CN113087923A

CN113087923A - Azine-connected benzotrithienyl covalent organic framework material and preparation method and application thereof

Info

Publication number: CN113087923A
Application number: CN202110434720.9A
Authority: CN
Inventors: 李留义; 潘国栋; 许�鹏; 于岩
Original assignee: Fuzhou University
Current assignee: Fuzhou University
Priority date: 2021-04-22
Filing date: 2021-04-22
Publication date: 2021-07-09
Anticipated expiration: 2041-04-22
Also published as: CN113087923B

Abstract

An azine-linked benzotrithienyl covalent organic framework material, a preparation method and application thereof. The invention belongs to the field of material preparation, and particularly relates to a synthesis scheme for preparing an azine covalent organic framework material by an imine exchange strategy and application of the synthesis scheme in photocatalytic water decomposition to hydrogen production. Aniline is used as a molecular regulator to react with benzo [1,2-b:3,4-b ': 5, 6-b' ] trithiophene-2, 5, 8-trialdehyde to obtain an intermediate, and then the intermediate and hydrazine hydrate are subjected to imine exchange to finally obtain an Azine covalent organic framework material (BTT-Azine COF). The azine covalent organic framework is prepared by an imine exchange strategy, and the application of photocatalytic water decomposition to hydrogen production is realized, so that the method has potential application value in the field of photocatalysis.

Description

Azine-connected benzotrithienyl covalent organic framework material and preparation method and application thereof

Technical Field

The invention belongs to the field of material preparation and photocatalysis, and particularly provides a method for preparing azine COF by an imine exchange strategy, which is applied to photocatalytic water decomposition to produce hydrogen.

Background

In recent years, extensive economic development patterns have resulted in the development and utilization of a large number of fossil fuels due to the rapid development of modern industries. The method causes serious problems of resource shortage, environmental pollution and the like, and the search, development and utilization of novel green energy sources become one of the hot subjects of current scientific research. Solar energy is regarded as the most attractive alternative energy source as a green pollution-free inexhaustible energy source. Inspired by photosynthesis, the conversion of solar energy into chemical energy by storing the solar energy in chemical bonds through a photocatalytic technology has become an effective way to solve energy and environmental problems. The development and utilization of visible light are most important to find efficient photocatalyst. Conventional inorganic semiconductors, metal complexes, dyes, etc. have been widely studied due to their unique redox properties, but they have disadvantages of difficulty in separation, difficulty in recovery, etc. Although MOFs exhibit excellent performance in the field of heterogeneous photocatalysis, MOFs are mostly connected by coordination bonds and have poor stability. Therefore, the development of the high-efficiency photocatalyst with high specific surface area, adjustable structure and strong stability has important practical and theoretical significance.

Covalent Organic Frameworks (COFs) are porous materials which are formed by connecting organic building units through reversible covalent bonds, have crystallinity and periodicity, and have the characteristics of high specific surface area, low density, accurate and adjustable structure and the like. The long-range ordered pore channels provide ideal environment for adsorption, diffusion and reaction of small molecular substances, and the Pi-Pi stacked columnar aryl structure can promote separation, diffusion and migration of photo-generated electrons and holes, so that the COFs material becomes a potential candidate of a heterogeneous photocatalyst.

Disclosure of Invention

The invention aims to solve the problems that the conditions for preparing azine covalent organic frameworks by a traditional solvothermal method are severe and the obtained covalent organic framework material has poor crystal form, and provides a method for preparing the azine covalent organic framework material by an imine exchange strategy and application of the method for producing hydrogen by photocatalytic water decomposition.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method of preparing an azine-linked benzotrithienyl covalent organic framework material, comprising the steps of:

(1) benzo [1,2-b:3,4-b ': 5, 6-b' ] trithiophene-2, 5, 8-trialdehyde and aniline are added into a 1, 4-dioxane glacial acetic acid system and refluxed in an oil bath kettle at 120 ℃ for 12 hours to obtain an intermediate.

(2) Adding the intermediate obtained in the step (1) and hydrazine hydrate into an o-dichlorobenzene/1, 4-dioxane/acetic acid mixed solution. Degassing for 3 times in a freezing-thawing cycle in a liquid nitrogen bath, sealing the tube in vacuum, and reacting at 120 ℃ for 3 days to obtain the azine covalent organic framework.

The mass ratio of benzo [1,2-b:3,4-b ': 5, 6-b' ] trithiophene-2, 5, 8-trialdehyde to aniline in step (1) is 1: 5.

The amount of the 1, 4-dioxane in the step (1) is 15 mL, and the amount of the glacial acetic acid is 0.15 mL.

The mass ratio of the intermediate and the hydrazine hydrate in the step (2) is as follows: 6:10.

Further, the amounts of the intermediate and hydrazine hydrate in step (2) were 33.1 mg and 5. mu.L, respectively.

The solvent system in the step (2) is ortho-dichlorobenzene/1, 4 dioxane/acetic acid (volume ratio is 5:5: 1), and the concentration of the acetic acid is 6 mol/L.

The invention has the following remarkable advantages:

1) according to the invention, aniline is used as a molecular regulator, benzo [1,2-b:3,4-b ': 5, 6-b' ] trithiophene-2, 5, 8-trialdehyde and hydrazine hydrate are subjected to an imine exchange strategy to obtain a novel azine covalent organic framework material, and the obtained material has more micropore structures, heteroatoms and two-dimensional conjugated structures, is favorable for transmission of electrons and holes, and shows good activity in a reaction of photocatalytic decomposition of water to produce hydrogen.

2) The equipment and chemical reagents used in the synthesis method are easy to obtain, the process operation is simple and convenient, the process conditions are simple, the applicability is strong, the industrial application value is high, and the method is easy to popularize and utilize.

Drawings

FIG. 1 is a schematic synthesis of the preparation of BTT-Azine COF;

FIG. 2 is an X-ray powder diffraction pattern of BTT-Azine COF by experiment and fitting; the results of the experiment and the fitting are matched to show that the BTT-Azine COF is successfully synthesized;

FIG. 3 is a Fourier transform infrared spectrum of BTT-Azine COF; the appearance of a C = N characteristic absorption peak indicates successful synthesis of the material;

FIG. 4 is an SEM image of BTT-Azine COF; the morphology of BTT-Azine COF can be observed;

FIG. 5 is the UV-visible absorption spectrum of BTT-Azine COF; the absorption range of BTT-Azine COF almost covers the whole ultraviolet-visible spectrum region;

FIG. 6 is a graph of the yield of hydrogen from the photocatalytic decomposition of BTT-Azine COF under visible light conditions over time.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly understood and understandable, the present invention is further described in detail with reference to the following embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention.

Example 1

Benzo [1,2-b:3,4-b ': 5, 6-b' ] trithiophene-2, 5, 8-trialdehyde (BTT: 165 mg, 0.5 mmol), aniline (230. mu.L, 2.5 mmol), 1, 4-dioxane (15 mL), and glacial acetic acid (0.15 mL) were added to a pressure bottle and placed in a 120 ℃ oil bath and refluxed for 12 hours. Then, a yellow solid is precipitated from the ice methanol, and the solid is collected by suction filtration, washed three times with methanol and dried overnight under vacuum at 60 ℃ to obtain an intermediate.

The intermediate (33.1 mg, 0.06 mmol), hydrazine hydrate (5. mu.L, 0.1 mmol) and 1 mL of a mixed solution of o-dichlorobenzene/1, 4-dioxane (volume ratio 1: 1) were placed in a Pyrex tube, and after sonication for 10 minutes, a uniform dispersion was obtained, acetic acid (0.1 mL, 6M) was added. Performing freeze-thaw cycle degassing for 3 times in a liquid nitrogen bath, performing vacuum tube sealing, reacting at 120 ℃ for 3 days, cooling to room temperature, performing suction filtration to collect solids, washing with methanol, dichloromethane and acetone for three times respectively, and performing vacuum drying on the obtained powder at 60 ℃ overnight to obtain yellow powder BTT-Azine COF.

Application example 1

10 mg of BTT-Azine COF was weighed, 100 mg of sodium ascorbate and 3wt% of Pt were added, 50 mL of water was added, and the mixture was placed in a special quartz glass reactor after being subjected to ultrasonic treatment for 5 minutes. After the reactor is vacuumized, a 300W xenon lamp is used for simulating visible light (lambda is more than or equal to 420 nm) irradiation at 290-398K, and gas components after the photocatalytic reaction are detected by gas chromatography at intervals of 0.5 hour in the photocatalytic reaction process.

While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.

Claims

1. A method for preparing an azine-linked benzotrithienyl covalent organic framework material, which is characterized by comprising the following steps: the method comprises the following steps:

(1) adding benzo [1,2-b:3,4-b ': 5, 6-b' ] trithiophene-2, 5, 8-trialdehyde and aniline into a 1, 4-dioxane glacial acetic acid system, and refluxing to obtain an intermediate;

(2) adding the intermediate obtained in the step (1) and hydrazine hydrate into an organic solvent mixed solution; and circularly degassing for 3 times in a liquid nitrogen bath in a freezing-unfreezing way, and reacting after vacuum tube sealing to obtain the benzotrithiophenyl covalent organic framework material.

2. A method of making an azine-linked benzotrithienyl covalent organic framework material of claim 1, wherein: the mass ratio of benzo [1,2-b:3,4-b ': 5, 6-b' ] trithiophene-2, 5, 8-trialdehyde to aniline in step (1) is 1: 5.

3. A method of making an azine-linked benzotrithienyl covalent organic framework material of claim 1, wherein: the refluxing in the step (1) is carried out in an oil bath kettle at the temperature of 120 ℃ for 12 hours.

4. A method of making an azine-linked benzotrithienyl covalent organic framework material of claim 1, wherein: the amount of the 1, 4-dioxane in the step (1) is 15 mL, and the amount of the glacial acetic acid is 0.15 mL.

5. A method of making an azine-linked benzotrithienyl covalent organic framework material of claim 1, wherein: the mass ratio of the intermediate and the hydrazine hydrate in the step (2) is as follows: 6:10.

6. A method of making an azine-linked benzotrithienyl covalent organic framework material of claim 1, wherein: the organic solvent mixed solution system in the step (2) is specifically ortho-dichlorobenzene/1, 4 dioxane/acetic acid.

7. An azine-linked benzotrithienyl covalent organic framework material of claim 6, wherein: the volume ratio of the three is as follows: o-dichlorobenzene: 1,4 dioxane: acetic acid =5:5: 1.

8. An azine-linked benzotrithienyl covalent organic framework material of claim 6, wherein: the reaction after the vacuum tube sealing in the step (2) is specifically carried out for 3 days at 120 ℃.

9. Benzotrithiophenyl covalent organic framework materials obtainable by the process according to any one of claims 1 to 8.

10. Use of the benzotrithiophenyl covalent organic framework material prepared by the method of any one of claims 1-8 for photocatalytic decomposition of water to produce hydrogen.