Preparation and application of two covalent organic framework materials

Abstract

The present invention belongs to the field of covalent organic framework materials, and specifically relates to the preparation methods and uses of two covalent organic framework materials. The characteristic feature of the covalent organic framework materials is that their structural units belong to the hexagonal P3 space group, with unit cell parameters α = 90°, β = 90°, and γ = 120°. Due to the unique structure of the material, it can be used as a photocatalyst, directly undergoing a gas-liquid catalytic reaction under visible light drive, with the reduction product hydrogen peroxide having an average yield of 1200 μmol g per hour. ‑1 and 1800 μmol g ‑1 .

Description

Technical Field

[0001] The present invention belongs to the field of covalent organic framework materials, and in particular relates to the preparation of two covalent organic framework materials and their application in photocatalytic production of hydrogen peroxide. Background Art

[0002] With the continuous growth of fossil energy consumption, environmental pollution and energy shortages are becoming increasingly prominent. Green energy is a promising long-term alternative for sustainable development. H2O2, a green oxidant widely used in wastewater treatment, chemical industry, and energy storage, is recognized as one of the 100 most essential chemicals. However, the traditional anthraquinone method for producing H2O2 presents numerous challenges, including high energy consumption, which is particularly evident in industrial-scale operations. Due to its non-green production methods, H2O2's cleanliness is significantly compromised. Therefore, the development of eco-friendly H2O2 production methods is crucial. Since the first report of photocatalytic H2O production in 1972, photocatalysis has flourished. Its low energy consumption and environmental friendliness have led to its high adoption in biodiesel. Photochemical conversion of naturally abundant water and oxygen into H2O2 is the most efficient and green approach to obtaining it. The resulting synthetic fuel can also be stored and used as a fossil fuel alternative. To achieve the goal of green and sustainable photochemical H2O2 production, the search for low-cost photocatalysts with high solar energy conversion efficiency is crucial.

[0003] Traditional H2O2 synthesis processes are often accompanied by numerous drawbacks, including the use of large amounts of organic solvents and precious metals. Therefore, the search for 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 photocatalysts generate H2O2 through photosynthesis, without pollutant emissions. These advantages have attracted considerable attention for photocatalytic H2O2 synthesis, due to its environmental safety, high stability, and low cost. The key lies in the development of efficient photocatalysts. Covalent organic frameworks (COFs), as crystalline porous materials, are a classic class of structurally stable crystalline porous frameworks developed after MOFs. They are composed of two- or three-dimensional porous structures composed of organic molecules linked in an orderly fashion by strong covalent bonds (such as C=N, CN, and C=C). As crystalline porous structures, COFs possess outstanding surface area and gas adsorption capacity. Currently, COFs have become a new class of visible light-responsive catalysts. Summary of the Invention

[0004] The purpose of the present invention is to provide two methods for preparing covalent organic framework materials and their application in photocatalytic production of hydrogen peroxide.

[0005] The technical solution adopted in the present invention is:

[0006] Two covalent organic framework materials, characterized by structural units belonging to the hexagonal P3 space group, unit cell parameters α=90°, β=90°, γ=120°.

[0007] The first method for preparing a covalent organic framework material described above is characterized by comprising the following steps: (1) adding 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-formylphenyl)benzene, p-phenylenediamine, o-dichlorobenzene, and n-butanol sequentially into a Pyrex tube, adding an acetic acid aqueous solution after ultrasonication for 3 hours, and performing three liquid nitrogen freezing degassing operations to achieve vacuum and oxygen-free conditions in the reaction system; thawing the degassed Pyrex tube naturally and placing it in an oven heated at 100-170°C for reaction, closing the oven after 72-120 hours, and allowing it to cool naturally to room temperature.

[0008] The crude product obtained in step (1) is filtered and washed with N,N-dimethylformamide and ethanol several times until the filtrate is colorless. The solvent is exchanged with methanol and acetone respectively, and the solvent is evaporated in a vacuum drying oven at 100-150°C for 24-72 hours to obtain a reddish-brown powdered covalent organic framework material.

[0009] In step (1), the ratio of the amount of 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-formylphenyl)benzene and p-phenylenediamine weighed is 1:3.

[0010] In step (1), o-dichlorobenzene and n-butanol are placed in a tube at a molar ratio of 1:2 to 2:1.

[0011] The concentration of the acetic acid in step (1) is 3 to 6 mol L -1 The volume of acetic acid added is 0.2~0.5mL.

[0012] The second method for preparing a covalent organic framework material described above is characterized by comprising the following steps: (2) adding 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-formylphenyl)benzene, pyridinediamine, o-dichlorobenzene, and DMA to a Pyrex tube in sequence, adding an acetic acid aqueous solution after ultrasonication for 3 hours, and performing three liquid nitrogen freezing degassing operations to achieve vacuum and oxygen-free conditions in the reaction system; the degassed Pyrex tube is naturally thawed and placed in an oven to heat at 100-170°C for reaction, and the oven is closed after 72-120 hours to allow it to cool naturally to room temperature.

[0013] The crude product obtained in step (2) is filtered and washed with N,N-dimethylformamide and ethanol several times until the filtrate is colorless. The solvent is exchanged with methanol and acetone respectively, and the solvent is evaporated in a vacuum drying oven at 100-150°C for 24-72 hours to obtain a red powdery covalent organic framework material.

[0014] In step (2), the ratio of the amount of 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-formylphenyl)benzene and pyridinediamine is 1:3.

[0015] In step (2), o-dichlorobenzene and DMA are placed in a tube at a molar ratio of 1:2 to 2:1.

[0016] The concentration of the acetic acid in step (2) is 3 to 9 mol L -1 The volume of acetic acid added is 0.2~0.5mL.

[0017] Beneficial effects of the present invention:

[0018] The triazine rings in the two new COFs are fully conjugated structures, which can increase the migration rate of photogenerated electrons, shorten the migration time of photogenerated electrons, retain a large number of carriers, and effectively inhibit the recombination of photogenerated electrons and holes. Therefore, both materials themselves have the potential to act as photocatalysts for gas-liquid photocatalytic reactions, reducing water and oxygen to hydrogen peroxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The synthetic route of specific embodiment 1 of the present invention;

[0020] Figure 2 The synthetic route of specific embodiment 2 of the present invention;

[0021] Figure 3 The XRD diffraction pattern of specific embodiment 1 of the present invention;

[0022] Figure 4 The XRD diffraction pattern of specific embodiment 2 of the present invention;

[0023] Figure 5 Infrared spectrum of specific embodiment 1 of the present invention;

[0024] Figure 6 The infrared spectrum of the specific embodiment 2 of the present invention;

[0025] Figure 7 A comparison chart of the photocatalytic gas-liquid hydrogen peroxide performance of specific embodiments 1 and 2 of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further elaborated below in conjunction with the embodiments:

[0027] Two covalent organic framework materials, characterized by structural units belonging to the hexagonal P3 space group, unit cell parameters α=90°, β=90°, γ=120°.

[0028] The preparation methods of the two covalent organic framework materials described above are characterized by comprising the following steps:

[0029] (1) 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-formylphenyl)benzene, p-phenylenediamine, o-dichlorobenzene, and n-butanol were sequentially added to a Pyrex tube. After ultrasonication for 3 hours, an acetic acid aqueous solution was added, and three liquid nitrogen freezing and degassing operations were performed to achieve vacuum and oxygen-free conditions in the reaction system. The degassed Pyrex tube was naturally thawed and placed in an oven to heat at 100-170°C for reaction. After 72-120 hours, the oven was closed and the tube was naturally cooled to room temperature.

[0030] The crude product obtained in step (1) is filtered and washed with N,N-dimethylformamide and ethanol several times until the filtrate is colorless. The solvent is exchanged with methanol and acetone respectively, and the solvent is evaporated in a vacuum drying oven at 100-150°C for 24-72 hours to obtain a reddish-brown powdered covalent organic framework material.

[0031] In step (1), the ratio of the amount of 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-formylphenyl)benzene and p-phenylenediamine weighed is 1:3 to 1:5.

[0032] In step (1), o-dichlorobenzene and n-butanol are weighed in a tube at a molar ratio of 1:2 to 2:1.

[0033] The concentration of the acetic acid in step (1) is 3 to 6 mol L -1 The volume of acetic acid added is 0.2~0.5mL.

[0034] The second method for preparing the covalent organic framework material described above is characterized by comprising the following steps:

[0035] (2) 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-formylphenyl)benzene, pyridinediamine, o-dichlorobenzene, and DMA were sequentially added to a Pyrex tube. After ultrasonication for 3 hours, an acetic acid aqueous solution was added, and three liquid nitrogen freezing degassing operations were performed to achieve vacuum and oxygen-free conditions in the reaction system. The degassed Pyrex tube was naturally thawed and placed in an oven at 100-170°C for heating to react. After 72-120 hours, the oven was closed and allowed to cool naturally to room temperature.

[0036] The crude product obtained in step (2) is filtered and washed with N,N-dimethylformamide and ethanol several times until the filtrate is colorless. The solvent is exchanged with methanol and acetone respectively, and the solvent is evaporated in a vacuum drying oven at 100-150°C for 24-72 hours to obtain a red powdery covalent organic framework material.

[0037] In step (2), the ratio of the amount of 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-formylphenyl)benzene and pyridinediamine is 1:3.

[0038] In step (2), o-dichlorobenzene and DMA are placed in a tube at a molar ratio of 1:2 to 2:1.

[0039] The concentration of the acetic acid in step (2) is 3 to 9 mol L -1 The volume of acetic acid added is 0.2~0.5mL.

[0040] The present invention is described in more detail in the following examples, but the examples do not limit the present invention.

[0041] (1) 0.02618 g of 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-dialdehyde)benzene, 0.01596 g of p-phenylenediamine, 1.5 ml of o-dichlorobenzene, and 1.5 ml of n-butanol were added to a Pyrex tube in sequence. After three hours of ultrasound at room temperature, 0.2-0.5 ml of the substance was added using a pipette to a molar concentration of 3-6 mol L -1The reaction system was then subjected to three liquid nitrogen freeze-degassed operations to achieve vacuum and oxygen-free conditions. The degassed Pyrex tube was naturally thawed and placed in an oven heated at 120-150°C for reaction. After 72-120 hours, the oven was closed and the reaction was allowed to cool naturally to room temperature. The solid product was filtered and washed with tetrahydrofuran and methanol multiple times 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 a covalent organic framework material.

[0042] The XRD diffraction patterns of the product and the product powder XRD simulated by AA stacking are as follows: Figure 3 As shown in the figure, the peaks at 3.52°, 7.21°, and 26.36° correspond to the 100, 200, and 001 crystal planes, respectively. Figure 3 It can be seen that the peak shape of the experimental spectrum is completely consistent with that of the simulated spectrum, indicating that the obtained product is a covalent organic framework material. Figure 5 As shown in the figure, the product is -1 The C=O peak of the monomer disappears and the peak at 1638 cm -1 There is a strong absorption nearby, corresponding to C=N, indicating that a condensation reaction has occurred between the two monomers.

[0043] (2) 0.02618 g of 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-dialdehyde)benzene, 0.01611 g of pyridinediamine, 0.5 ml of o-dichlorobenzene, and 1.5 ml of DMA were added to a Pyrex tube in sequence. After ultrasonication at room temperature for three hours, 0.2 to 0.5 ml of the substance was added using a pipette to a molar concentration of 3 to 9 mol L -1 The reaction system was then subjected to three degassing operations using liquid nitrogen to achieve vacuum and oxygen-free conditions. The degassed Pyrex tube was naturally thawed and placed in an oven heated at 120-150°C for the reaction. After 72-120 hours, the oven was closed and the reaction was allowed to cool naturally to room temperature. The solid product was filtered and washed with tetrahydrofuran and methanol multiple times 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 a covalent organic framework material.

[0044] The XRD diffraction patterns of the product and the product powder XRD simulated by AA stacking are as follows: Figure 4 As shown in the figure, the peaks at 3.26°, 7.28°, and 26.83° correspond to the 100, 200, and 001 crystal planes, respectively. Figure 4 It can be seen that the peak shape of the experimental spectrum is completely consistent with that of the simulated spectrum, indicating that the obtained product is a covalent organic framework material. Figure 6As shown in the figure, the product is -1 The C=O peak of the monomer disappears and the peak at 1638 cm -1 There is a strong absorption nearby, corresponding to C=N, indicating that a condensation reaction has occurred between the two monomers.

[0045] The photocatalytic gas-liquid hydrogen peroxide performance test of its product is shown in the figure below: Figure 7 50 ml of water and 0.010 g of covalent organic framework material were ultrasonically homogenized and placed in a gas-liquid reactor. After continuous introduction of pure oxygen for a period of time, the light source was turned on for photocatalytic reaction. The average production of hydrogen peroxide was 1200 μmol g per hour. -1 and 1800 μmol g -1 .

Claims

1. A covalent organic framework material, wherein the chemical structure repeating unit of the covalent organic framework material is shown in structural formula 1 or structural formula 2, and the structural unit of the covalent organic framework material belongs to the hexagonal P3 space group, and the unit cell parameter α=90°, β=90°, γ=120°; 2. A covalent organic framework material according to claim 1, characterized in that The method for preparing the material shown in the structural formula 1 comprises the following steps: (1) adding 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-formylphenyl)benzene, p-phenylenediamine, o-dichlorobenzene and n-butanol into a Pyrex tube in sequence, adding acetic acid aqueous solution after ultrasonic treatment for 3 hours, and performing three liquid nitrogen freezing degassing operations to achieve vacuum oxygen-free conditions of the reaction system; thawing the degassed Pyrex tube naturally and placing it in an oven heated at 100-170°C for reaction, closing the oven after 72-120 hours, and naturally cooling to room temperature; filtering the crude product obtained in step (1), and washing it with N,N-dimethylformamide and ethanol for multiple times until the filtrate is colorless; using methanol and acetone for solvent exchange respectively, keeping the solution in a vacuum drying oven at 100-150°C for 24-72 hours to evaporate the solvent, thereby obtaining a red-brown powdery covalent organic framework material.

3. A covalent organic framework material according to claim 2, characterized in that, In step (1), the ratio of the amount of 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-formylphenyl)benzene and p-phenylenediamine weighed is 1:3 to 1:

5.

4. A covalent organic framework material according to claim 2, characterized in that In step (1), o-dichlorobenzene and n-butanol are placed in a tube at a molar ratio of 1:2 to 2:

1.

5. A covalent organic framework material according to claim 2, characterized in that, The concentration of the acetic acid in step (1) is 3 to 6 mol L -1 The volume of acetic acid added is 0.2~0.5mL.

6. A covalent organic framework material according to claim 1, characterized in that: The method for preparing the material shown in the structural formula 2 comprises the following steps: (2) adding 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-formylphenyl)benzene, pyridinediamine, o-dichlorobenzene and DMA into a Pyrex tube in sequence, adding acetic acid aqueous solution after ultrasonic treatment for 3 hours, and performing three liquid nitrogen freezing degassing operations to achieve vacuum and oxygen-free conditions of the reaction system; thawing the degassed Pyrex tube naturally and placing it in an oven heated at 100-170°C for reaction, closing the oven after 72-120 hours, and naturally cooling to room temperature; filtering the crude product obtained in step (2), and washing it with N,N-dimethylformamide and ethanol several times until the filtrate is colorless; using methanol and acetone for solvent exchange respectively, keeping the solvent in a vacuum drying oven at 100-150°C for 24-72 hours to evaporate the solvent, and obtaining a red powdery covalent organic framework material.

7. A covalent organic framework material according to claim 6, characterized in that: In step (2), the ratio of the amount of 1,3,5-triazine-2,4,6-tris(4'-hydroxy-3',5'-formylphenyl)benzene and pyridinediamine weighed is 1:

3.

8. A covalent organic framework material according to claim 6, characterized in that: In step (2), o-dichlorobenzene and DMA are placed in a tube at a molar ratio of 1:2 to 2:

1.

9. A covalent organic framework material according to claim 6, characterized in that: The concentration of the acetic acid in step (2) is 3 to 9 mol L -1 The volume of acetic acid added is 0.2~0.5mL.

10. Use of the covalent organic framework material according to claim 1, wherein the covalent organic framework material is used as a photocatalyst to carry out a gas-liquid photocatalytic reaction to reduce water and oxygen to hydrogen peroxide.

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