Vegetable-sponge-shaped covalent organic framework material as well as preparation method and application thereof

Abstract

The invention belongs to the field of material synthesis, and particularly relates to a vegetable-sponge-shaped covalent organic framework material as well as a preparation method and application thereof. I) uniformly dispersing a monomer C3 containing an aldehyde group functional group and a triazine structure, a monomer C2 containing an amino group and a sulfydryl group, a catalyst and a regulating agent in an organic solvent to obtain a dispersion liquid; and ii) carrying out a reversible reaction on the dispersion liquid 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 washing and drying the product to obtain the vegetable sponge-shaped covalent organic framework material. According to the preparation method disclosed by the invention, the covalent organic framework material can be synthesized at room temperature, the reaction condition is mild, the preparation is convenient, the harsh condition of high-temperature synthesis is avoided, meanwhile, the microstructure can be controlled, and the covalent organic framework material with a vegetable sponge-shaped structure is prepared.

Description

Technical Field

[0001] The invention belongs to the field of material synthesis, and particularly relates to a loofah-shaped covalent organic framework material and a preparation method and application thereof. Background Art

[0002] With the rapid development of industry and agriculture, various pollutants such as heavy metal ions are emitted and present in various environmental media, posing a significant threat to the ecological environment and human health. Currently, the main methods for removing heavy metals and other pollutants include electrochemical methods, membrane separation, bioremediation, and adsorption. Compared with other methods, adsorption has attracted widespread attention due to its low cost and good selectivity. However, common adsorbents such as activated carbon often have limited adsorption capacity. Therefore, the preparation of new adsorbents with large specific surface areas and high adsorption capacities has always been a major challenge.

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

[0004] Currently, common covalent organic frameworks are typically synthesized using high-temperature methods, which require stringent conditions. Furthermore, there is limited control over the material's morphology, which is a key factor influencing its adsorption properties. Summary of the Invention

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

[0006] To achieve the above object, the technical solution adopted by the present invention is: A method for preparing a loofah-like covalent organic framework material: i) uniformly dispersing a monomer C3 containing an aldehyde functional group and a triazine structure, a monomer C2 containing an amino group and a thiol group, a catalyst, and a regulating agent in an organic solvent to obtain a dispersion; ii) allowing the dispersion to undergo a reversible reaction at 20-50° C. for 1-5 days, thereby connecting the building blocks of the two monomers to obtain a corresponding product. The product is washed and dried to obtain a sponge-like covalent organic framework material.

[0007] The monomer C3 is a substance containing a triazine structure and at least three aldehyde groups; the monomer C2 is a substance containing an amino group and a thiol group, and the number of the amino group and the number of the thiol group are at least two or more.

[0008] Preferably, the monomer C3 contains a triazine structure and 3-6 aldehyde groups; the monomer C2 contains an amino group and a thiol group, and the number of the amino group and the number of the thiol group are 2-4 respectively.

[0009] More preferably, the monomer C3 is 2,4,6-tris(4-vinylphenyl)-1,3,5-triazine; and the monomer C2 is 2,5-dimercaptophenyl-1,4-diamine.

[0010] The molar ratio of the monomer C3 to the monomer C2 is 1:8 to 8:1, preferably 1:4 to 4:1, and more preferably 2:3.

[0011] The final concentration of the catalyst in the dispersion is 0.15-1 mM, preferably 0.6 mM; the volume ratio of the regulator to the dispersion is 1:100-1:400, preferably 1:200.

[0012] The catalyst is acetic acid and / or cesium carbonate, preferably acetic acid; the regulator is aniline or p-phenylenediamine and / or phenylenediamine, preferably aniline.

[0013] The organic solvent is one or more of mesitylene, 1,4-dioxane, n-butanol, o-dichlorobenzene or acetonitrile.

[0014] The organic solvent is mesitylene and 1,4-dioxane, and the volume ratio of the two is (0.1-1): (0.1-1).

[0015] A loofah-like covalent organic framework material prepared by the method, wherein the method prepares a covalent organic framework material having a loofah-like microstructure, rich pore structure, large specific surface area and high thermal stability, and containing a large amount of S element and many active sites.

[0016] An application of the loofah sponge-shaped covalent organic framework material, and an application of the loofah sponge-shaped covalent organic framework material in adsorbing heavy metals in the environment.

[0017] Application of the loofah-like covalent organic framework material in adsorbing heavy metals in water.

[0018] The advantages of the present invention are: (1) The preparation method of the present invention can synthesize covalent organic framework materials at room temperature. The reaction conditions are mild and the preparation is convenient, avoiding the harsh conditions of high-temperature synthesis. At the same time, the micromorphology can be controlled to prepare a covalent organic framework material with a loofah-like structure.

[0019] (2) The loofah-like covalent organic framework material prepared by the present invention has the advantages of rich pores and large specific surface area, which are conducive to the adsorption of various pollutants. It also has high thermal stability and can be used in different environments.

[0020] (3) The sponge gourd-like covalent organic framework material prepared by the present invention contains rich S elements, which can provide more active sites for heavy metal ions, which is beneficial to the adsorption of heavy metal pollutants and is expected to achieve the simultaneous adsorption and removal of multiple heavy metal pollutants. It can also be used as a single-atom carrier and has good application prospects in catalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the synthesis and structure of the loofah-like covalent organic framework material prepared at room temperature.

[0022] Figure 2 The Fourier transform infrared (FT-IR) spectra of two monomers and the synthesized loofah-like covalent organic framework material.

[0023] Figure 3 This is the thermogravimetric analysis diagram of the loofah-like covalent organic framework material. The horizontal axis represents temperature and the vertical axis represents the percentage of mass loss.

[0024] Figure 4 This is the EDS spectrum of the loofah-like covalent organic framework material.

[0025] Figure 5 This is a scanning electron microscope image of the loofah-like covalent organic framework material.

[0026] Figure 6 This is the XRD pattern of the loofah-like covalent organic framework material.

[0027] Figure 7 This is the adsorption thermodynamic curve of the loofah-like covalent organic framework material.

[0028] Figure 8 This is the adsorption kinetic curve of the loofah-like covalent organic framework material. DETAILED DESCRIPTION

[0029] In order to make the contents of the present invention easier to understand, the technical solutions of the present invention are further described below with reference to examples. It should be pointed out that the specific implementation methods described here are only for illustrating and explaining the present invention, but the present invention is not limited thereto.

[0030] The preparation method of the present invention is simple and easy to operate. The covalent organic framework material prepared by the present invention has a sponge-like structure, rich pore structure, large specific surface area, and high thermal stability. It also contains a large amount of sulfur element, has many active sites, and has a high adsorption capacity. It can be used as an adsorbent for the adsorption and removal of pollutants such as heavy metal ions, and also has good application prospects in single-atom loading.

[0031] The sponge gourd-like covalent organic framework material of the present invention has the characteristics of rich pores, large specific surface area, and many active sites. It has a high adsorption capacity and can be used as an adsorbent for the adsorption and removal of pollutants such as heavy metal ions, and can also be used for the loading of single atoms. Example 1

[0032] 25 mg of 2,4,6-tris(4-vinylphenyl)-1,3,5-triazine, 23.37 mg of 2,5-dimercaptophenyl-1,4-diamine, 1 mL of 1,4-dioxane, 1 mL of mesitylene, 0.1 mL of 6M acetic acid and 10 μL of aniline were added to a 10 mL centrifuge tube, ultrasonically dispersed for 2 minutes, and then sealed. The reaction was carried out at room temperature for 72 hours. Then, the obtained solid material was washed three times with acetone, 50 mL each time, and then washed three times with ethanol, 50 mL each time. Subsequently, the washed solid material was vacuum dried at 100 ° C for 24 hours to obtain a brown powdery loofah-like covalent organic framework material, see Figure 1 .

[0033] The obtained sponge gourd-like covalent organic framework material was analyzed by Fourier transform infrared spectroscopy (FT-IR). Figure 2 As shown. Figure 2 It can be seen that the corresponding functional groups of the aldehyde group and the amino group are weakened or disappear, and a new C=N double bond is generated.

[0034] The obtained sponge gourd-like covalent organic framework material was subjected to thermogravimetric analysis, and the results were as follows: Figure 3 As shown. Figure 3 It can be seen that the sponge gourd-like covalent organic framework material has high thermal stability within 400°C.

[0035] The obtained sponge gourd-like covalent organic framework material was subjected to EDS spectrum analysis, and the results were as follows: Figure 4 As shown. Figure 4 It can be seen that the loofah-like covalent organic framework material contains rich S element.

[0036] The obtained sponge gourd-like covalent organic framework material was analyzed by scanning electron microscopy. Figure 5 As shown. Figure 5It can be seen that the covalent organic framework material presents a loofah-like structure with high porosity and an average size of about 10 μm.

[0037] The obtained sponge gourd-like covalent organic framework material was subjected to X-ray diffraction analysis, and the results were as follows: Figure 6 As shown. Figure 6 It can be seen that the loofah-like covalent organic framework material has certain crystallinity. Example 2

[0038] Weigh 2 mg of the sponge gourd-like covalent organic framework material prepared in Example 1 and add it to a series of heavy metal Hg solutions with a concentration of 10-200 mg / L. 2+ The standard solution (each concentration standard solution is 10mL) was shaken and adsorbed at room temperature for 24 hours. After shaking, 5mL was taken with a syringe and filtered with a filter to measure the Hg content in the residual solution. 2+ Concentration. Test results are as follows Figure 7 As shown, the sponge gourd-like covalent organic framework material is used for heavy metal Hg 2+ The maximum adsorption capacity is about 600 mg / g.

[0039] Weigh 10 mg of the sponge gourd-like covalent organic framework material prepared in Example 1 and add it to 50 mL of 20 mg / L Hg 2+ The standard solution was shaken and 2 mL was taken with a syringe after 2, 4, 6, 8, 10, 20, 30, 50, and 100 minutes respectively. The residual liquid was filtered and the Hg content was detected. 2+ Concentration. Test results are as follows Figure 8 As shown in Figure 2, with the increase of time, Hg 2+ The concentration gradually decreases, and the adsorption effect will be better when the time continues to extend.

[0040] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a sponge gourd-like covalent organic framework material, characterized in that: i) uniformly dispersing a monomer C3 containing an aldehyde functional group and a triazine structure, a monomer C2 containing an amino group and a thiol group, a catalyst, and a regulating agent in an organic solvent to obtain a dispersion; ii) allowing the dispersion to undergo a reversible reaction at 20-50° C. for 1-5 days, thereby connecting the building blocks of the two monomers to obtain a corresponding product. The product is washed and dried to obtain a sponge-like covalent organic framework material.

2. The method for preparing the sponge gourd-shaped covalent organic framework material according to claim 1, wherein: The monomer C3 contains a triazine structure and at least three aldehyde groups; the monomer C2 contains an amino group and a thiol group, and the number of the amino group and the number of the thiol group are at least two.

3. The method for preparing the sponge gourd-shaped covalent organic framework material according to claim 2, wherein: The monomer C3 is 2,4,6-tris(4-vinylphenyl)-1,3,5-triazine; and the monomer C2 is 2,5-dimercaptophenyl-1,4-diamine.

4. The method for preparing the sponge gourd-shaped covalent organic framework material according to any one of claims 1 to 3, wherein: The molar ratio of the monomer C3 to the monomer C2 is 1:8-8:1; the final concentration of the catalyst in the dispersion is 0.15-1 mM; and the volume ratio of the regulator to the dispersion is 1:100-1:

400.

5. The method for preparing the sponge gourd-shaped covalent organic framework material according to claim 4, wherein: The catalyst is acetic acid and / or cesium carbonate, and the regulator is aniline and / or p-phenylenediamine.

6. The method for preparing the sponge gourd-shaped covalent organic framework material according to claim 1, wherein: The organic solvent is one or more of mesitylene, 1,4-dioxane, n-butanol, o-dichlorobenzene or acetonitrile.

7. The method for preparing the sponge gourd-shaped covalent organic framework material according to claim 6, wherein: The organic solvent is mesitylene and 1,4-dioxane, and the volume ratio of the two is (0.1-1): (0.1-1).

8. A loofah-like covalent organic framework material prepared by the preparation method of claim 1, characterized in that: The preparation method of claim 1 prepares a covalent organic framework material having a loofah-like microstructure, rich pore structure, large specific surface area and high thermal stability, and containing a large amount of S elements and many active sites.

9. An application of the sponge gourd-like covalent organic framework material according to claim 8, characterized in that: The invention relates to an application of the loofah-like covalent organic framework material in adsorbing heavy metals in the environment.

10. The use of the sponge gourd-shaped covalent organic framework material according to claim 9, characterized in that: Application of the loofah-like covalent organic framework material in adsorbing heavy metals in water.

Images