A polymer material for photocatalytic hydrogen peroxide production and its preparation method

Abstract

This invention belongs to the field of photocatalytic materials technology, specifically relating to a polymer material for photocatalytic hydrogen peroxide production and its preparation method. The preparation method of the polymer material includes polymerizing a pyridine aldehyde compound with an acylhydrazine compound having the structure shown in formula (1) in the presence of a catalyst and an organic solvent to obtain the polymer material; the pyridine aldehyde compound is selected from 2,2'-bipyridine-5,5'-dicarboxaldehyde and / or 3,3'-bipyridine-6,6'-dicarboxaldehyde. The key to this invention is the use of a pyridine aldehyde compound and an acylhydrazine compound with specific structures to polymerize the resulting polymer material. Due to its specific bipyridine structure and the presence of ether oxygen bonds in its side chains, the light absorption efficiency of the polymer material can be improved, which is beneficial for the polymer material to generate more photogenerated charge carriers with photocatalytic H2O2 production activity under light excitation, thereby significantly improving the yield of photocatalytic H2O2 production.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a polymer material for photocatalytic hydrogen peroxide production and its preparation method. Background Technology

[0002] Hydrogen peroxide (H2O2), as a highly efficient cleaning agent, possesses advantages such as safe operation, high oxidation potential, and water as the only byproduct, thus it is widely used in the chemical industry and environmental treatment. Currently, the commercial production of H2O2 still mainly relies on the anthraquinone process, which consumes a significant amount of energy and generates substantial chemical waste, making it neither a resource-saving nor environmentally friendly system. Therefore, there is an urgent need to develop energy-efficient and environmentally friendly methods for H2O2 production. In recent years, photocatalysis, as an emerging research field intersecting catalytic chemistry, photochemistry, semiconductor physics, materials science, and environmental science, has attracted widespread attention from researchers. Photocatalytic production of H2O2 is gradually becoming a solution for small-scale, efficient H2O2 synthesis. Currently, many reported semiconductors have been shown to possess photocatalytic H2O2 production characteristics, such as TiO2, graphitic carbon nitride (g-C3N4), metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). However, most photocatalysts require the use of sacrificial agents to exhibit good photocatalytic H2O2 production efficiency, and the synthesis methods of currently reported covalent organic frameworks (COFs) are generally complex. These factors mean that the efficiency of photocatalytic H2O2 production is far from meeting industrial needs. Summary of the Invention

[0003] The primary objective of this invention is to address the shortcomings of existing photocatalytic hydrogen peroxide production materials, which involve complex synthesis and require sacrificial agents to achieve high photocatalytic efficiency, by providing a method for preparing polymer materials.

[0004] Specifically, the preparation method of the polymer material includes polymerizing a pyridine aldehyde compound with an acylhydrazine compound having the structure shown in formula (1) in the presence of a catalyst and an organic solvent to obtain the polymer material; the pyridine aldehyde compound is selected from 2,2'-bipyridine-5,5'-dicarboxaldehyde and / or 3,3'-bipyridine-6,6'-dicarboxaldehyde;

[0005]

[0006] In formula (1), R1 and R2 are each independently C1 to C4 alkylene groups, and R3 and R4 are each independently hydrogen, hydroxyl or C1 to C4 alkoxy groups.

[0007] In a preferred embodiment, the molar ratio of the pyridine aldehyde compound to the acylhydrazine compound is 1:(1.2 to 1.8).

[0008] In a preferred embodiment, the organic solvent is selected from at least one of mesitylene, 1,4-dioxane, o-dichlorobenzene, and n-butanol.

[0009] In a preferred embodiment, the organic solvent is a mixed solution of mesitylene and 1,4-dioxane.

[0010] In a preferred embodiment, the volume ratio of mesitylene and 1,4-dioxane is (1-3):1.

[0011] In a preferred embodiment, the catalyst is an acidic catalyst.

[0012] In a preferred embodiment, the catalyst is selected from at least one of acetic acid, formic acid, and benzenesulfonic acid.

[0013] In a preferred embodiment, the catalyst is used in solution form.

[0014] In a preferred embodiment, the concentration of the catalyst in the catalyst solution is 10–15 M.

[0015] In a preferred embodiment, the volume ratio of the catalyst solution to the organic solvent is 1:(4-8).

[0016] In a preferred embodiment, the polymerization reaction is carried out at a temperature of 70–100°C for 2–4 days.

[0017] A second objective of the present invention is to provide a polymer material prepared by the above method.

[0018] A third objective of this invention is to provide the application of the polymer material prepared by the above method in photocatalytic hydrogen peroxide production.

[0019] The key to this invention lies in the polymerization reaction of specific pyridine aldehyde compounds and acylhydrazine compounds with specific structures in the presence of a catalyst and solvent. The resulting polymer material exhibits high efficiency in the photocatalytic H2O-O2 system for producing hydrogen peroxide. The reason for this is speculated to be that the polymer material possesses a specific bipyridine structure and contains ether-oxygen bonds, which enhances the light absorption efficiency of the polymer material. This facilitates the generation of more photogenerated charge carriers (photogenerated electrons and holes) with photocatalytic H2O2 production activity under light excitation, and the separation efficiency of photogenerated electrons and holes is relatively high. The photogenerated electrons generated by the polymer material under light excitation can be quickly captured and react with O2 to produce H2O2 (oxygen reduction process), while the holes left after the photogenerated electron reaction can also react with H2O to produce H2O2 (water oxidation process), thereby significantly improving the efficiency of photocatalytic H2O2 production. Attached Figure Description

[0020] Figure 1 This is the XRD pattern of the polymer material prepared in Example 1.

[0021] Figure 2 This is a SEM image of the polymer material prepared in Example 1. Detailed Implementation

[0022] The method for preparing polymer materials provided by the present invention includes polymerizing pyridine aldehyde compounds with acyl hydrazine compounds having the structure shown in formula (1) in the presence of a catalyst and a solvent to obtain polymer materials; wherein the pyridine aldehyde compounds are selected from 2,2'-bipyridine-5,5'-dicarboxaldehyde and / or 3,3'-bipyridine-6,6'-dicarboxaldehyde;

[0023]

[0024] In formula (1), R1 and R2 are each independently a C1-C4 alkylene group, and R3 and R4 are each independently hydrogen, hydroxyl, or C1-C4 alkoxy group. The C1-C4 alkylene group can be methylene, ethylene, n-propylene, isopropylene, n-butylene, sec-butylene, isobutylene, or tert-butylene. The C1-C4 alkoxy group can be methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, or tert-butoxy.

[0025] In this invention, the pyridine aldehyde compounds can be commercially available or prepared using existing methods.

[0026] In this invention, the acylhydrazine compound can be any compound having the structure shown in formula (1), which can be commercially available or prepared by existing methods. Specific examples include, but are not limited to, at least one of 2,5-dimethoxy-terephthalohydrazine, 2,5-diethoxy-terephthalohydrazine, 2,5-dipropoxy-terephthalohydrazine, 2,5-dibutoxy-terephthalohydrazine, 2,5-diisobutoxy-terephthalohydrazine, 2,5-bis(2-methoxyethoxy)-terephthalohydrazine, 2,5-bis(2-methoxypropoxy)-terephthalohydrazine, 2,5-bis(2-methoxybutoxy)-terephthalohydrazine, and 2,5-bis(2-methoxyhydroxy)-terephthalohydrazine.

[0027] In this invention, the molar ratio of the pyridine aldehyde compound to the acyl hydrazine compound is preferably 1:(1.2 to 1.8). Taking 1 mol of the pyridine aldehyde compound as a unit, the molar amount of the acyl hydrazine compound is preferably 1.2 to 1.8 mol, such as 1.2 mol, 1.3 mol, 1.4 mol, 1.5 mol, 1.6 mol, 1.7 mol, 1.8 mol, or any value between them.

[0028] In this invention, the type of organic solvent is not specifically limited, as long as it can provide a suitable reaction environment for the polymerization reaction of pyridine aldehydes and hydrazides. Specific examples include, but are not limited to, at least one of: mesitylene, 1,4-dioxane, o-dichlorobenzene, and n-butanol. More preferably, the organic solvent is a mixed solution of mesitylene and 1,4-dioxane. The volume ratio of mesitylene to 1,4-dioxane is preferably (1-3):1, such as 1:1, 1.5:1, 2:1, 2.5:1, 3:1, or any value between them.

[0029] In this invention, the type of catalyst is not specifically limited. It can be any compound that can catalyze the polymerization reaction of pyridine aldehydes and acyl hydrazides. It can be an acidic catalyst or a basic catalyst, more preferably an acidic catalyst. Specifically, it can be selected from at least one of acetic acid, formic acid, and benzenesulfonic acid.

[0030] In this invention, the catalyst is preferably used in solution form, i.e., the catalyst is mixed with a solvent to obtain a catalyst solution. The concentration of the catalyst in the catalyst solution is preferably 10–15 M, such as 10 M, 11 M, 12 M, 13 M, 14 M, 15 M, or any value between them. The solvent can be water or at least one of the above-mentioned organic solvents, more preferably water.

[0031] In this invention, the volume ratio of the catalyst solution to the organic solvent is preferably 1:(4-8), such as 1:4, 1:5, 1:6, 1:7, 1:8 or any value between them.

[0032] In this invention, the temperature of the polymerization reaction is preferably 70 to 100°C, such as 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C or any value between them; the time is preferably 2 to 4 days, such as 2 days, 2.5 days, 3 days, 3.5 days, 4 days or any value between them.

[0033] In one specific embodiment, the preparation method of the polymer material is as follows: a pyridine aldehyde compound and an acyl hydrazine compound having the structure shown in formula (1) are subjected to a polymerization reaction at 70-100°C for 2-4 days in the presence of a catalyst and an organic solvent. The resulting product is filtered, washed 2-4 times, and then dried to obtain the polymer material.

[0034] This invention provides the application of the above-mentioned polymer material in photocatalytic hydrogen peroxide production. Specifically, a method for photocatalytic hydrogen peroxide production is as follows: In a photocatalytic hydrogen peroxide production apparatus, the above-mentioned polymer material is mixed with pure water, oxygen is introduced into the mixture, and a photocatalytic hydrogen peroxide production reaction is carried out under light of a certain wavelength (visible light). The photocatalytic hydrogen peroxide production reaction process involved is as follows:

[0035] Water oxidation process: 2H₂O + 2h + →H₂O₂ + 2H⁺ +

[0036] Oxygen reduction process: O 2 +2e - +2H + →H2O2

[0037] The present invention will be described in detail below through specific embodiments.

[0038] Example 1: Preparation of Polymer Materials

[0039] 8 mg of 2,2'-bipyridine-5,5'-dicarboxaldehyde and 20 mg of 2,5-bis(2-methoxyethoxy)terephthalohydrazide were added to a reaction flask, followed by 800 μL of mesitylene and 400 μL of 1,4-dioxane as solvents. The mixture was sonicated for 15 min to dissolve and disperse the solvents evenly. Then, 200 μL of 12M acetic acid solution was added as a catalyst. The entire reaction system was placed in an oven at 85 °C for 3 days. After the reaction was completed, the mixture was cooled to room temperature and the solid product was collected by filtration. The collected solid was washed three times each with THF (tetrahydrofuran), acetone, and water, and then dried overnight in a vacuum oven at 60 °C to obtain the polymer material.

[0040] Among them, 2,2'-bipyridine-5,5'-dicarboxaldehyde has the structure shown in formula (1-1), and 2,5-bis(2-methoxyethoxy)terephthalohydrazide has the structure shown in formula (1-3).

[0041] Figure 1 The image shows the XRD pattern of the polymer material prepared in this embodiment, indicating that a polymer material with a crystalline structure was successfully synthesized. Figure 2 This is a SEM image of the polymer material prepared in this embodiment. It can be seen that the polymer surface is not smooth and flat, which is conducive to exposing more active sites and improving the efficiency of photocatalytic H2O2 production.

[0042] Example 2 Preparation of Polymer Materials

[0043] 8 mg of 3,3'-bipyridine-6,6'-dicarboxaldehyde and 20 mg of 2,5-bis(2-methoxyethoxy)terephthalohydrazide were added to a reaction flask, followed by 800 μL of mesitylene and 400 μL of 1,4-dioxane as solvents. The mixture was sonicated for 15 min to dissolve and disperse the solvents evenly. Then, 200 μL of 12M acetic acid solution was added as a catalyst. The entire reaction system was placed in an oven at 85 °C for 3 days. After the reaction was completed, the mixture was cooled to room temperature and the solid product was collected by filtration. The collected solid was washed three times each with THF (tetrahydrofuran), acetone, and water, and then dried overnight in a vacuum oven at 60 °C to obtain the polymer material.

[0044] Among them, 3,3'-bipyridine-6,6'-dicarboxaldehyde has the structure shown in formula (1-2).

[0045] Example 3: Preparation of Polymer Materials

[0046] 8 mg of 2,2'-bipyridine-5,5'-dicarboxaldehyde and 20 mg of 2,5-bis(3-hydroxypropoxy)terephthalohydrazide were added to a reaction flask, followed by 800 μL of mesitylene and 400 μL of 1,4-dioxane as solvents. The mixture was sonicated for 15 min to dissolve and disperse the solvents evenly. Then, 200 μL of 12M acetic acid solution was added as a catalyst. The entire reaction system was placed in an oven at 85 °C for 3 days. After the reaction was completed, the mixture was cooled to room temperature and the solid product was collected by filtration. The collected solid was washed three times each with THF (tetrahydrofuran), acetone, and water, and then dried overnight in a vacuum oven at 60 °C to obtain the polymer material.

[0047] Among them, 2,5-bis(3-hydroxypropoxy)terephthalohydrazide has the structure shown in formula (1-4).

[0048] Example 4: Preparation of Polymer Materials

[0049] 8 mg of 2,2'-bipyridine-5,5'-dicarboxaldehyde and 20 mg of 2,5-dipropoxyterephthalohydrazide were added to a reaction flask, followed by 800 μL of mesitylene and 400 μL of 1,4-dioxane as solvents. The mixture was sonicated for 15 min to dissolve and disperse the solvents evenly. Then, 200 μL of 12M acetic acid solution was added as a catalyst. The entire reaction system was placed in an oven at 85 °C for 3 days. After the reaction was completed, the mixture was cooled to room temperature and the solid product was collected by filtration. The collected solid was washed three times each with THF (tetrahydrofuran), acetone, and water, and then dried overnight in a vacuum oven at 60 °C to obtain the polymer material.

[0050] Among them, 2,5-dipropoxyterephthalohydrazide has the structure shown in formula (1-5).

[0051]

[0052] Preparation of the reference polymer material in Comparative Example 1

[0053] 8 mg of 2,2'-bipyridine-5,5'-dicarboxaldehyde and 12 mg of dihydrazine terephthalate were added to a reaction flask, followed by 800 μL of mesitylene and 400 μL of 1,4-dioxane as solvents. The mixture was sonicated for 15 min to dissolve and disperse the solvent evenly. Then, 200 μL of 12M acetic acid solution was added as a catalyst. The entire reaction system was placed in an oven at 85 °C for 3 days. After the reaction was completed, the mixture was cooled to room temperature and the solid product was collected by filtration. The collected solid was washed three times each with THF (tetrahydrofuran), acetone, and water, and then dried overnight in a vacuum oven at 60 °C to obtain the reference polymer material.

[0054] Comparative Example 2: Preparation of the reference polymer material

[0055] 8 mg of 3,3'-bipyridine-6,6'-dicarboxaldehyde and 12 mg of dihydrazine terephthalate were added to a reaction flask, followed by 800 μL of mesitylene and 400 μL of 1,4-dioxane as solvents. The mixture was sonicated for 15 min to dissolve and disperse the solvent evenly. Then, 200 μL of 12 M acetic acid solution was added as a catalyst. The entire reaction system was placed in an oven at 85 °C for 3 days. After the reaction was completed, the mixture was cooled to room temperature and the solid product was collected by filtration. The collected solid was washed three times each with THF (tetrahydrofuran), acetone, and water, and then dried overnight in a vacuum oven at 60 °C to obtain the reference polymer material.

[0056] Test case

[0057] (1) The performance of the polymer materials prepared in the above examples and comparative examples for photocatalytic H2O2 production was tested according to the following method: 10 mg of polymer material and 20 mL of deionized water were mixed and stirred in a quartz reactor for 10 min, and ultrasonically treated for 10 min to make the suspension solution uniformly distributed. After aeration in an oxygen atmosphere for 30 min, a 300 W xenon light source (PLS-SXE 300+) with a filter was used as the light source (visible wavelength range). The quartz reaction device was placed under light for 2 h. After centrifugation at 12000 rpm for 5 min, the supernatant was filtered using a syringe with a 0.45 μm filter. The hydrogen peroxide concentration was determined using the DPD method. A standard curve for different H2O2 concentrations was first established. After diluting the sample to be tested, the absorbance of different samples was measured at 551 nm using a UV-Vis spectrometer. The efficiency of photocatalytic hydrogen peroxide production was calculated according to the standard curve. The results are shown in Table 1.

[0058] (2) The performance of photocatalytic H2O2 production was tested according to the method in (1), except that the atmosphere was puffed with Ar for 30 min before irradiation, while the other conditions were the same. The results are shown in Table 1.

[0059] (3) The performance of photocatalytic H2O2 production was tested according to the method in (1), except that oxygen was isolated in the reaction system and 5 mg of AgNO3 was added as an electron scavenger, while the other conditions were the same. The results are shown in Table 1.

[0060] Table 1

[0061]

[0062] As shown in Table 1, compared to Comparative Examples 1-2, the polymer materials prepared in Examples 1-4 exhibit significantly improved photocatalytic H2O2 production efficiency. Under an Ar atmosphere, the reaction system produced virtually no H2O2 (the H2O2 production efficiency of both the examples and the comparative examples was less than 13 μmol g). -1 h -1 This indicates that oxygen reduction to produce H2O2 is the dominant process in the photocatalytic H2O2 production system of the polymer material provided by this technical solution, and photogenerated electrons are the main active substances in the photocatalytic H2O2 production of this reaction system. Adding AgNO3 to the reaction system, under oxygen-isolated conditions, significantly reduces the photocatalytic H2O2 production efficiency (the H2O2 production efficiency of Examples 1-4 and Comparative Example 1 all decreased by approximately 50% or even more), indicating that the photocatalytic H2O2 production system of the polymer material provided by this technical solution includes a water oxidation process to produce H2O2, and photogenerated holes are also active substances in the photocatalytic H2O2 production of this reaction system.

[0063] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for preparing a polymer material, characterized in that, The method includes polymerizing a pyridine aldehyde compound with an acylhydrazine compound having the structure shown in formula (1) in the presence of a catalyst and an organic solvent to obtain a polymer material; wherein the pyridine aldehyde compound is selected from 2,2'-bipyridine-5,5'-dicarboxaldehyde and / or 3,3'-bipyridine-6,6'-dicarboxaldehyde; In formula (1), R1 and R2 are each independently C1 to C4 alkylene groups, and R3 and R4 are each independently hydrogen, hydroxyl or C1 to C4 alkoxy groups.

2. The method for preparing the polymer material according to claim 1, characterized in that, The molar ratio of the pyridine aldehyde compound to the acylhydrazine compound is 1:(1.2 to 1.8).

3. The method for preparing the polymer material according to claim 1, characterized in that, The organic solvent is selected from at least one of mesitylene, 1,4-dioxane, o-dichlorobenzene, and n-butanol.

4. The method for preparing the polymer material according to claim 3, characterized in that, The organic solvent is a mixed solution of mesitylene and 1,4-dioxane.

5. The method for preparing the polymer material according to claim 4, characterized in that, The volume ratio of mesitylene and 1,4-dioxane is (1-3):

1.

6. The method for preparing the polymer material according to claim 1, characterized in that, The catalyst is an acidic catalyst.

7. The method for preparing the polymer material according to claim 1, characterized in that, The catalyst is selected from at least one of acetic acid, formic acid, and benzenesulfonic acid.

8. The method for preparing the polymer material according to claim 1, characterized in that, The catalyst is used in the form of a catalyst solution.

9. The method for preparing the polymer material according to claim 8, characterized in that, The concentration of the catalyst in the catalyst solution is 10–15 M.

10. The method for preparing the polymer material according to claim 8, characterized in that, The volume ratio of the catalyst solution to the organic solvent is 1:(4-8).

11. The method for preparing the polymer material according to claim 1, characterized in that, The polymerization reaction is carried out at a temperature of 70–100°C for 2–4 days.

12. A polymer material prepared by the method for preparing polymer materials according to any one of claims 1 to 11.

13. The application of the polymer material of claim 12 in photocatalytic hydrogen peroxide production.

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