Preparation of a thiol-containing two-dimensional covalent organic framework and application of photocatalytic overall water splitting performance

Abstract

This invention relates to the preparation of a thiol-containing covalent organic framework (COF) and its application in photocatalytic water splitting. The invention provides a thiol-containing covalent organic framework material (TFDBD-COF) to address the problems of low photocatalytic water splitting efficiency and low visible light utilization of existing covalent organic framework materials. Methods: 1. Preparation of TFDBD-COF material; 2. Preparation of TFDBD-COF material. This invention is applied to the field of photocatalytic water splitting. Experiments show that this material has excellent photocatalytic water splitting performance, achieving a hydrogen production rate of 158 μmol·h⁻¹ under visible light irradiation. ‑1 ·g ‑1 The oxygen production rate can reach 78 μmol·h⁻¹ ‑1 ·g ‑1 This provides a new approach for the development of two-dimensional covalent organic frameworks and is of great significance.

Description

Technical Field

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

[0002] With rapid economic development and a growing population, human society's dependence on energy is increasing daily. The rapid depletion of traditional fossil fuels has triggered a severe energy crisis, leading to serious environmental pollution and ecological damage. Therefore, developing and utilizing clean, renewable, and green energy sources to replace fossil fuels while addressing environmental pollution is of paramount importance. Among various energy sources, hydrogen energy, with its advantages of being renewable, having high energy density, and zero pollution, is considered one of the most promising energy sources for solving the energy crisis. Photocatalytic water splitting to produce hydrogen and oxygen using inexhaustible solar energy is one of the cleanest and most effective methods. 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 a two-dimensional covalent organic framework to enhance electron transport efficiency and improve electron-hole separation efficiency is a more effective approach.

[0003] Two-dimensional covalent organic frameworks (COFs) are porous crystalline materials composed of elements such as C, H, O, and N connected by covalent bonds. They have advantages such as light weight, low density, high specific surface area, regular structure, uniform pores, relatively stable structure, and easy functionalization modification. As a result, COFs have shown 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 this invention is to solve the problems of easy recombination of electrons and holes in photocatalysts and low water splitting efficiency, thereby providing a method for preparing COF containing thiol groups and its application in photocatalytic water splitting.

[0005] The method for preparing a thiol-containing two-dimensional covalent organic framework according to the present invention is carried out according to the following steps:

[0006] I. Preparation of TFPa-COF: 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and p-phenylenediamine were added to a heat-resistant glass tube, followed by the addition of a mixed solution of o-dichlorobenzene, n-butanol and acetic acid. The tube was ultrasonically treated at a frequency of 40 kHz for 30-35 min, degassed by three freeze-thaw cycles in a liquid nitrogen bath, sealed, and heated at 120-150 °C for 72-120 h. The tube was then filtered, washed several times with tetrahydrofuran, and dried to obtain the TFPa-COF material.

[0007] The mass of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine mentioned in step one is 19.8 mg;

[0008] The mass of p-phenylenediamine mentioned in step one is 8.1 mg;

[0009] The molar ratio of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and p-phenylenediamine in step one is 2:3;

[0010] The volume ratio of o-dichlorobenzene, n-butanol, and acetic acid in step one is 5:5:1;

[0011] The concentration of acetic acid used in step one is 6 mol·L⁻¹. -1 ;

[0012] After sealing as described in step one, heat at 120 °C for 72 h;

[0013] II. Preparation of TFBDD-COF: The obtained dried TFBDD-COF material and 2,5-diamino-1,4-benzenedithiol were then mixed.

[0014] Add the sample to a heat-resistant glass tube, followed by a mixed solution of o-dichlorobenzene, n-butanol, and acetic acid. Sonicate the sample at a frequency of 40 kHz for 60–90 min, degas it by three freeze-thaw cycles in a liquid nitrogen bath, seal it, and heat it at 120–150 °C for 72–120 h. Filter the sample and extract it with N,N-dimethylformamide by Soxhlet extraction for 48 h, then replace the extraction with ethanol and continue Soxhlet extraction for 24 h. The sample is then vacuum dried for later use.

[0015] The mass of TFPa-COF mentioned in step two is 10 mg;

[0016] The mass of 2,5-diamino-1,4-benzenedithiol mentioned in step two is 9.17 mg;

[0017] In step two, the mass ratio of TFPa-COF to 2,5-diamino-1,4-benzenedithiol is 1:0.917.

[0018] The volume ratio of o-dichlorobenzene, n-butanol, and acetic acid in step two is 5:5:1;

[0019] The concentration of acetic acid used in step two is 6 mol·L⁻¹. -1 ;

[0020] After sealing as described in step two, heat at 120 °C for 72 h.

[0021] The beneficial effects of this invention are:

[0022] This invention employs a solvothermal method to successfully synthesize TFPa-COF material using 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and p-phenylenediamine as raw materials. However, this material has poor visible light absorption and cannot photolyze water into hydrogen and oxygen. Therefore, this invention synthesizes a novel COF material, TFBDD-COF, by reacting TFPa-COF with 2,5-diamino-1,4-phenylenediol in a secondary solvothermal reaction. This material effectively improves visible light absorption, thereby enhancing performance. The photolytic hydrogen production efficiency of TFBDD-COF material is 158 μmol·h⁻¹. -1 ·g -1 The oxygen production efficiency is 78 μmol·h⁻¹ -1 ·g -1 . Attached Figure Description

[0023] Figure 1 Here is a structural diagram of the TFDBD-COF material;

[0024] Figure 2 X-ray powder diffraction patterns of TFPa-COF and TFDBD-COF materials;

[0025] Figure 3 Infrared spectra of TFPa-COF and TFDBD-COF materials;

[0026] Figure 4 The graph shows the photocatalytic water splitting performance of TFPa-COF and TFDBD-COF materials. Detailed Implementation

[0027] The present invention will be further illustrated below with examples. These examples are only for illustrating the method of the present invention and do not limit the scope of application of the present invention in any way.

[0028] Example 1: The preparation of TFDBD-COF in this embodiment was carried out according to the following steps:

[0029] I. Preparation of TFPa-COF: 19.8 mg of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and 8.1 mg of p-phenylenediamine were added to a heat-resistant glass tube, followed by 1 ml each of o-dichlorobenzene and n-butanol. The mixture was sonicated at 40 kHz for 30–35 min, and then 6 mol·L⁻¹ of COF was added. -1 0.2 ml of acetic acid solution was degassed by three freeze-thaw cycles in a liquid nitrogen bath and heated at 120 °C for 72 h. After the temperature was reduced to room temperature, the solution was washed several times with tetrahydrofuran solution and dried to obtain TFPa-COF.

[0030] II. 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, followed by 1 ml each of o-dichlorobenzene and n-butanol. The mixture was sonicated at room temperature for 1 h, with the sonication water temperature controlled below 30 °C. Then, 6 mol·L⁻¹ of TFDBD-COF was added. -1 0.2 ml of acetic acid solution was added, and the sample was degassed by three freeze-thaw cycles in a liquid nitrogen bath and heated at 120 °C for 72 h. After the temperature dropped to room temperature, Soxhlet extraction was performed for 48 h, followed by Soxhlet extraction with ethanol for another 24 h. The sample was then vacuum dried for later use.

[0031] The following experiments were conducted to verify the beneficial effects of the present invention:

[0032] To investigate the photocatalytic water splitting performance of TFPa-COF and TFDBD-COF materials, their visible light photocatalytic water splitting performance was tested using the following method: TFPa-COF and TFDBD-COF (10 mg) were used as photocatalysts, respectively, in a 200 μL 1.5 mg / mL solution. -1 Chloroplatinic acid was used as a cocatalyst, and 50 ml of 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 the reactor, and the air inside was purged. A xenon lamp was then used as the light source, and the reactor was irradiated for 30 min while being evacuated to reduce chloroplatinic acid to platinum, which served as the cocatalyst. Irradiation continued for 5 h. Gas chromatography was used to calculate the photocatalytic hydrogen production efficiency of TFDBD-COF through water splitting to 158 μmmol·h. -1 ·g -1 The oxygen production efficiency was 78 μmmol·h. -1 ·g -1 TFPa-COF, however, has no yield.

Claims

1. The application of a thiol-containing two-dimensional covalent organic framework in photocatalytic water splitting, characterized in that, The preparation method of the thiol-containing two-dimensional covalent organic framework is carried out according to the following steps: Step 1: Preparation of TFPa-COF material: 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine and p-phenylenediamine were added to a heat-resistant glass tube, followed by the addition of a mixed solution of o-dichlorobenzene, n-butanol and acetic acid. The tube was ultrasonically treated at a frequency of 40 kHz for 30–35 min, degassed by three freeze-thaw cycles in a liquid nitrogen bath, sealed, and heated at 120–150 °C for 72–120 h. The tube was then filtered, washed several times with tetrahydrofuran, and dried to obtain the TFPa-COF material. Step 2: Preparation of TFDBD-COF material: TFPa-COF and 2,5-diamino-1,4-benzenedithiol were added to a heat-resistant glass tube, followed by the addition of a mixed solution of o-dichlorobenzene, n-butanol and acetic acid. The mixture was ultrasonically treated at a frequency of 40 kHz for 45–60 min, degassed by three freeze-thaw cycles in a liquid nitrogen bath, sealed, and heated at 120–150 °C for 72–120 h. The mixture was then filtered, washed several times with tetrahydrofuran, and dried to obtain the TFBDD-COF material. The mass of the 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine is 19.8 mg; The mass of the p-phenylenediamine is 8.1 mg; The volume ratio of o-dichlorobenzene, n-butanol, and acetic acid mentioned in steps one and two is 5:5:1; The concentration of the acetic acid is 6 mol·L⁻¹. -1 ; The mass ratio of TFPa-COF to 2,5-diamino-1,4-benzenedithiol is 1:0.917.

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