag2WO4), manganese tungstate (MnWO4), iron tungstate (FeWO4), cobalt tungstate (CoWO4), nickel tungstate (NiWO4), indium tungstate (In2(WO4)3), cerium tungstate (Ce2(WO4)3), lanthanum tungstate (La2(WO4)3), bismuth distungstate (Bi2W2O9), and bismuth niobium tungstate (Bi4NbWO4). 11 ); (f) Precursor compounds The water-insoluble oxalates, carbonates, or hydroxides corresponding to the components in (a) to (e) above decompose in situ during degumming or sintering heat treatment to generate corresponding oxides or oxygen-containing compounds; the precursor compounds are uniformly dispersed in the WO3 powder as solid particles in the slurry stage, and decompose in situ during heat treatment to generate nano-sized active powders, with better dispersion uniformity than directly added oxides; "insoluble in water" means: solubility in deionized water at 25°C ≤0.1 g / 100 mL; typical precursor compounds include: calcium carbonate (CaCO3), magnesium carbonate (MgCO3), iron oxalate (FeC2O4), etc. The amount of the sintering aid added is 0.1-30 wt.% of the tungsten trioxide powder mass; the amount of the precursor compound added is based on the theoretical mass of the corresponding photocatalytically active oxide generated by its complete thermal decomposition, i.e., oxide equivalent. The defect control agent (including grain growth inhibitors, valence state compensators, grain boundary modifiers, and oxygen activity self-regulating stabilizers) is selected from at least one of the following components: (a) Equivalent substitution stabilizers Such defect control agents and W 6+ With or near-identical valence, WO3 lattice is stabilized through solid solution substitution mechanism, suppressing W 6+ →W 5+ Excessive reduction includes the following components: molybdenum trioxide (MoO3), rhenium heptaoxide (Re2O7), chromium trioxide (CrO3), tellurium trioxide (TeO3), and antimony pentoxide (Sb2O5); (b) Grain boundary segregation inhibitors The ionic radius of such defect control agents is much larger than W. 6+ (r(W) 6+The WO3 grain size is 0.060 nm, mainly due to grain boundary segregation. It inhibits abnormal WO3 grain growth through solute dragging effect, while simultaneously accumulating at grain boundaries to form a pinning phase, including the following components: lanthanum trioxide (La2O3), yttrium oxide (Y2O3), scandium oxide (Sc2O3), gadolinium oxide (Gd2O3), cerium dioxide (CeO2), samarium oxide (Sm2O3), neodymium oxide (Nd2O3), and praseodymium oxide (Pr6O3). 11 Or Pr2O3), europium oxide (Eu2O3), terbium oxide (Tb4O7 or Tb2O3), dysprosium oxide (Dy2O3), holmium oxide (Ho2O3), erbium oxide (Er2O3), thulium oxide (Tm2O3), ytterbium oxide (Yb2O3), lutetium oxide (Lu2O3), indium oxide (In2O3); (c) Grain boundary / lattice dual stabilizer The ionic radius of such defect control agents is related to W 6+ With moderate phase difference, it has limited solid solubility in the WO3 lattice and forms a nanoscale segregation layer at the grain boundaries. Through solid solution strengthening and grain boundary pinning, it inhibits grain growth and defect formation. It includes the following components: zirconium dioxide (ZrO2), hafnium dioxide (HfO2), tin dioxide (SnO2), germanium dioxide (GeO2), aluminum oxide (Al2O3), and gallium oxide (Ga2O3). (d) Oxygen activity self-regulating stabilizer These defect control agents are compounds with reversible redox pairs. During sintering, they maintain a localized oxidizing atmosphere around WO3 particles through a dynamic oxygen release / storage mechanism, thus thermodynamically inhibiting W oxidation. 6+ →W 5+ The reduction reaction involves the following components: cerium dioxide (CeO2), manganese oxide (MnO2 / Mn2O3 / Mn3O4 system), and cobalt oxide (Co3O4 / CoO system). (e) Precursor compounds The water-insoluble oxalates and / or carbonates corresponding to components (a), (b), (c), and (d) above decompose in situ during sintering heat treatment to generate corresponding oxides; for example, lanthanum oxalate (La2(C2O4)3), yttrium oxalate (Y2(C2O4)3), neodymium oxalate (Nd2(C2O4)3), zirconium carbonate (ZrOCO3), etc.; wherein, "insoluble in water" means: solubility in deionized water at 25℃ ≤ 0.1 g / 100 mL; The amount of the defect control agent added is 0.1-30 wt.% of the tungsten trioxide powder mass; the amount of the precursor compound added is based on the theoretical mass of the corresponding photocatalytically active oxide generated by its complete thermal decomposition, i.e., oxide equivalent. The organic additives include at least one of binders, plasticizers, dispersants, surfactants, rheology modifiers, and defoamers; The organic additives are used alone or in combination, with a total addition amount of 0.1-30 wt.% of the total mass of tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents. The adhesive is selected from at least one of the following components: polyethylene oxide (PEO), sodium alginate (SA), chitosan (CTS), polyurethane emulsion (PU), polyacrylamide (PAM), polyvinyl alcohol (PVA), methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), ethylcellulose (EC), polyethylene glycol (PEG, molecular weight 200-20,000), polyacrylic acid (PAA), polyvinyl acetate (PVAc), starch (ST) and its derivatives; The plasticizer is selected from at least one of the following components: triethyl acetylglucosamine citrate (ATEC), epoxidized soybean oil (ESO), polycaprolactone (PCL), glycerin (GLY), dibutyl phthalate (DBP), triethyl citrate (TEC), polyethylene glycol (PEG), sorbitol (SORB), and dioctyl sebacate (DOS). The dispersant is selected from at least one of the following components: polycarboxylate superdispersants (such as Solsperse). TM 32000, Tamol TM SN), polymaleic anhydride (PMA), polyaspartic acid (PASP), ammonium polyacrylate (NH4PAA), sodium polyacrylate (NaPAA), tetramethylammonium hydroxide (TMAH), ammonium citrate (AC), gum arabic (GA) and polyvinylpyrrolidone (PVP). The surfactant is selected from at least one of the following components: sorbitan monooleate (Span-80), cocamidopropyl betaine (CAB), perfluoropolyethers (such as Zonyl® FSO), sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide (CTAB), polysorbate 80 (Tween-80), octylphenyl polyoxyethylene ether (Triton X-100), lecithin (LC), and fluorocarbon surfactants (such as Capstone® FS-30); The rheology modifier is selected from at least one of the following components: guar gum (GG), gellan gum (GeG), polyacrylic acid thickeners (such as Carbopol® 940), organic modified montmorillonite (such as Bentonex®), xanthan gum (XG), sodium carboxymethyl cellulose (CMC), bentonite (BT), fumed silica (FS), and polyacrylamide (PAM). The defoamer is selected from at least one of the following components: polydimethylsiloxane (PDMS), polyether defoamer (such as Pluronic® L61), isooctanol (IOA), n-octanol (NOA), silicone oil (such as Dow Corning® 200 Fluid), polyether modified siloxane (such as BYK-024), and mineral oil (MO). The pH adjuster is at least one of ammonia (NH3·H2O, 1-10 mol / L) and hydrochloric acid (HCl, 1-10 mol / L); The reinforcing phase is fibers and / or whiskers, selected from any one or more of the following: (1) Inorganic fibers: glass fiber, basalt fiber, silicon carbide fiber, alumina fiber, mullite fiber, quartz fiber, potassium titanate fiber, aluminum nitride fiber, etc. (2) Ceramic whiskers: silicon carbide whiskers, zinc oxide whiskers, calcium sulfate whiskers, silicon nitride whiskers, barium titanate whiskers, aluminum borate whiskers, magnesium borate whiskers, sodium titanate whiskers, potassium titanate whiskers, zirconium oxide whiskers, aluminum oxide whiskers, calcium carbonate whiskers, aluminum nitride, etc. (3) Natural mineral fibers: sepiolite fiber, attapulgite fiber, wollastonite fiber, palygorskite fiber, tremolite fiber, actinolite fiber, vermiculite fiber, pyrophyllite fiber, sillimanite fiber, glauconite fiber, tourmaline fiber, palygorskite fiber, etc. (4) Synthetic organic fibers: polyacrylonitrile fiber, polyvinyl alcohol fiber, aramid fiber, polyimide fiber, etc.; The reinforcing phase has an aspect ratio ≥ 10, a length of 2 μm-10 mm, and a diameter of 0.1-1000 μm.

[0011] The solid content of the tungsten trioxide-based composite slurry is 20-70 vol.%, and the pH is 2-14. The amounts of organic additives and reinforcing phases added (based on the total mass of tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents) are as follows: Adhesive 1-20 wt.%; Dispersant 0.1-5 wt.%; Plasticizer 0.1-10 wt.%; Surfactant 0.01-5 wt.%; Rheology modifier 0.1-10 wt.%; Defoamer 0.05-10 wt.%; pH adjuster 0.01-10 wt.%; Reinforcing phase: 0.01-30 wt.% (fibers) or 0.01-50 wt.% (whiskers).

[0012] In some embodiments, in step S1, the homogeneous solution is uniformly dispersed by mechanical stirring; the tungsten trioxide-based suspension slurry and the composite slurry are uniformly dispersed by mechanical stirring and / or ball milling. For uniform dispersion of the homogeneous solution, the mechanical stirring rate is 100-3000 rpm; the stirring time is 0.5-180 min; the stirring paddle is made of inert material, preferably polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container is 0.1-2 cm. When mechanically dispersing tungsten trioxide-based suspension slurry and tungsten trioxide-based composite slurry, the stirring speed range is 20-3000 rpm; the stirring time range is 15-1500 min; the stirring paddle material is inert; and the distance between the stirring paddle blade and the bottom of the slurry container ranges from 0.1-50 cm. When uniformly dispersing tungsten trioxide-based suspension slurry and tungsten trioxide-based composite slurry using ball milling, the ball milling jar used for ball milling is made of an inert material, preferably polytetrafluoroethylene; the ball-to-material mass ratio is 0.2-12; the ball milling time is 30-1500 min; the diameter of a single grinding ball is 0.2-12 mm, and the average diameter is 3-8 mm.

[0013] In some embodiments, in step S2, the organic foam is made of polyurethane (PU), melamine formaldehyde (MF), or polystyrene (PS), preferably polyurethane foam (PU); the pore density of the organic foam is in the range of 6-70 PPI, and its macroscopic shape is any one of the following: cylinder, cube, cuboid, sphere, ellipsoid, torus, prism, pyramid, polyhedron, honeycomb block, sheet, arc, arch, tubular, hollow spherical shell, or any combination and deformation thereof; The impregnation is carried out using normal pressure, negative pressure assisted, or alternating negative and normal pressure methods; the impregnation process is carried out at 25±20℃, the normal pressure impregnation time is 30-1800 seconds, and the number of negative and normal pressure alternating impregnations is 1-5 times per impregnation cycle; The negative pressure assistance involves completely immersing the organic foam in the tungsten trioxide-based composite slurry described in step S1, then evacuating the composite slurry to boiling point within 3 minutes, maintaining boiling for 0.5-10 minutes to ensure that all air in the system is expelled, and then restoring it to ambient pressure. The pressure of the extrusion desizing is controlled at 0.1-10 MPa, and the thickness of the organic foam after extrusion is compressed to 30-95% of the original thickness; The centrifugal desizing process is performed at a speed of 500-5000 rpm for a time of 10-900 seconds. The drying process employs a programmed temperature increase method, with a temperature range of 20~95℃ and relative humidity gradually decreasing from ≥70% to <10%, drying until the mass change rate is <20% / h. After each impregnation-desizing-drying-impregnation cycle, the mass gain rate of the composite slurry loaded in the organic foam is 20-600%. After 2-5 cycles, the cumulative loading of the composite slurry reaches 150-1000% of the original mass of the organic foam, forming a coating thickness of 0.1-3.0 mm, a slurry coating thickness variation coefficient of <30%, and a pore blockage rate of <40%.

[0014] In step S3, the natural air drying is carried out in a ventilated environment with a temperature of 5-45℃, a relative humidity of 30-90%, a ventilation rate of 0.1-10.0 m / s, and a natural air drying time of 2-24 hours. The heating program for the drying process is as follows: the temperature is increased from room temperature to 50-95℃ at a rate of 0.1-20℃ / min, and the temperature is maintained for 4-24 hours. The airflow rate in the oven is 0.01-10 m / s, and the drying endpoint is a mass change rate of <0.1% / h. The degumming heat treatment includes: The first stage involves raising the temperature at a rate of 1-10℃ / min to 150-250℃ and holding it for 1-360 min. In the second stage, the temperature is increased to 350-450℃ at a rate of 0.5-10℃ / min, and then held for 1-360 min. The third stage involves raising the temperature at a rate of 0.5-10℃ / min to 550-600℃ and holding it for 1-360 min. The degumming heat treatment process is carried out under vacuum or atmospheric conditions. The vacuum conditions are: no gas is introduced and the absolute pressure inside the furnace is maintained below 100 Pa. The atmospheric conditions are: at least one of helium, argon, nitrogen, ammonia, air or oxygen is introduced, the gas flow rate is 0-9000 mL / min, and the pressure inside the furnace is maintained at gauge pressure +50 ~ +9000 Pa.

[0015] In some embodiments, in step S4, the controlled sintering heat treatment temperature is 800-1200℃, the heating rate is 2-20℃ / min, and the holding time is 0.01-24 hours; The controlled sintering heat treatment is carried out under vacuum or atmospheric conditions. The vacuum conditions are: no gas is introduced and the absolute pressure inside the furnace is maintained below 10 Pa. The atmospheric conditions are: at least one of hydrogen, helium, argon, nitrogen, ammonia, air and oxygen is introduced, the gas flow rate is 0-9000 mL / min, and the pressure inside the furnace is maintained at gauge pressure +50~+9000 Pa. In this application, the upper limit of the controlled sintering heat treatment temperature is strictly controlled within 1200℃. This limitation aims to effectively avoid the significant volatilization loss of tungsten trioxide (WO3) above 1100℃, ensuring the stability of the stoichiometry of the photocatalytic active components. The specific sintering temperature range is preferably 700℃ to 1100℃. This range is selected by comprehensively considering the melting point characteristics of the sintering aids and the eutectic reaction temperature in the system, aiming to find the optimal balance between the matrix densification process and the suppression of volatile components. Furthermore, the various process parameters of the controlled sintering heat treatment (including heating rate, holding time, and atmosphere control) are synergistically regulated based on the sintering kinetics, thermal stability threshold, microstructural evolution of microstructures, and grain growth behavior of the tungsten trioxide-based photocatalytic foam ceramic, while also fully considering the thermal sensitivity of the active components. Through the above precise regulation, this process can synergistically achieve the following technical objectives: (1) Construct a high-strength and high-transparency three-dimensional mesh framework: promote the in-situ synergistic growth of tungsten trioxide and photocatalytic active components to form a continuous foam ceramic rib structure; precisely control the width of the neck connection area between particles within the range of 0.1-50 μm, and achieve the best balance between the macroscopic mechanical strength of the material and the mass transfer efficiency of micro-reactants on the premise of ensuring high connectivity of the three-dimensional channels. (2) Implementing multi-scale grain growth suppression and lattice stabilization: utilizing the dual mechanisms of equivalent substitution solid solution and grain boundary segregation of defect control agents: on the one hand, making Mo 6+ Equivalent replacement of W 6+ Lattice sites enhance the structural stability of the WO3 lattice; on the other hand, they promote the development of La³⁺. + Y³ + Zr 4+ Large-radius ions are enriched in the grain boundary region, effectively suppressing abnormal growth of WO3 grains and W through the solute drag effect. 6+ Excessive reduction is avoided to prevent the excessive accumulation of oxygen vacancies and the resulting increase in composite centers; the average grain size is finely controlled within the range of 0.1-10 μm, thereby maintaining a high specific surface area and porosity of the foam ceramic. (3) Enhance interface bonding and component uniformity: significantly enhance the interfacial chemical bonding strength between the reinforcing phase and the foam ceramic matrix, ensure that the sintering aid and photocatalytic active components are uniformly distributed at the atomic level inside the skeleton ribs, and form a stable chemical bond with the main structure, avoiding component peeling during service. (4) Maintain the integrity of highly interconnected porous structure: effectively protect the pore structure during the sintering densification process, ensure the structural integrity of the three-dimensional interconnected porous framework, and keep the pore structure connectivity rate stable at over 60%, providing a channel for the rapid diffusion of pollutant molecules; (5) Locking the metastable crystal phase to optimize photoresponse performance: Based on the visible light response characteristics of WO3 with a narrow bandgap, the excessive generation of the thermodynamically stable monoclinic phase (m-WO3) is suppressed by controlled sintering heat treatment, so as to achieve a high proportion of retention of the metastable γ-WO3 phase; by utilizing the unique tunnel structure characteristics of γ-WO3 and its special band matching with the matrix, the separation efficiency of photogenerated carriers and surface reactivity are maximized, thereby significantly improving the catalytic degradation efficiency of the material in the visible light region; During sintering, based on the chemical properties of the reinforcing phase, the interfacial bonding exhibits two forms: (1) For chemically inert reinforcing phases (such as glass fiber and basalt fiber), they do not undergo significant chemical reactions with the foam ceramic matrix, and the reinforcement is mainly achieved through surface microstructure anchoring and physical integration; (2) For active enhancement phases (such as silicon carbide whiskers, mullite whiskers, aluminum borate whiskers, and potassium titanate whiskers), they react in situ with the WO3 matrix or photocatalytic functional phase at high temperature to form a chemical bonding layer at the interface. The thickness is controlled within the range of 0.01-5 μm to ensure the interface bonding strength while avoiding thermal stress cracking. The crystal phase composition of the monolithic tungsten trioxide-based photocatalytic foam ceramic is determined by the sintering reaction of the raw material powder used in step S1, including the unreacted original phase and / or the new crystal phase generated in situ during the sintering process; when there are two or more photocatalytic functional phases with different crystal structures or chemical compositions in the ceramic, their phase interfaces can form a heterojunction structure, providing a channel for the efficient separation and migration of photogenerated electron-hole pairs; This application also provides a monolithic tungsten trioxide-based photocatalytic foam ceramic prepared by the above preparation method. The monolithic tungsten trioxide-based photocatalytic foam ceramic has a compressive strength ≥0.1 MPa, a porosity of 60-95%, a pore structure connectivity >60%, and a degradation rate of organic pollutants under ultraviolet-visible light greater than 90%.

[0016] This application also provides the application of the monolithic tungsten trioxide-based photocatalytic foam ceramic prepared by the above preparation method in i) the degradation of organic pollutants or water treatment; ii) the application in the preparation of devices for degrading organic pollutants or water treatment devices.

[0017] The organic pollutants mentioned include those listed in the Shanghai Key Controlled New Pollutants List (2023 Edition): perfluorooctyl sulfonic acid and its salts and perfluorooctyl sulfonyl fluoride (PFOS); perfluorooctanoic acid and its salts and related compounds (PFOA); decabromodiphenyl ether; short-chain chlorinated paraffins; hexachlorobutadiene; Pentachlorophenol and its salts and esters; trichlorfon; perfluorohexyl sulfonic acid and its salts and related compounds (PFHxS class); decanoate and its cis and trans isomers; dichloromethane; chloroform; nonylphenol; antibiotics (antibacterial drugs); obsolete new pollutants (such as methyl parathion, toxaphene, etc.); microplastics; bisphenol A.

[0018] This application provides a method for preparing a visible-light-responsive monolithic tungsten trioxide-based photocatalytic foam ceramic and its application in water treatment. The key technical points are: using tungsten trioxide powder as the main raw material, fully utilizing the inherent visible-light photocatalytic activity of WO3 (band gap 2.6-2.8 eV) and its strong oxidation valence band (+3.1 eV vs NHE); supplemented with appropriate defect control agents (MoO3, La2O3, ZrO2, etc.) to synergistically regulate grain growth and defect structure during sintering, and suppress W during high-temperature sintering. 6+ Excessive reduction, excessive oxygen vacancy generation, and abnormal growth of WO3 grains were addressed. High aspect ratio whiskers or fibers were introduced in situ as reinforcing phases in the preparation system. After controlled sintering, the reinforcing phase and the tungsten trioxide framework formed a three-dimensional interlocking network structure, strengthening the porous framework struts and significantly improving the material's compressive strength, ensuring structural reliability under complex water flow conditions. Simultaneously, the photocatalytic active component and tungsten trioxide formed a continuous and dense photocatalytic functional phase network through particle fusion and phase boundary bonding. This network itself constitutes the mechanical framework of the foam ceramic, completely avoiding the leaching risk of active components in traditional supported catalysts. Based on the electronic characteristics and molecular structure of the target pollutants, specific heterojunction systems were precisely matched and constructed, significantly improving the separation efficiency of photogenerated carriers and the interfacial reaction activity, achieving visible light-driven targeted and efficient degradation of emerging pollutants.

[0019] Compared with the prior art, the present invention has the following outstanding advantages: (1) Visible light-driven and structure-function integrated synergistic design to eliminate the bottlenecks of catalyst shedding and insufficient strength. Using tungsten trioxide as the main component, its visible light response advantage of 2.6-2.8 eV band gap (approximately 10 times higher than TiO2 photon utilization) is fully utilized. At the same time, its valence band position of +3.1 eV provides extremely strong oxidizing holes, which is conducive to the efficient generation of ·OH. By precisely controlling the grain size through defect control agents, high aspect ratio whiskers / fibers are introduced in situ to construct a three-dimensional interlocking network, which greatly improves the compressive strength of the foam ceramic. The photocatalytic active component and the tungsten trioxide framework form a photocatalytic functional phase network in situ through solid-phase diffusion and interfacial reaction. This network continuously forms three-dimensional framework ribs, effectively avoiding the risk of loss of active components due to physical adsorption.

[0020] (2) The precise matching mechanism between pollutants and heterojunctions breaks through the bottlenecks of degradation efficiency and specificity. Based on the molecular structure, electronic properties, and bond energy characteristics of the target pollutants, a WO3-based heterojunction system was systematically matched. WO3, as an S-type heterojunction of OP (coordinated with RP such as TiO2 and In2O3), retains the strong oxidizing hole of +3.1 eV in the WO3 valence band while utilizing the strong reducing conduction band of RP to generate a high overpotential ·O2. - This enables the simultaneous and efficient supply of dual active species, allowing for targeted degradation of specific pollutants.

[0021] (3) Significant advantages in engineering applicability and green application Foamed ceramics possess high structural strength, environmental stability, and easy cutting properties, allowing them to be directly packed into fixed-bed and fluidized-bed reactors without downstream separation processes. The visible light responsiveness of WO3 enables it to drive photocatalytic reactions under natural light conditions, providing a material basis for sunlight-driven outdoor water treatment applications. The three-dimensional interconnected channels enhance mass transfer efficiency while also improving light scattering. This design mitigates the risk of nanoparticle leakage at the source, effectively balancing the practical needs of water treatment engineering for material mechanical reliability, functional durability, and ease of operation. Attached Figure Description

[0022] Figure 1 This is a process flow diagram for the preparation of monolithic tungsten trioxide-based photocatalytic foam ceramics. Detailed Implementation

[0023] To make the technical solution of this application clearer and easier to understand, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0024] Unless otherwise specified, the experimental or testing methods described in the following examples are conventional methods; the reagents and materials described are of analytical grade and obtained from conventional commercial sources unless otherwise specified.

[0025] This application provides a method for preparing a visible light-responsive monolithic tungsten trioxide-based photocatalytic foam ceramic, comprising the following steps: Step S1: Preparation of tungsten trioxide-based composite slurry Organic additives and pH adjusters are added to deionized water and dispersed evenly to form a homogeneous solution; tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents are added to the homogeneous solution in batches and dispersed evenly to form a tungsten trioxide-based suspension slurry; fiber and / or whisker reinforcing phases are added to the suspension slurry and dispersed evenly to form a tungsten trioxide-based composite slurry; Step S2: Preparation of tungsten trioxide-based foam ceramic wet blank The organic foam is completely immersed in the tungsten trioxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and excess slurry on the surface is removed by squeezing or centrifugation; then drying treatment is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the tungsten trioxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a wet tungsten trioxide-based foam ceramic blank. Step S3: Preparation of tungsten trioxide-based foam ceramic green body The tungsten trioxide-based foam ceramic green body obtained in step S2 is first air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried green body is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while tungsten trioxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phases are initially sintered together to form a tungsten trioxide-based foam ceramic green body with a three-dimensional interconnected pore structure. Step S4: Sintering and Heterogeneous Structure Construction The green body obtained in step S3 is subjected to controlled sintering heat treatment. Under the action of sintering aids, tungsten trioxide and photocatalytic active components form a continuous and dense ceramic skeleton network through particle fusion and phase boundary bonding, effectively reducing the sintering temperature and ensuring the structural integrity of the three-dimensional interconnected channels. At the same time, the defect control agent inhibits W during high-temperature sintering through solid solution substitution and grain boundary segregation mechanisms. 6+ Excessive reduction, excessive generation of oxygen vacancies, lattice distortion, and abnormal growth of WO3 grains are controlled to keep the grain size within a small range, maintaining a high specific surface area and porosity of the material. During sintering, the reinforcing phase and the foam ceramic skeleton are firmly bonded together. The components construct band-matched heterojunction interfaces or generate new photocatalytically active phases in situ through solid-phase diffusion and interfacial reactions. The electronic structure of the heterojunction interface or the new photocatalytically active phase is precisely matched with the molecular characteristics of the target pollutant, significantly improving the separation efficiency of photogenerated carriers and the interfacial reaction activity. Finally, a visible light-responsive monolithic tungsten trioxide-based photocatalytic foam ceramic is obtained. The three-dimensional skeleton of this ceramic is composed of a continuous network of photocatalytic functional phases, which has excellent mechanical strength, high photocatalytic activity, and specific and efficient degradation ability for the target pollutant.

[0026] The following description, in conjunction with specific embodiments, illustrates this point.

[0027] Example 1 S1: Organic additives and pH adjusters are added to deionized water and dispersed evenly to form a homogeneous solution; tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents are added to the homogeneous solution in batches and dispersed evenly to form a tungsten trioxide-based suspension slurry; fiber and / or whisker reinforcing phases are added to the suspension slurry and dispersed evenly to form a tungsten trioxide-based composite slurry; S2: The organic foam is completely immersed in the tungsten trioxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and excess slurry on the surface is removed by squeezing or centrifugation; then drying treatment is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the tungsten trioxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a wet tungsten trioxide-based foam ceramic blank. S3: The tungsten trioxide-based foam ceramic green body obtained in step S2 is first air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried green body is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while tungsten trioxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phases are initially sintered together to form a tungsten trioxide-based foam ceramic green body with a three-dimensional interconnected pore structure; S4: The green body obtained in step S3 is subjected to controlled sintering heat treatment. Under the action of sintering aids, tungsten trioxide and photocatalytic active components form a continuous and dense ceramic skeleton network through particle fusion and phase boundary bonding, effectively reducing the sintering temperature and ensuring the structural integrity of the three-dimensional interconnected channels. At the same time, the defect control agent inhibits W during high-temperature sintering through solid solution substitution and grain boundary segregation mechanisms. 6+ Excessive reduction, excessive generation of oxygen vacancies, lattice distortion, and abnormal growth of WO3 grains are controlled to keep the grain size within a small range, maintaining a high specific surface area and porosity of the material. During sintering, the reinforcing phase and the foam ceramic skeleton are firmly bonded together. The components construct band-matched heterojunction interfaces or generate new photocatalytically active phases in situ through solid-phase diffusion and interfacial reactions. The electronic structure of the heterojunction interface or the new photocatalytically active phase is precisely matched with the molecular characteristics of the target pollutant, significantly improving the separation efficiency of photogenerated carriers and the interfacial reaction activity. Finally, a visible light-responsive monolithic tungsten trioxide-based photocatalytic foam ceramic is obtained. The three-dimensional skeleton of this ceramic is composed of a continuous network of photocatalytic functional phases, which has excellent mechanical strength, high photocatalytic activity, and specific and efficient degradation ability for the target pollutant.

[0028] In step S1, the tungsten trioxide powder has a purity > 98 wt.% and an average particle size D50 of 5 μm; The photocatalytic active component is titanium dioxide (TiO2) with a purity >98 wt.% and an average particle size D50 of 0.5 μm, and the addition amount is 50 wt.% of the tungsten trioxide powder mass. The sintering aid is molybdenum trioxide (MoO3) with a purity >98 wt.% and an average particle size D50 of 5 μm, and is added at a rate of 5 wt.% of the tungsten trioxide powder mass. The defect control agent is lanthanum trioxide (La₂O₃) with a purity >98 wt.% and an average particle size D50 of 3 μm, and is added at a rate of 3 wt.% of the tungsten trioxide powder mass. The organic additives include binders, plasticizers, dispersants, surfactants, rheology modifiers, and defoamers; wherein the binder is sodium alginate (SA); the plasticizer is glycerin (GLY); the dispersant is polycarboxylate superdispersant (Solsperse™ 32000); the surfactant is sodium dodecyl sulfate (SDS); the rheology modifier is xanthan gum (XG); and the defoamer is polydimethylsiloxane (PDMS). The pH adjuster is ammonia water (NH3·H2O, 2 mol / L); The reinforcing phase is zinc oxide (ZnO) whiskers with an average length of 55 μm and an average diameter of 1.5 μm; The solid content of the tungsten trioxide-based composite slurry is 55 vol.%, and the pH is 10. The amount of each component of the organic additive and the reinforcing phase added is based on the total mass of tungsten trioxide powder, photocatalytic active component, sintering aid and defect control agent, as follows: binder, 0.9 wt.%; dispersant, 1.5 wt.%; plasticizer, 1.2 wt.%; surfactant, 2.0 wt.%; rheology modifier, 2.1 wt.%; defoamer, 0.7 wt.%; reinforcing phase, 12 wt.%.

[0029] In step S1, the homogeneous solution is uniformly dispersed by mechanical stirring; the tungsten trioxide-based suspension slurry and the composite slurry are also uniformly dispersed by mechanical stirring. For the uniform dispersion of the homogeneous solution, the mechanical stirring rate was 1000 rpm; the stirring time was 15 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. The stirring rate for both the tungsten trioxide-based suspension slurry and the composite slurry was 2000 rpm; the stirring time was 120 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. In step S2, the organic foam is made of polyurethane (PU), has a pore density of 10 PPI, and has a macroscopic shape of cuboid. The impregnation is carried out under normal pressure; the impregnation process is conducted at 20°C for 300 seconds. The pressure of the extrusion desizing is controlled within 1 MPa, and the thickness of the organic foam after extrusion is compressed to 90% of the original thickness; The drying process employs a programmed temperature increase method, with a drying temperature of 70℃, and continues until the mass change rate is <1% / h. After five cycles of impregnation-desizing-drying-impregnation, the cumulative loading of the composite slurry reaches 590% of the original mass of the organic foam. In step S3, the natural air drying is carried out in a ventilated environment at a temperature of 34°C, a relative humidity of 20%, a ventilation rate of 1 m / s, and a natural air drying time of 12 hours. The heating program for the drying process is as follows: the temperature is increased from room temperature to 70°C at a rate of 2°C / min, and the temperature is maintained for 10 hours. The airflow rate inside the oven is 1 m / s, and the drying endpoint is a mass change rate of <0.05% / h. The degumming heat treatment includes: In the first stage, the temperature is increased to 250℃ at a rate of 8℃ / min and held for 30 min. The second stage involves raising the temperature to 450℃ at a rate of 4℃ / min and holding it for 10 minutes. The third stage involves increasing the temperature to 600℃ at a rate of 2℃ / min and holding it for 5 minutes. The degumming heat treatment process is carried out under a selected atmosphere, namely air, with a gas flow rate of 1000 mL / min and the furnace pressure maintained at gauge pressure +600 Pa. In step S4, the process conditions for the controlled sintering heat treatment include: sintering temperature 980℃, isothermal time 2min, and heating rate 5℃ / min. During the controlled sintering heat treatment, the components undergo the following chemical reactions in sequence, ultimately constructing a cascaded heterojunction system with targeted degradation function: (1) Liquid-phase activation and particle densification reaction of sintering aids The sintering aid, molybdenum trioxide (MoO3), has a melting point of approximately 795°C, far lower than the sintering temperature (980°C) of this embodiment. Upon heating to 795°C, it transforms into a liquid state, providing a continuous and stable activating liquid phase for the system. The eutectic temperature of the WO3-MoO3 binary system is approximately 760°C, forming a low-viscosity melt that wets and spreads at the interface between WO3 and TiO2 particles. Through capillary action, it drives particle rearrangement, effectively filling the interparticle gaps and significantly accelerating mass transfer and densification. This precisely controls the width of the neck connection region between particles to within 10 μm, ensuring that the three-dimensional skeleton ribs form a continuous and dense ceramic network structure at low temperatures (<1000°C), avoiding the risk of high-temperature volatilization of WO3 above 1100°C. Its activation process can be described as follows: MoO3(s) → MoO3(l) [795°C] MoO3(l) + WO3(s) → WO3-MoO3 eutectic liquid phase [760°C] It is worth noting that Mo6+ Ionic radius (r = 0.059 nm) and W 6+ (r = 0.060 nm) almost identical, and with the same valence state, during the sintering cooling process, some Mo 6+ It enters the WO3 lattice through an equivalent substitution mechanism, forming a (W,Mo)O3 solid solution, which stabilizes the WO3 lattice structure and synergistically inhibits W. 6+ Excessive reduction allows sintering aids to achieve a synergistic effect in promoting liquid-phase densification and lattice stability.

[0030] (2) Grain boundary segregation and pinning reaction of defect control agents The defect control agent lanthanum trioxide (La2O3) contains La 3+ The ionic radius is 0.103 nm, much larger than W. 6+ (0.060 nm), and with a valence state difference of 3, it cannot enter the WO3 lattice through solid solution substitution. Therefore, La 3+ Primarily driven by grain boundary segregation, the WO3 grains preferentially accumulate in the grain boundary region during high-temperature sintering. This effectively suppresses abnormal WO3 grain growth through the solute drag effect, reducing the average grain size D. 50 The diameter is controlled within 5 μm to maintain a high specific surface area and porosity of the foam ceramic.

[0031] Meanwhile, La enriched at the grain boundaries 3+ Under sintering conditions at 980℃, a solid-phase interfacial reaction occurs with local WO3, resulting in the in-situ formation of lanthanum tungstate nanoscale pinned phases. La2O3 + 3WO3 → La2(WO4)3 The generated La2(WO4)3 phase is enriched at the WO3 grain boundaries, acting as a grain-boundary-pinning phase. This further restricts grain boundary migration through the Zener pinning mechanism, and, in conjunction with the solute dragging effect, inhibits the abnormal growth of WO3 grains and W... 6+ To W 5+ Excessive reduction effectively prevents the increase of recombination centers and the decrease of photocatalytic activity caused by excessive accumulation of oxygen vacancies.

[0032] (3) Enhanced in-situ interfacial reaction between the phase and the matrix The zinc oxide (ZnO) whiskers used as the reinforcing phase are active reinforcing phases, exhibiting significantly higher chemical activity than inert reinforcing phases such as glass fibers. During sintering at 980℃, solid-phase diffusion and in-situ interfacial reactions occur at the interface between the ZnO whiskers and the WO3 matrix, forming a zinc tungstate (ZnWO4) bonded layer. ZnO + WO3 → ZnWO4 The generated ZnWO4 phase (ferrotungsten structure) forms a continuous chemically bonded interface layer with a thickness of about 10-50 nm at the interface between ZnO whiskers and WO3 matrix. Since ZnO and WO3 are chemically compatible, the interface bonding is mainly chemical bonding, which has a significantly better reinforcing effect than the physically anchored inert reinforcing phase. It can effectively transfer the crack propagation stress borne by the foam ceramic and significantly improve the compressive strength of the material.

[0033] Most importantly, the generated ZnWO4 phase has a band gap of approximately 3.7-4.0 eV (UV response) and possesses photocatalytic activity. It can further form a ZnWO4 / WO3 heterojunction secondary structure with the WO3 matrix at the interface, participating in the separation and transport of photogenerated carriers. This achieves a synergistic contribution to enhancing the relative photocatalytic function while simultaneously strengthening the mechanical properties.

[0034] (4) In-situ formation reaction of photocatalytically active new phase During the high-temperature sintering process at 980℃, the photocatalytically active components TiO2 and WO3 undergo solid-phase diffusion and in-situ reaction to generate a new photocatalytically active phase of titanoltate. TiO2 + WO3 → TiWO5 2TiO2 + WO3 → Ti2WO7 TiWO5 is the main product, with a band gap of approximately 2.5-2.9 eV, falling between TiO2 (3.0-3.2 eV) and WO3 (2.6-2.8 eV), effectively extending the photoresponse range into the visible light region (<500 nm). The conduction and valence bands of TiWO5 lie between those of TiO2 and WO3, forming a band gradient bridging structure, laying the band structure foundation for the subsequent construction of S-type cascaded heterojunctions. Furthermore, the in-situ formation of a small amount of Ti2WO7 further enriches the interface phase composition, contributing to the broadening of the photoresponse range.

[0035] (5) Heterogeneous structure construction and tetracycline-targeted degradation mechanism The TiWO5 generated in situ during the controlled sintering heat treatment process, together with the residual TiO2 and WO3 phases, jointly construct a TiO2 / TiWO5 / WO3 cascaded S-type heterojunction: (1) TiO2 is used as a reduced photocatalyst (RP), with a conduction band position of approximately -0.5 eV (vs NHE). (2) WO3, as an oxidative photocatalyst (OP), has a valence band position of approximately +3.1 eV (vs NHE). (3) The TiWO5 conduction band and valence band are located between the two, serving as an intermediate phase for band gradient bridging, enabling the stepwise directional transport of charge carriers.

[0036] Under visible light irradiation, the built-in electric field at the TiO2 / TiWO5 and TiWO5 / WO3 interfaces drives the weak reducing electrons in the WO3 conduction band and the weak oxidizing holes in the TiO2 valence band to recombine and annihilate in a directional manner at the interface, while retaining the strong reducing electrons in the TiO2 conduction band. The presence of strong oxidizing holes (+3.1 eV) in the valence band of WO3 (0.5 eV) and O2 respectively generates ·O2. - Superoxide radicals and ·OH hydroxyl radicals enable the simultaneous and efficient supply of dual active species.

[0037] The above system targets the pollutant tetracycline (TC, C). 22 H 24 The targeted degradation of N2O8 is based on the precise matching of the bond energy characteristics of the TC molecule with its dual active species. The TC molecule is composed of four parallel rings (A, B, C, and D). The bond energies and breaking difficulties of each key chemical bond are as follows: C4 position dimethylamino C The N-bond has a bond energy of approximately 305 kJ / mol, making it the lowest bond energy site in the entire molecule. It is most easily oxidized and broken, making it a priority target for targeted attack. The enol hydroxyl group at C11a... OH bond (approximately 360 kJ / mol) and C2 amide bond N-bond (approximately 350 kJ / mol) is next; C4a The C12a enol double bond (approximately 610 kJ / mol) and the D-ring aromatic conjugated C=C bond (approximately 510 kJ / mol) have the highest bond energies, requiring synergy between two active species to achieve ring-opening mineralization. Therefore, the system performs targeted degradation of tetracycline in three steps: (1) Target-induced (C4) N-bond preferential breakage): ·OH, due to its high electrophilicity, preferentially attacks the C4 position of the TC molecule. The N-bond (305 kJ / mol) initiates the removal of dimethylamino and the formation of the benzene ring-opening precursor; (2) Hydroxylation of active site (C11a-position oxygenation activation): ·OH attacks the C11a-position enol hydroxyl group (C OH (360 kJ / mol) to achieve oxygenation activation at the C11a position, further weakening the conjugation stability of the TC molecule's tetracyclic system; (3) Ring opening and complete mineralization of the tetracyclic parent nucleus: ·OH and ·O2 - Coordinated and sustained C4a attack The C12a enol double bond and D-ring aromatic conjugation system overcomes the aromatic ring conjugation stabilization energy (approximately 510 kJ / mol), driving the sequential ring opening of the tetracyclic core, ultimately completely mineralizing TC into CO2, H2O, and NH4. + NO3 - Inorganic small molecules, etc.

[0038] The specificity of this targeted matching stems from the precise division of labor among the two active species: • The high electrophilicity of OH is highly compatible with the low bond energy (305 kJ / mol) of the C4-N bond and the high electron cloud density of the C11a site in the TC molecule, enabling preferential initiation; • O2 - The nucleophilicity of the compound is precisely matched with the unsaturated characteristics of the C4a-C12a enol double bond, achieving synergistic ring opening; the S-type heterojunction mechanism ensures the simultaneous retention of the high redox potential of the two active species, thus ensuring the continuous attack capability on the high bond energy aromatic ring system, thereby achieving efficient degradation of tetracycline from targeted initiation, active site activation to complete mineralization.

[0039] The monolithic tungsten trioxide-based photocatalytic foam ceramic has a cuboid shape; compressive strength ≥ 0.6 MPa, porosity ≥ 84%, pore structure connectivity ≥ 80%, and tetracycline degradation rate ≥ 95% under visible light. Those skilled in the art can determine the process window that satisfies the above effects through limited experiments under conventional equipment conditions, based on the specific type of tungsten trioxide powder, the type of photocatalytic active component, and the characteristics of the reinforcing phase.

[0040] Example 2 S1: Organic additives and pH adjusters are added to deionized water and dispersed evenly to form a homogeneous solution; tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents are added to the homogeneous solution in batches and dispersed evenly to form a tungsten trioxide-based suspension slurry; fiber and / or whisker reinforcing phases are added to the suspension slurry and dispersed evenly to form a tungsten trioxide-based composite slurry; S2: The organic foam is completely immersed in the tungsten trioxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and excess slurry on the surface is removed by squeezing or centrifugation; then drying treatment is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the tungsten trioxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a wet tungsten trioxide-based foam ceramic blank. S3: The tungsten trioxide-based foam ceramic green body obtained in step S2 is first air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried green body is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while tungsten trioxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phases are initially sintered together to form a tungsten trioxide-based foam ceramic green body with a three-dimensional interconnected pore structure; S4: The green body obtained in step S3 is subjected to controlled sintering heat treatment. Under the action of sintering aids, tungsten trioxide and photocatalytic active components form a continuous and dense ceramic skeleton network through particle fusion and phase boundary bonding, effectively reducing the sintering temperature and ensuring the structural integrity of the three-dimensional interconnected channels. At the same time, the defect control agent inhibits W during high-temperature sintering through solid solution substitution and grain boundary segregation mechanisms. 6+ Excessive reduction, excessive generation of oxygen vacancies, lattice distortion, and abnormal growth of WO3 grains are controlled to keep the grain size within a small range, maintaining a high specific surface area and porosity of the material. During sintering, the reinforcing phase and the foam ceramic skeleton are firmly bonded together. The components construct band-matched heterojunction interfaces or generate new photocatalytically active phases in situ through solid-phase diffusion and interfacial reactions. The electronic structure of the heterojunction interface or the new photocatalytically active phase is precisely matched with the molecular characteristics of the target pollutant, significantly improving the separation efficiency of photogenerated carriers and the interfacial reaction activity. Finally, a visible light-responsive monolithic tungsten trioxide-based photocatalytic foam ceramic is obtained. The three-dimensional skeleton of this ceramic is composed of a continuous network of photocatalytic functional phases, which has excellent mechanical strength, high photocatalytic activity, and specific and efficient degradation ability for the target pollutant.

[0041] In step S1, the tungsten trioxide powder has a purity > 98 wt.% and an average particle size D50 of 5 μm; The photocatalytic active component is bismuth trioxide (Bi₂O₃) with a purity >98 wt.%, an average particle size D50 of 2.5 μm, and an addition amount of 45 wt.% of the tungsten trioxide powder mass. The sintering aid is zinc oxide (ZnO) with a purity >98 wt.% and an average particle size D50 of 2 μm, and is added at a rate of 7 wt.% of the tungsten trioxide powder mass. The defect control agent is molybdenum trioxide (MoO3) with a purity >98 wt.% and an average particle size D50 of 5 μm, and is added at a rate of 6 wt.% of the tungsten trioxide powder mass. The organic additives include binders, plasticizers, dispersants, surfactants, rheology modifiers, and defoamers; wherein the binder is chitosan (CTS); the plasticizer is epoxidized soybean oil (ESO); the dispersant is ammonium polyacrylate (NH4PAA); the surfactant is cetyltrimethylammonium bromide (CTAB); the rheology modifier is sodium carboxymethyl cellulose (CMC); and the defoamer is isooctanol (IOA). The pH adjuster is ammonia water (NH3·H2O, 2 mol / L); The reinforcing phase is mullite whiskers with an average length of 12 μm and an average diameter of 0.6 μm; The solid content of the tungsten trioxide-based composite slurry is 53 vol.%, and the pH is 11. The addition amounts of each component of the organic additive and the reinforcing phase are based on the total mass of tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents, specifically as follows: binder, 1.4 wt.%; dispersant, 0.6 wt.%; plasticizer, 2.1 wt.%; surfactant, 1.2 wt.%; rheology modifier, 1.5 wt.%; defoamer, 2.1 wt.%; reinforcing phase, 15 wt.%. In step S1, the homogeneous solution is uniformly dispersed by mechanical stirring; the tungsten trioxide-based suspension slurry and the composite slurry are also uniformly dispersed by mechanical stirring. For the uniform dispersion of the homogeneous solution, the mechanical stirring speed was 900 rpm; the stirring time was 10 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. The stirring rate for both the tungsten trioxide-based suspension slurry and the composite slurry was 2100 rpm; the stirring time was 120 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. In step S2, the organic foam is made of polyurethane (PU), has a pore density of 10 PPI, and has a cubic shape. The impregnation is carried out under normal pressure; the impregnation process is carried out at 25°C for 180 seconds. The pressure of the extrusion desizing is controlled within 0.9 MPa, and the thickness of the organic foam after extrusion is compressed to 90% of the original thickness; The drying process employs a programmed temperature increase method, with a drying temperature of 70℃, and continues until the mass change rate is <1% / h. After four cycles of impregnation-desizing-drying-impregnation, the cumulative loading of the composite slurry reaches 490% of the original mass of the organic foam. In step S3, the natural air drying is carried out in a ventilated environment at a temperature of 25°C, a relative humidity of 10%, a ventilation rate of 1 m / s, and a natural air drying time of 12 hours. The heating program for the drying process is as follows: the temperature is increased from room temperature to 75°C at a rate of 2°C / min, and the temperature is maintained for 11 hours. The airflow rate inside the oven is 1 m / s, and the drying endpoint is a mass change rate of <0.05% / h. The degumming heat treatment includes: In the first stage, the temperature was increased to 250℃ at a rate of 10℃ / min and held for 40 min. The second stage involves raising the temperature to 450℃ at a rate of 5℃ / min and holding it for 10 minutes. The third stage involves raising the temperature to 600℃ at a rate of 3℃ / min and holding it for 1 min. The degumming heat treatment process is carried out under a selected atmosphere, namely air, with a gas flow rate of 1000 mL / min and the furnace pressure maintained at gauge pressure +800 Pa. In step S4, the process conditions for the controlled sintering heat treatment include: sintering temperature 950℃, isothermal time 1min, and heating rate 8℃ / min. During the controlled sintering heat treatment, the components undergo the following chemical reactions in sequence, ultimately constructing a cascaded heterojunction system with targeted degradation function: (1) Activation of eutectic liquid phase and densification reaction of sintering aid The sintering aid zinc oxide (ZnO) has a melting point of approximately 1975°C, which, when used alone, far exceeds the sintering temperature (950°C) of this embodiment, making it impossible to generate a liquid phase. However, the WO3-ZnO binary system exhibits a eutectic reaction at approximately 875°C, forming a Zn-rich activated liquid phase on the surface of the WO3 particles. Its eutectic temperature is significantly lower than the individual melting points of the two components. After heating to 875°C, the system enters the liquid-phase assisted sintering stage; during the 950°C holding stage, the liquid phase viscosity further decreases, wettability increases, driving the rearrangement and densification of WO3 and Bi2O3 particles. The width of the neck connection region between particles is precisely controlled within 10 μm, effectively promoting the formation of a continuous skeletal network structure in the foam ceramic. Furthermore, under the synergistic wetting of the Bi2O3 liquid phase (melting point approximately 824°C, completely liquefied at 950°C), ZnO also undergoes an interfacial solid-phase reaction with WO3 and molten Bi2O3, generating zinc tungstate (ZnWO4) and trace amounts of zinc bismuth oxide phase. ZnO + WO3 → ZnWO4 [875-950°C, ZnO-WO3 eutectic liquid phase assisted] ZnO + Bi₂O₃ → ZnBi₂O₄ [Local trace amounts, 950°C] The generated ZnWO4 (ferrotungsten structure) is preferentially enriched in the neck region between WO3 particles, which plays a role in filling the neck gaps and strengthening the chemical bonding between grains. At the same time, the band gap of ZnWO4 is about 3.8-4.0 eV, and it has photocatalytic activity (ultraviolet region). It can participate in the capture and transport of photogenerated carriers in the skeleton strips, realizing the superposition of the functions of sintering aid in densification promotion and photocatalytic synergistic gain.

[0042] (2) Solid solution substitution and grain boundary segregation reaction of defect control agents The defect control agent, molybdenum trioxide (MoO3), has a melting point of approximately 795°C and exists in liquid form at the sintering temperature (950°C) of this embodiment. Its wetting and diffusion between WO3 particles are extremely rapid. 6+ Ionic radius (r = 0.059 nm) and W 6+(r = 0.060 nm) almost identical, with the same charge, satisfying the size-valence matching condition of the Hume-Rothery solid solution rule, it can be massively dissolved into the WO3 lattice through an equivalent substitution mechanism to form a continuous (W,Mo)O3 solid solution: Mo 6+ Replace W 6+ Lattice site → (W1) x Mo x O3 solid solution (x ≤ 0.3) Mo 6+ Solid solution substitution effectively enhances the lattice barrier of WO3, simultaneously suppressing W3 during high-temperature sintering from both thermodynamic and kinetic perspectives. 6+ →W 5+ Excessive reduction reaction to prevent lattice distortion and color centers (tungsten bronze WO3) x The generation of ) maintains photocatalytic activity from the source. Meanwhile, supersaturated Mo 6+ Enrichment of WO3 in the grain boundary region via grain boundary segregation mechanism, forming nanoscale MoO at the grain boundaries. x The segregation layer, through the solute drag effect, suppresses the abnormal growth of WO3 grains, reducing the average grain size D. 50 The synergistic control is within 5 μm, maintaining a high specific surface area and photocatalytic active site density of the foam ceramic skeleton.

[0043] (3) Enhanced in-situ interfacial reaction between the phase and the matrix The mullite (3Al2O3·2SiO2) whiskers, the reinforcing phase, are partially active reinforcing phases: their main framework is chemically stable at 950℃ and does not undergo bulk decomposition; however, in a high-temperature environment of 950℃, the completely melted Bi2O3 liquid phase (melting point 824℃) has good wettability on the surface of the mullite whiskers. Through a liquid-phase assisted interfacial diffusion mechanism, Bi2O3 reacts with the trace Al2O3 precipitated on the whisker surface (a very small amount of surface Al from mullite decomposition), resulting in a local solid-liquid interfacial reaction. This reaction generates a continuous bismuth aluminate bonded layer in situ at the interface between the mullite and the WO3 / Bi2O3 matrix. Al₂O₃ + Bi₂O₃(l) → 2BiAlO₃ The generated BiAlO3 (perovskite-type bismuth aluminate) forms a continuous chemically bonded interfacial layer with a thickness of about 5–20 nm at the interface between the mullite whiskers and the ceramic matrix. This upgrades the bonding mode between the whiskers and the matrix from purely physical anchoring to chemical bonding, significantly improving the interfacial shear strength, ensuring effective stress transfer, and contributing to the strengthening and toughening of the foam ceramic skeleton. At the same time, the formation of the BiAlO3 phase firmly locks the whiskers and the matrix in the three-dimensional skeleton, completely avoiding the risk of the reinforcing phase falling off under water treatment conditions.

[0044] (4) In-situ formation reaction of photocatalytically active new phase The photocatalytically active component, bismuth trioxide (Bi2O3), has a melting point of approximately 824°C. Upon heating to 824°C, it transforms into a liquid state, extensively wetting and spreading on the surface of WO3 particles. This liquid-solid interface diffusion significantly accelerates the solid-phase reaction process between the two. At a sintering temperature of 950°C, WO3 and Bi2O3(l) undergo the following in-situ solid-liquid interface reaction, generating a new photocatalytically active phase of bismuth tungstate: WO3 + Bi2O3(l) → Bi2WO6 [Main Product] 2WO3 + Bi2O3(l) → Bi2W2O9 [Secondary product, high WO3 region] Bi₂WO₆ is the main product, which has an Aurivillius layered perovskite structure ([Bi₂O₂)). 2+ Layers and [WO4] 2 The perovskite layers are arranged alternately, with a band gap of approximately 2.7-2.8 eV. [This band gap matches well with WO3 (2.6-2.8 eV), both effectively responding to visible light (λ<460 nm), forming the core material basis for the visible light biphase photocatalysis function of this system.] The valence band of Bi2WO6 is approximately +3.2 eV (vs NHE), and the conduction band is approximately +0.46 eV (vs NHE). Together with WO3 (VB: +3.1 eV, CB: +0.3 eV), they form a band gradient-matched bicomponent visible light-responsive system, providing a precise band engineering basis for the subsequent construction of heterojunctions.

[0045] (5) Heterogeneous structure construction and ciprofloxacin targeted degradation mechanism The Bi2WO6 generated in situ during the controlled sintering heat treatment process, together with the residual WO3 phase and the Bi2O3 phase, jointly construct a WO3 / Bi2WO6 / Bi2O3 visible light direct Z-scheme heterojunction system. (1) WO3 (OP, oxidizing photocatalyst): the conduction band position is about +0.3 eV (vs NHE), and the valence band position is about +3.1 eV (vs NHE), providing extremely strong oxidizing photogenerated holes; (2) Bi2WO6 (Z-type interface bridging phase): The conduction band position is approximately +0.46 eV, and the valence band position is approximately +3.2 eV (vsNHE). As an intermediate phase for band coupling between WO3 and residual Bi2O3, it connects the two components through a direct Z-type electron transport path. (3) Bi2O3 (OP', synergistic oxidation phase): The conduction band position is approximately +0.33 eV, and the valence band position is approximately +3.13 eV (vsNHE). The valence band position is similar to that of WO3, and they synergistically provide strong oxidizing holes, thus broadening the visible light absorption coverage.

[0046] Under visible light irradiation, the built-in electric field at the Z-type heterojunction interface drives photogenerated electrons on the Bi₂WO₆ conduction band (+0.46 eV) and photogenerated holes on the WO₃ valence band (+3.1 eV) (or with holes on the Bi₂O₃ valence band at +3.13 eV) to recombine and annihilate at the interface. Simultaneously, it retains strong oxidizing holes (+3.1 eV) on the WO₃ valence band and electrons on either the Bi₂WO₆ or Bi₂O₃ conduction bands. The strong oxidizing holes on the WO₃ valence band (+3.1 eV, far exceeding the standard redox potential of OH at +2.72 eV) can directly oxidize adsorbed water molecules or OH⁻. The formation of ·OH hydroxyl radicals; photogenerated electrons participate in the single-electron reduction of O2 molecules on the surfaces of ZnWO4 and Bi2WO6, producing a small amount of ·O2. - The two active species work synergistically to participate in the targeted degradation of ciprofloxacin.

[0047] The above system targets the pollutant ciprofloxacin (CIP, C 17 H 18 The targeted degradation of FN3O3 (MW = 331.34 g / mol) is based on the precise match between the bond energy characteristics of the CIP molecule and the aforementioned strong ·OH system. The CIP molecule consists of a quinolone-benzopyridine bicyclic core (quinoline ring) and a C3 carboxyl group ( COOH), C4 ketone carbonyl group (C=O), C6 fluorine substituent ( The structure consists of five major structural units: F) and the piperazine group at the C7 position. The bond energies and breaking priorities of the key chemical bonds are as follows: C7 piperazine ring C The N-bond has a bond energy of approximately 305–315 kJ / mol, making it the site with the lowest bond energy in the entire molecule. It is most easily cleaved by electrophilic ·OH groups and is a preferred target for targeted attack. The C3 carboxyl group... COOH bond (approximately 350 kJ / mol) and piperazine ring secondary C N-bond (approximately 350 kJ / mol) is the next best; C6 position C The F bond (approximately 484 kJ / mol) is the target of the defluorination reaction, relying on the strong oxidizing hole (+3.1 eV) in the WO3 valence band to provide sufficient oxidative driving force. The C=C aromatic conjugated bond (approximately 510 kJ / mol) and C4=O carbonyl bond (approximately 745 kJ / mol) of the quinolone ring have the highest bond energies, requiring multi-step synergistic action of active species to achieve ring-opening mineralization. Accordingly, the targeted degradation of ciprofloxacin in the system proceeds in three steps: (1) Target-induced (C7) Piperazine C N-bond preferential breakage and side chain removal: ·OH, due to its high electrophilicity, preferentially attacks the piperazine ring at C7 position of the CIP molecule. The N-bond (305 kJ / mol) initiates ring-opening of the piperazine ring and the stepwise removal of the ethylenediamine side chain, generating a depiperazinylquinolone intermediate, accompanied by the release of NH3; during this stage, ·OH attacks C3. COOH (350 kJ / mol) triggers the decarboxylation reaction. COOH → H + CO2), further reducing molecular stability; (2) C6-position defluorination activation (strong ·OH driven C F-bond breakage): WO3 valence band strong oxidizing hole (+3.1 eV) directly oxidizes or attacks the C6 position of the CIP molecule via high concentration of ·OH. The F bond (484 kJ / mol) enables a defluorination reaction via an electrophilic addition substitution mechanism, with the F atom reacting as F... Released into the water in form, C6 position transforms into C The presence of OH or C=O groups disrupts the π-conjugated system of the quinolone ring, significantly reducing its aromaticity. (3) Ring opening and complete mineralization of quinolone nucleus: ·OH and ·O2 - The synergistic and continuous attack on the bicyclic C=C aromatic conjugated system of quinolone (approximately 510 kJ / mol) and C4=O carbonyl group (approximately 745 kJ / mol) overcomes the aromatic ring conjugation stabilization energy, driving the sequential ring opening of the quinolone core. Through the gradual mineralization of various small molecule intermediates (oxalic acid, acetic acid, formic acid, etc.), CIP is ultimately completely mineralized into CO2, H2O, and F. and NH4 + NO3 Inorganic small molecules; The specificity of this targeted matching stems from the precise fit between the strong oxidizing ·OH system and the bond energy gradient of the CIP molecule: the high electrophilicity of ·OH and the CIP piperazine C The lowest bond energy of the N bond (305 kJ / mol) is highly matched, enabling preferential ring-opening initiation; the strong oxidizing hole of WO3 (+3.1 eV) affects C The breaking of the F bond (484 kJ / mol) provides sufficient thermodynamic driving force to achieve complete defluorination (compared to the TiO2 system with +2.7 eV hole-to-C ratio). (This system has significant advantages over the one that suffers from insufficient driving force for F bond breakage). The Z-type heterojunction mechanism achieves full-spectrum response in the visible light region (λ<460nm) while simultaneously retaining the strong oxidizing holes of both WO3 and Bi2WO6 components. This lays the material foundation for practical solar-driven outdoor water treatment applications, thereby enabling efficient degradation of ciprofloxacin from targeted initiation, defluorination activation to complete mineralization.

[0048] The monolithic tungsten trioxide-based photocatalytic foam ceramic has a cubic shape; compressive strength ≥ 0.5 MPa, porosity ≥ 82%, pore structure connectivity ≥ 80%, and a degradation rate of ciprofloxacin ≥ 94% under visible light. Those skilled in the art can determine the process window that satisfies the above effects through limited experiments under conventional equipment conditions, based on the specific type of tungsten trioxide powder, the type of photocatalytic active component, and the characteristics of the reinforcing phase.

[0049] Example 3 S1: Organic additives and pH adjusters are added to deionized water and dispersed evenly to form a homogeneous solution; tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents are added to the homogeneous solution in batches and dispersed evenly to form a tungsten trioxide-based suspension slurry; fiber and / or whisker reinforcing phases are added to the suspension slurry and dispersed evenly to form a tungsten trioxide-based composite slurry; S2: The organic foam is completely immersed in the tungsten trioxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and excess slurry on the surface is removed by squeezing or centrifugation; then drying treatment is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the tungsten trioxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a wet tungsten trioxide-based foam ceramic blank. S3: The tungsten trioxide-based foam ceramic green body obtained in step S2 is first air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried green body is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while tungsten trioxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phases are initially sintered together to form a tungsten trioxide-based foam ceramic green body with a three-dimensional interconnected pore structure; S4: The green body obtained in step S3 is subjected to controlled sintering heat treatment. Under the action of sintering aids, tungsten trioxide and photocatalytic active components form a continuous and dense ceramic skeleton network through particle fusion and phase boundary bonding, effectively reducing the sintering temperature and ensuring the structural integrity of the three-dimensional interconnected channels. At the same time, the defect control agent inhibits W during high-temperature sintering through solid solution substitution and grain boundary segregation mechanisms. 6+ Excessive reduction, excessive generation of oxygen vacancies, lattice distortion, and abnormal growth of WO3 grains are controlled to keep the grain size within a small range, maintaining a high specific surface area and porosity of the material. During sintering, the reinforcing phase and the foam ceramic skeleton are firmly bonded together. The components construct band-matched heterojunction interfaces or generate new photocatalytically active phases in situ through solid-phase diffusion and interfacial reactions. The electronic structure of the heterojunction interface or the new photocatalytically active phase is precisely matched with the molecular characteristics of the target pollutant, significantly improving the separation efficiency of photogenerated carriers and the interfacial reaction activity. Finally, a visible light-responsive monolithic tungsten trioxide-based photocatalytic foam ceramic is obtained. The three-dimensional skeleton of this ceramic is composed of a continuous network of photocatalytic functional phases, which has excellent mechanical strength, high photocatalytic activity, and specific and efficient degradation ability for the target pollutant.

[0050] In step S1, the tungsten trioxide powder has a purity > 98 wt.% and an average particle size D50 of 5 μm; The photocatalytic active component is zinc oxide (ZnO) with a purity >98 wt.% and an average particle size D50 of 1.5 μm, and the amount added is 45 wt.% of the tungsten trioxide powder mass. The sintering aid is bismuth tungstate (Bi2WO6) with a purity >98 wt.%, an average particle size D50 of 2 μm, and an addition amount of 8 wt.% of the tungsten trioxide powder mass. The defect control agent is zirconium dioxide (ZrO2) with a purity >98 wt.% and an average particle size D50 of 3 μm, and is added at a rate of 5.5 wt.% of the tungsten trioxide powder mass. The organic additives include binders, plasticizers, dispersants, surfactants, rheology modifiers, and defoamers; wherein the binder is a polyurethane emulsion (PU); the plasticizer is triethyl acetylglucosyl citrate (ATEC); the dispersant is polyaspartic acid (PASP); the surfactant is polysorbate 80 (Tween-80); the rheology modifier is guar gum (GG); and the defoamer is silicone oil (Dow Corning® 200 Fluid). The pH adjuster is ammonia water (NH3·H2O, 2 mol / L); The reinforcing phase is potassium hexatitanate (K2Ti6O). 13 Whiskers with an average length of 21 μm and an average diameter of 0.7 μm; The solid content of the tungsten trioxide-based composite slurry is 50 vol.%, and the pH is 10. The amounts of each component of the organic additive and the reinforcing phase are based on the total mass of tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents, and are as follows: binder, 1.6 wt.%; dispersant, 1.4 wt.%; plasticizer, 0.5 wt.%; surfactant, 0.7 wt.%; rheology modifier, 0.9 wt.%; defoamer, 1.6 wt.%; reinforcing phase, 10 wt.%.

[0051] In step S1, the homogeneous solution is uniformly dispersed by mechanical stirring; the tungsten trioxide-based suspension slurry and the composite slurry are also uniformly dispersed by mechanical stirring. For the uniform dispersion of the homogeneous solution, the mechanical stirring speed was 1100 rpm; the stirring time was 15 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. The stirring rate for both the tungsten trioxide-based suspension slurry and the tungsten trioxide-based composite slurry was 1500 rpm; the stirring time was 280 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. In step S2, the organic foam is made of polyurethane (PU), has a pore density of 10 PPI, and has a cylindrical shape. The impregnation is carried out under normal pressure; the impregnation process is carried out at 25°C for 200 seconds. The pressure of the extrusion desizing is controlled within 0.8 MPa, and the thickness of the organic foam after extrusion is compressed to 90% of the original thickness; The drying process employs a programmed temperature increase method, with a drying temperature of 75℃, and continues until the mass change rate is <1% / h. After three cycles of impregnation-desizing-drying-impregnation, the cumulative loading of the composite slurry reaches 480% of the original mass of the organic foam. In step S3, the natural air drying is carried out in a ventilated environment at a temperature of 25°C, a relative humidity of 20%, a ventilation rate of 1 m / s, and a natural air drying time of 12 hours. The heating program for the drying process is as follows: the temperature is increased from room temperature to 70°C at a rate of 10°C / min, and the temperature is maintained for 15 hours. The airflow rate inside the oven is 1 m / s, and the drying endpoint is a mass change rate of <0.05% / h. The degumming heat treatment includes: In the first stage, the temperature is increased to 250℃ at a rate of 9℃ / min and held for 10 min. The second stage involves raising the temperature to 450℃ at a rate of 4℃ / min and holding it for 5 minutes. The third stage involves increasing the temperature to 600℃ at a rate of 1℃ / min and holding it for 1 min. The degumming heat treatment process is carried out under a selected atmosphere, namely air, with a gas flow rate of 1000 mL / min and the furnace pressure maintained at gauge pressure +800 Pa. In step S4, the process conditions for the controlled sintering heat treatment include: sintering temperature 1000℃, constant temperature time 2min, and heating rate 8℃ / min. During the controlled sintering heat treatment, the components undergo the following chemical reactions in sequence, ultimately constructing a cascaded heterojunction system with targeted degradation function: (1) High-temperature decomposition-redeposition activation and liquid-phase densification reaction of sintering aids The sintering aid, bismuth tungstate (Bi2WO6), is a pre-synthesized layered perovskite phase from Aurivillius ([Bi2O2]). 2+ Layers and [WO4] 2 (The perovskite layers are arranged alternately), with a melting point of approximately 960°C. In this embodiment, when the temperature is raised to approximately 960°C, the Bi2WO6 particles undergo solid-phase softening and localized decomposition, releasing a molten Bi2O3 liquid phase (Bi2O3 melting point 824°C). Bi₂WO₆(s) → Bi₂O₃(l) + WO₃ [≥960°C, partial decomposition] The released Bi₂O₃ molten liquid phase exhibits extremely low viscosity and strong wettability at 1000°C, rapidly spreading at the interface between WO₃ and ZnO particles. Driven by capillary forces, it rearranges the particles, filling neck voids and significantly accelerating the densification process. Simultaneously, the decomposed WO₃ active particles replenish the particle neck region in situ, strengthening the neck connection width (controlled within 10 μm) and ensuring the continuity and structural strength of the three-dimensional skeleton. During the 1000°C holding stage, the molten Bi₂O₃ further undergoes a liquid-solid interface reaction with WO₃ and ZnO, generating a Bi₂WO₆ redeposition phase (during cooling) and trace amounts of Bi₂W₂O₉ phase, realizing a three-stage liquid-phase sintering mechanism of [decomposition-activation-repositioning] for the sintering aid. Bi₂O₃(l) + WO₃ → Bi₂WO₆ [cooling and redeposition, at grain boundaries] 2WO3 + Bi2O3(l) → Bi2W2O9 [High WO3 localization, trace amounts] The redeposited Bi2WO6 phase is uniformly coated at the interface between WO3 and ZnO grains in the form of a nanofilm. It not only plays a mechanical role in strengthening grain boundaries, but more importantly, it provides an additional visible light responsive active phase (Bi2WO6 bandgap of about 2.7–2.8 eV, λ<460 nm) for the subsequent S4 photocatalytic heterojunction system, realizing the dual contribution of sintering aid in densification promotion and synergistic enhancement of photocatalytic function.

[0052] (2) Grain boundary / lattice dual stabilization reaction of defect control agents The defect control agent, zirconium dioxide (ZrO2), is a grain boundary / lattice dual-effect stabilizer. 4+ The ionic radius is 0.072 nm, similar to W. 6+ The radius difference (0.060 nm) is approximately 20%, placing it at the edge of the solid solubility limit according to the Hume-Rothery solid solution rule. It possesses a finite but non-zero solid solubility in the WO3 lattice: a small amount of Zr. 4+ W can be occupied through lattice substitution mechanism 6+ Site, forming (Zr, W)O x Finite solid solutions, suppressing W through lattice stress fields 6+ →W 5+ Excessive reduction and stress-driven growth of WO3 grains: Zr 4+ →W 6+ Site (limited solid solution) → enhances the WO3 lattice barrier and suppresses W 6+ reduction Meanwhile, ZrO2 exceeding the solid solubility limit preferentially accumulates in the grain boundary region of WO3 grains through a grain boundary segregation mechanism, dispersing at the grain boundaries as nanoscale m-ZrO2 (monoclinic phase, stable phase at 1000°C) particles, and is further enriched through the Zener pinning mechanism (grain boundary pinning force F). Z = 3Vf·γ / (2r), where Vf is the volume fraction of ZrO2 and r is the particle radius) restricts the grain boundary migration rate, synergistically reducing the average grain size D of WO3 and ZnO. 50 The size is controlled within 5 μm to maintain a high specific surface area and photocatalytic active site density of the foam ceramic skeleton, while preventing abnormal growth of ZnO grains at high temperatures (ZnO has stronger sintering activity than WO3, and grain growth is significant at 1000°C without inhibition measures).

[0053] During the 1000°C holding period, the ZrO2 and WO3 enriched at the grain boundaries can undergo trace solid-phase interfacial reactions, generating in situ a zirconate tungstate interfacial phase with negative thermal expansion characteristics. ZrO2 + 2WO3 → ZrW2O8 [trace amount at grain boundaries, 1000°C] The generated ZrW2O8 phase (cubic structure) has the following properties: The isotropic negative thermal expansion coefficient (NTE, α ≈ 0.05) is found in the range of 273°C to approximately 777°C. 9.1×10 6 K 1 In the foam ceramic skeleton, the ZrW2O8 phase expands in volume during cooling, which can effectively compensate for the thermal shrinkage of the matrix WO3 phase. It introduces compressive stress at the grain boundaries, which significantly inhibits the initiation and propagation of skeleton microcracks during thermal cycling, thereby improving the structural reliability and thermal stability of foam ceramics under actual water treatment conditions.

[0054] (3) Enhanced in-situ interfacial reaction between the phase and the matrix The reinforcing phase potassium hexatite (K2Ti6O) 13 Whiskers belong to the active reinforcing phase, and their interfacial reaction mechanism during the 1000°C high-temperature sintering process differs from that of the TiO2-based system—the matrix in this embodiment is ZnO, not TiO2. During the 1000°C holding stage, K2Ti6O… 13 Ti on whisker surface 4+ Migrating outward through solid-phase diffusion, it interacts with Zn in the ZnO matrix. 2+ An in-situ solid-state reaction occurs at the whisker-matrix interface to form a zinc titanate bonded layer: K2Ti6O 13 (TiO2 diffused onto whisker surface) + ZnO → ZnTiO3 [interfacial bonding layer, 10-30 nm, 1000°C] The generated ZnTiO3 (hexagonal perovskite zinc titanate, band gap approximately 3.0-3.2 eV) is produced in K2Ti6O 13 A continuous chemically bonded interfacial layer with a thickness of approximately 10–30 nm is formed at the interface between the whiskers and the ZnO matrix; due to K2Ti6O 13 Both ZnO and ZnTiO3 belong to oxide ceramics and have good chemical compatibility. Their interfacial bonding is mainly chemically bonded, resulting in a significantly better reinforcing effect than physically anchored inert reinforcing phases. Furthermore, the ZnTiO3 phase at the interface itself possesses photocatalytic activity (UV-near-visible region), which is also observed in K2Ti6O3. 13 A photocatalytic functional coating is formed on the surface of the whiskers, which adds additional photocatalytic active sites to the skeleton ribs while strengthening them mechanically, thus achieving a synergistic contribution of the reinforcing phase in both mechanical toughening and photocatalytic function enhancement.

[0055] (4) In-situ formation reaction of photocatalytically active new phase The photocatalytically active component zinc oxide (ZnO) and WO3 undergo solid-phase diffusion and in-situ reaction during high-temperature sintering at 1000°C to generate a new photocatalytically active phase, zinc tungstate (ZnWO4), which is of the ferrotungstate type. ZnO + WO3 → ZnWO4 [Main product, ferrotungsten structure, 1000°C] ZnWO4 has a wolframite structure (monoclinic, P2 / c space group) with a band gap of approximately 3.7–4.0 eV (UV response) and possesses the following important characteristics: (i) excellent photochemical stability: Zn 2+ –O–W 6+ The bonding network endows ZnWO4 with extremely strong chemical inertness, enabling it to operate stably in strong acid / alkaline water treatment environments and avoiding the risk of dissolution and corrosion of ZnO in acidic solutions; (ii) Synergistic photocatalytic function: The conduction band of ZnWO4 is located at approximately 0.5~0 eV (vs NHE), the valence band position is about +3.5~4.0 eV, forming a band gradient match with WO3 and ZnO; (iii) WO3 volatilization inhibition effect: the formation of the new ZnWO4 phase will reduce the W of WO3 6+ By immobilizing it in the form of tungstate, the volatilization loss of WO3 at 1000°C is effectively suppressed (WO3 volatilization increases sharply with increasing temperature), and the stoichiometric ratio of the photocatalytic active components is maintained stably.

[0056] (5) Heterogeneous structure construction and bisphenol A targeted degradation mechanism The ZnWO4 generated in situ during the controlled sintering heat treatment process, together with the residual ZnO phase, WO3 phase, and Bi2WO6 phase redeposited at the grain boundaries, jointly construct a WO3 / ZnO / ZnWO4 direct Z-scheme heterojunction system. Bi2WO6 participates in carrier transport as a grain boundary gain phase. (1) WO3 (OP, oxidizing photocatalyst): The conduction band position is about +0.3 eV (vs NHE), and the valence band position is about +3.1 eV (vs NHE), providing extremely strong oxidizing photogenerated holes, directly driving the high concentration of ·OH generation; (2) ZnO (RP, reduced photocatalyst): The conduction band position is approximately With a voltage of 0.3 eV (vs NHE) and a valence band position of approximately +2.9 eV (vs NHE), it provides strongly reducing conduction band electrons, efficiently driving the single-electron reduction of O2 to produce O2. - Superoxide radicals; (3) ZnWO4 (band bridging intermediate phase): the conduction band position is approximately With a valence band of 0.3–0 eV and a valence band position of approximately +3.5–4.0 eV (vs NHE), it serves as a band gradient bridging phase between WO3 and ZnO, and the directional recombination and annihilation of electrons and holes at the Z-type interface is assisted by the built-in electric field of ZnWO4. (4) Bi2WO6 (grain boundary gain phase): The conduction band position is approximately +0.46 eV, and the valence band position is approximately +3.2 eV (vsNHE). It is distributed in the form of a thin film at the grain boundary. Under visible light (λ<460 nm) irradiation, it generates additional photogenerated holes, participates in Z-type charge transport at the interface, and broadens the overall visible light response coverage.

[0057] Under visible light irradiation, the built-in electric field at the WO3 / ZnO interface drives the weakly reducing electrons (+0.3 eV) in the WO3 conduction band and the weakly oxidizing holes (+2.9 eV) in the ZnO valence band to recombine and annihilate in a directional manner at the ZnWO4 bridging interface; simultaneously, the strong reducing electrons in the ZnO conduction band are retained. 0.3 eV) Highly efficient reduction of O2 to produce O2 - And the highly oxidizing holes in the WO3 valence band (+3.1 eV, far exceeding the standard redox potential of ·OH +2.72 eV vs NHE) efficiently oxidize water molecules / OH. It generates ·OH, enabling a synergistic and efficient supply of dual active species.

[0058] The above system is effective against the target pollutant bisphenol A (BPA, C). 15 H 16 Targeted degradation of O2 (i.e., 4,4'-isopropylidene bisphenol), based on the bond energy characteristics of BPA molecules and the aforementioned ·OH-dominant / ·O2 - Precise matching of the synergistic system. The BPA molecule consists of two p-hydroxyphenol groups connected by an isopropylidene group (…). C(CH 32) The carbon bridges connect the bonds, and the bond energies and breaking priorities of the key chemical bonds are as follows: Isopropylidene carbon bridge C The C bond energy is approximately 346 kJ / mol, making it the lowest bond energy site in the entire molecule. It is the weakest link in the molecule most vulnerable to attack and breakage by active species, and thus the core target site for targeted attack. (Phenol C...) The OH bond (approximately 360 kJ / mol) is the next strongest, followed by the hydrogen C bonds in the benzene ring. Following the H bond (approximately 413 kJ / mol), the aromatic C=C conjugated bond of the benzene ring (approximately 510 kJ / mol) has the highest bond energy, requiring synergy between two active species to achieve ring-opening mineralization. Therefore, the targeted degradation of bisphenol A in this system proceeds in three steps: (1) Targeted initiation (isopropylene carbon bridge C) C-bond breakage, dissociation of the two phenolic rings: WO3's strong oxidizing hole (+3.1 eV) directly oxidizes the phenolic hydroxyl group in the BPA molecule, which has a higher electron cloud density. OH), inducing single-electron oxidation to form phenoxy radicals (PhO·); simultaneously, high concentrations of ·OH (highly electrophilic) preferentially attack the isopropylidene carbon bridge C. C bond (346 kJ / mol), inducing C C-homogeneous cleavage breaks down the bibenzene ring structure of BPA into two independent p-hydroxybenzyl alcohol / benzoquinone intermediates and acetone molecules, completing the dissociation of the core structure of the BPA molecule; BPA + ·OH → phenoxy radical + benzoquinone intermediate + CH3COCH3 (2) Phenolic ring hydroxylation activation (phenol C) OH oxygenates, forming a catechol / hydroquinone intermediate: · OH attacks the high electron cloud density carbons at C2 and C4 positions of the phenol ring (C (OH- ortho-para activation) introduces additional [resources] through electrophilic addition-hydrogenation reaction. OH, converting phenol (C6H5OH) sequentially into catechol (catechol) and hydroquinone (hydroquinone); ·O2 - Further nucleophilic addition with the benzoquinone intermediate accelerates the destruction of the benzene ring π-conjugated system, providing a low-barrier channel for subsequent ring opening; (3) Ring opening and complete mineralization of benzene ring: ·OH and ·O2 - The synergistic and continuous attack on the C=C aromatic conjugated system of the benzene ring of catechol / hydroquinone (approximately 510 kJ / mol) overcomes the stabilization energy of the aromatic ring conjugation through the addition-elimination mechanism of hydroxyl radicals, thereby driving the ring opening of the benzene ring in sequence. Through the gradual oxidation and mineralization of short-chain fatty acid intermediates such as maleic acid, oxalic acid, acetic acid, and formic acid, BPA is finally completely mineralized into inorganic small molecules such as CO2 and H2O. The specificity of this targeted matching stems from the precise fit between the distribution of active species in the system and the bond energy gradient of BPA: the high electrophilicity of ·OH and the isopropylidene carbon bridge of BPA. The C bond's lowest bond energy (346 kJ / mol) is highly matched, enabling preferential breakage and dissociation of the core structure; the strong oxidizing hole (+3.1 eV) of WO3 exerts a much stronger direct oxidation driving force on the phenolic hydroxyl group (potential approximately +0.7–1.0 eV vs NHE) than the TiO2 system (+2.7 eV), achieving a high concentration accumulation of phenoxy radicals; the strong reducing conduction band of ZnO ( O2 produced at 0.3 eV - The nucleophilic addition to the benzoquinone intermediate is precisely matched, achieving synergistic ring opening; the Z-type heterojunction mechanism facilitates the interaction of ·OH and ·O2. - The simultaneous retention of high redox potentials of the two active species ensures a continuous and efficient attack capability on the high bond energy benzene ring system (510 kJ / mol), thereby achieving efficient and targeted degradation of bisphenol A throughout the entire process from core structure dissociation, phenol hydroxylation activation to complete mineralization.

[0059] The monolithic tungsten trioxide-based photocatalytic foam ceramic has a cylindrical macroscopic shape; compressive strength ≥ 0.7 MPa, porosity ≥ 81%, pore structure connectivity ≥ 80%, and bisphenol A degradation rate ≥ 93% under visible light; Those skilled in the art can determine the process window that satisfies the above effects through limited experiments under conventional equipment conditions, based on the specific type of tungsten trioxide powder, the type of photocatalytic active component, and the characteristics of the reinforcing phase.

[0060] Example 4 S1: Organic additives and pH adjusters are added to deionized water and dispersed evenly to form a homogeneous solution; tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents are added to the homogeneous solution in batches and dispersed evenly to form a tungsten trioxide-based suspension slurry; fiber and / or whisker reinforcing phases are added to the suspension slurry and dispersed evenly to form a tungsten trioxide-based composite slurry; S2: The organic foam is completely immersed in the tungsten trioxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and excess slurry on the surface is removed by squeezing or centrifugation; then drying treatment is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the tungsten trioxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a wet tungsten trioxide-based foam ceramic blank. S3: The tungsten trioxide-based foam ceramic green body obtained in step S2 is first air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried green body is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while tungsten trioxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phases are initially sintered together to form a tungsten trioxide-based foam ceramic green body with a three-dimensional interconnected pore structure; S4: The green body obtained in step S3 is subjected to controlled sintering heat treatment. Under the action of sintering aids, tungsten trioxide and photocatalytic active components form a continuous and dense ceramic skeleton network through particle fusion and phase boundary bonding, effectively reducing the sintering temperature and ensuring the structural integrity of the three-dimensional interconnected channels. At the same time, the defect control agent inhibits W during high-temperature sintering through solid solution substitution and grain boundary segregation mechanisms. 6+Excessive reduction, excessive generation of oxygen vacancies, lattice distortion, and abnormal growth of WO3 grains are controlled to keep the grain size within a small range, maintaining a high specific surface area and porosity of the material. During sintering, the reinforcing phase and the foam ceramic skeleton are firmly bonded together. The components construct band-matched heterojunction interfaces or generate new photocatalytically active phases in situ through solid-phase diffusion and interfacial reactions. The electronic structure of the heterojunction interface or the new photocatalytically active phase is precisely matched with the molecular characteristics of the target pollutant, significantly improving the separation efficiency of photogenerated carriers and the interfacial reaction activity. Finally, a visible light-responsive monolithic tungsten trioxide-based photocatalytic foam ceramic is obtained. The three-dimensional skeleton of this ceramic is composed of a continuous network of photocatalytic functional phases, which has excellent mechanical strength, high photocatalytic activity, and specific and efficient degradation ability for the target pollutant.

[0061] In step S1, the tungsten trioxide powder has a purity > 98 wt.% and an average particle size D50 of 5 μm; The photocatalytic active component is indium trioxide (In₂O₃), with a purity >98 wt.%, an average particle size D50 of 2 μm, and an addition amount of 55 wt.% of the tungsten trioxide powder mass. The sintering aid is calcium carbonate (CaCO3) with a purity >98 wt.%, an average particle size D50 of 4 μm, and an addition amount of 8 wt.% of the tungsten trioxide powder mass. The defect control agent is cerium dioxide (CeO2) with a purity >98 wt.%, an average particle size D50 of 1 μm, and an addition amount of 5 wt.% of the tungsten trioxide powder mass. The organic additives include binders, plasticizers, dispersants, surfactants, rheology modifiers, and defoamers; wherein the binder is polyacrylamide (PAM); the plasticizer is polycaprolactone (PCL); the dispersant is sodium polyacrylate (NaPAA); the surfactant is octylphenyl polyoxyethylene ether (Triton X-100); the rheology modifier is gellan gum (GeG); and the defoamer is n-octanol (NOA). The pH adjuster is ammonia water (NH3·H2O, 2 mol / L); The reinforcing phase is silicon carbide (SiC) whiskers and potassium hexatitanate (K2Ti6O). 13 The fibers are silicon carbide whiskers with an average length of 18 μm and an average diameter of 0.4 μm; and potassium hexatite fibers with an average length of 17 μm and an average diameter of 0.7 μm. The solid content of the tungsten trioxide-based composite slurry is 56 vol.%, and the pH is 10. The addition amounts of each component of the organic additive and the reinforcing phase are based on the total mass of tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents, and are as follows: binder, 1.6 wt.%; dispersant, 0.9 wt.%; plasticizer, 1.3 wt.%; surfactant, 0.8 wt.%; rheology modifier, 1.6 wt.%; defoamer, 1.1 wt.%; reinforcing phase, 11 wt.%.

[0062] In step S1, the homogeneous solution is uniformly dispersed by mechanical stirring; the tungsten trioxide-based suspension slurry and the composite slurry are also uniformly dispersed by mechanical stirring. For the uniform dispersion of the homogeneous solution, the mechanical stirring speed was 900 rpm; the stirring time was 11 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. The stirring rate for both the tungsten trioxide-based suspension slurry and the composite slurry was 1300 rpm; the stirring time was 380 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. In step S2, the organic foam is made of polyurethane (PU), has a pore density of 10 PPI, and has a macroscopic shape of cuboid. The impregnation was carried out under normal pressure; the impregnation process was conducted at 29°C for 240 seconds. The pressure of the extrusion desizing is controlled within 0.9 MPa, and the thickness of the organic foam after extrusion is compressed to 90% of the original thickness; The drying process employs a programmed temperature increase method, with a drying temperature of 70℃, and continues until the mass change rate is <1% / h. After five cycles of impregnation-desizing-drying-impregnation, the cumulative loading of the composite slurry reaches 550% of the original mass of the organic foam. In step S3, the natural air drying is carried out in a ventilated environment at a temperature of 21°C, with a relative humidity of 10%, a ventilation rate of 1 m / s, and a natural air drying time of 12 hours. The heating program for the drying process is as follows: the temperature is increased from room temperature to 75°C at a rate of 5°C / min, and the temperature is maintained for 8 hours. The airflow rate inside the oven is 1 m / s, and the drying endpoint is a mass change rate of <0.05% / h. The degumming heat treatment includes: The first stage involves raising the temperature to 250℃ at a rate of 10℃ / min and holding it for 60 min. The second stage involves raising the temperature to 450℃ at a rate of 5℃ / min and holding it for 10 minutes. The third stage involves increasing the temperature to 600℃ at a rate of 2℃ / min and holding it for 5 minutes. The degumming heat treatment process is carried out under a selected atmosphere, namely air, with a gas flow rate of 1000 mL / min and the furnace pressure maintained at gauge pressure +800 Pa. In step S4, the process conditions for the controlled sintering heat treatment include: sintering temperature 900℃, isothermal time 2min, and heating rate 6℃ / min. During the controlled sintering heat treatment, the components undergo the following chemical reactions in sequence, ultimately constructing a cascaded heterojunction system with targeted degradation function: (1) Thermal decomposition and activation reaction of sintering aids The sintering aid calcium carbonate (CaCO3) undergoes a two-step reaction during heat treatment. The initial decomposition temperature of CaCO3 is approximately 840°C, and in this embodiment, complete decomposition is achieved at approximately 875°C, generating highly active nano-sized CaO particles. CaCO3 → CaO + CO2↑ [≥840°C, thermal decomposition] The in-situ generated nanoscale CaO has extremely high activity (large surface area and high lattice defect density). Under sintering conditions of 900°C, it rapidly undergoes a solid-phase reaction at the interface with WO3 particles to generate a scheelite-type calcium tungstate (CaWO4) activated phase. CaO + WO3 → CaWO4 [scheelite structure, 900°C] The generated CaWO4 has a scheelite-type structure (space group I41 / a), a melting point of approximately 1620°C, and is stable at a sintering temperature of 900°C. CaWO4 forms a highly active tungstate liquid-phase precursor layer at the interface between WO3 and In2O3 particles—the Ca at its grain boundaries… 2+ –O–W 6+ The bonded network can reduce the surface energy between WO3 particles, driving the rearrangement of WO3 and In2O3 particles through a solid-state mass transfer mechanism. The width of the neck connection region between particles is controlled within 10 μm, effectively promoting the formation of a continuous skeleton network structure in the foam ceramic. Simultaneously, the CaWO4 phase will partially bind the WO3 particles to the bonded network. 6+ By immobilizing it in the form of tungstate, the volatilization loss of WO3 is further suppressed within a relatively mild sintering temperature window of 900°C, maintaining the stoichiometric stability of the photocatalytic active components. In addition, CaWO4 itself has photoluminescence properties (band gap of approximately 5.0 eV, ultraviolet region), which can convert short-wave ultraviolet light into visible light, thus providing auxiliary compensation for the visible light absorption of WO3 and exerting a synergistic down-conversion gain effect within the framework.

[0063] (2) Oxygen activity self-regulation and grain boundary stabilization reaction of defect control agents The defect control agent, cerium dioxide (CeO2), belongs to the oxygen activity self-regulating stabilizer (class d), and its core working mechanism is the same as that of La in Examples 1–3. 3+ Mo 6+ Zr 4+ Static stabilizers are quite different—CeO2 via Ce 4+ / Ce 3+ The reversible redox pair dynamically releases / stores oxygen during sintering, actively maintaining the localized oxidizing atmosphere around WO3 particles from a thermodynamic perspective, and using chemical driving force to inhibit W 6+ →W 5+ Excessive reduction reaction: 2CeO2 Ce2O3 + ½O2 [Dynamic oxygen release, T>700°C] Ce₂O₃ + ½O₂ → 2CeO₂ [Cooling and oxygen storage, oxidizing atmosphere] During the sintering and holding stage at 900°C, when the local oxygen partial pressure around the WO3 particles decreases due to the consumption of solid-phase mass transfer at high temperature, CeO2 spontaneously flows through Ce... 4+ →Ce 3+ Reduction reaction (E°(Ce) 4+ / Ce 3+ (≈ +1.61 V vs NHE) releases O2 into the environment, actively replenishing the localized oxidizing atmosphere near the WO3 particles, making W 6+ The chemical potential is maintained within the thermodynamically stable range, fundamentally suppressing the growth of tungsten bronze (WO3). x The formation of color center defects; when the oxygen partial pressure increases during the cooling stage, Ce... 3+ Re-oxidized to Ce 4+ (Oxygen storage process) completes the dynamic oxygen buffer cycle. This three-stage self-regulating mechanism of [oxygen release-steady state-oxygen storage] endows this embodiment with the ability to regulate W 6+ The highest thermodynamic protection level for valence states, especially suitable for sintering temperature ranges above 900°C. 6+ Restore working conditions where risks are significantly increased.

[0064] Ce 4+ The ionic radius (r = 0.087 nm) is much larger than that of W. 6+ (0.060 nm) does not satisfy the solid solution rule, therefore its solid solubility in WO3 is extremely low, and it mainly exhibits a grain boundary segregation mechanism, accumulating at the grain boundaries of WO3 and In2O3 to form a nanoscale CeO2 segregation layer. The CeO2 enriched at the grain boundaries simultaneously inhibits the abnormal growth of WO3 and In2O3 grains through a solute dragging effect, reducing the average grain size D of the two phases. 50 The synergistic control is within 3 μm, maintaining a high specific surface area and photocatalytic active site density of the foam ceramic skeleton.

[0065] Furthermore, under sintering conditions at 900°C, a small amount of CeO2 and WO3 at the grain boundaries can undergo a trace solid-phase interfacial reaction to generate a cerium tungstate interfacial phase, further locking the W at the grain boundaries. 6+ Price state: 3WO3 + Ce2O3 → Ce2(WO4)3 [trace amount at grain boundaries, Ce] 3+ It is stabilized by oxidation to Ce 4+ ] (3) Enhanced in-situ interfacial reaction between the phase and the matrix In this embodiment, the reinforcing phase consists of silicon carbide (SiC) whiskers and potassium hexatitanate (K2Ti6O). 13 The fiber composite structure exhibits different interfacial bonding mechanisms during sintering: ① SiC whiskers – Inert reinforcing phase, high-temperature oxidation to form a SiO2 passivation anchoring layer: SiC whiskers have extremely high chemical stability. In an air atmosphere at 900°C, slight controllable oxidation occurs on the whisker surface (the oxidation rate is controlled by the dense SiO2 passivation film), forming a continuous SiO2 passivation film with a thickness of about 1–5 nm on the whisker surface. SiC (surface) + O2 → SiO2 (passivation layer) + CO2 [900°C, air, slightly controllable] The generated SiO2 passivation film does not undergo significant solid-state reaction with WO3 or In2O3 (because the activation energy of the solid-state reaction of the SiO2–WO3 system is high at 900°C). It mainly achieves a firm bond between SiC whiskers and the foam ceramic skeleton through surface micro-interlocking and physical interlocking mechanisms. The excellent mechanical properties of SiC whiskers (elastic modulus of about 480 GPa and flexural strength of about 800 MPa) provide a high-modulus load transfer path for the foam ceramic skeleton ribs, significantly improving compressive strength and crack propagation resistance.

[0066] ② K2Ti6O 13 Fiber-active reinforcing phase, with indium titanate bonding layer formed at the interface: potassium hexatitanate (K2Ti6O) 13 The fiber belongs to the active reinforcing phase. During the high-temperature sintering process at 900°C, the Ti layer on the fiber surface... 4+ Migrating outwards via solid-phase diffusion, it interacts with In in the In2O3 matrix. 3+ An in-situ solid-state reaction occurs at the fiber-matrix interface to generate an indium titanate bonding layer: TiO2 (K2Ti6O) 13 Surface diffusion) + In₂O₃ → In₂TiO₅ [interfacial bonding layer, 5–20 nm, 900°C] The generated In2TiO5 (indium titanate, orthorhombic crystal system, Pbam space group) in K2Ti6O 13 A continuous chemically bonded interfacial layer with a thickness of approximately 5–20 nm is formed at the interface between the fiber and the In₂O₃ matrix, upgrading the fiber-matrix bonding mode from physical intercalation to chemical bonding, significantly improving the interfacial shear strength. Crucially, the In₂TiO₅ band gap is approximately 2.6–2.9 eV (visible light response, λ < 480 nm), and its conduction band position is approximately... 0.4~ 0.5 eV (vs NHE), valence band position approximately +2.2 to +2.4 eV (vs NHE), and In2O3 (CB ≈ (0.6 eV, VB ≈ +2.3 eV) constitute a highly band-matched photocatalytic functional phase combination, jointly participating in the subsequent construction of the S-type heterojunction system; in addition, the formation of the In2TiO5 phase will... 13 The fibers are firmly anchored in the matrix, completely avoiding the risk of fiber detachment under actual water treatment conditions, and achieving a synergistic contribution of the reinforcing phase in terms of both mechanical strength and photocatalytic functional gain.

[0067] (4) In-situ formation reaction of photocatalytically active new phase The photocatalytic active component, indium trioxide (In₂O₃), undergoes an interfacial reaction with WO₃ via solid-phase diffusion during sintering at 900°C. 3+ Diffusion towards the WO3 particle interface leads to the in-situ formation of a new photocatalytically active phase of indium tungstate. In₂O₃ + 3WO₃ → In₂(WO₄)₃ [Indium tungstate, 900°C, WO₃-rich region] In₂O₃ + WO₃ → 2InWO₄ [ferrotungsten type, 900°C, localized reaction] The amount of indium tungstate phase generated is limited by both sintering temperature (900°C) and holding time (extremely short 2 min). It is mainly enriched at the interface between WO3 and In2O3 particles and distributed in the form of nanoscale interfacial thin film. A large amount of unreacted WO3 phase and In2O3 phase maintain the original crystal phase structure and jointly participate in the construction of photocatalytic functional phase network.

[0068] The residual In₂O₃ phase possesses the following key photoelectric properties: a band gap of approximately 2.9 eV (λ < 427 nm, near-edge response in visible light); and a conduction band position of approximately [missing information]. 0.6 eV (vs NHE), compared to TiO2 ( (0.5 eV) exhibits stronger reducing power, enabling efficient driving of O2 single-electron reduction to produce O2. - (E°(O2 / ·O2) -)= 0.33 eV), and provides to meet C The high overpotential reducing electrons required for the reduction and breaking of F bonds are crucial for the reductive defluorination and degradation of perfluorinated compounds. The valence band position is approximately +2.3 eV (vsNHE), with moderate photogenerated holes. Combined with the strong oxidizing holes of WO3 (+3.1 eV), it forms a wide oxidation potential coverage range, which is well-suited to the multi-level bond energy distribution of the PFOA molecule.

[0069] (5) Heterogeneous structure construction and perfluorooctanoic acid targeted degradation mechanism In2TiO5 (from K2Ti6O) generated in situ during the above controlled sintering heat treatment process 13 (Fiber interface reaction), together with the residual In2O3 phase and WO3 phase, the three together construct a WO3 / In2O3 / In2TiO5 ternary S-scheme heterojunction system: (1) In2O3 (RP, reduced photocatalyst): The conduction band position is approximately 0.6 eV (vs NHE), valence band position approximately +2.3 eV (vs NHE), providing extremely strong reducing conduction band electrons (overpotential up to 0.27 eV relative to O2). - (Generation potential), efficiently generating O2 - Superoxide radicals, under light irradiation, generate hydrated electrons from the highly reducing electrons accumulated in the conduction band of In₂O₃. (aq) E° ≈ 2.9 eV vs NHE), which is the driving force behind the perfluorinated compound C F-bond reduction fracture of the core active species; (2) WO3 (OP, oxidizing photocatalyst): The conduction band position is approximately +0.3 eV (vs NHE), and the valence band position is approximately +3.1 eV (vs NHE), providing extremely strong oxidizing photogenerated holes (overpotential reaches 0.38 eV relative to ·OH generation potential +2.72 eV), efficiently oxidizing water molecules / OH High concentrations of ·OH are generated, and photo-Kolbe decarboxylation of the PFOA carboxyl head is driven by direct hole oxidation. (3) In2TiO5 (band gradient bridging intermediate phase): the conduction band position is approximately 0.4~ The valence band is approximately +2.2 to +2.4 eV (vs NHE), and the energy band position is between In2O3 and WO3, forming an energy band gradient bridging structure. The built-in electric field between the In2TiO5 conduction band and the WO3 valence band drives the weakly reducing conduction band electrons (+0.3 eV) of WO3 and the weakly oxidizing valence band holes (+2.3 eV) of In2O3 to recombine and annihilate in a directional manner at the In2TiO5 bridging interface, while retaining the strong reducing conduction band electrons of In2O3. The valence band of WO3 (+3.1 eV) and the strong oxidizing properties of 0.6 eV enable the synergistic and efficient supply of dual active species.

[0070] The above system is effective against the target pollutant perfluorooctanoic acid (PFOA, C7F). 15 The targeted degradation of COOH (MW = 414.07 g / mol) is based on the precise matching between the extreme bond energy distribution characteristics of the PFOA molecule and the aforementioned dual-active species redox synergistic system. The PFOA molecule consists of a perfluoroheptyl chain (CF3(CF... 2)6 ) and carboxylic acid group ( Composed of COOH), the bond energies and breaking difficulties of each key chemical bond are as follows: C The COOH carboxylic acid bond energy is approximately 350 kJ / mol, which is the lowest bond energy site in the entire molecule and a core target for oxidation-induced attack; the perfluorocarbon chain backbone is C The C bond energy is approximately 346-360 kJ / mol, making it a secondary target for the depolymerization of the PFOA carbon skeleton; C The F bond energy is approximately 485 kJ / mol, the highest bond energy site in the entire molecule. Its breakage (defluorination) is the most energy-barrier and challenging step in the PFOA mineralization process, and is also the fundamental reason why PFOA is far more difficult to degrade than other organic pollutants. The F bond is extremely polar (F electronegativity 3.98, the highest), and its bond energy is higher than that of the C bond. H (413 kJ / mol), C Common bond types such as O (360 kJ / mol), and the traditional ·OH oxidation pathway for C The thermodynamic driving force for F-bond breakage is insufficient. Therefore, the targeted degradation of perfluorooctanoic acid in the WO3 / In2O3 / In2TiO5S heterojunction system proceeds in three steps: (1) Oxidation initiation: Photo-Kolbe decarboxylation of the carboxyl head (C COOH, 350 kJ / mol: WO3 valence band strongly oxidizing hole (+3.1 eV) directly oxidizes the carboxyl group in the PFOA molecule ( COO The highest occupied molecular orbital (HOMO) of CO2 is used to oxidize and decarboxylate the carboxylate group in one step via photokolbe decarboxylation, generating a perfluoroheptyl radical and CO2:C7F. 15 COO +h + (VB, +3.1eV)→C7F 15 +CO2; This step relies on the valence band potential of WO3 (+3.1 eV) far exceeding COO The HOMO energy level (approximately +1.0 to +1.5 eV vs NHE) provides sufficient thermodynamic driving force to achieve rapid decarboxylation initiation, while traditional materials such as TiO2 (+2.7 eV) have significantly insufficient driving force in this step; (2) Reduction defluorination: C F-bond reduction cleavage at high overpotential (485 kJ / mol): In₂O₃ conduction band high reducing electrons ( 0.6 eV) and the resulting hydrated electrons (e (aq) E° ≈ 2.9 eV vs NHE) attacking perfluoroheptyl radical (C7F) 15 C in ·) F bonds (485 kJ / mol) drive C through an electron transfer reduction mechanism. The gradual breaking of F bonds, with F Defluorination in sequence: C n F 2n+1 ·+e (aq) →C n F 2n · →C n 1F 2n 1·+·CF (F Release) [stepwise defluorination chain reaction]; ·O2 - Superoxide radicals (E°(·O2)) - ) ≈ (0.33 eV) synergistically participates in the reductive defluorination of perfluoroalkyl chains, especially for low-carbon intermediates (C1–C4 perfluoro segments). F-bond breaking provides additional reduction driving force, accelerating the defluorination process of short-chain perfluorinated intermediates; (3) Cooperative oxidative mineralization of short-chain perfluorinated intermediates: After decarboxylation in step (1) and step-by-step reduction defluorination in step (2), PFOA is gradually degraded into short-chain perfluorinated carboxylic acids (C1–C6 perfluorinated carboxylic acids, such as PFBA and PFPeA). Subsequently, ·OH (generated by strong oxidative holes in WO3) performs photo-Kolbe decarboxylation on the short-chain perfluorinated carboxylic acids again, combined with high concentrations of e (aq) The reductive defluorination process involves alternating cycles of oxidative decarboxylation and reductive defluorination, gradually mineralizing PFOA completely into CO2 (carbon mineralization) and HF (fluorine mineralization, with all F converted to F2). It releases inorganic small molecules such as H2O in various forms, achieving complete deconstruction and harmlessness of the perfluorocarbon chain.

[0071] The specificity of the targeted matching stems from the system's precise response strategy to the challenge of PFOA's dual extreme bond energies: targeting C The COOH bond (350 kJ / mol) is rapidly initiated by photo-Kolbe decarboxylation relying on the strong oxidizing hole (+3.1 eV) of WO3, thus overcoming the bottleneck of insufficient driving force in traditional systems; targeting C F bond (485 kJ / mol), dependent on the highly reducing conduction band of In₂O₃ ( 0.6 eV) generates hydrated electrons (e (aq) E° ≈ 2.9 eV), far exceeding C The reduction potential of the thermodynamic threshold for F-bond breaking drives the gradual defluorination, which is a unique advantage of In2O3 as a photocatalytically active component (in contrast, the conduction band potentials of TiO2 or ZnO are relatively mild and cannot effectively generate hydrated electrons); the S-type heterojunction mechanism simultaneously retains the strong reduction conduction band electrons of In2O3. The 0.6 eV and the strong oxidative valence band hole of WO3 (+3.1 eV) enable the synergistic process of oxidation initiation and reductive defluorination under visible light, thereby achieving efficient and targeted degradation of perfluorooctanoic acid from carboxyl group-initiated decarboxylation, stepwise defluorination of the perfluorocarbon chain to complete mineralization of short-chain intermediates.

[0072] The monolithic tungsten trioxide-based photocatalytic foam ceramic has a cuboid macroscopic shape; compressive strength ≥ 0.5 MPa, porosity ≥ 85%, pore structure connectivity ≥ 80%, and a degradation rate of perfluorooctanoic acid (PFOA) ≥ 95% and a defluorination rate ≥ 90% under visible light. Those skilled in the art can determine the process window that satisfies the above effects through limited experiments under conventional equipment conditions, based on the specific type of tungsten trioxide powder, the type of photocatalytic active component, and the characteristics of the reinforcing phase.

[0073] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any form or substance. It should be noted that those skilled in the art can make several improvements and additions without departing from this application, and these improvements and additions should also be considered within the scope of protection of this application.

Claims

1. A method for preparing a visible light-responsive monolithic tungsten trioxide-based photocatalytic foam ceramic, characterized in that, Includes the following steps: Step S1: Preparation of tungsten trioxide-based composite slurry Organic additives and pH adjusters are added to deionized water and dispersed evenly to form a homogeneous solution; tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents are added to the homogeneous solution in batches and dispersed evenly to form a tungsten trioxide-based suspension slurry; fiber and / or whisker reinforcing phases are added to the suspension slurry and dispersed evenly to form a tungsten trioxide-based composite slurry; Step S2: Preparation of tungsten trioxide-based foam ceramic wet blank The organic foam is completely immersed in the tungsten trioxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and excess slurry on the surface is removed by squeezing or centrifugation; then drying treatment is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the tungsten trioxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a wet tungsten trioxide-based foam ceramic blank. Step S3: Preparation of tungsten trioxide-based foam ceramic green body The tungsten trioxide-based foam ceramic green body obtained in step S2 is first air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried green body is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while tungsten trioxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phase are sintered together to form a tungsten trioxide-based foam ceramic green body with a three-dimensional interconnected pore structure. Step S4: Sintering and Heterogeneous Structure Construction The green body obtained in step S3 is subjected to controlled sintering heat treatment, wherein sintering aids promote the fusion of tungsten trioxide and photocatalytic active components to form a ceramic framework network, and defect control agents inhibit grain growth through solid solution doping; during sintering, the reinforcing phase and the ceramic framework form an interface bond through solid-phase diffusion, and construct a heterojunction interface or generate a new photocatalytic active phase through band matching, ultimately obtaining an integral foam ceramic with a three-dimensional framework composed of continuous photocatalytic functional phases and possessing both mechanical strength and visible light response capability.

2. The preparation method according to claim 1, characterized in that, In step S1, the average particle size of the WO3 powder is 10 nm-80 μm, and it is selected from any one or a combination of γ-WO3 (monoclinic phase, room temperature stable phase), β-WO3 (tetragonal phase), commercial WO3 powder or modified powder thereof; The WO3 modified powder is obtained by any of the following modification methods: 1) Cation doping, wherein the cation is selected from Li + Na + K + 、Rb + Cs + Mg² + Ca² + Sr² + Ba² + Al³ + Ga³ + In³ + Sn 4+ Sb³ + Sb 5+ Bi³ + ,Sc³ + Ti 4+ V³ + V 4+ V 5+ Cr³ + Cr 4+ Mn² + Mn³ + Mn 4+ Fe² + Fe³ + Co² + Co³ + Ni² + Ni³ + Cu² + Zn² + Y³ + Zr 4+ 、Nb 5+ Mo 6+ Ru 4+ 、Rh³ + Pd² + Ag + La³ + Ce³ + Ce 4+ Pr³ + Pr 4+ 、Nd³ + Sm³ + Eu³ + Gd³ + Tb³ + 、Tb 4+ Dy³ + Ho³ + Er³ + Tm³ + Yb³ + Lu³ + Hf 4+ Ta 5+ Re 4+ Re 6+ Os 4+ Ir 4+ Pt² + Pt 4+ and Au³ + Any one or more of the following, with a doping concentration of 0.1-15 at% 2) Anion doping, wherein the anion is selected from any one or more of B, C, N, F, P, S, Cl, Br and I, and the doping concentration is 0.5-10 at% 3) Oxygen vacancy regulation, with an oxygen vacancy concentration of 10. 18 -10 21 cm -3 ; 4) Defect engineering modification, dislocation / grain boundary density 10 14 -10 16 cm -2 ; The modified powder still possesses semiconductor properties, with a band gap ranging from 1.5 to 5.5 eV; The photocatalytic active component is an inorganic oxide powder with semiconductor properties, and its band gap ranges from 1.5 to 5.5 eV; it is selected from at least one component from the following I) - V); I) Single metal oxides The general chemical formula is M m O n M is a single metallic element, m = 1-3, n = 1-5; including one or more of TiO2, ZnO, Bi2O3, Fe2O3, Cu2O, V2O5, MoO3, SnO2, MnO2, ZrO2, Ga2O3, Nb2O5, Ta2O5, In2O3, GeO2, RuO2, IrO2, Co3O4, NiO, Mn3O4, CuO, Ag2O, CoO, MnO, SnO, Sb2O3, Fe3O4, and Au2O and their modified derivatives; II) Composite metal oxides Composed of two or more metal cations, and further subdivided according to crystal structure as: a) Perovskites and their derived phases: general formula ABO3 or A (n+1) B n O (3n+1) , where n is an integer from 1 to 3, A is selected from at least one of La, Bi, Ba, Sr, Ca, Pb, Na and K, and B is selected from at least one of Ti, Zr, Hf, Nb, Ta, W, Mo, V, Cr, Mn, Fe, Co, Ni, Al, Ga and Sn; b) Spinel-type oxides: with the general formula AB₂O₄, wherein A is selected from at least one of Mg, Zn, Ni, Co, Cu, Fe, Mn and Li, and B is selected from at least one of Al, Ga, Cr, Fe, Mn, Co and Ti; c) Layered oxyacid salts having a layered crystal structure with an interlayer spacing of 0.5 nm to 1.5 nm, selected from at least one of the following: c1) Layered titanates, with the general formula A2Ti3O7 or ATi2O5, wherein A is selected from H, Li, Na, K, Rb or Cs; C2) Protonated layered niobates or tantalates, with the general formula HNb3O8 or HTa2O6; C3) Aurivillius phase bismuth-based oxides, selected from Bi2WO6, Bi2MoO6, and Bi4Ti3O 12 At least one of them; c4) Layered nickelates, with the general formula ANiO2, wherein A is selected from Li or Na; d) Other functional oxoacid salts, selected from at least one of the following groups: d1) Scheelite-type oxides, with the general formula AWO4, AMoO4 or AVO4, wherein A is selected from Bi, Ca, Sr, Zn or Pb; d2) Perovskite-type rare earth ferrates, with the general formula LnFeO3, wherein Ln is selected from La, Pr, Nd or Sm; d3) Pyrochlore-type oxides, with the general formula Ln2B2O7, wherein Ln is selected from La, Gd, Sm or Nd, and B is selected from Ti, Zr or Sn; d4) Tungsten bronze type oxide, with the general formula M x TO3, where T is selected from W, Nb, or Ta, M is selected from Na or K, and 0.1 ≤ x ≤ 1.0; d5) Olivine-type oxides, with the general formula M2SiO4 or M2GeO4, wherein M is selected from Mg, Zn, Fe or Mn; d6) Inverse spinel-type stannate Zn2SnO4; d7) Copper-iron ore type oxides, with the general formula CuMO2, wherein M is selected from Fe, Al, Ga or Cr; III) Rare earth-based oxides a) Single rare earth oxide Ln a O x , where Ln is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, a = 1–2, x = 1.5–3; b) Rare earth composite oxides: including perovskite-type LaMO3, NdMO3, ScMO3, YMO3, PrMO3, SmMO3, EuMO3, GdMO3, TbMO3, DyMO3, HoMO3, ErMO3, TmMO3, YbMO3, and LuMO3, where M is selected from transition metals Fe, Co, Sc, Ti, V, Cr, Mn, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, and W. Re, Os, Ir, Pt, Au, or Hg; pyrochlore-type Gd₂Ti₂O₇, Y₂Zr₂O₇, Sc₂Ti₂O₇, La₂Ti₂O₇, Ce₂Ti₂O₇, Pr₂Ti₂O₇, Nd₂Ti₂O₇, Sm₂Ti₂O₇, Eu₂Ti₂O₇, Tb₂Ti₂O₇, Dy₂Ti₂O₇, Ho₂Ti₂O₇, Er₂Ti₂O₇, Tm₂Ti₂O₇, Yb₂Ti₂O₇, Lu₂Ti₂O₇; bismuth rare earth co-doped oxides Bi. 1-x Ln x VO4, wherein Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y, x = 0.1-0.5, and at least one of the layered rare earth oxides La2O2CO3, Pr4O7, Ce2O2CO3, Nd2O2CO3, Sm2O2CO3, Eu2O2CO3, Gd2O2CO3, Tb2O2CO3, Dy2O2CO3, Ho2O2CO3, Er2O2CO3, Tm2O2CO3, Yb2O2CO3, Lu2O2CO3, Sc2O2CO3, Y2O2CO3; the interlayer spacing of the layered rare earth oxide structure is 0.8-1.2 nm; IV) Frontier structural metal oxides a) High-entropy oxides: general formula is (M1, M2, ... M n ) a O M1, M2, ..., Mn are at least five different metallic elements, each independently selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mg, Al, Li, Zr, Nb, Mo, Sn, Hf, Ta, W, or Ce, with each metallic element accounting for 5% to 35% of the total metallic elements, and the configuration entropy ΔS of the high-entropy oxide is... mix ≥ 1.5R, where R is the ideal gas constant 8.314 J·mol - ¹·K - ¹; (b) A two-dimensional nano-metal oxide, wherein the matrix material of the two-dimensional nano-metal oxide is selected from at least one of TiO2, MnO2, MoO3, V2O5, Co3O4, Fe2O3, SnO2, ZnO and Nb2O5, has a plate-like or layered morphology, has a thickness of 0.5 nm to 10 nm, has a lateral dimension to thickness ratio ≥ 50, and the two-dimensional nano-metal oxide has preferentially exposed crystal planes, wherein the crystal planes are selected from at least one of the {001}, {010}, {100} and {110} plane families; c) MOF-derived porous oxides, wherein the MOF-derived porous oxides are obtained by heat treatment conversion of metal-organic framework precursors, wherein the metal center of the precursor is selected from at least one of Zn, Co, Fe, Cu, Zr, Ti, Ni and Al, and the resulting oxides retain the morphological characteristics and pore structure of the precursors, with a specific surface area ≥ 50 m² / g, pore volume ≥ 0.1 cm³ / g, and pore size distribution spanning from micropores to mesopores, ranging from 0.5 nm to 50 nm; V) Precursor compound: is the water-insoluble oxalate and / or carbonate corresponding to the metal oxides in I)-II), wherein the precursor compound decomposes in situ during sintering heat treatment to generate the corresponding photocatalytically active oxide; Wherein, "insoluble in water" means: solubility in deionized water at 25°C ≤ 0.1 g / 100 mL; the precursor compound must meet the following requirements: decomposition temperature between 200-1200°C, residual carbon content after decomposition < 0.1 wt.%, and no introduction of impurity anions harmful to photocatalytic activity; VI) The photocatalytic active component described in any of I) to IV) above is modified using one or more of the following methods, and the resulting powder satisfies a band gap of 1.5-5.5 eV: a) Cation doping, wherein the cation is selected from Li + Na + K + 、Rb + Cs + Mg² + Ca² + Sr² + Ba² + Al³ + Ga³ + In³ + Sn 4+ Sb³ + Sb 5+ Bi³ + ,Sc³ + Ti 4+ V³ + V 4+ V 5+ Cr³ + Cr 4+ Mn² + Mn³ + Mn 4+ Fe² + Fe³ + Co² + Co³ + Ni² + Ni³ + Cu² + Zn² + Y³ + Zr 4+ 、Nb 5+ Mo 6+ Ru 4+ 、Rh³ + Pd² + Ag + La³ + Ce³ + Ce 4+ Pr³ + Pr 4+ 、Nd³ + Sm³ + Eu³ + Gd³ + Tb³ + 、Tb 4+ Dy³ + Ho³ + Er³ + Tm³ + Yb³ + Lu³ + Hf 4+ Ta 5+ Re 4+ Re 6+ Os 4+ Ir 4+ Pt² + Pt 4+ and Au³ + At least one of them, with a doping ratio of 0.1-15 at%; b) Anion doping, wherein the anion is selected from one or more of B, C, N, F, P, S, Cl, Br and I, and the doping ratio is 0.5-10 at% c) Oxygen vacancy regulation, with an oxygen vacancy concentration of 10. 18 -10 21 cm -3 ; d) Defect engineering modification, dislocation / grain boundary density 10 14 -10 16 cm -2 ; The amount of the photocatalytic active component added is 5-80 wt.% of the tungsten trioxide powder mass. The amount of the precursor compound added is based on the theoretical mass of the corresponding photocatalytic active oxide generated by its complete thermal decomposition, i.e., oxide equivalent.

3. The preparation method according to claim 1, characterized in that, The sintering aid is selected from at least one of the following components: a) Low-melting-point oxides: bismuth trioxide, vanadium pentoxide, boron trioxide, molybdenum trioxide, tellurium dioxide, antimony trioxide, silver oxide; b) Eutectic oxides: copper oxide, nickel oxide, zinc oxide, iron oxide, tin oxide, cobalt oxide, manganese oxide, indium oxide, gallium oxide, titanium oxide, cadmium oxide, silver oxide, germanium oxide; c) Network forming agents: silicon dioxide, phosphorus pentoxide, germanium dioxide, tellurium dioxide, boron trioxide, vanadium pentoxide, antimony pentoxide, antimony trioxide; d) Network modifiers: magnesium oxide, calcium carbonate, lithium carbonate, barium carbonate, strontium carbonate; e) Presynthesized tungstates: bismuth tungstate, zinc tungstate, copper tungstate, calcium tungstate, strontium tungstate, barium tungstate, silver tungstate, manganese tungstate, iron tungstate, cobalt tungstate, nickel tungstate, indium tungstate, cerium tungstate, lanthanum tungstate, bismuth distungstate, bismuth niobium tungstate; f) Precursor compounds At least one of the water-insoluble oxalates, carbonates, and hydroxides corresponding to each component in a)-e) above decomposes in situ during degumming or sintering heat treatment to generate the corresponding oxides or oxygen-containing compounds; the precursor compounds are uniformly dispersed in the WO3 powder as solid particles in the slurry stage, and decompose in situ during heat treatment to generate nano-sized active powders, with better dispersion uniformity than directly adding oxides; "insoluble in water" means: solubility in deionized water at 25°C ≤0.1 g / 100mL; The amount of sintering aid added is 0.2-30 wt.% of the WO3 powder mass: for the sintering aids mentioned in a) to e), it is based on the actual added mass; for the sintering aids mentioned in f), it is based on the theoretical mass of the corresponding oxides generated by complete thermal decomposition, i.e., the oxide equivalent. The defect control agent is selected from at least one of the following components: i) Equivalent substitute stabilizers: molybdenum trioxide, rhenium heptaoxide, chromium trioxide, tellurium trioxide, antimony pentoxide; ii) Grain boundary segregation inhibitors: Lanthanum trioxide, yttrium oxide, scandium oxide, gadolinium oxide, cerium dioxide, samarium oxide, neodymium oxide, praseodymium oxide, europium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, indium oxide; iii) Grain boundary / lattice dual-effect stabilizers: zirconium dioxide, hafnium dioxide, tin dioxide, germanium dioxide, aluminum oxide, gallium oxide; iv) Oxygen activity self-regulating stabilizers: cerium dioxide, manganese oxides MnO2, Mn2O3, Mn3O4, cobalt oxides Co3O4, CoO; v) Precursor compounds The water-insoluble oxalates and / or carbonates corresponding to each component in i)-iv) above decompose in situ to generate corresponding oxides during the sintering heat treatment; wherein, the water-insoluble means: solubility in deionized water at 25℃ ≤0.1 g / 100mL; The total amount of the defect control agent added is 0.1-30 wt.% of the tungsten trioxide powder mass: for the defect control agents described in i)-iv), it is based on their actual added mass; for the precursor compounds described in v), it is based on the theoretical mass of the corresponding oxides generated by their complete thermal decomposition, i.e., the oxide equivalent.

4. The preparation method according to claim 1, characterized in that, In step S1, the organic additive includes at least one of binders, plasticizers, dispersants, surfactants, rheology modifiers, and defoamers; The organic additives are used alone or in combination, with a total addition amount of 0.1-30 wt.% of the total mass of tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents. The adhesive is selected from any one or more of polyethylene oxide, sodium alginate, chitosan, polyurethane emulsion, polyacrylamide, polyvinyl alcohol, methylcellulose, hydroxypropyl methylcellulose, ethylcellulose, polyethylene glycol, polyacrylic acid, polyvinyl acetate, starch and its derivatives; The plasticizer is selected from any one or more of the following: triethyl acetylglucosamine citrate, epoxidized soybean oil, polycaprolactone, glycerin, dibutyl phthalate, triethyl citrate, polyethylene glycol, sorbitol, and dioctyl sebacate. The dispersant is selected from any one or more of the following: polycarboxylate superdispersant, polymaleic anhydride, polyaspartic acid, ammonium polyacrylate, sodium polyacrylate, tetramethylammonium hydroxide, ammonium citrate, gum arabic, and polyvinylpyrrolidone. The surfactant is selected from any one or more of the following: sorbitan monooleate, cocamidopropyl betaine, perfluoropolyethers, sodium lauryl sulfate, hexadecyltrimethylammonium bromide, polysorbate 80, octylphenyl polyoxyethylene ether, lecithin, and fluorocarbon surfactants. The rheology modifier is selected from any one or more of guar gum, gellan gum, polyacrylic acid thickeners, organic modified montmorillonite, xanthan gum, sodium carboxymethyl cellulose, bentonite, fumed silica and polyacrylamide; The defoamer is selected from one or more of polydimethylsiloxane, polyether defoamer, isooctanol, n-octanol, silicone oil, polyether-modified siloxane, and mineral oil; The pH adjuster is at least one of ammonia and hydrochloric acid; The reinforcing phase is fibers and / or whiskers, selected from any one or more of the following: 1) Inorganic fibers: glass fiber, basalt fiber, silicon carbide fiber, alumina fiber, mullite fiber, quartz fiber, potassium titanate fiber; 2) Ceramic whiskers: silicon carbide whiskers, zinc oxide whiskers, calcium sulfate whiskers, silicon nitride whiskers, barium titanate whiskers, aluminum borate whiskers, magnesium borate whiskers, sodium titanate whiskers, potassium titanate whiskers, zirconium oxide whiskers, aluminum oxide whiskers, calcium carbonate whiskers. 3) Natural mineral fibers: sepiolite fiber, attapulgite fiber, wollastonite fiber, palygorskite fiber, tremolite fiber, actinolite fiber, vermiculite fiber, pyrophyllite fiber, sillimanite fiber, glauconite fiber, tourmaline fiber, palygorskite fiber; 4) Synthetic organic fibers: polyacrylonitrile fiber, polyvinyl alcohol fiber, aramid fiber, polyimide fiber; The reinforcing phase has an aspect ratio ≥ 10, a length of 1-500 μm, and a diameter of 0.1-50 μm. The solid content of the tungsten trioxide-based composite slurry is 20-70 vol.%, and the pH is 2-14. The amounts of organic additives and reinforcing phases added are based on the total mass of tungsten trioxide powder, photocatalytic active components, sintering aids, and defect control agents, and are as follows: Adhesive 1-20 wt.%; Dispersant 0.1-5 wt.%; Plasticizer 0.1-10 wt.%; Surfactant 0.01-5 wt.%; Rheology modifier 0.1-10 wt.%; Defoamer 0.05-10 wt.%; pH adjuster 0.01-10 wt.%; Reinforcing phase: 0.01-30 wt.% of fibers or 0.01-50 wt.% of whiskers.

5. The preparation method according to claim 1, characterized in that, In step S2, the organic foam is made of polyurethane, melamine formaldehyde, or polystyrene; the pore density of the organic foam ranges from 6 to 70 PPI, and its macroscopic shape is any one of the following: cylinder, cube, cuboid, sphere, ellipsoid, torus, prism, pyramid, polyhedron, honeycomb block, sheet, arc, arch, tubular, hollow spherical shell, or any combination or deformation thereof. The impregnation is carried out using normal pressure, negative pressure assisted, or alternating negative and normal pressure methods; the impregnation process is carried out at 25±20℃, the normal pressure impregnation time is 30-1800 seconds, and the number of negative and normal pressure alternating impregnations is 1-5 times per impregnation cycle; The negative pressure assistance involves completely immersing the organic foam in the tungsten trioxide-based composite slurry described in step S1, then evacuating the composite slurry to boiling point within 3 minutes, maintaining boiling for 0.5-10 minutes to ensure that all air in the system is expelled, and then restoring it to ambient pressure. The pressure of the extrusion desizing is controlled at 0.05-5.0 MPa, and the thickness of the organic foam after extrusion is compressed to 30-95% of the original thickness; the centrifugal desizing speed is 500-2000 rpm, and the centrifugation time is 10-600 seconds; The drying process employs a programmed temperature increase method, with a temperature range of 20~95℃ and a relative humidity decreasing from ≥70% to <10%, drying until the mass change rate is <20% / h. After each impregnation-desizing-drying cycle, the mass gain rate of the composite slurry loaded in the organic foam is 50-500%. After 2-5 cycles, the cumulative loading of the composite slurry reaches 150-1000% of the original mass of the organic foam, forming a coating thickness of 0.1-3.0 mm, a coating thickness variation coefficient of <30%, and a pore blockage rate of <40%.

6. The preparation method according to claim 1, characterized in that, In step S3, the natural air drying is carried out in a ventilated environment with a temperature of 5-45℃, a relative humidity of 30-90%, a ventilation rate of 0.1-10.0 m / s, and a natural air drying time of 2-24 hours. The heating program for the drying process is as follows: the temperature is increased from room temperature to 50-95℃ at a rate of 0.01-10.00℃ / min, and the temperature is maintained for 4-8 hours. The airflow rate inside the oven is 0.01-10.00 m / s, and the drying endpoint is a mass change rate of <0.1% / h. The degumming heat treatment includes: The first stage involves raising the temperature at a rate of 1-10℃ / min to 150-250℃ and holding it for 1-360 min. In the second stage, the temperature is increased to 350-450℃ at a rate of 0.5-10℃ / min, and then held for 1-360 min. The third stage involves raising the temperature at a rate of 0.5-10℃ / min to 550-600℃ and holding it for 1-360 min. The degumming heat treatment process is carried out under vacuum or atmospheric conditions. The vacuum conditions are: no gas is introduced and the absolute pressure inside the furnace is maintained below 100 Pa. The atmospheric conditions are: at least one of helium, argon, nitrogen, ammonia, air and oxygen is introduced, the gas flow rate is 0-9000 mL / min, and the pressure inside the furnace is maintained at gauge pressure +50 to +9000 Pa.

7. The preparation method according to claim 1, characterized in that, In step S4, the controlled sintering heat treatment temperature is 800-1200℃, the heating rate is 2-20℃ / min, and the holding time is 0.01-24 hours; The controlled sintering heat treatment is carried out under vacuum or atmospheric conditions. The vacuum conditions are: no gas is introduced and the absolute pressure inside the furnace is maintained below 10 Pa. The atmospheric conditions are: at least one of hydrogen, helium, argon, nitrogen, ammonia, air and oxygen is introduced, the gas flow rate is 0-9000 mL / min, and the pressure inside the furnace is maintained at gauge pressure +50 to +9000 Pa.

8. The monolithic tungsten trioxide-based photocatalytic foam ceramic obtained by the preparation method according to any one of claims 1 to 7.

9. The monolithic tungsten trioxide-based photocatalytic foam ceramic prepared by the preparation method according to any one of claims 1 to 7 is used in i) the degradation of organic pollutants or water treatment; ii) in the preparation of an apparatus for degrading organic pollutants or a water treatment apparatus.

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