Ion liquid modified ZnBDC / polymer hybrid matrix membrane for gas separation and its preparation method

Abstract

This invention discloses an ionic liquid-modified ZnBDC / polymer hybrid matrix membrane for gas separation and its preparation method. It solves the technical problem of defects and non-selective interfacial voids in hybrid matrix membranes caused by interfacial compatibility issues of metal-organic framework fillers in organic matrices. The method includes steps such as preparing ionic liquid-modified ZnBDC and preparing the ionic liquid-modified ZnBDC / polymer hybrid matrix membrane. The preparation process of this invention is mild and controllable, the raw materials are readily available, and the filler has good dispersibility. The prepared hybrid matrix membrane exhibits excellent separation performance in CO2 / CH4 and CO2 / N2 separation systems.

Description

Technical Field

[0001] This invention belongs to the field of gas membrane separation technology, specifically relating to an ionic liquid modified ZnBDC / polymer hybrid matrix membrane for gas separation and its preparation method. Background Technology

[0002] In recent years, human activities have led to a year-on-year increase in atmospheric CO2 concentration, especially the burning of fossil fuels used for power generation, transportation, oil recycling, cement production, and metallurgy, which has exacerbated climate problems such as the greenhouse effect and sea-level rise.

[0003] Membrane separation technology offers a clean, economical, easy-to-operate, and efficient separation process, which is beneficial for large-scale industrial applications. Membrane materials, as the core of gas separation membranes, determine the membrane's separation efficiency and lifespan. Mixed matrix membranes (MMMs) are typically composed of inorganic packing materials and polymer matrices. The inorganic materials are mainly added as a dispersed phase to the organic polymer, combining the advantages of both inorganic materials and organic polymers to enhance the membrane's gas separation performance.

[0004] Metal-organic frameworks (MOFs), as a class of porous materials, possess advantages such as high specific surface area and the ability to be functionalized, making them highly promising inorganic fillers for gas separation. Physical blending is currently the most common method for preparing mixed matrix membranes. However, poor interfacial compatibility between inorganic fillers and organic polymers often leads to defects and non-selective interfacial voids, severely limiting the separation efficiency of mixed matrix membranes. Furthermore, uneven distribution of fillers within the membrane makes them more prone to aggregation, reducing their surface energy and thus severely limiting the filler content in mixed matrix membranes, even compromising the membrane's structural integrity, which also restricts the development of mixed matrix membranes to some extent. Summary of the Invention

[0005] This application addresses the technical problem of defects and non-selective interfacial voids in mixed matrix membranes caused by interfacial compatibility issues of metal-organic framework (MOF) fillers in organic matrices. It proposes a method for modifying the metal-organic framework material ZnBDC with the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate. Specifically, ZnBDC, a Zn-based MOF material prepared with zinc ions, possesses high CO2 adsorption capacity and specific surface area. Introducing ZnBDC into the membrane provides additional gas transport channels, enhancing the CO2 mass transfer process within the membrane. Secondly, the ionic liquid improves the compatibility between the metal-organic framework filler and the polymer, achieving uniform dispersion of the metal-organic framework filler in the mixed matrix membrane and strengthening the construction of CO2 diffusion channels within the membrane. Furthermore, the imidazole and sulfonic acid groups in the ionic liquid enhance the membrane's CO2 solubility through Lewis acid-base interactions. By synergistically strengthening the membrane's dissolution-diffusion mechanism, the prepared ionic liquid-modified ZnBDC / polymer mixed matrix membrane exhibits excellent gas separation performance.

[0006] This invention is achieved through the following technical solution:

[0007] This invention provides a method for preparing ZnBDC, a metal-organic framework material modified with 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, an ionic liquid.

[0008] The method for preparing the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate-modified metal-organic framework material ZnBDC provided by the present invention includes the following steps:

[0009] 1) Dissolve the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate in a solvent and stir to disperse it evenly to obtain an ionic liquid solution;

[0010] 2) Disperse ZnBDC (Zn-terephthalic acid MOFs) material in a solvent and sonicate it to make it uniformly dispersed to obtain ZnBDC dispersion;

[0011] 3) Add the ZnBDC dispersion to the above ionic liquid solution and sonicate to ensure thorough and uniform mixing;

[0012] 4) The resulting mixture was reacted under stirring to obtain ionic liquid modified ZnBDC;

[0013] In steps 1) and 2) of the above method, the solvent can specifically be at least one of methanol and ethanol.

[0014] In step 1), the stirring time can be 5-20 minutes, specifically 10 minutes;

[0015] The ratio of the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate to the solvent in the ionic liquid solution can be 0.5g:10mL-0.5g:20mL, specifically 0.5g:15mL;

[0016] In step 2) of the above method, the ratio of ZnBDC material to solvent can be 0.5g:5mL-0.5g:15mL, specifically 0.5g:10mL;

[0017] The duration of the ultrasonic treatment can be 0.1-1 hour, specifically 0.5 hours;

[0018] In step 3) of the above method, the mass ratio of the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate in the ionic liquid solution to the ZnBDC in the ZnBDC dispersion can be 1:1 to 1:4, specifically 1:1;

[0019] The duration of the ultrasonic treatment can be 0.1-1 hour, specifically 0.5 hours;

[0020] In step 4) of the above method, the reaction temperature can be 30-90℃, specifically 60℃, and the time can be 12-36h, specifically 24h.

[0021] The above method further includes repeatedly centrifuging and washing the product obtained after the reaction, and then drying the reaction product to remove residual solvent to obtain ionic liquid modified ZnBDC.

[0022] The drying process can specifically be vacuum drying, with a temperature of 60°C and a duration of 24 hours.

[0023] The present invention also provides an ionic liquid modified ZnBDC / polymer hybrid matrix membrane, wherein the ionic liquid modified ZnBDC / polymer hybrid matrix membrane is made from ionic liquid modified ZnBDC and polymer materials as raw materials;

[0024] Specifically, the ionic liquid-modified ZnBDC can be a ZnBDC metal-organic framework material modified with ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate.

[0025] The polymer material is a polymer matrix membrane material, which can be selected from at least one of the following: polyimide PI, polyetheretherketone SPEEK, polyamide Pebax, and cellulose acetate CA;

[0026] The mass ratio of ionic liquid-modified ZnBDC to polymer materials is 0.5:100-10:100;

[0027] Preferably, the thickness of the ionic liquid modified ZnBDC / polymer hybrid matrix membrane is 40μm-70μm, and it is in the form of a flat sheet membrane.

[0028] The present invention also provides a method for preparing the above-mentioned ionic liquid modified ZnBDC / polymer hybrid matrix membrane.

[0029] The method for preparing an ionic liquid-modified ZnBDC / polymer hybrid matrix membrane provided by the present invention includes the following steps:

[0030] 1) Disperse ionic liquid modified ZnBDC powder in a certain amount of solvent to form an inorganic filler dispersion;

[0031] 2) Dissolve the polymer material in a solvent to form an organic casting solution;

[0032] 3) The above inorganic filler dispersion is mixed with the organic casting solution, ultrasonically treated, and then stirred to ensure uniform dispersion;

[0033] 4) Using the obtained ionic liquid-modified ZnBDC / polymer mixture as the casting solution, it was coated onto the ultra-flat surface, and the solvent was evaporated by heating to form a film;

[0034] 5) Peel off the obtained mixed matrix membrane material and dry it to obtain the ionic liquid modified ZnBDC / polymer mixed matrix membrane.

[0035] In steps 1) and 2) of the above method, the solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetone, water, ethanol, and chloroform;

[0036] In step 1), the mass concentration of ionic liquid modified ZnBDC in the inorganic filler dispersion is 0.001-0.005 g / mL, specifically 0.001 g / mL or 0.002 g / mL;

[0037] In step 2), the polymer material is a polymer matrix membrane material, which can be selected from at least one of the following: polyimide PI, polyether ether ketone SPEEK, polyamide Pebax, and cellulose acetate CA;

[0038] In the organic casting solution, the mass concentration of the polymer material is 0.05-0.1 g / mL, specifically 0.1 g / mL;

[0039] In step 3), the mass ratio of the ionic liquid modified ZnBDC in the inorganic filler dispersion to the polymer material in the organic casting solution can be 0.5:100-10:100, specifically 1:100 or 2:100.

[0040] The duration of the ultrasonic treatment can be 0.5-2 hours, specifically 0.5 hours.

[0041] The stirring time can be 12-24 hours, specifically 24 hours;

[0042] In step 4), the coating can be at least one of scraping and dripping, specifically dripping.

[0043] In step 5), the drying is vacuum drying. The temperature of the vacuum drying can be 150-250℃, specifically 150℃, and the time can be 10-40h, specifically 24h or 36h.

[0044] The present invention also provides the application of the above-mentioned ionic liquid modified ZnBDC / polymer hybrid matrix membrane in CO2 separation.

[0045] The CO2 membrane separation is preferably CO2 / CH4 and CO2 / N2 membrane separation.

[0046] The present invention also provides a CO2 capture device comprising the above-mentioned ionic liquid modified ZnBDC / polymer hybrid matrix membrane.

[0047] The advantages of this invention are: the mixed matrix membrane of this invention has a significant effect on gas separation, can effectively separate carbon dioxide, and the preparation process is simple and controllable, the conditions are mild, the raw materials are readily available, and the preparation method has a certain degree of universality.

[0048] A preferred hybrid matrix membrane of the present invention (matrix is ​​PI) has a CO2 permeability coefficient of 11 Barrer (matrix membrane is 6.8), a carbon dioxide / nitrogen separation coefficient of 33.2 (matrix membrane is 25), and a carbon dioxide / methane separation coefficient of 42.2 (matrix membrane is 29.8).

[0049] Modifying the metal-organic framework ZnBDC with ionic liquids improved the compatibility between the inorganic filler and the polymer matrix, enhanced the filler's distribution within the polymer matrix, and strengthened the construction of CO2 diffusion channels within the membrane. Simultaneously, the interaction between CO2 and the trifluoromethyl, sulfonic acid, and imidazole groups in the ionic liquid can enhance the membrane's CO2 solubility. Attached Figure Description

[0050] Figure 1 The infrared spectrum of the ionic liquid modified ZnBDC (IL@ZnBDC) prepared in Example 2 of this invention.

[0051] Figure 2 The images show scanning electron microscope (SEM) images and structural schematic diagrams of the ionic liquid-modified ZnBDC prepared in Example 2 and the mixed matrix membranes prepared in Examples 3 and 4 of this invention. Image (a) shows the surface (b), cross-sectional (c), and cross-sectional (d) images of the ionic liquid-modified ZnBDC, the mixed matrix membrane prepared in Example 3, and the mixed matrix membrane prepared in Example 4. Detailed Implementation

[0052] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0053] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0054] In the following embodiments of the present invention, CO2, CH4, and N2 are all high-purity gases. The gas separation evaluation device in the following embodiments is a Langguang VAC-V2 differential pressure gas permeation analyzer.

[0055] Example 1: Preparation of ZnBDC material

[0056] Dissolve 0.1g of NaOH in 10mL of methanol and stir for 10min to disperse it evenly to obtain a NaOH alcohol solution;

[0057] Dissolve 0.4 g of Zn(NO3)2·6H2O in 10 mL of N,N-dimethylformamide, add the above NaOH alcohol solution, and sonicate for 0.5 h to obtain zinc hydroxide solution;

[0058] Add 200 mL of 0.035 g / mL terephthalic acid solution to the above solution and sonicate for 2 h;

[0059] The white precipitate obtained by filtration was washed repeatedly with ethanol and dried under vacuum at 60°C for 24 hours to obtain ZnBDC material.

[0060] Example 2: Preparation of Ionic Liquid Modified ZnBDC

[0061] A method for preparing ionic liquid-modified ZnBDC includes the following steps:

[0062] Dissolve 0.5 g of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate in 15 mL of ethanol and stir for 10 min to disperse it evenly.

[0063] 0.5 g of ZnBDC prepared in Example 1 was dispersed in 10 mL of ethanol, sonicated for 0.5 h, and then added to the above 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ethanol solution. The mixture was stirred at 60 °C for 24 h.

[0064] After the reaction was completed, the product was repeatedly centrifuged and washed, and then the reaction product was vacuum dried in a vacuum oven at 60°C for 24 hours.

[0065] Figure 1 The infrared spectrum of the prepared ionic liquid modified ZnBDC (IL@ZnBDC).

[0066] Figure 2 Image (a) shows the prepared ionic liquid-modified ZnBDC.

[0067] Example 3: Preparation of ionic liquid modified ZnBDC polyimide mixed matrix membrane

[0068] 0.005 g of the ionic liquid-modified ZnBDC powder prepared in Example 2 was dispersed in 5 mL of N,N-dimethylacetamide to prepare a filler dispersion. 0.5 g of polyimide polymer was dissolved in 5 mL of N,N-dimethylacetamide to prepare an organic casting solution. The dispersion and casting solution were mixed to form a mixed matrix membrane casting solution, and the mixture was ultrasonicated for 0.5 h and then stirred for approximately 24 h to ensure uniform dispersion. The resulting ionic liquid-modified ZnBDC / polymer mixture was used as the casting solution and drop-coated onto an ultra-flat glass surface. The surface was heated at 60°C for 24 h on a heating plate to allow the solvent to evaporate slowly. Subsequently, the membrane was placed in a vacuum oven and vacuum-dried at 150°C for 36 h. The membrane thickness was 55 μm. The exfoliated membrane material was placed in a gas permeameter, and its gas separation performance was tested at 35°C and 1 bar. The carbon dioxide gas flux was 9 Barrer, the carbon dioxide / methane separation performance was 35.8, and the carbon dioxide / nitrogen separation performance was 29.

[0069] Figure 2 (b) is a SEM image of the prepared hybrid matrix film, and (c) is a cross-sectional image.

[0070] Example 4: Preparation of ionic liquid modified ZnBDC / polyimide hybrid matrix membrane

[0071] 0.01 g of the prepared ionic liquid-modified ZnBDC powder was dispersed in 5 mL of N,N-dimethylacetamide to prepare a filler dispersion. 0.5 g of polyimide polymer was dissolved in 5 mL of N,N-dimethylacetamide to prepare an organic casting solution. The dispersion and casting solution were mixed to form a mixed matrix membrane casting solution, and the mixture was ultrasonicated for 0.5 h and then stirred for approximately 24 h to ensure uniform dispersion. The resulting ionic liquid-modified ZnBDC / polymer mixture was used as the casting solution and drop-coated onto an ultra-flat glass surface. The surface was heated at 60 °C for 24 h on a heating plate to allow the solvent to evaporate slowly. Subsequently, the membrane was placed in a vacuum oven and vacuum-dried at 150 °C for 36 h. The exfoliated membrane material (57 μm thickness) was placed in a gas permeameter, and its gas separation performance was tested at 35 °C and 1 bar. The carbon dioxide gas flux was 11 Barrer, the carbon dioxide / methane separation performance was 42.2, and the carbon dioxide / nitrogen separation performance was 33.2.

[0072] Figure 2 (d) is a SEM cross-sectional image of the hybrid matrix membrane.

[0073] Comparative Example 1: Preparation of Polyimide Film

[0074] A method for preparing a polyimide film includes the following steps:

[0075] 0.5 g of polyimide powder was dissolved in 10 mL of N,N-dimethylacetamide and stirred for approximately 24 h to ensure uniform dispersion. The dispersion was then drop-coated onto a clean, flat glass surface and heated at 60 °C for 24 h on a heating plate to allow the solvent to evaporate slowly. The membrane was then placed in a vacuum oven and vacuum-dried at 150 °C for 36 h. The exfoliated membrane material (54 μm thick) was placed in a gas permeameter, and its gas separation performance was tested at 35 °C and 1 bar. The carbon dioxide flux was 6.8 Barrer, the carbon dioxide / methane separation performance was 29.8, and the carbon dioxide / nitrogen separation performance was 25.

[0076] Example 5: Preparation of ZnBDC / cellulose acetate hybrid matrix membrane modified by ionic liquid

[0077] 0.01 g of the prepared ionic liquid-modified ZnBDC powder was dispersed in 5 mL of acetone to prepare a filler dispersion. 0.5 g of cellulose acetate polymer was dissolved in 5 mL of acetone to prepare an organic casting solution. The dispersion and casting solution were mixed to form a mixed matrix membrane casting solution, and the mixture was ultrasonicated for 0.5 h and then stirred for approximately 24 h to ensure uniform dispersion. The resulting ionic liquid-modified ZnBDC / polymer mixture was used as the casting solution and drop-coated onto an ultra-flat glass surface. The surface was heated at 60 °C for 24 h on a heating plate to allow the solvent to evaporate slowly. Subsequently, the membrane was placed in a vacuum oven and vacuum-dried at 150 °C for 36 h. The exfoliated membrane material (55 μm thick) was placed in a gas permeameter, and its gas separation performance was tested at 35 °C and 1 bar. The carbon dioxide gas flux was 7.2 Barrer, the carbon dioxide / methane separation performance was 35, and the carbon dioxide / nitrogen separation performance was 27.

[0078] Comparative Example 2: Preparation and Gas Separation Performance Testing of Cellulose Acetate Organic Matrix Membrane

[0079] 0.5 g of cellulose acetate powder was dissolved in 10 mL of acetone and stirred for approximately 24 hours to ensure uniform dispersion. The dispersion was then drop-coated onto a clean, flat glass surface and heated at 60 °C for 24 hours to allow the solvent to evaporate slowly. The membrane was then placed in a vacuum oven and vacuum-dried at 150 °C for 36 hours. The exfoliated membrane material (57 μm thick) was placed in a gas permeameter, and its gas separation performance was tested at 35 °C and 1 bar. The carbon dioxide flux was 5.4 Barrer, the carbon dioxide / methane separation performance was 28, and the carbon dioxide / nitrogen separation performance was 22.

[0080] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A method for preparing ZnBDC metal-organic framework materials modified with ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, comprising the following steps: 1) Dissolve the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate in a solvent and stir to disperse it evenly to obtain an ionic liquid solution; 2) Disperse the ZnBDC material in a solvent and sonicate it to make it uniformly dispersed to obtain a ZnBDC dispersion. 3) Add the ZnBDC dispersion to the above ionic liquid solution and sonicate to ensure thorough and uniform mixing; 4) The resulting mixture was stirred and reacted to obtain ionic liquid modified ZnBDC.

2. The method according to claim 1, characterized in that: In steps 1) and 2), the solvent is at least one of methanol and ethanol. In step 1), the stirring time is 5-20 minutes; The ratio of the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate to the solvent in the ionic liquid solution is 0.5g:10mL-0.5g:20mL; In step 2), the ratio of ZnBDC material to solvent is 0.5g:5mL - 0.5g:15mL; The ultrasonic treatment time is 0.1-1h.

3. The method according to claim 1 or 2, characterized in that: In step 3), the mass ratio of the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate in the ionic liquid solution to the ZnBDC in the ZnBDC dispersion is 1:1 to 1:

4. The ultrasonic treatment time is 0.1-1 hour; In step 4) of the above method, the reaction temperature is 30-90℃ and the time is 12-36h.

4. The ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate modified ZnBDC metal-organic framework material prepared by the method of any one of claims 1-3.

5. An ionic liquid-modified ZnBDC / polymer hybrid matrix membrane, wherein the ionic liquid-modified ZnBDC / polymer hybrid matrix membrane is made from the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate-modified ZnBDC metal-organic framework material as described in claim 4 and polymer materials; in, The polymer material is a polymer matrix membrane material selected from at least one of the following: polyimide (PI), polyetheretherketone (SPEEK), polyamide (Pebax), and cellulose acetate (CA).

6. The ionic liquid-modified ZnBDC / polymer hybrid matrix membrane according to claim 5, characterized in that: The mass ratio of the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate modified ZnBDC metal-organic framework material to the polymer material is 0.5:100-10:100; The thickness of the ionic liquid modified ZnBDC / polymer hybrid matrix membrane is 40μm-70μm, and it is in the form of a flat sheet membrane.

7. A method for preparing the ionic liquid-modified ZnBDC / polymer hybrid matrix membrane according to claim 5 or 6, comprising the following steps: 1) The ZnBDC metal-organic framework material powder modified by ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate was dispersed in a certain amount of solvent to form an inorganic filler dispersion; 2) Dissolve the polymer material in a solvent to form an organic casting solution; 3) The above inorganic filler dispersion is mixed with the organic casting solution, ultrasonically treated, and then stirred to ensure uniform dispersion; 4) Using the obtained ionic liquid-modified ZnBDC / polymer mixture as the casting solution, it was coated onto the ultra-flat surface, and the solvent was evaporated by heating to form a film; 5) Peel off the obtained mixed matrix membrane material and dry it to obtain the ionic liquid modified ZnBDC / polymer mixed matrix membrane.

8. The method according to claim 7, characterized in that: In steps 1) and 2), the solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetone, water, ethanol, and chloroform. In step 1), the mass concentration of ionic liquid modified ZnBDC in the inorganic filler dispersion is 0.001-0.005 g / mL; In step 2), the polymer material is a polymer matrix membrane material selected from at least one of: polyimide PI, polyether ether ketone SPEEK, polyamide Pebax, and cellulose acetate CA; In the organic casting solution, the mass concentration of the polymer material is 0.05-0.1 g / mL; In step 3), the mass ratio of the ionic liquid-modified ZnBDC in the inorganic filler dispersion to the polymer material in the organic casting solution is 0.5:100-10:100; The ultrasonic treatment time is 0.5-2 hours; The stirring time is 12-24 hours; In step 4), the coating is at least one of scraping or dripping. In step 5), the drying is vacuum drying, and the temperature of the vacuum drying is 150-250℃, and the time is 10-40h.

9. The application of the ionic liquid modified ZnBDC / polymer hybrid matrix membrane according to claim 5 or 6 in CO2 separation, wherein the CO2 separation is CO2 / CH4 and CO2 / N2 membrane separation.

10. A CO2 trapping device comprising the ion liquid modified ZnBDC / polymer hybrid matrix membrane as described in claim 5 or 6.

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