Method for in-situ preparation of covalent organic framework mixed matrix membrane and application

Abstract

The invention relates to the technical field of gas separation membranes, in particular to a method for in-situ preparation of a covalent organic framework (COFs) mixed matrix membrane in a polymer matrix and application of the covalent organic framework (COFs) mixed matrix membrane in CO2 separation. According to the method, a COFs precursor is directly introduced into a polymer matrix, and a solvent molecule is utilized to promote the precursor to generate a Schiff base reaction, so that in-situ generation of COFs nanoparticles in the polymer matrix is realized, and the covalent organic framework mixed matrix membrane is prepared. The method provided by the invention not only promotes the uniform dispersion of COFs in a polymer matrix, but also significantly enhances the interfacial compatibility between COFs and the polymer matrix, and the prepared membrane material shows excellent long-term stability. The method is simple in process, and the prepared covalent organic framework mixed matrix membrane has important application potential in the field of CO2 separation.

Description

[0001] Technical field: The present invention relates to a method for in-situ preparation of a covalent organic framework mixed matrix membrane and its application, belonging to the field of gas separation membranes.

[0002] Background technology: With the widespread use of fossil fuels, the concentration of CO2 in the atmosphere continues to rise, leading to a series of climate crises such as rising sea levels and intensified greenhouse effects, which have brought a heavy burden to the ecological environment. At present, CO2 capture methods mainly include cryogenic distillation and absorption methods, but these methods are faced with huge energy consumption and serious environmental pollution. In contrast, membrane separation technology has gradually demonstrated its unique advantages in the field of CO2 separation. With its low energy consumption, environmentally friendly operation process and excellent separation effect, it has become an important development direction in the field of CO2 separation in the future.

[0003] Organic polymer membranes dominate the market due to their good mechanical properties, easy processing and low cost. However, there is often a trade-off between permeability and selectivity in polymer materials, which is limited by the Robeson upper limit, making it difficult to improve both at the same time. An effective solution is to add fillers such as carbon nanotubes, zeolites, zeolites, and metal organic framework materials to the polymer matrix to prepare mixed matrix membranes. However, the interface compatibility problem between these inorganic fillers and polymer materials is a difficulty in preparing mixed matrix membranes with stable structure and high gas capture efficiency.

[0004] Therefore, the present invention designs a mixed matrix membrane with covalent organic frameworks (COFs) as fillers, directly adds COFs precursors to the polymer matrix, realizes the in-situ generation of COFs nanoparticles, and thus prepares COFs mixed matrix membranes (MMMs). This method not only promotes the uniform dispersion of COFs in the polymer matrix, but also enhances the interface compatibility of COFs and the polymer matrix, bringing broad application prospects to the field of CO2 separation.

[0005] Invention content: The present invention provides a method for in-situ preparation of covalent organic framework mixed matrix membranes. The method is simple to operate and can significantly enhance the interfacial compatibility between COFs and polymer matrices to achieve effective separation of CO2. The technical solution of the present invention is as follows:

[0006] (1) The polyamide-polyether block copolymer Pebax 2533 was dried in a vacuum oven at 80° C. for one day to remove moisture before use.

[0007] (2) Pebax 2533 was added to the solvent and stirred, and refluxed and condensed at 80° C. for 2 h to completely dissolve Pebax 2533 in the solvent, thereby preparing a Pebax 2533 solution with a certain mass fraction.

[0008] (3) Weigh a certain mass of the Pebax 2533 solution prepared in step (2), add a certain mass of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde, and perform ultrasonic treatment to ensure that the aldehyde monomer is completely dissolved in the Pebax 2533 solution. Then add a certain mass of p-phenylenediamine, and the aldehyde monomer and the amine monomer react to form COF by Schiff base reaction. Ultrasonic treatment is performed for 30 minutes, and stirring is performed for 12 hours to allow the COF to be evenly dispersed in the Pebax 2533 solution to obtain a COF / Pebax 2533 casting solution.

[0009] (4) Pour the COF / Pebax 2533 film casting solution into a polytetrafluoroethylene culture dish, place it on a flat surface to ensure uniform film formation, and dry it in an oven at 100°C for 24 h.

[0010] (5) Soak the film prepared in step (4) in solvent for 12 h, and change the solvent three times to ensure that the unreacted COF precursor is completely removed.

[0011] (6) The film obtained in step (5) was placed in a vacuum oven at 120°C and dried for 24 hours.

[0012] The solvent in the above step (2) is n-butanol, ethanol, N,N-dimethylacetamide, preferably N,N-dimethylacetamide.

[0013] The certain mass fraction of Pebax 2533 solution in the above step (2) is 3wt%, 5wt%, preferably 3wt%.

[0014] The certain mass of the Pebax 2533 solution of step (2) described in the above step (3) is 5 g.

[0015] The certain mass of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde in the above step (3) is 1 mg to 12 mg.

[0016] The certain mass of p-phenylenediamine in the above step (3) is 0.77 mg to 9.2 mg.

[0017] The solvent described in the above step (5) is methanol, ethanol, dioxane, mesitylene, preferably dioxane.

[0018] The method of the present invention adopts the method of directly adding the precursor of the covalent organic framework into the polymer matrix to prepare the covalent organic framework mixed matrix membrane in situ. Compared with the prior art, the present invention has the following advantages:

[0019] (1) This method is easy to operate and has high film-making efficiency;

[0020] (2) The interfacial compatibility between the covalent organic framework and the polymer matrix is ​​effectively enhanced, and the prepared membrane material exhibits excellent long-term stability.

[0021] Description of the drawings: Figure 1 (a) is a surface scanning electron micrograph of COF MMMs prepared in Example 1, Figure 1 (b) is a surface scanning electron micrograph of COF MMMs prepared in Example 2, Figure 1 (c) is a surface scanning electron micrograph of COF MMMs prepared in Example 3, Figure 1 (d) is a surface scanning electron micrograph of the COF MMMs prepared in Example 4.

[0022] Figure 2 This is a scanning electron microscope image of the cross section of COF MMMs prepared in Example 3.

[0023] Figure 3 This is a surface scanning electron microscope image of the pure Pebax film prepared in Comparative Example 1.

[0024] Figure 4 This is a diagram of the long-term operating stability of COF MMMs prepared in Example 3.

[0025] Specific implementation method: The technical solution of the present invention is further described in detail below in combination with specific examples based on the accompanying drawings.

[0026] Example 1

[0027] (1) Weigh 5 g of Pebax 2533 and dry it in a vacuum oven at 80°C for one day to remove moisture before use.

[0028] (2) Weigh 0.6 g of Pebax 2533 and 20 g of N,N-dimethylacetamide, pour into a 50 mL three-necked flask, stir and reflux at 80° C. for 2 h to completely dissolve Pebax 2533 in the solvent, and prepare a 3 wt % Pebax 2533 solution.

[0029] (3) Weigh 1 mg of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde and dissolve it in 5 g of Pebax 2533 solution. Perform ultrasonic treatment to ensure that the aldehyde monomer is completely dissolved in the Pebax 2533 solution. Then weigh 0.77 mg of p-phenylenediamine and pour it into the above solution. The aldehyde monomer and the amine monomer react with Schiff base to generate COF. Ultrasonic treatment is performed for 30 minutes and stirring is performed for 12 hours to ensure that COF can be evenly dispersed in the Pebax 2533 solution to obtain COF / Pebax 2533 casting solution.

[0030] (4) Pour the COF / Pebax 2533 casting solution into a polytetrafluoroethylene culture dish with a diameter of 5 cm, place it on a flat surface to ensure uniform film formation, and dry it in an oven at 100°C for 24 h.

[0031] (5) Measure 40 mL of dioxane and soak the film prepared in step (4) for 12 hours. Replace the solvent every 4 hours to ensure that the unreacted COF precursor is completely removed.

[0032] (6) The film obtained in step (5) was placed in a vacuum oven at 120°C and dried for 24 hours.

[0033] The membrane prepared in this embodiment was subjected to gas permeation test and the separation performance of CO2 and N2 was tested, wherein the volume ratio of CO2 to N2 was 15 / 85, the inlet pressure was 2 bar, and the test temperature was 35° C. The test results showed that the permeability coefficient of CO2 was 221.6 Barrer, the permeability coefficient of N2 was 10.3 Barrer, and the separation selectivity of CO2 and N2 was 21.4.

[0034] Example 2

[0035] (1) Weigh 5 g of Pebax 2533 and dry it in a vacuum oven at 80°C for one day to remove moisture before use.

[0036] (2) Weigh 0.6 g of Pebax 2533 and 20 g of N,N-dimethylacetamide, pour into a 50 mL three-necked flask, stir and reflux at 80° C. for 2 h to completely dissolve Pebax 2533 in the solvent, and prepare a 3 wt % Pebax 2533 solution.

[0037] (3) Weigh 5 mg of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde and dissolve it in 5 g of Pebax 2533 solution. Perform ultrasonic treatment to ensure that the aldehyde monomer is completely dissolved in the Pebax 2533 solution. Then weigh 3.8 mg of p-phenylenediamine and pour it into the above solution. The aldehyde monomer and the amine monomer react with Schiff base to generate COF. Ultrasonic treatment is performed for 30 minutes and stirring is performed for 12 hours to ensure that COF can be evenly dispersed in the Pebax 2533 solution to obtain COF / Pebax 2533 casting solution.

[0038] (4) Pour the COF / Pebax 2533 casting solution into a polytetrafluoroethylene culture dish with a diameter of 5 cm, place it on a flat surface to ensure uniform film formation, and dry it in an oven at 100°C for 24 h.

[0039] (5) Measure 40 mL of dioxane and soak the film prepared in step (4) for 12 hours. Replace the solvent every 4 hours to ensure that the unreacted COF precursor is completely removed.

[0040] (6) The film obtained in step (5) was placed in a vacuum oven at 120°C and dried for 24 hours.

[0041] The membrane prepared in this embodiment was subjected to gas permeation test and the separation performance of CO2 and N2 was tested, wherein the volume ratio of CO2 to N2 was 15 / 85, the inlet pressure was 2 bar, and the test temperature was 35° C. The test results showed that the permeability coefficient of CO2 was 268.9 Barrer, the permeability coefficient of N2 was 13.0 Barrer, and the separation selectivity of CO2 and N2 was 20.7.

[0042] Example 3

[0043] (1) Weigh 5 g of Pebax 2533 and dry it in a vacuum oven at 80°C for one day to remove moisture before use.

[0044] (2) Weigh 0.6 g of Pebax 2533 and 20 g of N,N-dimethylacetamide, pour into a 50 mL three-necked flask, stir and reflux at 80° C. for 2 h to completely dissolve Pebax 2533 in the solvent, and prepare a 3 wt % Pebax 2533 solution.

[0045] (3) Weigh 10 mg of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde and dissolve it in 5 g of Pebax 2533 solution. Perform ultrasonic treatment to ensure that the aldehyde monomer is completely dissolved in the Pebax 2533 solution. Then weigh 7.7 mg of p-phenylenediamine and pour it into the above solution. The aldehyde monomer and the amine monomer react with Schiff base to generate COF. Ultrasonic treatment is performed for 30 minutes and stirring is performed for 12 hours to ensure that COF can be evenly dispersed in the Pebax 2533 solution to obtain COF / Pebax 2533 casting solution.

[0046] (4) Pour the COF / Pebax 2533 casting solution into a polytetrafluoroethylene culture dish with a diameter of 5 cm, place it on a flat surface to ensure uniform film formation, and dry it in an oven at 100°C for 24 h.

[0047] (5) Measure 40 mL of dioxane and soak the film prepared in step (4) for 12 hours. Replace the solvent every 4 hours to ensure that the unreacted COF precursor is completely removed.

[0048] (6) The film obtained in step (5) was placed in a vacuum oven at 120°C and dried for 24 hours.

[0049] The membrane prepared in this embodiment was subjected to gas permeation test and the separation performance of CO2 and N2 was tested, wherein the volume ratio of CO2 to N2 was 15 / 85, the inlet pressure was 2 bar, and the test temperature was 35° C. The test results showed that the permeability coefficient of CO2 was 313.4 Barrer, the permeability coefficient of N2 was 13.9 Barrer, and the separation selectivity of CO2 and N2 was 22.6.

[0050] Example 4

[0051] (1) Weigh 5 g of Pebax 2533 and dry it in a vacuum oven at 80°C for one day to remove moisture before use.

[0052] (2) Weigh 0.6 g of Pebax 2533 and 20 g of N,N-dimethylacetamide, pour into a 50 mL three-necked flask, stir and reflux at 80° C. for 2 h to completely dissolve Pebax 2533 in the solvent, and prepare a 3 wt % Pebax 2533 solution.

[0053] (3) Weigh 12 mg of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde and dissolve it in 5 g of Pebax 2533 solution. Perform ultrasonic treatment to ensure that the aldehyde monomer is completely dissolved in the Pebax 2533 solution. Then weigh 9.2 mg of p-phenylenediamine and pour it into the above solution. The aldehyde monomer and the amine monomer react with Schiff base to generate COF. Ultrasonic treatment is performed for 30 minutes and stirring is performed for 12 hours to ensure that COF can be evenly dispersed in the Pebax 2533 solution to obtain COF / Pebax 2533 casting solution.

[0054] (4) Pour the COF / Pebax 2533 casting solution into a polytetrafluoroethylene culture dish with a diameter of 5 cm, place it on a flat surface to ensure uniform film formation, and dry it in an oven at 100°C for 24 h.

[0055] (5) Measure 40 mL of dioxane and soak the film prepared in step (4) for 12 hours. Replace the solvent every 4 hours to ensure that the unreacted COF precursor is completely removed.

[0056] (6) The film obtained in step (5) was placed in a vacuum oven at 120°C and dried for 24 hours.

[0057] The membrane prepared in this embodiment was subjected to gas permeation test and the separation performance of CO2 and N2 was tested, wherein the volume ratio of CO2 to N2 was 15 / 85, the inlet pressure was 2 bar, and the test temperature was 35° C. The test results showed that the permeability coefficient of CO2 was 251.9 Barrer, the permeability coefficient of N2 was 12.5 Barrer, and the separation selectivity of CO2 and N2 was 20.2.

[0058] Comparative Example 1

[0059] (1) Weigh 5 g of Pebax 2533 and dry it in a vacuum oven at 80°C for one day to remove moisture before use. (2) Weigh 0.6 g of Pebax 2533 and 20 g of N,N-dimethylacetamide, pour them into a 50 mL three-necked flask, stir and reflux condense at 80°C for 2 h to completely dissolve Pebax 2533 in the solvent, and prepare a 3 wt% Pebax 2533 solution.

[0060] (3) Weigh 5 g of Pebax 2533 casting solution and pour it into a polytetrafluoroethylene culture dish with a diameter of 5 cm. Place it on a flat surface to ensure uniform film formation and dry it in an oven at 100 °C for 24 h.

[0061] (4) Measure 40 mL of dioxane and soak the film prepared in step (3) for 12 hours. Replace the solvent every 4 hours to ensure that the unreacted COF precursor is completely removed.

[0062] (5) The film obtained in step (4) was placed in a vacuum oven at 120°C and dried for 24 hours.

[0063] The membrane prepared in this comparative example was subjected to gas permeation test and the separation performance of CO2 and N2 was tested, wherein the volume ratio of CO2 to N2 was 15 / 85, the inlet pressure was 2 bar, and the test temperature was 35° C. The test results showed that the permeability coefficient of CO2 was 214.9 Barrer, the permeability coefficient of N2 was 10.7 Barrer, and the separation selectivity of CO2 and N2 was 20.1.

[0064] Figure 1 Surface scanning electron micrographs of COF MMMs prepared in Examples 1 to 4. Figure 1 (c) It can be seen that the COF particles are evenly distributed in the polymer matrix. Figure 1 It can be seen from (a) and (b) that too little COF may not be conducive to fully filling the entire polymer film. Figure 1 (d) It can be seen that too many COF particles tend to agglomerate, which is not conducive to the formation of a well-structured mixed matrix membrane.

[0065] Figure 2 This is a scanning electron micrograph of a cross section of COF MMMs prepared in Example 3. From the figure, it can be seen that the COF particles are evenly distributed in the polymer matrix and have good interface compatibility.

[0066] Figure 3 This is a surface scanning electron microscope image of the pure Pebax film prepared in Comparative Example 1. From the image, it can be seen that the surface of the pure Pebax film is smooth and dense.

[0067] Figure 4: is the long-term operation stability diagram of COF MMMs prepared in Example 3. It can be seen from the figure that there is no obvious change in gas permeability coefficient and selectivity, and the prepared COF MMMs have excellent long-term stability.

Claims

1. A method for in situ preparation of a covalent organic framework mixed matrix membrane, characterized in that: The following steps are involved: (1) drying the polyamide-polyether block copolymer Pebax 2533 in a vacuum oven at 80° C. for 24 hours to remove moisture and setting aside; (2) adding the dried Pebax 2533 to the solvent, stirring and reflux condensing at 80° C. for 2 hours to prepare a Pebax 2533 solution; (3) weighing the Pebax 2533 solution obtained in step (2), adding 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and p-phenylenediamine, and promoting the Schiff base reaction by ultrasound and stirring to obtain a COF / Pebax 2533 casting solution; (4) Pour the COF / Pebax 2533 casting solution into a polytetrafluoroethylene petri dish and dry it in an oven at 100 °C for 24 h; (5) soaking the film prepared in step (4) in a solvent for 12 hours, and changing the solvent three times to remove unreacted precursor; (6) Dry the film obtained in step (5) in a vacuum oven at 120°C for 24 hours.

2. The method according to claim 1, characterized in that: The solvent described in step (2) is n-butanol, ethanol, N,N-dimethylacetamide, preferably N,N-dimethylacetamide.

3. The method according to claim 1, characterized in that: The mass fraction of the Pebax 2533 solution in step (2) is 3 wt % to 5 wt %, preferably 3 wt %.

4. The method according to claim 1, characterized in that: The mass of the Pebax 2533 solution described in step (3) is 5 grams.

5. The method according to claim 1, characterized in that: The mass of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde described in step (3) is 1 mg to 12 mg.

6. The method according to claim 1, characterized in that: The mass of p-phenylenediamine described in step (3) is 0.77 mg to 9.2 mg.

7. The method according to claim 1, characterized in that: The solvent described in step (5) is methanol, ethanol, dioxane, mesitylene, among which dioxane is preferred. A method for in-situ preparation of a covalent organic framework mixed matrix membrane, characterized in that: It is prepared by the preparation method of claims 1 to 7 and is used for CO2 / N2 separation.

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