A new method for rapid preparation of imine-linked covalent organic frameworks at room temperature and pressure

Abstract

A new method for rapidly preparing an imine-linked covalent organic framework at room temperature and pressure relates to the technical field of covalent organic framework materials, comprising the following steps: 1) dissolving an aldehyde monomer and a fatty amine regulator in a composite solvent of tetrahydrofuran and toluene; 2) dissolving an amino monomer in a composite solvent of tetrahydrofuran and toluene; 3) mixing the solution obtained in step 1) and the solution obtained in step 2) with an acetic acid aqueous solution for reaction, followed by washing and drying to obtain a COFs material. The present invention is based on a new nucleation-growth mechanism to prepare COFs in a simpler manner, and can solve the technical problems of the prior art in the complicated preparation methods of COFs, poor product crystallinity, and difficulty in batch preparation. The present invention not only significantly reduces the synthesis cost and time, but also increases the yield and crystallinity of COFs, laying the foundation for their industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of covalent organic framework materials, and in particular to a novel method for rapidly preparing an imine-linked 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, the synthesis of imine-linked COFs has largely relied on high-temperature, high-pressure solvothermal strategies due to their inherent limitations in self-healing mechanisms. To prevent monomer oxidation and side reactions during prolonged reactions, ampoules are often used as reaction vessels, and preparations are often performed on a milligram-scale. Consequently, these stringent reaction requirements have limited the industrial mass production of imine-linked COFs and have resulted in extremely high synthesis costs.

[0004] To achieve industrial production, a series of improved strategies have been developed, including ionothermal, hydrothermal, microwave heating, mechanical synthesis, and ultrasound-assisted synthesis. Although these methods all build upon solvothermal methods with improvements in reaction time, heating methods, and solvent selection, none of them fully overcome technical challenges such as scale-up difficulties, poor reaction uniformity, and low product crystallinity. Summary of the Invention

[0005] The present invention aims to address the aforementioned problems in the prior art by providing a novel method for rapidly preparing imine-linked covalent organic frameworks at room temperature and pressure. This method, based on a novel nucleation-growth mechanism, allows for a simpler preparation of COFs. This method addresses the technical issues of the prior art, such as the cumbersome preparation methods, poor product crystallinity, and difficulty in batch production. This method not only significantly reduces synthesis cost and time, but also increases the yield and crystallinity of COFs, laying the foundation for their industrial application.

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

[0007] A new method for rapid preparation of imine-linked covalent organic frameworks 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-benzenedicarboxaldehyde, 2,5-dimethoxybenzene-1,4-dicarboxaldehyde, 2,5-hydroxybenzene-1,4-dicarboxaldehyde, trimesicarboxaldehyde 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 normal pressure, and the reaction time is 12 to 50 hours.

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

[0019] The present invention discloses a method for preparing COFs under normal temperature and pressure. The method uses a suitable solvent to increase the solubility of the monomer and a suitable fatty amine as a regulator to adjust the reaction rate. The thermodynamic nucleation and growth process of COF nanocrystals in the control system is then controlled. The product is then washed and dried to produce the COF material.

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

[0021] First, the present invention utilizes aliphatic amine regulators and specific solvents to prepare imine-linked covalent organic frameworks in large quantities at room temperature and pressure, and has good universality for the preparation of imine-based COFs with different substituents and topological structures. Secondly, compared with traditional high-temperature reaction systems, this system does not require long-term high-temperature reactions, which reduces energy consumption while eliminating the need for vacuum or inert gas protection to prevent monomer oxidation. Thirdly, compared with aqueous reaction systems, the monomers and oligomers in this system have good solubility, which is conducive to the crystallization of COFs, resulting in products with higher crystallinity and specific surface area. Finally, the reaction equipment is simple and does not require any complex external equipment, which facilitates 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 the Fourier transform infrared spectra of the monomer 1,3,5-tris(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 with reference to the accompanying drawings and embodiments.

[0027] Figure 1 Figure (a) illustrates the preparation process for imine-based COFs. First, an aldehyde-containing monomer and a fatty amine modifier are dissolved in a co-solvent of tetrahydrofuran and toluene. Simultaneously, an amino-containing monomer is dissolved in the same co-solvent. Acetic acid is then added as a catalyst, and the reaction proceeds at room temperature and pressure. After the reaction is complete, post-processing steps such as washing and drying are performed to obtain the imine-based COFs. Figure 1 (b) shows imine COFs materials 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 following is an example of the preparation of COF-TBDM.

[0028] Example 1

[0029] Step 1: Dissolve 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%) in 200 mL of a tetrahydrofuran / toluene co-solvent with a volume ratio of 4:1.

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

[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, ultrasonicate 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 unreacted small molecules. The powder was dried at 80°C to obtain COF-TBDM as a dark yellow powder with a 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, the product spectrum clearly shows a new -1 The absorption peaks at 3100~3500 cm -1 and 1670~1690 cm -1 The absorption peaks of the amino 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 pattern of the product obtained in Example 1 is as follows: Figure 3 As shown, the characteristic X-ray diffraction peaks of the product 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 utilizes a specific solvent and modifier combination to synthesize high-area, highly crystalline COFs through a nucleation-growth process at room temperature and pressure. The invention utilizes a specific polar solvent combination and an amine-based modifier to improve the solubility of the reacting monomers and oligomers, enabling spontaneous nucleation and growth of COFs at room temperature and pressure, without the protection of an inert gas. This avoids the harsh reaction conditions of high temperature, oxygen deprivation, and long reaction times required by traditional preparation strategies. The reaction can be carried out at room temperature and pressure, without the need for vacuum or inert gas protection, facilitating scale-up and showing potential for industrial production.

[0037] The above content is 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 method for rapidly preparing an imine-linked covalent organic framework at room temperature and pressure, characterized in that: The following steps are involved: 1) dissolving 2,5-dimethoxybenzene-1,4-dicarbaldehyde and a fatty amine regulator in a composite solvent of tetrahydrofuran and toluene, wherein the volume ratio of tetrahydrofuran to toluene is 3 to 8:1; the fatty amine regulator comprises one of ethylamine, n-propylamine, and n-butylamine, and the molar ratio of 2,5-dimethoxybenzene-1,4-dicarbaldehyde to the fatty amine regulator is 1 to 10:1; 2) dissolving 1,3,5-tris(4-aminophenyl)benzene in a co-solvent of tetrahydrofuran and toluene; the molar ratio of the aldehyde group of 2,5-dimethoxybenzene-1,4-dicarbaldehyde to the amino group of 1,3,5-tris(4-aminophenyl)benzene is 1:1; 3) mixing the solution obtained in step 1), the solution obtained in step 2) and a 3M to 17.5M aqueous acetic acid solution at room temperature and pressure for 12 to 50 hours, and then washing and drying to obtain a COFs material.

2. The method for rapidly preparing an imine-linked covalent organic framework at room temperature and pressure according to claim 1, wherein: The washing is carried out using tetrahydrofuran and ethanol in sequence.

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