Metalloporphyrin-bismuth oxyhalide composite catalyst with amide functional interface as well as preparation method and application of metalloporphyrin-bismuth oxyhalide composite catalyst

Abstract

The invention discloses a metalloporphyrin-bismuth oxyhalide composite catalyst with an amide functional interface as well as a preparation method and application of the metalloporphyrin-bismuth oxyhalide composite catalyst. The catalyst successfully realizes efficient compounding with metalloporphyrin by introducing an amide interface on the surface of bismuth oxyhalide: firstly, performing condensation reaction on an amino silane coupling agent and hydroxyl on the surface of bismuth oxyhalide to construct stable amino-functionalized bismuth oxyhalide; and then, the amino group on the surface of the bismuth oxyhalide reacts with the carboxyl group of the 5, 10, 15, 20-tetra (4-carboxyphenyl) metalloporphyrin to form the metalloporphyrin-bismuth oxyhalide composite catalyst with an amide interface. The composite photocatalyst not only remarkably promotes electron transfer between bismuth oxyhalide and metalloporphyrin, but also effectively enhances the carbon-carbon coupling capacity of a C1 intermediate in the photocatalytic CO2 reduction process, and realizes selective conversion of CO2 to a high-added-value C2 product (ethylene). The invention provides a new interface engineering strategy for constructing an efficient multi-carbon product photocatalytic system.

Description

Technical Field

[0001] This invention relates to a metal porphyrin-bismuth halide composite catalyst with an amide functional interface, its preparation method, and its application in photocatalytic CO2 reduction to ethylene. Background Technology

[0002] Currently, the conversion energy barrier for photocatalytic CO2 reduction to ethylene is relatively high, resulting in a significantly lower ethylene yield compared to C1 products. Furthermore, the photocatalytic CO2 reduction process is a multi-electron, multi-step reaction with complex product composition, posing significant challenges to improving reaction conversion and product selectivity. The key to achieving efficient photocatalytic CO2 reduction to ethylene lies in the rational design and controllable preparation of the photocatalyst.

[0003] From the perspective of reaction mechanism, photocatalytic CO2 reduction to ethylene requires the synergistic resolution of key scientific issues such as CO2 molecule activation, electron transfer, and carbon-carbon coupling. Among these, efficiently promoting carbon-carbon coupling of C1 intermediates is considered the key and challenging aspect of ethylene production. Given that the photocatalytic CO2 reduction process typically involves basic steps such as light capture, photogenerated carrier separation, and surface redox reactions, highly efficient CO2 reduction photocatalysts must possess strong CO2 chemisorption capacity, a suitable band structure, and efficient photogenerated electron-hole separation capabilities.

[0004] Bismuth oxyhalides have a layered crystal structure, and their [Bi₂O₂]... 2+ The layers of metalloporphyrins are stacked alternately with halogen atoms, and the layers are bonded together by van der Waals forces. Due to their π-conjugated macrocyclic structure and nitrogen-containing coordination centers, metalloporphyrin compounds exhibit unique advantages in light absorption and photogenerated electron transfer, showing great potential for application in photocatalysis. However, it should be noted that single metalloporphyrin catalysts are difficult to effectively promote carbon-carbon coupling reactions in C1 intermediates, resulting in low efficiency in the formation of high-value-added C2 products. This problem restricts the further application of metalloporphyrins in the photocatalytic reduction of CO2 to prepare multi-carbon products, highlighting the necessity of constructing composite photocatalytic systems of metalloporphyrins and functionalized bismuth oxyhalide. Summary of the Invention

[0005] To address the problems of low carbon-carbon coupling efficiency, poor photogenerated electron transfer efficiency, and reduction products mainly limited to C1 compounds in the CO2 reduction process of existing photocatalysts, the present invention aims to provide a metal porphyrin-bismuth halide composite catalyst with an amide functional interface, its preparation method, and its application in the photocatalytic CO2 reduction reaction.

[0006] The composite catalyst constructed in this invention promotes efficient carbon-carbon coupling and multi-electron synergistic transfer of C1 intermediates through precise control of the interface structure, thereby significantly improving the selectivity and generation rate of CO2 to high-value-added multi-carbon products (such as ethylene).

[0007] The synthesis of the metal porphyrin-bismuth oxyhalide composite catalyst with amide functional interface of the present invention is as follows: First, bismuth oxyhalide with a layered crystal structure and rich in hydroxyl groups on the surface is synthesized; second, an amino silane coupling agent is used to react with the hydroxyl groups on the surface of bismuth oxyhalide to introduce amino groups to achieve surface amino functionalization; finally, the amino groups are bridged with the carboxyl groups on the metal porphyrin molecule to construct a stable composite structure with amide functional interface.

[0008] The catalyst design of this invention realizes the covalent chemical bond connection between bismuth oxyhalide and metal porphyrin, forming a stable and efficient interfacial coupling structure and electron transport channel, thereby improving the efficiency of photogenerated electron-hole separation and the generation of C2 products.

[0009] The technical solution adopted in this invention is as follows: A metal porphyrin-bismuth halide composite catalyst with an amide functional interface, wherein the composite catalyst is formed by chemical bonding between amino-functionalized bismuth halide and metal porphyrin, wherein the amino groups on the surface of the amino-functionalized bismuth halide undergo a condensation reaction with the carboxyl groups in the metal porphyrin molecule to form a composite structure connected by amide bonds. The amino-functionalized bismuth oxyhalide is prepared by the following steps: first, bismuth oxyhalide with a layered crystal structure is synthesized, the crystal structure of which is composed of alternating stacked bismuth oxygen layers and halogen layers, the layers are bonded by van der Waals forces, and its surface is rich in hydroxyl groups; then, an aminosilane coupling agent is used to react with the hydroxyl groups on the surface of the bismuth oxyhalide to graft amino groups onto the surface of the bismuth oxyhalide, thereby obtaining amino-functionalized bismuth oxyhalide. The metalloporphyrin is 5,10,15,20-tetra(4-carboxyphenyl)metalloporphyrin, and the metal is selected from Co. 2+ Cu 2+ Fe 2+ Zn 2+ or Ni 2+ .

[0010] Furthermore, the preparation method of the amino-functionalized bismuth halide includes the following steps: Step 1: Dissolve erythritol and bismuth nitrate in deionized water, add potassium salt and stir to mix, wherein the potassium salt is potassium bromide, potassium chloride or potassium iodide; Step 2: Transfer the reaction solution obtained in Step 1 to a reaction vessel, seal the reaction vessel, and react at 160~190℃ for 10~15 hours; Step 3: After the reaction is complete, the product is centrifuged, washed and dried to obtain hydroxyl-functionalized bismuth halide. Step 4: Disperse the hydroxyl-functionalized bismuth oxyhalide in a mixed solution of ethanol and water, add an aminosilane coupling agent dropwise, and add acetic acid to adjust the pH of the reaction system to 4-6. Stir the reaction at room temperature for 4-8 hours, and then centrifuge, wash and dry to obtain amino-functionalized bismuth oxyhalide.

[0011] Furthermore, in step 1, the molar ratio of potassium salt to bismuth nitrate is 0.5~2:1, the molar amount of erythritol is 10~30 times the molar amount of bismuth nitrate, and the dispersion concentration of bismuth nitrate in the reaction solution is 0.02~0.03 mol / L.

[0012] Further, the aminosilane coupling agent mentioned in step 4 is 3-aminopropyltriethoxysilane, and the mass of the aminosilane coupling agent is 40-60% of the mass of the hydroxyl-functionalized bismuth halooxygenate.

[0013] Furthermore, in step 4, the volume ratio of ethanol to water is 8~10:1.

[0014] The preparation method of the composite catalyst of the present invention includes: dispersing amino-functionalized bismuth oxyhalide and metal porphyrin in N,N-dimethylformamide at a mass ratio of 1:0.5%~2%, mixing and sonicating for 10~40 minutes, and reacting at 90~100℃ for 5~8 hours; after the reaction is completed, cooling to room temperature, centrifuging, washing and drying to obtain a metal porphyrin-bismuth oxyhalide composite catalyst with an amide functional interface.

[0015] This invention also discloses the application of the composite catalyst in the photocatalytic reduction of CO2: the composite catalyst is uniformly loaded onto a quartz fiber filter membrane and placed on a glass tripod, which is then placed in a quartz reactor. Deionized water is added to the bottom of the quartz reactor. After vacuuming and replacing the membrane with high-purity CO2, CO2 at 20~200 kPa is introduced. After the system reaches adsorption equilibrium, a xenon lamp with a power of 100~500W is used as the light source for visible light irradiation. The photocatalytic reaction is carried out at 2~10℃ to achieve the reduction and conversion of CO2.

[0016] Compared with the prior art, the present invention has the following advantages and innovations: 1) Interface engineering innovation: In the catalyst of this invention, the combination of metal porphyrin and bismuth oxyhalide is no longer limited to the formation of Bi-O bond by oxygen defect. Instead, an amide functional interface between bismuth oxyhalide and metal porphyrin is constructed through an aminosilane coupling agent, which expands the applicability of the two-phase material, realizes stable covalent chemical bonding, and significantly enhances the interface electronic coupling and charge transport efficiency.

[0017] 2) Multi-electron synergistic mechanism: In the catalyst of this invention, bismuth oxyhalide provides excellent light absorption and carrier separation capabilities, while metalloporphyrin provides selective CO2 adsorption and carbon-carbon coupling active centers. The synergistic effect of the two significantly promotes the formation of C2 products (ethylene).

[0018] 3) High stability and reusability: The layered crystal structure of bismuth oxyhalide ensures the structural and chemical stability of the system. Amino modification and amide bond connection improve the binding strength between bismuth oxyhalide and metal porphyrin, enabling the catalyst to maintain high photocatalytic activity in multiple cycles of reaction. Attached Figure Description

[0019] Figure 1 This is a scanning electron microscope image of the composite catalyst CoTCPP / BiOBr-NH2 obtained in Example 1.

[0020] Figure 2 The powder X-ray diffraction patterns of the composite catalysts CoTCPP / BiOBr-NH2 and BiOBr-NH2 obtained in Example 1 are shown below. Figure 3 Fourier transform infrared spectra of the composite catalysts CoTCPP / BiOBr-NH2 and CoTCPP obtained in Example 1. Figure 4 Electrochemical impedance spectroscopy diagrams of the composite catalysts CoTCPP / BiOBr-NH2, BiOBr-NH2, and CoTCPP obtained in Example 1; Figure 5 The graph shows the Mott-Schottky curve of the composite catalyst CoTCPP / BiOBr-NH2 obtained in Example 1. Figure 6 The photocatalytic experiment of the present invention was carried out according to the method of Example 2, and the results of the catalytic carbon dioxide reduction performance when the photocatalysts used were CoTCPP / BiOBr-NH2 and BiOBr-NH2 of Example 1; Figure 7 The photocatalytic experiment of the present invention was carried out according to the method of Example 2, and the photocatalyst used was CuTCPP / BiOBr-NH2 of Control Example 1. The results showed the catalytic performance of carbon dioxide reduction. Figure 8 The photocatalytic experiment of the present invention was carried out according to the method of Example 2, and the photocatalyst was CoTCPP / BiOBr-OH of Control Example 2. The results showed the catalytic performance of carbon dioxide reduction. Figure 9 The results of the photocatalytic performance of this invention, which was tested in a cycle according to the method of Example 2, show the catalytic performance of carbon dioxide reduction when the photocatalyst used was CoTCPP / BiOBr-NH2 from Example 1. Detailed Implementation

[0021] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0022] Example 1: Synthesis of CoTCPP / BiOBr-NH2, a metal porphyrin-bismuth halide composite catalyst with an amide functional interface, comprising the following steps: 1) Bismuth nitrate pentahydrate (2 mmol) and erythritol (41 mmol) were dissolved in 40 mL of deionized water. With continuous stirring, 40 mL of potassium bromide aqueous solution (0.05 mol / L) was added dropwise. The reaction solution was transferred to a 100 mL polytetrafluoroethylene reactor, sealed, and then placed in an oven and heated to 180 °C for 12 h. After the reaction, the mixture was cooled to room temperature, centrifuged, washed three times with ethanol and deionized water, and then dried in a vacuum oven at 80 °C for 6 h to obtain hydroxylated bismuth oxybromooxy (BiOBr-OH). 0.5 g of hydroxylated bismuth oxybromooxy was added to 45 mL of ethanol and 5 mL of water and stirred. 300 µL (approximately 0.284 g) of 3-aminopropyltriethoxysilane was added dropwise, and a small amount of acetic acid was added dropwise until the pH of the solution reached 6. The mixture was stirred at room temperature for 6 h. After the reaction was completed, the product was cooled to room temperature, centrifuged, washed three times with ethanol, and then dried in a vacuum oven at 80°C for 6 h to obtain amino-functionalized bismuth oxybromide (BiOBr-NH2).

[0023] 2) Take 13.8 g of methyl p-formylbenzoate in a round-bottom flask, add 300 mL of propionic acid, heat to 145 °C under N2 protection, and add 6 g of redistilled pyrrole dropwise in the dark. After the addition is complete, continue the reaction for 2 h. After the reaction is complete, cool to room temperature, collect the product by vacuum filtration, wash with methanol, and then purify by silica gel column chromatography. Dry in a vacuum oven at 90 °C for 8 h to obtain 5,10,15,20-tetra(4-formylphenyl)porphyrin. Take 0.847 g of 5,10,15,20-tetra(4-formylphenyl)porphyrin in a round-bottom flask, add 100 mL of N,N-dimethylformamide, and then add 3.19 g of cobalt acetate tetrahydrate. React at 153 °C for 12 h under N2 protection. After the reaction was completed, the mixture was cooled to room temperature. The solid obtained by vacuum distillation was dissolved in 100 mL of dichloromethane and extracted with distilled water (3 × 500 mL). The lower organic phase was collected, dried over anhydrous magnesium sulfate, filtered, and then distilled under reduced pressure to obtain the crude product. The crude product was then separated and purified by silica gel column chromatography and dried in a vacuum oven at 90 °C for 8 h to obtain the precursor of the metalloporphyrin. 1.60 g of the precursor was placed in a round-bottom flask, and 50 mL of tetrahydrofuran, 50 mL of methanol, 50 mL of deionized water, and 5.26 g of potassium hydroxide were added. The mixture was reacted at 80 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature and distilled under reduced pressure. The solid was dissolved in 400 mL of deionized water, filtered, and the filtrate was added under stirring to adjust the pH to 2. The mixture was stirred for another 30 min. The sample was filtered and washed with deionized water, then dried in a vacuum oven at 90°C for 8 h to obtain 5,10,15,20-tetra(4-carboxyphenyl)porphyrin (CoTCPP) with Co as the central metal ion.

[0024] 3) At room temperature, 0.1 g BiOBr-NH2 was added to 30 mL of N,N-dimethylformamide and stirred vigorously for 20 min. Then, 1 mg CoTCPP was added and stirred for another 20 min. The mixture was then reacted at 90 °C for 5 h. The mixture was washed with N,N-dimethylformamide and ethanol and then dried under vacuum at 80 °C to obtain the metal porphyrin-halooxybismuth composite catalyst CoTCPP / BiOBr-NH2 with an amide functional interface.

[0025] 4) Preparation method of electrochemical impedance spectroscopy (EIS) working electrode: Preparation of S1 catalyst dispersion: 4 mg of catalyst powder was dispersed in 600 μL of deionized water, 400 μL of ethanol and 80 μL of Nafion binder. The mixture was ultrasonically treated to make the material dispersed evenly, and the catalyst dispersion was obtained.

[0026] S2 carbon cloth loading: Take 10 μL of catalyst dispersion onto carbon cloth (1 cm × 1.5 cm), then put it into a vacuum oven at 60℃ to dry before starting electrochemical impedance spectroscopy.

[0027] 5) Mott-Schottky curve test S1: Using the composite catalyst CoTCPP / BiOBr-NH2 obtained in Example 1 as the test sample, 4 mg of the test sample was dispersed in 600 μL of deionized water, 400 μL of ethanol and 80 μL of Nafion binder. The mixture was ultrasonically treated to make the material dispersed evenly, and the catalyst dispersion was obtained. S2: Take 10 μL of catalyst dispersion onto a carbon rod, then place it in a vacuum oven at 60℃ to dry before starting the Mott-Schottky curve test.

[0028] S3: Three-electrode system test, the electrolyte is 0.5 mol / L Na2SO4 solution, the reference electrode is Ag / AgCl electrode, the platinum electrode is the counter electrode, and the working electrode is a carbon rod with the sample to be tested; S4: Test within a certain voltage range (-1 ~ 1 V vs Ag / AgCl), changing the test frequency (500, 1000, and 1500 Hz) to obtain the corresponding test curves. The test results at different frequencies are shown below. Figure 5 .

[0029] The scanning electron microscope (SEM) image of the composite catalyst CoTCPP / BiOBr-NH2 obtained in Example 1 is shown below. Figure 1 As shown, from Figure 1 It can be seen that the amino-functionalized bismuth oxybromide is in the form of thin sheets, stacked layer by layer, and has a certain degree of surface roughness after being combined with metal porphyrin.

[0030] Example 1 shows the powder X-ray diffraction patterns of the composite catalysts CoTCPP / BiOBr-NH2 and BiOBr-NH2 as follows: Figure 2 As shown, the diffraction peaks of the composite catalyst CoTCPP / BiOBr-NH2 are consistent with those of BiOBr. No characteristic peaks of other impurities or phases were detected, indicating that the structure of bismuth oxybromooxygenate was not damaged before and after amino functionalization or before and after composite with CoTCPP, further demonstrating the successful preparation of the bismuth oxybromooxygenate composite in CoTCPP / BiOBr-NH2.

[0031] Example 1: The Fourier transform infrared spectra of the composite catalysts CoTCPP / BiOBr-NH2 and CoTCPP are shown below. Figure 3As shown, infrared analysis of CoTCPP / BiOBr-NH2 reveals the stretching vibration peaks of Bi-O and the bending vibration peaks of NH, indicating successful amino-functionalized bismuth oxyhalide composite. The N-Co peak confirms successful metallization of 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin. (1690 cm⁻¹) -1 The characteristic peak at 1515 cm⁻¹ corresponds to the C=O stretching vibration. -1 The peak at the position corresponds to the NH bending vibration and CN stretching vibration coupled to the amide II band, indicating the formation of the functional interface of the composite catalyst CoTCPP / BiOBr-NH2 amide.

[0032] Example 1 yielded composite catalysts CoTCPP / BiOBr-NH2, BiOBr-NH2, and CoTCPP. A carbon cloth electrode was prepared according to step S2 of Example 1 (4). Electrochemical impedance spectroscopy was performed using the prepared carbon cloth electrode. The electrochemical impedance spectroscopy results for CoTCPP / BiOBr-NH2, BiOBr-NH2, and CoTCPP as catalysts are shown below. Figure 4 As shown, the radius of the arc of CoTCPP / BiOBr-NH2 is smaller than that of BiOBr-NH2 and CoTCPP, indicating that the composite catalyst has a smaller interfacial charge transfer resistance and improved electron mobility, which is beneficial to the interfacial charge transfer process in photocatalysis and further enhances the photocatalytic performance.

[0033] Example 1 shows the Mott-Schottky curve of the composite catalyst CoTCPP / BiOBr-NH2 as follows: Figure 5 As shown, the vertical axis of the curve is the reciprocal of the square of the capacitance. The characteristics of the semiconductor can be determined by the curve. The slope of the straight part of the curve is positive, indicating that the material is an n-type semiconductor.

[0034] Example 2: 30 mg of photocatalyst was uniformly loaded onto a quartz fiber filter membrane and placed on a glass tripod in a quartz reactor. 5 mL of deionized water was added to the bottom of the reactor (the deionized water did not contact the photocatalyst). The reactor was then connected to a photocatalytic testing system. The reactor was subjected to three vacuum-purging and gas-displacement treatments using high-purity CO2 to remove air from the reaction system. CO2 was then introduced again to maintain the CO2 pressure in the reaction system at approximately 80 kPa. After the system reached equilibrium, a 300 W xenon lamp was used as the reaction light source for visible light irradiation. The reaction system temperature was maintained at 5°C using a low-temperature constant-temperature water bath system. A gas chromatograph automatically took samples for analysis every 30 minutes or 1 hour. After reacting under visible light for 5 hours, the yields of photocatalytic CO2 reduction to ethylene, methane, carbon monoxide, and other components were calculated.

[0035] Following the above photocatalytic experimental procedure, when the photocatalysts used were CoTCPP / BiOBr-NH2 and BiOBr-NH2 from Example 1, the products of photocatalytic CO2 reduction and the corresponding generation rates are shown below. Figure 6 The yields of the photocatalytic reduction products CO, CH4, and C2H4 were recorded. Figure 6 The yield data is the rate of the catalytic reaction after 5 hours.

[0036] pass Figure 6 It can be seen that the CoTCPP / BiOBr-NH2 prepared by the method of Example 1 is beneficial to increasing the yield of ethylene, a C2 compound with higher added value, in the photocatalytic CO2 reduction reaction.

[0037] To verify the cycling stability of the photocatalyst, four cycles were performed on the composite catalyst CoTCPP / BiOBr-NH2. The test results are shown below. Figure 9 The results of each cycle test are the average rates of different photocatalytic reduction products after 5 hours of catalytic reaction, indicating that the composite catalyst CoTCPP / BiOBr-NH2 has good cycle stability.

[0038] Comparative Example 1: The metal porphyrin-bismuth halide composite catalyst CuTCPP / BiOBr-NH2 with an amide functional interface was synthesized by repeating the steps of Example 1, except that in "step 2), cobalt acetate tetrahydrate was replaced with an equal molar amount of copper acetate monohydrate", and the other conditions remained unchanged, and the composite catalyst CuTCPP / BiOBr-NH2 was finally obtained.

[0039] Following the photocatalytic experiment procedure of Example 2, the photocatalyst used was CuTCPP / BiOBr-NH2 from Control Example 1. The products of photocatalytic CO2 reduction and the corresponding formation rates are shown below. Figure 7 .

[0040] Comparative Example 2: The metalloporphyrin-hydroxy functionalized bismuth halooxygenate composite catalyst CoTCPP / BiOBr-OH was synthesized as follows: 0.1 g BiOBr-OH was added to 30 mL of N,N-dimethylformamide at room temperature and stirred vigorously for 20 min. Then, 1 mg CoTCPP was added and stirring was continued for another 20 min. The mixture was then reacted at 90 °C for 5 h. After washing with N,N-dimethylformamide and ethanol, the mixture was dried under vacuum at 80 °C to finally obtain the composite catalyst CoTCPP / BiOBr-OH.

[0041] Following the photocatalytic experiment procedure of Example 2, the photocatalyst used was CoTCPP / BiOBr-OH from Control Example 2. The products of photocatalytic CO2 reduction and the corresponding generation rates are shown below. Figure 8 .

[0042] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A metal porphyrin-bismuth halide composite catalyst with an amide functional interface, characterized in that, The composite catalyst is formed by chemical bonding between amino-functionalized bismuth oxyhalide and metal porphyrin. The amino groups on the surface of the amino-functionalized bismuth oxyhalide undergo a condensation reaction with the carboxyl groups in the metal porphyrin molecules to form a composite structure connected by amide bonds. The amino-functionalized bismuth oxyhalide is prepared by the following steps: First, bismuth oxyhalide with a layered crystal structure is synthesized. Its crystal structure is composed of alternating stacks of bismuth oxygen layers and halogen layers, which are bonded by van der Waals forces and its surface is rich in hydroxyl groups. Then, an aminosilane coupling agent is used to perform a condensation reaction with the hydroxyl groups on the surface of the bismuth oxyhalide to graft amino groups onto the surface of the bismuth oxyhalide, thereby obtaining amino-functionalized bismuth oxyhalide. The metalloporphyrin is 5,10,15,20-tetra(4-carboxyphenyl)metalloporphyrin, and the metal is selected from Co. 2+ Cu 2+ Fe 2+ Zn 2+ or Ni 2+ .

2. The composite catalyst as described in claim 1, characterized in that, The preparation method of the amino-functionalized bismuth halide includes the following steps: Step 1: Dissolve erythritol and bismuth nitrate in deionized water, add potassium salt and stir to mix, wherein the potassium salt is potassium bromide, potassium chloride or potassium iodide; Step 2: Transfer the reaction solution obtained in Step 1 to a reaction vessel, seal the reaction vessel, and react at 160~190℃ for 10~15 hours; Step 3: After the reaction is complete, the product is centrifuged, washed and dried to obtain hydroxyl-functionalized bismuth halide. Step 4: Disperse the hydroxyl-functionalized bismuth oxyhalide in a mixed solution of ethanol and water, add an aminosilane coupling agent dropwise, and add acetic acid to adjust the pH of the reaction system to 4-6. Stir the reaction at room temperature for 4-8 hours, and then centrifuge, wash and dry to obtain amino-functionalized bismuth oxyhalide.

3. The composite catalyst as described in claim 2, characterized in that: In step 1, the molar ratio of potassium salt to bismuth nitrate is 0.5~2:1, the molar amount of erythritol is 10~30 times that of bismuth nitrate, and the concentration of bismuth nitrate in the reaction solution is 0.02~0.03 mol / L.

4. The composite catalyst as described in claim 2, characterized in that: The aminosilane coupling agent mentioned in step 4 is 3-aminopropyltriethoxysilane, and the mass of the aminosilane coupling agent is 40-60% of the mass of the hydroxyl-functionalized bismuth halide.

5. The composite catalyst as described in claim 2, characterized in that: In step 4, the volume ratio of ethanol to water is 8~10:

1.

6. The method for preparing the composite catalyst as described in claim 1, characterized in that: Aminofunctionalized bismuth oxyhalide and metalloporphyrin were co-dispersed in N,N-dimethylformamide at a mass ratio of 1:0.5%~2%. After mixing and sonicating for 10~40 minutes, the mixture was reacted at 90~100℃ for 5~8 hours. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, washed and dried to obtain a metalloporphyrin-bismuth oxyhalide composite catalyst with an amide functional interface.

7. The application of the composite catalyst as described in claim 1 in the photocatalytic reduction of CO2 reaction.

8. The application as described in claim 7, characterized in that: The composite catalyst was uniformly loaded onto a quartz fiber filter membrane and placed on a glass tripod in a quartz reactor. Deionized water was added to the bottom of the reactor, and after vacuuming and replacement with high-purity CO2, CO2 at 20-200 kPa was introduced. After the system reached adsorption equilibrium, a xenon lamp with a power of 100-500W was used as the light source for visible light irradiation, and photocatalytic reaction was carried out at 2-10℃ to achieve the reduction and conversion of CO2.

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