A type A3B cobalt metal porphyrin-bismuth halide composite material, its preparation method and its application in photocatalytic CO2 reduction.

Abstract

The application discloses an A3B type cobalt metal porphyrin-halogen bismuth composite material and a preparation method and photocatalytic CO2 reduction application thereof. The composite material is a heterojunction structure composed of A3B type cobalt metal porphyrin and halogen bismuth. The halogen bismuth is Bi3O4Br, and the A3B type cobalt metal porphyrin is 5-(4-carboxylphenyl)-10,15,20-tris(4-methoxyphenyl) porphyrin cobalt (II). The composite material can solve the technical problem that photogenerated carriers are difficult to be directionally separated in the existing halogen bismuth photocatalyst, and the conversion rate of CO2 reduction product CO is low, and has good light absorption performance and the performance of photocatalytic reduction of CO2 to CO.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic material preparation and CO2 resource utilization technology, specifically involving an A3B type cobalt metal porphyrin-bismuth oxyhalide composite material, its preparation method and photocatalytic CO2 reduction application. Background Technology

[0002] Photocatalytic CO2 reduction technology has become a highly promising CO2 resource recovery technology due to its mild reaction conditions and the use of clean solar energy. Many effective strategies for improving the performance of photocatalytic CO2 reduction have been developed, such as constructing heterojunctions, loading metals, doping with non-metallic elements, defect engineering, and surface photosensitization. Among these, constructing heterojunctions is one of the most widely studied methods for improving photocatalyst performance.

[0003] Bismuth oxyhalides (BiOX, where X = F, Cl, Br, and I) are a novel type of photocatalyst. Bismuth oxyhalides are chemically inert, harmless, and corrosion-resistant in aqueous media. 3+ Bismuth oxyhalides exhibit high visible light photocatalytic activity due to their narrow band gap resulting from the hybridization of O 2p and Bi 6s valence bands.

[0004] Porphyrin compounds are conjugated cyclic structures with π electrons, exhibiting good electron mobility within the molecular ring. Most porphyrins and their derivatives possess favorable optical properties. Therefore, in recent years, porphyrins have attracted researchers' attention in the field of photocatalytic carbon dioxide reduction.

[0005] Forming a heterojunction by combining porphyrin with bismuth oxyhalide is a feasible strategy to improve the photocatalytic CO2 reduction performance of catalysts. Due to the synergistic effect between porphyrin and bismuth oxyhalide, the visible light absorption range is increased and electron-hole pair recombination is hindered, thereby improving the conversion rate of CO, the CO reduction product.

[0006] Compared to previously reported metalloporphyrin-based flexible conjugated organic polymer-halogen bismuth composite materials, the material of this invention has a significant advantage in economic cost because the metalloporphyrin content in its composition is extremely low, about 1-3 wt%. Summary of the Invention

[0007] To address the technical problems of narrow light absorption range and low CO2 conversion rate of traditional bismuth oxyhalide photocatalysts, the present invention aims to provide an A3B type cobalt metal porphyrin-bismuth oxyhalide composite material, its preparation method, and its application. The A3B type cobalt metal porphyrin-bismuth oxyhalide composite material provided by the present invention can expand the light absorption range and improve the separation efficiency of photogenerated carriers, thereby increasing the conversion rate of CO, the photocatalytic CO2 reduction product.

[0008] The preparation mechanism of the A3B type cobalt metal porphyrin-bismuth oxyhalide composite material of the present invention is that the A3B type cobalt metal porphyrin forms a Bi-O bond with the bismuth oxyhalide through the carboxyl group in the exocyclic group, thus obtaining a type II heterojunction composite.

[0009] The technical solution adopted in this invention is as follows:

[0010] A type A3B cobalt metal porphyrin-bismuth oxyhalide composite material, wherein the composite material is a heterojunction structure formed by combining A3B type cobalt metal porphyrin and bismuth oxyhalide, wherein the bismuth oxyhalide is Bi3O4Br, and the A3B type cobalt metal porphyrin is 5-(4-carboxyphenyl)-10,15,20-tris(4-methoxyphenyl)porphyrin cobalt(II), which is labeled as Co-OCPP.

[0011] Furthermore, the A3B type cobalt metal porphyrin is prepared according to the following method:

[0012] Step 1: Synthesize 5-(4-methoxycarbonylphenyl)-10,15,20-tris(4-methoxyphenyl)-21H,23H-porphyrin, labeled as OMPP, with the following structural formula:

[0013] ;

[0014] Step 2: OMPP reacts with divalent Co salt to synthesize 5-(4-methoxycarbonylphenyl)-10,15,20-tris(4-methoxyphenyl)porphyrin cobalt(II), labeled as Co-OMPP, with the following structural formula:

[0015] ;

[0016] Step 3: After alkaline hydrolysis of the methoxycarbonyl group on the benzene ring of Co-OMPP, acidification was performed to synthesize 5-(4-carboxyphenyl)-10,15,20-tris(4-methoxyphenyl)porphyrin cobalt(II), which was labeled as Co-OCPP, and its structural formula is as follows:

[0017] .

[0018] Furthermore, in step 1, the preparation method of OMPP includes the following steps:

[0019] S1: Methyl p-aldehyde benzoate, p-methoxybenzaldehyde and pyrrole are dissolved in solvent A, and nitrogen gas is introduced to completely remove oxygen from the system;

[0020] S2: Add boron trifluoride diethyl ether complex dropwise to the reaction solution of step S1 as a Lewis acid catalyst, and stir the reaction at room temperature and under nitrogen atmosphere for 0.5~1.5 h to promote the condensation reaction of pyrrole units;

[0021] S3: Add a solution of 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) dropwise to the reaction system of step S2. After the addition is complete, continue stirring at room temperature for 2-3 h to oxidize and aromatize the porphyrin precursor to obtain the crude product.

[0022] S4: The solvent was removed by rotary evaporation to obtain a dark solid residue. The solid was dissolved in dichloromethane and purified by silica gel column chromatography to obtain OMPP.

[0023] Furthermore, the molar ratio of p-methoxybenzaldehyde to methyl p-aldehyde benzoate is 2-4:1, the molar ratio of pyrrole to methyl p-aldehyde benzoate is 3-5:1, and solvent A is chloroform, toluene, or dichloromethane.

[0024] Furthermore, the molar amount of the boron trifluoride diethyl ether complex in step S2 is 30-50% of the molar amount of methyl benzoate in step S1.

[0025] Furthermore, the molar amount of DDQ in step S3 is 6-8 times the molar amount of methyl benzoate in step S1.

[0026] Furthermore, the eluent for column chromatography in step S4 is a mixture of petroleum ether and dichloromethane with a volume ratio of 1 to 1.5:1.

[0027] Furthermore, in step 2, the preparation steps of Co-OMPP specifically include the following steps:

[0028] M1: Under nitrogen protection, OMPP is dissolved in DMF, followed by the addition of divalent Co salt, and the mixture is heated to 150~170℃ and reacted for 12~16 h;

[0029] M2: After the reaction is complete, the mixture is cooled and rotary evaporated. The residue from the rotary evaporation is dissolved in dichloromethane and washed with distilled water to separate the organic phase. The organic phase is dried with anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure to obtain the crude product. The crude product is then purified by silica gel column chromatography to obtain Co-OMPP.

[0030] Furthermore, in step M1, the molar amount of divalent Co salt is 10-15 times the molar amount of OMPP; in step M2, the eluent for column chromatography is dichloromethane.

[0031] The preparation method of the A3B type cobalt metal porphyrin-bismuth halide composite material includes the following steps:

[0032] Step 1: Disperse Co-OCPP and Bi3O4Br in ethanol;

[0033] Step 2: React the mixture at 80~90℃ for 5~8 h;

[0034] Step 3: After the system cools naturally to room temperature, collect the solid product by centrifugation, wash and dry it to complete the preparation.

[0035] Furthermore, the mass ratio of Co-OCPP to bismuth oxyhalide is 0.01~0.03:1.

[0036] This invention also discloses the application of the aforementioned A3B type cobalt metal porphyrin-bismuth halooxygenate composite material in the photocatalytic reduction of CO2. The application method is as follows: using the aforementioned A3B type cobalt metal porphyrin-bismuth halooxygenate composite material as a photocatalyst, the photocatalyst is dispersed in pure water at a concentration of 0.1~1g / L, and the mixture is transferred to a quartz reactor. The reactor is vacuumed and gas-displaced using high-purity CO2 to remove air from the reaction system. Then, CO2 at a pressure of 20~200kPa is introduced into the reactor. After the system is balanced, a 100~500W xenon lamp is used as the reaction light source for illumination. The temperature of the reaction system is maintained at 2~10℃ using a low-temperature constant-temperature water bath system to carry out the photocatalytic CO2 reduction reaction.

[0037] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0038] 1) The A3B type cobalt metal porphyrin-bismuth oxyhalide composite material prepared by the present invention retains the excellent photoelectric properties of the original A3B type metal porphyrin, and introduces bismuth oxyhalide to enrich more electrons, thus having good light absorption performance and photocatalytic reduction of CO2 to CO performance.

[0039] 2) The A3B type cobalt metal porphyrin-bismuth oxyhalide composite material prepared in this invention is formed by the interaction of A3B type metal porphyrin and bismuth oxyhalide through carboxyl groups and Bi. 3+ The coordination interactions between them are tightly combined to form a type II heterojunction composite material. The built-in electric field of this composite material effectively promotes the spatial separation of photogenerated carriers, and it has a wider light absorption range, lower fluorescence intensity and charge transfer impedance, and stronger photocurrent response.

[0040] 3) Bismuth oxyhalide enriches more electrons. Bismuth oxyhalide and A3B type metalloporphyrin form an electron tandem system. Its rationally designed structure can regulate the band structure of the composite material, which helps to improve the conversion rate of photocatalytic CO2 reduction to CO. Attached Figure Description

[0041] Figure 1 Fourier transform infrared spectra of Co-OCPP, Bi3O4Br and Co-OCPP@Bi3O4Br obtained in Example 2;

[0042] Figure 2The powder X-ray diffraction patterns of Co-OCPP, Bi3O4Br and Co-OCPP@Bi3O4Br obtained in Example 2 are shown below.

[0043] Figure 3 The O 1s high-resolution X-ray photoelectron spectrum of Co-OCPP obtained in Example 2;

[0044] Figure 4 The O 1s high-resolution X-ray photoelectron spectrum of Co-OCPP@Bi3O4Br obtained in Example 2;

[0045] Figure 5 The high-resolution C 1s X-ray photoelectron spectrum of Co-OCPP@Bi3O4Br obtained in Example 2;

[0046] Figure 6 The N 1s high-resolution X-ray photoelectron spectrum of Co-OCPP@Bi3O4Br obtained in Example 2;

[0047] Figure 7 The high-resolution X-ray photoelectron spectrum of Co-OCPP@Bi3O4Br obtained in Example 2 is shown below.

[0048] Figure 8 The high-resolution X-ray photoelectron spectrum of Bi 4f of Co-OCPP@Bi3O4Br obtained in Example 2;

[0049] Figure 9 This is a scanning electron microscope image of the Co-OCPP obtained in Example 2;

[0050] Figure 10 This is a scanning electron microscope image of Bi3O4Br obtained in Example 2;

[0051] Figure 11 This is a scanning electron microscope image of Co-OCPP@Bi3O4Br obtained in Example 2;

[0052] Figure 12 This is a transmission electron microscope image of Bi3O4Br obtained in Example 2;

[0053] Figure 13 This is a transmission electron microscope image of Co-OCPP@Bi3O4Br obtained in Example 2 at 50 nm.

[0054] Figure 14 This is a transmission electron microscope image of Co-OCPP@Bi3O4Br obtained in Example 2 at 5 nm.

[0055] Figure 15The elemental distribution diagram of Co-OCPP@Bi3O4Br obtained in Example 2 is shown below.

[0056] Figure 16 The UV-Vis diffuse reflectance spectra of Co-OCPP, Bi3O4Br and Co-OCPP@Bi3O4Br obtained in Example 2 are shown below.

[0057] Figure 17 The bandgap diagram of Co-OCPP obtained in Example 2;

[0058] Figure 18 The band gap diagram of Bi3O4Br obtained in Example 2;

[0059] Figure 19 The band gap diagram of Co-OCPP@Bi3O4Br obtained in Example 2;

[0060] Figure 20 The electrochemical impedance spectroscopy curves of Co-OCPP, Bi3O4Br and Co-OCPP@Bi3O4Br obtained in Example 2 are shown.

[0061] Figure 21 The photoresponse current curves of Co-OCPP, Bi3O4Br and Co-OCPP@Bi3O4Br obtained in Example 2 are shown.

[0062] Figure 22 The photoluminescence spectra of Co-OCPP, Bi3O4Br, and Co-OCPP@Bi3O4Br obtained in Example 2 are shown below.

[0063] Figure 23 The graph shows the Mott-Schottky curve of Co-OCPP obtained in Example 2.

[0064] Figure 24 The Mott-Schottky curve of Bi3O4Br obtained in Example 2 is shown.

[0065] Figure 25 The Mott-Schottky curve of Co-OCPP@Bi3O4Br obtained in Example 2 is shown.

[0066] Figure 26 The graph shows the photocatalytic carbon dioxide reduction performance of Co-OMPP and Co-OCPP in Example 3;

[0067] Figure 27 The graph shows the photocatalytic carbon dioxide reduction performance of Co-OCPP, Bi3O4Br, and Co-OCPP@Bi3O4Br in Example 3.

[0068] Figure 28The graph shows the cyclic stability test results of Co-OCPP@Bi3O4Br in Example 3.

[0069] Figure 29 The results show the catalyst-free control conditions in Example 3, and the photocatalytic control results of the Co-OCPP@Bi3O4Br photocatalyst under different conditions;

[0070] Figure 30 The graph shows a comparison of the photocatalytic carbon dioxide reduction performance of the five materials obtained in Examples 2, 4, 5 and 6. Detailed Implementation

[0071] 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.

[0072] Example 1: Synthesis of 5-(4-methoxycarbonylphenyl)-10,15,20-tris(4-methoxyphenyl)-21H,23H-porphyrin (OMPP), comprising the following steps:

[0073] Under nitrogen protection, methyl p-aldehyde benzoate (0.41 g, 2.5 mmol), p-methoxybenzaldehyde (1.01 g, 7.5 mmol), and pyrrole (0.67 g, 10 mmol) were added sequentially to a 500 mL three-necked flask containing 300 mL of chloroform. Nitrogen gas was continuously bubbled through the flask for 40 min to thoroughly remove oxygen from the system. Subsequently, a boron trifluoride diethyl ether complex solution (BF3·Et2O, 0.125 mL, 1 mmol) was added dropwise to the reaction solution as a Lewis acid catalyst, and the reaction was continued to be stirred for 50 min at room temperature under a nitrogen atmosphere to promote the condensation reaction of the pyrrole units. Then, 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ, 2.04 g, 18 mmol) was dissolved in 30 mL of toluene and slowly added dropwise to the above reaction system. After the addition was complete, the mixture was stirred at room temperature for 2 h to oxidize and aromatize the porphyrin precursor, yielding crude A3B type porphyrin. After the reaction was complete, the solvent was removed by rotary evaporation, yielding a dark solid residue. This solid was dissolved in a suitable amount of dichloromethane and purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane, volume ratio 1:1). The target product band was collected, and the solvent was removed by rotary evaporation to obtain 0.34 g of pure A3B type porphyrin (5-(4-methoxycarbonylphenyl)-10,15,20-tris(4-methoxyphenyl)-21H,23H-porphyrin, labeled OMPP), with a yield of 18%.

[0074] The 1H NMR spectrum of 5-(4-methoxycarbonylphenyl)-10,15,20-tris(4-methoxyphenyl)-21H,23H-porphyrin (OMPP) prepared in Example 1 is as follows: 1H NMR (400 MHz, Chloroform-d) δ 8.91 –8.86 (m, 6H, Por-CH), 8.78 (d, J = 4.7 Hz, 2H, Por-CH), 8.44 (d, J = 8.2 Hz,2H, Ar-CH), 8.31 (d, J = 8.1 Hz, 2H, Ar-CH), 8.13 (dd, J = 8.6, 2.2 Hz, 6H,Ar-CH), 7.29 (d, J = 8.5 Hz, 6H, Ar-CH), 4.12 (s, 3H, COOCH3), 4.10 (s, 9H,OCH3), -2.75 (s, 2H, NH). In the aromatic ring hydrogen signals (δ 8.44 - 7.29), the benzene ring hydrogens attached to the methoxy group shift significantly to higher fields (δ 8.13, 7.29) due to the strong electron-donating conjugation effect of the oxygen atom, which is the most prominent feature of this structure. The two singlets at δ 4.12 and δ 4.10 correspond to the ester group and the three methoxy groups (-OCH3), respectively.

[0075] The high-resolution mass spectra of 5-(4-methoxycarbonylphenyl)-10,15,20-tris(4-methoxyphenyl)-21H,23H-porphyrin (OMPP) prepared in Example 1 are as follows: HRMS (ESI) + m / z: Calcd for C 49 H 39 N4O5:763.2915, found 763.2913.

[0076] Example 2: Synthesis and photoelectric performance testing of 5-(4-carboxyphenyl)-10,15,20-tris(4-methoxyphenyl)porphyrin cobalt(II) (Co-OCPP), Bi3O4Br, and Co-OCPP@Bi3O4Br composites, including the following steps:

[0077] 1) The OMPP (0.76 g, 1 mmol) obtained in Example 1 was placed in a 500 mL three-necked round-bottom flask, and 100 mL of N,N-dimethylformamide (DMF) was added to dissolve it. Then, cobalt acetate tetrahydrate (3.24 g, 13 mmol) was added. Under nitrogen protection, the reaction mixture was heated to 153 °C and stirred under reflux for 12 h. After the reaction was complete, the system was allowed to cool naturally to room temperature, and most of the solvent was removed by vacuum distillation. The resulting residual solid was dissolved in 100 mL of dichloromethane and washed three times with distilled water (500 mL each time). The organic phase was separated, dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography using dichloromethane as the eluent. The target component was collected, concentrated by rotary evaporation under reduced pressure, and dried in a vacuum drying oven at 80℃ for 6 h to obtain 0.47 g of the orange-red solid product 5-(4-methoxycarbonylphenyl)-10,15,20-tris(4-methoxyphenyl)porphyrin cobalt(II) (Co-OMPP), with a yield of 57%.

[0078] 2) The Co-OMPP (1.45 g, 1.77 mmol) obtained in step 1), 50.0 mL tetrahydrofuran, 50.0 mL distilled water, 50.0 mL methanol, and 5.260 g potassium hydroxide (93.75 mmol) were added to a 100 mL single-necked round-bottom flask. The mixture was refluxed at 80 °C for 12.0 h, and the reaction was stopped. After natural cooling to room temperature, the mixture was distilled under reduced pressure to obtain a purple-red solid. The solid was dissolved in 400.0 mL distilled water and then filtered. 2.0 mol / L hydrochloric acid was added dropwise to the filtrate with stirring until the pH reached 2.0. The mixture was stirred for another 50 min, and the filter cake was obtained by suction filtration. The filter cake was washed with distilled water (3 × 200.0 mL) to obtain an orange-red filter cake. The filter cake was dried in a vacuum drying oven at 90 °C for 8.0 h to obtain an orange-red solid 5-(4-carboxyphenyl)-10,15,20-tris(4-methoxyphenyl)porphyrin cobalt(II) (Co-OCPP). 1.27g, yield 89%.

[0079] 3) Bi(NO3)3·5H2O (0.242 g, 0.5 mmol) and 0.2 g PVP were dissolved together in 15 mL of 0.1 M mannitol solution. Then, a dispersion of 0.5 mmol NaBr dispersed in 3 mL of 0.1 M mannitol solution was added, and the mixture was stirred vigorously for 30 minutes. Next, the pH of the mixture was adjusted to 11.5 using 2 mol / L NaOH solution. The reaction mixture was transferred to a 25 mL polytetrafluoroethylene-lined autoclave, sealed, and reacted at 160 °C for 24 hours. After the reaction, the product was collected by centrifugation and washed successively with deionized water and ethanol to remove impurities. Finally, it was vacuum dried at 60 °C to obtain 0.176 g of Bi3O4Br sample, with a yield of 46%.

[0080] 4) The obtained Bi3O4Br powder (2g) was dispersed in 300 mL of ethanol and ultrasonically treated to obtain a uniform dispersion. Subsequently, the Co-OCPP (0.03g) obtained in step 2) was added to the dispersion. The mixture was refluxed in an oil bath at 85°C for 6 hours. After the reaction was completed, the solid product was collected by centrifugation, washed several times with ethanol, and finally dried to obtain 1.59g of Co-OCPP@Bi3O4Br composite material, with a yield of 80%.

[0081] 5) Preparation methods of Eis and IT working electrodes:

[0082] S1: The Co-OCPP, Bi3O4Br and Co-OCPP@Bi3O4Br powders obtained in Example 2 were used as catalysts for testing. 4 mg of catalyst powder was dispersed in 960 μL of anhydrous ethanol and 40 μL of Nafion binder. The mixture was ultrasonically treated for 24 h to make the material dispersed evenly, and the catalyst dispersion was obtained.

[0083] S2: Take 200 μL of the catalyst dispersion and apply it to carbon cloth (0.5 cm × 2 cm) in 8 portions (25 μL × 8), obtaining approximately 0.8 mg·cm⁻¹. -2 The catalyst loading is determined, and then the catalyst is dried in a vacuum oven at 60°C before electrochemical impedance spectroscopy can be performed.

[0084] S3 FTO glass support: Take 200μL of catalyst dispersion and apply it to the conductive surface of FTO glass (16.6×12.5 mm) in 8 portions (25μL×8). Then place it in a vacuum oven at 60℃ to dry before starting transient photocurrent testing.

[0085] 6) Mott-Schottky test:

[0086] S1: The Co-OCPP, Bi3O4Br and Co-OCPP@Bi3O4Br powders obtained in Example 2 were used as catalysts, and the catalysts were used as test samples. 4 mg of catalyst powder was dispersed in a mixture of 400 µL of ethanol and 600 µL of water. After ultrasonic dispersion, a conductive glass sheet was immersed in the mixture. After thorough immersion, it was dried to obtain a conductive glass sheet with the test sample.

[0087] S2: Three-electrode system test, the electrolyte is 0.1mol / L Na2SO4 solution, the reference electrode is Ag / AgCl electrode, the counter electrode is platinum electrode, and the working electrode is conductive glass with the sample to be tested;

[0088] S3: Perform tests within a certain voltage range (-1 ~ 1 V vs Ag / AgCl), and change the test frequency (1000, 1500, and 2000 Hz) to obtain the corresponding test curves.

[0089] The Fourier transform infrared spectra of the Co-OCPP, Bi3O4Br, and Co-OCPP@Bi3O4Br composite materials prepared in Example 2 are shown below. Figure 1 As shown, from Figure 1 It can be seen that no characteristic peak of the NH stretching vibration on the porphyrin ring was detected in Co-OCPP, indicating that Co metal coordination replaced the NH bond. Similar to Co-OMPP, Co-OCPP showed a peak at 2950 cm⁻¹. -1 and 2850 cm -1 The aliphatic CH stretching vibration at this location proves that Co-OCPP is obtained based on the carboxylation of Co-OMPP porphyrin. Furthermore, at 1680 cm⁻¹... -1 The characteristic C=O stretching vibration appears at this point, corresponding to the carboxyl functional group on Co-OCPP. As an inorganic compound, Bi3O4Br's infrared spectrum mainly shows a C=O stretching vibration at 830 cm⁻¹. -1 The stretching vibration of the Bi-O bond at this location. Additionally, it should be noted that due to the adsorption of hydrated CO2 in the air, the infrared spectrum of Bi3O4Br is at 1380 cm⁻¹. -1 Characteristic peaks of surface carbonates appeared at that location.

[0090] For the Co-OCPP@Bi3O4Br composite material, its infrared spectrum is roughly a superposition of the peaks of Co-OCPP and Bi3O4Br. However, it should be noted that, in terms of peak intensity, 1680 cm⁻¹... -1 The C=O stretching vibration peak at this location is significantly weakened compared to Co-OCPP. Meanwhile, at 1640 cm⁻¹... -1 and 1380 cm -1A pair of new peaks appeared. Based on the peak shapes above, it can be determined that the carboxyl groups in Co-OCPP are deprotonated and bonded to the Bi atoms on the Bi3O4Br surface via carboxylates. After deprotonation of the carboxyl group, the bond lengths of the two CO bonds are close, falling between single and double bonds. This produces peaks located at 1640 cm⁻¹. -1 Asymmetric stretching vibration at 1380 cm and at 1380 cm -1 Symmetric stretching vibrations at the location. However, the Bi3O4Br surface contains coordinally unsaturated Bi... 3+ These are ions, which are Lewis acid sites. When Co-OCPP molecules recombine with Bi3O4Br, the carboxyl groups undergo proton transfer, generating surface carboxylate ions. 3+ Ion coordination forms Bi-O covalent bonds, significantly improving the stability of Co-OCPP@Bi3O4Br composite materials.

[0091] More importantly, the Bi-O covalent bond establishes a direct, low-resistance electron transport path between Co-OCPP and Bi3O4Br. This strong electron coupling facilitates the rapid transfer of photogenerated electrons from the valence band of Co-OCPP to the conduction band of Bi3O4Br, and also suppresses electron-hole recombination at the interface.

[0092] The powder X-ray diffraction patterns of the Co-OCPP, Bi3O4Br, and Co-OCPP@Bi3O4Br composite materials prepared in Example 2 are shown below. Figure 2 As shown, from Figure 2 It can be seen that Co-OCPP has a relatively broad diffraction peak between 20° and 30°, indicating that as a metal-organic molecular material, it mainly exists in an amorphous state. The spectrum of Bi3O4Br conforms to a typical Sillén layered structure. The XRD pattern of the Co-OCPP@Bi3O4Br composite material is basically consistent with the superposition results of the spectra of Co-OCPP and Bi3O4Br, proving that the composite material retains the layered structure of Bi3O4Br, and Co-OCPP is dispersed in an amorphous state on the surface of Bi3O4Br.

[0093] The Co-OCPP prepared in Example 2 has the following O 1s resolved X-ray photoelectron spectrum: Figure 3 As shown, from Figure 3 It can be seen that in the O 1s high-resolution XPS spectrum of Co-OCPP, the peaks at the binding energies of 531.4 eV and 532.7 eV are attributed to CO and C=O, respectively.

[0094] The high-resolution X-ray photoelectron spectrum of Co-OCPP@Bi3O4Br prepared in Example 2 is shown below. Figure 4 As shown, from Figure 4It can be seen that in the O 1s high-resolution XPS spectrum of Co-OCPP@Bi3O4Br, CO and C=O moved to the binding energy positions of 530.7 eV and 532.1 eV, respectively. This indicates that the oxygen atom of the carboxyl group coordinated with the Bi atom on the surface of Bi3O4Br, resulting in an increase in the electron cloud density on the oxygen atom.

[0095] The high-resolution X-ray photoelectron spectrum of Co-OCPP@Bi3O4Br prepared in Example 2 is shown below. Figure 5 As shown, from Figure 5 It can be seen that in the C 1s high-resolution XPS spectrum of Co-OCPP@Bi3O4Br, the CC peak at 284.8 eV is used as the standard for charge correction, and the peaks at the binding energy positions of 285.8 eV and 288.6 eV are attributed to CO / CN and C=O, respectively.

[0096] The N 1s high-resolution X-ray photoelectron spectrum of the Co-OCPP@Bi3O4Br prepared in Example 2 is shown below. Figure 6 As shown, from Figure 6 It can be seen that in the N 1s high-resolution XPS spectrum of Co-OCPP@Bi3O4Br, the peaks at the binding energies of 399.1 eV and 401.4 eV belong to NH and CN, respectively, indicating that the porphyrin compound in the composite material has a complete structure.

[0097] The high-resolution X-ray photoelectron spectrum of Co-OCPP@Bi3O4Br prepared in Example 2 is shown below. Figure 7 As shown, from Figure 7 It can be seen that in the high-resolution XPS spectrum of Co-OCPP@Bi3O4Br, the peaks at the binding energies of 780.2 eV and 795.5 eV belong to the Co 2p region, respectively. 3 / 2 and Co 2p 1 / 2 Furthermore, significant satellite peaks appeared at binding energies of 783.1 eV and 797.3 eV, respectively, indicating that the interfacial interaction between Co-OCPP and Bi3O4Br may mainly occur through the peripheral carboxyl groups.

[0098] The high-resolution X-ray photoelectron spectrum of Bi 4f of the Co-OCPP@Bi3O4Br prepared in Example 2 is shown below. Figure 8 As shown, from Figure 8 It can be seen that in the high-resolution XPS spectrum of Bi 4f in Co-OCPP@Bi3O4Br, the peaks at the binding energies of 158.8 eV and 164.2 eV belong to Bi 4f, respectively. 7 / 2 and Bi 4f 5 / 2 This proves that Bi is mainly composed of Bi 3+The valence state exists.

[0099] The scanning electron microscope observation results of the Co-OCPP prepared in Example 2 are as follows: Figure 9 As shown, from Figure 9 It can be seen that the metalloporphyrin Co-OCPP is a rod-shaped aggregate with a length of about 500 nm.

[0100] The scanning electron microscope observation results of the Bi3O4Br prepared in Example 2 are as follows: Figure 10 As shown, from Figure 10 It can be seen that Bi3O4Br is a relatively thin sheet-like accumulation with a diameter of about 200 nm.

[0101] The scanning electron microscope observation results of the Co-OCPP@Bi3O4Br prepared in Example 2 are as follows: Figure 11 As shown, from Figure 11 It can be seen that the Co-OCPP@Bi3O4Br composite material is formed by the attachment of Co-OCPP polymer on Bi3O4Br nanosheets. This proves that the Co-OCPP@Bi3O4Br composite material was successfully synthesized by the solution reflux method.

[0102] The transmission electron microscope observation results of Bi3O4Br prepared in Example 2 are as follows: Figure 12 As shown, from Figure 12 It can be seen that a single Bi3O4Br nanosheet is a regular square shape with a diameter of about 200 nm.

[0103] The Co-OCPP@Bi3O4Br composite material prepared in Example 2 was observed under a transmission electron microscope at 50 nm as follows: Figure 13 As shown, from Figure 13 It can be seen that the Co-OCPP@Bi3O4Br composite material clearly shows the composite of Co-OCPP amorphous polymer on the surface of Bi3O4Br crystals.

[0104] The Co-OCPP@Bi3O4Br composite material prepared in Example 2 was observed under a transmission electron microscope at 5 nm as follows: Figure 14 As shown, from Figure 14 It can be seen that the composite of Co-OCPP on the surface did not affect the layered structure of Bi3O4Br crystals, and its lattice fringes were clearly visible.

[0105] The elemental distribution of the Co-OCPP@Bi3O4Br composite material prepared in Example 2 is shown in the following figure. Figure 15 As shown, from Figure 15 It can be seen that the elements in the Co-OCPP@Bi3O4Br composite material are reasonably and uniformly distributed, further confirming the successful preparation of the composite material.

[0106] The UV-Vis diffuse reflectance spectra of the Co-OCPP, Bi3O4Br, and Co-OCPP@Bi3O4Br composite materials prepared in Example 2 are shown below. Figure 16 As shown, from Figure 16 It can be seen that Co-OCPP exhibits two strong absorption peaks at 380 nm and 520 nm, corresponding to its Soret band and Q band, respectively, which are typical characteristic absorption peaks of metalloporphyrins. The Q band position shows a blue shift compared to OMPP, further demonstrating the coordination field effect of the metal. Bi3O4Br exhibits a typical wide-bandgap inorganic semiconductor UV spectrum. More importantly, the absorption peaks of Co-OCPP@Bi3O4Br appear at 420 nm and 530 nm. That is, compared to pure Co-OCPP, both its Soret and Q bands show a significant red shift. This proves that there is a strong electronic interaction between Co-OCPP and Bi3O4Br, altering the electron cloud density of the metalloporphyrin.

[0107] The band gap diagrams of the Co-OCPP, Bi3O4Br, and Co-OCPP@Bi3O4Br composite materials prepared in Example 2 are shown below. Figure 17 , Figure 18 and Figure 19 As shown, from Figures 17-19 It can be seen that the band gaps of Co-OCPP, Bi3O4Br, and Co-OCPP@Bi3O4Br are 1.84 eV, 2.55 eV, and 2.05 eV, respectively. The band gap of the composite material Co-OCPP@Bi3O4Br is between that of the two single materials, which can combine the strong ultraviolet absorption of Bi3O4Br with the wide light absorption range of Co-OCPP, thereby improving the light absorption capacity.

[0108] The electrochemical impedance spectroscopy diagrams of the Co-OCPP, Bi3O4Br, and Co-OCPP@Bi3O4Br composite materials prepared in Example 2 are shown below. Figure 20 As shown, from Figure 20 It can be seen that Co-OCPP, as a metalloporphyrin organic molecule, has the highest impedance (approximately 320 Ω). Electrons can migrate rapidly along the layered structure of Bi3O4Br, therefore, the impedance of Bi3O4Br is relatively low (approximately 290 Ω). For the Co-OCPP@Bi3O4Br composite material, its electrochemical impedance is approximately 275 Ω.

[0109] The built-in electric field of the type II heterojunction provides a strong driving force for the directional separation and migration of electrons. Secondly, the carboxylic acid bonds formed between Co-OCPP and Bi3O4Br provide a good transfer channel for electrons. Therefore, the impedance of Co-OCPP@Bi3O4Br is slightly lower than that of Bi3O4Br.

[0110] The photocurrent response test results of the Co-OCPP, Bi3O4Br and Co-OCPP@Bi3O4Br composite materials prepared in Example 2 are as follows: Figure 21 As shown, from Figure 21 It can be seen that Co-OCPP@Bi3O4Br has the highest photocurrent value, which proves that it has the best photoresponse performance and the highest charge separation and transfer efficiency. Co-OCPP has the lowest photocurrent response value due to its larger charge transfer impedance.

[0111] The photoluminescence spectra of the Co-OCPP, Bi3O4Br, and Co-OCPP@Bi3O4Br composite materials prepared in Example 2 are shown in the figure below. Figure 22 As shown, from Figure 22 It can be seen that Bi3O4Br, as an indirect bandgap semiconductor, derives its strong fluorescence primarily from the luminescence of surface defect states. These surface defect states can act as charge recombination centers, causing photogenerated carriers to recombine rapidly on their surface, which is detrimental to photocatalytic reactions. Co-OCPP exhibits the lowest fluorescence, indicating that its excited-state energy is mainly consumed through non-radiative and metal-center electron transfer pathways. This result is largely consistent with the PL data of Co-OMPP, further demonstrating that carboxylation has minimal impact on the photoelectric properties of Co-OCPP. Compared to pure Bi3O4Br, the fluorescence of Co-OCPP@Bi3O4Br is significantly quenched, indicating that interfacial charge separation and transfer occur within the composite material, thereby suppressing the luminescence of surface defect states. Therefore, the Co-OCPP@Bi3O4Br composite material can improve the charge separation efficiency of Bi3O4Br, thus exhibiting better photocatalytic CO2 reduction kinetics.

[0112] The Mott-Schottky curve test results of the Co-OCPP, Bi3O4Br and Co-OCPP@Bi3O4Br composite materials prepared in Example 2 are as follows: Figures 23-25 As shown, from Figures 23-25 It can be seen that the LUMO value of Co-OCPP is -0.89 eV, which provides sufficient overpotential for the CO2 reduction reaction. The LUMO value of Bi3O4Br is -0.53 eV, which is exactly equivalent to the CO2 / CO reduction potential. Therefore, if pure Bi3O4Br is used for photocatalytic CO2 reduction to CO, it will easily compete with the hydrogen evolution reaction. The LUMO value of Co-OCPP@Bi3O4Br is -0.63 eV, which proves that the composite material Co-OCPP@Bi3O4Br forms a type II heterojunction, providing a large built-in electric field driving force for the directional migration of photogenerated electrons.

[0113] Example 3: 30 mg of photocatalyst and 50 mL of pure water were added to a quartz reactor. The material was uniformly dispersed by ultrasonication, and then the reactor was connected to a photocatalytic testing system. The magnetic stirrer at the bottom of the reactor was turned on, and the reactor was subjected to three vacuum-displacement gas 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, and the temperature of the reaction system was maintained at 5°C using a low-temperature constant-temperature water bath system. A gas chromatograph automatically took samples every 1 hour for analysis, calculating the yield of each major component in the photocatalytic reduction of CO2 at different reaction times. The yield was expressed in micromolar amounts per gram of catalyst.

[0114] Following the above catalytic experimental procedure, the photocatalysts used were Co-OMPP and Co-OCPP prepared in Example 2, respectively. The changes in the yield of the photocatalytic reduction product CO over time are shown below. Figure 26 As shown, from Figure 26 It can be seen that Co-OCPP exhibits improved photocatalytic CO production compared to Co-OMPP. This is because the introduction of carboxyl groups significantly enhances the dispersibility of Co-OCPP in the aqueous phase, and the carboxyl groups can more effectively enrich CO2 molecules through electrostatic interactions, increasing the local reactant concentration and thus improving the photocatalytic CO2 reduction reaction rate.

[0115] Following the catalytic experimental procedure described above, the photocatalysts were prepared using Co-OCPP, Bi3O4Br, and Co-OCPP@Bi3O4Br composite materials as described in Example 2. The changes in the yield of their photocatalytic reduction products over time are shown below. Figure 27 As shown, from Figure 27 It can be seen that Co-OCPP@Bi3O4Br exhibits the highest photocatalytic CO yield, approximately 3.84 µmol / g at 5 h, which is about 6.7 times and 2.7 times that of Co-OCPP (0.57 µmol / g) and Bi3O4Br (1.41 µmol / g), respectively. This demonstrates the significant improvement in the performance of the composite photocatalytic material due to the type II heterostructure.

[0116] Following the above catalytic experiment procedure, the photocatalyst, the Co-OCPP@Bi3O4Br composite material prepared in Example 2, was used in a photocatalyst recycling experiment. Each catalytic reaction lasted 5 hours. After the catalytic reaction, the photocatalyst was separated from the water, and the recovered photocatalyst was added back into the quartz reactor along with 50 mL of pure water. The photocatalyst recycling experiment was then conducted according to the above catalytic experiment procedure in Example 3. The cycle stability test results are shown in the figure below. Figure 28 As shown, from Figure 28It can be seen that Co-OCPP@Bi3O4Br has excellent cycle stability.

[0117] Following the above catalytic experiment procedure, the photocatalyst used was the Co-OCPP@Bi3O4Br composite material prepared in Example 2, and different blank control groups (no catalyst, no CO2, and no light) were set up. The experimental results of CO generation rate under different experimental conditions are shown in [the table below]. Figure 29 ,from Figure 29 It can be seen that multiple blank control experiments were conducted using Co-OCPP@Bi3O4Br as the photocatalyst under different experimental conditions (normal conditions, no catalyst, no CO2, and no light). The results show that CO was generated only under normal conditions, with a generation rate of 0.768 μmol / (g·h). The target product CO was not detected in any of the three blank control experiments. This experiment indicates that the source of CO in this experiment was solely the photocatalytic CO2 reduction reaction.

[0118] Example 4: The preparation method of the catalyst in Example 4 is the same as in Example 2, except that in "step 1), cobalt acetate tetrahydrate is replaced with ferrous acetate, and the molar ratio of ferrous acetate to OMPP is still 13:1". The other conditions remain unchanged, and finally a composite material of 5-(4-carboxyphenyl)-10,15,20-tris(4-methoxyphenyl)porphyrin iron(II) and Bi3O4Br is obtained, which is labeled as Fe-OCPP@Bi3O4Br.

[0119] Example 5: The preparation method of the catalyst in Example 5 is the same as that in Example 2, except that in "step 1), cobalt acetate tetrahydrate is replaced with copper acetate monohydrate, and the molar ratio of copper acetate monohydrate to OMPP is still 13:1". The other conditions remain unchanged, and finally a composite material of 5-(4-carboxyphenyl)-10,15,20-tris(4-methoxyphenyl)porphyrin copper(II) and Bi3O4Br is obtained, which is labeled as Cu-OCPP@Bi3O4Br.

[0120] Example 6: The preparation method of the catalyst in Example 6 is the same as that in Example 2, except that "step 2 is omitted" and the carboxyl functionalization step is not performed. In step 4), Co-OMPP is directly compounded with Bi3O4Br, and the amount of Co-OMPP is 0.03g. The other conditions remain unchanged, and finally a composite material of 5-(4-methoxycarbonylphenyl)-10,15,20-tris(4-methoxyphenyl)porphyrin cobalt(II) and Bi3O4Br is obtained, which is labeled as Co-OMPP@Bi3O4Br.

[0121] Example 7: Following the catalytic experiment procedure of Example 3, the photocatalysts used were Co-OCPP@Bi3O4Br and Bi3O4Br prepared in Example 2, Fe-OCPP@Bi3O4Br prepared in Example 4, Cu-OCPP@Bi3O4Br prepared in Example 5, and Co-OMPP@Bi3O4Br prepared in Example 6. The changes in the yield of the photocatalytic reduction product CO over time are shown below. Figure 30 As shown, from Figure 30 It can be seen that:

[0122] (1) The composites of three metal porphyrins (Co-OCPP, Fe-OCPP, Cu-OCPP) with Bi3O4Br significantly improved the photocatalytic reduction of CO2 to CO yield. Among them, Co-OCPP@Bi3O4Br performed best, Fe-OCPP@Bi3O4Br was second best, and Cu-OCPP@Bi3O4Br was the worst.

[0123] (2) The composite of Co-OMPP without carboxyl functionalization and Bi3O4Br showed a significantly insufficient increase in the photocatalytic reduction of CO2 to CO, and was closer to the catalytic efficiency of Bi3O4Br alone. This shows the importance of carboxyl functionalization in step 2) of Example 2 for the successful composite of materials.

[0124] 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. An A3B type cobalt metal porphyrin-bismuth halide composite material, characterized in that, The composite material is a heterojunction structure composed of A3B type cobalt metal porphyrin and bismuth oxyhalide, wherein the bismuth oxyhalide is Bi3O4Br and the A3B type cobalt metal porphyrin is 5-(4-carboxyphenyl)-10,15,20-tris(4-methoxyphenyl)porphyrin cobalt(II), which is labeled as Co-OCPP.

2. The A3B type cobalt metal porphyrin-bismuth halide composite material as described in claim 1, characterized in that, The A3B type cobalt metal porphyrin was prepared according to the following method: Step 1: Synthesize 5-(4-methoxycarbonylphenyl)-10,15,20-tris(4-methoxyphenyl)-21H,23H-porphyrin, labeled as OMPP, with the following structural formula: ； Step 2: OMPP reacts with divalent Co salt to synthesize 5-(4-methoxycarbonylphenyl)-10,15,20-tris(4-methoxyphenyl)porphyrin cobalt(II), labeled as Co-OMPP, with the following structural formula: ； Step 3: After alkaline hydrolysis of the methoxycarbonyl group on the benzene ring of Co-OMPP, acidification was performed to synthesize 5-(4-carboxyphenyl)-10,15,20-tris(4-methoxyphenyl)porphyrin cobalt(II), which was labeled as Co-OCPP, and its structural formula is as follows: 。 3. The A3B type cobalt metal porphyrin-bismuth halide composite material as described in claim 2, characterized in that, In step 1, the preparation method of OMPP includes the following steps: S1: Methyl p-aldehyde benzoate, p-methoxybenzaldehyde and pyrrole are dissolved in solvent A, and nitrogen gas is introduced to completely remove oxygen from the system; S2: Add boron trifluoride diethyl ether complex as Lewis acid catalyst to the reaction solution of step S1, and stir the reaction at room temperature and under nitrogen atmosphere for 0.5~1.5 h to promote the condensation reaction of pyrrole units; S3: Add a solution of 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) dropwise to the reaction system of step S2. After the addition is complete, continue stirring at room temperature for 2-3 h to oxidize and aromatize the porphyrin precursor to obtain the crude product. S4: The solvent was removed by rotary evaporation to obtain a dark solid residue. The solid was dissolved in dichloromethane and purified by silica gel column chromatography to obtain OMPP.

4. The A3B type cobalt metal porphyrin-bismuth halide composite material as described in claim 3, characterized in that, The molar ratio of p-methoxybenzaldehyde to methyl p-aldehyde benzoate is 2-4:1, the molar ratio of pyrrole to methyl p-aldehyde benzoate is 3-5:1, and solvent A is chloroform, toluene, or dichloromethane. The molar amount of the boron trifluoride diethyl ether complex in step S2 is 30-50% of the molar amount of methyl benzoate in step S1; The molar amount of DDQ in step S3 is 6-8 times the molar amount of methyl benzoate in step S1; The eluent for column chromatography in step S4 is a mixture of petroleum ether and dichloromethane with a volume ratio of 1 to 1.5:

1.

5. The A3B type cobalt metal porphyrin-bismuth halide composite material as described in claim 2, characterized in that, Step 2, the preparation of Co-OMPP specifically includes the following steps: M1: Under nitrogen protection, OMPP is dissolved in DMF, followed by the addition of divalent Co salt, and the mixture is heated to 150~170℃ and reacted for 12~16h; M2: After the reaction is complete, the mixture is cooled and rotary evaporated. The residue from the rotary evaporation is dissolved in dichloromethane and washed with distilled water to separate the organic phase. The organic phase is dried with anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure to obtain the crude product. The crude product is then purified by silica gel column chromatography to obtain Co-OMPP.

6. The A3B type cobalt metal porphyrin-bismuth halide composite material as described in claim 5, characterized in that, In step M1, the molar amount of divalent Co salt is 10-15 times the molar amount of OMPP; in step M2, the eluent for column chromatography is dichloromethane.

7. The preparation method of the A3B type cobalt metal porphyrin-bismuth halide composite material as described in claim 1, characterized in that, Includes the following steps: Step 1: Disperse Co-OCPP and Bi3O4Br in ethanol; Step 2: React the mixture at 80~90℃ for 5~8 hours; Step 3: After the system cools naturally to room temperature, collect the solid product by centrifugation, wash and dry it to complete the preparation.

8. The preparation method of the A3B type cobalt metal porphyrin-bismuth halide composite material as described in claim 7, characterized in that... The mass ratio of Co-OCPP to bismuth oxyhalide is 0.01~0.03:

1.

9. The application of the A3B type cobalt metal porphyrin-bismuth halide composite material as described in claim 1 in the photocatalytic reduction of CO2 reaction.

10. The application as described in claim 9, characterized in that... Using the A3B type cobalt metal porphyrin-halobismuth composite material as a photocatalyst, the photocatalyst was dispersed in pure water at a concentration of 0.1~1g / L. The mixture was transferred to a quartz reactor, and the reactor was evacuated and gas-displaced using high-purity CO2 to remove air from the reaction system. Then, CO2 at a pressure of 20~200kPa was introduced into the reactor. After the system was balanced, a 100~500W xenon lamp was used as the reaction light source for illumination. The temperature of the reaction system was maintained at 2~10℃ using a low-temperature constant-temperature water bath system to carry out the photocatalytic CO2 reduction reaction.

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