Preparation method and application of sulfonated photocatalyst

Abstract

The invention provides a preparation method and application of a sulfonated photocatalyst, and belongs to the technical field of photocatalyst materials.The preparation method comprises the steps that 2, 5-dibromopyrimidine and trimethylsilylacetylene react in anhydrous triethylamine and tetrahydrofuran, and then extraction and purification are conducted to obtain a first intermediate; dissolving the first intermediate in tetrahydrofuran, dropwise adding tetra-n-butylammonium fluoride at-40 DEG C or below, hydrolyzing, extracting and purifying to obtain a second intermediate; the second intermediate and 5, 10, 15, 20-tetra (4-bromophenyl) porphyrin are dissolved in N, N-dimethylformamide and diisopropylamine, and then a Sonogashira coupling reaction is carried out under the catalytic action; after the coupling reaction is completed, filtering, extracting and drying in vacuum to obtain an initial polymer; the preparation method of the sulfonated photocatalyst, provided by the invention, is simple, efficient and environment-friendly, and the prepared sulfonated photocatalyst has excellent hydrophilicity and high oxygen adsorption capacity at the same time, and can be used for efficiently producing H2O2.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalyst materials, and particularly to a preparation method and application of a sulfonated photocatalyst. Background Art

[0002] The research on synthesizing hydrogen peroxide (H2O2) using photocatalytic technology has gradually become one of the hotspots in the current catalytic field. In this method, during the operation process, no additional chemical reagents or energy input are required. Only relying on renewable light energy as the driving force, using water and oxygen in the air as raw materials, H2O2 is efficiently generated through photocatalytic reactions, demonstrating the advantages of being green and environmentally friendly. In addition, the reaction conditions of this method are mild and can usually be carried out at room temperature and atmospheric pressure, greatly reducing energy consumption and safety risks, and is expected to replace the traditional energy-intensive and pollution-emitting hydrogen peroxide production process. This sustainable synthesis path not only meets the requirements of the green development of modern chemical industry but also shows broad application prospects in the fields of environmental governance, energy conversion, and efficient oxidation reactions. Therefore, in-depth research on the mechanism of photocatalytic synthesis of H2O2, optimization of the design of catalytic materials, and improvement of reaction efficiency have important scientific significance and practical value for promoting the practical application of this technology.

[0003] Although the photocatalytic synthesis of H2O2 technology shows great potential, its practical application still faces many challenges. Among them, the high recombination rate of photo-generated carriers is one of the key factors limiting the efficiency of photocatalytic reactions. During the photocatalytic reaction process, the rapid recombination of photo-generated electrons and holes will significantly reduce the number of active electrons available for reducing oxygen to generate H2O2, thereby inhibiting the catalytic efficiency. In addition to the limitation of the carrier recombination rate, the material properties of the photocatalyst also have an important impact on the catalytic effect. Among them, the adsorption ability of the photocatalyst to oxygen directly determines the activation degree of oxygen on the catalyst surface during the reaction process, which is a prerequisite for generating H2O2. At the same time, the hydrophilicity of the catalyst is also a factor that cannot be ignored. Good hydrophilicity helps the uniform distribution of water molecules on the catalyst surface and promotes the reaction synergy between oxygen and water, increasing the generation rate of H2O2.

[0004] Therefore, it is crucial to develop a photocatalyst that simultaneously has excellent hydrophilicity and high oxygen adsorption ability. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a simple, efficient, and environmentally friendly preparation method of a sulfonated photocatalyst. The prepared sulfonated photocatalyst simultaneously has excellent hydrophilicity and high oxygen adsorption ability and can be used for the efficient production of H2O2.

[0006] To solve the above technical problem, the present invention provides a preparation method of a sulfonated photocatalyst, including the following steps: 2,5-dibromopyrimidine reacts with trimethylsilylacetylene in anhydrous triethylamine and tetrahydrofuran, and then is extracted and purified to obtain a first intermediate; The first intermediate is dissolved in tetrahydrofuran, and tetrabutylammonium fluoride is added dropwise below -40 °C for hydrolysis, and then is extracted and purified to obtain a second intermediate; The second intermediate and 5,10,15,20-tetra(4-bromophenyl)porphyrin are dissolved in N,N-dimethylformamide and diisopropylamine, and then undergo a Sonogashira coupling reaction under catalysis; After the coupling reaction is completed, it is filtered, extracted and vacuum dried to obtain an initial polymer; The initial polymer is sulfonated and modified, and then filtered, extracted and vacuum dried to obtain a sulfonated photocatalyst.

[0007] Further, the extractant used for extraction is dichloromethane and deionized water.

[0008] Further, the purification is column chromatography purification, and the eluent used for column chromatography is a mixture of dichloromethane and petroleum ether with a volume ratio of 3:1 - 5:1.

[0009] Further, the molar ratio of the reaction of 5,10,15,20-tetra(4-bromophenyl)porphyrin to the second intermediate is 1:1 - 1:3.

[0010] Further, the reaction temperature of the coupling reaction is 100 - 120 °C, and the reaction time is 2 - 6 days.

[0011] Further, the sulfonation modification of the initial polymer includes the following steps: The initial polymer is dispersed in dichloromethane under a protective atmosphere to obtain an initial polymer dispersion; Chlorosulfonic acid is added dropwise to the initial polymer dispersion under a protective atmosphere and mixed in an ice bath to obtain a mixture; The mixture is stirred for a sulfonation modification reaction.

[0012] Further, the reaction temperature of the sulfonation modification reaction of the mixture is 20 - 30 °C, and the reaction time is 2 - 6 days.

[0013] Further, the extraction is carried out by Soxhlet extraction, and the Soxhlet extractant is methanol, dichloromethane or tetrahydrofuran.

[0014] Further, the drying temperature of the vacuum drying is 50 - 120 °C, and the drying time is 20 - 40 h.

[0015] The present invention also provides an application of the sulfonated photocatalyst for producing H2O2 from air and water, including the following steps: The sulfonated photocatalyst is dispersed in ultrapure water to obtain a mixture; Transfer the mixture into a reactor and irradiate it with xenon lamp light; Measure the production amount of the generated H2O2.

[0016] A preparation method of a sulfonated photocatalyst provided by the present invention uses 5,10,15,20-tetrakis(4-bromophenyl)porphyrin as a photosensitive unit and 2,5-dibromopyrimidine as an electron donor. After constructing a conjugated skeleton through the Sonogashira coupling reaction, it is then sulfonated and modified to obtain a sulfonated photocatalyst with broad-spectrum response characteristics. Not only is the process simple, the process conditions mild, the operation simple, the whole process simple and efficient, and it is easy to implement on a large scale, but also raw materials that can pollute the environment and affect human health are not used during the process, and the process is environmentally friendly, realizing a green synthesis route for the photocatalyst.

[0017] Moreover, in the preparation method of a sulfonated photocatalyst provided by the present invention, chlorosulfonic acid is introduced into the conjugated microporous polymer constructed by the Sonogashira coupling reaction for sulfonation modification to obtain a sulfonated photocatalyst with broad-spectrum response characteristics. Since the sulfonic acid group (-SO3H) in the obtained sulfonated photocatalyst has strong polarity, while oxygen molecules are weakly polar and have a certain quadrupole moment, when they come into contact with polar groups, they can be effectively adsorbed. Therefore, the sulfonated photocatalyst prepared by the present invention can form a strong physical adsorption with oxygen molecules (O2).

[0018] Therefore, the sulfonated photocatalyst prepared by the present invention not only has excellent hydrophilicity, but also has high oxygen adsorption capacity, can increase the enrichment degree of oxygen on the material surface, and further can improve the ability of the photocatalyst to produce H2O2 in H2O.

[0019] Applying the sulfonated photocatalyst prepared by the present invention to the synthesis of hydrogen peroxide from water and air can efficiently utilize oxygen in water and air to directly synthesize hydrogen peroxide under normal temperature and pressure, realizing the efficient production of H2O2, and the yield of H2O2 can be as high as 2.59 mmol g -1 h -1 。 Description of the Drawings

[0020] Figure 1 It is a flow chart of a preparation method of a sulfonated photocatalyst provided by an embodiment of the present invention; Figure 2(a) is the solid 13 C NMR diagram of BMO prepared in Example 1 and BMS prepared in Example 2 of the present invention; Figure 2(b) is the FT-IR spectrum diagram of BMO prepared in Example 1 and BMS prepared in Example 2 of the present invention; Figure 2(c) is the XPS survey spectrum diagram of BMO prepared in Example 1 and BMS prepared in Example 2 of the present invention; Figure 2(d) shows the O 1s XPS and S 2p XPS spectra of BMO prepared in Example 1 of the present invention and BMS prepared in Example 2; Figure 3(a) shows the UV-visible DRS spectra of BMO prepared in Example 1 of the present invention and BMS prepared in Example 2 (the inset is a Tauc plot); Figure 3(b) shows the Mott-Schottky plot of BMO prepared in Example 1 of the present invention and BMS prepared in Example 2 (Mott-Schottky plot); Figure 3(c) shows the energy band structure diagram of the photocatalyst of BMO prepared in Example 1 of the present invention and BMS prepared in Example 2; Figure 3(d) shows the photocurrent response diagram of BMO prepared in Example 1 of the present invention and BMS prepared in Example 2; Figure 3(e) shows the electrochemical impedance diagram of BMO prepared in Example 1 of the present invention and BMS prepared in Example 2; Figure 3(f) shows the Koutecky-Levich plot of BMO prepared in Example 1 of the present invention and BMS prepared in Example 2 (Koutecky-Levich plot); Figure 4(a) shows a comparison diagram of the photocatalytic H2O2 production amounts of BMO prepared in Example 1 of the present invention and BMS prepared in Example 2 under different atmospheres; Figure 4(b) shows the stability performance test diagram of BMS prepared in Example 2 as a photocatalyst. Detailed implementation manners

[0021] A preparation method of a sulfonated photocatalyst provided by an embodiment of the present invention uses 5,10,15,20-tetra(4-bromophenyl)porphyrin as a photosensitive unit and 2,5-dibromopyrimidine as an electron donor. After constructing a conjugated skeleton through a Sonogashira coupling reaction, a sulfonated photocatalyst with broad spectral response characteristics is obtained through sulfonation modification.

[0022] See Figure 1 A preparation method of a sulfonated photocatalyst provided by an embodiment of the present invention specifically includes the following steps: Step 1) 2,5-Dibromopyrimidine reacts with trimethylsilylacetylene in anhydrous triethylamine and tetrahydrofuran, and then is extracted and purified to obtain a first intermediate.

[0023] Specifically, to promote the reaction, during the actual reaction process, 2,5-dibromopyrimidine and trimethylsilylacetylene are placed in a reaction vessel, and then anhydrous triethylamine and tetrahydrofuran are added to the reaction vessel. After introducing nitrogen gas into the resulting mixture for a period of time, copper(I) iodide, triphenylphosphine, and bis(triphenylphosphine)palladium(II) dichloride are successively added to the mixture. After continuing to introduce nitrogen gas for a period of time, the mixture is heated under reflux for reaction. Meanwhile, to more clearly understand the reaction situation, the reaction is monitored by thin-layer chromatography (TLC). After the reaction is completed, the mixture is cooled to room temperature and then poured into water for extraction and purification to obtain the first intermediate.

[0024] Among them, copper(I) iodide acts as a co-catalyst, activating the C≡C bond of trimethylsilylacetylene by forming a copper-alkyne complex to promote the coupling reaction between trimethylsilylacetylene and 2,5-dibromopyrimidine; triphenylphosphine acts as a ligand to stabilize the active center of the palladium catalyst, preventing the aggregation and inactivation of palladium species, and at the same time adjusting the electronic environment of palladium to optimize the catalytic efficiency; bis(triphenylphosphine)palladium(II) dichloride acts as a palladium catalyst precursor, catalyzing the Sonogashira coupling reaction between 2,5-dibromopyrimidine and trimethylsilylacetylene through oxidative addition (activation of the C-Br bond), transmetalation (interaction with the copper-alkyne intermediate), and reductive elimination steps.

[0025] Among them, the structural formula of the first intermediate obtained by reacting 2,5-dibromopyrimidine with trimethylsilylacetylene and then performing extraction and purification in anhydrous triethylamine and tetrahydrofuran is as follows:

[0026] The reaction equation of the reaction occurring in this process is as follows:

[0027] Among them, the extraction solvent used for extraction after the reaction is dichloromethane and deionized water.

[0028] Among them, the purification is column chromatography purification, and the eluent used for the column chromatography is a mixture of dichloromethane and petroleum ether with a volume ratio of 3:1 - 5:1.

[0029] As an optimal implementation mode of the present invention, the volume ratio of the dichloromethane and petroleum ether mixture in the eluent used for the column chromatography is 3:1.

[0030] Step 2) The first intermediate is dissolved in tetrahydrofuran, and tetrabutylammonium fluoride is added dropwise at a temperature below -40 °C for hydrolysis, and then extraction and purification are performed to obtain the second intermediate.

[0031] Specifically, during the reaction process, the first intermediate is placed in a reaction vessel, and tetrahydrofuran is added to the reaction vessel to dissolve the first intermediate in tetrahydrofuran under a nitrogen atmosphere to obtain a mixed solution. Then, tetrabutylammonium fluoride (abbreviated as TBAF) is slowly added dropwise to the mixed solution at a low temperature below -40 °C to cause a hydrolysis reaction, and the reaction progress is monitored by TLC during the reaction. After the reaction is completed, the mixture obtained from the reaction is cooled to room temperature and poured into water for extraction and purification to obtain the second intermediate, and the obtained second intermediate is 2,5-diethynylpyrimidine.

[0032] This reaction process is a process of selectively removing the trimethylsilyl group, i.e., –Si(CH3)3, in the first intermediate from the acetylene end (–C≡C–SiMe3) through a hydrolysis reaction to generate a terminal alkyne (–C≡C–H). The obtained second intermediate, i.e., the structural formula of 2,5-diethynylpyrimidine, is as follows:

[0033] The reaction formula of the reaction occurring in this process is as follows:

[0034] Among them, the extraction solvent used for extraction after the hydrolysis reaction is dichloromethane and deionized water.

[0035] Among them, the purification after extraction is carried out by column chromatography purification, and the eluent used for column chromatography is a mixture of dichloromethane and petroleum ether with a volume ratio of 3:1 - 5:1.

[0036] As an optimal implementation mode of the present invention, the volume ratio of dichloromethane to petroleum ether in the eluent used for column chromatography is 5:1.

[0037] Step 3) The second intermediate and 5,10,15,20-tetrakis(4-bromophenyl)porphyrin are dissolved in N,N-dimethylformamide and diisopropylamine and then undergo a Sonogashira coupling reaction under catalysis. After the coupling reaction is completed, filtration, extraction, and vacuum drying are carried out to obtain the initial polymer.

[0038] Specifically, 5,10,15,20-tetrakis(4-bromophenyl)porphyrin and the second intermediate (i.e., 2,5-diethynylpyrimidine) are placed in a reaction vessel, and N,N-dimethylformamide and diisopropylamine are added to the reaction vessel under a nitrogen atmosphere to completely dissolve 5,10,15,20-tetrakis(4-bromophenyl)porphyrin and the second intermediate to obtain a mixed solution. After blowing nitrogen into the mixed solution for a period of time, copper iodide and tetrakis(triphenylphosphine)palladium are added to the mixed solution, and the mixture is heated to reflux under a nitrogen atmosphere. After the reaction is completed, the mixture is cooled to room temperature, and filtration, extraction, and vacuum drying are carried out to obtain the initial polymer (denoted as BMO).

[0039] Among them, the core role of cuprous iodide (CuI) is to significantly reduce the activation energy barrier of the C≡C bond in the second intermediate (i.e., 2,5-diethynylpyrimidine) by forming a highly active copper(I)-ethynyl complex (Cu-C≡C-pyrimidine).

[0040] Among them, the core role of tetrakis(triphenylphosphine)palladium (Pd(PPh3)4) is to act as a Pd(0) source, first undergo oxidative addition with 5,10,15,20-tetrakis(4-bromophenyl)porphyrin to generate the key intermediate Pd(II)-aryl bromide.

[0041] Among them, the molar ratio of 5,10,15,20-tetrakis(4-bromophenyl)porphyrin to the second intermediate (i.e., 2,5-diethynylpyrimidine) in the reaction is 1:1 - 1:3.

[0042] As an optimal implementation mode of the present invention, the molar ratio of 5,10,15,20-tetrakis(4-bromophenyl)porphyrin to the second intermediate (i.e., 2,5-diethynylpyrimidine) in the reaction is 1:2.

[0043] Among them, the reaction temperature of the Sonogashira coupling reaction is 100 - 120 °C, and the reaction time is 2 - 6 days.

[0044] As an optimal implementation mode of the present invention, the reaction temperature of the Sonogashira coupling reaction is 110 °C, and the reaction time is 3 days.

[0045] Among them, extraction is carried out by Soxhlet extraction, and the extraction agent is methanol, dichloromethane or tetrahydrofuran.

[0046] Among them, the drying temperature of vacuum drying is 50 - 120 °C, and the drying time is 20 - 40 h.

[0047] As an optimal implementation mode of the present invention, the drying temperature of vacuum drying is 60 °C, and the drying time is 24 h.

[0048] Among them, the structural formula of the obtained initial polymer (denoted as BMO) is as follows:

[0049] The reaction formula of the reaction occurring in this process is as follows:

[0050] Step 4) The initial polymer is sulfonated and modified, then filtered, extracted and vacuum dried to obtain the sulfonated photocatalyst.

[0051] Among them, the sulfonation modification of the initial polymer includes the following steps: a. Disperse the initial polymer in dichloromethane under a protective atmosphere to obtain an initial polymer dispersion system; b Under a protective atmosphere, chlorosulfonic acid was added dropwise to the initial polymer dispersion system and mixed in an ice bath to obtain a mixture; c The mixture was stirred to carry out the sulfonation modification reaction.

[0052] Specifically, first place the initial polymer in a reaction vessel. Under nitrogen protection, add dichloromethane to the reaction vessel to uniformly disperse the initial polymer in dichloromethane to obtain a mixed solution. Among them, dichloromethane, as an organic solvent, can uniformly disperse the initial polymer (i.e., BMO), provide a reaction medium for the subsequent sulfonation modification reaction of the initial polymer, and ensure that the subsequent dropwise addition and reaction of chlorosulfonic acid can be carried out in a homogeneous system.

[0053] Then, under nitrogen protection and in an ice bath condition, chlorosulfonic acid was slowly added dropwise to the mixed solution to obtain a mixture. Then the mixture was stirred to carry out the sulfonation modification reaction. Finally, filtration, extraction, and vacuum drying were carried out to obtain the sulfonated photocatalyst (denoted as BMS).

[0054] Among them, the temperature of the sulfonation modification reaction of the mixture is 20 - 30 °C, and the reaction time is 2 - 6 days.

[0055] As an optimal implementation mode of the present invention, the temperature of the sulfonation modification reaction of the mixture is at room temperature, and the reaction time is 3 days.

[0056] Among them, extraction is carried out by Soxhlet extraction, and the extraction agent is methanol, dichloromethane, or tetrahydrofuran.

[0057] Among them, the drying temperature of vacuum drying is 50 - 120 °C, and the drying time is 20 - 40 h.

[0058] As an optimal implementation mode of the present invention, the drying temperature of vacuum drying is 60 °C, and the drying time is 24 h.

[0059] Among them, the structural formula of the obtained sulfonated photocatalyst (denoted as BMS) is as follows:

[0060] The reaction formula of the reaction occurring in this process is as follows:

[0061] A preparation method of a sulfonated photocatalyst provided by the present invention uses 5,10,15,20-tetra(4-bromophenyl)porphyrin as a photosensitive unit and 2,5-dibromopyrimidine as an electron donor. After constructing a conjugated framework through the Sonogashira coupling reaction, it is then sulfonated and modified to obtain a sulfonated photocatalyst with broad-spectrum response characteristics. The process is not only simple, with mild process conditions and easy operation, the whole process is simple and efficient, and is easy to implement on a large scale. Moreover, no raw materials that can pollute the environment and affect human health are used in the process, and the process is environmentally friendly, realizing a green synthesis route for the photocatalyst.

[0062] Since the sulfonated photocatalyst of the present invention is prepared by introducing chlorosulfonic acid for sulfonation modification in the conjugated microporous polymer constructed by the Sonogashira coupling reaction, the sulfonic acid group (-SO3H) in the prepared sulfonated photocatalyst has strong polarity, while oxygen molecules are weakly polar molecules with a certain quadrupole moment. When they come into contact with the polar sulfonic acid group, they can be effectively adsorbed. Therefore, the sulfonated photocatalyst prepared by the present invention can form a strong physical adsorption with oxygen molecules (O2).

[0063] Therefore, the sulfonated photocatalyst prepared by the present invention not only has excellent hydrophilicity but also has high oxygen adsorption capacity, which can increase the enrichment degree of oxygen on the material surface, and thus can improve the ability of the photocatalyst to produce H2O2 in H2O.

[0064] Applying the sulfonated photocatalyst prepared by the present invention to the synthesis of hydrogen peroxide from water and air can directly synthesize hydrogen peroxide from water and oxygen in the air efficiently at normal temperature and pressure, realizing the high-efficiency production of H2O2, and the yield of H2O2 can be as high as 2.59 mmol g -1 h -1 。

[0065] Specifically, when using the sulfonated photocatalyst prepared by the present invention to synthesize hydrogen peroxide from water and air, the sulfonated photocatalyst can be added to ultrapure water, ultrasonically dispersed to make it uniformly mixed, and the mixture is transferred to a specific reactor.

[0066] Then, it is irradiated with a 300 W xenon lamp (600 mW / cm 2 ). After a certain period of time, the reaction solution is taken, filtered through a hydrophilic PET membrane filter, and the amount of H2O2 produced can be measured with a potassium titanate oxalate solution.

[0067] Since the sulfonated photocatalyst prepared by the present invention has both excellent hydrophilicity and high oxygen adsorption capacity, at normal temperature and pressure, the sulfonated photocatalyst prepared by the present invention can directly and efficiently synthesize hydrogen peroxide from water and oxygen in the air, and the yield of H2O2 can be as high as 2.59 mmol g -1 h -1, the efficient production of H2O2 is achieved.

[0068] The following is a specific description of a preparation method and application of a sulfonated photocatalyst provided by the present invention through examples. However, these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. The preparation schemes in the examples are only preferred schemes, and the present invention is not limited to the examples.

[0069] Example 1 Step 1: Place 2,5-dibromopyrimidine (6.25 g, 28.07 mmol) and trimethylethynylsilane (22.68 g, 230.4 mmol) in a 250 mL Schlenk flask. Then add tetrahydrofuran (90 mL) and anhydrous triethylamine (50 mL) to the Schlenk flask, purge with nitrogen for 15 min, and then successively add copper(I) iodide (1.086 g, 5.7 mmol), triphenylphosphine (1.02 g, 3.8 mmol), and bis(triphenylphosphine)palladium(II) dichloride (1.2 g, 1.7 mmol). Purge with nitrogen for another 15 min, and then heat the mixture to 50 °C and reflux for 24 h. Monitor the reaction by thin-layer chromatography (TLC). After the reaction is completed, cool the mixture to room temperature, pour it into water, extract with dichloromethane, and then purify by column chromatography to obtain 4 g of intermediate 1 with a yield of 52.3%.

[0070] Step 2: Place intermediate 1 (3.8 g, 13.9 mmol) in a 250 mL Schlenk flask, and add 50 mL of tetrahydrofuran to the Schlenk flask to dissolve intermediate 1 in tetrahydrofuran under a nitrogen atmosphere. Then slowly add tetrabutylammonium fluoride (TBAF) at a low temperature below -40 °C, and monitor the reaction by thin-layer chromatography (TLC). After the reaction is completed, cool the mixture to room temperature, pour it into water, and extract with dichloromethane. Then purify by column chromatography to obtain 1.3 g of intermediate 2, namely 2,5-diethynylpyrimidine, with a yield of 73%.

[0071] Step 3: Place 5,10,15,20-tetrakis(4-bromophenyl)porphyrin (2.78 g, 3 mmol) and Intermediate 2 (i.e., 2,5-diethynylpyrimidine) (762 mg, 6 mmoL) in a 500 mL Schlenk flask. Under a nitrogen atmosphere, add N,N-dimethylformamide (200 mL) and diisopropylamine (100 mL) to the Schlenk flask to dissolve all of 5,10,15,20-tetrakis(4-bromophenyl)porphyrin and Intermediate 2. After purging with nitrogen for 10 min, add copper(I) iodide (114.2 mg, 0.6 mmol) and tetrakis(triphenylphosphine)palladium(0) (277 mg, 0.24 mmol), and under a nitrogen atmosphere, heat the mixture to reflux for 3 days. After the reaction is completed, cool the mixture to room temperature, filter to obtain a solid, and extract it multiple times with tetrahydrofuran, methanol, and dichloromethane. Place the obtained solid in a vacuum drying oven at 60 °C and dry it overnight to obtain 2.3 g of a purple-black initial polymer solid with a yield of 65%. Denote this initial polymer as BMO.

[0072] Example 2 Based on the initial polymer BMO prepared in Example 1, further prepare a sulfonated photocatalyst.

[0073] Place the initial polymer BMO (600 mg, 0.186 mmol) prepared in Example 1 in a 100 mL Schlenk flask. Under nitrogen protection, add dichloromethane to the flask to disperse the initial polymer evenly in dichloromethane. Then, under nitrogen protection, slowly add chlorosulfonic acid (12 mL) dropwise under an ice bath condition to obtain a mixture. Stir the mixture at room temperature for 48 h. Finally, filter and collect the residue, and extract the filter cake three times with deionized water and methanol respectively. After drying in a vacuum at 60 o °C for 24 h, 640 mg of a sulfonated photocatalyst is obtained. Denote this sulfonated photocatalyst as BMS.

[0074] Example 3: Structural Characterization of the Photocatalyst Refer to Figures 2(a) - 2(d). Characterize the chemical structures of BMO prepared in Example 1 of the present invention and BMS prepared in Example 2 of the present invention by solid carbon spectrum ( 13 C ss-NMR), Fourier transform infrared spectrum (FT-IR), and X-ray photoelectron spectroscopy (XPS) respectively. In fact, the main difference in the structures between BMO prepared in Example 1 of the present invention and BMS prepared in Example 2 is that: BMS prepared in Example 2 introduces chlorosulfonic acid onto BMO prepared in Example 1, which can be proven in 13 C ss-NMR, FT-IR, and XPS spectra.

[0075] The resonance peaks generated between δ = 109 ppm and δ = 120 - 142 ppm are attributed to the carbon atoms in the pyrrole of the porphyrin unit and the benzene ring. The peak at δ = 155 ppm is attributed to the pyrimidine carbon respectively. The vibration peak of -C≡C- can be observed at δ = 95 ppm, indicating the successful construction of BMO. In the FT-IR spectrum, the stretching vibration of N-H in the porphyrin group is around 3000 cm -1 or so, and the peak at 1640 cm -1 is related to the stretching vibration of -C=C-. The peak shown at 2362 cm -1 is for the alkyne bond (-C≡C-), confirming that polymerization has occurred. The stretching vibration peaks of O=S=O can be observed at 1115 and 1011 cm -1 , indicating the successful incorporation of the sulfonic acid group, that is, the successful construction of BMS.

[0076] Moreover, the XPS spectra of BMS prepared in Example 2 and BMO prepared in Example 1 of the present invention were recorded to study the chemical element composition and state of the two polymers BMS and BMO. The XPS spectrum of BMS shows an obvious additional peak corresponding to the presence of sulfur element. In the high-resolution XPS spectrum of S2p, two peaks centered at 168 eV and 167 eV were observed, which were assigned to S 2p1 / 2 and S 2p3 / 2 respectively, and can be attributed to the O=S=O bond. This confirms the presence of the sulfonate group, indicating that chlorosulfonic acid has been successfully incorporated into the structure of the polymer BMS.

[0077] Example 4: Photoelectrochemical Experiment of Photocatalyst Referring to Figures 3(a) - 3(f), in order to determine the photocarrier separation efficiency and the interfacial charge transfer ability of the catalyst, the transient photocurrent response (CA) and the electrochemical impedance spectrum (EIS) of BMO prepared in Example 1 and BMS prepared in Example 2 of the present invention under illumination were recorded in detail.

[0078] The electronic structures of these materials were analyzed using ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), and the results showed that they had strong absorption in the range of 200–1000 nm. The optical band gaps (Eg) of BMO prepared in Example 1 and BMS prepared in Example 2 obtained from the Tauc plot were 1.55 eV and 1.43 eV, respectively, indicating that they had typical n-type semiconductor characteristics and exhibited good photocatalytic potential. In addition, compared with BMO and BMS, BMS had a smaller band gap, which was more conducive to electron transfer. Generally, the reduction ability of a photocatalyst is determined by the position of its conduction band (CB), while the oxidation ability depends on the position of its valence band (VB). The CB energy levels of BMO and BMS were determined by Mott–Schottky measurements, where the flat-band potentials of BMO and BMS were -0.74 eV and -0.71 eV, respectively. For n-type semiconductors, the conduction band (CB) potential is usually ~0.2 V higher than the flat-band potential. The corresponding CB values were -0.54 V and -0.51 V obtained from these flat-band potentials. The VB of BMO and BMS were calculated to be 1.01 eV and 0.92 eV, respectively, through VB = Eg + CB, and the energy band diagram of the catalyst could be obtained based on the valence band and conduction band. The energy band diagram of a photocatalyst can accurately describe the feasibility and mechanism of the water oxidation reaction (WOR) and the oxygen reduction reaction (ORR). WOR is an oxidation process that requires the potential of the valence band (VB) to be higher than the oxygen / water pair potential of water oxidation (O2 / H2O, 0.83 V vs. NHE) to ensure that photo-generated holes (h + ) can oxidize water to oxygen. ORR is a reduction process where the CB potential is lower than ORR (O2 / H2O2, 0.28 V vs. NHE), enabling photo-generated electrons (e - ) to reduce oxygen to water. When the VB potential of the photocatalyst is higher than 0.28 V and the CB potential is lower than 0.68 V, the material can not only drive WOR to generate oxygen but also promote ORR to generate water, showing good photocatalytic potential.

[0079] The photo-generated charge separation abilities of the two photocatalysts BMO and BMS were compared through transient photocurrent measurements and impedance. In the photocurrent response spectrum, when illuminated, the photocurrent intensity of BMS was significantly higher than that of BMO, indicating that BMO had a higher photocurrent intensity, and the photo-generated electron-hole pairs had a faster separation and transfer speed, thus being able to utilize more photo-generated electrons.

[0080] Through the comparative analysis of electrochemical impedance spectroscopy (EIS), BMS had a smaller Nyquist arc radius, indicating that BMS had a lower interfacial charge transfer resistance. This characteristic was consistent with the photocurrent response results, indicating that BMS had stronger charge transfer ability and charge separation efficiency because -SO3 was introduced into BMS- It can stabilize photo-generated carriers, optimize the energy band structure and internal electric field.

[0081] The curves were plotted using the Koutecky-Levich method, and the average electron transfer numbers of BMO and BMS were calculated to be 1.89 and 1.37 respectively, indicating that two single-electron transfer mechanisms dominate the process of photocatalytic production of hydrogen peroxide.

[0082] Example 5: Performance test of photocatalyst for photocatalytic production of H2O2 Referring to Figures 4(a) and 4(b), the photocatalytic activities of two catalysts, BMO and BMS, were studied in pure water under different atmospheres. The activities of BMO and BMS for producing hydrogen peroxide were studied under N2, O2, and Air conditions. The hydrogen peroxide production under O2 atmosphere was higher than that under N2 atmosphere, indicating that O2 is one of the necessary conditions for producing H2O2 through the ORR mechanism.

[0083] However, the hydrogen peroxide production of BMS is much higher than that of BMO, and the hydrogen peroxide production of BMS reaches 3.03 mmol g -1 h -1 , because after introducing -SO3 - into BMS, while improving the hydrophilicity of BMS, it can also adsorb more reactive oxygen, improve the proton transport channel, and reduce the reaction energy barrier. Therefore, the photocatalytic activity of BMS is better.

[0084] To evaluate the recyclability and stability of BMS, a cycling experiment was carried out. After five cycles of use-recovery-reuse process, BMS still has excellent hydrogen peroxide production performance, specifically, the hydrogen peroxide production reaches 2.06 mmol g - 1 h -1 , which is 79% of the initial performance, indicating that the sulfonated photocatalyst BMS prepared by the present invention has excellent stability and reusability.

[0085] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A preparation method of a sulfonated photocatalyst, characterized in that, It includes the following steps: 2,5-dibromopyrimidine reacts with trimethylsilylacetylene in anhydrous triethylamine and tetrahydrofuran, and after extraction and purification, a first intermediate is obtained; The first intermediate is dissolved in tetrahydrofuran, and tetrabutylammonium fluoride is added dropwise below -40 °C for hydrolysis, and after extraction and purification, a second intermediate is obtained; The second intermediate and 5,10,15,20-tetrakis(4-bromophenyl)porphyrin are dissolved in N,N-dimethylformamide and diisopropylamine, and under the catalysis, a Sonogashira coupling reaction is carried out; After the coupling reaction is completed, filtration, extraction and vacuum drying are carried out to obtain an initial polymer; The initial polymer is sulfonated and modified, and then filtered, extracted and vacuum dried to obtain a sulfonated photocatalyst.

2. The preparation method of the sulfonated photocatalyst according to claim 1, characterized in that, The extractant used for the extraction is dichloromethane and deionized water.

3. The preparation method of the sulfonated photocatalyst according to claim 1, characterized in that, The purification is column chromatography purification, and the eluent used for the column chromatography is a mixture of dichloromethane and petroleum ether with a volume ratio of 3:1 - 5:

1.

4. The preparation method of the sulfonated photocatalyst according to claim 1, wherein, The molar ratio of the reaction of 5,10,15,20-tetrakis(4-bromophenyl)porphyrin to the second intermediate is 1:1 - 1:

3.

5. The preparation method of the sulfonated photocatalyst according to claim 1, characterized in that, The reaction temperature of the coupling reaction is 100 - 120 °C, and the reaction time is 2 - 6 days.

6. The preparation method of the sulfonated photocatalyst according to claim 1, characterized in that, The sulfonation modification of the initial polymer includes the following steps: Under a protective atmosphere, the initial polymer is dispersed in dichloromethane to obtain an initial polymer dispersion system; Under a protective atmosphere, chlorosulfonic acid is added dropwise to the initial polymer dispersion system and mixed in an ice bath to obtain a mixture; The mixture is stirred for a sulfonation modification reaction.

7. The preparation method of the sulfonated photocatalyst according to claim 6, characterized in that, The reaction temperature of the sulfonation modification reaction of the mixture is 20 - 30 °C, and the reaction time is 2 - 6 days.

8. The preparation method of the sulfonated photocatalyst according to claim 1, characterized in that, The extraction adopts Soxhlet extraction, and the Soxhlet extractant is methanol, dichloromethane or tetrahydrofuran.

9. The preparation method of the sulfonated photocatalyst according to claim 1, characterized in that, The drying temperature of the vacuum drying is 50 - 120 °C, and the drying time is 20 - 40 h.

10. Use of the sulfonated photocatalyst according to any one of claims 1-9 for producing H2O2 from air and water, characterized in that, It includes the following steps: The sulfonated photocatalyst is dispersed in ultrapure water to obtain a mixture; The mixture is transferred to a reactor and irradiated with xenon lamp light; Measure the production amount of H2O2 produced.

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