Heteroporous covalent organic framework materials, methods of preparation and use in photosynthesis of hydrogen peroxide

Abstract

This invention relates to heteroporous covalent organic framework materials, their preparation methods, and their application in the photosynthesis of hydrogen peroxide, belonging to the fields of organic framework materials technology and photocatalytic functional materials. This invention provides novel heteroporous covalent organic framework materials with fewer heterocyclic rings, while simultaneously solving the yield problem in the synthesis of hydrogen peroxide. The structural unit of the first heteroporous covalent organic framework material belongs to the hexagonal crystal system, space group P-62m, with cell parameters: a=39.3049Å, b=39.3049Å, c=3.4595Å; α=90°, β=90°, γ=120°. The structural unit of the second heteroporous covalent organic framework material belongs to the monoclinic crystal system, space group C2, with cell parameters: a=67.4524Å, b=38.0374Å, c=4.156Å; α=90°, β=90°, γ=90°. Due to its unique material structure, it can be used as a photocatalyst to directly carry out gas-liquid catalytic reactions under visible light. The yield of its reduction product, hydrogen peroxide, is 4658.59 μmol·g⁻¹. ‑1 h ‑1 The yield of hydrogen peroxide in structure 2 was 1112.11 μmol·g. ‑1 h ‑1 .

Description

Technical Field

[0001] This invention belongs to the fields of organic framework materials technology and photocatalytic functional materials, specifically involving two heteroporous covalent organic framework materials and their preparation methods, and using them as photocatalysts to achieve photocatalytic synthesis of hydrogen peroxide from water and oxygen. Background Technology

[0002] With rapid economic development and a continuously increasing population, human society's dependence on energy is growing daily. The rapid depletion of traditional fossil fuels has triggered a severe energy crisis, leading to serious environmental pollution and ecological damage. Hydrogen peroxide (H2O2), as a strong oxidant, is widely used in chemical synthesis, pharmaceuticals, medical disinfection, and environmental treatment, and is a high-value green chemical raw material. Currently, the mainstream H2O2 production process worldwide is based on the anthraquinone oxidation method. This method involves complex synthesis steps, high costs, hazardous production processes, and high energy consumption, while also causing some environmental pollution. Therefore, developing new green, environmentally friendly, low-cost, and low-energy-consumption H2O2 preparation technologies has significant economic and social value.

[0003] Traditional H2O2 synthesis processes often involve large amounts of organic solvents and the use of precious metals, among other drawbacks. Therefore, seeking more environmentally friendly, green, and recyclable methods is urgent. Solar energy is considered a clean and efficient energy source. Converting solar energy into chemical energy is a highly promising approach. Semiconductor photocatalytic synthesis of H2O2 using water and oxygen as raw materials offers advantages such as simple synthesis and low cost, making it a green and environmentally friendly H2O2 production technology. This reaction utilizes abundant solar energy as an energy source for catalytic reaction, exhibiting high product selectivity and producing no other pollutants, thus attracting significant attention and being considered a disruptive H2O2 production technology. However, the current H2O2 production efficiency of this technology remains relatively low, and it is still some distance from practical application. The key to this technology lies in developing highly efficient and stable photocatalysts. Common H2O2 synthesis photocatalysts include metal oxides, metal-organic frameworks, carbon nitride, organic porous materials, and covalent organic frameworks (COFs). COFs, a novel type of covalently linked organic crystalline framework material, possess multiple advantages in photocatalysis: their regular one-dimensional pore structure and large specific surface area facilitate molecular mass transfer reactions and rapid conduction of photogenerated charge carriers; their diverse synthetic building blocks and polymerization reactions make their molecular and pore structures easily modifiable, exhibiting strong tailorability; their band structure and optical properties are easily tunable; and they possess abundant organic units and bonds, enabling post-modification through specific reactions. Based on these advantages, COFs are widely used in photocatalytic water splitting for hydrogen production, CO2 reduction, and H2O2 synthesis, becoming one of the most popular catalysts in the current photocatalysis field.

[0004] No existing technology has proposed using 5'-(4-formylphenyl)-[1,1':3',1” terphenyl]-3,4”,5-tricarbonyl aldehyde and 4'-(bis(4-formylphenyl)amino)-[1,1'-biphenyl]-3,5-dialdehyde to synthesize heteroporous covalent organic framework materials. Summary of the Invention

[0005] The technical problem to be solved by this invention is:

[0006] The purpose of this invention is to provide two heteroporous covalent organic framework materials and their preparation methods, as well as their application in photocatalytic synthesis of hydrogen peroxide. It provides a novel heteroporous covalent organic framework material with fewer heterocyclic rings, while also addressing the issue that the materials themselves can be used as photocatalysts for gas-liquid photocatalytic reactions to reduce water and oxygen to hydrogen peroxide, resulting in a high yield of hydrogen peroxide.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0008] This invention provides two covalent organic framework materials. The structural unit of the first heteroporous covalent organic framework material belongs to the hexagonal crystal system P-62m space group, with unit cell parameters a=39.3049Å, b=39.3049Å, c=3.4595Å; α=90°, β=90°, γ=120°.

[0009] The structural unit of the second type of heteroporous covalent organic framework material belongs to the monoclinic C2 space group, with cell parameters a=67.4524Å, b=38.0374Å, c=4.156Å; α=90°, β=90°, γ=90°.

[0010] The method for preparing the first heteroporous covalent organic framework material of the present invention is characterized by comprising the following steps:

[0011] (1) 5'-(4-formylphenyl)-[1,1':3',1” terphenyl]-3,4”,5-tricarbonyl aldehyde, p-phenylenediamine, o-dichlorobenzene, and 1,4-dioxane were added sequentially into a Pyrex tube. After sonication for 3 to 4 hours, an aqueous acetic acid solution was added, and three liquid nitrogen freezing degassing operations were performed to achieve a vacuum oxygen-free condition for the reaction system.

[0012] (2) After the Pyrex tubes that have undergone degassing are naturally thawed, they are placed in an oven and heated at 100-170°C for reaction. After 72-120 hours, the oven is turned off and the tubes are allowed to cool naturally to room temperature.

[0013] (3) Filter the crude product obtained in step (2) and wash it repeatedly with N,N-dimethylformamide and ethanol until the filtrate is colorless. Solvent exchange is performed using methanol and acetone respectively, and the solvent is evaporated in a vacuum drying oven at 100-150℃ for 48-72 hours to obtain a yellow-green powdery covalent organic framework material.

[0014] In step (1), the molar ratio of 5'-(4-formylphenyl)-[1,1':3',1” terphenyl]-3,4”,5-tricarbonyl aldehyde and p-phenylenediamine is 1:2, and the total mass of the two does not exceed 30 mg.

[0015] In step (1), take mesitylene and 1,4-dioxane in a molar ratio of 1:2 to 2:1 into a tube, and the total volume of the two shall not exceed 4 mL.

[0016] The concentration of acetic acid in step (1) is 3–6 mol / L. -1 The volume of acetic acid added is 0.2 to 0.5 mL.

[0017] The preparation method of the second type of porous covalent organic framework material of the present invention includes the following steps:

[0018] (1) 4'-(bis(4-formylphenyl)amino)-[1,1'-biphenyl]-3,5-dialdehyde, p-phenylenediamine, o-dichlorobenzene and DMA were added sequentially into a Pyrex tube. After sonication for 3 to 4 hours, an aqueous acetic acid solution was added, and three liquid nitrogen freezing degassing operations were performed to achieve a vacuum oxygen-free condition for the reaction system.

[0019] (2) After the Pyrex tubes that have undergone degassing are naturally thawed, they are placed in an oven and heated at 100-170°C for reaction. After 72-120 hours, the oven is turned off and the tubes are allowed to cool naturally to room temperature.

[0020] (3) Filter the crude product obtained in step (2) and wash it repeatedly with N,N-dimethylformamide and ethanol until the filtrate is colorless. Solvent exchange is performed using methanol and acetone respectively, and the solvent is evaporated in a vacuum drying oven at 100-150℃ for 48-72 hours to obtain a yellow powdery covalent organic framework material.

[0021] In step (1), the molar ratio of 4'-(bis(4-formylphenyl)amino)-[1,1'-biphenyl]-3,5-dialdehyde and p-phenylenediamine is 1:2, and the total mass of the two does not exceed 30 mg.

[0022] In step (1), o-dichlorobenzene and DMA with a molar ratio of 1:2 to 2:1 are placed in a tube, and the total volume of the two shall not exceed 4 mL.

[0023] The concentration of acetic acid in step (1) is 3–9 mol / L. -1 The volume of acetic acid added is 0.2 to 0.5 mL.

[0024] The beneficial effects of this invention are:

[0025] This invention employs a solvothermal method to successfully synthesize two novel heteroporous covalent organic framework materials using 5'-(4-formylphenyl)-[1,1':3',1” terphenyl]-3,4”,5-tricarbonyl aldehyde, 4'-(bis(4-formylphenyl)amino)-[1,1'-biphenyl]-3,5-dialdehyde, and p-phenylenediamine as raw materials. Compared to single-structure covalent organic framework materials, heteroporous covalent organic frameworks possess unique multi-segmented structures and diverse pore environments, while inheriting the common characteristics of single-pore covalent organic frameworks. Both materials themselves possess the potential to act as photocatalysts in gas-liquid photocatalytic reactions, reducing water and oxygen to hydrogen peroxide. Attached Figure Description

[0026] Figure 1 This is a synthesis route diagram of Embodiment 1 and Structure 1 of the present invention;

[0027] Figure 2 This is a synthesis route diagram for Embodiment 2 and Structure 2 of the present invention;

[0028] Figure 3 The XRD diffraction pattern of structure 1 of the present invention;

[0029] Figure 4 The XRD diffraction pattern of structure 2 of the present invention;

[0030] Figure 5 The photocatalytic performance of gas-liquid hydrogen peroxide for structures 1 and 2 of this invention is shown in the diagram.

[0031] Figure 6 The attached diagram shows the nitrogen adsorption-desorption process of structure 1 of the present invention;

[0032] Figure 7 The attached diagram shows the nitrogen adsorption-desorption process of structure 2 of the present invention;

[0033] Figure 8 The Fourier infrared spectrum of structure 1 of the present invention;

[0034] Figure 9 The Fourier infrared spectrum of structure 2 of the present invention;

[0035] Figure 10 This is a SEM image of structure 1 of the present invention;

[0036] Figure 11 This is a SEM image of structure 2 of the present invention. Detailed Implementation

[0037] The following describes specific implementation methods and examples in conjunction with the appendix. Figure 1-11 The implementation of the present invention will be further described as follows:

[0038] Specific implementation method one: The first heteroporous covalent organic framework material has a structural unit belonging to the hexagonal crystal system P-62m space group, with unit cell parameters a=39.3049Å, b=39.3049Å, c=3.4595Å; α=90°, β=90°, γ=120°.

[0039] The preparation of the first type of porous covalent organic framework material in this embodiment is carried out according to the following steps:

[0040] (1) 5'-(4-formylphenyl)-[1,1':3',1” terphenyl]-3,4”,5-tricarbonyl aldehyde, p-phenylenediamine, o-dichlorobenzene, and 1,4-dioxane were added sequentially into a Pyrex tube (usually with a tube volume of 10 mL). After sonication for 3 hours, an aqueous acetic acid solution was added, and three liquid nitrogen freezing degassing operations were performed to achieve a vacuum oxygen-free condition for the reaction system.

[0041] (2) After the Pyrex tubes that have undergone degassing are naturally thawed, they are placed in an oven and heated to 100-170°C for reaction. After 72-100 hours, the oven is turned off and the tubes are allowed to cool naturally to room temperature.

[0042] (3) Filter the crude product obtained in step (2) and wash it repeatedly with N,N-dimethylformamide and ethanol until the filtrate is colorless. Solvent exchange is performed using methanol and acetone respectively, and the solvent is evaporated in a vacuum drying oven at 100-150℃ for 48-72 hours to obtain a yellow-green powdery covalent organic framework material.

[0043] In step (1), the molar ratio of 5'-(4-formylphenyl)-[1,1':3',1” terphenyl]-3,4”,5-tricarbonyl aldehyde and p-phenylenediamine is 1:2, and the total mass of the two does not exceed 30 mg.

[0044] In step (1), take trimethylbenzene and 1,4-dioxane in a molar ratio of 1:2 into a tube, with a total volume of 2 to 4 mL.

[0045] The concentration of acetic acid in step (1) is 3–6 mol / L. -1 The volume of acetic acid added is 0.2 to 0.5 mL.

[0046] Specific implementation method two: The second type of heteroporous covalent organic framework material, the structural unit belongs to the monoclinic crystal system C2 space group, and the cell parameters are a=67.4524Å, b=38.0374Å, c=4.156Å; α=90°, β=90°, γ=90°.

[0047] The second method for preparing a porous covalent organic framework material is characterized by the following steps:

[0048] (1) 4'-(bis(4-formylphenyl)amino)-[1,1'-biphenyl]-3,5-dialdehyde, p-phenylenediamine, o-dichlorobenzene and DMA were added sequentially into a Pyrex tube. After sonication for 3 hours, an aqueous acetic acid solution was added, and liquid nitrogen freezing degassing was performed three times to achieve a vacuum oxygen-free condition for the reaction system.

[0049] (2) After the Pyrex tubes that have undergone degassing are naturally thawed, they are placed in an oven and heated to 100-170°C for reaction. After 72-100 hours, the oven is turned off and the tubes are allowed to cool naturally to room temperature.

[0050] (3) Filter the crude product obtained in step (2) and wash it repeatedly with N,N-dimethylformamide and ethanol until the filtrate is colorless. Solvent exchange is performed using methanol and acetone respectively, and the solvent is evaporated in a vacuum drying oven at 100-150℃ for 48-72 hours to obtain a yellow powdery covalent organic framework material.

[0051] In step (1), the molar ratio of 4'-(bis(4-formylphenyl)amino)-[1,1'-biphenyl]-3,5-dialdehyde and p-phenylenediamine is 1:2, and the total mass of the two does not exceed 30 mg.

[0052] In step (1), o-dichlorobenzene and DMA with a molar ratio of 1:2 to 2:1 are placed in a tube, and the total volume of the two does not exceed 2 to 4 mL.

[0053] The concentration of acetic acid in step (1) is 3–9 mol / L. -1 The volume of acetic acid added is 0.2 to 0.5 mL.

[0054] The present invention is described in more detail in the following embodiments, but these embodiments do not constitute a limitation on the present invention. Specific embodiments are as follows:

[0055] Example 1: The preparation method of the first heteroporous covalent organic framework material is as follows:

[0056] (1) 0.01309 g of 5'-(4-formylphenyl)-[1,1':3',1” terphenyl]-3,4”,5-tricarbonyl aldehyde, 0.00798 g of p-phenylenediamine, 1.5 ml of mesitylene, and 1.5 ml of 1,4-dioxane were sequentially added to a Pyrex tube. After sonication for 3 hours, an aqueous acetic acid solution was added, and the reaction system was subjected to three liquid nitrogen cryogenic degassing operations to achieve a vacuum oxygen-free condition. After the Pyrex tube was naturally thawed, it was placed in an oven and heated at 100–170 °C for 72–120 hours. The oven was then turned off, and the tube was allowed to cool naturally to room temperature. The solid product was filtered and washed repeatedly with tetrahydrofuran and methanol until the filtrate was colorless. After solvent exchange with acetone, the solid powder was placed in a vacuum drying oven at 100 °C for 48 hours to evaporate the solvent, yielding 0.0209 g of covalent organic framework material.

[0057] The XRD patterns of the product and the XRD patterns of the product powder simulated by AA packing are as follows: Figure 3 As shown, the peaks at 2.75°, 4.75°, and 26.33° correspond to the 100, 110, and 201 crystal planes, respectively. The figure shows that the peak shapes of the experimentally measured spectrum perfectly match those of the simulated spectrum, indicating that the obtained product is indeed a covalent organic framework material.

[0058] Example 2: The preparation method of the second type of porous covalent organic framework material is as follows:

[0059] (2) Add 0.012075 g of 4'-(bis(4-formylphenyl)amino)-[1,1'-biphenyl]-3,5-dialdehyde, 0.00805 g of p-phenylenediamine, 0.5 ml of o-dichlorobenzene, and 1.5 ml of DMA sequentially to a Pyrex tube. After sonicating at room temperature for three hours, use a pipette to add 0.2–0.5 mL of a solution with a concentration of 3–9 mol / L. -1 An aqueous solution of acetic acid was prepared, and the reaction system underwent three liquid nitrogen cryogenic degassing operations to achieve a vacuum and oxygen-free condition. After natural thawing, the degassed Pyrex tubes were placed in an oven and heated to 100–170°C for 72–100 hours to allow for natural cooling to room temperature. The solid product was filtered and washed repeatedly with tetrahydrofuran and methanol until the filtrate was colorless. After solvent exchange with acetone, the solid powder was placed in a vacuum drying oven at 100°C for 48 hours to evaporate the solvent, yielding 0.0211 g of covalent organic framework material.

[0060] The XRD patterns of the product and the XRD patterns of the product powder simulated by AA packing are as follows: Figure 4As shown, the peaks at 2.63°, 4.77°, and 22.02° correspond to the 110, 020, and 221 crystal planes, respectively. The figure shows that the peak shapes of the experimentally measured spectrum and the simulated spectrum are in perfect agreement, indicating that the obtained product is a covalent organic framework material.

[0061] The following experiments were conducted to verify the beneficial effects of the present invention:

[0062] To investigate the photocatalytic synthesis of hydrogen peroxide using covalent organic framework materials, their visible light photocatalytic hydrogen peroxide synthesis performance was tested using the following method. The test procedure was as follows: 10 mg of a porous covalent organic framework was used as the photocatalyst, and deionized water was used as the reaction solution. The mixture was sonicated for 30 min to form a homogeneous suspension. The suspension was poured into a reactor, and oxygen was introduced for 30 min to purge the air from the reactor. A xenon lamp was then used as the light source, and the mixture was irradiated for 30 min. After irradiation, the resulting suspension was filtered through a 1 mL syringe with a filter tip to remove the catalyst, and the liquid was collected. 1 mL of the collected liquid was added to 1 mL of a 66.5 mg / mL potassium iodide solution and 0.5 mL of a 20.4 mg / mL potassium hydrogen phthalate solution. The mixture was thoroughly mixed and allowed to stand for 30 min. Analysis was then performed using a UV-Vis spectrophotometer. Figure 5 As shown, the yield of hydrogen peroxide synthesized under visible light irradiation can reach 4658.59 μmol·g. -1 h -1 Structure 2 can reach 1112.11 μmol·g -1 h -1 .like Figure 6 , 7 The figures shown are for nitrogen adsorption and desorption of structures 1 and 2, respectively. Isotherm data were obtained through N2 adsorption-desorption experiments at 77 K, and the adsorption characteristics and pore structures of the two COFs materials were analyzed based on these data. Both COFs exhibited typical type II reversible adsorption isotherm characteristics, indicating that their pore structure is mainly microporous and exhibits multilayer adsorption behavior. Based on the Brunauer-Emmett-Teller (BET) theoretical model, the specific surface area of ​​structure 1 was calculated to be 1530.6432 m². 2 g -1 The specific surface area of ​​structure 2 is 618.3520 m². 2 g -1 .like Figure 8 , 9 The figures show the Fourier transform infrared spectra of structures 1 and 2, respectively. It can be seen from the figures that the aldehyde and amino peaks of the monomers have disappeared, and vibrational absorption peaks of imine bonds appear in the synthesized COF, confirming the preliminary synthesis of this material. To investigate the macroscopic morphology of the two COFs, SEM analysis was performed. Figure 10 , 11 The images are SEM images of structure 1 and structure 2, respectively. Figure 10 The structure within it consists of regular particles. Figure 11 They exhibit a spiral, rod-like structure, and these particles have an uneven, porous surface.

Claims

1. A porous covalent organic framework material, characterized in that... The structural unit of the aforementioned heteroporous covalent organic framework material belongs to the hexagonal crystal system, space group P-62m, with cell parameters of a=39.3049Å, b=39.3049Å, c=3.4595Å; α=90°, β=90°, γ=120°. Its repeating chemical structure unit is shown in Structure 1. Structure 1 2. A heteroporous covalent organic framework material, characterized in that the structural unit of the heteroporous covalent organic framework material belongs to the monoclinic crystal system C2 space group, with cell parameters of: a=67.4524Å, b=38.0374Å, c=4.156Å; α=90°, β=90°, γ=90°, and its chemical repeating unit is shown in Structure 2: Structure 2 3. The method for preparing the heteroporous covalent organic framework material according to claim 1, characterized in that, The method includes the following steps: (1) 5'-(4-formylphenyl)-[1,1':3',1” terphenyl]-3,4”,5-tricarbonyl aldehyde, p-phenylenediamine, mesitylene, and 1,4-dioxane were added sequentially into a Pyrex tube. After sonication for 3-4 hours, an aqueous acetic acid solution was added, and three liquid nitrogen freezing degassing operations were performed to achieve a vacuum oxygen-free condition in the reaction system inside the Pyrex tube. (2) After the Pyrex tubes that have undergone degassing are naturally thawed, they are placed in an oven and heated at 100-170°C for reaction. After 72-120 hours, the oven is turned off and the tubes are allowed to cool naturally to room temperature to obtain the crude product. (3) Filter the crude product obtained in step (2) and wash it repeatedly with N,N-dimethylformamide and ethanol until the filtrate is colorless. Then, use methanol and acetone for solvent exchange, and keep it in a vacuum drying oven at 100-150℃ for 24-72 hours to evaporate the solvent, and obtain a yellow-green powdery heteroporous covalent organic framework material.

4. The method for preparing the heteroporous covalent organic framework material according to claim 3, characterized in that, Step (1) Weigh out the molar ratio of 5'-(4-formylphenyl)-[1,1':3',1” terphenyl]-3,4”,5-tricarbonyl aldehyde and p-phenylenediamine. The ratio is 1:2, and the total mass of the two does not exceed 30mg.

5. The method for preparing the heteroporous covalent organic framework material according to claim 4, characterized in that, In step (1) Take mesitylene and 1,4-dioxane in a molar ratio of 1:2 to 2:1 in a Pyrex tube as solvents, and the total volume of the two should not exceed 4 mL.

6. The method for preparing the heteroporous covalent organic framework material according to claim 5, characterized in that, The concentration of the substance of amount of acetic acid in step (1) is 3-6 mol / L -1 The volume of acetic acid added is 0.2-0.5 mL.

7. The method for preparing the heteroporous covalent organic framework material according to claim 2, characterized in that, The method includes the following steps: (1) 4'-(bis(4-formylphenyl)amino)-[1,1'-biphenyl]-3,5-dialdehyde, p-phenylenediamine, o-dichlorobenzene and DMA were added sequentially into a Pyrex tube. After sonication for 3 to 4 hours, an aqueous acetic acid solution was added, and three liquid nitrogen freezing degassing operations were performed to achieve a vacuum oxygen-free condition for the reaction system. (2) After the Pyrex tubes that have undergone degassing are naturally thawed, they are placed in an oven and heated at 100-170°C for reaction. After 72-120 hours, the oven is turned off and the tubes are allowed to cool naturally to room temperature to obtain the crude product. (3) Filter the crude product obtained in step (2) and wash it repeatedly with N,N-dimethylformamide and ethanol until the filtrate is colorless. Then, use methanol and acetone for solvent exchange and keep it in a vacuum drying oven at 100-150℃ for 24-72 hours to evaporate the solvent, and obtain a yellow powdery heteroporous covalent organic framework material.

8. The method for preparing the heteroporous covalent organic framework material according to claim 7, characterized in that, In step (1), weigh 4'-(bis(4-formylphenyl)amino)-[1,1'-biphenyl]-3,5-dialdehyde and p-phenylenediamine in a molar ratio of 1:2, with a total mass not exceeding 30 mg; take o-dichlorobenzene and DMA in a molar ratio of 1:2 to 2:1 as solvents in a Pyrex tube, with a total volume not exceeding 4 mL.

9. The method for preparing the heteroporous covalent organic framework material according to claim 8, characterized in that, The concentration by amount of substance of acetic acid in step (1) is 3 to 9 mol L -1 The volume of acetic acid added is 0.2 to 0.5 mL.

10. The application of the heteroporous covalent organic framework material as described in claim 1 or 2 in the photosynthesis of hydrogen peroxide, characterized in that, The application of the heteroporous covalent organic framework material in the photosynthesis of hydrogen peroxide involves using the covalent organic framework material as a photocatalyst to perform a gas-liquid photocatalytic reaction, reducing water and oxygen to hydrogen peroxide.

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