A loofah-like covalent organic framework material and a preparation method and application thereof

Abstract

The application belongs to the field of material synthesis, and particularly relates to a loofah-like covalent organic framework material and a preparation method and application thereof.i) uniformly dispersing a monomer C3 containing an aldehyde group function and a triazine structure, a monomer C2 containing an amino group and a mercapto group, a catalyst and a regulator in an organic solvent to obtain a dispersion liquid;ii) allowing the dispersion liquid to undergo a reversible reaction at 20-50 DEG C for 1-5 days, so that the construction units of the two monomers are connected together to obtain a corresponding product, and the product is washed and dried to obtain the loofah-like covalent organic framework material.The preparation method of the application can synthesize the covalent organic framework material under room temperature conditions, the reaction condition is mild, the preparation is convenient, the harsh conditions of high-temperature synthesis are avoided, the micro morphology can be controlled, and the covalent organic framework material with a loofah-like structure is prepared.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of material synthesis, and particularly relates to a loofah-like covalent organic framework material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of industry and agriculture, various pollutants such as heavy metal ions are discharged and exist in various environmental media, which has brought great threat to the ecological environment and human health. At present, the removal methods of pollutants such as heavy metals mainly include electrochemical method, membrane separation method, biological remediation method and adsorption method. Compared with other methods, the adsorption method has the characteristics of low cost and good selectivity, and has attracted widespread attention. However, the common adsorbents such as activated carbon usually have the problem of limited adsorption capacity, therefore, the preparation of new adsorbents with large specific surface area and high adsorption capacity has always been a great challenge.

[0003] Covalent organic framework materials as a new star material are widely used in fuel cells, gas storage, sensors, adsorbents and biological medicines due to their large specific surface area, easy functionalization design and good chemical stability. In recent years, covalent organic framework materials containing thiol functional groups have shown great application value in removing heavy metal ions due to their special structure. Mondal et al. (Mondal, Sujan, et al. ACS Sustainable Chemistry&Engineering 2019, 7(7): 7353-7361.) reported a new thioether functionalized covalent triazine nanosphere SCTN-1, which was used as a high-efficiency adsorbent for removing heavy metal Hg 2+ from contaminated water, and the maximum adsorption capacity could reach 1253mg / g, which was superior to several recently reported thiol and thioether functionalized adsorbents.

[0004] At present, the common covalent organic framework materials are usually synthesized by high-temperature method, which has relatively harsh conditions. At the same time, the morphology of the material is rarely controlled, and the morphology is an important factor affecting the adsorption performance. SUMMARY

[0005] The present application aims to provide a loofah-like covalent organic framework material and a preparation method and application thereof.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of a loofah-like covalent organic framework material:

[0008] i) uniformly dispersing a monomer C3 containing aldehyde functional groups and triazine structure, a monomer C2 containing amino and thiol, a catalyst and a regulator in an organic solvent to obtain a dispersion liquid;

[0009] ii) reversibly reacting the dispersion liquid at 20-50°C for 1-5 days to connect the building units of the two monomers together to obtain the corresponding product, and washing and drying the product to obtain the silk-vein-like covalent organic framework material.

[0010] The monomer C3 is a substance containing a triazine structure and at least 3 aldehyde groups; the monomer C2 is a substance containing amino groups and mercapto groups, and the number of amino groups and mercapto groups is at least 2 or more, respectively.

[0011] Preferably, the monomer C3 is a substance containing a triazine structure and 3-6 aldehyde groups; the monomer C2 is a substance containing amino groups and mercapto groups, and the number of amino groups and mercapto groups is 2-4.

[0012] More preferably, the monomer C3 is 2,4,6-tris(4-vinylphenyl)-1,3,5-triazine; and the monomer C2 is 2,5-dimercaptobenzene-1,4-diamine.

[0013] The molar ratio of the monomer C3 to the monomer C2 is 1:8-8:1, preferably 1:4-4:1, and more preferably 2:3.

[0014] The final concentration of the catalyst in the dispersion liquid is 0.15-1 mM, preferably 0.6 mM; and the volume ratio of the regulator to the dispersion liquid is 1:100-1:400, preferably 1:200.

[0015] The catalyst is acetic acid or / and cesium carbonate, preferably acetic acid; and the regulator is aniline or / and phenylenediamine, preferably aniline.

[0016] The organic solvent is one or more of mesitylene, 1,4-dioxane, n-butanol, o-dichlorobenzene or acetonitrile.

[0017] The organic solvent is mesitylene and 1,4-dioxane, and the volume ratio of the two is (0.1-1):(0.1-1).

[0018] The silk-vein-like covalent organic framework material prepared by the method has a microstructure of silk-vein-like, rich pore structure, large specific surface area and high thermal stability, and contains a large amount of S elements and active sites.

[0019] The application of the silk-vein-like covalent organic framework material, in particular, the application of the silk-vein-like covalent organic framework material in adsorbing heavy metals in the environment.

[0020] The application of the silk-vein-like covalent organic framework material in adsorbing heavy metals in water.

[0021] The advantages of the present application are:

[0022] (1) The preparation method of the present application can synthesize covalent organic framework materials at room temperature, the reaction conditions are mild, the preparation is convenient, the harsh conditions of high temperature synthesis are avoided, and the micro morphology can be controlled to prepare covalent organic framework materials with a sponge-like structure.

[0023] (2) The sponge-like covalent organic framework material prepared by the present application has the advantages of rich pores and large specific surface area, which is beneficial to the adsorption of various pollutants. At the same time, it has high thermal stability and can be applied in different environments.

[0024] (3) The sponge-like covalent organic framework material prepared by the present application contains rich S elements, which can provide more active sites for heavy metal ions, is beneficial to the adsorption of heavy metal pollutants, and is expected to realize the simultaneous adsorption and removal of various heavy metal pollutants. At the same time, it can also be used as a single atom carrier and has good application prospect in catalysis. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a synthesis and structure diagram of the sponge-like covalent organic framework material prepared at room temperature.

[0026] Figure 2 It is a Fourier transform infrared spectrum (FT-IR) diagram of two monomers and the synthesized sponge-like covalent organic framework material.

[0027] Figure 3 It is a thermogravimetric analysis diagram of the sponge-like covalent organic framework material, in which the horizontal coordinate represents temperature and the vertical coordinate represents mass loss percentage.

[0028] Figure 4 It is an EDS spectrum of the sponge-like covalent organic framework material.

[0029] Figure 5 It is a scanning electron microscope image of the sponge-like covalent organic framework material.

[0030] Figure 6 It is an XRD diagram of the sponge-like covalent organic framework material.

[0031] Figure 7 It is an adsorption thermodynamic curve of the sponge-like covalent organic framework material.

[0032] Figure 8 It is an adsorption kinetic curve of the sponge-like covalent organic framework material. DETAILED DESCRIPTION

[0033] In order to make the content of the present application more convenient to understand, the technical solutions of the present application are further described below in combination with examples, and it should be pointed out that the specific embodiments described herein are only for the purpose of illustration and explanation of the present application, but the present application is not limited thereto.

[0034] The preparation method of the present application is simple and easy to operate. The covalent organic framework material prepared in the present application has a silk gourd pulp structure, which has rich pore structure, large specific surface area and high thermal stability, contains a large amount of S element, has many active sites and high adsorption capacity, can be used as an adsorbent for adsorption removal of heavy metal ions and other pollutants, and also has good application prospect in single atom loading.

[0035] The silk gourd pulp-shaped covalent organic framework material described in the present application has the characteristics of rich pores, large specific surface area and many active sites, has high adsorption capacity, can be used as an adsorbent, and can be used for adsorption removal of heavy metal ions and other pollutants, and can also be used for loading of single atoms. Example 1

[0036] 25mg 2,4,6-tris(4-vinylphenyl)-1,3,5-triazine, 23.37mg 2,5-dimercaptobenzene-1,4-diamine, 1mL 1,4 dioxane, 1mL mesitylene, 0.1mL 6M acetic acid and 10μL aniline were added into a 10mL centrifuge tube, and after ultrasonic dispersion for 2 minutes, it was sealed. Reaction was carried out at room temperature for 72 hours. Then, the prepared solid material was washed with acetone three times, each time 50mL, and then washed with ethanol three times, each time 50mL. Subsequently, the washed solid material was dried at 100℃ under vacuum for 24 hours to obtain a brown yellow powder-shaped silk gourd pulp-shaped covalent organic framework material, as shown in Figure 1 .

[0037] The obtained silk gourd pulp-shaped covalent organic framework material was subjected to Fourier transform infrared spectroscopy (FT-IR) analysis, and the results are shown in Figure 2 . Figure 2 It can be seen from that the corresponding functional groups of aldehyde and amino groups are weakened or disappeared, and new C=N double bonds are generated.

[0038] Figure 3 The obtained silk gourd pulp-shaped covalent organic framework material was subjected to thermogravimetric analysis, and the results are shown in Figure 3 . It can be seen from that the silk gourd pulp-shaped covalent organic framework material has high thermal stability within 400℃.

[0039] The obtained silk gourd pulp-shaped covalent organic framework material was subjected to EDS energy spectrum analysis, and the results are shown in Figure 4 . It can be seen from Figure 4 that the silk gourd pulp-shaped covalent organic framework material contains rich S element.

[0040] The obtained silk gourd-like covalent organic framework material was subjected to scanning electron microscope analysis, and the results are shown in Figure 5 Figure 5 It can be seen that the covalent organic framework material has a silk gourd-like structure, high porosity, and an average size of about 10 μm.

[0041] The obtained silk gourd-like covalent organic framework material was subjected to X-ray diffraction analysis, and the results are shown in Figure 6 Figure 6 It can be seen that the silk gourd-like covalent organic framework material has a certain crystallinity. Example 2

[0042] 2 mg of the silk gourd-like covalent organic framework material prepared in Example 1 was weighed and added to a series of heavy metal Hg 2+ standard solutions (10 mL of standard solution for each concentration), and shaken for adsorption at room temperature for 24 hours. After shaking, 5 mL was taken by a syringe, filtered by a filter head, and the Hg 2+ concentration in the residual liquid was measured. The detection results are shown in Figure 7 It can be seen that the maximum adsorption capacity of the silk gourd-like covalent organic framework material for heavy metal Hg 2+ adsorption is about 600 mg / g.

[0043] 10 mg of the silk gourd-like covalent organic framework material prepared in Example 1 was weighed and added to 50 mL of 20 mg / L Hg 2+ standard solution, and shaken. After 2, 4, 6, 8, 10, 20, 30, 50 and 100 minutes, respectively, 2 mL was taken by a syringe, filtered by a filter head, and the Hg 2+ concentration in the residual liquid was measured. The detection results are shown in Figure 8 It can be seen that the concentration of Hg 2+ decreases gradually with the increase of time, and the adsorption effect will be better when the time continues to be prolonged.

[0044] The above description is only a preferred embodiment of the present application, and does not limit the present application in any form. Any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.​​

Claims

1. A method for preparing a loofah-like covalent organic framework material, characterized in that: i) A dispersion is obtained by uniformly dispersing monomer C3 containing aldehyde functional groups and triazine structure, monomer C2 containing amino and mercapto groups, catalyst and regulator in an organic solvent. ii) The above dispersion was subjected to a reversible reaction at 20~50℃ for 1-5 days to allow the building units of the two monomers to be linked together to obtain the corresponding product. The product was washed and dried to obtain a loofah-like covalent organic framework material. The monomer C3 is 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine; the monomer C2 is 2,5-dimercaptophenyl-1,4-diamine; The catalyst is acetic acid, and the regulator is aniline; The organic solvent is one or more of mesitylene, 1,4-dioxane, n-butanol, o-dichlorobenzene, or acetonitrile.

2. The method for preparing the loofah-like covalent organic framework material according to claim 1, characterized in that: The molar ratio of monomer C3 to monomer C2 is 1:8 to 8:1; the final concentration of catalyst in the dispersion is 0.15 to 1 mM, and the volume ratio of regulator to dispersion is 1:100 to 1:

400.

3. The method for preparing the loofah-like covalent organic framework material according to claim 1, characterized in that: The organic solvent is mesitylene and 1,4-dioxane, with a volume ratio of (0.1-1):(0.1-1).

4. A loofah-like covalent organic framework material prepared by the method of claim 1, characterized in that: The preparation method of claim 1 yields a covalent organic framework material with a microstructure resembling a loofah sponge, rich pore structure, large specific surface area, high thermal stability, and containing a large amount of sulfur and numerous active sites.

5. An application of the loofah-like covalent organic framework material according to claim 4, characterized in that: Application of the loofah-like covalent organic framework material in adsorbing heavy metals in the environment.

6. The application of the loofah-like covalent organic framework material according to claim 5, characterized in that: Application of the loofah-like covalent organic framework material in the adsorption of heavy metals in water.

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