Mildew-proof formaldehyde-removing gypsum and preparation method thereof

Abstract

The invention relates to the technical field of gypsum, and discloses a preparation method of mildew-proof formaldehyde-removing gypsum, which comprises the following steps: S1, loading Pd-Cu quantum clusters on a ZIF-8 carrier by adopting a microwave plasma sputtering method under the conditions that the microwave power is 300-600W and the concentration of a precursor solution is 0.05-0.2 mol / L; s2, Au nanoparticles are deposited on the surface of BiOI / BiVO4 through a chemical vapor deposition method, the deposition temperature ranges from 300 DEG C to 400 DEG C, and the carrier gas flow ranges from 50 mL / min to 150 mL / min; and S3, chitosan / PNIPAMJanus particles are prepared through a micro-fluidic interfacial polymerization method, and Ag-Pd bimetallic particles are packaged on the chitosan / PNIPAMJanus particles. The Pd-Cu quantum clusters are loaded by adopting a microwave plasma sputtering method, and the catalytic formaldehyde decomposition efficiency is improved by 175%. Through quantum confinement effect and bimetallic cooperation, the problem that active sites are uncontrollable is solved.

Description

Technical Field

[0001] The invention relates to the technical field of gypsum, in particular to mildew-proof and formaldehyde-removing gypsum and a preparation method thereof. Background Art

[0002] Mold-proof and formaldehyde-removing gypsum is in urgent demand in areas such as interior decoration and medical cleanrooms. Current technology primarily purifies functional gypsum through physical mixing with photocatalysts (such as TiO2) or mildew inhibitors (nanosilver). Mainstream processes include pyrolysis loading, impregnation reduction, and mechanical mixing. Industry standards typically test formaldehyde removal rates based on GB / T 18883, while mildew resistance levels refer to ISO 16869.

[0003] Existing mold-proof and formaldehyde-removing gypsum technology usually uses a conventional pyrolysis process. In this process (calcination of loaded Pd-Cu), high temperature (500°C) induces metal atoms to migrate and agglomerate, forming 5-10nm coarse particles (XRD half-peak width ≥1.2°, TEM statistical RSD ≥40%). The specific surface area drops sharply to 200-300m 2 / g, the insufficient active site density limits the formaldehyde degradation rate to 0.05-0.07s -1 , cannot meet the high purification efficiency requirements in some specific scenarios. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a mildew-proof and formaldehyde-removing gypsum and a preparation method thereof, which solves the problem in the prior art that the active site density of gypsum is insufficient, resulting in a limited formaldehyde degradation rate.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: a mildew-proof and formaldehyde-removing gypsum, comprising the following components in proportions by mass:

[0006] Gypsum matrix: 50-65 parts;

[0007] Metal-organic framework-supported bimetallic catalyst: 10-25 parts;

[0008] Visible light responsive semiconductor heterojunction: 8-15 copies;

[0009] Slow-release mildew inhibitor: 3-10 parts;

[0010] Reinforcement fiber: 2-8 parts;

[0011] Additives: 1-5 parts.

[0012] Preferably, the gypsum matrix is industrial by-product phosphogypsum or desulfurized gypsum, the purity of the β-hemihydrate gypsum is ≥85%, and the soluble impurities are removed by acid washing.

[0013] The pickling process involves soaking in dilute sulfuric acid (5-10 wt%) to dissolve free alkaline substances and soluble salts, followed by water washing to neutrality and drying.

[0014] High-purity β-hemihydrate gypsum crystals (XRD characteristic peaks 2θ=11.6°, 20.7°) provide a stable hydration skeleton, and its crystal defects (dislocation density ≤1×10 14 m -2 ) as anchoring points for functional components to enhance interfacial bonding; pickling treatment eliminates the poisoning effect of impurities on the active sites of the catalyst to ensure formaldehyde decomposition efficiency.

[0015] Preferably, the metal organic framework supported bimetallic catalyst is a Pd-Cu quantum cluster supported on a ZIF-8 carrier, the molar ratio of Pd to Cu is 1:1-1:3, and the cluster size is 1.5-2.2 nm.

[0016] ZIF-8 (zeolitic imidazolate framework-8) was used as a support to load Pd-Cu bimetallic quantum clusters via microwave plasma sputtering. The precursor was an ethanol solution of Pd(acac)2 (palladium acetylacetonate) and Cu(acac)2 (copper acetylacetonate). The microwave power range was 300-600W, and the precursor solution concentration was 0.05-0.2 mol / L. The molar ratio of Pd to Cu was precisely controlled (1:1-1:3) by varying the precursor feed ratio. The cluster size was controlled to 1.5-2.2 nm by synergistically adjusting the microwave power and reaction time (10-30 minutes).

[0017] Confinement effect of ZIF-8: The micropore diameter of ZIF-8 (1.16 nm) matches the molecular kinetic diameter of formaldehyde (0.45 nm), which selectively adsorbs and enriches formaldehyde molecules through the molecular sieve effect, thereby increasing the local reactant concentration.

[0018] Quantum confined catalysis: When the Pd-Cu cluster size is ≤2.2nm, the quantum size effect causes the d-band center to shift upward (XPS verification Δ=+0.3-0.5eV), reducing the C=O bond breaking energy barrier (DFT calculation reduces it from 1.5eV to 0.8eV); the bimetallic synergy optimizes the oxygen species (O - ,·OH) generation path.

[0019] Optimization of the bimetallic ratio: When Pd:Cu = 1:1-1:3, Pd provides highly catalytically active sites, and Cu improves stability by inhibiting Pd oxidation (forming Pd-Cu alloy). The synergistic effect completely mineralizes formaldehyde into CO2 and H2O through the Mars-van Krevelen mechanism (lattice oxygen participates in oxidation).

[0020] Preferably, the visible light responsive semiconductor heterojunction is a BiOI / BiVO4 core-shell structure, Au nanoparticles are deposited on the surface thereof, the particle size of the Au nanoparticles is 40-60 nm, and the mass ratio of Au to BiVO4 is 1:10-1:20.

[0021] BiOI nanosheets (thickness 10-50 nm) were synthesized by a two-step hydrothermal method, and then a BiVO4 shell was epitaxially grown on its surface to form a core-shell structure; Au nanoparticles were deposited on the BiVO4 surface by chemical vapor deposition (CVD, carrier gas N2 flow rate 50-150 mL / min, temperature 300-400°C), with the particle size controlled to 40-60 nm, and the mass ratio of Au to BiVO4 was adjusted to 1:10-1:20 by adjusting the precursor feed amount.

[0022] BiOI / BiVO4 heterojunction energy band design:

[0023] BiOI (band gap Eg = 1.8 eV) and BiVO4 (Eg = 2.4 eV) form a type II heterojunction. The conduction band (CB) and valence band (VB) positions are offset (CB of BiOI = -0.4 eV, CB of BiVO4 = 0.2 eV), driving the migration of photogenerated electrons from BiOI to BiVO4, and the reverse migration of holes to BiOI, thereby suppressing electron-hole recombination (the fluorescence lifetime is increased from 5 ns to 12 ns).

[0024] The core-shell structure reduces the interface resistance through close interface contact (HRTEM shows that the lattice spacing of 0.312nm matches 0.235nm) and improves the charge separation efficiency (IPCE test shows that the quantum efficiency in the visible light region reaches 45%).

[0025] Localized surface plasmon resonance (LSPR) effect of Au nanoparticles:

[0026] The LSPR absorption peak of Au nanoparticles (particle size 40-60nm) is located at 550-650nm (verified by UV-Vis absorption spectrum), overlapping with the visible light response range of BiOI / BiVO4 (400-650nm). Through the near-field enhancement effect, the light energy is converted into high-energy hot electrons and injected into the BiVO4 conduction band, driving the formaldehyde oxidation reaction under light-free conditions.

[0027] The mass ratio of Au to BiVO4 (1:10-1:20) optimizes the balance between plasma hot electron yield and catalyst specific surface area: when the mass ratio is >1:10, Au excessively covers the BiVO4 active sites; when it is <1:20, hot electron injection is insufficient and the catalytic activity decreases.

[0028] Synergistic catalytic mechanism:

[0029] After hot electrons are injected into the conduction band of BiVO4, they react with O4 molecules adsorbed on the surface to generate superoxide radicals (·O2 - ), and at the same time, the BiOI valence band holes oxidize H2O to generate hydroxyl radicals (·OH), and the two synergistically attack formaldehyde molecules (HCHO+·OH→HCOOH→CO2+H2O).

[0030] Au nanoparticles act as electron relay stations, accelerating the charge transfer between BiVO4 and BiOI (electrochemical impedance spectroscopy shows a 60% reduction in charge transfer resistance).

[0031] Preferably, the slow-release mildew inhibitor is chitosan / poly (N-isopropylacrylamide) Janus microparticles, which encapsulate Ag-Pd bimetallic particles. The diameter of the Janus microparticles is 50-200 μm, and the LCST of PNIPAM is 30-40°C.

[0032] Janus microparticles composed of chitosan (hydrophilic side) and PNIPAM (thermosensitive side) were prepared using microfluidic chip technology, encapsulating Ag-Pd bimetallic particles (Ag:Pd molar ratio of 1:1-1:2). The microfluidic oil phase consisted of silicone oil (containing 1-3% Span 80 surfactant), and the aqueous phases consisted of a chitosan solution (2-4wt%) and a PNIPAM prepolymer solution (5-10wt%, containing 0.1-0.3wt% MBA crosslinker). The flow rate ratio (oil phase:aqueous phase 1:aqueous phase 2) was 3:1:1, and the chip temperature was 25-40°C. The particle diameter was controlled to be 50-200μm. The liquid crystal stability (LCST) of 30-40°C was achieved by adjusting the hydrophilic / hydrophobic ratio of the PNIPAM segments (monomer / crosslinker ratio).

[0033] Humidity-temperature dual response mechanism of Janus structure:

[0034] Humidity response of chitosan side: Chitosan molecular chain contains a large number of hydroxyl and amino groups. At high humidity (RH>80%), it absorbs water molecules through hydrogen bonds and swells (swelling rate ΔD=120%), and the internal pore size expands (from 10nm to 30nm), accelerating Ag + Fick diffusion release (diffusion coefficient D = 1.2 × 10 -10 cm 2 / s), directly inhibiting the growth of mold hyphae (Ag + Minimum inhibitory concentration (MIC) = 0.02 μg / mL).

[0035] Temperature response of the PNIPAM side: When the temperature exceeds the LCST (30-40°C), the PNIPAM chain segments hydrophobically collapse (dynamic light scattering shows a 50% particle size reduction), resulting in asymmetric deformation of the Janus particles (contact angle increases from 30° to 90°), exposing the internal Pd particles and catalyzing the decomposition of formaldehyde (activation energy Ea = 45 kJ / mol). The LCST is regulated by the Flory-Huggins theory, as follows:

[0036]

[0037] where χ is the interaction parameter, φ is the volume fraction, and θ is the reference temperature.

[0038] Ag-Pd bimetallic synergy:

[0039] Bactericidal function of Ag: Ag + It binds to the thiol group (-SH) of the fungal cell membrane, disrupting the redox balance (the glutathione oxidized state / reduced state ratio GSSG / GSH increases from 0.2 to 1.5) and inducing DNA damage (comet assay shows tail moment ≥20%).

[0040] Catalytic function of Pd: Pd nanoparticles (particle size 5-15nm) activate formaldehyde molecules on the surface and oxidize them to CO2 and H2O via the Langmuir-Hinshelwood mechanism (HCOO was detected by in situ DRIFTS). - intermediate); electronic coupling between Pd and Ag (XPS binding energy shift Δ=0.8eV) inhibits Ag + Over-release to extend the life of the mildewcide.

[0041] Particle size and release kinetics:

[0042] Size control (50-200 μm): Through the microfluidic chip flow rate and interfacial tension (γ=25-35 mN / m), larger particles (150-200 μm) provide long-term sustained release (first-order kinetic rate constant k=0.02h -1 ), smaller particles (50-100 μm) achieve fast response (k = 0.15h -1 ).

[0043] Bimetallic encapsulation: Ag-Pd particles are electrostatically adsorbed (chitosan-NH3 + With PdCl4 2- Complexation, coordination constant logβ=6.8) is loaded on the Janus interface to avoid metal agglomeration (TEM shows dispersion degree PDI<0.2).

[0044] Preferably, the reinforcing fiber is silicon carbide whisker with a fiber diameter of 0.5-2 μm and an aspect ratio of ≥20:1; the additives include sodium polyacrylate and citric acid with a mass ratio of 1:0.5-1:2.

[0045] Silicon carbide whiskers are synthesized via vapor deposition (CVD) using SiO2 and carbon black as raw materials. They are grown at 1400-1600°C via a vapor-liquid-solid (VLS) mechanism, resulting in a controlled fiber diameter of 0.5-2 μm and an aspect ratio ≥ 20:1. The whisker surface is modified with a silane coupling agent (KH-550) to enhance interfacial bonding strength with the gypsum matrix.

[0046] Size effect and mechanical enhancement:

[0047] When the diameter is ≤2μm, the dislocation density inside the whisker decreases (XRD calculation ≤1×10 13 m -2 ), close to the theoretical strength (6GPa); when the aspect ratio is ≥20:1, the crack bridging mechanism (Griffith theory critical stress intensity factor K_IC ≥2.5MPa·m 1 / 2 ) and fiber pull-out effect (pulling work W_pul lout=0.5-1.5J / m 2 ) synergistically improve the flexural strength of gypsum (6.5-8.5MPa).

[0048] Whisker orientation distribution (controlled by tape casting) forms a three-dimensional network skeleton to inhibit gypsum shrinkage and cracking (thermal expansion coefficient CTE is 15×10 -6 / ℃ down to 8×10 -6 / ℃).

[0049] Surface modification mechanism: amino groups (-NH2) of silane coupling agent and Ca in gypsum matrix 2+ A coordination bond is formed (binding energy ΔE = 1.8 eV, DFT calculation), and at the same time the hydrophobic segment (-CH3) reduces the surface energy of the whiskers (the contact angle increases from 30° to 110°), inhibiting the interface weakening caused by water penetration.

[0050] Additives (sodium polyacrylate and citric acid, mass ratio 1:0.5-1:2).

[0051] Technical Details: Sodium polyacrylate (molecular weight 2000-5000) is used as a dispersant, and citric acid (food grade) is used as a chelating agent, in a mass ratio of 1:0.5-1:2. The sodium polyacrylate is added in an amount of 0.5-2.0wt% and the citric acid is added in an amount of 0.25-4.0wt%. After dissolving in water, the mixture is blended with the gypsum slurry.

[0052] Dispersing effect of sodium polyacrylate:

[0053] Sodium polyacrylate is synthesized by carboxylate (-COO - ) adsorbed on the surface of gypsum particles (Zeta potential dropped from +5mV to -35mV), generating electrostatic repulsion (DLVO theoretical double layer thickness κ -1 =5-10nm) and steric hindrance effect to prevent particle agglomeration (D50 particle size is reduced from 50μm to 15μm);

[0054] The chain length of the molecular weight 2000-5000 (≈10-25nm) matches the gap between gypsum particles (20-50nm), forming a dense adsorption layer (adsorption capacity Γ=1.2-2.0mg / m 2 ).

[0055] Chelation regulation of citric acid:

[0056] The tricarboxylic acid group of citric acid and Ca 2+ Forming a stable complex (complexation constant log K = 8.3), delaying the conversion of hemihydrate gypsum (CaSO4·0.5H2O) to dihydrate gypsum (CaSO4·2H2O) (extending the setting time from 8 minutes to 15-25 minutes), and ensuring uniform dispersion of functional components;

[0057] A mass ratio of 1:0.5-1:2 optimizes the balance between dispersion and retarding setting: when the proportion of sodium polyacrylate is too high (1:0.5), excessive dispersion causes the slurry viscosity to decrease (from 1200mPa·s to 600mPa·s), affecting the molding strength; excessive citric acid (<1:2) leads to excessive retarding setting (setting time >30 minutes), reducing construction efficiency.

[0058] A method for preparing mildew-proof and formaldehyde-removing gypsum comprises the following steps:

[0059] S1. Pd-Cu quantum clusters were loaded on ZIF-8 support by microwave plasma sputtering, with microwave power of 300-600 W and precursor solution concentration of 0.05-0.2 mol / L;

[0060] High-energy electrons (5-15 eV) in the microwave plasma bombard the precursor molecules, preferentially breaking Pd-O (bond energy 318 kJ / mol) and Cu-O (bond energy 265 kJ / mol) bonds, releasing metal atoms. The imidazole ring nitrogen sites (Lewis basicity) of ZIF-8 anchor the metal atoms through coordination, forming subnanometer clusters (1.5-2.2 nm). The microwave non-thermal effect inhibits Ostwald ripening, and the quantum size effect (d-band center shifts up 0.3-0.5 eV) optimizes formaldehyde oxidation activity (TOF = 0.15-0.25 s). -1 ).

[0061] S2, depositing Au nanoparticles on the BiOI / BiVO4 surface by chemical vapor deposition at a deposition temperature of 300-400°C and a carrier gas flow rate of 50-150 mL / min;

[0062] High temperature (300-400℃) drives Au atoms to migrate to low-energy sites (lattice steps or defects) on the BiVO4 surface, epitaxially growing Au (111) crystal plane (lattice spacing 0.235nm) and BiVO4 (040) crystal plane (0.312nm) to form a mismatch interface (mismatch degree 24.7%), inducing stress field enhancement of localized surface plasmon resonance (LSPR); the carrier gas flow rate controls the distribution density of Au particles (5-15 particles / μm 2 ), LSPR hot electron injection into the BiVO4 conduction band (current density increased by 3 times), driving dark-state formaldehyde catalysis (apparent quantum efficiency AQE = 12-18%)

[0063] S3, chitosan / PNIPAMJanus microparticles were prepared by microfluidic interfacial polymerization and encapsulated with Ag-Pd bimetallic particles;

[0064] Oil-water interfacial tension (γ=25-35mN / m) drives the self-assembly of amphiphilic Janus structures; Ag + Through chitosan amino complexation (logβ=6.8), Pd 2+ Through PNIPAM carboxyl adsorption, interfacial polymerization forms a core-shell isolation structure. Janus asymmetry realizes dual controlled release of humidity response (chitosan swelling ratio ΔD = 120%) and temperature response (PNIPAM volume phase transition temperature LCST = 30-40°C), Ag + The antibacterial activity (MIC = 0.02 μg / mL) was synergistic with Pd catalysis (Ea = 45 kJ / mol).

[0065] S4, mixing the gypsum matrix with the functional components, and forming the mixture using an ice template-chemical foaming synergistic pore-forming process, with a freezing temperature of -20 to -40°C and a foaming agent H2O2 added in an amount of 0.5-2.0 wt%;

[0066] Ice crystals grow in a directional manner along the temperature gradient (Mullins-Sekerka instability model), forming vertically penetrating macropores (100-300 μm); H2O2 decomposes (activation energy 75 kJ / mol) to produce micron-sized bubbles (CO2) and nano-sized bubbles (O2), which are constrained by the ice template to expand and form mesopores (2-50 nm). The dual-level pore structure is determined by Fick's diffusion law (D_eff=2.1×10 -6 m 2 / s) to optimize formaldehyde mass transfer, porosity (65-75%) and strength (compressive strength 4.5-6.0MPa) are balanced.

[0067] S5. The functional components are loaded into the gypsum matrix by vacuum impregnation with a vacuum degree of 0.05-0.1 MPa for 1-3 hours, followed by curing at 50-70° C. and a humidity of 90-98%.

[0068] Vacuum negative pressure (ΔP = 2γ / r, γ = 72mN / m, r = 1μm) drives the functional components to penetrate deep into the pores (penetration depth ≥ 500μm). The humid and hot environment promotes the interweaving of dihydrate gypsum (CaSO4·2H4O) needle-shaped crystals (crystal aspect ratio ≥ 50:1), fixing the functional components through capillary forces (≈10kPa) and hydrogen bonds (bond energy ≈20kJ / mol), preventing them from falling off (activity retention ≥ 90% after 5 cycles).

[0069] Preferably, in S1, the precursors of the Pd-Cu quantum cluster are Pd(acac)2 and Cu(acac)2, the solvent is ethanol, and the microwave sputtering time is 10-30 minutes.

[0070] Precursor selection and solvent effects:

[0071] Acetylacetonate ligands of Pd(acac)2 and Cu(acac)2 (acac - ) stabilizes the metal center through chelation, and the high microwave absorption capacity (loss tangent tanδ = 0.941) of ethanol (dielectric constant ε = 24.3) enhances the plasma energy transfer efficiency and accelerates ligand dissociation.

[0072] In the microwave field, the Pd-O bond (bond energy 318 kJ / mol) and the Cu-O bond (bond energy 265 kJ / mol) are preferentially broken (electron temperature T_e≈10 4 K), released Pd 0 and Cu 0 The atoms are directionally anchored at the imidazole-N site (Lewis basicity) of ZIF-8 to form bimetallic clusters.

[0073] Microwave time and cluster size control:

[0074] When the sputtering time is less than 10 minutes, the amount of metal atom deposition is insufficient and the cluster size is discrete (1.0-3.0 nm). When the sputtering time is greater than 30 minutes, Ostwald ripening causes the clusters to coarsen (size > 3.0 nm).

[0075] The critical window is 10-30 minutes, and the non-thermal effect of microwaves (high-energy electron bombardment) inhibits cluster ripening and maintains the quantum size (1.5-2.2nm). The grain size calculated by XRD half-peak width is consistent with the HRTEM result (error ±0.2nm).

[0076] Solvent evaporation and loading uniformity:

[0077] The low boiling point of ethanol (78°C) and the microwave thermal effect synergistically promote the rapid volatilization of the solvent, avoiding local supersaturation and agglomeration of the precursor;

[0078] The confinement effect of ZIF-8 micropores (1.16 nm) restrains cluster growth, and the BET specific surface area increases from 1200 m 2 / g dropped to 950m 2 / g (after loading), indicating that the metal is uniformly dispersed in the pores of the carrier.

[0079] Preferably, in S2, the purity of the Au nanoparticle deposition target is 99.99%, and the sputtering gas pressure is 0.5-1.0 Pa.

[0080] The role of high-purity target (99.99%):

[0081] The high-purity target material (impurity content ≤ 100 ppm) ensures that the Au atoms produced by sputtering are almost free of impurities (Ag, Cu), reduces lattice distortion (XRD half-peak width ≤ 0.2°), forms a highly crystalline Au (111) crystal plane (lattice spacing 0.235 nm), and enhances the localized surface plasmon resonance (LSPR) effect.

[0082] Impurity atoms (Fe, Ni) occupy Au lattice sites, forming defect states (PL spectra show that the defect luminescence peak intensity is reduced by 90%), which inhibits the efficiency of hot electron injection (quantum efficiency loss ≤ 5%).

[0083] Control mechanism of sputtering gas pressure (0.5-1.0Pa):

[0084] Under low pressure (0.5-1.0Pa), Ar in plasma + The ions have a long mean free path (≈10-20 mm), high kinetic energy (50-100 eV), high sputtering yield (≈1.5-2.0 atoms / ion) when bombarding the target, and a fast Au atom deposition rate (≈5-10 nm / min), forming dense and uniform nanoparticles (particle size distribution RSD ≤ 15%).

[0085] When the pressure is greater than 1.0 Pa, Ar + As the collision frequency increases, energy dissipation leads to a decrease in deposition rate (≈2-3nm / min) and discrete particle size (RSD≥30%). When the gas pressure is <0.5Pa, high-energy ions bombard the substrate, destroying the BiVO4 surface structure (AFM shows that the roughness increases from 1.2nm to 4.5nm).

[0086] Preferably, in S4, the ice template-chemical foaming process forms a dual-level pore structure of macropores and mesopores, wherein the pore size of the macropores is 100-300 μm, the pore size of the mesopores is 2-50 nm, and the macropores account for 30-50%.

[0087] Formation mechanism of macropores (100-300 μm):

[0088] Ice crystal template dominance: Under low-temperature freezing (-20 to -40°C), water molecules crystallize directional-wise along the temperature gradient (Mullins-Sekerka instability model), resulting in columnar or lamellar ice crystal growth, with their size controlled by the freezing rate. Slower freezing rates (-20°C) allow for more time for ice crystal growth, resulting in larger pores (≈300 μm). Faster freezing rates (-40°C) increase ice crystal branching and reduce pore size (≈100 μm).

[0089] Balance of macropore proportion (30-50%): The porosity of the ice template is directly related to the solid content of the slurry. When the water-paste ratio is 0.5-0.7, the volume of ice crystals accounts for 30-50%. After melting, through macropores are formed, providing gas diffusion channels (effective diffusion coefficient D_eff = 2.1×10 -6 m 2 / s) while retaining the matrix skeleton strength (compressive strength 4.5-6.0MPa).

[0090] Mesopore (2-50nm) formation mechanism:

[0091] Chemical foaming is dominant: H2O2 decomposes in the alkaline gypsum slurry (2H2O2 → 2H2O + O2↑), producing micron-sized O2 bubbles (initial diameter 1-5μm) and nanoscale H2O molecular clusters. The foaming agent concentration (0.5-2.0wt%) regulates bubble density: at low concentrations (0.5wt%), bubbles are sparse, forming isolated mesopores (≈50nm); at high concentrations (2.0wt%), bubbles become dense and merge, reducing the mesopore size to 2-10nm.

[0092] Ice crystal constrained foaming: During the growth of ice crystals, bubbles are compressed in the gaps between ice crystals. The rigidity of the ice template restricts the expansion of bubbles, forming slit-like mesopores (BET specific surface area 25-35m 2 / g), significantly improving formaldehyde adsorption and catalyst loading sites.

[0093] Double-stage pore synergistic effect:

[0094] Mass transfer enhancement: The macropores act as fast diffusion channels (Knudsen diffusion dominates), and the mesopores provide high specific surface area active sites (Langmuir adsorption capacity Q_m = 12-18 mg / g). The two synergistically optimize the mass transfer efficiency of formaldehyde from the gas phase to the catalyst surface through Fick's diffusion law (apparent reaction rate k_app = 0.15-0.25 min -1 ).

[0095] Strength-porosity balance: When the macropore ratio is 30-50%, the porosity of 65-75% and the compressive strength of 4.5-6.0 MPa are optimally matched (Gibson-Ashby porous material model), avoiding excessive sacrifice of mechanical properties.

[0096] The present invention provides a mildew-proof and formaldehyde-removing gypsum and a preparation method thereof. It has the following beneficial effects:

[0097] 1. This invention uses microwave plasma sputtering to deposit Pd-Cu quantum clusters (1.5-2.2 nm), achieving atomic-level dispersion of metal active sites for the first time, boosting formaldehyde decomposition efficiency by 175%. Existing technologies rely on traditional thermal decomposition, where active components easily aggregate and exhibit uneven sizes (3-10 nm), resulting in low activity and poor stability. This solution, however, overcomes the technical bottleneck of uncontrollable active sites by leveraging quantum confinement effects and synergizing with bimetallic materials.

[0098] 2. The present invention is based on the temperature and humidity dual response design of chitosan / PNIPAMJanus particles to achieve Ag + The technology combines the dual effects of antibacterial and catalytic effects with the spatiotemporal controlled release of Pd. Existing antifungal agents are mostly static release agents, which can easily lead to overconsumption or ineffectiveness due to environmental fluctuations. This technology precisely controls the release rate through asymmetric swelling and phase transition mechanisms, resolving the conflicting issues of "complete release" or "delayed release" of antifungal agents.

[0099] 3. This invention utilizes an ice-templating-chemical foaming process to create a cross-scale structure with interconnected macropores (300μm) and mesopores (20nm) with a high specific surface area, tripling the formaldehyde mass transfer rate. Traditional single-pore materials often face the dilemma of either "fast mass transfer but few active sites" or "high activity but slow diffusion." This solution, through the synergistic dual-stage pore structure, addresses this dilemma by balancing pore structure and mechanical strength.

[0100] 4. This invention utilizes a vacuum impregnation (0.05 MPa) coupled with a moist heat curing process, achieving a 90% loading stability of the catalyst and mildew inhibitor within the gypsum matrix (after five cycles). Compared to conventional mechanical mixing or surface coating techniques, which suffer from uneven component distribution and easy shedding, this technology mitigates the problem of active component shedding by capillary force through directional penetration and crystal interweaving. BRIEF DESCRIPTION OF THE DRAWINGS

[0101] Figure 1 Schematic diagram of the method of the present invention. DETAILED DESCRIPTION

[0102] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the present specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0103] Example 1:

[0104] Component ratio: gypsum matrix 65%, ZIF-8@Pd-Cu (Pd:Cu=1:2) 15%, BiOI / BiVO4@Au (Au:BiVO4=1:15) 10%, chitosan / PNIPAMJanus particles (Ag-Pd5%) 8%, H2O22%.

[0105] step:

[0106] S1. Microwave plasma sputtering: Pd(acac)2 and Cu(acac)2 ethanol solutions (0.1 mol / L), microwave power 450 W, sputtering time 20 min, ZIF-8 loaded with Pd-Cu quantum clusters (size 1.8 ± 0.3 nm);

[0107] S2. Magnetron sputtering Au: Au nanoparticles (50 nm) were deposited on the BiVO4 surface at a sputtering pressure of 0.8 Pa and a N2 carrier gas flow rate of 100 mL / min.

[0108] S3. Microfluidic preparation of Janus microparticles: silicone oil (Span 80 2%) in the oil phase, chitosan (3 wt%) and PNIPAM (8 wt%) in the aqueous phase, flow rate ratio 3:1:1, and UV-cured encapsulated Ag-Pd particles.

[0109] S4. Ice template-foaming: water-paste ratio 0.6, H2O2 1.5wt%, freezing temperature -30°C, forming macropores (200μm, 40%) and mesopores (20nm);

[0110] S5. Vacuum impregnation: vacuum degree 0.08 MPa, impregnation for 2 hours, curing at 70°C and humidity 95% for 18 hours.

[0111] Example 2:

[0112] Component ratio: gypsum matrix 60%, ZIF-8@Pd-Cu (Pd:Cu=1:1) 18%, BiOI / BiVO4@Au (Au:BiVO4=1:10) 12%, Janus particles (Ag-Pd6%) 8%, H2O 22%.

[0113] step:

[0114] S1. Microwave sputtering: precursor concentration 0.2 mol / L, power 600 W, time 30 min, Pd-Cu clusters (2.0 ± 0.2 nm) were obtained;

[0115] S2. Au deposition: sputtering pressure 0.5 Pa, carrier gas flow rate 150 mL / min, Au particle size 60 nm (density 10 particles / μm 2 );

[0116] S3. Janus particles: chitosan concentration 4wt%, PNIPAM crosslinker 0.3wt%, Ag-Pd loading 8%;

[0117] S4. Foaming process: H2O2 2.0 wt%, freezing rate -40°C, macropores 100 μm (50%), mesopores 10 nm;

[0118] S5. Immersion curing: Vacuum degree 0.1 MPa, immersion for 3 hours, 60 ° C, humidity 98% curing for 24 hours.

[0119] Example 3:

[0120] Component ratio: gypsum matrix 70%, ZIF-8@Pd-Cu (Pd:Cu=1:3) 10%, BiVO4@Au (Au:BiVO4=1:20) 8%, Janus particles (Ag-Pd4%) 6%, H2O 22%.

[0121] step:

[0122] S1. Microwave parameters: power 300 W, duration 10 min, cluster size 1.5 ± 0.2 nm;

[0123] S2. Au nanoparticles: deposition temperature 350°C, carrier gas flow rate 50 mL / min, particle size 40 nm;

[0124] S3.Janus particles: PNIPAM prepolymer concentration 5wt%, Ag-Pd molar ratio 1:1;

[0125] S4. Pore structure control: H2O2 0.5wt%, freezing temperature -20°C, macropores 300μm (30%), mesopores 50nm;

[0126] S5. Loading process: vacuum degree 0.05 MPa, immersion for 1 hour, curing for 12 hours at 50°C and 90% humidity.

[0127] Example 4:

[0128] Component ratio: gypsum matrix 55%, ZIF-8@Pd-Cu (Pd:Cu=1:2.5) 20%, BiVO4@Au (Au:BiVO4=1:18) 12%, Janus particles (Ag-Pd7%) 10%, H2O 23%.

[0129] step:

[0130] S1. Precursor solution: ethanol solvent, concentration 0.05 mol / L, microwave power 500 W, sputtering time 25 min;

[0131] S2. Au deposition: sputtering pressure 1.0 Pa, target purity 99.99%, particle size 55 ± 5 nm;

[0132] S3. Interfacial polymerization: chitosan side thickness 30 μm, PNIPAM phase transition temperature LCST = 35°C;

[0133] S4. Dual-stage pore optimization: H2O2 1.0 wt%, macropores 150 μm (45%), mesopores 30 nm;

[0134] S5. Curing conditions: vacuum degree 0.07 MPa, immersion for 2.5 hours, curing for 20 hours at 65°C and humidity 96%.

[0135] Example 5:

[0136] Component ratio: gypsum matrix 75%, ZIF-8@Pd-Cu (Pd:Cu=1:1.5) 12%, BiVO4@Au (Au:BiVO4=1:12) 6%, Janus particles (Ag-Pd4%) 5%, H2O 22%.

[0137] step:

[0138] S1. Quantum cluster: Pd-Cu loading 12 wt%, microwave power 400 W, time 15 min;

[0139] S2.Au distribution: BiVO4 surface particle density 8 particles / μm 2 , LSPR absorption peak 580nm;

[0140] S3. Microparticle encapsulation: Ag-Pd particle size 10 nm, Janus diameter 120 μm;

[0141] S4. Pore design: Ice template macropores 250 μm (35%), mesopores 5 nm;

[0142] S5. Immersion curing: Vacuum degree 0.09 MPa, immersion for 1.5 hours, 55 ° C, humidity 92% curing for 16 hours.

[0143] Comparative Example 1 (corresponding to Example 1):

[0144] Technical solution: Use traditional thermal decomposition method instead of microwave plasma sputtering to prepare Pd-Cu clusters.

[0145] Steps: Pd(acac)2 and Cu(acac)2 ethanol solution (0.1 mol / L) was impregnated into ZIF-8 and calcined at 500°C for 2 hours under nitrogen atmosphere. The cluster size was not controlled, and the Pd-Cu particle size was 5-10 nm with uneven distribution (RSD≥40%).

[0146] Comparative Example 2 (corresponding to Example 2):

[0147] Technical solution: Use conventional immersion method instead of magnetron sputtering to deposit Au nanoparticles.

[0148] Steps: BiVO4 was immersed in HAuCl4 solution (0.01 mol / L) and reduced at 80℃ for 2 hours. The particle size and distribution were not controlled. The Au particles were 80-150nm in size and randomly agglomerated (density ≤ 5 particles / μm). 2 ), no lattice matching interface is formed.

[0149] Comparative Example 3 (corresponding to Example 3):

[0150] Technical solution: Single-layer chitosan microspheres are used to replace the Janus structure, without the dual temperature and humidity response function.

[0151] Steps: Chitosan solution (3 wt%) was used to prepare monolayer microspheres (diameter 50-200 μm) by emulsification method, and Ag-Pd particles were directly mixed (without encapsulation) without introducing PNIPAM temperature-sensitive components.

[0152] Comparative Example 4 (corresponding to Example 4):

[0153] Technical solution: Only ice template method is used to form pores, chemical foaming step is omitted, and there is no mesoporous structure.

[0154] Steps: Gypsum slurry (water-to-paste ratio 0.6) is frozen (-30°C) to form an ice template, without adding H2O2 foaming agent, with a single pore structure (macropores 200-300μm, no mesopores), and a specific surface area ≤5m 2 / g.

[0155] Comparative Example 5 (corresponding to Example 5):

[0156] Technical solution: Use mechanical mixing instead of vacuum impregnation to load functional components.

[0157] Steps: ZIF-8@Pd-Cu, BiVO4@Au and Janus particles were directly dry-mixed with gypsum powder at a water-to-paste ratio of 0.6. Vacuum impregnation and wet heat curing were not used, and the functional components were only attached to the gypsum surface (loading depth ≤ 50μm).

[0158] Experiment 1: Comparison of quantum cluster size and catalytic activity:

[0159] Experimental description:

[0160] Samples: Example 1 (microwave sputtering Pd-Cu / ZIF-8) and Comparative Example 1 (pyrolysis Pd-Cu / ZIF-8), 3 batches of each were prepared.

[0161] step:

[0162] Cluster characterization: 50 mg of sample was dispersed in ethanol, sonicated for 30 min, and dropped onto a copper grid. TEM images were taken (accelerating voltage 200 kV), and the sizes of 200 particles were counted. The grain size was calculated using XRD (CuKα radiation) (Scherrer formula).

[0163] Catalytic test: fixed bed reactor (10 mm inner diameter), loaded with 1 g catalyst, introduced formaldehyde (50 ppm, 50% humidity), space velocity 30000 h -1 , detect the outlet concentration (GC-MS) and calculate the k value (first-order kinetic fitting).

[0164] Stability: The assay was run continuously for 24 hours, with samples taken every 2 hours to detect activity and calculate the decay rate (Δk / k0×100%).

[0165] The final experimental data are shown in Table 1 below:

[0166] Table 1

[0167]

[0168] Microwave plasma sputtering technology uses high-energy electrons to dissociate the precursor, anchoring atomically dispersed Pd-Cu clusters on the ZIF-8 surface. The quantum size effect (1.7-2.1 nm) significantly increases the d-band center position, optimizes the adsorption energy of formaldehyde molecules (DFT calculation ΔE = 0.8 eV), and transforms the reaction pathway from the Langmuir-Hinshelwood mechanism to the Eley-Rideal mechanism, with an apparent rate constant (k≈0.21s -1 ) Pyrolysis coarsened particles (k≈0.05s -1 ) increased by more than 3 times.

[0169] The long-term high-temperature calcination in the traditional pyrolysis method induces Ostwald ripening, and the Pd-Cu particles grow to 5-8nm, and the specific surface area plummets (BET from 950→300m 2 / g). Large particles lead to a reduction in active sites and oxidation of the Cu surface to form an inert CuO phase (XPS shows Cu 2+ Accounting for ≥60%), which seriously restricts the efficiency of the formaldehyde adsorption-oxidation cycle.

[0170] The athermal effect of microwave sputtering inhibits metal migration, forming a Pd-Cu alloy at the bimetallic interface (verified by HAADF-STEM), synergistically lowering the O2 activation energy barrier (Ea = 45 → 28 kJ / mol). During continuous operation, Example 1 maintained stable cluster size (Δd ≤ 0.3 nm), while Comparative Example 1 experienced a dramatic drop in activity (decay rate > 30%) due to particle sintering (TEM revealed neck connections).

[0171] Experiment 2: Au particle distribution and LSPR effect verification:

[0172] Experimental description:

[0173] Samples: Example 2 (magnetron sputtering Au / BiVO4) and Comparative Example 2 (immersion reduction Au / BiVO4), 5 area samples were taken for each.

[0174] step:

[0175] Morphology analysis: The sample was gold-sprayed (5 nm), and SEM was scanned at 10 kV. Five fields of view (50 × 50 μm) were randomly selected to calculate the particle density and particle size.

[0176] Optical testing: UV-Vis-NIR spectrometer (wavelength 300-1000 nm) with integrating sphere accessory to measure absorbance and extract LSPR peak wavelength (λ_max) and full width at half maximum (FWHM);

[0177] Dark Catalysis: Sealed Chamber (1m 3 ) injection of formaldehyde (initial concentration 2.0 mg / m 3 ), no light source, constant temperature and humidity (25℃, 50%RH), detect the residual concentration after 24 hours, and calculate the degradation rate.

[0178] The final experimental data are shown in Table 2 below:

[0179] Table 2

[0180]

[0181]

[0182] The magnetron sputtering process precisely controls the crystal orientation of the Au nanoparticles. The lattice mismatch (24.7%) between the BiVO4(040) plane and the Au(111) plane induces an interfacial stress field, promoting the migration of hot electrons from the Au to the BiVO4 conduction band. The LSPR absorption peak blue-shifts to 568nm (compared to 628nm in Comparative Example 2), the half-width is compressed to 82nm, and the local electric field strength increases fivefold (FDTD simulation). The formaldehyde degradation rate in the dark state exceeds 60%.

[0183] The Au particles synthesized by the immersion reduction method are coarse and randomly distributed. Large particles (100 nm) cause a red shift in the LSPR, and the broadening effect (FWHM > 140 nm) weakens the resonant energy transfer efficiency. The presence of an amorphous layer at the Au-BiVO4 interface (confirmed by TEM-EDS scanning) increases the carrier recombination rate and plummets the quantum efficiency to less than 20%.

[0184] Lattice-matched interfaces are central to dark-state catalysis. In Example 2, the Au (111) surface exposure ratio reaches 85% (XRD texture coefficient), the surface plasmon oscillation direction aligns with the BiVO4 band structure, and the hot electron injection efficiency is increased to 45% (TRPL lifetime shortened from 2.1ns to 0.8ns). In contrast, the Au particles in Comparative Example 2 are disordered, and the interface barrier hinders electron transfer, nearly eliminating catalytic activity.

[0185] Experiment 3: Verification of Janus particle responsiveness and anti-mildew effect:

[0186] Experimental description:

[0187] Samples: Example 3 (Janus structure Ag-Pd microparticles) and Comparative Example 3 (single-layer chitosan microspheres), 5 sets of parallel samples were prepared for each.

[0188] step:

[0189] Dynamic release: The sample is placed in a temperature and humidity alternating chamber ( Switching every 30 minutes), sampling every 2 hours, and ICP-MS quantification of Ag + Release amount;

[0190] Antibacterial test: Aspergillus niger spore suspension (1×10 6 CFU / mL) were coated on PDA culture medium, sample pieces (10 mm in diameter) were placed, and cultured at 25°C for 48 h. The edge clarity and diameter of the inhibition zone were measured;

[0191] Dynamic matching: Synchronous monitoring of Ag + Release rate and formaldehyde degradation rate (concentration in the chamber 0→50ppm), calculation of response lag time (Δt) and synergy coefficient (R 2 ).

[0192] The final experimental data are shown in Table 3 below:

[0193] Table 3

[0194]

[0195] When the humidity of the Janus microparticles increases, the chitosan-PNIPAM asymmetric structure will cause the chitosan side to swell faster (expansion rate 300%) than the PNIPAM side (LCST triggers contraction), and the internal Ag-Pd particles will be released in a directional manner driven by the pressure difference. + The release rate instantly increased to 2.3 μg / h·cm 2 , accurately matching the peak of mold reproduction, the diameter of the inhibition zone exceeds 18mm, achieving cross-level inhibition compared to single-layer microspheres (≤11mm).

[0196] The static release mode of single-layer chitosan microspheres leads to Ag + Premature exhaustion. Under temperature and humidity fluctuations, the microspheres swell and shrink isotropically, leading to disordered leakage of Ag-Pd particles (release rate fluctuations >50%) and intermittent antibacterial activity. Aspergillus niger rapidly colonizes during the intermittent period (the edges of the inhibition zone become blurred, and hyphae density increases fourfold), significantly reducing antifungal efficacy.

[0197] The dual-response mechanism of Janus particles confers dynamic synergy, and the spatiotemporal coupling of PNIPAM phase transition temperature (LCST = 35 ° C) and chitosan humidity response enables Ag + Release curve (R 2 =0.91) is highly synchronized with the change in formaldehyde concentration. 2 <0.6, lag time Δt>2 hours, anti-mildew and catalysis are seriously disconnected, and the functional components "fight on their own", dragging down the overall performance.

[0198] Experiment 4: Evaluation of mass transfer efficiency and mechanical strength of double-stage pores:

[0199] Experimental description:

[0200] Samples: Example 4 (ice template + chemical foaming) and Comparative Example 4 (single ice template), each cut into 5 test pieces (20×20×20 mm).

[0201] step:

[0202] Pore structure characterization: Mercury porosimetry (pressure 0.1-200 MPa) was used to determine the total porosity, and fractal dimension analysis was used to analyze the proportion of macropores (50 μm) and mesopores (2-50 nm).

[0203] Mass transfer test: A mixture of formaldehyde (50 ppm) and N2 was introduced (flow rate 0.5 L / min). The concentration gradient within the pores was measured every 10 minutes, and the effective diffusion coefficient (D_eff) was fitted using Fick's law.

[0204] Mechanical testing: A universal testing machine (loading rate 1 mm / min) was used to apply vertical pressure until the specimen ruptured, and the peak stress (compressive strength) was recorded.

[0205] The final experimental data are shown in Table 4 below:

[0206] Table 4

[0207]

[0208]

[0209] The coupling strategy of ice template and chemical foaming breaks the limitations of traditional pore design. The macropores (200-300μm) dominated by ice crystal growth build a high-speed gas diffusion skeleton. The nanobubbles produced by H2O2 decomposition are squeezed and deformed by ice crystals to form a 2-50nm mesoporous network (BET specific surface area>30m 2 / g). Under the cooperation of dual-level pores, formaldehyde molecules undergo cascade transfer of Knudsen diffusion (macroporous) and surface adsorption (mesopores) in the pores, and the effective diffusion coefficient exceeds 2.0×10 -6 m 2 / s, compared with the single ice template (D_eff≈0.7×10 -6 m 2 / s) increased by nearly 3 times.

[0210] The single ice template process has too high a proportion of macropores (65%), and the pore wall thickness is sharply reduced to 10-20μm (SEM tomography). The continuity of the gypsum matrix is destroyed, stress is concentrated at the pore-strut nodes (finite element simulation shows local stress >15MPa), and the compressive strength plummets to below 3MPa. In Example 4, the matrix skeleton density is increased (porosity 70% vs 65%) by filling the macropore gaps with mesopores, and the mechanical properties are enhanced against the trend.

[0211] The chemically foamed mesoporous network serves not only as a mass transfer channel but also as a mechanical reinforcement unit. The nanoscale pore walls form a microtruss structure (validated by the Gibson-Ashby model), distributing external loads and maintaining a stable compressive strength of 5 MPa. In contrast, the single-aperture system in Example 4 exhibits interpenetrating macropores but lacks support, hindering both mechanical and mass transfer performance, demonstrating the irreplaceable superiority of the dual-aperture design.

[0212] Experiment 5: Load stability and cycle life verification:

[0213] Experimental description:

[0214] Samples: Example 5 (vacuum impregnation + wet heat curing) and Comparative Example 5 (mechanical mixing), 3 sets of test specimens (10×10×10 mm) were taken for each.

[0215] step:

[0216] Load depth analysis: Cut the sample cross section and use SEM-EDS line scan (step size 1 μm) to detect the concentration gradient of Pd and Cu elements from the surface to 500 μm inside;

[0217] Cyclic oxidation test: The sample was placed in a formaldehyde degradation reactor (50 ppm, humidity 60%) and run for 5 consecutive times (24 hours each time). XPS was used to determine the Pd 0 / Pd 2+ Proportion;

[0218] Determination of shedding rate: The sample was immersed in deionized water and ultrasonically cleaned (40 kHz, power 100 W) for 30 minutes. The concentrations of Pd and Cu ions in the solution were quantified by ICP-OES.

[0219] The final experimental data are shown in Table 5 below:

[0220] Table 5

[0221]

[0222] The negative pressure environment (0.09 MPa) of vacuum impregnation forces the functional components to penetrate along the capillaries of the gypsum matrix. The Pd-Cu clusters are "pushed" into the matrix 400 μm deep (only 50 μm in comparative example 5) by the hydraulic gradient, forming a three-dimensional interwoven load network. The wet heat curing (55 ° C / 92% RH) triggers the dihydration reaction of gypsum, and the microcrystals grow and wrap around the clusters. After 5 cycles, the Pd 0 The proportion is still >80%, and the metal active phase is highly retained.

[0223] The dry process of mechanical mixing causes the functional components to float on the surface. Under ultrasonic vibration, the loosely attached particles are peeled off in pieces (the shedding rate is >10μg / cm 2 ), the exposed gypsum matrix cannot provide an anchoring point. XPS shows that the Pd 2+ It accounts for more than 60%, and surface oxidation passivation directly kills the catalytic activity.

[0224] The dual locking effect of capillary forces and crystal wrapping is key to load stability. In Example 5, Pd-Cu clusters are embedded in the gaps between gypsum whiskers (SEM shows whisker diameter ≈200nm). Physical entrapment and chemical bonding (FTIR detection of the OH coordination peak) synergistically protect against external impacts. In contrast, the components in Comparative Example 5 have a "duckweed-like" distribution, and even the slightest disturbance triggers catastrophic failure.

[0225] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A mildew-proof and formaldehyde-removing gypsum, characterized in that: It includes the following components in proportion by mass: Gypsum matrix: 50-65 parts; Metal-organic framework-supported bimetallic catalyst: 10-25 parts; Visible light responsive semiconductor heterojunction: 8-15 copies; Slow-release mildew inhibitor: 3-10 parts; Reinforcement fiber: 2-8 parts; Additives: 1-5 parts.

2. The mold-proof and formaldehyde-removing gypsum according to claim 1, characterized in that: The gypsum matrix is industrial by-product phosphogypsum or desulfurized gypsum, the purity of its beta-hemihydrate gypsum is ≥85%, and soluble impurities are removed by acid washing.

3. The mold-proof and formaldehyde-removing gypsum according to claim 1, characterized in that: The metal organic framework-supported bimetallic catalyst is a Pd-Cu quantum cluster supported on a ZIF-8 carrier, the molar ratio of Pd to Cu is 1:1-1:3, and the cluster size is 1.5-2.2 nm.

4. The mold-proof and formaldehyde-removing gypsum according to claim 1, characterized in that: The visible light responsive semiconductor heterojunction is a BiOI / BiVO4 core-shell structure, with Au nanoparticles deposited on its surface. The particle size of the Au nanoparticles is 40-60 nm, and the mass ratio of Au to BiVO4 is 1:10-1:

20.

5. The mold-proof and formaldehyde-removing gypsum according to claim 1, characterized in that: The slow-release mildew inhibitor is chitosan / poly N-isopropylacrylamide Janus microparticles, which encapsulate Ag-Pd bimetallic particles. The diameter of the Janus microparticles is 50-200 μm, and the LCST of PNIPAM is 30-40° C.

6. The mildew-proof and formaldehyde-removing gypsum according to claim 1, characterized in that: The reinforcing fiber is silicon carbide whisker with a fiber diameter of 0.5-2 μm and an aspect ratio of ≥20:1; the auxiliary agent includes sodium polyacrylate and citric acid with a mass ratio of 1:0.5-1:

2.

7. A method for preparing the mildew-proof and formaldehyde-removing gypsum according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Pd-Cu quantum clusters were loaded on ZIF-8 support by microwave plasma sputtering, with microwave power of 300-600 W and precursor solution concentration of 0.05-0.2 mol / L; S2, depositing Au nanoparticles on the BiOI / BiVO4 surface by chemical vapor deposition at a deposition temperature of 300-400°C and a carrier gas flow rate of 50-150 mL / min; S3, chitosan / PNIPAMJanus microparticles were prepared by microfluidic interfacial polymerization and encapsulated with Ag-Pd bimetallic particles; S4, mixing the gypsum matrix with the functional components, and forming the mixture using an ice template-chemical foaming synergistic pore-forming process, with a freezing temperature of -20 to -40°C and a foaming agent H2O2 added in an amount of 0.5-2.0 wt%; S5. The functional components are loaded into the gypsum matrix by vacuum impregnation with a vacuum degree of 0.05-0.1 MPa for 1-3 hours, followed by curing at 50-70° C. and a humidity of 90-98%.

8. The preparation method according to claim 7, characterized in that In S1, the precursors of the Pd-Cu quantum cluster are Pd(acac)2 and Cu(acac)2, the solvent is ethanol, and the microwave sputtering time is 10-30 minutes.

9. The preparation method according to claim 7, characterized in that In S2, the purity of the Au nanoparticle deposition target is 99.99%, and the sputtering gas pressure is 0.5-1.0 Pa.

10. The preparation method according to claim 7, characterized in that In S4, the ice template-chemical foaming process forms a dual-level pore structure of macropores and mesopores, wherein the pore size of the macropores is 100-300 μm, the pore size of the mesopores is 2-50 nm, and the macropores account for 30-50%.

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