New normal-temperature normal-pressure imine-linked covalent organic framework rapid preparation method

Abstract

A novel normal-temperature normal-pressure imine-linked covalent organic framework rapid preparation method relates to the technical field of covalent organic framework materials, and comprises the following steps: 1) dissolving an aldehyde group monomer and a fatty amine regulator in a tetrahydrofuran and toluene composite solvent; 2) dissolving an amino monomer in a composite solvent of tetrahydrofuran and toluene; and 3) mixing the solution obtained in the step 1), the solution obtained in the step 2) and an acetic acid aqueous solution for reaction, and then washing and drying to obtain the COFs material. The COFs are prepared in a simpler mode based on a new nucleation-growth mechanism, and the technical problems that in the prior art, COFs preparation means are tedious, the product crystallinity is poor, and batch preparation is difficult can be solved. According to the method, the synthesis cost and time are remarkably reduced, the yield and crystallinity of the COFs are improved, and a foundation is laid for industrial application of the COFs.

Description

Technical Field

[0001] The invention relates to the technical field of covalent organic framework materials, and in particular to a novel method for rapidly preparing an imine-connected covalent organic framework at room temperature and pressure. Background Art

[0002] Covalent organic frameworks (COFs), as a class of ordered porous crystalline materials synthesized using topological design, have the advantages of large specific surface area, good structural stability, low density and strong designability of chemical structure within the pores. They have broad application prospects in catalysis, separation, sensing and semiconductors.

[0003] Since the discovery of COFs materials, the synthesis of imine-linked COFs has mostly adopted a high-temperature, high-pressure solvent thermal strategy due to the limitation of the "self-healing" mechanism. In order to prevent the oxidation of monomers and the occurrence of side reactions during the long reaction process, ampoules are often used as reaction containers and prepared on a milligram scale. Therefore, these stringent reaction requirements limit the industrial mass production of imine COFs, and the synthesis cost is extremely high.

[0004] In order to achieve industrial production, a series of improved strategies have been developed, such as ionothermal method, hydrothermal method, microwave heating method, mechanical synthesis method and ultrasound-assisted synthesis method, etc. Although these methods are based on the solvothermal method and have made some improvements in reaction time, heating method and solvent selection, they have not completely overcome the technical difficulties such as difficulty in scale-up, poor reaction uniformity and low crystallinity of the obtained products. Summary of the invention

[0005] The purpose of the present invention is to solve the above problems in the prior art, provide a new method for rapid preparation of imine-linked covalent organic frameworks at room temperature and pressure, prepare COFs in a simpler way based on a new nucleation-growth mechanism, and solve the technical problems of cumbersome COFs preparation methods, poor product crystallinity and difficulty in batch preparation in the prior art. The present invention not only significantly reduces the synthesis cost and time, but also improves the yield and crystallinity of COFs, laying a foundation for its industrial application.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] A novel method for rapidly preparing an imine-linked covalent organic framework at room temperature and pressure comprises the following steps:

[0008] 1) dissolving the aldehyde monomer and the fatty amine regulator in a composite solvent of tetrahydrofuran and toluene;

[0009] 2) dissolving the amino monomer in a composite solvent of tetrahydrofuran and toluene;

[0010] 3) The solution obtained in step 1), the solution obtained in step 2) and an acetic acid aqueous solution are mixed and reacted, and then washed and dried to obtain a COFs material.

[0011] The aldehyde monomer is one of trialdehyde phloroglucinol, 2,5-divinyl-1,4-benzenedicarbaldehyde, 2,5-dimethoxybenzene-1,4-dicarboxaldehyde, 2,5-hydroxybenzene-1,4-dicarboxaldehyde, trimesic acid and 1,3,5-tris(4-formylphenyl)benzene.

[0012] The amino monomer is one of p-phenylenediamine, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 1,3,5-tris(4-aminophenyl)benzene and tetra-4-aminostyrene.

[0013] The fatty amine regulator includes one of ethylamine, n-propylamine and n-butylamine, and the molar ratio of the aldehyde monomer to the fatty amine regulator is 1-10:1.

[0014] The molar ratio of the aldehyde group of the aldehyde monomer to the amino group of the amino monomer is 1:1.

[0015] The concentration of the acetic acid aqueous solution is 3M to 17.5M.

[0016] In the composite solvent, the volume ratio of tetrahydrofuran to toluene is 3-8:1.

[0017] The reaction conditions of the present invention are normal temperature and pressure, and the reaction time is 12 to 50 hours.

[0018] The washing is carried out by using tetrahydrofuran and ethanol in sequence.

[0019] The invention discloses a method for preparing COFs under normal temperature and pressure atmosphere, wherein a suitable solvent is used to improve the solubility of the monomer, and a suitable fatty amine is used as a regulator to adjust the reaction rate. The thermodynamic nucleation-growth process of COFs nanocrystals in the control system is controlled, and then the product is washed and dried to obtain the COFs material.

[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0021] First, the present invention uses a fatty amine regulator and a specific solvent to prepare imine-linked covalent organic frameworks in large quantities at room temperature and pressure, and has good universality for the preparation of imine COFs with different substituents and topological structures. Secondly, compared with the traditional high-temperature reaction system, this system does not require long-term high-temperature reaction, which reduces energy consumption and does not require vacuum or inert gas protection to prevent monomer oxidation. Thirdly, compared with the aqueous phase reaction system, the monomers and oligomers of this system have good solubility, which is conducive to the crystallization of COFs, so that the product has higher crystallinity and specific surface area. Finally, the reaction equipment is simple and does not require any complex external equipment, which is conducive to industrial scale-up production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 (a) is a schematic diagram of the preparation process of imine COFs materials; (b) is the prepared imine COFs materials with different topological structures.

[0023] Figure 2 From top to bottom in the figure are Fourier transform infrared spectra of the monomer 1,3,5-tri(4-aminophenyl)benzene, 2,5-dimethoxyterephthalaldehyde and the prepared covalent organic framework COF-TBDM used in Example 1.

[0024] Figure 3 This is the powder X-ray diffraction pattern of the covalent organic framework COF-TBDM prepared in Example 1.

[0025] Figure 4 This is a nitrogen adsorption-desorption curve of the covalent organic framework COF-TBDM prepared in Example 1. DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0027] Figure 1 (a) is the preparation process of imine COFs materials. First, the monomer containing aldehyde groups and the fatty amine regulator are dissolved in a composite solvent of tetrahydrofuran and toluene. At the same time, the monomer containing amino groups is also dissolved in the same composite solvent, and acetic acid aqueous solution is added to catalyze the reaction at room temperature and pressure. After the reaction is completed, the imine COFs material is finally obtained after post-processing steps such as washing and drying. Figure 1 (b) is an imine COFs material with different topological structures prepared by the above steps. This method can be used to prepare a variety of imine COFs materials with different structures. The preparation example of COF-TBDM is given below.

[0028] Example 1

[0029] Step 1: Take 2.93 g of 2,5-dimethoxyterephthalaldehyde (CAS: 7310-97-6) and 0.11 g of ethylamine aqueous solution (ethylamine concentration is 65 wt%~70 wt%) and dissolve them in 200 mL of tetrahydrofuran / toluene mixed solvent with a volume ratio of 4:1.

[0030] Step 2: Dissolve 3.51 g of 1,3,5-tri(4-aminophenyl)benzene (CAS: 118727-34-7) in 100 mL of tetrahydrofuran / toluene co-solvent with a volume ratio of 4:1.

[0031] Step 3: Add the solution obtained in step 1 and 40 mL of 6 mol / L acetic acid aqueous solution dropwise to the solution in step 2, perform ultrasonic treatment at room temperature for 2 minutes, and allow to react for 2 days.

[0032] Step 4: After the reaction, the powder was filtered and then washed with tetrahydrofuran and ethanol to remove the unreacted small molecules. After drying at 80 °C, a dark yellow powder COF-TBDM was obtained with a product yield of 90%.

[0033] The Fourier transform infrared spectra of the monomers used and the products obtained in Example 1 are as follows: Figure 2 As shown in the product spectrum, a new -1 The absorption peaks at 3100-3500 cm -1 and 1670~1690 cm -1 The absorption peaks of the amine NH and aldehyde -C=O were weakened, confirming that the monomers were condensed to form an imine-linked chemical structure.

[0034] The powder X-ray diffraction spectrum of the product obtained in Example 1 is as follows: Figure 3 As shown, the characteristic peaks of the product's X-ray diffraction are consistent with those reported in the literature, indicating that highly crystalline COFs are formed, indicating that COF-TBDM is successfully prepared in this example.

[0035] pass Figure 4 The nitrogen adsorption-desorption curve of COF-TBDM is shown, and the calculated specific surface area is: 2716m 2 / g.

[0036] The present invention uses a specific solvent and regulator combination to synthesize high specific area and high crystallinity COFs through a nucleation-growth process at room temperature and pressure. The present invention selects a specific polar solvent combination and an amine-based regulator to improve the solubility of the reaction monomers and oligomers, so that COFs can spontaneously nucleate and grow at room temperature and pressure without inert gas protection, avoiding the harsh reaction conditions such as high temperature, oxygen-free, and long time required by traditional preparation strategies. The reaction can be carried out at room temperature and pressure without vacuum or inert gas protection, which is conducive to scale-up production and has industrial production potential.

[0037] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A new method for rapid preparation of imine-linked covalent organic frameworks at room temperature and pressure, characterized in that: The following steps are involved: 1) dissolving the aldehyde monomer and the fatty amine regulator in a composite solvent of tetrahydrofuran and toluene; 2) dissolving the amino monomer in a composite solvent of tetrahydrofuran and toluene; 3) The solution obtained in step 1), the solution obtained in step 2) and an acetic acid aqueous solution are mixed and reacted, and then washed and dried to obtain a COFs material.

2. A novel method for rapidly preparing an imine-linked covalent organic framework at room temperature and pressure as claimed in claim 1, characterized in that: The aldehyde monomer is one of trialdehyde phloroglucinol, 2,5-divinyl-1,4-benzenedicarbaldehyde, 2,5-dimethoxybenzene-1,4-dicarboxaldehyde, 2,5-hydroxybenzene-1,4-dicarboxaldehyde, trimesic acid and 1,3,5-tris(4-formylphenyl)benzene.

3. A novel method for rapidly preparing an imine-linked covalent organic framework at room temperature and pressure as claimed in claim 1, characterized in that: The amino monomer is one of p-phenylenediamine, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 1,3,5-tris(4-aminophenyl)benzene and tetra-4-aminostyrene.

4. A novel method for rapidly preparing an imine-linked covalent organic framework at room temperature and pressure as claimed in claim 1, characterized in that: The fatty amine regulator includes one of ethylamine, n-propylamine and n-butylamine, and the molar ratio of the aldehyde monomer to the fatty amine regulator is 1-10:

1.

5. A novel method for rapidly preparing an imine-linked covalent organic framework at room temperature and pressure as claimed in claim 1, characterized in that: The molar ratio of the aldehyde group of the aldehyde monomer to the amino group of the amino monomer is 1:

1.

6. A novel method for rapidly preparing an imine-linked covalent organic framework at room temperature and pressure as claimed in claim 1, characterized in that: The concentration of the acetic acid aqueous solution is 3M to 17.5M.

7. A novel method for rapidly preparing an imine-linked covalent organic framework at room temperature and pressure as claimed in claim 1, characterized in that: In the composite solvent, the volume ratio of tetrahydrofuran to toluene is 3-8:

1.

8. A novel method for rapidly preparing an imine-linked covalent organic framework at room temperature and pressure as claimed in claim 1, characterized in that: The reaction conditions are normal temperature and pressure.

9. A novel method for rapidly preparing an imine-linked covalent organic framework at room temperature and pressure as claimed in claim 1, characterized in that: The reaction time is 12~50h.

10. A novel method for rapidly preparing an imine-linked covalent organic framework at room temperature and pressure as claimed in claim 1, characterized in that: The washing is carried out by using tetrahydrofuran and ethanol in sequence.

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