A method for rapidly preparing imine covalent organic framework membranes and applications thereof

Abstract

This invention belongs to the field of covalent organic framework (COF) separation membranes and discloses a method for rapidly preparing imine covalent organic framework membranes and their applications. The preparation method includes the following steps: Step 1: Preparation of an amorphous membrane; Step 2: Conversion of the amorphous membrane to a COF membrane. The preparation method provided by this invention overcomes the problems of slow rate and high requirements in the traditional imine COF membrane preparation process, and has the characteristics of simple preparation method, few steps, high repeatability, and easy scale-up. Applying the prepared COF membrane to the nanofiltration process achieves precise molecular separation and high solvent permeation characteristics, providing a new approach for the large-scale preparation and industrial application of COF membranes.

Description

Technical Field

[0001] This invention relates to a method for rapidly preparing imine covalent organic framework membranes and its application, belonging to the field of covalent organic framework membranes. Background Technology

[0002] Covalent organic frameworks (COFs) are widely recognized as candidates for next-generation high-performance membrane materials due to their uniform pore size, high stability, and strong tunability. Compared to traditional polymer membranes, they exhibit unique advantages. Their regular and uniform pores hold promise for overcoming the trade-off effect of solvent permeability and solute selectivity. Furthermore, the designable pore size provides strong adaptability to different application scenarios, and their applications in water treatment, gas separation, and energy storage have been reported. Imine COF membranes, due to their relatively simple synthesis, abundant monomers, and strong tunability of functional groups, have become the most studied COF membranes to date. Imine COF membranes have significant application potential in water treatment, especially in molecular separation and molecular / ion separation. However, the insoluble and infusible nature of imine COFs leads to poor processability; therefore, recent research has focused primarily on the preparation of imine COF membranes. Existing methods for preparing imine COF membranes include in-situ growth, interfacial polymerization (including solid-gas interfacial polymerization, liquid-liquid interfacial polymerization and liquid-gas interfacial polymerization), layer-by-layer self-assembly and disorder-to-order transformation. However, the formation of a well-ordered, highly crystalline structure in imine COF membranes often requires a long time and harsh growth conditions, which greatly limits the large-scale preparation of COF membranes.

[0003] Dynamic imine bonds, guided by dynamic imine chemistry, serve as the guiding principle for the preparation of imine COFs. The reversibility of imine bonds ensures self-repair and self-correction during the imine COF preparation process, thereby forming a thermodynamically stable framework structure under certain conditions. The preparation of imine COF membranes is similar to that of imine COFs, but due to the slow crystallization process and the poor film-forming properties of COFs, the preparation process of COF membranes is often more complex and prone to defects leading to poor separation performance. Therefore, the rapid preparation of highly crystalline, defect-free COF membranes is a significant challenge. Summary of the Invention

[0004] To address the aforementioned technical problems in the existing technology, this invention provides a method for rapidly preparing imine covalent organic framework membranes, the specific technical solution of which is as follows:

[0005] A method for rapidly preparing imine covalent organic framework membranes includes the following steps:

[0006] Step 1: Preparation of amorphous membranes

[0007] 1.8 mmol of pyromellitic methyl ether and 8.6 mmol of aniline were dissolved in 10 mL of ethanol and reacted at 80 °C for 24 h to prepare the aldehyde monomer BTPA. The aldehyde monomer BTPA was ultrasonically dissolved in N,N-dimethylacetamide to prepare an aldehyde monomer solution. The amine monomer p-phenylenediamine (PDA) and different amounts of polyethyleneimine (PEI) were ultrasonically dissolved in N,N-dimethylacetamide to prepare an amine monomer solution. The aldehyde monomer solution and the amine monomer solution were further mixed and ultrasonically homogenized, and then allowed to stand for several hours. The mixed monomer solution was cast onto a glass slide, and after solvent evaporation, an amorphous film was obtained.

[0008] Step 2: Conversion of amorphous membrane to COF membrane

[0009] The amorphous membrane obtained in step one is placed in a mixed solution of solvent and catalyst, and heat-treated at 65°C for a certain time to obtain a COF-PEIa(b) membrane, where a represents the PEI content and b represents the heat treatment time.

[0010] Furthermore, in step one, the molecular weight of PEI is one or more of 600, 800, 1800, 3000, 10000, 30000 or 50000.

[0011] Furthermore, the amount of PEI used in the steps is 10 μL, 20 μL, 30 μL, 40 μL or 50 μL.

[0012] Furthermore, the solvent evaporation time in step one is controlled to be 1 hour, 3 hours, 6 hours, 12 hours, or 24 hours.

[0013] Furthermore, the volume ratio of solvent to catalyst used in the heat treatment process in step two is 2:8, 4:6, 6:4, or 8:2.

[0014] Furthermore, the heat treatment time in step two is 1 hour, 3 hours, 6 hours, 12 hours, or 24 hours.

[0015] Application of the covalent organic framework membrane prepared by the method in molecular and / or molecular ion separation.

[0016] The preparation method of this invention uses aniline-modified trimesin as the aldehyde-based monomer obtained in the COF film preparation process, and p-phenylenediamine as the amino monomer. Polyethyleneimine is incorporated into the COF through imine bonds to improve film-forming properties and fill defects. An amorphous film is obtained by evaporating the solvent using a simple casting method, and the COF film is obtained through a hydrothermal process for rapid crystallization. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a rapid COF membrane preparation method.

[0018] Figure 2These are the XRD patterns of amorphous membranes and COF membranes. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] Example 1

[0021] The method for rapidly preparing imine covalent organic framework membranes according to the present invention includes the following steps:

[0022] Step 1: Preparation of the amorphous membrane: Weigh 291.85 mg of trimesin and 783.65 μL of aniline, dissolve them in 10 mL of ethanol, react at 80 °C for 24 h, and separate the powder to obtain the aldehyde monomer. Dissolve the aldehyde monomer in 0.5 mL of N,N-dimethylacetamide using ultrasonication to prepare an aldehyde monomer solution; dissolve the amine monomer p-phenylenediamine and 20 μL of polyethyleneimine (molecular weight 600) in 0.5 mL of N,N-dimethylacetamide using ultrasonication in the same molar ratio as the aldehyde monomer to prepare an amine monomer solution; mix the amine monomer and aldehyde monomer solutions thoroughly, allow them to stand for a period of time, cast them onto a glass slide, and evaporate the solvent to obtain the amorphous membrane.

[0023] Step 2: Conversion of amorphous membrane to COF membrane: The amorphous membrane obtained in step 1 was placed in a mixed solution of solvent and catalyst in a ratio of 6:4 and heat-treated at 65°C for 3 hours to obtain COF-PEI20(3) membrane.

[0024] The COF-PEI20(3) membrane obtained in Example 1 was used for nanofiltration separation, and the separation performance was: pure water flux of 121.76 Lm. -2 h -1 bar -1 The flux of Congo red solution (concentration of 100 ppm) was 115.89 L / m³. -2 h -1 bar -1 The retention rate of Congo Red was 98.48%.

[0025] Example 2

[0026] The preparation process is as follows:

[0027] Step 1: Preparation of the amorphous membrane: Weigh 291.85 mg of trimesin and 783.65 μL of aniline, dissolve them in 10 mL of ethanol, react at 80 °C for 24 h, and separate the powder to obtain the aldehyde monomer. Dissolve the aldehyde monomer in 0.5 mL of N,N-dimethylacetamide using ultrasonication to prepare an aldehyde monomer solution. Dissolve the amine monomer p-phenylenediamine and 30 μL of polyethyleneimine (molecular weight 600) in 0.5 mL of N,N-dimethylacetamide using ultrasonication to prepare an amine monomer solution. Mix the amine monomer and aldehyde monomer solutions thoroughly, allow them to stand for a period of time, cast them onto a glass slide, and evaporate the solvent to obtain the amorphous membrane.

[0028] Step 2: Conversion of amorphous membrane to COF membrane: The amorphous membrane obtained in Step 1 is placed in a mixed solution of solvent and catalyst in a ratio of 6:4 and heat-treated at 65°C for 3 hours to obtain COF-PEI30(3) membrane.

[0029] The COF-PEI30(3) membrane obtained in Example 1 was used for nanofiltration separation, and the separation performance was: pure water flux of 233.81 Lm. -2 h -1 bar -1 The flux of Congo red solution (concentration of 100 ppm) was 215.67 L / m³. -2 h -1 bar -1 The retention rate of Congo Red was 98.69%.

[0030] Example 3

[0031] The preparation process is as follows:

[0032] Step 1: Preparation of the amorphous membrane: Weigh 291.85 mg of trimesin and 783.65 μL of aniline, dissolve them in 10 mL of ethanol, react at 80 °C for 24 h, and separate the powder to obtain the aldehyde monomer. Dissolve the aldehyde monomer in 0.5 mL of N,N-dimethylacetamide using ultrasonication to prepare an aldehyde monomer solution; dissolve the amine monomer p-phenylenediamine and 40 μL of polyethyleneimine (molecular weight 600) in 0.5 mL of N,N-dimethylacetamide using ultrasonication in the same molar ratio as the aldehyde monomer to prepare an amine monomer solution; mix the amine monomer and aldehyde monomer solutions thoroughly, allow them to stand for a period of time, cast them onto a glass slide, and evaporate the solvent to obtain the amorphous membrane.

[0033] Step 2: Conversion of amorphous membrane to COF membrane: The amorphous membrane obtained in Step 1 is placed in a mixed solution of solvent and catalyst in a ratio of 6:4, and heat-treated at 65°C for 3 hours to obtain COF-PEI40(3) membrane.

[0034] The COF-PEI40(3) membrane obtained in Example 2 was used for nanofiltration separation, and the separation performance was: pure water flux of 344.09 Lm.-2 h -1 bar -1 The flux of Congo red solution (concentration of 100 ppm) was 291.90 L / m³. -2 h -1 bar -1 The retention rate of Congo Red was 99.89%.

[0035] Example 4

[0036] The preparation process is as follows:

[0037] Step 1: Preparation of the amorphous membrane: Weigh 291.85 mg of trimesin and 783.65 μL of aniline, dissolve them in 10 mL of ethanol, react at 80 °C for 24 h, and separate the powder to obtain the aldehyde monomer. Dissolve the aldehyde monomer in 0.5 mL of N,N-dimethylacetamide using ultrasonication to prepare an aldehyde monomer solution. Dissolve the amine monomer p-phenylenediamine and 50 μL of polyethyleneimine (molecular weight 600) in 0.5 mL of N,N-dimethylacetamide using ultrasonication in the same molar ratio as the aldehyde monomer to prepare an amine monomer solution. Mix the amine monomer and aldehyde monomer solutions thoroughly, allow them to stand for a period of time, cast them onto a glass slide, and evaporate the solvent to obtain the amorphous membrane.

[0038] Step 2: Conversion of amorphous membrane to COF membrane: The amorphous membrane obtained in Step 1 is placed in a mixed solution of solvent and catalyst in a ratio of 6:4 and heat-treated at 65°C for 3 hours to obtain COF-PEI50(3) membrane.

[0039] The COF-PEI50(3) membrane obtained in Example 3 was used for nanofiltration separation, and the separation performance was: pure water flux of 405.05 Lm. -2 h -1 bar -1 The flux of Congo red solution (concentration of 100 ppm) was 353.38 L / m³. -2 h -1 bar -1 The retention rate of Congo Red was 98.56%.

[0040] Example 5

[0041] The preparation process is as follows:

[0042] Step 1: Preparation of the amorphous membrane: Weigh 291.85 mg of trimesin and 783.65 μL of aniline, dissolve them in 10 mL of ethanol, react at 80 °C for 24 h, and separate the powder to obtain the aldehyde monomer. Dissolve the aldehyde monomer in 0.5 mL of N,N-dimethylacetamide using ultrasonication to prepare an aldehyde monomer solution; dissolve the amine monomer p-phenylenediamine and 40 μL of polyethyleneimine (molecular weight 600) in 0.5 mL of N,N-dimethylacetamide using ultrasonication in the same molar ratio as the aldehyde monomer to prepare an amine monomer solution; mix the amine monomer and aldehyde monomer solutions thoroughly, allow them to stand for a period of time, cast them onto a glass slide, and evaporate the solvent to obtain the amorphous membrane.

[0043] Step 2: Conversion of amorphous membrane to COF membrane: The amorphous membrane obtained in Step 1 was placed in a mixed solution of solvent and catalyst in a ratio of 6:4 and heat-treated at 65°C for 12 hours to obtain COF-PEI40(12) membrane.

[0044] The COF-PEI40(12) membrane obtained in Example 4 was used for nanofiltration separation, and the separation performance was: pure water flux of 651.76 Lm. -2 h -1 bar -1 The flux of Congo red solution (concentration of 100 ppm) was 567.34 L / m³. -2 h -1 bar -1 The retention rate of Congo Red was 88.11%.

[0045]

[0046] Table 1. Nanofiltration performance of COF membranes.

Claims

1. A method for rapidly preparing imine covalent organic framework membranes, characterized in that... Includes the following steps: Step 1: Preparation of amorphous membranes 1.8 mmol of pyromellitic methyl ether and 8.6 mmol of aniline were dissolved in 10 mL of ethanol and reacted at 80 °C for 24 h to prepare the aldehyde monomer BTPA. The aldehyde monomer BTPA was ultrasonically dissolved in N,N-dimethylacetamide to prepare an aldehyde monomer solution. The amine monomer p-phenylenediamine (PDA) and different amounts of polyethyleneimine (PEI) were ultrasonically dissolved in N,N-dimethylacetamide to prepare an amine monomer solution. The aldehyde monomer solution and the amine monomer solution were further mixed and ultrasonically homogenized, and then allowed to stand for several hours. The mixed monomer solution was cast onto a glass slide, and after solvent evaporation, an amorphous film was obtained. Step 2: Conversion of amorphous membrane to COF membrane The amorphous membrane obtained in step one is placed in a mixed solution of solvent and catalyst and heat-treated at 65 °C for a certain time to obtain COF-PEIa(b) membrane, where a represents the PEI content and b represents the heat treatment time.

2. The method for rapidly preparing imine covalent organic framework membranes as described in claim 1, characterized in that: In step one, the molecular weight of PEI is one or more of the following: 600, 800, 1800, 3000, 10000, 30000 or 50000.

3. The method for rapidly preparing imine covalent organic framework membranes as described in claim 1, characterized in that: In step one, the amount of PEI used is 10 μL, 20 μL, 30 μL, 40 μL, or 50 μL.

4. The method for rapidly preparing imine covalent organic framework membranes as described in claim 1, characterized in that: In step one, the solvent evaporation time is controlled to be 1 h, 3 h, 6 h, 12 h or 24 h.

5. The method for rapidly preparing imine covalent organic framework membranes as described in claim 1, characterized in that: In step two, the volume ratio of solvent to catalyst used in the heat treatment process is 2:8, 4:6, 6:4, or 8:

2.

6. The method for rapidly preparing imine covalent organic framework membranes as described in claim 1, characterized in that: The heat treatment time in step two is 1 h, 3 h, 6 h, 12 h or 24 h.

7. The application of the imine covalent organic framework membrane prepared by the method according to any one of claims 1-6 in molecular separation.

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