Porous ceramic for purifying indoor volatile organic compounds and preparation method thereof

Abstract

The invention relates to porous ceramic for purifying indoor volatile organic compounds and a preparation method of the porous ceramic, and belongs to the technical field of environmental protection. The porous ceramic disclosed by the invention comprises a porous ceramic matrix, wherein a photocatalytic coating is loaded on the porous ceramic matrix; a photocatalyst used by the photocatalytic coating is prepared by a method comprising the following steps: mixing BPQDs, amino-modified GQDs, nitrogen-phosphorus co-doped g-C3N4, nano CoO and BiVO4 sol, drying and then roasting. The preparation method comprises the following steps: mixing the BPQDs, the amino-modified GQDs, the nitrogen-phosphorus co-doped g-C3N4, the nano CoO and the BiVO4 sol; the porous ceramic effectively combines the adsorption-reaction type composite coating and the photocatalysis type coating, harmful gases such as formaldehyde can be quickly adsorbed through the photocatalysis type coating in the initial decoration stage, a small amount of indoor formaldehyde can be adsorbed and decomposed through the adsorption-reaction type composite coating in the later stage, adsorption and decomposition of the adsorption-reaction type composite coating are carried out at the same time, and the decoration effect is good. The efficiency of absorbing and decomposing gases such as formaldehyde is higher, and the action time is longer.

Description

Technical Field

[0001] This invention relates to a porous ceramic for purifying indoor volatile organic compounds and its preparation method, belonging to the field of environmental protection technology. Background Technology

[0002] With the increasing airtightness of modern buildings and the growing complexity of interior decoration, volatile organic compounds (VOCs) such as formaldehyde, benzene, and toluene have become significant environmental problems threatening human health. Among them, formaldehyde, as the most important and representative volatile organic pollutant in indoor air, has attracted much attention due to its wide range of sources, long release period, and significant health hazards.

[0003] Formaldehyde is more troublesome than other volatile organic compounds, mainly for the following reasons: (1) Continuous and long-term low-concentration release: Formaldehyde mainly comes from unreacted components in decoration materials such as urea-formaldehyde resin, and its release cycle can be as long as 3-15 years. This "slow release" specificity leads to a long-term presence of low concentrations (usually 0.01~0.5 mg / m³) indoors. 3 (1) Formaldehyde pollution places extremely high demands on the durability of purification technologies. (2) Strong polarity and high reactivity: Formaldehyde molecules are small and highly water-soluble (high polarity), resulting in low adsorption capacity and easy desorption of traditional adsorbents (such as ordinary activated carbon). At the same time, the high reactivity of formaldehyde also means that intermediate by-products are easily generated during the purification process, which may cause secondary pollution. (3) Low health risk threshold: The World Health Organization has listed formaldehyde as a Group 1 carcinogen, even if the concentration is lower than the international limit (0.08 mg / m³). 3 Long-term exposure may still damage the respiratory tract, immune system and genetic material, requiring purification technology to have deep purification capabilities.

[0004] Several purification technologies have been developed to address the physicochemical properties of formaldehyde. Adsorption methods utilize porous materials to capture formaldehyde molecules through physical or chemical processes. Ordinary physical adsorption (e.g., activated carbon) uses widely available and low-cost raw materials, but suffers from weak formaldehyde adsorption capacity, easy saturation, significant dependence on ambient temperature and humidity, and the potential for reverse release after saturation. Chemically modified adsorption modifies adsorbents (e.g., activated carbon, molecular sieves) by altering their functional groups (amine, acid, etc.) to enhance formaldehyde capture and fixation through chemical reactions; however, it still suffers from limited adsorption capacity. Catalytic oxidation involves the reaction of formaldehyde with oxygen in the air at room temperature or low temperature under the action of a catalyst, resulting in its complete oxidation into carbon dioxide and water. This is currently recognized as the most thorough and promising formaldehyde purification technology. However, precious metal catalysts (such as Pt, Pd, and Au) are expensive and prone to deactivation due to poisoning by carbon dioxide, water vapor, or other volatile organic compounds in the room. While metal oxide catalysts (MnO2 and TiO2) are lower in cost and more environmentally friendly, they suffer from lower activity and stability. Photocatalytic oxidation uses visible light to drive a photocatalyst, generating highly oxidizing free radicals to degrade formaldehyde. It is effective in degrading formaldehyde, but incomplete oxidation can lead to the formation of intermediate products, causing secondary pollution. Furthermore, these intermediate products can occupy the active sites of the catalyst, causing rapid deactivation. Therefore, the development of efficient and stable formaldehyde purification materials has become a research hotspot.

[0005] Porous ceramic materials, with their unique physical and chemical properties, show great promise as catalyst carriers and adsorption matrices in the field of indoor formaldehyde purification. Although porous ceramic materials themselves have limited physical adsorption capacity for formaldehyde, they can serve as excellent carriers for functional components (such as catalysts and adsorbents), achieving synergistic purification through composite technology.

[0006] Chinese invention patent application CN119345991A, published on January 24, 2025, discloses a porous ceramic membrane catalyst and its preparation system. Specifically, it discloses that the preparation of ceramic membrane is optimized by an eccentric wheel mixing system, but it does not integrate photocatalytic function and still relies on physical adsorption. Loading nanoparticles such as Ag and ZnO can enhance light absorption, but it is costly and has poor stability.

[0007] Chinese invention patent application CN120643978A, published on September 16, 2025, discloses a porous ceramic core supported on a nanocomposite catalyst and its preparation method. Specifically, the porous ceramic core comprises a porous ceramic matrix, a nanocomposite catalyst layer, and a surface functionalized layer. The nanocomposite catalyst layer is composed of g-C3N4 / TiO2 / Ag3PO4 nanoparticles loaded on the surface and within the pores of the porous ceramic matrix. The surface functionalized layer is formed by silver nanoparticles modified on the surface of the catalyst layer. Through hierarchical pore structure design and heterojunction bandgap modulation, a synergistic effect of efficient photocatalytic degradation and pollutant adsorption is achieved, resulting in high degradation rates for pollutants such as formaldehyde and benzene. It exhibits good adsorption, photocatalytic, and antibacterial properties. However, it suffers from high cost and the need to improve the formaldehyde removal rate. Summary of the Invention

[0008] The first objective of this invention is to provide a porous ceramic for purifying indoor volatile organic compounds, thereby addressing the problem that the formaldehyde removal rate of existing porous ceramic-based products used for purifying formaldehyde needs to be improved.

[0009] The second objective of this invention is to provide a method for preparing porous ceramics that purify indoor volatile organic compounds, and to provide porous ceramics with high formaldehyde removal rate and long service life.

[0010] To achieve the above objectives, the technical solution of this invention for a porous ceramic material for purifying indoor volatile organic compounds is as follows: A porous ceramic for purifying indoor volatile organic compounds includes a porous ceramic matrix on which a photocatalytic coating is loaded. The photocatalyst used in the photocatalytic coating is prepared by a method comprising the following steps: mixing BPQDs, amino-modified GQDs, nitrogen-phosphorus co-doped g-C3N4, nano-CoO and BiVO4 sol, drying and then calcining. The mass ratio of BPQDs, amino-modified GQDs, nitrogen-phosphorus co-doped g-C3N4, nano-CoO and BiVO4 sol is (2.25-5):(0.75-1.7):(80-120):(3-8):(80-120).

[0011] The beneficial effects of the above technical solution are as follows: This invention, a porous ceramic for purifying indoor volatile organic compounds, is a pioneering invention. Through a multi-level pore design and the loading of a photocatalytic coating, this invention achieves the synergistic function of formaldehyde adsorption and catalysis, overcoming the shortcomings of existing air purification materials in terms of systematic adsorption and catalysis, effectively improving the formaldehyde removal rate. Furthermore, the design of the BPQDs / GQDs / CoO / BiVO4 / g-C3N4 composite photocatalyst material gives the porous ceramic of this invention outstanding durability. The porous ceramic of this invention exhibits excellent comprehensive performance in the field of air purification, can be reused, significantly reduces usage costs, and has good prospects for practical application.

[0012] Preferably, the concentration of the BiVO4 sol is 5~5.5 wt%.

[0013] As a further improvement, the mixing includes: mixing a BPQDs solution, an amino-modified GQDs solution, and a silane coupling agent to obtain a BPQDs / GQDs composite solution; dispersing nano-CoO and nitrogen-phosphorus co-doped g-C3N4 in water, and then mixing it with BiVO4 sol to form a g-C3N4-CoO-BiVO4 pre-composite system; mixing the g-C3N4-CoO-BiVO4 pre-composite system with the BPQDs / GQDs composite solution; in the pre-composite system, the mass ratio of nano-CoO, nitrogen-phosphorus co-doped C3N4, BiVO4 sol, and water is (0.03-0.08):(0.8-1.2):(0.8-1.2):(8-12); the mass ratio of the total number of quantum dots in the pre-composite system to the BPQDs / GQDs composite solution is 100:(0.3-0.6).

[0014] Preferably, in the pre-composite system, the mass ratio of nano-CoO, nitrogen-phosphorus co-doped C3N4, BiVO4 sol, and water is (0.05-0.08):(1-1.2):(1-1.2):(10:12); the mass ratio of the total number of sub-dots in the pre-composite system to the BPQDs / GQDs composite solution is 100:(0.4-0.6). More preferably, in the pre-composite system, the mass ratio of nano-CoO, nitrogen-phosphorus co-doped C3N4, BiVO4 sol, and water is 0.05:1:1:10; the mass ratio of the total number of sub-dots in the pre-composite system to the BPQDs / GQDs composite solution is 100:0.4.

[0015] As a further improvement, the preparation of the BiVO4 sol includes: dissolving bismuth nitrate, citric acid, and ammonium metavanadate in water, then adjusting the pH of the mixed solution to 3-3.5, and mixing to obtain BiVO4 sol; the molar ratio of bismuth nitrate, citric acid, and ammonium metavanadate is 1:(1.5-2.5):(0.95-1.05); the mass ratio of citric acid to water is 1.92:(18-25); and the pH of the mixed solution is adjusted using ammonia water; the preparation of the nitrogen-phosphorus co-doped g-C3N4 includes: calcining melamine and ammonium dihydrogen phosphate at 500-550℃, and cooling to obtain nitrogen-phosphorus co-doped g-C3N4; the mass ratio of melamine to ammonium dihydrogen phosphate is 10:(1.2-2); and the calcination time is (3-3.5) h.

[0016] Preferably, the molar ratio of bismuth nitrate, citric acid, and ammonium metavanadate is 1:(1.5-2):(1-1.05); the mass ratio of citric acid to water is 1.92:(18-20); and the mass ratio of melamine to ammonium dihydrogen phosphate is 10:(1.2-1.5). More preferably, the molar ratio of bismuth nitrate, citric acid, and ammonium metavanadate is 1:2:1; the mass ratio of citric acid to water is 1.92:20; and the mass ratio of melamine to ammonium dihydrogen phosphate is 10:1.5.

[0017] As a further improvement, the mass concentration of BPQDs in the BPQDs solution is (0.3-0.8) mg / mL, and the particle size is 2-5 nm; the mass concentration of amino-modified GQDs in the amino-modified GQDs solution is (0.3-0.8) mg / mL, and the particle size is 2-3 nm; the calcination temperature is 400-450℃, and the time is (2-2.5) h.

[0018] Preferably, the BPQDs solution contains 0.5-0.8 mg / mL of BPQDs and has a particle size of 2-5 nm; the amino-modified GQDs solution contains 0.5-0.8 mg / mL of amino-modified GQDs and has a particle size of 2-3 nm. More preferably, the BPQDs solution contains 0.5 mg / mL of BPQDs and has a particle size of 2-5 nm; the amino-modified GQDs solution contains 0.5 mg / mL of amino-modified GQDs and has a particle size of 2-3 nm.

[0019] Preferably, the roasting temperature is 400-420℃ and the time is (2~2.5) h. More preferably, the roasting temperature is 420℃ and the time is 2 h.

[0020] As a further improvement, the photocatalytic coating is mainly composed of silica sol, modified lithium-based silicate, fumed silica, nano-TiO2, and the photocatalyst; the thickness of the photocatalytic coating is 5-10 μm; the porous ceramic matrix is ​​mainly composed of alumina, calcium carbonate, hollow glass microspheres, dispersant, and curing agent mixed together, then cured and sintered; the porosity of the porous ceramic matrix is ​​≥85%.

[0021] Among them, fumed silica has a large specific surface area, forming a three-dimensional network structure in the base material, which improves the viscosity stability and thixotropy of the coating. Nano titanium dioxide itself has photocatalytic activity, and works synergistically with BPQDs / GQDs / CoO / BiVO4 / g-C3N4 to broaden the light absorption range and improve the formaldehyde degradation efficiency; in addition, nano titanium dioxide has the ability to shield ultraviolet rays, preventing the aging and degradation of the base material and improving the weather resistance of the coating.

[0022] Preferably, the volume-to-mass ratio of the silica sol, modified lithium-based silicate, fumed silica, nano-TiO2, and photocatalyst is (90-100) mL:(30-35) mL:(4-5) g:(3-3.5) g:(5-8) g. More preferably, the volume-to-mass ratio of the silica sol, modified lithium-based silicate, fumed silica, nano-TiO2, and photocatalyst is 100 mL:30 mL:5 g:3 g:(5-8) g. As a further improvement, an adsorption-reaction composite coating is first loaded onto the surface and pores of the porous ceramic substrate, and then the photocatalytic coating is loaded onto the surface of the adsorption-reaction composite coating. The adsorption-reaction composite coating mainly comprises MIL-88B(Fe)-NH2 and physical adsorption materials; the loading amount of the adsorption-reaction composite coating in the porous ceramic substrate is 5-10%.

[0023] Preferably, the mass ratio of the alumina, calcium carbonate, hollow glass microspheres, dispersant and curing agent is (85-90):(14-16):(40-45):(1-1.1):(5-6).

[0024] Preferably, the modified lithium-based silicate is prepared by reacting lithium silicate with methyltrimethoxysilane; the volume ratio of lithium silicate to methyltrimethoxysilane is 80:(7-10); the reaction temperature is 55-60°C; and the reaction time is 2-3 hours. More preferably, the reaction includes first diluting the lithium silicate with water to adjust the pH to 9-10, then adding a methyltrimethoxysilane solution to react, and finally adjusting the pH to 9-10 after the reaction to obtain a solution. The solution obtained from the reaction can be used directly without further treatment.

[0025] As a further improvement, the adsorption-reaction composite coating is mainly composed of silica sol, modified lithium-based silicate, nano-SiO2, the MIL-88B(Fe)-NH2, and physical adsorption materials; the physical adsorption materials are one, two, or more of the following: biochar, activated carbon, bamboo charcoal, zeolite powder, tourmaline powder, diatomaceous earth, vermiculite, shell powder, modified clay, and modified cellulose.

[0026] Preferably, the volume-to-mass ratio of the silica sol, modified lithium-based silicate, nano-SiO2, MIL-88B(Fe)-NH2, and physical adsorption material is (90-100) mL:(40-45) mL:(4-5) g:(10-12) g:(4-5) g. More preferably, the volume-to-mass ratio of the silica sol, modified lithium-based silicate, nano-SiO2, MIL-88B(Fe)-NH2, and physical adsorption material is 100 mL:40 mL:5 g:10 g:5 g.

[0027] As a further improvement, the dispersant is one, two, or more of the following: ammonium polyacrylate, tartaric acid, glutaraldehyde, ammonium citrate, sodium citrate, and polyethyleneimine; the curing agent is one, two, or more of the following: SecZ, propylene oxide glycerol ether, hydroxypropyl methylcellulose, N,N'-methylenebisacrylamide, ethyl acetate, and polyvinyl alcohol.

[0028] To achieve the above objectives, the technical solution of the present invention for preparing porous ceramics for purifying indoor volatile organic compounds is as follows: A method for preparing a porous ceramic for purifying indoor volatile organic compounds includes the following steps: vacuum impregnating a porous ceramic matrix in an adsorption-reaction composite coating containing MIL-88B(Fe)-NH2 as the active ingredient and a physical adsorption material, curing it by heating to form a coating, and then coating the surface of the coating with a photocatalytic coating containing the photocatalyst as the active ingredient.

[0029] The beneficial effects of the above technical solution are as follows: This invention utilizes vacuum negative pressure and coating to combine two coatings onto a porous ceramic substrate. The process is clear and controllable, simple to operate, and easy to scale up for production. The parameters of each step are rationally designed, which can effectively ensure the consistency of product quality and performance, and is conducive to the large-scale promotion and application of this porous ceramic core.

[0030] As a further improvement, the vacuum impregnation pressure is -0.06 to -0.08 MPa, and the holding time is 30-45 min; the curing includes first holding at 60-70℃ for 2 h; and then holding at 120-150℃ for 3 h. Attached Figure Description

[0031] Figure 1The porous ceramic prepared in Example 1 of this invention is used to purify indoor volatile organic compounds. Figure 2 This is a schematic diagram of the reaction apparatus used in Experimental Example 1 of the present invention (wherein, 1-closed glass reactor, 2-gas inlet, 3-gas outlet, 4-sampling port, 5-temperature sensor port, 6-porous ceramic, 7-quartz reactor). Detailed Implementation

[0032] Volatile organic compounds (VOCs) such as formaldehyde, benzene, and toluene in indoor air are major pollutants affecting human health. Formaldehyde, in particular, is widely sourced (from furniture, building materials, textiles, etc.), has a long release period, and is highly toxic; therefore, it is classified as a Group 1 carcinogen by the World Health Organization, making its efficient removal a core challenge in the field of air purification. Porous ceramics, due to their high porosity, large specific surface area, good chemical stability, and high-temperature resistance, have been widely used in filtration, adsorption, catalysis, and insulation. With increasingly stringent requirements for indoor air quality, porous ceramic materials with air purification functions have become a research hotspot. However, existing porous ceramic materials suffer from high costs and relatively low formaldehyde removal rates.

[0033] Based on this, the present invention provides a porous ceramic material for purifying indoor volatile organic compounds and its preparation method. The present invention uses a calcium hexaaluminate-based porous ceramic material with high porosity as the matrix, effectively combining an adsorption-reaction composite coating and a photocatalytic coating. In the early stages of renovation, the photocatalytic coating can quickly adsorb harmful gases such as formaldehyde. Later, small amounts of formaldehyde in the room can be adsorbed and decomposed by the adsorption-reaction composite coating. The adsorption and decomposition of the adsorption-reaction composite coating occur simultaneously, requiring only one application. There is no longer a distinction between the adsorption layer and the reaction decomposition layer, resulting in higher efficiency and longer duration of action for absorbing and decomposing formaldehyde and other gases.

[0034] Specifically, the porous ceramic of the present invention includes a porous ceramic matrix, an adsorption-reaction composite coating loaded on the surface and pores of the porous ceramic matrix, and a photocatalytic coating loaded on the adsorption-reaction composite coating on the surface of the porous ceramic matrix; the adsorption-reaction composite coating mainly includes MIL-88B(Fe)-NH2 and physical adsorption materials; the photocatalytic coating mainly includes BPQDs / GQDs / CoO / BiVO4 / g-C3N4 composite photocatalyst material; the open porosity of the porous ceramic matrix is ​​≥85%; the loading of the adsorption-reaction composite coating in the porous ceramic matrix is ​​5-10%; and the thickness of the photocatalytic coating is 5-10 μm.

[0035] As a further improvement, the preparation process of MIL-88B(Fe)-NH2 includes the following steps: (1) The trivalent soluble iron salt reacts with 2-aminoterephthalic acid in an organic solvent; (2) The reactants obtained in step (1), ferrocene derivatives, and acetic acid are reacted in an organic solvent under the protection of an inert gas to obtain the product.

[0036] As a further improvement, the molar ratio of the trivalent soluble iron salt and 2-aminoterephthalic acid in step (1) is (1~1.1):(1~1.1); the reaction is carried out at 150-160℃ for (12-14) h.

[0037] As a further improvement, the mass-volume ratio of the reactants, ferrocene derivatives and acetic acid in step (2) is (0.5-0.6) g: (0.25-0.3) g: (1-1.2) mL; the reaction is carried out at 95-100 °C for (8-10) h.

[0038] As a further improvement, the preparation process of the BPQDs / GQDs / CoO / BiVO4 / g-C3N4 composite photocatalyst material includes the following steps: (1) Melamine and ammonium dihydrogen phosphate were calcined at 550°C and cooled to obtain nitrogen-phosphorus co-doped g-C3N4; (2) Dissolve bismuth nitrate, citric acid and ammonium metavanadate in water, then adjust the pH of the mixed solution to 3-3.5, and mix to obtain BiVO4 sol; (3) Disperse nano-CoO in water, add nitrogen-phosphorus co-doped g-C3N4 obtained in step (1) and disperse evenly, then mix with BiVO4 sol obtained in step (2) to form g-C3N4-CoO-BiVO4 precomposite system; (4) Black phosphorus is sonicated in an organic solution to separate solid and liquid and obtain BPQDs solution; the pH of citric acid aqueous solution is adjusted to 7.0-7.5 by ethylenediamine and hydrothermal reaction is carried out to obtain amino-modified GQDs solution; BPQDs solution and amino-modified GQDs solution are mixed with silane coupling agent by sonication to obtain BPQDs / GQDs composite solution. (5) The g-C3N4-CoO-BiVO4 precomposite system obtained in step (3) and the BPQDs / GQDs composite solution obtained in step (4) are mixed and adsorbed in a solvent, dried and then calcined at 400-450℃.

[0039] As a further improvement, the mass ratio of melamine to ammonium dihydrogen phosphate in step (1) is 10:(1.2-2); the temperature is increased to 500-550℃ at 5℃ / min; and the calcination time is (3~3.5)h.

[0040] As a further improvement, the molar ratio of bismuth nitrate, citric acid, and ammonium metavanadate in step (2) is 1:(1.5-2.5):(0.95-1.05); the mass ratio of citric acid to water is 1.92:(18-25); and the pH of the mixed solution is adjusted using ammonia.

[0041] As a further improvement, the mass ratio of nano-CoO, nitrogen-phosphorus co-doped g-C3N4, BiVO4 sol and water in step (3) is (0.03-0.08):(0.8-1.2):(0.8-1.2):(8-12); when dispersing nano-CoO in water, a dispersant is added.

[0042] As a further improvement, in step (4), the mass concentration of BPQDs in the BPQDs solution is (0.3-0.8) mg / mL, and the particle size is 2-5 nm; the mass concentration of amino-modified GQDs in the amino-modified GQDs solution is (0.3-0.8) mg / mL, and the particle size is 2-3 nm; the mass ratio of BPQDs solution to amino-modified GQDs solution in the BPQDs / GQDs composite solution is 3:1.

[0043] As a further improvement, in step (5), the mass ratio of the total number of quantum dots in the g-C3N4-CoO-BiVO4 precomposite system to the BPQDs / GQDs composite solution is 100:(0.3-0.6); the temperature is increased to 400-450℃ at 2℃ / min; and the calcination time is (2~2.5)h.

[0044] As a further improvement, the physical adsorption material is one, two, or more of the following: biochar, activated carbon, bamboo charcoal, zeolite powder, tourmaline powder, diatomaceous earth, vermiculite, shell powder, modified clay, and modified cellulose.

[0045] As a further improvement, the porous ceramic matrix is ​​mainly composed of alumina, calcium carbonate, hollow glass microspheres, dispersant and curing agent, which are mixed, cured and sintered.

[0046] As a further improvement, the dispersant is one, two, or more of the following: ammonium polyacrylate, tartaric acid, glutaraldehyde, ammonium citrate, sodium citrate, and polyethyleneimine; the curing agent is one, two, or more of the following: SecZ, propylene oxide glycerol ether, hydroxypropyl methylcellulose, N,N'-methylenebisacrylamide, ethyl acetate, and polyvinyl alcohol.

[0047] The adsorption-reaction composite coating mainly consists of MIL-88B(Fe)-NH2 and physical adsorption materials. Its adsorption-reaction mechanism is as follows: (1) Adsorption and enrichment: Physical adsorbent materials possess a large specific surface area. Furthermore, the ultra-large specific surface area and pores of the MIL-88B(Fe) matrix provide diffusion and sieving space for VOCs. Amino groups (-NH2) react with Fe through acid-base neutralization and π-π stacking. 3+ Through synergistic action, VOCs are targeted, captured, and enriched around the active site.

[0048] (2) Catalytic activation: Fe 3+ Under the electronic regulation of amino groups, they are more easily reduced to Fe. 2+ Through a Fenton-like reaction, active substances such as •OH are continuously generated, while the amino group simultaneously lowers the activation energy of VOCs bonds, which helps the catalytic reaction to occur.

[0049] (3) Oxidative mineralization: Active substances attack VOCs activated by amino groups, preferentially breaking weak bonds (such as methyl groups in benzene series), avoiding toxic intermediates, and ultimately converting them into CO2 and H2O. The amino group reacts with Fe... 3+ / Fe 2+ It participates in the reaction in a cyclical manner.

[0050] Photocatalytic coatings mainly include BPQDs / GQDs / CoO / BiVO4 / g-C3N4 composite photocatalyst materials, and their photocatalytic mechanism is as follows: (1) Photoabsorption excitation: In the system, g-C3N4 and BiVO4 absorb visible light, CoO absorbs near-infrared light, and BPQDs / GQDs cover the ultraviolet-visible light. The multi-component components synergistically capture photons, exciting the valence band electrons of each component to transition to the conduction band, generating photogenerated electrons (e electrons). - )-hole (h + )right.

[0051] (2) Charge separation and migration: relying on the stepped energy band of the Z-type / II-type heterojunction, e - Directional conduction to the surface via GQDs, h + Residing at the oxidation end such as CoO, BPQDs and Co 2+ / Co 3+ Redox inhibits carrier recombination and prolongs charge lifetime (Type II heterojunctions mainly form between g-C3N4 and BiVO4, while the core of Z-type heterojunctions forms between BiVO4 and CoO; the two together construct the "reduction end" (g-C3N4, producing O2). - The complete charge transport chain, from BiVO4 (connecting type II and type Z) to the oxidation terminal (CoO, producing •OH), achieves both full-spectrum response and ensures •O2 production. - The efficient generation of two core active species, α and β, ultimately enhances the mineralization efficiency of VOCs.

[0052] (3) Generation of active species: e -It reacts with adsorbed O2 to generate •O2 - h + with H2O / OH - The reaction produces •OH, and some h + It directly participates in oxidation, forming a library of highly reactive oxidizing species.

[0053] (4) VOCs mineralization: •O2 - Initially, weak bonds in VOCs (such as toluene methyl) are attacked, and •OH further breaks the bonds (such as benzene ring opening). BPQDs / GQDs adsorb and enrich VOCs to improve reaction efficiency, and finally the VOCs are gradually oxidized to CO2 and H2O.

[0054] The roles of each component in the BPQDs / GQDs / CoO / BiVO4 / g-C3N4 composite photocatalyst material are as follows: BPQDs (black phosphorus quantum dots): On the one hand, they broaden the light absorption range (covering 400-800nm) through the quantum confinement effect, enhancing the capture of visible light; on the other hand, their surface defects can adsorb VOCs molecules, while simultaneously acting as hole traps to retain highly oxidizing holes (h). + It promotes the formation of •OH and enhances the oxidation capacity of VOCs.

[0055] GQDs (graphene quantum dots): act as "electron highways," accelerating photogenerated electrons (electrons) through their high conductivity. - The directional migration of ions reduces recombination with holes; at the same time, its excellent light transmittance does not block light absorption, and it can also assist in the adsorption of benzene VOCs through π-π stacking, thereby increasing the local pollutant concentration.

[0056] CoO: As a "near-infrared responsive unit and oxidation enhancer," its narrow bandgap (≈1.2 eV) allows it to absorb near-infrared light (520-1000 nm), expanding the range of light utilization; its valence band hole (2.0 eV) has strong oxidation ability, directly generating •OH, and Co... 2+ / Co 3+ Redox pairs can capture electrons and release them slowly, extending charge lifetime.

[0057] BiVO4 (bismuth vanadate): As a "visible light response core and charge bridge", it absorbs visible light (λ<520nm) to generate charge carriers. Its band positions (conduction band 0.3eV, valence band 2.4eV) match g-C3N4 and CoO. In the Z-type heterojunction, it plays the role of an "intermediate transport layer" to guide the directional flow of charge.

[0058] g-C3N4 (graphitic carbon nitride): Serving as the "reduction end core and structural framework," it absorbs visible light (λ<460nm) to generate strongly reducing electrons (conduction band -1.3eV), which is the precursor for O2.- It generates an electron source; at the same time, its layered structure has high stability, providing support for the entire system and ensuring the integrity of the heterojunction structure.

[0059] The present invention will now be further described in conjunction with specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. The equipment and raw materials used are all commercially available or commonly used in the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0060] The hollow glass microspheres used in the following examples are HL38 from Zhengzhou Shenglait Hollow Microsphere New Material Co., Ltd.

[0061] Specific embodiments of the porous ceramic for purifying indoor volatile organic compounds and its preparation method according to the present invention: Example 1 The specific preparation process of the porous ceramic for purifying indoor volatile organic compounds in this embodiment is as follows: 1. Preparation of calcium hexaaluminate-based porous ceramic materials: Weigh 85.62g of alumina (45-65μm) and 14.38g of calcium carbonate (10-18μm), and dry mix them in a ball mill jar for 60 minutes to ensure uniform mixing. Add 1g of ammonium polyacrylate, 5g of SECURITY Z, and 35g of deionized water to the dry-mixed powder, and continue wet mixing for 60 minutes to form a uniform slurry. Add 40g of hollow glass microspheres to the slurry (during the subsequent sintering process, the shell material of the hollow glass microspheres participates in the solid-phase reaction, while the air in the hollow parts remains unchanged, becoming pores in the matrix), and stir at low speed for 20 minutes to uniformly disperse the microspheres in the slurry. Pour the mixed slurry into a mold (200×200×10mm). 3 The surface was smoothed with a scraper and allowed to stand at room temperature for 24 hours for initial curing. It was then placed in an oven and dried at 95°C for 24 hours to remove moisture. Finally, it was transferred to a muffle furnace and heated to 1500°C at a rate of 3°C / min, held for 3 hours, and allowed to cool naturally to room temperature to obtain a calcium hexaaluminate-based porous ceramic material (open porosity ≥85%).

[0062] 2. Preparation of MIL-88B(Fe)-NH2: Take 2 mol of ferric chloride and 1 mol of 2-aminoterephthalic acid, add them to 100 mL of DMF (N,N-dimethylformamide), and sonicate for 20 minutes to ensure complete dissolution. Then add 1.5 mol of sodium hydroxide (to adjust the pH of the solution to be alkaline and inhibit Fe). 3+ Hydrolysis ensures Fe 3+The product (in its free state) was transferred to a 150 mL hydrothermal reactor and reacted at 150 °C for 12 hours. After the reaction, it was cooled to room temperature and washed three times alternately with DMF and ethanol, centrifuged (11000 rpm, 10 min) each time for separation. Finally, it was vacuum dried at 80 °C for 24 hours to obtain MIL-88B(NH2). 0.5 g of the prepared MIL-88B(NH2) was weighed, and 0.25 g of a ferrocene derivative (selected from ferrocene formyl chloride or ferrocene formaldehyde; in this example, the ferrocene derivative was ferrocene formyl chloride) and 1 mL of acetic acid were added. The mixture was dissolved in 30 mL of DMF and stirred for 60 minutes to ensure homogeneity. Nitrogen gas was then introduced for 30 minutes to purge air. The mixture was quickly transferred to a hydrothermal reactor and reacted at 100 °C for 8 hours. After the reaction was completed, the product was separated by centrifugation (11,000 rpm, 10 minutes), washed three times with ethanol or deionized water, and dried under vacuum at 80°C for 24 hours to obtain MIL-88B(Fe)-NH2.

[0063] 3. Preparation of adsorption-reaction composite coatings: Add 100 mL of silica sol (solid content 20-30 wt%, pH 9-11) to a mixing tank, slowly add 40 mL of methylsilicate (sodium methylsilicate is used in this example), stir for 15 min to form a mixed base; add 5 g of nano SiO2, continue stirring for 20 min to obtain the base material.

[0064] Combination and dispersion of functional components: Take 10g of MIL-88B(Fe)-NH2 and 5g of biochar (physical adsorbent) in a beaker, add 50mL of deionized water, and dropwise add 0.75g of polyethylene glycol (PEG-400). Sonicate the mixture for 40min until no obvious agglomeration occurs, obtaining a suspension. Then, slowly pour the suspension into the base material and stir at high speed for 40min to ensure uniform dispersion. Add 0.3% bentonite and stir at low speed for 10min to adjust the viscosity; dropwise add 0.5g of tributyl phosphate and stir for 5min to eliminate air bubbles.

[0065] 4. Preparation of photocatalytic coatings: (1) Preparation of nitrogen-phosphorus co-doped g-C3N4: 10g of melamine and 1.5g of ammonium dihydrogen phosphate were ground for 30min and passed through a 200-mesh sieve. The mixed powder was transferred to an alumina crucible, covered and placed in a muffle furnace. The temperature was increased to 550℃ at 3℃ / min and held for 3h. After naturally cooling to room temperature, the powder was taken out and ground again for 15min and passed through a 200-mesh sieve to obtain light yellow nitrogen-phosphorus co-doped g-C3N4 powder.

[0066] (2) Preparation of BiVO4 sol: Add 20 mL of deionized water to a beaker, add 1.92 g of citric acid, and stir magnetically for 10 min until completely dissolved to obtain a citric acid solution; slowly add 1.98 g of bismuth nitrate, and continue stirring for 30 min until the solution is clear and transparent; add 0.69 g of ammonium metavanadate according to the Bi:V=1:1 molar ratio, and continue stirring for 30 min. During this period, add 0.1 mol / L dilute ammonia water dropwise with a dropper to adjust the pH of the solution to 3.0; continue stirring for 1 h to obtain a uniform and transparent BiVO4 sol (concentration of about 5.0 wt%).

[0067] (3) Dispersion of CoO nanoparticles and pre-composite of g-C3N4-CoO-BiVO4: Add 10 mL of deionized water to a 50 mL beaker, add 0.05 g of CoO nanoparticles, add 5 mL of 0.1 wt% sodium polycarboxylate (SN-5040) aqueous solution, and sonicate in an ultrasonic instrument for 20 min; after sonication, add 1 g of nitrogen-phosphorus co-doped g-C3N4 powder to the beaker, and stir magnetically for 1 h (400 r / min) to make g-C3N4 uniformly dispersed in the CoO suspension; slowly pour the prepared 1 g BiVO4 sol into the above mixture, and continue to sonicate for 30 min to obtain the g-C3N4-CoO-BiVO4 pre-composite system.

[0068] (4) Preparation of BPQDs: Place 0.1g of black phosphorus block into a 50mL centrifuge tube, add 20mL of solvent (selected from anhydrous ethanol, N-methylpyrrolidone or bio-based solvent prepared from waste cooking oil; the solvent used in this example is bio-based solvent prepared from waste cooking oil), seal and place in an ultrasonic instrument for ultrasonic peeling for 3h (pause for 5min every 30min during ultrasonication to prevent the solvent from overheating; black phosphorus is easily oxidized and must be operated under inert gas protection, or used immediately after ultrasonication is completed quickly); after ultrasonication, place the centrifuge tube into a centrifuge and centrifuge at 8000r / min for 10min to remove the unpeeled black phosphorus block; take the supernatant from the centrifugation and filter it with qualitative filter paper to obtain a transparent BPQDs solution (concentration of about 0.5mg / mL, verified by UV-Vis spectrophotometer, with a characteristic absorption peak at 660nm, for later use).

[0069] Note: The preparation process of the bio-based solvent made from edible waste oil used in step (4) is as follows: (a) Impurity removal: Take 100g of edible waste oil, add 5g of activated clay and stir at 80℃ for 30min, then filter; add 10g of sodium carbonate powder, stir at 60℃ for 20min, let stand and filter to remove salt residue, wash with deionized water until neutral, and obtain refined oil. (b) Transesterification: 20g of methanol (oil: alcohol = 1:0.2) and 2g of KOH were added to the refined oil and stirred under reflux at 65℃ for 2h; after cooling, the lower layer of glycerol was removed by separation, and the upper layer was washed until neutral to obtain crude fatty acid methyl ester. (c) Hydrogenation: Add 0.5g Ni / Al2O3 catalyst to the crude product, purge hydrogen gas into the autoclave to 3MPa, and react at 180℃ for 4h; filter to remove catalyst to obtain saturated fatty acid methyl ester; (d) Purification: The hydrogenated product, saturated fatty acid methyl ester, was transferred to a distillation flask and distilled at 200°C under normal pressure. The fraction was collected and dried over anhydrous magnesium sulfate and then filtered to obtain the bio-based solvent.

[0070] (5) Preparation of amino-modified GQDs: Add 2.0 g of citric acid and 20 mL of deionized water to the lining of the high-pressure reactor, stir until dissolved, slowly add 0.5 mL of ethylenediamine (adjust pH to 7.0), and continue stirring for 10 min; seal the reactor, place it in an oven, and perform hydrothermal reaction at 180 °C for 4 h; cool naturally to room temperature, transfer the reaction solution to a dialysis bag (the molecular weight cutoff (MWCO) of the dialysis bag is 1000 D), and dialyze with deionized water for 24 h (change the water every 6 h to remove unreacted citric acid and ethylenediamine); concentrate the solution after dialysis to 0.5 mg / mL to obtain amino-modified GQDs.

[0071] (6) BPQDs / GQDs composite (construction of a dual quantum dot synergistic system): 15 mL of BPQDs solution and 5 mL of GQDs solution were measured according to the mass ratio of BPQDs to GQDs of 3:1 and poured into a 50 mL beaker; 1 mL of 0.05 wt% KH-560 solution was added dropwise to the mixed solution and magnetically stirred for 10 min; the mixture was placed in an ultrasonic instrument and ultrasonicated at 300 W power for 15 min to obtain the BPQDs / GQDs composite solution.

[0072] (7) Loading and shaping: Take 1.0g of CoO / BiVO4 / g-C3N4 pre-composite system, add 10mL of deionized water, and ultrasonically disperse for 10min; slowly add 8mL of the above BPQDs / GQDs composite solution, and magnetically stir for 2h; dry in an oven at 80℃ for 4h to obtain dry gel; transfer to a muffle furnace, heat to 420℃ at 2℃ / min, keep warm for 2h, and grind through a 300-mesh sieve after natural cooling to obtain BPQDs / GQDs / CoO / BiVO4 / g-C3N4 composite photocatalyst material.

[0073] (8) Pretreatment of composite photocatalyst: Take 10g of BPQDs / GQDs / CoO / BiVO4 / g-C3N4 composite photocatalyst material, add 50mL of deionized water, add 0.5wt% sodium polycarboxylate, and ultrasonically disperse for 30min to form a uniform suspension.

[0074] (9) Preparation of inorganic base material: Add 100 mL of silica sol to the stirred tank, slowly add 30 mL of modified lithium silicate (in this example, a 20 wt% methyl-modified lithium silicate polymer solution is used), stir for 10 min to form a mixed base material. Add 5 g of fumed silica and 3 g of nano TiO2, and continue stirring for 20 min to improve the mechanical properties of the coating.

[0075] Note: The preparation process of the 20wt% methyl-modified lithium silicate polymer solution used in step (9) is as follows: Take 80 mL of lithium silicate (modulus 4, solid content 22 wt%, Wona Fluorine Materials Co., Ltd.), dilute with 10 mL of deionized water, stir for 5 min, adjust the pH to 9-10 with 0.1 mol / L hydrochloric acid, and maintain the temperature in a 40-50℃ water bath. Coupling agent solution: Add 7 mL of methyltrimethoxysilane (MTMS) to 3 mL of anhydrous ethanol and stir until homogeneous. Slowly add the coupling agent solution dropwise to the lithium silicate system at 1-2 mL / min, heat to 55-60℃, stir at 500 rpm for 2-3 h, keeping the system transparent during this period. Cool to room temperature and adjust the pH to 9-10 to obtain a 20 wt% transparent modified lithium silicate solution.

[0076] (10) Combining and dispersing: Slowly drip 40 mL of the suspension from step (8) into the base material while stirring at high speed for 30 min; adjust the viscosity of the coating with 20 mL of deionized water; add 0.3 wt% of silicone defoamer (a commercially available product; the silicone defoamer in this example was purchased from Jinan Delan Chemical Co., Ltd.), and stir at low speed for 10 min to remove bubbles.

[0077] 5. Preparation of porous ceramics for purifying indoor volatile organic compounds: (1) Cleaning of porous ceramic surfaces: The calcium hexaaluminate-based porous ceramic material prepared in step 1 was ultrasonically cleaned in anhydrous ethanol for 15-20 minutes to remove surface dust and oil. The cleaned ceramic was then placed in a forced-air drying oven and dried at 60-80℃ for 2-4 hours to ensure that there was no moisture in the pores.

[0078] (2) In vacuum negative pressure porous ceramics, adsorption-reaction type composite coatings: Place a corrosion-resistant tray inside a vacuum drying oven and pour in the adjusted adsorption-reaction composite coating. The coating volume should be sufficient to completely submerge the porous ceramic (the liquid level should be 2 cm above the top of the ceramic). Slowly place the pretreated calcium hexaaluminate-based porous ceramic material into the coating, ensuring complete immersion and avoiding air bubble encapsulation. Close the vacuum drying oven door, start the vacuum pump, and slowly evacuate to -0.06~-0.08 MPa. Maintain this negative pressure for 30 minutes, using the negative pressure difference to allow the coating to penetrate the pores inside the ceramic and simultaneously form a uniform wetting layer on the surface. After the set time is reached, slowly open the vacuum valve to release the negative pressure. Once the pressure returns to normal, remove the ceramic, gently tilt it, and drain any excess coating from the surface. At this point, the ceramic pores are loaded with coating, and a thin coating has formed on the surface. Place the drained ceramic back into the drying oven and maintain the temperature at 60℃ for 2 hours to slowly evaporate the solvent in the coating. This allows the coating inside the pores and on the surface to initially set, preventing cracking or pore blockage caused by rapid solvent evaporation during subsequent high-temperature curing. The temperature was raised to 120℃ and held for 3 hours to allow the adsorbed and reacted components in the coating to firmly bond with the pore walls and surface of the ceramic, forming a stable composite structure. After natural cooling to room temperature, the coating loading was calculated and controlled at 10%.

[0079] (3) Photocatalytic coating sprayed onto porous ceramic surfaces: Set the air compressor pressure to 0.4 MPa, maintain a distance of 15-20 cm between the spray gun and the ceramic surface, keep the spraying angle at 90° (perpendicular to the ceramic surface), and move at a uniform speed (approximately 5 cm / s) to avoid localized paint buildup. Employ a "thin coat, multiple coats" strategy. After the first coat, pre-bake the ceramic in a 60°C oven for 10 minutes (to allow the paint to initially adhere and prevent dripping during subsequent coats). Repeat the spraying 2-3 times, pre-bake for 10 minutes after each coat, ultimately controlling the dry film thickness to 5-10 μm.

[0080] Specifically, the porous ceramic prepared in this embodiment for purifying indoor volatile organic compounds, such as... Figure 1 As shown.

[0081] Example 2 The specific preparation process of the porous ceramic for purifying indoor volatile organic compounds in this embodiment differs from that in Example 1 only in that: in step (10) of step 4, 30 mL of the suspension from step (8) is slowly dripped into the base material.

[0082] Example 3 The specific preparation process of the porous ceramic for purifying indoor volatile organic compounds in this embodiment differs from that in Example 1 only in that: in step (10) of step 4, 20 mL of the suspension from step (8) is slowly dripped into the base material.

[0083] Comparative Example 1 This comparative example is the calcium hexaaluminate-based porous ceramic material prepared in Example 1.

[0084] Comparative Example 2 The only difference between this comparative example and Example 1 is that the calcium hexaaluminate-based porous ceramic material is not coated with a photocatalytic coating.

[0085] Comparative Example 3 The only difference between this comparative example and Example 1 is that the calcium hexaaluminate-based porous ceramic material is not loaded with an adsorption-reactive coating.

[0086] Comparative Example 4 The only difference between this comparative example and Example 1 is that the calcium hexaaluminate-based porous ceramic material does not support adsorption-reaction coatings, and BPQDs, GQDs and CoO are not used to modify BiVO4 / g-C3N4 when preparing photocatalytic coatings.

[0087] After preparing nitrogen-phosphorus co-doped g-C3N4 and BiVO4 sols, the following steps were performed to prepare composite photocatalyst powder: 1g of nitrogen-phosphorus co-doped g-C3N4 powder was weighed and added to 1g of prepared BiVO4 sol and 10mL of deionized water; the mixture was transferred to an ultrasonic instrument (300W power) and ultrasonically dispersed for 30min (ultrasound can break the interlayer agglomeration of g-C3N4, so that BiVO4 sol is uniformly loaded on the surface of g-C3N4); after ultrasonication, the mixture was poured into an evaporating dish and dried in an 80℃ forced-air oven for 4h (low temperature and slow drying avoid rapid solvent evaporation leading to particle agglomeration), resulting in a light yellow-green dry gel; the dry gel was transferred to an alumina crucible and placed in a muffle furnace at 450℃ for 2h; after calcination, it was naturally cooled to room temperature, the product was taken out and ground for 10min, and passed through a 300-mesh sieve to obtain a light yellow BiVO4 / g-C3N4 composite photocatalyst powder.

[0088] Experiment Example 1: Formaldehyde Removal Rate and Durability Testing Reaction apparatus (schematic diagram shown) Figure 2 As shown): 100mL closed glass reactor (quartz glass top, including gas inlet / outlet / sampling port and temperature sensor), 300W xenon lamp (simulating sunlight). Figure 2 (Not shown in the image).

[0089] Test conditions: 2 mL of deionized water was added to the bottom of the reactor (simulating the humidity of the actual environment). Then, a quartz reactor (d=20 mm, h=30 mm, open at the top; the quartz reactor has good light transmittance and high transmittance of sunlight simulated by the xenon lamp, which is conducive to driving the photocatalytic degradation of formaldehyde) containing a porous ceramic sample (d=10 mm, h=20 mm) was placed at the bottom of the closed glass reactor. Pure O2 (2 atm) was introduced to remove the air in the device. 3 μL of formaldehyde solution (mass concentration of 37%) was injected into the closed glass reactor using a microsyringe (formaldehyde is volatile and will evaporate into the air in the reactor after being injected into the closed glass reactor). Samples were taken for analysis every 20 min for a total of 80 min. The adsorption and degradation effect of formaldehyde on Examples 1-3 and Comparative Examples 1-4 was tested in this way. The test results are shown in Table 1. The same testing method was used to conduct durability tests on Examples 1-3 and Comparative Examples 3-4. The durability test samples were used repeatedly, and the number of cycles in which "the removal rate was less than 90% in 120 minutes" was recorded. The test results are shown in Table 2.

[0090] Table 1

[0091] Table 2

[0092] As shown in Table 1, the porous ceramic-supported composite coatings prepared in this invention exhibit excellent VOCs removal rates. Comparative Examples 1-3 demonstrate that both the adsorption-reaction type and the photocatalytic type coatings have a significant effect on formaldehyde removal, with the photocatalytic type coating showing better removal efficiency than the adsorption-reaction type coating within the same timeframe. This is because the photocatalytic type coating can achieve a full-spectrum response, generating •OH and •O2 in a short time. - The presence of a large total amount of three types of active species—negative oxygen, positive oxygen, and negative oxygen ions (NEO, NE, and NE)—allows for deep mineralization of pollutants, preventing the accumulation of intermediate products and resulting in stronger degradation momentum. As shown in Comparative Example 4, the modification of BiVO4 / g-C3N4 by BPQDs, GQDs, and CoO improves the formaldehyde removal rate and efficiency. This is because BPQDs, GQDs, and CoO broaden the light absorption range of the photocatalytic coating, converting more photons into photogenerated carriers and providing more energy for the reaction. Simultaneously, the high conductivity of BPQDs / GQDs and the Z-shaped heterojunction constructed with CoO inhibit electron-hole recombination and extend carrier lifetime. Furthermore, in addition to the •OH and •O2 generated by BiVO4 / g-C3N4… - In addition, CoO also generates •OH, and the electron transport of BPQDs / GQDs promotes •O2. - When converted to •OH, the total amount of active species generated increases within the same time frame, and the oxidation rate of formaldehyde by •OH is higher than that of •O2. -Higher efficiency accelerates the degradation of formaldehyde into CO2 and H2O, resulting in a higher formaldehyde removal rate.

[0093] As shown in Table 2, the porous ceramic-supported composite coatings prepared in this invention exhibit outstanding durability, maintaining a formaldehyde removal rate of no less than 90% after 8 cycles. It can be seen that the modification of BiVO4 / g-C3N4 by BPQDs, GQDs, and CoO extends the photocatalytic lifetime. This is because BPQDs and GQDs broaden light absorption to the near-infrared region, while CoO enhances photoresponse stability, preventing the degradation efficiency decrease caused by BiVO4 / g-C3N4's absorption of only visible light and the decay of photoresponse after long-term illumination. Furthermore, BPQDs / GQDs rapidly transfer charge carriers, and CoO constructs a Z-shaped heterojunction to suppress electron-hole recombination, reducing the passivation of catalyst active sites in BiVO4 / g-C3N4 due to charge carrier recombination accumulation. Simultaneously, the active species such as •OH generated synergistically by the multi-components can promptly degrade formaldehyde and intermediate products, preventing intermediate products from adhering and clogging active sites, thereby extending the coating's continuous formaldehyde removal time.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A porous ceramic for purifying indoor volatile organic compounds, characterized by: The porous ceramic substrate is loaded with a photocatalytic coating; The photocatalyst used in the photocatalytic coating is prepared by a method comprising the following steps: mixing BPQDs, amino-modified GQDs, nitrogen-phosphorus co-doped g-C3N4, nano CoO and BiVO4 sol, drying and then calcining; the mass ratio of the BPQDs, amino-modified GQDs, nitrogen-phosphorus co-doped g-C3N4, nano CoO and BiVO4 sol is (2.25-5):(0.75-1.7):(80-120):(3-8):(80-120).

2. The porous ceramic for purifying volatile organic compounds in a clean room according to claim 1, wherein: The mixing comprises: mixing BPQDs solution, amino-modified GQDs solution and silane coupling agent to obtain a BPQDs / GQDs composite solution; dispersing nano CoO and nitrogen-phosphorus co-doped g-C3N4 in water, and then mixing with BiVO4 sol to form a g-C3N4-CoO-BiVO4 pre-composite system; mixing the g-C3N4-CoO-BiVO4 pre-composite system and the BPQDs / GQDs composite solution; in the pre-composite system, the mass ratio of nano CoO, nitrogen-phosphorus co-doped C3N4, BiVO4 sol and water is (0.03-0.08):(0.8-1.2):(0.8-1.2):(8-12); the mass ratio of the total quantum dots in the pre-composite system and the BPQDs / GQDs composite solution is 100:(0.3-0.6).

3. The porous ceramic for purifying volatile organic compounds in a clean room according to claim 2, wherein: The preparation of the BiVO4 sol comprises: dissolving bismuth nitrate, citric acid and ammonium metavanadate in water, then adjusting the pH of the mixed solution to 3-3.5 to obtain BiVO4 sol; the molar ratio of the bismuth nitrate, citric acid and ammonium metavanadate is 1:(1.5-2.5):(0.95-1.05); the mass ratio of the citric acid and water is 1.92:(18-25); the pH of the mixed solution is adjusted by using ammonia water; the preparation of the nitrogen-phosphorus co-doped g-C3N4 comprises: calcining melamine and ammonium dihydrogen phosphate at 500-550 DEG C, and then cooling to obtain nitrogen-phosphorus co-doped g-C3N4; the mass ratio of the melamine and ammonium dihydrogen phosphate is 10:(1.2-2); the calcination time is (3-3.5) h.

4. The porous ceramic for purifying volatile organic compounds in a clean room according to claim 2, wherein: The mass concentration of BPQDs in the BPQDs solution is (0.3-0.8) mg / mL, and the particle size is 2-5 nm; the mass concentration of amino-modified GQDs in the amino-modified GQDs solution is (0.3-0.8) mg / mL, and the particle size is 2-3 nm; the calcination temperature is 400-450 DEG C, and the time is (2-2.5) h.

5. The porous ceramic for purifying volatile organic compounds in a clean room according to any one of claims 1 to 4, characterized by: The photocatalytic coating mainly comprises silica sol, modified lithium-based silicate, fumed white carbon black, nano TiO2 and the photocatalyst; the thickness of the photocatalytic coating is 5-10 microns; the porous ceramic substrate is mainly prepared by mixing alumina, calcium carbonate, hollow glass microbeads, dispersant and curing agent, and then curing and sintering; the open porosity of the porous ceramic substrate is greater than or equal to 85%.

6. The porous ceramic for purifying volatile organic compounds in a clean room according to any one of claims 1 to 4, wherein: The adsorption-reaction type composite coating is first loaded on the surface and pores of the porous ceramic substrate, and then the photocatalytic type coating is loaded on the surface of the adsorption-reaction type composite coating, wherein the adsorption-reaction type composite coating mainly comprises MIL-88B(Fe)-NH2 and a physical adsorption material; and the loading amount of the adsorption-reaction type composite coating in the porous ceramic substrate is 5-10%.

7. The porous ceramic for purifying volatile organic compounds in a clean room according to claim 6, wherein: The adsorption-reaction type composite coating mainly comprises silica sol, modified lithium-based silicate, nano-SiO2, the MIL-88B(Fe)-NH2 and a physical adsorption material; and the physical adsorption material is one, two or more than three of biochar, activated carbon, bamboo charcoal, zeolite powder, tourmaline powder, diatomite, vermiculite, shell powder, modified white clay and modified cellulose.

8. The porous ceramic for purifying volatile organic compounds in a clean room according to claim 5, wherein: The dispersant is one, two or more than three of polyacrylammonium, tartaric acid, glutaraldehyde, ammonium citrate, sodium citrate and polyethyleneimine; and the curing agent is one, two or more than three of sec Z, propylene oxide glyceryl ether, hydroxypropyl methylcellulose, N,N'-methylene bisacrylamide, ethyl acetate and polyvinyl alcohol.

9. A method for producing a porous ceramic for purifying volatile organic compounds in a clean room as claimed in any one of claims 1 to 8, characterized by: The method comprises the following steps: The porous ceramic substrate is vacuum impregnated in an adsorption-reaction type composite coating with active components of MIL-88B(Fe)-NH2 and a physical adsorption material, and a coating is formed through temperature curing, and then a photocatalytic coating with active components of the photocatalyst is coated on the surface of the coating.

10. The method of claim 9, wherein the porous ceramic is prepared by the steps of: a) mixing a ceramic powder with a binder; b) extruding the mixture to form a green body; c) drying the green body; d) sintering the green body; and e) coating the sintered green body with a coating material. The pressure of the vacuum impregnation is-0.06~-0.08Mpa, and the holding time is 30-45min; and the curing comprises first holding at 60-70℃ for 2h, and then holding at 120-150℃ for 3h.

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