Preparation of covalent organic framework material containing methyl and thiophene and application of covalent organic framework material in production of hydrogen peroxide

Abstract

The invention relates to preparation of a covalent organic framework material (COF) containing methyl and thiophene and application of the covalent organic framework material in production of hydrogen peroxide. Two thienyl covalent organic framework materials are prepared respectively, and the problem that the yield of hydrogen peroxide produced through photocatalysis of an existing covalent organic framework material is not high is solved. A solvothermal method is adopted for preparation, the preparation process is simple and efficient, the solvent consumption is low, the method is green and environmentally friendly, the yield is high, the problem that the energy utilization efficiency is too low due to mutual compounding of photon-generated carriers and electrons in the photocatalysis process is solved, and the efficiency of photocatalytic production of hydrogen peroxide is effectively improved. The BTTPa-2COF is applied to photocatalytic production of hydrogen peroxide, experimental results show that the BTTPa-2COF has excellent performance of photocatalytic production of hydrogen peroxide, and the performance of hydrogen peroxide production can reach 3680 [mu] molg <-1 > h <-1 > under visible light irradiation.

Description

Technical Field

[0001] The present invention relates to the field of photocatalytic production of hydrogen peroxide. Background Art

[0002] As a versatile chemical, hydrogen peroxide (H2O2) shows great application potential in the fields of chemical industry, medicine, energy, and environmental protection. However, currently, more than 98% of the global H2O2 is still synthesized by the anthraquinone process, which is energy-consuming and highly polluting. In contrast, photocatalytic technology, with its sustainable, safe, and green characteristics, has become an ideal alternative for the production of H2O2. Although photocatalytic technology is limited by problems such as high electron-hole pair recombination rate, low visible light utilization rate, and poor product selectivity, its development prospect is still broad.

[0003] Photocatalytic technology uses solar energy as the driving energy, which can not only reduce production costs but also reduce environmental pollution. With the increasing global demand for renewable energy, the development of photocatalytic technology is particularly important. Research shows that by optimizing the design of photocatalysts and improving the structure of photocatalytic systems, the production efficiency of H2O2 can be significantly improved. For example, strategies such as constructing a spontaneous system without sacrificial agents, a gas-liquid-solid three-phase system, and inhibiting the decomposition of H2O2 are all effective ways to improve photocatalytic efficiency. In addition, solar-driven photocatalytic technology plays a crucial role in solving energy crises and environmental problems. With the gradual depletion of fossil fuel resources and the increasing severity of environmental pollution problems, finding clean and renewable energy alternatives has become an urgent task. Photocatalytic technology can not only directly convert solar energy into chemical energy but also play a great role in the field of environmental protection, such as using the H2O2 generated by photocatalysis for in-situ disinfection and degradation of pollutants. The multifunctional application of H2O2 and the development of its green production technology, especially the progress of photocatalytic technology, are of great significance for promoting sustainable development. In the future, with continuous technological breakthroughs and innovations, photocatalytic technology is expected to play a more crucial role in solving energy crises and environmental problems and contribute to the sustainable development of human society.

[0004] Covalent Organic Frameworks (COFs) are a class of porous crystalline materials composed of light elements (such as carbon, hydrogen, boron, oxygen, nitrogen, and silicon, etc.) connected by strong covalent bonds. Since they were first reported in 2005, COFs have shown great application potential in multiple fields due to their unique structures and properties, especially in the field of photocatalysis. With their high specific surface area, tunable structures, and excellent optoelectronic properties, COFs exhibit great application potential in the field of photocatalysis. Through rational design and functional modification, COFs can significantly improve the efficiency and selectivity of photocatalytic reactions, providing new solutions for clean energy development, environmental pollution treatment, and green chemical synthesis. Although there are still some challenges at present, with the in-depth research, COFs materials are expected to become revolutionary materials in the field of photocatalysis. Covalent organic framework materials containing methyl and thiophene can not only reduce the recombination rate of photo-generated charges and holes, but also enhance the electron transport efficiency and provide catalytic sites. COFs can convert water and oxygen into H2O2 through photocatalytic reactions, providing an efficient and environmentally friendly method for the green synthesis of H2O2. Summary of the Invention

[0005] The object of the present invention is to solve the problem of low yield of hydrogen peroxide produced by photocatalysis of existing covalent organic framework materials, and a covalent organic framework material containing methyl and thiophene and its application in photocatalytic production of hydrogen peroxide are synthesized.

[0006] The preparation method of the covalent organic framework material of the present invention is completed according to the following steps:

[0007] Step 1: Preparation of BTTPa-2 COF: Add benzothieno[3,2-b][1,4]dithiophene-2,5,8-tricarbaldehyde and 2,5-dimethyl-p-phenylenediamine into a heat-resistant glass tube, and use a pipette to measure o-dichlorobenzene and n-butanol into the heat-resistant glass tube respectively. Ultrasonically treat for 1 h to ensure uniform dispersion. Then add an acetic acid aqueous solution to the system and immediately perform three freeze-thaw cycle degassing operations in a liquid nitrogen bath. After sealing, place the heat-resistant glass tube in an oven at 120 °C and heat for 72 h. After cooling to room temperature, wash the product with a large amount of HTF (tetrahydrofuran) and ethanol, and dry to obtain BTTPa-2 COF.

[0008] Step 2. Preparation of BTTPa COF: Add benzothieno[3,2-b]benzothiophene-2,5,8-tricarbaldehyde and p-phenylenediamine into a heat-resistant glass tube, and use a pipette to measure o-dichlorobenzene and n-butanol into the heat-resistant glass tube respectively. Perform ultrasonic treatment for 1 h to ensure uniform dispersion. Subsequently, add an acetic acid aqueous solution to the system and immediately perform three freeze-thaw cycle degassing operations in a liquid nitrogen bath. After sealing, place the heat-resistant glass tube in an oven and heat it at 120 °C for 72 h. After cooling to room temperature, wash the product with a large amount of HTF and ethanol, and dry it to obtain BTTPa COF.

[0009] The masses of benzothieno[3,2-b]benzothiophene-2,5,8-tricarbaldehyde and 2,5-dimethyl-p-phenylenediamine described in Step 1 are 19.8 mg and 12.2 mg respectively;

[0010] The molar ratio of benzothieno[3,2-b]benzothiophene-2,5,8-tricarbaldehyde to 2,5-dimethyl-p-phenylenediamine described in Step 1 is 2:3;

[0011] The masses of benzothieno[3,2-b]benzothiophene-2,5,8-tricarbaldehyde and p-phenylenediamine described in Step 2 are 19.8 mg and 9.7 mg respectively;

[0012] The molar ratio of benzothieno[3,2-b]benzothiophene-2,5,8-tricarbaldehyde to p-phenylenediamine described in Step 2 is 2:3;

[0013] The volume ratio of o-dichlorobenzene to n-butanol described in Step 1 is 1:1;

[0014] The volume ratio of o-dichlorobenzene to n-butanol described in Step 2 is 1:1;

[0015] The concentration of the acetic acid aqueous solution described in Step 1 is 6 mol / L;

[0016] The concentration of the acetic acid aqueous solution described in Step 2 is 6 mol / L;

[0017] The volume of the added acetic acid aqueous solution described in Step 1 is 1 mL;

[0018] The volume of the added acetic acid aqueous solution described in Step 2 is 1 mL;

[0019] Advantages of the present invention: Two COFs are prepared by the solvothermal method in the present invention. Among them, the photocatalytic hydrogen peroxide performance of BTTPa-2COF prepared from benzo[1,2-B:3,4-B':5,6-B']terthiophene-2,5,8-tricarbaldehyde and 2,5-dimethyl-p-phenylenediamine can reach 3680 μmol g -1 h -1 , this material has good visible light absorption ability, and its unique thiophene group containing S sites can improve the adsorption ability of reactants, improve the redox power, and effectively separate and transfer photo-generated carriers. The methyl groups on the aryl near the imine bond can adjust the electronic structure and expand the visible light absorption. Therefore, it is 1.71 times higher than that without methyl groups. Description of the Drawings

[0020] Figure 1 is the structural diagram of BTTPa-2 COF.

[0021] Figure 2 is the structural diagram of BTTPa COF.

[0022] Figure 3 are the XRD spectrum and simulated spectrum of BTTPa-2 COF.

[0023] Figure 4 are the XRD spectrum and simulated spectrum of BTTPa COF.

[0024] Figure 5 are the FT-TR spectra of BTTPa-2 COF and BTTPa COF.

[0025] Figure 6 are the hydrogen peroxide yield spectra of BTTPa-2 COF and BTTPa COF changing with time. Detailed Embodiments

[0026] To make the objectives, technical solutions and advantages of the present invention clearer and easier to understand, the present invention will be further described in detail below with reference to the embodiments. The specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0027] Example 1: The preparation of the two COF materials in this embodiment is completed according to the following steps:

[0028] Preparation of BTTPa-2 COF: Add benzo[1,2-b:3,4-b':5,6-b'']trithiophene-2,5,8-tricarbaldehyde and 2,5-dimethyl-p-phenylenediamine into a heat-resistant glass tube. Then, use a pipette to measure o-dichlorobenzene and n-butanol into the heat-resistant glass tube respectively. Ultrasonically treat for 1 h to ensure uniform dispersion. Subsequently, add an acetic acid aqueous solution to the system and immediately perform three freeze-thaw cycle degassing operations in a liquid nitrogen bath. After sealing, place the heat-resistant glass tube in an oven and heat at 120 °C for 72 h. After cooling to room temperature, wash the product with a large amount of HTF and ethanol, and dry to obtain BTTPa-2 COF.

[0029] Preparation of BTTPa COF: Add benzo[1,2-b:3,4-b':5,6-b'']trithiophene-2,5,8-tricarbaldehyde and p-phenylenediamine into a heat-resistant glass tube. Then, use a pipette to measure o-dichlorobenzene and n-butanol into the heat-resistant glass tube respectively. Ultrasonically treat for 1 h to ensure uniform dispersion. Subsequently, add an acetic acid aqueous solution to the system and immediately perform three freeze-thaw cycle degassing operations in a liquid nitrogen bath. After sealing, place the heat-resistant glass tube in an oven and heat at 120 °C for 72 h. After cooling to room temperature, wash the product with a large amount of HTF and ethanol, and dry to obtain BTTPa COF.

[0030] The following experiments were carried out to verify the beneficial effects of the present invention: To investigate the photocatalytic ability of BTTPa-2 COF and BTTPa COF materials, their visible-light photocatalytic performance was tested according to the following method. The test process is as follows: Take BTTPa-2 COF and BTTPa COF (5 mg) as photocatalysts respectively, and 50 ml of distilled water as the reaction solution. Ultrasonically treat for 30 min to form a uniform suspension. After pouring the suspension into the reactor, introduce oxygen for 30 min to exhaust the air in the reactor. Then, use a xenon lamp as the light source. Collect 1 ml of filtrate every ten minutes. Add 1 ml of (0.1 M) potassium iodide solution and 0.5 ml of (0.1 M) potassium hydrogen phthalate solution to 1 ml of the collected liquid to be tested after the reaction. After standing for half an hour, measure the absorbance of the solution with a UV-visible spectrophotometer, and substitute it into the hydrogen peroxide standard curve to obtain the hydrogen peroxide yield.

[0031] Figure 1 、 Figure 2 Structural diagrams of two kinds of COFs prepared in the implementation of the present invention, where Figure 1 is the structure of BTTPa-2 COF, Figure 2 is the structure of BTTPa COF. As shown in the figure, the benzotrithiophene structure is connected to two kinds of benzene rings through imine bonds respectively to form BTTPa-2 COF and BTTPa COF.

[0032] Figure 3 、 Figure 4XRD spectra of two COFs prepared in the implementation of the present invention, where 1 is the X-ray diffraction spectrum of the two COFs, and 2 is the peak position spectrum of the two COFs simulated by Material Studio. As shown in the figure, the peak positions of the two COFs are consistent with the peak positions of the COFs simulated by Material Studio, proving the successful preparation of the two materials.

[0033] Figure 5 FT-IR spectra of two COFs prepared in the implementation of the present invention, where 1 is the FT-IR spectrum of BTTPa-2 COF, and 2 is the FT-IR spectrum of BTTPa COF. As shown in the figure, the two COFs have strong absorption peaks near 1600 nm, indicating that a Schiff base reaction occurred between the two monomers, generating a C=N bond, proving the successful synthesis of the two COF materials.

[0034] Figure 6 Performance spectra of two COFs prepared in the implementation of the present invention for the production of hydrogen peroxide over time, where 1 is the performance spectrum of BTTPa-2 COF for the production of hydrogen peroxide over time, and 2 is the performance spectrum of BTTPa COF for the production of hydrogen peroxide over time. As shown in the figure, the hydrogen peroxide productivity of BTTPa-2 COF is 3680 μmol g -1 h -1 , and the hydrogen peroxide productivity of BTTPa COF is 2152 μmol g -1 h -1 , and the ratio of the two is 1.71:1.

Claims

1. A covalent organic framework material containing methyl and thiophene, characterized in that: The covalent organic framework material is BTTPa-2 COF, and the monomers for synthesizing the covalent organic framework are benzo[1,2-B:3,4-B':5,6-B']terthiophene-2,5,8-trialdehyde and 2,5-dimethyl-p-phenylenediamine.

2. The preparation of the BTTPa-2 COF material according to claim 1, characterized in that: Benzo[1,2-B:3,4-B':5,6-B']trithiophene-2,5,8-trialdehyde and 2,5-dimethyl-p-phenylenediamine were added to a heat-resistant glass tube, and o-dichlorobenzene and n-butanol were measured and added to the heat-resistant glass tube with a pipette. Ultrasonic treatment was performed for 1 hour to ensure uniform dispersion. Then, acetic acid aqueous solution was added to the system and immediately three freeze-thaw cycles were performed in a liquid nitrogen bath for degassing. After sealing, the heat-resistant glass tube was placed in an oven at 120°C and heated for 72 hours. After cooling to room temperature, the product was washed with a large amount of HTF and ethanol, and BTTPa-2 COF was obtained after drying.

3. The preparation of the BTTPa-2 COF material according to claim 2, characterized in that: The molar ratio of the benzo[1,2-B:3,4-B':5,6-B']terthiophene-2,5,8-trialdehyde to 2,5-dimethyl-p-phenylenediamine is 2:

3.

4. The preparation of the BTTPa-2 COF material according to claim 2, characterized in that: The volume ratio of o-dichlorobenzene to n-butanol is 1:

1.

5. The preparation of the BTTPa-2 COF material according to claim 2, characterized in that: The concentration of the acetic acid solution is 6 mol / L.

6. The preparation of the BTTPa-2 COF material according to claim 2, characterized in that: The volume of the acetic acid solution is 0.1 mL.

Images