Preparation of sulfydryl-containing two-dimensional covalent organic framework and photocatalytic full-water-splitting performance application of sulfydryl-containing two-dimensional covalent organic framework

Abstract

The invention relates to preparation of a sulfydryl-containing covalent organic framework (COF) and application of the sulfydryl-containing covalent organic framework in photocatalytic full water splitting performance. The invention provides a sulfydryl-containing covalent organic framework material (TFDBD-COF), and aims to solve the problems of low photocatalytic full water splitting efficiency and low visible light utilization rate of the existing covalent organic framework material. The method comprises the following steps: 1, preparing a TFPa-COF material; and 2, preparing the TFDBD-COF material. The two-dimensional covalent organic framework material is applied to the field of photocatalytic complete water splitting, experiments show that the material has excellent photocatalytic complete water splitting performance, the complete water splitting hydrogen production rate can reach 158 [mu] mol.h <-1 >. G <-1 > under visible light irradiation, the oxygen production rate can reach 78 [mu] mol.h <-1 >. G <-1 >, a new thought is provided for development of the two-dimensional covalent organic framework, and the two-dimensional covalent organic framework material has important significance.

Description

Technical Field

[0001] The invention relates to the preparation of a thiol-containing two-dimensional covalent organic framework and the application of its photocatalytic overall water splitting performance.

[0002] With the rapid economic development and the increasing population, human society is increasingly dependent on energy. The rapid consumption of traditional fossil energy has triggered a severe energy crisis and led to serious environmental pollution and ecological damage. Therefore, it is particularly important to develop and utilize clean, renewable green energy to replace fossil energy and change the environmental pollution problem. Among many energy sources, hydrogen energy has the advantages of being renewable, high in energy density, and zero pollution. It is considered to be one of the most promising energy sources to solve the energy crisis. Photocatalytic water splitting using inexhaustible solar energy as the driving force to produce hydrogen and oxygen is the cleanest and most effective way. However, due to the problem of easy recombination of electrons and holes in photocatalysts, the efficiency of water splitting is extremely low. Therefore, introducing thiol groups into two-dimensional covalent organic frameworks to enhance electron transfer efficiency and improve electron-hole separation efficiency is a more effective way.

[0003] Two-dimensional covalent organic frameworks (COFs) are porous crystalline materials formed by covalently connecting elements such as C, H, O, and N. They have the advantages of light weight, low density, high specific surface area, regular structure, uniform pores, relatively stable structure, and easy functional modification. These advantages make COFs show great potential for application in many fields such as gas storage and separation, catalysis, sensing, energy storage, and photoelectric conversion. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the electron holes in the photocatalyst are easy to recombine and the water decomposition efficiency is low, thereby providing a method for preparing a COF containing a thiol group and its application in photocatalytic water decomposition.

[0005] The preparation method of a thiol-containing two-dimensional covalent organic framework of the present invention is completed by the following steps: 1. Preparation of TFPa-COF: 2,4,6-tris(4-formylphenyl)-1,3,5-triazine and p-phenylenediamine were added to a heat-resistant glass tube, followed by a mixed solution of o-dichlorobenzene, n-butanol and acetic acid, and ultrasonically treated for 30 to 35 min at an ultrasonic frequency of 40 kHz, and degassed by three freeze-thaw cycles in a liquid nitrogen bath. After sealing, the tube was heated at 120 to 150 °C for 72 to 120 h, filtered and washed several times with tetrahydrofuran, and dried to obtain the TFPa-COF material; The mass of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine described in step 1 is 19.8 mg; The mass of p-phenylenediamine in step 1 is 8.1 mg; The molar ratio of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine to p-phenylenediamine in step 1 is 2:3; The volume ratio of o-dichlorobenzene, n-butanol and acetic acid in step 1 is 5:5:1; The concentration of acetic acid used in step 1 is 6 mol·L -1 ; After sealing as described in step 1, heat at 120° C. for 72 h; Preparation of TFDBD-COF: The obtained dry TFPa-COF material and 2,5-diamino-1,4-benzenedithiol were mixed. 2. Add a heat-resistant glass tube, then add a mixed solution of o-dichlorobenzene, n-butanol and acetic acid, ultrasonically treat for 60 to 90 minutes at an ultrasonic frequency of 40KHz, perform three freeze-thaw cycles in a liquid nitrogen bath for degassing, seal and heat at 120 to 150°C for 72 to 120 hours, filter and extract with N,N-dimethylformamide for 48 hours, then replace with ethanol and continue Soxhlet extraction for 24 hours, and vacuum dry the sample for later use; The mass of TFPa-COF in step 2 is 10 mg; The mass of 2,5-diamino-1,4-benzenedithiol described in step 2 is 9.17 mg; The mass ratio of TFPa-COF and 2,5-diamino-1,4-benzenedithiol in step 2 is 1:0.917; The volume ratio of o-dichlorobenzene, n-butanol and acetic acid in step 2 is 5:5:1; The concentration of acetic acid used in step 2 is 6 mol·L -1 ; After sealing as described in step 2, the mixture was heated at 120°C for 72 h.

[0006] Beneficial effects of the present invention: The present invention adopts a solvothermal method to successfully synthesize TFPa-COF material using 2,4,6-tris(4-formylphenyl)-1,3,5-triazine and p-phenylenediamine as raw materials. However, the material has poor visible light absorption ability and cannot photolyze water into hydrogen and oxygen. Therefore, the present invention performs a secondary solvothermal reaction of TFPa-COF and 2,5-diamino-1,4-benzenedithiol to synthesize a new COF material TFDBD-COF, which effectively improves visible light absorption, thereby improving performance. The photocatalytic hydrogen production efficiency of TFDBD-COF material is 158 μmol·h -1 ·g -1 , oxygen production efficiency is 78 μmol·h -1 ·g -1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is the structural diagram of TFDBD-COF material; Figure 2 X-ray powder diffraction patterns of TFPa-COF and TFDBD-COF materials; Figure 3 Infrared spectra of TFPa-COF and TFDBD-COF materials; Figure 4 Performance diagram of photocatalytic water splitting of TFPa-COF and TFDBD-COF materials. DETAILED DESCRIPTION

[0008] The present invention is further described below with reference to examples. These examples are only used to illustrate the method of the present invention and have no limitation on the scope of application of the present invention.

[0009] Example 1: The preparation of TFDBD-COF of this embodiment is completed according to the following steps: 1. Preparation of TFPa-COF: 19.8 mg of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine and 8.1 mg of p-phenylenediamine were added to a heat-resistant glass tube, followed by 1 ml of o-dichlorobenzene and 1 ml of n-butanol. After ultrasonic treatment at a frequency of 40 kHz for 30 to 35 min, a 6 mol·L -1 0.2 ml of acetic acid solution was added, and three freeze-thaw cycles were performed in a liquid nitrogen bath for degassing and heating at 120 °C for 72 h. After the temperature dropped to room temperature, it was washed several times with tetrahydrofuran solution and dried to obtain TFPa-COF. 2. Preparation of TFDBD-COF: 10 mg of TFDBD-COF and 9.17 mg of 2,5-diamino-1,4-benzenedithiol were added to a heat-resistant glass tube, and 1 ml of o-dichlorobenzene and n-butanol were added. Ultrasonication was performed at room temperature for 1 h. The ultrasonic water temperature should be controlled below 30 °C. Then 6 mol·L -1 0.2 ml of acetic acid solution was then freeze-thawed three times in a liquid nitrogen bath for degassing and heated at 120°C for 72 h. After the temperature dropped to room temperature, Soxhlet extraction was performed for 48 h and then replaced with ethanol for a further 24 h. The sample was vacuum dried for later use.

[0010] To verify the beneficial effects of the present invention, the following tests were performed: In order to investigate the photocatalytic water splitting effect of TFPa-COF and TFDBD-COF materials, their visible light photocatalytic water splitting performance was tested according to the following method; the test process is as follows: TFPa-COF and TFDBD-COF (10 mg) were used as photocatalysts, 200 μL 1.5 mg ml -1Chloroplatinic acid was used as a co-catalyst and 50 ml of deionized water was used as the reaction liquid. Ultrasonic treatment was performed for 30 min to form a uniform suspension. The suspension was poured into a reactor and the air in the reactor was exhausted. A xenon lamp was used as a light source. The chloroplatinic acid was reduced to platinum as a co-catalyst while evacuating the air. The light was then continued for 5 h. The efficiency of hydrogen production from photocatalytic water splitting of TFDBD-COF was calculated by gas chromatography to be 158 μmmol·h -1 ·g -1 , oxygen production efficiency is 78μmmol·h -1 ·g -1 , while TFPa-COF had no yield.

Claims

1. Preparation of a thiol-containing two-dimensional covalent organic framework and photocatalytic water splitting, characterized in that The method proceeds as follows:

1. Preparation of TFDBD-COF material: TFPa-COF and 2,5-diamino-1,4-benzenedithiol were added to a heat-resistant glass tube, followed by a mixed solution of o-dichlorobenzene, n-butanol and acetic acid. The tube was ultrasonically treated at an ultrasonic frequency of 40 kHz for 45 to 60 min, and degassed by three freeze-thaw cycles in a liquid nitrogen bath. The tube was sealed and heated at 120 to 150°C for 72 to 120 h. The tube was filtered and washed several times with tetrahydrofuran, and dried to obtain the TFDBD-COF material.

2. The preparation of a TFDBD-COF material according to claim 1, characterized in that The mass described in step 1 is 10-15 mg.

3. The preparation of a TFDBD-COF material according to claim 1, characterized in that The mass ratio of TFPa-COF to 2,5-diamino-1,4-benzenedithiol in step 1 is 1:0.

917.

4. The preparation of a TFDBD-COF material according to claim 1, characterized in that The volume ratio of o-dichlorobenzene, n-butanol and acetic acid in step 1 is 5:5:1.

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