Preparation method and application of biomass carbon-coated heteropolyacid hydrogen salt catalyst

Abstract

The present invention discloses a preparation method and application of a biomass carbon-coated heteropolyacid hydrogen salt catalyst. The preparation method is carried out in a sealed container. A heteropolyacid hydrogen salt, a biomass polysaccharide precursor, and a polar organic solvent are added, reacted at 120-180°C, and then dried to obtain the biomass carbon-coated heteropolyacid hydrogen salt catalyst. The preparation method of the present invention is simple, the conditions are controllable, the composite structure is stable, and the cost is low. The prepared biomass carbon-coated heteropolyacid hydrogen salt catalyst has both strong oxidizing and reducing properties and can also be adjusted for proton transfer, thus having good photocatalytic performance and can be used for photocatalytic oxygen reduction and oxidative removal of formaldehyde in air.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a biomass carbon-coated heteropolyacid hydrogen salt catalyst, belonging to the technical field of heteropolyacid composite material preparation. Background Art

[0002] Semiconductor photocatalysis is an environmentally friendly, energy-efficient, and safe method for synthesizing economically valuable substances (such as hydrogen peroxide) and removing pollutants from the environment (such as formaldehyde). However, this technology suffers from low photocatalytic efficiency and poor target reaction performance, leading to high industrial production costs. Therefore, the development of efficient photocatalysts is a major goal for chemical upgrading and environmental remediation under renewable energy systems.

[0003] Biomass carbon is a widely available, cheap, and highly efficient photocatalyst with good adsorption capacity. Hu Zhuofeng et al. used sulfuric acid-assisted hydrothermal carbonization to convert biomass such as cellulose, sucrose, starch, and cardboard into hydrothermal carbon and used it for photocatalytic removal of chromium (VI) and synthesis of hydrogen peroxide (Appl. Catal., B 2021, 295, 120253.;ACS Catal.2021, 11 (23), 14480-14488.), and in 2020 announced a method for preparing carbon dioxide reduction photocatalyst using hyperaccumulator plants (CN111111660B). Kang Zhenhui used sulfuric acid-assisted hydrothermal carbonization to convert cellulose, quercetin, hesperidin, glucan, etc. into hydrothermal carbon and used it for photocatalytic synthesis of hydrogen peroxide (Nano Res. 2022, 15 (5), 4000-4007;Catal. Sci. Technol. 2022, 12 (6), 1837-184;Appl. Catal., B 2022, 319,121944;J. Mater. Chem. A 2022, 10 (28), 15074-15079). However, the use of inorganic acids in sulfuric acid-assisted hydrothermal carbonization requires the recovery and disposal of waste acid. Hydrothermal carbon catalysts suffer from poor oxidation performance and rapid recombination of photogenerated carriers during the photocatalytic process, resulting in poor catalytic performance. Furthermore, the photocatalytic process is limited by a mismatch between the oxidation and reduction reaction rates, resulting in a low proton transfer rate.

[0004] Heteropolymetallic oxide metal complexes (heteropolyacids, POMs) are molecular-type semiconductors with a LUMO-HOMO energy level difference comparable to that of semiconductors. They also possess strong oxidizing ability, excellent electron and proton carrying and releasing capabilities, and multi-electron reversible redox properties. However, heteropolyacids have high solubility in polar solvents and are not easily complexed with semiconductor materials. In order to enhance the stable binding of heteropolyacids and semiconductors, Liu Jiquan et al. reported a method for forming a heterojunction catalyst of Keggin-type sparingly soluble heteropolyacid hydrogen salt and bismuth-based semiconductors (Adv. Mater. Interfaces, 2022, 9(11), 202102031; CN113398994), which was applied to photocatalytic nitrogen reduction and oxygen reduction. During the preparation process, the bismuth-based semiconductor is deposited and grown on the surface of the Keggin-type sparingly soluble heteropolyacid hydrogen salt, and the binding force exists on the outer surface of the Keggin-type sparingly soluble heteropolyacid salt particles. However, during the photocatalytic oxygen reduction reaction to synthesize hydrogen peroxide, metal oxide semiconductors cause in-situ decomposition of hydrogen peroxide, which is not conducive to the formation of hydrogen peroxide. In addition, it cannot be used for formaldehyde oxidation removal reaction.

[0005] Therefore, there is an urgent need to develop a composite photocatalyst that is simple to prepare, has a wide range of raw materials, possesses both strong oxidizing and reducing properties, and can promote proton transport. Furthermore, there is a need for a composite photocatalyst that can firmly bond the composite structure from the inside of the particles to the surface of the microcrystals and slow the in-situ decomposition of hydrogen peroxide. Summary of the Invention

[0006] The present invention aims to provide a preparation method and application of a biomass carbon-coated heteropolyacid hydrogen salt catalyst with excellent photocatalytic performance.

[0007] The implementation process of the present invention is as follows:

[0008] A method for preparing a biomass carbon-coated heteropolyacid hydrogen salt, characterized by comprising the following steps:

[0009] (1) dispersing a biomass polysaccharide precursor X in a polar organic solvent or a mixed solution of a polar organic solvent and water to obtain a dispersion system I, wherein the mass volume ratio of the biomass polysaccharide precursor X to the polar organic solvent or the mixed solution of the polar organic solvent and water is 0.01-0.2 g / mL;

[0010] The biomass polysaccharide precursor X is selected from cellulose, hemicellulose, cyclodextrin, dextran, chitosan or starch.

[0011] The dispersion refers to the formation of a dispersion system, such as a solution, a colloid, a suspension, and an emulsion, including partial dissolution or complete dissolution, such as cyclodextrin can be completely or partially dissolved in DMF, or in a DMF-H2O mixed solution;

[0012] (2) Dispersing the heteropolyacid hydrogen salt H-POMs in a polar organic solvent or a mixed solution of a polar organic solvent and water to form dispersion system II, wherein the mass volume ratio of H-POMs to the polar organic solvent or the mixed solution of the polar organic solvent and water is 0.001-0.05 g / mL;

[0013] The mass ratio of the heteropolyacid hydrogen salt H-POMs to the biomass polysaccharide precursor X is 0.01 to 0.5, wherein the anion of the heteropolyacid hydrogen salt H-POMs is selected from Keggin type, Dawson type or Weakley type heteropolyacid, and the cation of the heteropolyacid hydrogen salt H-POMs is selected from Cs + , Ag + , Ba 2+ , Ce 3+ , Ru 2+ or Ir 3+ N / C-containing complex cations, quaternary ammonium ions or imidazolium ions, where the proton H of H-POM + The number is an integer or decimal between 1 and 2;

[0014] Ru 2+ or Ir 3+ The N / C-containing cation is selected from [Ru(bpy)3] 2+ (bpy is 2,2'-bipyridine), [Ru(dmb)3] 2+ (dmb is 5,5'-dimethyl-2,2'-bipyridine), [Ru(bpz)3] 2+ (bpz is 2,2′-bipyrazine), [Ru(phen)3] 2+ (phen is 1,10-phenanthroline, 1,10-phenanthroline), [Ru(bpm)3] 2+ (bpm is 2,2′-bipyrimidine), [Ru(phd)3] 2+ (PhD is 1,10-phenanthroline-5,6-dione), [Ru(bpy)3] 2+ (bpy is 2,2'-bipyridine), [Ru(bpy)2(phen-5-NH2)] 2+ (bpy is 2,2'-bipyridine, phen-5-NH2 is 5-amino-1,10-phenanthroline), [Ru(dphphen)3] 2+ (dphphen is 4,7-diphenyl-1,10-phenanthroline), [Ir(ppy)2(bpy)] + (ppy is 2-phenylpyridine), [Ir(ppy)2(phen)] + 、[Ir(ppy)2(dphphen)] +、[Ir(ppy)2(dtbbpy)] + (dtbbpy is 4,4-di-tert-butyl-2,2′-bipyridine), [Ir(F-mppy)2(bpy)] + (F-mppy is 2-(4-fluorophenyl)pyridine), [Ir(F-mppy)2(phen)] + 、[Ir(F-mppy)2(dphphen)] + 、[Ir(dFppy)2(dtbbpy)] + (dFppy is 2-(2,4-difluorophenyl)pyridine), [Ir(dF(CF3)ppy)2(dtbbpy)] + (dF(CF3)ppy is 2-(2,4-difluorophenyl)-5-trifluoromethylpyridine), [Ir(dF(Me)ppy)2(dtbbpy)] + (dF(Me)ppy is 2-(2,4-difluorophenyl)-5-trimethylpyridine), Ir[(dFppy)2(4,4′-dCF3bpy)] (4,4′-dCF3bpy is 4,4′-bis(trifluoromethyl)-2,2′-bipyridine), Ir[4-t-bu-phenyl-4-t-bu-py]2(dtbpy)] (4-tbphenyl-5-t-bu-py is 2-(4-tert-butylphenyl)-4-tert-butylpyridine, dtbpy is tert-butyl-4,4′-di-tert-butyl-2,2′-bipyridine), [Ir[Me(Me)ppy]2(dtbpy)] + (Me(Me)ppy is 2-(4-methylphenyl)-4-methylpyridine), Ir[(dFMeppy)2(4,4′-dCF3bpy)] + 、[Ir(dFppy)2(dtbpy)] + 、Ir[(FCF3(CF3)ppy)2(dtbpy)] + (FCF3(CF3)ppy is 2-(2-fluoro-4-trifluoromethylphenyl)-5-trifluoromethylpyridine), Ir[(dFOMeppy)2(5,5'-dCF3bpy)] + (dFOMeppy is 2-(2,4-difluorophenyl)-5-methoxypyridine), Ir[(dFMeppy)2(dtbpy)] + .

[0015] The quaternary ammonium salt ion is selected from alkyl trimethylammonium, alkyl triethylammonium, alkyl tripropylammonium, and alkyl tributyl, wherein the alkyl group is octyl, dodecyl, tetradecyl, hexadecyl, or octadecyl. The quaternary ammonium salt ion includes octyl trimethyl ammonium ion, octyl triethyl ammonium ion, octyl tripropyl ammonium ion, octyl tributyl ammonium ion, dodecyl trimethyl ammonium ion, dodecyl triethyl ammonium ion, dodecyl tripropyl ammonium ion, dodecyl tributyl ammonium ion, tetradecyl trimethyl ammonium ion, tetradecyl triethyl ammonium ion, tetradecyl tripropyl ammonium ion, tetradecyl tributyl ammonium ion, hexadecyl trimethyl ammonium ion, hexadecyl triethyl ammonium ion, hexadecyl tripropyl ammonium ion, hexadecyl tributyl ammonium ion, octadecyl trimethyl ammonium ion, octadecyl triethyl ammonium ion, octadecyl tripropyl ammonium ion, or octadecyl tributyl ammonium ion.

[0016] The imidazolium salt ion is selected from:

[0017] 1,3-substituted imidazolium ions: when the 1,3-position substituents are different, the 1-position substituent is octyl, dodecyl, tetradecyl, hexadecyl or octadecyl, and the 3-position substituent is methyl, ethyl, propyl or butyl; when the 1,3-position substituents are the same, the substituent is octyl, dodecyl, tetradecyl, hexadecyl or octadecyl;

[0018] When there are substituents at positions 1, 2, and 3, the substituent at position 1 is octyl, dodecyl, tetradecyl, hexadecyl, or octadecyl, and the substituents at positions 2 and 3 are methyl. These include: 1-octyl-3-methylimidazolium ion, 1-octyl-3-ethylimidazolium ion, 1-octyl-3-propylimidazolium ion, 1-octyl-3-butylimidazolium ion, 1-dodecyl-3-methylimidazolium ion, 1-dodecyl-3-ethylimidazolium ion, 1-dodecyl-3-propylimidazolium ion, 1-dodecyl-3-butylimidazolium ion, 1-tetradecyl-3-methylimidazolium ion, 1-tetradecyl-3-ethylimidazolium ion, 1-tetradecyl-3-propylimidazolium ion, 1-tetradecyl-3-butylimidazolium ion, 1-hexadecyl-3-methylimidazolium ion, 1-hexadecyl-3-ethylimidazolium ion, 1-hexadecyl-3-propylimidazolium ion imidazolium, 1-hexadecyl-3-butylimidazolium ion, 1-octadecyl-3-methylimidazolium ion, 1-octadecyl-3-ethylimidazolium ion, 1-octadecyl-3-propylimidazolium ion, 1-octadecyl-3-butylimidazolium ion, 1,3-dioctylimidazole, 1,3-didodecylimidazole, 1,3-ditetradecylimidazole, 1,3-dihexadecylimidazole, 1,3-dioctadecylimidazole, 1-octyl-2,3-dimethylimidazole, 1-dodecyl-2,3-dimethylimidazole, 1-tetradecyl-2,3-dimethylimidazole, 1-hexadecyl-2,3-dimethylimidazole, 1-octyl-2,3-dimethylimidazole;

[0019] The polar organic solvent is selected from acetonitrile, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and formamide, and the volume ratio of the polar organic solvent to water is greater than or equal to 1:1, usually less than or equal to 10:1, and in extreme cases is 20:1;

[0020] (3) Dispersion II and dispersion I were thoroughly mixed under ultraviolet light irradiation in the wavelength range of 320-405 nm;

[0021] UV irradiation can promote the dispersion of H-POMs and enhance their interaction with biomass precursor X, and the irradiation time is maintained for 1 to 6 h;

[0022] (4) The mixed dispersion was transferred into a sealed container and allowed to fully react in an oxygen-free environment at 120-180°C to obtain biomass carbon-coated heteropolyacid hydrogen salt H-POMs@BC(X).

[0023] During the solvothermal reaction, an oxygen-free inert gas or reducing gas is introduced to reduce the contact of the biomass polysaccharide precursor X with oxygen and prevent it from being oxidized during the reaction. The inert atmosphere or reducing atmosphere can be nitrogen, argon, carbon dioxide, hydrogen, a hydrogen-nitrogen mixture, or a hydrogen-argon mixture.

[0024] The solvothermal reaction, which takes place at 120-180°C for 1-72 hours, involves H-POMs catalyzing the dissolution, depolymerization, and isomerization of a biomass precursor X (such as cellulose, hemicellulose, cyclodextrin, glucan, chitosan, or starch). This is followed by polycondensation on the surface of the H-POM microcrystals, which then grow outward to form a biomass carbon coating (BC(X)), known as the H-POMs@BC(X) structure. This is based on the pseudo-liquid-phase catalytic behavior of the heteropolyacid hydrogen salt, allowing the process to occur within the H-POM microcrystals, resulting in an inside-out polymerization growth model. The depolymerization process involves β-1,4-glycosidic bond cleavage to form soluble oligomers containing glucose or fructose units. The isomerization process involves the conversion of glucose or fructose units to furan units (or furfural). During the polycondensation process, the furan units (or furfural) repolymerize to form a polyfuran structure, resulting in a product suspension.

[0025] The biomass carbon-coated heteropolyacid hydrogen salt prepared by catalysis-self-assembly is a core-shell structure with the general structural formula H-POMs@BC(X), with H-POMs as the core, BC(X) as the biomass carbon shell, and X as the biomass precursor raw material. The surface hydroxyl or carbonyl group of the biomass carbon BC(X) and the terminal metal oxygen bond of the heteropolyacid hydrogen salt H-POMs form a stable organic-inorganic core-shell structure through covalent interaction. H-POMs is a crystalline structure while BC(X) is an amorphous structure.

[0026] This invention uses heteropolyacid hydrogen salts as templates and catalysts, allowing biomass precursors to depolymerize and recondense on the surface of microcrystals within their particles, growing outward to form an organic-inorganic heterojunction material, thereby enhancing its photocatalytic performance. The biomass carbon-coated heteropolyacid hydrogen salts prepared by this invention can be used as photocatalysts, specifically for photocatalytic oxygen reduction and formaldehyde oxidation.

[0027] Photocatalytic oxygen reduction reaction: The oxygen reduction reaction is carried out in pure water at a pressure of 0.1-1.0 MPa without electrolytes. The catalyst is suspended in the water or coated on the inner wall of the reactor. The reactant gas and water flow into the reactor or are enclosed in the reactor. The reaction temperature is 0-80°C. The photocatalytic reaction occurs in the ultraviolet-visible-near-infrared range, and the light source includes sunlight or artificial light (such as xenon lamps, tungsten lamps, mercury lamps, LEDs, etc.).

[0028] Formaldehyde oxidation reaction: The formaldehyde oxidation reaction occurs in a vapor-containing gas phase with a relative humidity range of 40% to 100%. The catalyst is coated on the inner wall of the reactor or filled in the reactor. The reactant gas flows into the reactor and the reaction proceeds at 0-80°C. The photocatalytic reaction occurs in the ultraviolet-visible-near-infrared range, and the light source includes sunlight or artificial light (such as xenon lamps, tungsten lamps, mercury lamps, LEDs, etc.).

[0029] The method of the present invention features a simple preparation process, mild conditions, a stable composite structure, and very low cost. The prepared biomass carbon-coated heteropolyacid hydrogen salt catalyst exhibits excellent photocatalytic properties and is applicable to oxygen reduction synthesis of hydrogen peroxide and oxidative removal of formaldehyde from air. The construction of the biomass carbon-coated heteropolyacid hydrogen salt catalyst simultaneously maintains the strong oxidizing properties of the heteropolyacid hydrogen salt and the strong reducing properties of the biomass carbon. The heteropolyacid hydrogen salt acts as a proton reservoir (i.e., a "proton sponge"), accommodating protons from the oxidation half-reaction and transferring them to the catalytic sites of the reduction half-reaction, promoting the proton-coupled electron transfer process. By promoting proton transfer through the heteropolyacid hydrogen salt and coordinating the oxidation-reduction half-reaction, the catalyst's activity is enhanced by simultaneously promoting both half-reactions. Furthermore, the biomass carbon coating of the heteropolyacid hydrogen salt effectively mitigates the in-situ decomposition of hydrogen peroxide, enhancing its catalytic activity.

[0030] The beneficial effects of the present invention are as follows: (1) The raw materials of the method of the present invention are widely available, cheap and easy to obtain, and the preparation process is simple. (2) The prepared biomass carbon-coated heteropolyacid hydrogen salt catalyst is a biomass precursor X that undergoes depolymerization, isomerization and re-condensation on the surface of heteropolyacid hydrogen salt H-POMs to form a coating layer, wherein the isomerization and re-condensation processes are carried out in the microcrystals inside the H-POMs particles, and polymerization from the inside to the outside forms a core-shell structure. (3) The prepared biomass carbon-coated heteropolyacid hydrogen salt catalyst has light absorption performance in the ultraviolet-visible-near infrared range, and the biomass carbon layer has a high-density π electron defect structure, which is conducive to the adsorption and activation of reactant molecules. (4) The prepared biomass carbon-coated heteropolyacid hydrogen salt catalyst has good photocatalytic activity, oxygen reduction to prepare hydrogen peroxide, and oxidation of formaldehyde to carbon dioxide. (5) In the prepared biomass carbon-coated heteropolyacid hydrogen salt catalyst, the surface hydroxyl groups (and carbonyl groups) on the biomass carbon BC(X) interact with the terminal metal oxygen bonds of the heteropolyacid hydrogen salt H-POMs through covalent interactions and act on the microcrystals inside the heteropolyacid hydrogen salt particles, thereby showing extremely strong stability and almost no loss of heteropolyacid molecules during the photocatalytic process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 TEM image of Example 1 of the present invention;

[0032] Figure 2 1 and 2 are XRD patterns of Examples 2 and 11 of the present invention;

[0033] Figure 3 FT-IR diagram of Example 9 of the present invention;

[0034] Figure 4 This is the SEM image of Example 10 of the present invention. DETAILED DESCRIPTION

[0035] Below in conjunction with specific embodiment of the present invention, technical solution of the present invention is clearly and completely described, and it is obvious that described embodiment is only a part of embodiment of the present invention, rather than whole embodiment.The reagent, method and equipment adopted in the present invention are conventional reagents, methods and equipment in the art.Based on the embodiment in the present invention, the every other embodiment that those of ordinary skill in the art obtain under the premise of not making creative work, all belong to the scope of protection of the present invention.

[0036] Examples 1 to 4 are methods for preparing biomass carbon-coated Dawson-type heteropolyacid hydrogen salt catalysts. Example 1

[0037] 1.0 g of starch was dispersed in 10 mL of acetonitrile-water (V 乙腈 :V 水= 2:1), stirred with ultrasound for 1 h to obtain dispersion I. 0.1 g of Dawson type phosphotungstate containing tetradecyltrimethylammonium ([N + (CH3)3( n -C 14 H 29 )]4H2P2W 18 O 62 ) were dispersed in 2 mL of acetonitrile-water (V 乙腈 :V 水 = 2:1) mixed solvent, stirred and ultrasonicated for 3 h to obtain dispersion II. Under the irradiation of ultraviolet light with a wavelength range of 320-405 nm and a power of 10 W, [N + (CH3)3( n -C 14 H 29 )]4H2P2W 18 O 62 Dispersion II was added to starch dispersion I and irradiated for 1 h. Subsequently, it was transferred to a closed reactor, filled with 0.1 MPa argon, and stirred for thermal reaction at 150°C for 12 h. The sample was then washed three times with water and ethanol, and dried in a drying oven at 40°C for 12 h to obtain [N + (CH3)3( n -C 14 H 29 )]4H2P2W 18 O 62 @BC (starch) catalyst. Its morphology and structure are as follows Figure 1 As shown. From the series representation, we can see that [N + (CH3)3( n -C 14 H 29 )]4H2P2W 18 O 62 As the core, and BC (starch) as the shell. + (CH3)3( n -C 14 H 29 )]4H2P2W 18 O 62 As the core is not a completely continuous granular structure, but is covered by BC (starch) at the level of microcrystals. This shows that BC (starch) is in [N + (CH3)3( n -C 14 H 29 )]4H2P2W 18 O 62 The microcrystal surfaces inside the particles aggregate and grow to form a coated core-shell structure.

[0038] [N+ (CH3)3( n -C 14 H 29 )]4H2P2W 18 O 62 The preparation method is as follows: K6P2W 18 O 62 The aqueous solution was exchanged with an acidic cation resin to obtain H6P2W 18 O 62 Then, add four times the amount (molar ratio) of tetradecyltrimethylammonium bromide [N + (CH3)3( n -C 14 H 29 )]Br to obtain [N + (CH3)3( n -C 14 H 29 )]4H2P2W 18 O 62 The precipitate was filtered and dried to obtain a solid powder. Example 2

[0039] 0.4 g of β-cyclodextrin was dispersed in 2 mL of DMF and stirred with ultrasound for 0.5 h to obtain dispersion I. 0.02 g of Cs4H2S2Mo 18 O 62 Dispersed in 20 mL DMF, stirred and ultrasonicated for 4 h to obtain dispersion II. Under 405 nm monochromatic light irradiation, Cs4H2S2Mo 18 O 62 Dispersion II was added to β-cyclodextrin dispersion I and irradiated for 6 h. Subsequently, it was transferred to a closed reactor, filled with 0.4 MPa nitrogen, and the reaction temperature was 180 ° C for 48 h. 18 O 62 @BC (β-cyclodextrin). Its XRD results are as follows Figure 2 As shown, the results show that Cs4H2P2Mo 18 O 62 The structure is crystalline before and after coating with BC (β-cyclodextrin), that is, its crystalline structure does not change during the hydrothermal carbonization process.

[0040] Cs4H2S2Mo 18 O 62 The preparation is as follows: Na6S2Mo 18 O 62 The aqueous solution was exchanged with acidic cation resin to obtain H6S2Mo 18 O 62After that, add twice the amount (molar ratio) of Cs2CO3 to obtain Cs4H2S2Mo 18 O 62 The precipitate was filtered and dried to obtain a solid powder. Example 3

[0041] This example is a comparative example of Example 2. 0.4 g of β-cyclodextrin was dispersed in 2 mL of DMF and stirred with ultrasound for 0.5 h to obtain dispersion system I. 0.02 g of Cs6Mo 18 O 62 Dispersed in 20 mL DMF, stirred and ultrasonicated for 4 h to obtain dispersion II. Under 405 nm monochromatic light irradiation, Cs6Mo 18 O 62 Dispersion II was added to β-cyclodextrin dispersion I and irradiated for 6 h. Subsequently, it was transferred to a closed reactor, filled with 0.4 MPa nitrogen, and the reaction temperature was 180 ° C for 48 h. 18 O 62 @BC (β-cyclodextrin).

[0042] C6Mo 18 O 62 The preparation is as follows: in Na6S2Mo 18 O 62 Cs6Mo is obtained by adding twice the amount (molar ratio) of Cs2CO3 to the aqueous solution. 18 O 62 The product was precipitated and filtered to obtain a solid powder. Example 4

[0043] 0.5 g of dextran was dispersed in 5 mL of DMSO-water (V DMSO :V 水 = 5:1), stirred and ultrasonicated for 2 h to obtain dispersion I, and 0.01 g Dawson type vanadium iron substituted phosphotungstate ((MeOctIM) 10 KHP2W 15 V2FeO 62 ) were dispersed in 10 mL DMSO-water (V DMSO :V 水 = 5:1), stirred and ultrasonicated for 6 h to obtain dispersion II. Under 365 nm monochromatic light irradiation, (MeOctIM) 10 KHP2W 15 V2FeO 62 Dispersion II was added to dextran dispersion I and irradiated for 2 h. Subsequently, it was transferred to a closed reactor, filled with 1 MPa of carbon dioxide, and the reaction temperature was 180°C for 48 h. (MeOctIM)10 KHP2W 15 V2FeO 62 @BC(Glucan).

[0044] (MeOctIM) 10 KHP2W 15 V2FeO 62 The preparation of K 12 P2W 15 V2FeO 62 The aqueous solution is exchanged with an acidic cation resin to obtain H 12 S2Mo 18 O 62 . Put 1 portion of K 12 P2W 15 V2FeO 62 With 11 parts H 12 P2W 15 V2FeO 62 After mixing, 10 parts of 1-octyl-3-methylimidazolium bromide (MeOctIM)Br were added to obtain (MeOctIM) 10 KHP2W 15 V2FeO 62 The precipitate was filtered and dried to obtain a solid powder.

[0045] Examples 5 to 7 are methods for preparing biomass carbon-coated Weakley-type heteropolyacid hydrogen salt catalysts. Example 5

[0046] 0.8 g chitosan was dispersed in 5 mL DMSO and stirred with ultrasound for 1.5 h to obtain dispersion I. 0.016 g Ba5H2[Co4(H2O)2(SiW9O 34 )2] was dispersed in 10 mL DMF and stirred with ultrasound for 5 h to obtain dispersion II. Under 395 nm monochromatic light irradiation, Ba5H2[Co4(H2O)2(SiW9O 34 )2] Dispersion II was added to chitosan dispersion I and irradiated for 3 h. Subsequently, it was transferred to a closed reactor and filled with 0.5 MPa of hydrogen-nitrogen mixture (volume ratio 1:1). The reaction temperature was 150 ° C and the reaction time was 72 h. Ba5H2[Co4(H2O)2(SiW9O 34 )2]@BC(Chitosan).

[0047] Ba5H2[Co4(H2O)2(SiW9O 34 )2] is prepared as follows: Na 12 [Co4(H2O)2(SiW9O 34)2] The aqueous solution is exchanged with an acidic cation resin to obtain H 12 [Co4(H2O)2(SiW9O 34 )2], and then 5 times the amount (molar ratio) of barium nitrate was added to obtain Ba5H2[Co4(H2O)2(SiW9O 34 )2] precipitate, and filter and dry to obtain solid powder. Example 6

[0048] 0.1 g of cellulose was dispersed in 10 mL of DMF-acetonitrile-water (V DMF :V 乙腈 :V 水 = 1:1:1), stirred with ultrasound for 2 h to obtain dispersion I, and 0.03 g [Ru(bdy)3]4H2[Ru4(µ-O)4(µ-OH)2(H2O)4(γ-SiW 10 O 36 )2] dispersed in 1 mL DMF-acetonitrile-water (V DMF :V 乙腈 :V 水 = 1:1:1), stirred and ultrasonicated for 4 h to obtain dispersion II. Under 320~405 nm ultraviolet light irradiation, [Ru(bdy)3]4H2[Ru4(µ-O)4(µ-OH)2(H2O)4(γ-SiW 10 O 36 )2] dispersion II was added to cellulose dispersion I and irradiated for 2.5 h. Subsequently, it was transferred to a closed reactor and filled with 0.5 MPa of hydrogen-argon mixture (volume ratio 1:10) at 160°C for 36 h. [Ru(bdy)3]4H2[Ru4(µ-O)4(µ-OH)2(H2O)4(γ-SiW 10 O 36 )2]@BC(cellulose).

[0049] [Ru(bdy)3]4H2[Ru4(µ-O)4(µ-OH)2(H2O)4(γ-SiW 10 O 36 )2] is prepared as follows: K 12 [Ru4(µ-O)4(µ-OH)2(H2O)4(γ-SiW 10 O 36 )2] The aqueous solution is exchanged with an acidic cation resin to obtain H 12 [Ru4(µ-O)4(µ-OH)2(H2O)4(γ-SiW 10 O 36)2], and then add 4 times the amount (molar ratio) of [Ru(bdy)3]Cl2 to obtain [Ru(bdy)3]4H2[Ru4(µ-O)4(µ-OH)2(H2O)4(γ-SiW 10 O 36 )2] precipitate, and filter and dry to obtain solid powder. Example 7

[0050] 0.4 g of hemicellulose was dispersed in 5 mL of DMSO-acetonitrile-water (V DMSO :V 乙腈 :V 水 = 1:5:1), stirred with ultrasound for 2 h to obtain dispersion I, and 0.004 g Cs6Ag2H[Mn III 3(H2O)5(PW9O 34 )2] were dispersed in 4 mL DMSO-acetonitrile-water (V DMSO :V 乙腈 :V 水 = 1:5:1), stirred and ultrasonicated for 2 h to obtain dispersion II. Under 385 nm monochromatic light irradiation, Cs6Ag2H[Mn III 3(H2O)5(PW9O 34 )2] Dispersion II was added to hemicellulose dispersion I and irradiated for 5 h. Subsequently, it was transferred to a closed reactor and filled with 0.1 MPa of hydrogen. The reaction temperature was 150 ° C and the reaction time was 24 h. Cs6Ag2H[Mn III 3(H2O)5(PW9O 34 )2]@BC(hemicellulose).

[0051] Cs6Ag2H[Mn III 3(H2O)5(PW9O 34 )2] is prepared as follows: K9[Mn III 3(H2O)5(PW9O 34 )2] aqueous solution was exchanged with acidic cation resin to obtain H9[Mn III 3(H2O)5(PW9O 34 )2], and then add 6 times (molar ratio) of cesium nitrate and 2 times (molar ratio) of silver nitrate to obtain Cs6Ag2H[Mn III 3(H2O)5(PW9O 34 )2] precipitate, and filter and dry to obtain solid powder.

[0052] Examples 8 to 10 are methods for preparing biomass carbon-coated Keggin-type heteropolyacid hydrogen salt catalysts. Example 8

[0053] 0.04 g starch was dispersed in 0.5 mL acetonitrile-water mixture (V 乙腈 :V 水 = 10:1), stirred and ultrasonicated for 1.5 h to obtain dispersion I, and 0.02 g Ag3HSiMo 12 O 40 Dispersed in 5 mL of acetonitrile-water mixture (V 乙腈 :V 水 = 10:1), stirred and ultrasonicated for 6 h to obtain dispersion II. Under 405 nm monochromatic light irradiation, Ag3HSiMo 12 O 40 Dispersion II was added to starch dispersion I and irradiated for 1 h. Subsequently, it was transferred to a closed reactor, filled with 0.6 MPa nitrogen, and the reaction temperature was 180 ° C for 16 h. Ag3HSiMo was obtained. 12 O 40 @BC(starch).

[0054] Ag3HSiMo 12 O 40 The preparation is as follows: H4SiMo 12 O 40 Dissolve in water and add 1.5 times the amount of silver carbonate to obtain Ag3HSiMo 12 O 40 The precipitate was filtered and dried to obtain a solid powder. Example 9

[0055] 0.25 g chitosan was dispersed in 1.5 mL DMSO and stirred with ultrasound for 0.5 h to obtain dispersion I. 0.1 g Cs2HPW was added 12 O 40 Dispersed in 10.5 mL of DMSO, stirred and ultrasonicated for 1 h to obtain dispersion II. Under 320-405 nm UV light irradiation, Cs2HPW 12 O 40 Dispersion II was added to starch dispersion I and irradiated for 1.5 h. Subsequently, it was transferred to a closed reactor and filled with 0.3 MPa of carbon dioxide. The reaction temperature was 160°C and the reaction time was 40 h. Cs2HPW was obtained. 12 O 40 @BC(Chitosan).

[0056] CxDV 12 O 40 The preparation of H3PW 12 O 40 Dissolve in water and add 2 times the amount of cesium nitrate to obtain Cs2HPW 12 O40 The precipitate was filtered and dried to obtain a solid powder. Example 10

[0057] Disperse 0.08 g of cellulose in 6 mL of DMSO:acetonitrile:water (V DMSO :V 乙腈 :V 水 = 1:3:1) and stirred with ultrasound for 3.5 h to obtain dispersion I, and 0.012 g Ce 1.3 H 1.1 PW 10 V2O 40 Disperse in 12 mL of DMSO:acetonitrile:water (V DMSO :V 乙腈 :V 水 = 1:3:1), stirred and ultrasonicated for 5.5 h to obtain dispersion II. Under 365 nm ultraviolet light irradiation, Ce 1.3 H 1.1 PW 10 V2O 40 Dispersion II was added to cellulose dispersion I and irradiated for 1 h. Subsequently, it was transferred to a closed reactor and filled with 0.8 MPa of hydrogen and argon with a volume ratio of 1:3. The reaction temperature was 150 ° C and the reaction time was 24 h. Ce was obtained. 1.3 H 1.1 PMo 12 O 40 @BC (cellulose). Its FT-IR spectrum is as follows Figure 3 As shown, Ce 1.3 H 1.1 PMo 12 O 40 The characteristic vibration peaks are 1062, 968, 866, and 790 cm -1 Both appear in Ce 1.3 H 1.1 PMo 12 O 40 @BC (cellulose) spectrum. This shows that Ce 1.3 H 1.1 PMo 12 O 40 The Keggin-type structure did not change during the hydrothermal carbonization process.

[0058] Ce 1.3 H 1.1 PW 10 V2O 40 The preparation of K5PW 10 V2O 40 Dissolved in water, exchanged with acidic cation resin to obtain H5PW 10V2O 40 Then, 1.3 times the amount (molar ratio) of Ce(NO3)3 was added to obtain Ce 1.3 H 1.1 PW 10 V2O 40 The precipitate was filtered and dried to obtain a solid powder. Example 11

[0059] This embodiment is a comparative example of Example 2, and its difference is that no Cs4H2S2Mo is added. 18 O 62 , but 1mL of 1% sulfuric acid was added. Its XRD diffraction and SEM morphology are as follows Figure 2 and 4 shown. Figure 2 It shows that BC (β-cyclodextrin) has an amorphous structure. Figure 4 It shows that the morphology of BC (β-cyclodextrin) is spherical. Example 12

[0060] This example is synthesized with reference to Chinese patent CN113398994 to obtain Cs3PW 12 O 40 @δ-Bi2O3 heterojunction catalyst was used as a comparative example. Example 13

[0061] This example is a comparative example of Example 2, except that glucose (monosaccharide) is used as the biomass precursor. 0.4 g glucose was dissolved in 2 mL DMF, stirred and ultrasonicated for 0.5 h to obtain dispersion system I, and 0.02 g Cs4H2S2Mo 18 O 62 Dispersed in 20 mL DMF, stirred and ultrasonicated for 4 h to obtain dispersion II. Under 405 nm monochromatic light irradiation, Cs4H2S2Mo 18 O 62 Dispersion II was added to glucose dispersion I and irradiated for 6 hours. Subsequently, the mixture was transferred to a sealed reactor, filled with 0.4 MPa nitrogen, and the reaction temperature was set at 180°C for 48 hours. No product was obtained after the reaction because glucose, due to its high solubility, hydrolyzed into small molecules during the reaction and could not polymerize to form biomass carbon.

[0062] Examples 14 to 16 are photocatalytic reaction performance Example 14

[0063] In a sealed reactor with a quartz window, 25 mg of the catalyst was suspended in 50 mL of pure water. The photocatalytic reaction was carried out under 300 W LED irradiation, with an oxygen pressure ranging from 0.1 to 1.0 MPa, a reaction temperature of 0 to 80°C, and a reaction time of 2 hours.

[0064] Table 1 Photocatalytic performance of hydrogen peroxide production using catalysts prepared in Examples 1 to 12

[0065] serial number catalyst Pressure (MPa) Temperature (℃) Hydrogen peroxide production (mmol) 1 <![CDATA[The [N prepared in Example 1 + (CH3)3( n -C 14 H 29 )]4H2P2W 18 O 62 @BC (starch)]]> 0.5 25 1 2 <![CDATA[Cs4H2P2Mo prepared in Example 2 18 O 62 @BC (β-cyclodextrin)]]> 0.1 20 1.5 3 <![CDATA[Cs6P2Mo prepared in Example 3 18 O 62 @BC (β - cyclodextrin)]]> 0.1 20 0.4 4 <![CDATA[(MeOctIM) prepared in Example 4 10 KHP2W 15 V2FeO 62 @BC (dextran)]]> 0.2 60 1.8 5 <![CDATA[Ba5H2[Co4(H2O)2(SiW9O 34 )2]@BC (chitosan)]]> 0.6 5 2.1 6 <![CDATA[[Ru(bdy)3]4H2[Ru4(µ-O)4(µ-OH)2(H2O)4(γ-SiW 10 O 36 )2]@BC(cellulose)]]> 0.8 0 3.2 7 <![CDATA[Cs6Ag2H[Mn prepared in Example 7 III 3(H2O)5(PW9O 34 )2]@BC (hemicellulose)]]> 1.0 30 2.7 8 <![CDATA[Ag3HSiMo prepared in Example 8 12 O 40 @BC (starch)]]> 0.7 20 1.9 9 <![CDATA[Cs2HPW prepared in Example 9 12 O 40 @BC (chitosan)]]> 0.1 20 1.6 10 <![CDATA[Ce prepared in Example 10 1.3 H 1.1 PMo 12 O 40 @BC (cellulose)]]> 0.9 80 1.7 11 BC (β-cyclodextrin) prepared in Example 11 0.1 20 0.2 12 <![CDATA[Cs3PW prepared in Example 12 12 O 40 @δ-Bi2O3]]> 0.1 20 0.05 13 <![CDATA[Cs4H2P2Mo prepared in Example 2 18 O 62 hydrogen heteropolyacid salt]]> 0.1 20 0.01

[0066] The catalyst Cs6P2Mo obtained in Example 3 was used 18 O 62 The activity of @BC (β-cyclodextrin) is lower than that of the catalyst Cs4H2P2Mo obtained in Example 2. 18 O 62 @BC (β-cyclodextrin), indicating that heteropolyacid hydrogen salts are beneficial to the proton transfer and proton-coupled electron transfer processes, thus exhibiting higher activity.

[0067] Comparison of the results of Example 2 and Example 11 shows that the presence of the heteropolyacid hydrogen salt enables the composite catalyst to have good oxidation performance, thereby facilitating the synthesis of hydrogen peroxide.

[0068] Comparison of Example 9 and Example 12 shows that biomass carbon has better performance than δ-Bi2O3 in hydrogen peroxide synthesis. Example 15

[0069] This example demonstrates the decomposition of hydrogen peroxide. In a sealed reactor with a quartz window, 25 mg of catalyst was suspended in 50 mL of an aqueous solution containing 2 mmol of hydrogen peroxide. The photocatalytic reaction was carried out under argon atmosphere and irradiation with a 300 W LED. The reaction temperature ranged from 0 to 80°C, and the reaction time was 2 hours.

[0070] Table 2 Performance of the catalysts prepared in Examples 1 to 12 for photocatalytic decomposition of hydrogen peroxide

[0071] serial number catalyst Temperature (℃) Residual amount of hydrogen peroxide (mmol) 1 <![CDATA[The [N prepared in Example 1 + (CH3)3( n -C 14 H 29 )]4H2P2W 18 O 62 @BC(starch)]]> 25 1.8 2 <![CDATA[Cs4H2P2Mo prepared in Example 2 18 O 62 @BC (β-cyclodextrin)]]> 20 1.9 3 <![CDATA[Cs6P2Mo prepared in Example 3 18 O 62 @BC (β-cyclodextrin)]]> 60 1.7 4 <![CDATA[(MeOctIM) prepared in Example 4 10 KHP2W 15 V2FeO 62 @BC (dextran)]]> 5 2.0 5 <![CDATA[Ba5H2[Co4(H2O)2(SiW9O 34 )2]@BC (chitosan)]]> 0 2.0 6 <![CDATA[[Ru(bdy)3]4H2[Ru4(µ-O)4(µ-OH)2(H2O)4(γ-SiW 10 O 36 )2]@BC(cellulose)]]> 30 1.8 7 <![CDATA[Cs6Ag2H[Mn prepared in Example 7 III 3(H2O)5(PW9O 34 )2]@BC (hemicellulose)]]> 20 1.8 8 <![CDATA[Ag3HSiMo prepared in Example 8 12 O 40 @BC (starch)]]> 75 1.5 9 <![CDATA[Cs2HPW prepared in Example 9 12 O 40 @BC (chitosan)]]> 20 1.9 10 <![CDATA[Ce prepared in Example 10 1.3 H 1.1 PMo 12 O 40 @BC (cellulose)]]> 40 1.7 11 BC (β-cyclodextrin) prepared in Example 11 20 1.7 12 <![CDATA[Cs3PW prepared in Example 12 12 O 40 @δ-Bi2O3]]> 20 0.2 13 <![CDATA[Cs4H2P2Mo prepared in Example 2 18 O 62 hydrogen heteropolyacid salt]]> 20 1.1

[0072] Comparison of Example 9 and Example 12 shows that hydrogen peroxide decomposes quickly on the surface of δ-Bi2O3, which is not conducive to the synthesis of hydrogen peroxide. Example 16

[0073] The formaldehyde oxidation reaction was carried out in a vapor-containing gas phase. A 2-L gas reservoir was filled with 100 ppm formaldehyde-containing vapor, and the temperature of the reservoir and reactor was maintained at the same temperature. The reactor consisted of a quartz tube (5 cm diameter, 20 cm length) coated with 100 mg of catalyst. The gas reservoir and reactor were connected via a gas circulation pump and associated quartz tubing. The photocatalytic reaction was carried out under a 300 W xenon lamp for 2 h at a temperature between 0 and 80°C. The relative humidity ranged from 40% to 100%.

[0074] Table 3 Performance of the catalysts prepared in Examples 1 to 12 for photocatalytic decomposition of formaldehyde

[0075] serial number catalyst Temperature (℃) Relative humidity (%) Residual formaldehyde (ppm) 1 <![CDATA[[N prepared in Example 1 + (CH3)3( n -C 14 H 29 )]4H2P2W 18 O 62 @BC(starch)]]> 50 45 5 2 <![CDATA[Cs4H2P2Mo prepared in Example 2 18 O 62 @BC (β-cyclodextrin)]]> 20 40 15 3 <![CDATA[Cs6P2Mo prepared in Example 3 18 O 62 @BC (β-cyclodextrin)]]> 20 40 59 4 <![CDATA[(MeOctIM) prepared in Example 4 10 KHP2W 15 V2FeO 62 @BC (dextran)]]> 38 60 6 5 <![CDATA[Ba5H2[Co4(H2O)2(SiW9O 34 )2]@BC (chitosan)]]> 75 100 2 6 <![CDATA[[Ru(bdy)3]4H2[Ru4(µ-O)4(µ-OH)2(H2O)4(γ-SiW 10 O 36 )2]@BC (Cellulose)]]> 45 72 3.5 7 <![CDATA[Cs6Ag2H[Mn prepared in Example 7 III 3(H2O)5(PW9O 34 )2]@BC (hemicellulose)]]> 80 100 1.7 8 <![CDATA[Ag3HSiMo prepared in Example 8 12 O 40 @BC (starch)]]> 0 40 32 9 <![CDATA[Cs2HPW prepared in Example 9 12 O 40 @BC (chitosan)]]> 35 66 8 10 <![CDATA[Ce prepared in Example 10 1.3 H 1.1 PMo 12 O 40 @BC (cellulose)]]> 71 53 2.9 11 BC (β-cyclodextrin) prepared in Example 11 20 40 75 12 <![CDATA[Cs3PW prepared in Example 12 12 O 40 @δ-Bi2O3]]> 20 10 98 13 <![CDATA[Cs4H2P2Mo prepared in Example 2 18 O 62 hydrogen heteropolyacid salt]]> 20 10 85

[0076] Comparison of the results of Example 2 and Example 11 shows that the oxidation performance of single biomass carbon is poor, which is not conducive to the oxidation of formaldehyde.

[0077] The activity of the catalyst obtained in Example 3 is lower than that of the catalyst in Example 2, indicating that the heteropolyacid hydrogen salt is beneficial to proton transfer and proton-coupled electron transfer in formaldehyde oxidation, thereby showing higher activity.

[0078] Comparison of Example 9 and Example 12 shows that Cs3PW 12 O 40 @δ-Bi2O3 does not have formaldehyde oxidation activity.

Claims

1. A method for preparing biomass carbon-coated heteropolyacid hydrogen salt, characterized in that The following steps are involved: (1) dispersing a biomass polysaccharide precursor X in a polar organic solvent or a mixed solution of a polar organic solvent and water to obtain a dispersion system I, wherein the mass volume ratio of the biomass polysaccharide precursor X to the polar organic solvent or the mixed solution of the polar organic solvent and water is 0.01-0.2 g / mL; The biomass polysaccharide precursor X is selected from cellulose, hemicellulose, cyclodextrin, dextran, chitosan or starch; (2) Dispersing the heteropolyacid hydrogen salt H-POMs in a polar organic solvent or a mixed solution of a polar organic solvent and water to a dispersion system II, wherein the mass volume ratio of H-POMs to the polar organic solvent or the mixed solution of the polar organic solvent and water is 0.001-0.05 g / mL; the mass ratio of the heteropolyacid hydrogen salt H-POMs to the biomass polysaccharide precursor X is 0.01-0.5, wherein the anion of the heteropolyacid hydrogen salt H-POMs is selected from Keggin type, Dawson type or Weakley type heteropolyacid, and the cation of the heteropolyacid hydrogen salt H-POMs is selected from Cs + , Ag + , Ba 2+ , Ce 3+ , Ru 2+ or Ir 3+ N / C-containing complex cations, quaternary ammonium ions or imidazolium ions, where the proton H of H-POM + The number is an integer or decimal between 1 and 2; (3) Dispersion II and dispersion I were thoroughly mixed under ultraviolet light irradiation in the wavelength range of 320-405 nm; (4) The mixed dispersion was transferred into a sealed container and fully reacted in an oxygen-free environment at 120-180 °C to obtain biomass carbon-coated heteropolyacid hydrogen salt H-POMs@BC(X).

2. The method for preparing the biomass carbon-coated heteropolyacid hydrogen salt according to claim 1, characterized in that: In steps (1) and (2), the polar organic solvent is selected from acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide or formamide, and the volume ratio of the polar organic solvent to water is greater than or equal to 1:1 and less than or equal to 20:

1.

3. The method for preparing the biomass carbon-coated heteropolyacid hydrogen salt according to claim 1, characterized in that: In step (2), the Ru 2+ or Ir 3+ containing N / C coordination cation is selected from [Ru(bpy)3] 2+ , [Ru(dmb)3] 2+ , [Ru(bpz)3] 2+ , [Ru(phen)3] 2+ , [Ru(bpm)3] 2+ , [Ru(phd)3] 2+ , [Ru(bpy)2(phen-5-NH2)] 2+ , [Ru(dphphen)3] 2+ , [Ir(ppy)2(bpy)] + , [Ir(ppy)2(phen)] + , [Ir(ppy)2(dphphen)] + , [Ir(ppy)2(dtbbpy)] + , [Ir(F-mppy)2(bpy)] + , [Ir(F-mppy)2(phen)] + , [Ir(F-mppy)2(dphphen)] + , [Ir(dFppy)2(dtbbpy)] + , [Ir(dF(CF3)ppy)2(dtbbpy)] + , [Ir(dF(Me)ppy)2(dtbbpy)] + , Ir[(dFppy)2(4,4′-dCF3bpy)], Ir[4-t-bu-phenyl-4-t-bu-py]2(dtbpy)], [Ir[Me(Me)ppy]2(dtbpy)] + , Ir[(dFMeppy)2(4,4′-dCF3bpy)] + , [Ir(dFppy)2(dtbpy)] + , Ir[(FCF3(CF3)ppy)2(dtbpy)] + , Ir[(dFOMeppy)2(5,5'-dCF3bpy)] + , Ir[(dFMeppy)2(dtbpy)] + .

4. The method for preparing the biomass carbon-coated heteropolyacid hydrogen salt according to claim 1, characterized in that: In step (2), the quaternary ammonium salt ion is selected from alkyl trimethyl ammonium, alkyl triethyl ammonium, alkyl tripropyl ammonium, alkyl tributyl ammonium, wherein the alkyl group is octyl, dodecyl, tetradecyl, hexadecyl or octadecyl.

5. The method for preparing the biomass carbon-coated heteropolyacid hydrogen salt according to claim 4, characterized in that: The quaternary ammonium salt ion is selected from octyltrimethylammonium ion, octyltriethylammonium ion, octyltripropylammonium ion, octyltributylammonium ion, dodecyltrimethylammonium ion, dodecyltriethylammonium ion, dodecyltripropylammonium ion, dodecyltributylammonium ion, tetradecyltrimethylammonium ion, tetradecyltriethylammonium ion, tetradecyltripropylammonium ion, tetradecyltributylammonium ion, hexadecyltrimethylammonium ion, hexadecyltriethylammonium ion, hexadecyltripropylammonium ion, hexadecyltributylammonium ion, octadecyltrimethylammonium ion, octadecyltriethylammonium ion, octadecyltripropylammonium ion or octadecyltributylammonium ion.

6. The method for preparing the biomass carbon-coated heteropolyacid hydrogen salt according to claim 1, characterized in that: In step (2), the imidazolium salt ion is selected from 1- and 3-substituted imidazolium ions, and when the 1- and 3-substituents are different, the 1-substituent is octyl, dodecyl, tetradecyl, hexadecyl or octadecyl, and the 3-substituent is methyl, ethyl, propyl or butyl; when the 1- and 3-substituents are the same, the substituent is octyl, dodecyl, tetradecyl, hexadecyl or octadecyl; Alternatively, when there are substituents at positions 1, 2, and 3, the substituent at position 1 is octyl, dodecyl, tetradecyl, hexadecyl, or octadecyl, and the substituents at positions 2 and 3 are methyl.

7. The method for preparing the biomass carbon-coated heteropolyacid hydrogen salt according to claim 6, characterized in that: The imidazolium salt ion is selected from 1-octyl-3-methylimidazolium ion, 1-octyl-3-ethylimidazolium ion, 1-octyl-3-propylimidazolium ion, 1-octyl-3-butylimidazolium ion, 1-dodecyl-3-methylimidazolium ion, 1-dodecyl-3-ethylimidazolium ion, 1-dodecyl-3-propylimidazolium ion, 1-dodecyl-3-butylimidazolium ion, 1-tetradecyl-3-methylimidazolium ion, 1-tetradecyl-3-ethylimidazolium ion, 1-tetradecyl-3-propylimidazolium ion, 1-tetradecyl-3-butylimidazolium ion, 1-hexadecyl-3-methylimidazolium ion, 1-hexadecyl-3-ethylimidazolium ion, 1-hexadecyl-3-propylimidazolium ion, Imidazolium ion, 1-hexadecyl-3-butylimidazolium ion, 1-octadecyl-3-methylimidazolium ion, 1-octadecyl-3-ethylimidazolium ion, 1-octadecyl-3-propylimidazolium ion, 1-octadecyl-3-butylimidazolium ion, 1,3-dioctylimidazole, 1,3-didodecylimidazole, 1,3-ditetradecylimidazole, 1,3-dihexadecylimidazole, 1,3-dioctadecylimidazole, 1-octyl-2,3-dimethylimidazole, 1-dodecyl-2,3-dimethylimidazole, 1-tetradecyl-2,3-dimethylimidazole, 1-hexadecyl-2,3-dimethylimidazole, 1-octyl-2,3-dimethylimidazole.

8. The biomass carbon-coated heteropolyacid hydrogen salt catalyst prepared according to the method for preparing the biomass carbon-coated heteropolyacid hydrogen salt according to claim 1.

9. Use of the biomass carbon-coated heteropolyacid hydrogen salt catalyst according to claim 8 in photocatalysis.

10. The use according to claim 9, characterized in that include: Photocatalytic oxygen reduction or formaldehyde oxidation.

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