An integrated frequency-divided photo-thermal synergistic catalyst, its preparation method and application

Abstract

The present invention discloses an integrated frequency-divided photo-thermal synergistic catalyst, its preparation method and application, belonging to the technical field of photo-thermal coupling catalysis for CO2 reduction and resource utilization. The above-mentioned integrated frequency-divided photo-thermal synergistic catalyst uses a foam metal as the substrate, and successively includes a photo-thermal layer, a protective layer and a photo-electric layer from the substrate outwards. Among them, the photo-thermal layer is an amorphous metal oxide, the protective layer is a heat-resistant metal oxide-Y zeolite composite, and the photo-electric layer is a composite metal oxide with an array morphology; the photo-thermal layer is used to absorb low-frequency photons to generate heat, the protective layer is used for heat conduction control and heat buffering, and the photo-electric layer is used to absorb the energy of high-frequency photons for photocatalytic CO2 reduction reaction. The integrated frequency-divided photo-thermal synergistic catalyst of the present invention can be used in concentrated photocatalytic CO2 reduction, can perform cascade utilization of solar energy from the ultraviolet region to the infrared region, exhibits excellent photo-thermal coupling catalytic CO2 reduction performance, and has good stability at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalysis, and particularly to a monolithic frequency-divided photo-thermal synergistic catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of photocatalysis technology, single photocatalysis can no longer meet the requirements of people for efficient catalysis. Therefore, research on introducing an external field to enhance photocatalytic performance has emerged. Among them, photo-thermal catalysis is the integrated utilization of pure photocatalysis and thermal catalysis. In the existing technology, photo-thermal coupling catalysis for CO2 reduction can convert CO2 into high-value chemicals under mild reaction conditions, which is an effective way to alleviate environmental pollution and energy crisis.

[0003] The foam metal material is a new type of special metal material containing pores, and is widely used in the fields of chemical industry, aerospace, etc. due to its advantages such as low density, high energy absorption performance, and good stability. Common foam metals including aluminum foam, copper foam, iron foam, and nickel foam are used as carriers in catalytic reactions, which can increase the contact area between reactants and catalysts.

[0004] The invention patent with the publication number of CN107570174 discloses a highly efficient and stable nickel foam-based photocatalytic material. Using nickel foam as the substrate, a zinc oxide crystal layer is loaded by the crystal layer method, and then zinc oxide nanorod arrays are grown along the zinc oxide crystal layer by the hydrothermal method. Silver nanoparticles are in-situ photoreduced and deposited on the surface of the zinc oxide nanorod arrays to obtain a silver / zinc oxide nanorod array / nickel foam self-supporting material. However, this catalytic material cannot achieve the frequency division utilization of sunlight, that is, it cannot achieve high-efficiency sunlight utilization efficiency. The invention patent with the publication number of CN111889111 discloses a monolithic photocatalyst with a three-dimensional heterostructure, a preparation method thereof, and an application thereof. The catalyst is a monolithic photocatalyst of the CdS, NiS / Ni3S2@NF system. By growing a high density of cadmium sulfide particles on nickel foam, the light can be utilized to the greatest extent. At the same time, there is a rich amount of nickel sulfide at the interface between cadmium sulfide and nickel foam, which is used to ensure the tight combination of cadmium sulfide and nickel foam. However, this catalyst is prone to sintering inactivation when directly contacting high temperatures.

[0005] The main problems existing in current photocatalysts are as follows: The light absorption range of photocatalysts still mostly concentrates in the ultraviolet light region, so the utilization rate of sunlight is low; The currently developed photocatalysts still fail to produce an efficient inhibitory effect on the recombination of photo-generated electrons and holes, and their ability to generate and enable the high-speed transmission of photo-generated carriers is limited by their inherent properties; The existing photocatalysts still generally have the problem of poor stability. Summary of the Invention

[0006] Object of the Invention: In order to solve the technical problems of high recombination rate of photo-generated carriers and poor stability existing in the prior art, the present invention aims to provide an integrated frequency-divided photo-thermal synergistic catalyst with high solar energy utilization rate and good thermal stability. Moreover, the present invention also provides a preparation method and application of the integrated frequency-divided photo-thermal synergistic catalyst.

[0007] Technical Solution: The integrated frequency-divided photo-thermal synergistic catalyst described in the present invention uses a foam metal as a substrate, and successively includes a photo-thermal layer, a protective layer, and a photo-electric layer from the substrate outwards, wherein the photo-thermal layer is an amorphous metal oxide, the protective layer is a heat-resistant metal oxide-Y zeolite composite, and the photo-electric layer is a composite metal oxide with an array morphology.

[0008] Furthermore, the foam metal is foam copper, foam nickel or foam iron; the amorphous metal oxide is nickel oxide, chromium oxide or cobalt oxide; the heat-resistant metal oxide is alumina or silica, preferably alumina, and the composite metal oxide is two or more of zinc oxide, cerium oxide, titanium dioxide, copper oxide, nickel oxide.

[0009] The preparation method of the integrated frequency-divided photo-thermal synergistic catalyst described in the present invention includes the following steps:

[0010] (1) Using a foam metal as a substrate, an amorphous metal oxide is deposited on the surface of the substrate by electrodeposition to obtain a substrate material with a photo-electric layer;

[0011] (2) The material obtained in step (1) is immersed in a mixed solution of a heat-resistant metal oxide-Y zeolite composite, and a heat-resistant metal oxide-Y zeolite composite is grown on the surface of the photo-electric layer by a hydrothermal method to obtain a substrate material with a protective layer and a photo-electric layer;

[0012] (3) The material obtained in step (2) is impregnated in a precursor solution of a composite metal oxide, and after impregnation, it is taken out for annealing treatment;

[0013] (4) The material obtained in step (3) is impregnated in a precursor solution of a composite metal oxide added with a structure-directing agent, and crystallization treatment is carried out. After completion, the integrated frequency-divided photo-thermal synergistic catalyst is obtained.

[0014] Furthermore, in step (1), the conditions of the electrodeposition method are: the anode is a nickel sheet, a chromium sheet or a cobalt sheet, the cathode is a foam metal as the cathode, the electrolyte is an ionic liquid composed of aminopropionic acid, metal chloride salt and a solvent, the current density of the cathode is 10-30 mA / cm 2 , the electrodeposition time is 10-30 min; in the electrolyte, the molar ratio of aminopropionic acid to metal chloride salt is 1:5-10, preferably 1:5, the metal chloride salt is nickel chloride hexahydrate, chromium chloride hexahydrate or cobalt chloride hexahydrate, and the solvent is water.

[0015] Further, in step (2), the method for preparing the mixed solution of the heat-resistant metal oxide - Y zeolite composite is as follows: uniformly mixing an aluminum source, a silicon source, a template agent, a heat-resistant metal oxide, and a solvent; the molar ratio of the aluminum source, the silicon source, the template agent, and the heat-resistant metal oxide is 2:2:1 - 1.5:1, preferably 2:2:1:1; the aluminum source is sodium aluminate, the silicon source is sodium silicate, and the template agent is 1-benzyl-4-hydroxypiperidine; the conditions of the hydrothermal method are: the temperature of the hydrothermal reaction is 100 - 150 °C, and the time of the hydrothermal reaction is 2 - 10 h.

[0016] Further, in step (3), the method for preparing the composite metal oxide precursor solution is as follows: uniformly mixing a composite metal precursor, an alkali, and a solvent; the composite metal precursor is two or more of zinc acetate, cerium nitrate, tetrabutyl titanate, copper nitrate, and nickel nitrate, the alkali is potassium hydroxide, and the solvent is water; the ratio of the total molar amount of the composite metal precursor to the molar amount of the alkali is 1:3 - 10, preferably 1:5; the conditions for uniform mixing are: stirring at 50 - 80 °C for 3 - 5 h; the impregnation time is 1 - 3 h; the conditions for the annealing treatment are: the temperature is 150 - 250 °C, and the time is 1 - 3 h.

[0017] Further, in step (4), the structure-directing agent is N,N-dimethylacetamide, and the ratio of the molar amount of the structure-directing agent to the total molar amount of the composite metal precursor is 1:1 - 3, preferably 1:2 - 3; the crystallization treatment time is 5 - 15 h, and the seed layer obtained after the annealing treatment can make the optoelectronic layer grow more firmly under the action of the structure-directing agent.

[0018] Application of the monolithic frequency-divided photo-thermal synergistic catalyst described in the present invention in photocatalytic CO2 reduction for preparing solar fuels.

[0019] Further, the method for the above application includes the following steps: placing the monolithic frequency-divided photo-thermal synergistic catalyst in a quartz reactor, irradiating with a xenon lamp with 40 - 100 mW / cm 3 and using a pair of Fresnel lenses to focus the light source, introducing a CO2 and N2 mixed gas with a volume ratio of 1:99 - 2:98, passing through ultrapure water and then introducing it into the reactor, controlling the reactor pressure to be atmospheric pressure, and carrying out a photocatalytic CO2 reduction reaction for 30 min - 180 min, and the reaction products are detected and analyzed by a gas chromatograph.

[0020] Principle of the invention: The amorphous metal oxide of the photothermal layer exhibits good infrared absorption performance; the basic sites on the surface of the alumina-Y zeolite composite in the protective layer can enhance the adsorption of the reactant CO2, and at the same time, the moderate thermal conductivity can play a role in heat buffering; the selection of N,N-dimethylacetamide can enable the growth of an array structure in the photoelectric layer, increasing the utilization rate of photons.

[0021] Advantages: Compared with the prior art, the present invention has the following remarkable advantages:

[0022] (1) The integrated frequency-divided photothermal synergistic catalyst of the present invention includes a foam metal substrate, a photothermal layer, a protective layer, and a photoelectric layer. Among them, the photoelectric layer (composite metal oxide with an array morphology) can absorb the energy of ultraviolet-visible light for photocatalytic CO2 reduction reaction; the photothermal layer (amorphous metal oxide) can absorb infrared light to generate heat and transfer it to the photoelectric layer through the protective layer. The increase in the temperature of the catalytic sites can reduce the activation energy of the photocatalytic reaction, thereby enhancing the catalytic performance of the photoelectric layer; compared with traditional catalysts, the frequency-divided photothermal synergistic catalyst designed in the present invention realizes the gradient utilization of sunlight, and at the same time, the array morphology of the photoelectric layer can make the incident light reflect multiple times between the nanorods, greatly increasing the utilization rate of sunlight;

[0023] (2) The protective layer (alumina-Y zeolite composite) between the photoelectric layer and the photothermal layer prepared in the present invention not only plays a role in heat buffering, but also can protect the photocatalyst of the photoelectric layer from sintering and deactivating due to direct contact with high temperature while strengthening the photocatalytic reaction kinetics of the photoelectric layer, thereby ensuring the stability of the photocatalyst of the photoelectric layer; in addition, the basic sites on the surface can also enhance the adsorption of the reactant CO2;

[0024] (3) The preparation of the catalyst of the present invention is simple in operation, low in cost, good in stability, and exhibits excellent photocatalytic CO2 reduction activity under concentrated light conditions. It has been experimentally verified that when using the catalyst prepared in the present invention, the highest CH4 yield reaches 2554 μmol·h -1 ·g -1 , and the highest CO yield reaches 368 μmol·h -1 ·g -1 , showing broad prospects in practical applications. Description of the drawings

[0025] Figure 1 is the electron microscope image of the foam metal as the substrate in the integrated frequency-divided photothermal synergistic catalyst prepared in Example 1 of the present invention;

[0026] Figure 2 is the electron microscope image of the photothermal layer in the integrated frequency-divided photothermal synergistic catalyst prepared in Example 1 of the present invention;

[0027] Figure 3This is the electron micrograph of the protective layer and the optoelectronic layer in the monolithic frequency-divided photothermal synergistic catalyst prepared in Example 1 of the present invention. Detailed implementation mode

[0028] Next, the present invention will be further described in conjunction with specific embodiments and the accompanying drawings.

[0029] Example 1: The monolithic frequency-divided photothermal synergistic catalyst of the present invention includes a copper foam substrate, an amorphous nickel oxide (black nickel) photothermal layer, an alumina-Y zeolite composite protective layer, and a zinc oxide / nickel oxide composite metal oxide optoelectronic layer with an array morphology.

[0030] The specific preparation method of the above catalyst is as follows: Under a 50°C oil bath, 10 mmol of aminopropionic acid and 50 mmol of nickel chloride hexahydrate are added to 100 ml of deionized water to prepare an ionic electrolyte solution. Using a nickel metal sheet as the anode and a copper foam with a specification of 5 cm × 5 cm as the cathode, controlling the stirring speed at 300 r / min and the cathode current density at 20 mA / cm 2 , performing constant current electrodeposition for 30 min, rinsing the impurities on the cathode surface with deionized water, and then washing and drying for standby; adding 10 mmol of sodium aluminate, 10 mmol of sodium silicate, 5 mmol of 1-benzyl-4-hydroxypiperidine, and 5 mmol of alumina to 100 ml of water, fully stirring and mixing, and then performing hydrothermal treatment at 100°C for 10 h; then, taking out the copper foam-based catalyst, washing it thoroughly, adding 6 mmol of zinc acetate, 6 mmol of nickel nitrate, 3.36 g of potassium hydroxide, and 100 ml of ethanol, mixing, stirring at 70°C for 4 h to prepare a precursor solution, taking it out after impregnation for 3 h and annealing at 200°C for 2 h. The prepared material is impregnated in a precursor solution of a composite metal oxide added with 6 mmol of a structure-directing agent N,N-dimethylacetamide, and subjected to a crystallization treatment for 10 h to obtain a copper foam@black nickel@alumina-Y zeolite@zinc oxide / nickel oxide monolithic frequency-divided photothermal synergistic monolithic catalyst, and performing electron microscopy characterization on the catalyst, as Figures 1-3 shown. Figure 1 The foam metal substrate in has an open connected pore framework structure with a pore diameter of about 200 - 300 μm, Figure 2 The morphology of the photothermal layer in has no obvious crystal structure, Figure 3 The protective layer in has an irregular shape, and the optoelectronic layer exhibits an array structure. The length of the nanorods is about 2 - 3 μm, and the diameter is about 300 nm.

[0031] Example 2: The monolithic frequency-divided photothermal synergistic catalyst of the present invention includes a nickel foam substrate, an amorphous chromium oxide (black chromium) photothermal layer, an alumina-Y zeolite composite protective layer, and a cerium oxide / copper oxide composite metal oxide with an array morphology.

[0032] The preparation method of the above catalyst is as follows: Under a 50 °C oil bath, 10 mmol of alanine and 50 mmol of chromium(III) chloride hexahydrate are added to 100 ml of deionized water to prepare an ionic electrolyte. Using a chromium metal sheet as the anode and nickel foam with a specification of 5 cm × 5 cm as the cathode, the stirring speed is controlled at 300 r / min, and the cathode current density is 10 mA / cm 2 , and constant current electrodeposition is carried out for 30 min. The impurities on the cathode surface are rinsed clean with deionized water, and then washed and dried for standby; 10 mmol of sodium aluminate, 10 mmol of sodium silicate, 5 mmol of 1-benzyl-4-hydroxypiperidine, and 5 mmol of alumina are added to 100 ml of water, stirred and mixed thoroughly, and then hydrothermally treated at 130 °C for 5 h; After that, the nickel foam-based catalyst is taken out, washed thoroughly, 6 mmol of cerium nitrate, 6 mmol of copper nitrate, 3.36 g of potassium hydroxide, and 100 ml of ethanol are added and mixed, and stirred at 50 °C for 5 h to prepare a precursor solution. After impregnation for 2 h, it is taken out and annealed at 150 °C for 3 h. The prepared material is impregnated in a precursor solution of a composite metal oxide added with 4 mmol of a structure-directing agent N,N-dimethylacetamide, and subjected to crystallization treatment for 15 h to obtain a nickel foam@black chromium@alumina-Y zeolite@cerium oxide / copper oxide monolithic frequency-divided photothermal synergistic monolithic catalyst.

[0033] Example 3: The monolithic frequency-divided photothermal synergistic catalyst of the present invention includes a foam iron substrate, an amorphous cobalt oxide (black cobalt) photothermal layer, an alumina-Y zeolite composite protective layer, and a titanium dioxide / copper oxide / cerium oxide composite metal oxide optoelectronic layer with an array morphology.

[0034] The preparation method of the above catalyst is as follows: Under a 50 °C oil bath, 10 mmol of alanine and 50 mmol of cobalt(II) chloride hexahydrate are added to 100 ml of deionized water to prepare an ionic electrolyte. Using a chromium metal sheet as the anode and foam iron with a specification of 5 cm × 5 cm as the cathode, the stirring speed is controlled at 300 r / min, and the cathode current density is 30 mA / cm 2, perform constant current electrodeposition for 10 min, rinse the impurities on the cathode surface with deionized water, then wash and dry for standby; add 10 mmol of sodium aluminate, 10 mmol of sodium silicate, 5 mmol of 1-benzyl-4-hydroxypiperidine and 5 mmol of alumina to 100 ml of water, stir well and mix, and then perform hydrothermal treatment at 150 °C for 2 h; then, take out the foam iron-based catalyst, wash it thoroughly, add 6 mmol of tetrabutyl titanate, 6 mmol of cerium nitrate, 6 mmol of copper nitrate, 5.0 g of potassium hydroxide and 100 ml of ethanol, mix, and stir at 80 °C for 3 h to prepare a precursor solution. After impregnation for 1 h, take it out and anneal at 250 °C for 1 h. The prepared material is impregnated in a precursor solution of composite metal oxide added with 8 mmol of structure-directing agent N,N-dimethylacetamide, and subjected to crystallization treatment for 5 h to obtain a foam iron@black cobalt@alumina-Y zeolite@titanium dioxide / copper oxide / cerium oxide monolithic frequency-divided photothermal synergistic monolithic catalyst.

[0035] Example 4: The method for the application of the monolithic frequency-divided photothermal synergistic catalyst of the present invention in photocatalytic CO2 reduction to prepare solar fuel includes the following steps: Take a prepared monolithic frequency-divided photothermal synergistic catalyst and place it in a quartz reactor of 100 cm 3 , irradiate with a 100 mW / cm 3 xenon lamp and use a pair of Fresnel lenses to focus the light source. Introduce a CO2 and N2 mixed gas with a volume ratio of 1:99. After passing through ultrapure water, introduce it into the reactor. Control the reactor pressure at atmospheric pressure and perform photocatalytic CO2 reduction reaction for 60 min. The reaction products are detected and analyzed by a gas chromatograph.

[0036] Comparative Example 1: Add 6 mmol of zinc acetate, 6 mmol of nickel nitrate, 3.36 g of potassium hydroxide and 100 ml of ethanol to a clean 200 ml beaker, mix and stir at 70 °C for 4 h to prepare a precursor solution. After adding 6 mmol of structure-directing agent N,N-dimethylacetamide, crystallize for 10 h to obtain a zinc oxide / nickel oxide nanocatalyst.

[0037] Comparative Example 2: Place a foam copper with a specification of 5 cm × 5 cm as a catalyst substrate in a clean 200 ml beaker, add 6 mmol of zinc acetate, 6 mmol of nickel nitrate, 3.36 g of potassium hydroxide and 100 ml of ethanol, mix and stir at 70 °C for 4 h to prepare a precursor solution. After impregnation for 3 h, take it out and anneal at 200 °C for 2 h. The prepared material is impregnated in a precursor solution of composite metal oxide added with 6 mmol of structure-directing agent N,N-dimethylacetamide, and subjected to crystallization treatment for 10 h to obtain a foam copper@zinc oxide / nickel oxide monolithic catalyst.

[0038] Comparative Example 3: Under an oil bath at 50 °C, 10 mmol of alanine and 50 mmol of nickel chloride hexahydrate were added to 100 ml of deionized water to prepare an ionic electrolyte. A nickel metal sheet was used as the anode, and copper foam with a specification of 5 cm × 5 cm was used as the cathode. The stirring speed was controlled at 300 r / min, and the cathode current density was 20 mA / cm 2 , and constant current electrodeposition was carried out for 30 min. The impurities on the cathode surface were rinsed clean with deionized water; 6 mmol of zinc acetate, 6 mmol of nickel nitrate, 3.36 g of potassium hydroxide, and 100 ml of ethanol were mixed and stirred at 70 °C for 4 h to prepare a precursor solution. After impregnation for 3 h, it was taken out and annealed at 200 °C for 2 h. The prepared material was impregnated in a precursor solution of a composite metal oxide containing 6 mmol of a structure-directing agent N,N-dimethylacetamide, and crystallization treatment was carried out for 10 h to obtain a copper foam@black nickel@zinc oxide / nickel oxide monolithic catalyst.

[0039] The catalysts prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were used for the CO2 photocatalytic reduction experiment under concentrated light, and the experimental conditions were the same as those in Example 4.

[0040] Table 1 Comparison of the performance of different catalysts for the photocatalytic reduction of CO2 under concentrated light (unit: μmol·h -1 ·g -1 )

[0041]

[0042] As shown in Table 1, Comparative Example 1 had only a photocatalyst and had the worst performance; Comparative Example 2 was a photocatalyst with a substrate added, and the effect was improved; Comparative Example 3 consisted of a metal substrate, a photothermal layer, and a photoelectric layer. After adding the photothermal effect, the performance of the catalyst was greatly improved and was close to that of Example 1, indicating that the solar energy frequency division utilization can greatly increase the catalytic performance.

[0043] The catalysts prepared in Example 1 and Comparative Example 3 were used for the CO2 photocatalytic reduction cyclic experiment under concentrated light, and the experimental conditions were the same as those in Example 4.

[0044] As can be seen from Table 2, although the catalyst in Comparative Example 3 can realize the solar energy distribution utilization and improve the catalytic performance, due to the lack of thermal protection for the photoelectric layer by a protective layer, the stability of the catalyst is poor, and most of the catalytic performance is lost after four cycles; while Example 1 shows the best photocatalytic activity in the photocatalytic CO2-H2O reaction system under concentrated light conditions, and can efficiently catalytically reduce the greenhouse gas CO2 into available solar fuels CH4 and CO, and also has good catalytic stability.

[0045] Table 2 Comparison of the cyclic performance of different catalysts for the photocatalytic reduction of CO2 under concentrated light (unit: μmol·h-1 ·g -1 )

[0046]

Claims

1. An integrated frequency-divided photo-thermal synergistic catalyst, characterized in that, The catalyst uses a foam metal as the substrate, and from the substrate outwards, it sequentially includes a photothermal layer, a protective layer, and a photoelectric layer. Among them, the photothermal layer is an amorphous metal oxide, the protective layer is a heat-resistant metal oxide - Y zeolite composite, and the photoelectric layer is a composite metal oxide with an array morphology.

2. The integrated frequency-divided photo-thermal synergistic catalyst according to claim 1, wherein The foam metal is foam copper, foam nickel, or foam iron; the amorphous metal oxide is nickel oxide, chromium oxide, or cobalt oxide; the heat-resistant metal oxide is alumina or silica, and the composite metal oxide is two or more of zinc oxide, cerium oxide, titanium dioxide, copper oxide, and nickel oxide.

3. The preparation method of the integrated frequency-divided photo-thermal synergistic catalyst according to claim 1, characterized in that, It includes the following steps: (1) Using the foam metal as the substrate, an amorphous metal oxide is deposited on the substrate surface by electrodeposition to obtain a substrate material with a photothermal layer. (2) Immerse the material prepared in step (1) in a mixed solution of a heat-resistant metal oxide - Y zeolite composite, and use hydrothermal method to grow a heat-resistant metal oxide - Y zeolite composite on the surface of the photothermal layer to obtain a substrate material with a protective layer and a photothermal layer; the preparation method of the mixed solution of the heat-resistant metal oxide - Y zeolite composite is: mix an aluminum source, a silicon source, a template agent, a heat-resistant metal oxide, and a solvent evenly. (3) Immerse the material prepared in step (2) in a precursor solution of a composite metal oxide, and after the immersion is completed, take it out for annealing treatment. (4) Immerse the material prepared in step (3) in a precursor solution of a composite metal oxide added with a structure-directing agent, and perform crystallization treatment. After completion, the monolithic frequency-divided photothermal synergistic catalyst is obtained; the structure-directing agent is N,N-dimethylacetamide.

4. The preparation method according to claim 3, characterized in that, In step (1), the conditions of the electrodeposition method are as follows: the anode is a nickel sheet, a chromium sheet or a cobalt sheet, the cathode is a foam metal, the electrolyte is an ionic electrolyte composed of aminopropionic acid, metal chloride salt and a solvent, and the current density of the cathode is 10 - 30 mA / cm 2 , the electrodeposition time is 10 - 30 min; in the electrolyte, the molar ratio of aminopropionic acid to metal chloride salt is 1:5 - 10, the metal chloride salt is nickel chloride hexahydrate, chromium chloride hexahydrate or cobalt chloride hexahydrate, and the solvent is water.

5. The preparation method according to claim 3, wherein In step (2), the molar ratio of the aluminum source, the silicon source, the template agent, and the heat-resistant metal oxide is 2:2:1 - 1.5:1; the aluminum source is sodium aluminate, the silicon source is sodium silicate, and the template agent is 1-benzyl-4-hydroxypiperidine.

6. The preparation method according to claim 3, characterized in that, In step (2), the conditions of the hydrothermal method are: the temperature of the hydrothermal reaction is 100 - 150 °C, and the time of the hydrothermal reaction is 2 - 10 h.

7. The preparation method according to claim 3, characterized in that, In step (3), the preparation method of the precursor solution of the composite metal oxide is: mix a composite metal precursor, an alkali, and a solvent evenly; the composite metal precursor is two or more of zinc acetate, cerium nitrate, tetrabutyl titanate, copper nitrate, and nickel nitrate, the alkali is potassium hydroxide, and the solvent is ethanol; the ratio of the total molar amount of the composite metal precursor to the molar amount of the alkali is 1:3 - 10; the condition for mixing evenly is: stir at 50 - 80 °C for 3 - 5 h.

8. The preparation method according to claim 7, wherein In step (4), the ratio of the molar amount of the structure-directing agent to the total molar amount of the composite metal precursor is 1:1 - 3, and the time of the crystallization treatment is 5 - 15 h.

9. The preparation method according to claim 3, characterized in that, In step (3), the time of the immersion is 1 - 3 h; the conditions of the annealing treatment are: the temperature is 150 - 250 °C, and the time is 1 - 3 h.

10. Application of the monolithic frequency-divided photothermal synergistic catalyst according to claim 1 in photocatalytic reduction of CO2 to prepare solar fuels.

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