Benzothiadiazole metal covalent organic framework material as well as preparation method and application thereof

Abstract

The invention discloses a benzothiadiazole metal covalent organic framework material as well as a preparation method and application thereof, and belongs to the technical field of MCOF photocatalytic materials. The metal covalent organic framework BTD-MCOF shown in the structural formula (I) is synthesized through the dehydration condensation reaction of aldehyde groups and amino groups, the prepared BTD-MCOF photocatalytic material is large in specific surface area and high in porosity, and due to the advantages of large specific surface area, high porosity and the like, the BTD-MCOF has huge application potential in the aspects of gas storage, sensing and the like, and the application prospect is broad. Meanwhile, the hydrogen evolution performance of the prepared sample in the absence of a promoter is 1012 [mu] mol.g <-1 >. H <-1 >, which exceeds the hydrogen evolution performance of most pure COF and MOF.

Description

TECHNICAL FIELD

[0001] The present application relates to a benzothiadiazole-based metal covalent organic framework material and a preparation method and application thereof, and belongs to the technical field of MCOF photocatalytic materials. BACKGROUND

[0002] Hydrogen energy is leading a revolutionary transformation of the energy system from fossil fuels to clean energy due to its significant energy density advantage and zero carbon emission during combustion. In the field of solar energy conversion, photocatalytic water splitting for hydrogen production technology opens up a green path for building a zero-carbon energy storage system by simulating natural photosynthesis. However, the current photocatalytic material system still faces three technical bottlenecks: (1) Although traditional covalent organic frameworks (COFs) have regular pore structures, the uneven distribution of active sites in the organic framework leads to insufficient exposure of the catalytic interface, and the high intramolecular exciton binding energy causes rapid recombination of photo-generated electron-hole pairs, resulting in a significant reduction in photocatalytic kinetic efficiency; (2) Although metal organic frameworks (MOFs) can provide abundant catalytic sites through metal clusters, the weak interaction of metal-organic coordination bonds leads to the collapse of the framework under photocatalytic reaction conditions, and the limited range of pi electron delocalization makes it difficult to break through the efficiency threshold of carrier migration rate; (3) The existing materials generally have the defects of narrow spectral response range (most of which are limited to the ultraviolet-visible light region), short carrier lifetime and poor chemical stability (especially in acid and alkaline environments), which results in that the actual hydrogen production rate is more than 50% lower than the theoretical prediction value.

[0003] It is particularly important to note that there is a fundamental contradiction in the performance optimization of COFs and MOFs in the prior art: increasing the metal doping amount of COFs will destroy the stability of its covalent bond network, causing irreversible pore collapse of the material during the reaction process; and enhancing the pi conjugated system of MOFs will distort the coordination environment of the metal nodes due to the increased rigidity of the organic ligand, thereby weakening its catalytic activity. This mutual exclusion relationship between material properties makes it impossible to simultaneously achieve high-density active site construction, long-range charge transport channel establishment, and wide-spectrum light response capability improvement through simple physical mixing or traditional modification methods. Therefore, how to break through the limitations of material intrinsic properties and synergistically regulate the distribution of catalytic sites, electronic structure and chemical stability at the atomic scale has become a core problem restricting the large-scale application of photocatalytic hydrogen production technology. SUMMARY

[0004] To solve or partially solve the problems in the related art, the present application provides a benzothiadiazole-based metal covalent organic framework material and a preparation method and application thereof.

[0005] The present application provides a benzothiadiazole-based metal covalent organic framework material, the structural formula of which is as formula (I):

[0006]

[0007] wherein M is Cu, Au, Ag or Fe.

[0008] The present application also claims the preparation method of the benzothiadiazole-based metal covalent organic framework material, comprising:

[0009] adding trinuclear metal pyrazole acid salt unit M3(PyCA)3 and 4,7-bis(4-aminophenyl)-2,1,3-benzothiadiazole in a solvent and dispersing uniformly; then adding glacial acetic acid solution and dispersing uniformly, followed by vacuum treatment and heat treatment; finally, soaking in an organic solvent, then washing and drying to obtain the benzothiadiazole-based metal covalent organic framework material.

[0010] Preferably, the substance amount ratio of the trinuclear metal pyrazole acid salt unit M3(PyCA)3 and 4,7-bis(4-aminophenyl)-2,1,3-benzothiadiazole is 1:(0.5-2).

[0011] M3(PyCA)3 is Cu3(PyCA)3, Au3(PyCA)3, Ag3(PyCA)3 or Fe3(PyCA)3.

[0012] Preferably, the preparation method of the trinuclear metal pyrazole acid salt unit M3(PyCA)3 comprises: dissolving metal salt and 1H-pyrazole-4-carboxaldehyde in a mixture of N,N-dimethylformamide, water and ethanol, followed by heating, centrifugal washing and drying to obtain the trinuclear metal pyrazole acid salt unit M3(PyCA)3.

[0013] Preferably, the metal salt is copper nitrate, silver nitrate, iron nitrate or gold chloride; the molar ratio of the metal salt and 1H-pyrazole-4-carboxaldehyde is 1:(0.5-2); the volume ratio of N,N-dimethylformamide, water and ethanol is 1:(0.5-2):(0.5-2); the mass ratio of the mixture of the metal salt and 1H-pyrazole-4-carboxaldehyde and N,N-dimethylformamide, water and ethanol is 1:(10-200); the heating temperature is 80-150℃, and the time is 12-72h.

[0014] Preferably, the solvent is N,N-dimethylformamide, 1,4-dioxane, 1,3,5-trimethylbenzene, acetonitrile, cyclohexane, one or two or more mixtures thereof; the mass ratio of the total mass of the trinuclear metal pyrazole acid salt unit M3(PyCA)3 and 4,7-bis(4-aminophenyl)-2,1,3-benzothiadiazole to the solvent is 1:(20-200).

[0015] Preferably, the volume ratio of the glacial acetic acid solution to the solvent is 1:(1-100); the concentration of the glacial acetic acid solution is 0.1-10M.

[0016] Preferably, the parameters of the vacuum treatment are defined so that the vacuum degree in the reactor is 10 -3 Pa to 10 -6 Pa.

[0017] Preferably, the temperature of the heat treatment is 100-150℃, and the time is 72-120h.

[0018] Preferably, the organic solvent is acetone, carbon tetrachloride or tetrahydrofuran; and the soaking time is 48-72h.

[0019] The technical solution provided by the present application can include the following beneficial effects:

[0020] (1) The BTD-MCOF photocatalytic material prepared by the present application has high photocatalytic efficiency. Due to the special MCOF structure, the number of active sites is increased, and the recombination rate of photo-generated carriers is reduced, thereby improving the photocatalytic efficiency.

[0021] (2) The metal covalent organic framework BTD-MCOF synthesized by the dehydration condensation reaction of aldehyde groups and amino groups will not decompose in water, acid, base and common organic solvents (such as n-hexane, methanol, acetone, tetrahydrofuran, N,N-dimethylformamide, etc.), and has excellent stability. The prepared BTD-MCOF photocatalytic material has large specific surface area and high porosity. The advantages of large specific surface area and high porosity can make the BTD-MCOF have great potential in gas storage, sensing and other aspects. At the same time, the hydrogen evolution performance of the prepared sample without catalyst is 1012μmol·g -1 ·h -1 , which exceeds the hydrogen evolution performance of most pure COFs and MOFs. BRIEF DESCRIPTION OF DRAWINGS

[0022] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout the figures, and wherein exemplary embodiments of the application are shown.

[0023] Figure 1 FTIR diagram of Cu3(PyCA)3, 4,7-bis(4-aminophenyl)-2,1,3-benzothiadiazole and benzothiadiazole-based copper cluster covalent organic framework material prepared in Example 1.

[0024] Figure 2 SEM diagram of benzothiadiazole-based copper cluster covalent organic framework material prepared in Example 1.

[0025] Figure 3TEM image of the benzothiadiazole-based copper cluster covalent organic framework material prepared in Example 1.

[0026] Figure 4 Adsorption-desorption isotherm graph of the benzothiadiazole-based copper cluster covalent organic framework material prepared in Example 1.

[0027] Figure 5 Pore size distribution graph of the benzothiadiazole-based copper cluster covalent organic framework material prepared in Example 1.

[0028] Figure 6 Photocatalytic hydrogen evolution performance graph of the benzothiadiazole-based copper cluster covalent organic framework material prepared in Example 1. DETAILED DESCRIPTION

[0029] The application will be further described in conjunction with the accompanying drawings and specific examples, but the scope of protection of the application is not limited to the content described.

[0030] Example 1

[0031] The preparation method of the trinuclear metal pyrazole acid salt unit Cu3(PyCA)3 includes: dissolving copper nitrate and 1H-pyrazole-4-carboxaldehyde in a mixture of N,N-dimethylformamide, water and ethanol in a molar ratio of 1:1, centrifuging, washing and drying after heating at 100℃ for 48h to obtain the trinuclear metal pyrazole acid salt unit Cu3(PyCA)3.

[0032] The preparation of the benzothiadiazole-based copper cluster covalent organic framework material (BTD-MCOF) includes the following steps:

[0033] The trinuclear copper pyrazole acid salt unit Cu3(PyCA) 20.5mg and 4,7-bis(4- aminophenyl)-2,1,3-benzothiadiazole (BTD) 32.9mg were weighed and added to a 25mL schlenk tube containing 1.5mL 1,4-dioxane and 1.5mL 1,3,5-trimethylbenzene, 0.2mL of 6M glacial acetic acid was added, and the mixture was uniformly mixed by ultrasonic for 30min, then vacuumed to 0.01Pa under liquid nitrogen and placed in an oven for heat treatment, kept at 120℃ for 72h, cooled to room temperature, and then soaked in tetrahydrofuran for 48h, during which the tetrahydrofuran solution was replaced 4 times, and the precipitate was separated by centrifugation to obtain the copper cluster BTD-MCOF material.

[0034] Characterization of the benzothiadiazole-based copper cluster covalent organic framework material:

[0035] The benzothiadiazole-based copper cluster covalent organic framework material (BTD-MCOF) was characterized by infrared spectroscopy, as shown in Figure 1 The infrared spectra of the monomer and BTD-MCOF are shown in the figure. By comparing the infrared spectra of the monomer and BTD-MCOF, it is found that the ~ 3300cm1 the disappearance of the aldehyde group at ~ 1600 cm 1

[0036] As Figure 2 and Figure 3 showed that BTD-MCOF presented uniform sheet-like structure.

[0037] As Figure 4 The specific surface area of BTD-MCOF was 165 m 2 / g, as shown by the adsorption-desorption isotherm. Figure 5 The pore size distribution of BTD-MCOF was about 1.6 nm, which was basically consistent with the theoretical pore size distribution.

[0038] Performance test of benzothiadiazole-based copper cluster covalent organic framework material:

[0039] As Figure 6 shown, the hydrogen evolution performance was evaluated by using a multi-channel photocatalytic reaction system for 25 consecutive hours of photocatalytic hydrogen production test. In the reaction cell, 2 mg of catalyst was mixed with 30 mL of water containing 0.1 M ascorbic acid (AA) at 25°C. The system was irradiated with a 10 W LED lamp. The generated H2 was analyzed by a gas chromatograph. BTD-MCOF reached a photocatalytic hydrogen evolution performance of 1012μmol·g -1 ·h -1 , and had certain performance stability. In addition, the photocatalytic hydrogen production performance of BTD and M3(PyCA)3 was tested, and it was found that they did not have the hydrogen evolution performance of BTD and M3(PyCA)3.

[0040] Example 2

[0041] The preparation method of the trinuclear metal pyrazole acid salt unit Fe3(PyCA)3 includes: dissolving ferric nitrate and 1H-pyrazole-4-carboxaldehyde in a mixture of N,N-dimethylformamide, water and ethanol at a molar ratio of 1:2, centrifuging, washing and drying after heating at 80°C for 72h to obtain the trinuclear metal pyrazole acid salt unit M3(PyCA)3.

[0042] The volume ratio of N,N-dimethylformamide, water and ethanol is 1:2:0.5; the mass ratio of metal salt and 1H-pyrazole-4-carboxaldehyde to the mixture of N,N-dimethylformamide, water and ethanol is 1:10.

[0043] Preparation of benzothiadiazole-based iron cluster covalent organic framework material (BTD-MCOF) includes the following steps:

[0044] ​The trinuclear metal pyrazole acid salt unit Fe3(PyCA)3 and 4,7-bis(4- aminophenyl)-2,1,3-benzothiadiazole (BTD) were weighed according to a molar ratio of 1:0.5, and then added to a 25 mL schlenk tube containing N,N dimethylformamide, and the mass ratio of the total mass of the trinuclear metal pyrazole acid salt unit Fe3(PyCA)3 and 4,7-bis(4- aminophenyl)-2,1,3-benzothiadiazole to the mass of N,N dimethylformamide was 1:200, 10M glacial acetic acid (volume ratio of glacial acetic acid to N,N dimethylformamide was 1:100) was added, and the mixture was uniformly mixed by ultrasonic for 30 min, and then vacuumed to 1 Pa under liquid nitrogen and placed in an oven for heat treatment, and kept at 100℃ for 120 h, and then cooled to room temperature, and then soaked in carbon tetrachloride for 72 h, and the carbon tetrachloride was replaced 4 times during the soaking, and the precipitate was separated by centrifugation to obtain the iron cluster BTD-MCOF material.

[0045] Through 25 hours of continuous photocatalytic hydrogen production test, the BTD-MCOF reached a photocatalytic hydrogen evolution performance of 895 μmol·g -1 ·h -1 , and had certain performance stability.

[0046] Example 3

[0047] The preparation method of the trinuclear metal pyrazole acid salt unit Ag3(PyCA)3 includes: dissolving silver nitrate and 1H-pyrazole-4-carboxaldehyde in a mixture of N,N-dimethylformamide, water and ethanol according to a molar ratio of 1:0.5, and then centrifuging, washing and drying after heating at 150℃ for 12 h to obtain the trinuclear metal pyrazole acid salt unit M3(PyCA)3.

[0048] The volume ratio of N,N-dimethylformamide, water and ethanol is 1:0.5:2; and the mass ratio of the metal salt and 1H-pyrazole-4-carboxaldehyde to the mixture of N,N-dimethylformamide, water and ethanol is 1:200.

[0049] The preparation of the benzothiadiazole-based silver cluster covalent organic framework material (BTD-MCOF) includes the following steps:

[0050] The trinuclear silver pyrazolate unit Ag3(PyCA)3 and 4,7-bis(4- aminophenyl)-2,1,3-benzothiadiazole (BTD) were weighed according to a molar ratio of 1:2, then added to a 25 mL schlenk tube containing N,N dimethylformamide, the mass ratio of the total mass of the trinuclear silver pyrazolate unit Ag3(PyCA)3 and 4,7-bis(4- aminophenyl)-2,1,3-benzothiadiazole to the mass of N,N dimethylformamide was 1:20, 0.1 M glacial acetic acid (volume ratio of glacial acetic acid to N,N dimethylformamide was 1:1) was added, and the mixture was uniformly mixed by ultrasonic for 30 min, then vacuumized to 0.05 Pa under liquid nitrogen and placed in an oven for heat treatment, kept at 150 ℃ for 72 h, cooled to room temperature, then soaked in acetone for 52 h, during which the acetone was replaced 4 times, and the precipitate was separated by centrifugation to obtain the silver cluster BTD-MCOF material.

[0051] Through 25 hours of continuous photocatalytic hydrogen production test, the BTD-MCOF reached a photocatalytic hydrogen evolution performance of 962 μmol·g -1 ·h -1 , and had certain performance stability.

[0052] Comparative Example 1

[0053] A preparation method of a covalent organic framework material, comprising the following steps:

[0054] The trinuclear copper pyrazolate unit Cu3(PyCA)3 20.5 mg and 4,7-bis(4- aminophenyl)-2,1,3-benzothiadiazole (BTD) 32.9 mg were weighed and added to a 25 mL schlenk tube containing 1.5 mL 1,4-dioxane and 1.5 mL 1,3,5-trimethylbenzene, 6M benzoic acid 0.2 mL was added, the mixture was uniformly mixed by ultrasonic for 30 min, then vacuumized to 0.01 Pa under liquid nitrogen and placed in an oven for heat treatment, kept at 120 ℃ for 72 h, cooled to room temperature, then soaked in tetrahydrofuran for 48 h, during which the tetrahydrofuran solution was replaced 4 times, and the precipitate was separated by centrifugation to obtain the covalent organic framework material.

[0055] The covalent organic framework material prepared in the present comparative example is not the benzothiadiazole-based metal covalent organic framework material prepared in the embodiments of the present application, the structures are different, and the covalent organic framework material does not have photocatalytic hydrogen evolution performance.

[0056] Having described various embodiments of the application, it is to be understood that the above description is meant to be illustrative only and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art, without departing from the scope and spirit of the described embodiments. The choice of words in this document is intended to best explain the principles of the embodiments, the practical application, or improvement over the technology in the art, or to enable other ordinary skilled in the art to understand the embodiments disclosed herein.

Claims

1. A benzothiadiazolyl metal covalent organic framework material, characterized by: The structural formula is as follows: wherein M is Cu, Au, Ag or Fe.

2. The method for preparing the benzothiadiazolyl metal covalent organic framework material according to claim 1, characterized in that: include: Trinuclear metal pyrazolate unit M3(PyCA)3 and 4,7-bis(4-aminophenyl)-2,1,3-benzothiadiazole are added to a solvent and dispersed evenly; then glacial acetic acid solution is added to disperse evenly and then vacuum heat treated; finally, the benzothiadiazole-based metal covalent organic framework material is obtained after soaking in an organic solvent, washing and drying.

3. The method for preparing the benzothiadiazolyl metal covalent organic framework material according to claim 2, characterized in that: The preparation method of the trinuclear metal pyrazolate unit M3(PyCA)3 includes: dissolving a metal salt and 1H-pyrazole-4-carboxaldehyde in a mixture of N,N-dimethylformamide, water and ethanol, heating, centrifuging, washing and drying to obtain the trinuclear metal pyrazolate unit M3(PyCA)3.

4. The method for preparing the benzothiadiazolyl metal covalent organic framework material according to claim 3, characterized in that: The metal salt is copper nitrate, silver nitrate, iron nitrate or gold chloride; the molar ratio of the metal salt to 1H-pyrazole-4-carboxaldehyde is 1:(0.5-2); the volume ratio of N,N-dimethylformamide, water and ethanol is 1:(0.5-2):(0.5-2); the mass ratio of the metal salt to 1H-pyrazole-4-carboxaldehyde and the mixture of N,N-dimethylformamide, water and ethanol is 1:(10-200); the heating temperature is 80-150°C and the heating time is 12-72 hours.

5. The method for preparing the benzothiadiazolyl metal covalent organic framework material according to claim 2, characterized in that: The molar ratio of the trinuclear metal pyrazolate unit M3(PyCA)3 and 4,7-bis(4-aminophenyl)-2,1,3-benzothiadiazole is 1:(0.5-2).

6. The method for preparing the benzothiadiazolyl metal covalent organic framework material according to claim 2, characterized in that: The solvent is one or a mixture of two or more of N,N-dimethylformamide, 1,4-dioxane, 1,3,5-mesitylene, acetonitrile, and cyclohexane; the mass ratio of the total mass of the trinuclear metal pyrazolate unit M3(PyCA)3 and 4,7-bis(4-aminophenyl)-2,1,3-benzothiadiazole to the solvent is 1:(20-200).

7. The method for preparing a benzothiadiazolyl metal covalent organic framework material according to claim 2, characterized in that: The volume ratio of the glacial acetic acid solution to the solvent is 1:(1-100); the concentration of the glacial acetic acid solution is 0.1-10M.

8. The method for preparing a benzothiadiazolyl metal covalent organic framework material according to claim 2, wherein: The vacuum heat treatment is performed at a temperature of 100-150° C. and for a time of 72-120 hours.

9. The method for preparing a benzothiadiazolyl metal covalent organic framework material according to claim 2, characterized in that: The organic solvent is acetone, carbon tetrachloride or tetrahydrofuran; and the soaking time is 48-72 hours.

10. Use of the benzothiadiazolyl metal covalent organic framework material according to claim 1 in photocatalytic hydrogen evolution.

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