Polymer material for producing hydrogen peroxide through photocatalysis and preparation method thereof

Abstract

The invention belongs to the technical field of photocatalytic materials, and particularly relates to a polymer material for producing hydrogen peroxide through photocatalysis and a preparation method of the polymer material. The preparation method of the polymer material comprises the following steps: carrying out polymerization reaction on a pyridine aldehyde compound and a hydrazide compound with a structure as shown in a 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 point of the invention is that the polymer material is obtained by carrying out polymerization reaction on the pyridine aldehyde compound and the hydrazide compound which have specific structures, and the polymer material has a specific bipyridine structure and a side chain contains an ether oxygen bond, so that the light absorption efficiency of the polymer material can be improved; the polymer material can generate more photon-generated carriers with photocatalytic H2O2 production activity under illumination excitation, so that the yield of photocatalytic H2O2 production can be remarkably improved. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic materials, and in particular relates to a polymer material for photocatalytically producing hydrogen peroxide and a preparation method thereof. Background Art

[0002] Hydrogen peroxide (H2O2) is an efficient cleaning agent with advantages such as safe operation, high oxidation potential and only water as a byproduct. Therefore, it is widely used in the chemical industry and environmental treatment. At present, the commercial production of H2O2 still mainly relies on the anthraquinone method, which consumes a lot of energy and produces a large amount of chemical waste. It is not a resource-saving and environmentally friendly system. Therefore, it is urgent to develop some energy-saving and environmentally friendly methods to produce H2O2. In recent years, photocatalysis has attracted widespread attention from researchers as an emerging research field that crosses multiple disciplines such as catalytic chemistry, photochemistry, semiconductor physics, materials science, and environmental science. Photocatalytic production of H2O2 has gradually become a solution strategy for small-scale and efficient synthesis of H2O2. At present, many reported semiconductors have been proven to have the characteristics of photocatalytic production of H2O2, such as TiO2, graphite-like carbon nitride (g-C3N4), metal organic frameworks (MOFs) and covalent organic frameworks (COFs). However, most photocatalysts require the use of sacrificial agents to show good photocatalytic H2O2 production efficiency, and the synthesis methods of the covalent organic frameworks (COFs) materials reported so far are generally complex. These reasons result in the efficiency of photocatalytic H2O2 production being far from meeting industrial needs. Summary of the invention

[0003] The first purpose of the present invention is to provide a method for preparing a polymer material in view of the shortcomings of existing photocatalytic hydrogen peroxide production materials, which are complex to synthesize and require sacrificial agents to achieve high photocatalytic efficiency.

[0004] Specifically, the preparation method of the polymer material comprises polymerizing a pyridine aldehyde compound and a hydrazide compound having a structure represented by formula (1) in the presence of a catalyst and an organic solvent to obtain a 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 a C1-C4 alkylene group, and R3 and R4 are each independently a hydrogen atom, a hydroxyl group or a C1-C4 alkoxy group.

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

[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 to 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 the form of a solution.

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

[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 temperature is 70-100° C. and the time is 2-4 days.

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

[0018] The third object of the present invention is to provide the use of the polymer material prepared by the above method in photocatalytic production of hydrogen peroxide.

[0019] The key of the present invention is to use a specific pyridine aldehyde compound and a hydrazide compound with a specific structure to carry out a polymerization reaction under the condition of a catalyst and a solvent, so that the polymer material prepared has a high efficiency of producing hydrogen peroxide in a photocatalytic H2O-O2 system. It is speculated that the reason may be that: the polymer material has a specific bipyridine structure and contains an ether oxygen bond, which can improve the light absorption efficiency of the polymer material, and is conducive to the polymer material to generate more photogenerated carriers (photogenerated electrons and holes) with photocatalytic H2O2 activity under light excitation, and the separation efficiency of photogenerated electrons and holes is high. The photogenerated electrons generated by the polymer material under the excitation of light can be quickly captured and react with O2 to produce H2O2 (oxygen reduction process), and 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the XRD diagram 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 DESCRIPTION

[0022] The preparation method of the polymer material provided by the present invention comprises the steps of polymerizing a pyridine aldehyde compound and a hydrazide compound having a structure represented by formula (1) in the presence of a catalyst and a solvent to obtain a polymer material; the pyridine aldehyde compound is 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 a hydrogen, a hydroxyl group, or a C1-C4 alkoxy group. The C1-C4 alkylene group may be a methylene group, an ethylene group, a n-propylene group, an isopropylene group, a n-butylene group, a sec-butylene group, an isobutylene group, or a tert-butylene group. The C1-C4 alkoxy group may be a methoxy group, an ethoxy group, a n-propoxy group, an isopropoxy group, a n-butoxy group, an isobutoxy group, a sec-butoxy group, or a tert-butoxy group.

[0025] In the present invention, the pyridine aldehyde compound can be commercially available or prepared by an existing method.

[0026] In the present invention, the hydrazide compound can be any compound having the structure shown in formula (1), and can be commercially available or prepared by an existing method. Specific examples thereof include, but are not limited to, at least one of 2,5-dimethoxyterephthaloyl hydrazide, 2,5-diethoxyterephthaloyl hydrazide, 2,5-dipropoxyterephthaloyl hydrazide, 2,5-dibutoxyterephthaloyl hydrazide, 2,5-diisobutoxyterephthaloyl hydrazide, 2,5-bis(2-methoxyethoxy)terephthaloyl hydrazide, 2,5-bis(2-methoxypropoxy)terephthaloyl hydrazide, 2,5-bis(2-methoxybutoxy)terephthaloyl hydrazide and 2,5-bis(2-methoxyhydroxy)terephthaloyl hydrazide.

[0027] In the present invention, the molar ratio of the pyridine aldehyde compound to the hydrazide compound is preferably 1:(1.2-1.8). Taking the molar amount of the pyridine aldehyde compound as 1 mol, the molar amount of the hydrazide compound is preferably 1.2-1.8 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 therebetween.

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

[0029] In the present invention, the type of the catalyst is not specifically limited, and it is mainly a class of compounds that can catalyze the polymerization reaction of pyridine aldehyde compounds and hydrazide compounds. It can be an acidic catalyst or a basic catalyst, more preferably an acidic catalyst, which can be specifically selected from at least one of acetic acid, formic acid, and benzenesulfonic acid.

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

[0031] In the present 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 therebetween.

[0032] In the present invention, the polymerization reaction temperature is preferably 70-100°C, such as 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C or any value therebetween; the reaction time is preferably 2-4d, such as 2d, 2.5d, 3d, 3.5d, 4d or any value therebetween.

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

[0034] The present invention provides an application of the above polymer material in photocatalytic production of hydrogen peroxide. Specifically, a method for photocatalytic production of hydrogen peroxide is as follows: in a device for photocatalytic production of hydrogen peroxide, the above polymer material is mixed with pure water, oxygen is introduced into the mixed liquid, and a photocatalytic production of hydrogen peroxide reaction is carried out under light of a certain wavelength (visible light). The photocatalytic production of hydrogen peroxide 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)terephthaloylhydrazide were added to a reaction bottle, and then 800 μL of mesitylene and 400 μL of 1,4-dioxane were added as solvents. The mixture was dissolved and evenly dispersed by ultrasonic treatment for 15 min, and then 200 μL of 12M acetic acid solution was added as a catalyst. The whole 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 3 times with THF (tetrahydrofuran), acetone and water respectively, and then dried in a vacuum oven at 60°C overnight to obtain a polymer material.

[0040] Among them, 2,2'-bipyridine-5,5'-dicarbaldehyde has a structure as shown in formula (1-1), and 2,5-bis(2-methoxyethoxy)terephthaloylhydrazide has a structure as shown in formula (1-3).

[0041] Figure 1 is the XRD pattern of the polymer material prepared in this example, indicating that the polymer material with a crystalline structure is successfully synthesized. Figure 2 This is the SEM image of the polymer material prepared in this example. 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)terephthaloylhydrazide were added to a reaction bottle, and then 800 μL of mesitylene and 400 μL of 1,4-dioxane were added as solvents. The mixture was dissolved and evenly dispersed by ultrasonic treatment for 15 min, and then 200 μL of 12M acetic acid solution was added as a catalyst. The whole 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 with THF (tetrahydrofuran), acetone and water respectively, and then dried in a vacuum oven at 60°C overnight to obtain a polymer material.

[0044] Among them, 3,3'-bipyridine-6,6'-dicarbaldehyde has a structure as 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)terephthaloylhydrazide were added to a reaction bottle, and then 800 μL of mesitylene and 400 μL of 1,4-dioxane were added as solvents. The mixture was dissolved and evenly dispersed by ultrasonic treatment for 15 min, and then 200 μL of 12M acetic acid solution was added as a catalyst. The whole 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 with THF (tetrahydrofuran), acetone and water respectively, and then dried in a vacuum oven at 60°C overnight to obtain a polymer material.

[0047] Among them, 2,5-bis(3-hydroxypropoxy)terephthaloylhydrazide has a structure as 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-dipropoxyterephthaloyl hydrazide were added to a reaction bottle, and then 800 μL of mesitylene and 400 μL of 1,4-dioxane were added as solvents. The mixture was dissolved and evenly dispersed by ultrasonic treatment for 15 min, and then 200 μL of 12M acetic acid solution was added as a catalyst. The whole 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 with THF (tetrahydrofuran), acetone and water respectively, and then dried in a vacuum oven at 60°C overnight to obtain a polymer material.

[0050] Among them, 2,5-dipropoxyterephthaloylhydrazide has a structure as shown in formula (1-5).

[0051]

[0052] Comparative Example 1 Preparation of Reference Polymer Material

[0053] 8 mg of 2,2'-bipyridine-5,5'-dicarboxaldehyde and 12 mg of terephthalic acid dihydrazine were added to a reaction bottle, and then 800 μL of mesitylene and 400 μL of 1,4-dioxane were added as solvents. The mixture was dissolved and evenly dispersed by ultrasonic treatment for 15 min, and then 200 μL of 12M acetic acid solution was added as a catalyst. The whole 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 with THF (tetrahydrofuran), acetone and water respectively, and then dried in a vacuum oven at 60°C overnight to obtain a reference polymer material.

[0054] Comparative Example 2 Preparation of Reference Polymer Material

[0055] 8 mg of 3,3'-bipyridine-6,6'-dicarboxaldehyde and 12 mg of terephthalic acid dihydrazine were added to a reaction bottle, and then 800 μL of mesitylene and 400 μL of 1,4-dioxane were added as solvents. The mixture was dissolved and evenly dispersed by ultrasonic treatment for 15 min, and then 200 μL of 12M acetic acid solution was added as a catalyst. The whole 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 with THF (tetrahydrofuran), acetone and water respectively, and then dried in a vacuum oven at 60°C overnight to obtain a reference polymer material.

[0056] Test Case

[0057] (1) The polymer materials prepared in the above examples and comparative examples were tested for the performance of photocatalytic H2O2 production according to the following method: 10 mg of the 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 for 30 min in an oxygen atmosphere, a 300W xenon light source (PLS-SXE 300+) with a filter added was used as the light source (visible light wavelength range), and the quartz reaction device was placed under illumination for 2 h. After centrifugation at 12000 rpm for 5 min, the supernatant was filtered using a syringe with a 0.45 um filter, and the hydrogen peroxide concentration was determined using the DPD method. The standard curve of different H2O2 concentrations was first calibrated, and the sample to be tested was diluted, and then the absorbance of different samples was measured at 551 nm using a UV-Vis spectrometer. The efficiency of photocatalytic hydrogen peroxide production was obtained after calculation based on the standard curve. The results are shown in Table 1.

[0058] (2) The performance test of photocatalytic H2O2 production was carried out according to the method in (1), except that the atmosphere was aerated for 30 minutes under Ar atmosphere before illumination, and the other conditions were the same. The results are shown in Table 1.

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

[0060] Table 1

[0061]

[0062] It can be seen from the data in Table 1 that, compared with Comparative Examples 1 to 2, the polymer materials prepared in Examples 1 to 4 have significantly improved photocatalytic H2O2 production efficiency. In the Ar atmosphere, the reaction system basically does not produce H2O2 (the efficiency of H2O2 production in the examples and comparative examples is less than 13 μmol g -1 h -1 ), indicating that oxygen reduction to produce H2O2 is the dominant process of the polymer material photocatalytic H2O2 production system provided by the present technical solution, and photogenerated electrons are the main active substances for the photocatalytic production of H2O2 in the reaction system. When AgNO3 is added to the reaction system, the efficiency of photocatalytic H2O2 production is greatly reduced under the condition of oxygen isolation (the efficiency of H2O2 production in Examples 1 to 4 and Comparative Example 1 is reduced by about 50% or even more than 50%), indicating that the polymer material photocatalytic H2O2 production system provided by the present technical solution includes the process of water oxidation to produce H2O2, and photogenerated holes are also the active substances for the photocatalytic production of H2O2 in the reaction system.

[0063] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for preparing a polymer material, characterized in that: The method comprises polymerizing a pyridine aldehyde compound and a hydrazide compound having a structure shown in formula (1) in the presence of a catalyst and an organic solvent to obtain a polymer material; 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 a C1-C4 alkylene group, and R3 and R4 are each independently a hydrogen atom, a hydroxyl group or a C1-C4 alkoxy group.

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

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

1.

5. The method for preparing a polymer material according to claim 1, characterized in that: The catalyst is an acidic catalyst; Preferably, the catalyst is selected from at least one of acetic acid, formic acid and benzenesulfonic acid.

6. The method for preparing a polymer material according to claim 1, characterized in that: The catalyst is used in the form of a solution; preferably, the concentration of the catalyst in the catalyst solution is 10-15M.

7. The method for preparing a polymer material according to claim 6, characterized in that: The volume ratio of the catalyst solution to the organic solvent is 1:(4-8).

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

9. A polymer material prepared by the method for preparing a polymer material according to any one of claims 1 to 8.

10. Use of the polymer material according to claim 9 in photocatalytic production of hydrogen peroxide.

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