A method for preparing an ac-modified cu-btc-based mixed matrix membrane

Abstract

The application relates to a preparation method of an AC modified Cu-BTC-based mixed matrix membrane, which comprises the following steps: weighing 0.5-1g of Cu(NO3)2.3H2O and 0.3-0.5g of an AC modifier, dissolving the two in a mixed solution of deionized water and anhydrous ethanol, mixing through ultrasonic waves to obtain a uniformly mixed Cu-BTC-AC solution, pouring the Cu-BTC-AC solution into a flask and performing constant-temperature heating and stirring, recovering the product through centrifugation, removing residual solvent and vacuum drying to obtain Cu-BTC-AC particles, then adding the Cu-BTC-AC particles into a Pebax solution to remove air bubbles and obtain Cu-BTC-AC fillers, finally coating the Cu-BTC-AC fillers on a pre-coated PDMS and PVA modified PSf base, and placing the base in a vacuum environment at 30-35 DEG C to dry and remove residual solvent, so as to obtain a Pebax mixed matrix membrane; the application has the advantages of improving the stability of MOFs in a humid environment.

Description

Technical Field

[0001] This invention belongs to the field of Cu-BTC-AC / Pebax hybrid matrix membrane technology, specifically relating to a method for preparing AC-modified Cu-BTC-based hybrid matrix membranes. Background Technology

[0002] With increasing global awareness of climate change and environmental protection, carbon peaking and carbon neutrality have become common global goals. Against this backdrop, membrane separation, with its advantages of low energy consumption, high efficiency, and zero pollution, is finding increasingly widespread application in energy, environmental protection, and chemical industries. Hybrid matrix membranes are multilayer composite membranes composed of a polymer matrix and a packing material, offering advantages such as high separation performance, high throughput, and low energy consumption. The packing material can be inorganic particles, carbon nanotubes, graphene, or other materials. Compared to traditional polymer membranes, hybrid matrix membranes have the advantage that the packing material can enhance the membrane's separation performance and form a porous structure within the polymer matrix, thereby improving separation efficiency.

[0003] Metal-organic frameworks (MOFs) are novel porous materials with high specific surface area, tunable pore size, and selective adsorption, thus attracting widespread attention in the field of membrane separation. Introducing MOFs into mixed matrix membranes can further improve membrane separation performance. However, most MOFs are susceptible to moisture damage in humid environments, leading to framework structure collapse and reduced separation performance and stability, which limits their application in membrane separation. Therefore, water stability modification of MOFs is necessary to improve their durability and separation performance in humid environments, potentially further enhancing their application value in membrane separation.

[0004] The introduction of MOFs can improve the separation performance of mixed matrix membranes, but they are susceptible to moisture degradation in humid environments. Therefore, water stability modification is an important way to improve the stability and separation performance of mixed matrix membranes. Chinese invention patent CN114602336A discloses an invention entitled "A Mixed Matrix Membrane, a Vapor-Induced In-Situ Synthesis Method, and its Application in H2 / CO2 Separation." It introduces a method for preparing a mixed matrix membrane doped with M(SiF6)(pyz)3 (M = Cu, Zn, Co, Ni) or M(SiF6)(bpy)2 and its application in the field of H2 / CO2 separation. However, the separation membrane prepared in this patent only verifies its application potential in the field of H2 / CO2 separation and does not show high selectivity for CO2 / N2, so it cannot be applied in the field of CO2 / N2 separation. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing AC-modified Cu-BTC-based hybrid matrix membranes that improves the stability of MOFs in humid environments.

[0006] The technical solution of the present invention is as follows: A method for preparing an AC-modified Cu-BTC-based hybrid matrix membrane includes the following steps: S1: Weigh 0.5-1 g of Cu(NO3)2·3H2O and 0.3-0.5 g of AC modifier, dissolve them in a mixed solution of deionized water and anhydrous ethanol, and then mix them by ultrasound to obtain a uniformly mixed Cu-BTC-AC solution. S2: Pour the Cu-BTC-AC solution obtained in S1 into a flask, then place the flask in an oil bath and heat it at 100-130 ℃ for 10-16 hours while stirring. After cooling to room temperature, centrifuge to recover the product and wash with ethanol to remove residual solvent. Then, vacuum dry the Cu-BTC-AC solution in the beaker at 100-130 ℃ for 10-16 hours to obtain Cu-BTC-AC particles. S3: Add Cu-BTC-AC particles to Pebax solution, stir for 24-36 hours, let stand for 24-36 hours to remove bubbles, and obtain Cu-BTC-AC filler; S4: Coat Cu-BTC-AC filler onto a pre-coated PDMS and PVA-modified PSf substrate, and dry it in a vacuum environment at 30-35 ℃ to remove residual solvent, thus preparing a Pebax mixed matrix membrane with Cu-BTC-AC added.

[0007] Furthermore, the volume of deionized water and anhydrous ethanol in the mixed solution is 10-15 mL.

[0008] Furthermore, the preparation steps of the Pebax solution are as follows: A: Weigh 1-1.5 g of Pebax granules and dissolve them in a mixed solution of ethanol:water = 7:3 (v / v) to prepare a solution (1-3 wt%). B: Stir the solution from step A vigorously at 70-80℃ for 2-4 hours to obtain a homogeneous Pebax solution.

[0009] Further, in step S3, (5 wt%-20 wt%) is added to 8-10 mL of Pebax solution.

[0010] Furthermore, the AC modifier is specifically ammonium citrate.

[0011] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention prepares Cu-BTC-AC filler by introducing AC modifier, improves water stability by utilizing the steric hindrance effect of AC modifier, and prepares Cu-BTC-AC based Pebax mixed matrix membrane by Cu-BTC-AC filler. Cu-BTC-AC filler has good dispersion in the membrane and exhibits good interfacial interaction with Pebax. 2. Due to the pore effect and strong affinity of the unsaturated sites of the Cu-BTC-AC filler for CO2 molecules, the Pebax mixed matrix membrane prepared by this invention has excellent CO2 permeability and the CO2 / N2 selectivity is also significantly improved.

[0012] In summary, the present invention has the advantage of improving the stability of MOFs in humid environments. Attached Figure Description

[0013] Figure 1 SEM surface images of Pebax hybrid matrix films with different Cu-BTC-AC particle loadings according to the present invention; Figure 2 SEM cross-sectional images of Pebax hybrid matrix membranes with different Cu-BTC-AC particle loadings according to the present invention; Figure 3 The graph shows the CO2 and N2 gas performance test results of this invention under different Cu-BTC-AC particle loads. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] A method for preparing an AC-modified Cu-BTC-based hybrid matrix membrane includes the following steps: S1: Weigh 0.5-1 g of Cu(NO3)2·3H2O and 0.3-0.5 g of AC modifier and dissolve them in a mixed solution made of 10-15 mL of deionized water and 10-15 mL of anhydrous ethanol. Mix the solutions by sonication for 5-15 min to obtain a uniformly mixed Cu-BTC-AC solution. S2: Pour the Cu-BTC-AC solution obtained in S1 into a 50-200 mL flask, then place the flask in an oil bath and heat it at 100-130 ℃ for 10-16 hours while stirring. After cooling to room temperature, centrifuge to recover the product and wash with ethanol to remove residual solvent. Then, vacuum dry the Cu-BTC-AC solution in the beaker at 100-130 ℃ for 10-16 hours to obtain Cu-BTC-AC particles. S3: Weigh 1-1.5 g of Pebax particles and dissolve them in a mixed solution of ethanol:water = 7:3 (v / v) to prepare a solution (1-3 wt%). Stir vigorously at 70-80℃ for 2-4 hours to obtain a homogeneous Pebax solution. Add 5 wt%-20 wt% of Cu-BTC-AC particles to 8-10 mL of the above Pebax solution, stir for 24-36 hours, and then let stand for 24-36 hours to remove air bubbles to obtain Cu-BTC-AC filler. S4: Using a 50-100 µm doctor blade, Cu-BTC-AC filler was coated onto a pre-coated PDMS and PVA-modified PSf substrate, and then placed in a vacuum oven at 30-35 °C to remove residual solvent, thus preparing a Pebax mixed matrix membrane with Cu-BTC-AC added.

[0016] In this embodiment, the AC modifier is specifically ammonium citrate.

[0017] like Figure 1-2 As shown, Figure 1 The four types a, b, c, and d in the figure represent (a) 5 wt% SEM surface image, (b) 10 wt% SEM surface image, (c) 15 wt% SEM surface image, and (d) 20 wt% SEM surface image, respectively. Figure 2 In the image, a, b, c, and d represent (a) a 5 wt% SEM cross-sectional image, (b) a 10 wt% SEM cross-sectional image, (c) a 15 wt% SEM cross-sectional image, and (d) a 20 wt% SEM cross-sectional image, respectively. Figure 1 Surface and cross-sectional morphology images of MMMs under different Cu-BTC-AC loadings. From Figure 1As can be seen, the number of particles on the surface of the Pebax mixed matrix membrane gradually increases with the increase of Cu-BTC-AC filler. At low filler loading (below 15 wt%), Cu-BTC-AC particles are well distributed in the Pebax mixed matrix membrane without obvious particle aggregation, indicating that Cu-BTC-AC particles have good dispersibility in the Pebax solution. When the Cu-BTC-AC loading increases to 20 wt%, particle aggregation is clearly observed. Furthermore, the cross-section of the Pebax mixed matrix membrane is shown below. Figure 2 As shown, a defect-free, dense layer of approximately 1 μm was formed on the PSf substrate. When the Cu-BTC-AC loading reached 20 wt%, some particle agglomeration was observed. This indicates that the particle loading has a significant impact on the morphology and structure of the Pebax hybrid matrix film.

[0018] like Figure 3 As shown, with the increase of Cu-BTC-AC loading, a large number of gas mass transfer channels are introduced into the Pebax hybrid matrix membrane. Simultaneously, due to the Cu content of Cu-BTC-AC molecules... 2+ The open sites exhibit a strong affinity for CO2 molecules, significantly improving the CO2 permeation flux. Furthermore, the CO2 / N2 selectivity of the Pebax mixed matrix membrane initially increases and then decreases with increasing filler content. At a Cu-BTC-AC loading (20 wt%), the CO2 selectivity shows a significant decline, likely due to Cu-BTC-AC particle agglomeration and the appearance of non-selective defect pores within the membrane. Gas permeation performance tests of the Pebax mixed matrix membrane demonstrate its good CO2 / N2 separation performance, along with excellent water stability, making it suitable for practical flue gas separation applications.

[0019] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an AC-modified Cu-BTC-based hybrid matrix membrane, characterized in that: Includes the following steps S1: Weigh 0.5-1 g of Cu(NO3)2·3H2O and 0.3-0.5 g of citric acid and dissolve them in a mixed solution of deionized water and anhydrous ethanol, and then mix them by ultrasound to obtain a uniformly mixed Cu-BTC-AC solution. S2: Pour the Cu-BTC-AC solution obtained in S1 into a flask, then place the flask in an oil bath and heat it at 100-130℃ for 10-16 hours while stirring. After cooling to room temperature, centrifuge to recover the product and wash with ethanol to remove residual solvent. Then, vacuum dry the Cu-BTC-AC solution in the beaker at 100-130℃ for 10-16 hours to obtain Cu-BTC-AC particles. S3: Add (5 wt%-20 wt%) Cu-BTC-AC particles to 8-10 mL of Pebax solution, stir for 24-36 hours, let stand for 24-36 hours to remove air bubbles, and obtain Cu-BTC-AC filler; S4: Coat Cu-BTC-AC filler onto a pre-coated PDMS and PVA-modified PSf substrate, and dry it in a vacuum environment at 30-35 ℃ to remove residual solvent, thus preparing a Pebax mixed matrix membrane with Cu-BTC-AC added.

2. The method for preparing an AC-modified Cu-BTC-based mixed matrix membrane according to claim 1, characterized in that: The volume of deionized water and anhydrous ethanol in the mixed solution is 10-15 mL.

3. The method for preparing an AC-modified Cu-BTC-based mixed matrix membrane according to claim 1, characterized in that: The preparation steps of the Pebax solution are as follows: A: Weigh 1-1.5 g of Pebax granules and dissolve them in a mixed solution of ethanol:water = 7:3 (v / v) to prepare a (1-3 wt%) Pebax solution; B: Stir the solution from step A vigorously at 70-80℃ for 2-4 hours to obtain a homogeneous Pebax solution.

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