Preparation of novel hydroxyl-modified covalent organic framework materials and their application in photosynthesis of hydrogen peroxide

Abstract

The application discloses a preparation method of a novel hydroxyl-modified covalent organic framework material and application of the material in photosynthesis of hydrogen peroxide. The application uses C3 symmetric amino building blocks, 2,2'-dipyridyl-5,5'-diformyl and propanol as reaction raw materials, and polymerizes under the condition of a Debus-Miller reaction to obtain the hydroxyl-modified covalent organic framework material. The hydroxyl modification mode enhances the electronic conjugation effect of the covalent organic framework material, and improves the efficiency of the covalent organic framework material in photosynthesis of hydrogen peroxide.

Description

Technical Field

[0001] This invention belongs to the field of organic photocatalytic materials technology, specifically relating to a method for preparing a novel hydroxyl-modified covalent organic framework material and its application in the photosynthesis of hydrogen peroxide. Background Technology

[0002] Hydrogen peroxide, with its high energy density and ease of transport, is widely used in sterilization, chemical synthesis, energy conversion, and fuel cells. However, the current main industrial method for synthesizing hydrogen peroxide is the anthraquinone process, which is energy-intensive, costly, and does not meet the requirements of green chemistry. Photocatalytic synthesis of hydrogen peroxide utilizes semiconductor materials to absorb solar energy and catalyze the production of water and oxygen. This method offers significant advantages in terms of environmental friendliness and sustainability compared to the traditional anthraquinone process.

[0003] Covalent organic frameworks (COFs) are porous, highly crystalline polymer materials formed by covalently linked organic units. COFs possess advantages such as tunable pore size, periodically ordered structure, and tunable band and electronic structures. Therefore, COFs have attracted considerable attention as a promising photocatalyst. Generally, the rational introduction of active groups can effectively modulate the photocatalytic properties of COF materials. Specifically, hydroxyl modification can reduce the oxygen adsorption energy of COFs and enhance the electron conjugation effect. Increasing the number of hydroxyl groups in the COF backbone can also significantly improve the separation and migration efficiency of photoexcited charges and the hydrophilicity of the material. However, current hydroxyl modification in COF materials is mostly limited to monomer design. Furthermore, the inherent strong polarization effect of widely used imine bonds hinders the transport of photoexcited charges, limiting the photocatalytic efficiency of COF materials. In recent years, post-modification of imine bonds through cascade bonding via reversible and irreversible reactions has become an effective strategy to eliminate imine bond polarization. In view of this, we designed a scheme for hydroxyl-modified covalent organic framework materials. By rationally introducing hydroxyl active groups, we locked the imine bonds, which improved the overall stability of the material and eliminated the polarization of the imine bonds. Summary of the Invention

[0004] This invention aims to provide a novel method for preparing hydroxyl-modified covalent organic framework materials and their application in the photosynthesis of hydrogen peroxide. The invention synthesizes a novel hydroxyl-modified covalent organic framework material via the debner-Müller reaction and compares it with a corresponding covalent organic framework material synthesized via the Schiff base reaction. This modification method effectively enhances the conjugation degree of the covalent organic framework material, further improving its carrier migration efficiency in the photocatalytic process. Simultaneously, the introduction of hydroxyl groups enhances the hydrophilicity of the material, thereby significantly improving the efficiency of hydrogen peroxide photosynthesis.

[0005] The present invention discloses a method for preparing a novel hydroxyl-modified covalent organic framework material, which uses C3 symmetrical amino building units, 2,2'-bipyridine-5,5'-dicarboxaldehyde and acetone alcohol as reactants, and polymerizes them under the conditions of the de Bühner-Müller reaction to obtain a hydroxyl-modified covalent organic framework material.

[0006] The structure of the C3 symmetric amino building block is shown in equation (1):

[0007]

[0008] Specifically, the steps include the following:

[0009] C3 symmetric amino building blocks and 2,2'-bipyridine-5,5'-dicarboxaldehyde were added to a Shrek tube. Trimethylbenzene, dioxane, acetic acid solution and acetone alcohol were added to prepare a reaction mixture. Then, three freeze-degassing cycles were performed. The degassed Shrek tube was placed in a pure oxygen environment for reaction. After the reaction was completed, the hydroxyl-modified covalent organic framework material was obtained through post-treatment and purification.

[0010] Preferably, the molar ratio of the C3 symmetrical amino building unit, 2,2'-bipyridine-5,5'-dicarboxaldehyde, and acetone alcohol is 2:3:9.

[0011] Preferably, the volume ratio of mesitylene, dioxane and acetic acid solution is (14-15):(5-6):1.

[0012] Preferably, the concentration of the acetic acid solution is 17.5 mol / L.

[0013] Preferably, the reaction temperature is 120℃ and the reaction time is 3 days.

[0014] The post-processing and purification consisted of filtration followed by washing with methanol, ethyl acetate, and n-hexane, and finally Soxhlet extraction using methanol, ethyl acetate, and n-hexane as solvents.

[0015] The novel hydroxyl-modified covalent organic framework material prepared by this invention has the structure shown in formula (2) below:

[0016]

[0017] The present invention also provides a method for preparing a corresponding covalent organic framework material. In comparison, a covalent organic framework material is obtained by polymerization of C3 symmetrical amino building units and 2,2'-bipyridine-5,5'-dicarboxaldehyde under Schiff base reaction conditions.

[0018] The structure of the C3 symmetric amino building block is shown in equation (1) above.

[0019] Specifically, the steps include the following:

[0020] C3 symmetric amino building blocks and 2,2'-bipyridine-5,5'-dicarboxaldehyde were added to a Pyrex tube, followed by a reaction mixture of mesitylene, dioxane, and acetic acid. The mixture was then subjected to three freeze-degassing cycles. The degassed Pyrex tube was then sealed at the top with a flame. After sealing, the reaction was carried out. After the reaction was completed, the covalent organic framework material was obtained through post-processing and purification.

[0021] Preferably, the molar ratio of the C3 symmetric amino building unit to 2,2'-bipyridine-5,5'-dicarboxaldehyde is 2:3.

[0022] Preferably, the ratio of mesitylene, dioxane and acetic acid solution is (17-18) ml: (2-3) ml: (1-2) ml.

[0023] Preferably, the concentration of the acetic acid solution is (6-17.5) mol / L.

[0024] Preferably, the reaction temperature is 120℃ and the reaction time is 3 days.

[0025] The post-treatment and purification consisted of filtration followed by washing with tetrahydrofuran, N,N-dimethylformamide and methanol, and finally Soxhlet extraction using tetrahydrofuran, water and methanol as solvents.

[0026] The structure of the covalent organic framework material prepared by this invention is shown in formula (3):

[0027]

[0028] The covalent organic framework materials and hydroxyl-modified covalent organic framework materials prepared by this invention both have high crystallinity.

[0029] This invention relates to the application of a novel hydroxyl-modified covalent organic framework material as a photocatalyst in the photocatalytic synthesis of hydrogen peroxide.

[0030] The hydroxyl-modified covalent organic framework material prepared by this invention has a higher degree of conjugation and better hydrophilicity compared with other covalent organic framework materials, thus improving the efficiency of photosynthetic hydrogen peroxide. Attached Figure Description

[0031] Figure 1 a is the chemical reaction formula for the preparation of covalent organic framework materials in Example 1 of this invention; Figure 1 b is the chemical reaction formula for the preparation of covalent organic framework materials in Example 2 of this invention.

[0032] Figure 2 a is the synthetic chemical reaction formula for preparing novel hydroxyl-modified covalent organic framework materials in Example 3 of this invention; Figure 2b is the chemical reaction formula for the preparation of novel hydroxyl-modified covalent organic framework materials in Example 4 of this invention.

[0033] Figure 3 a is the infrared spectrum of the covalent organic framework material and the hydroxyl-modified covalent organic framework material obtained in Examples 1 and 3 of the present invention; Figure 3 b is the carbon-13 solid-state NMR characterization of the covalent organic framework material and the hydroxyl-modified covalent organic framework material obtained in Examples 1 and 3 of the present invention; Figure 3 c is the photoelectron spectrum of the covalent organic framework material and the hydroxyl-modified covalent organic framework material obtained in Examples 1 and 3 of this invention.

[0034] Figure 4 a is the infrared spectrum of the covalent organic framework material and the hydroxyl-modified covalent organic framework material obtained in Examples 2 and 4 of the present invention; Figure 4 b is the carbon-13 solid-state NMR characterization diagram of the covalent organic framework material and the hydroxyl-modified covalent organic framework material obtained in Examples 2 and 4 of the present invention; Figure 4 c is the photoelectron spectrum of the covalent organic framework material and the hydroxyl-modified covalent organic framework material obtained in Examples 2 and 4 of this invention.

[0035] Figure 5 These are powder diffraction patterns and crystal structure simulation diagrams of the covalent organic framework materials and hydroxyl-modified covalent organic framework materials obtained in Examples 1, 2, 3, and 4 of this invention.

[0036] Figure 6 This is a comparison chart of the efficiency of photosynthesis of hydrogen peroxide between the covalent organic framework materials and the hydroxyl-modified covalent organic framework materials obtained in Examples 1, 2, 3, and 4 of this invention under a pure water oxygen-saturated atmosphere. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] The present invention first provides a covalent organic framework material, the structure of which is shown in formula (3) for comparison.

[0039] The preparation method of this covalent organic framework material includes: using C3 symmetric amino building units and 2,2'-bipyridine-5,5'-dicarboxaldehyde as reactants to carry out a Schiff base reaction in a vacuum environment under the catalysis of acetic acid solution to obtain the covalent organic framework material.

[0040] Example 1:

[0041] 20.4 mg of 2,2'-bipyridine-5,5'-dicarboxaldehyde and 22.7 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine were added to a Pyrex tube, along with 1.7 mL of mesitylene and 0.3 mL of dioxane. The mixture was sonicated for 5 minutes to ensure homogeneity. After sonication, 0.1 mL of 17.5 mol / L acetic acid solution was added, followed by sonication for another 3 minutes to obtain a homogeneous reaction mixture. The Pyrex tube containing the reaction mixture was subjected to three freeze-degassing cycles. After degassing, the top of the Pyrex tube was sealed with a flame. The sealed Pyrex tube was then placed at 120°C for 3 days. After the reaction was completed, the product was filtered and washed with tetrahydrofuran, N,N-dimethylformamide and methanol. Finally, Soxhlet extraction was performed for three days using tetrahydrofuran, water and methanol as solvents. After purification, the product was placed in a vacuum dryer at 60°C for 24 hours. The obtained product was ground into powder using a mortar and pestle to obtain a covalent organic framework material, denoted as BPY-TFPT COF.

[0042] Example 2:

[0043] 20.4 mg of 2,2'-bipyridine-5,5'-dicarboxaldehyde and 22.5 mg of 1,3,5-tris(4-aminophenyl)benzene were added to a Pyrex tube, along with 1.8 mL of mesitylene and 0.2 mL of dioxane. The mixture was sonicated for 5 minutes to ensure homogeneity. After sonication, 0.2 mL of 6 mol / L acetic acid solution was added, followed by sonication for another 3 minutes to obtain a homogeneous reaction mixture. The Pyrex tube containing the reaction mixture was subjected to three freeze-degassing cycles. After degassing, the top of the Pyrex tube was sealed with a flame. The sealed Pyrex tube was then placed at 120°C for 3 days. After the reaction was completed, the product was filtered and washed with tetrahydrofuran, N,N-dimethylformamide and methanol. Finally, Soxhlet extraction was performed for three days using tetrahydrofuran, water and methanol as solvents. After purification, the product was placed in a vacuum dryer at 60°C for 24 hours. The obtained product was ground into powder using a mortar and pestle to obtain a covalent organic framework material, denoted as BPY-TFPB COF.

[0044] This invention provides a hydroxyl-modified covalent organic framework material, the structure of which is shown in formula (2).

[0045] The preparation method of this hydroxyl-modified covalent organic framework material includes: using C3 symmetric amino building units, 2,2'-bipyridine-5,5'-dicarboxaldehyde and acetone alcohol as reactants to carry out the debner-Müller reaction in a pure oxygen environment and under the catalysis of acetic acid solution to obtain the hydroxyl-modified covalent organic framework material.

[0046] Example 3:

[0047] 20.4 mg of 2,2'-bipyridine-5,5'-dicarboxaldehyde and 22.7 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine were added to a 25 mL Shrek tube, along with 1.4 mL of mesitylene, 0.6 mL of dioxane, and 0.1 mL of 17.5 mol / L acetic acid solution. The mixture was sonicated for 30 minutes to ensure homogeneity. After sonication, 0.02 mL of acetone alcohol was added to prepare a reaction mixture. The Shrek tube containing the reaction mixture was subjected to three freeze-degassing cycles. The degassed reaction system was then placed in a pure oxygen environment and reacted at 120 °C for 3 days. After the reaction, the mixture was filtered and washed with methanol, ethyl acetate, and n-hexane. Finally, Soxhlet extraction was performed for three days using methanol, ethyl acetate, and n-hexane as solvents. The product was then dried under vacuum at 60 °C for 24 hours. The obtained product was ground into powder using a mortar and pestle to obtain a hydroxyl-modified covalent organic framework material, denoted as QL-TFPT COF.

[0048] Example 4:

[0049] 20.4 mg of 2,2'-bipyridine-5,5'-dicarboxaldehyde and 22.5 mg of 1,3,5-tris(4-aminophenyl)benzene were added to a 25 mL Shrek tube, along with 1.5 mL of mesitylene, 0.5 mL of dioxane, and 0.1 mL of 17.5 mol / L acetic acid solution. The mixture was sonicated for 30 minutes to ensure homogeneity. After sonication, 0.02 mL of acetone alcohol was added to prepare a reaction mixture. The Shrek tube containing the reaction mixture was subjected to three freeze-degassing cycles. The degassed reaction system was then placed in a pure oxygen environment and reacted at 120 °C for 3 days. After the reaction, the mixture was filtered and washed with methanol, ethyl acetate, and n-hexane. Finally, Soxhlet extraction was performed for three days using methanol, ethyl acetate, and n-hexane as solvents. The product was then vacuum dried at 60 °C for 24 hours. The obtained product was ground into powder using a mortar and pestle to obtain a hydroxyl-modified covalent organic framework material, denoted as QL-TFPB COF.

[0050] Figure 1 a is the chemical reaction formula for the preparation of covalent organic framework materials in Example 1 of this invention; Figure 1 b is the chemical reaction formula for the preparation of covalent organic framework materials in Example 2 of this invention.

[0051] Figure 2 a is the synthetic chemical reaction formula for preparing novel hydroxyl-modified covalent organic framework materials in Example 3 of this invention; Figure 2 b is the chemical reaction formula for the preparation of novel hydroxyl-modified covalent organic framework materials in Example 4 of this invention.

[0052] Figure 3a is the infrared spectrum of the covalent organic framework material and the hydroxyl-modified covalent organic framework material obtained in Examples 1 and 3 of this invention. The presence of imine bond characteristic signals in BPY-TFPT COF and the disappearance of the imine bond characteristic signal peak in QL-TFPT COF demonstrates the successful synthesis of the covalent organic framework material and the hydroxyl-modified covalent organic framework material. Figure 3 b is the carbon-13 solid-state NMR characterization of the covalent organic framework material and the hydroxyl-modified covalent organic framework material obtained in Examples 1 and 3 of this invention; the results show that the theoretical covalent organic framework material and the hydroxyl-modified covalent organic framework material were indeed obtained through the synthesis schemes of Examples 1 and 3. Figure 3 c is the photoelectron spectrum of the covalent organic framework material and the hydroxyl-modified covalent organic framework material obtained in Examples 1 and 3 of this invention. The figure shows the composition sp. 2 (C=C) hybrid carbon signal, sp 2 (CC) hybrid carbon signal and sp in pyridine and triazine ring 2 (C=N) hybrid carbon signal and sp(CN) hybrid carbon indicate the presence of pyridine and triazine structural units, while sp, representing imine, indicates the presence of these units. 2 The presence of (C=N) hybrid carbon and sp(CN) hybrid carbon indicates the successful synthesis of a covalent organic framework material, representing the sp(CN) hybrid carbon of quinoline. 2 (C=N) hybrid carbon and sp(CN) hybrid carbon, as well as sp (representing alcohols) 3 The presence of (CO) hybrid carbon indicates the successful synthesis of hydroxyl-modified covalent organic framework materials.

[0053] Figure 4 a is the infrared spectrum of the covalent organic framework material and the hydroxyl-modified covalent organic framework material obtained in Examples 2 and 4 of this invention. The presence of imine bond characteristic signals in BPY-TFPB COF and the disappearance of the imine bond characteristic signal peak in QL-TFPB COF in the figure proves the successful synthesis of the covalent organic framework material and the hydroxyl-modified covalent organic framework material. Figure 4 b is the carbon-13 solid-state NMR characterization of the covalent organic framework material and the hydroxyl-modified covalent organic framework material obtained in Examples 2 and 4 of this invention; the results show that the theoretical covalent organic framework material and the hydroxyl-modified covalent organic framework material were indeed obtained through the synthesis schemes of Examples 2 and 4; Figure 4 c is the photoelectron spectrum of the covalent organic framework material and the hydroxyl-modified covalent organic framework material obtained in Examples 2 and 4 of this invention. The figure shows the composition sp. 2 (C=C) hybrid carbon signal, sp 2 (CC) hybrid carbon signal and sp in pyridine 2 (C=N) hybrid carbon signal and sp(CN) hybrid carbon indicate the presence of pyridine structural units. Meanwhile, the sp(CN) signal, representing an imine, indicates the presence of these structural units. 2The presence of (C=N) hybrid carbon and sp(CN) hybrid carbon indicates the successful synthesis of a covalent organic framework material, representing the sp(CN) hybrid carbon of quinoline. 2 (C=N) hybrid carbon and sp(CN) hybrid carbon, as well as sp (representing alcohols) 3 The presence of (CO) hybrid carbon indicates the successful synthesis of hydroxyl-modified covalent organic framework materials.

[0054] Figure 5 These are powder diffraction patterns and crystal structure simulation diagrams of the covalent organic framework materials and hydroxyl-modified covalent organic framework materials obtained in Examples 1, 2, 3, and 4 of this invention. The results show that highly crystalline AA-stacking covalent organic framework materials and hydroxyl-modified covalent organic framework materials were obtained through the synthesis schemes of Examples 1, 2, 3, and 4.

[0055] Application Example: Photosynthesis of Hydrogen Peroxide

[0056] Ten milligrams of the covalent organic framework materials and hydroxyl-modified covalent organic framework materials obtained in Examples 1, 2, 3, and 4 were weighed and added to a photocatalytic bottle containing 10 ml of deionized water. A stir bar was added, and the mixture was sonicated for 15 minutes to ensure uniform dispersion of the materials in the water. Oxygen was then introduced into the system for 30 minutes. After aeration, the bottle opening was sealed with a rubber stopper and then sealed with a sealing film. A 300-watt xenon lamp was used as the light source, and a filter was added to obtain visible light >420 nm. After irradiation and stirring for 2 hours, the photocatalytic bottle was removed, and 1 ml of water was drawn from the system using a syringe. The residual photocatalyst was filtered out through a microporous membrane. A 1 mmol / L cerium sulfate solution was added to the filtered sample until a color change occurred. The mixture was then placed in the dark for 20 minutes. The absorbance of cerium sulfate at 316.5 nm in the mixed solution was measured using a UV-Vis absorption spectrometer. The detection of hydrogen peroxide involves reacting tetravalent cerium sulfate with the generated hydrogen peroxide. The tetravalent cerium ions are reduced by hydrogen peroxide to trivalent cerium ions. The absorbance of the mixed solution at 316.5 nm is detected by ultraviolet-visible absorption spectroscopy. The concentration of cerium sulfate in the mixed solution after the reaction is calculated by comparing it with a standard curve. Then, the amount of tetravalent cerium ions consumed is calculated, and finally, the concentration of photosynthetically synthesized hydrogen peroxide is obtained.

[0057] Figure 6 This is a comparison chart of the photosynthesis efficiency of hydrogen peroxide under pure water oxygen saturation conditions between the covalent organic framework materials and hydroxyl-modified covalent organic framework materials obtained in Examples 1, 2, 3, and 4 of this invention. Figure 6 It can be seen that the modification significantly improved the efficiency of hydrogen peroxide photosynthesis from covalent organic framework materials.

Claims

1. A method for preparing a novel hydroxyl-modified covalent organic framework material, characterized in that: Hydroxyl-modified covalent organic framework materials were obtained by polymerization using C3 symmetrical amino building units, 2,2'-bipyridine-5,5'-dicarboxaldehyde and acetone alcohol as reactants under the conditions of debner-Müller reaction. The structure of the C3 symmetric amino building block is shown in equation (1): ； The structure of the hydroxyl-modified covalent organic framework material is shown in equation (2) below: 。 2. The preparation method according to claim 1, characterized in that... Includes the following steps: C3 symmetric amino building blocks and 2,2'-bipyridine-5,5'-dicarboxaldehyde were added to a Shrek tube. Trimethylbenzene, dioxane, acetic acid solution and acetone alcohol were added to prepare a reaction mixture. Then, three freeze-degassing cycles were performed. The degassed Shrek tube was placed in a pure oxygen environment for reaction. After the reaction was completed, the hydroxyl-modified covalent organic framework material was obtained through post-treatment and purification.

3. The preparation method according to claim 2, characterized in that: The molar ratio of the C3 symmetrical amino building unit, 2,2'-bipyridine-5,5'-dicarboxaldehyde, and acetone alcohol is 2:3:

9.

4. The preparation method according to claim 2, characterized in that: The volume ratio of mesitylene, dioxane and acetic acid solution is (14~15):(5~6):

1.

5. The preparation method according to claim 4, characterized in that: The concentration of the acetic acid solution is 17.5 mol / L.

6. The preparation method according to claim 2, characterized in that: The reaction temperature was 120℃ and the reaction time was 3 days.

7. The preparation method according to claim 2, characterized in that: The post-processing and purification consisted of filtration followed by washing with methanol, ethyl acetate, and n-hexane, and finally Soxhlet extraction using methanol, ethyl acetate, and n-hexane as solvents.

8. A novel hydroxyl-modified covalent organic framework material, prepared according to any one of the preparation methods in claims 1-7.

9. The application of the novel hydroxyl-modified covalent organic framework material of claim 8 as a photocatalyst in the photocatalytic synthesis of hydrogen peroxide.

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