Single particle layer metal organic framework mixed matrix nanoporous membranes and methods of making the same

Abstract

The application discloses a single-particle layer metal organic framework mixed matrix nanometer porous membrane and a preparation method thereof, and belongs to the field of functional materials and membrane separation technology. The preparation method comprises the following steps: firstly, synthesizing MOF nanoparticles; then, self-assembling the MOF particles and polystyrene balls on the water surface; after treatment, obtaining a MOF single-particle layer; finally, adding a proper amount of a polymer binder to fill the gaps between the MOF particles, so that a single-particle layer MOF mixed matrix nanometer porous membrane is obtained. The single-particle layer MOF mixed matrix nanometer porous membrane prepared by the preparation method is composed of a single-particle layer, has an ultrathin thickness and high strength, and the transmembrane transport of substances in the membrane only needs to pass through a single MOF particle, so that the nanometer porous structure of the MOF particle can be used to the maximum extent, the negative influence of polymer blockage and grain boundary between particles on the substance transport of the nanometer porous membrane is avoided, and the single-particle layer MOF mixed matrix nanometer porous membrane has high selectivity and high permeability.

Description

Technical Field

[0001] This invention belongs to the field of functional materials and membrane separation technology, and relates to a nanoporous self-supporting membrane, particularly to a nanoporous membrane based on MOF nanoparticles and a binder and its preparation method. Background Technology

[0002] Membrane separation technology boasts advantages such as high stability, low energy consumption, small footprint, and ease of preparation, leading to its wide application in energy storage and conversion, and chemical synthesis. However, traditional organic separation membranes, constrained by the trade-off effect, cannot simultaneously achieve high permeation flux and selectivity, thus hindering the sieving of charged ions and small molecules and limiting their application range. To overcome the limitations of the trade-off effect, research on ultrathin nanoporous membranes with narrow pore size distributions (such as anodic alumina (AAO) membranes, graphene membranes, track-etched polymer membranes, and silica nanoporous membranes) has attracted current scientific attention. These nanoporous membranes can utilize precise pore structure design to employ the pore size sieving effect, preventing the passage of ions or molecules larger than the pore size while allowing those smaller to pass through. Among numerous nanoporous materials, metal-organic frameworks (MOFs) offer advantages such as tunable structure, uniform pore size distribution, and functionalizability. They can be composited with polymer binders to form hybrid matrix nanoporous membranes, making them one of the ideal materials for constructing nanoporous membranes.

[0003] However, due to the generally poor interfacial compatibility between MOF particles and polymers, MOF particles tend to aggregate in composite membranes, leading to a decline in the membrane's mechanical and mass transfer properties. Currently, polymer binders in MOF-based nanoporous membranes can clog the pores of MOF particles, hindering mass transport. Furthermore, the presence of numerous grain boundaries between MOF particles in the membrane blocks mass transfer channels within the system, causing substances to transport between MOF particles rather than within them, negatively impacting the selectivity and permeability of the membrane material. Therefore, finding solutions to these problems is crucial for the industrial preparation and practical application of MOF-based nanoporous membranes.

[0004] Optimizing the interface between MOF particles and polymers is a suitable solution to the above problems. Li Tao et al. modified the surface of MOF particles with an octahedral metal-organic nanocage (MONC) called PgC5Cu. By utilizing the open metal sites on the surface of PgC5Cu particles to coordinate and crosslink with polymers, they solved the problem of poor dispersion of MOF particles in mixed matrix films, thereby improving the mass transfer capacity and selectivity of the film (Li Tao, et al., Coating the Right Polymer: Achieving Ideal Metal–Organic Framework Particle Dispersibility in Polymer Matrixes Using a Coordinative Crosslinking Surface Modification Method, Angewandte Chemie., 2021, 60, 14138–14145). Gao et al. improved the dispersibility of MOFs in polymers by attaching amino groups to the surface of MOF particles, thereby enhancing the bonding force between MOFs and polymers. This resulted in the successful preparation of continuous, dense, uniformly dispersed, stable, and high-strength composite membranes (Gao, Kong, Chen, et al. Methods to improve the dispersibility of MOFs in polymer solutions and methods for preparing MOF / polymer composite membranes, CN108586760A[P]. 2018.). Currently, research on optimizing the interface between MOF particles and polymers mainly focuses on surface modification of MOF particles. However, this method struggles to precisely control the distribution of MOF particles at the nanoscale and cannot completely eliminate the problems of polymer clogging of MOF particle pores and MOF particle agglomeration.

[0005] Therefore, developing a hybrid matrix membrane preparation method that can more precisely control the spatial distribution of MOF particles in a polymer matrix is ​​an important research goal. Summary of the Invention

[0006] The purpose of this invention is to overcome the deficiencies in the prior art and provide a single-layer metal-organic framework (MOF) hybrid matrix nanoporous membrane and its preparation method. This invention first synthesizes water-stable MOF particles, then allows the MOF particles to self-assemble with sacrificial template polystyrene (PS) spheres on a liquid surface to form a single-layer structure. The polystyrene spheres are then removed, and a binder is added to synthesize the single-layer MOF hybrid matrix nanoporous membrane. On the one hand, transmembrane transport of substances in the single-layer MOF hybrid matrix nanoporous membrane only requires a single MOF particle, eliminating the negative effects of polymer blockage and intergranular boundaries on material transport in the nanoporous membrane. On the other hand, its thickness is approximately 0.5 μm to 1 μm, lower than that of traditional MOF hybrid matrix nanoporous membranes, reducing the resistance to transmembrane transport. The combination of these two aspects results in a single-layer MOF hybrid matrix nanoporous membrane exhibiting high selectivity and high permeability.

[0007] The specific technical solution adopted in this invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing a single-particle layer metal-organic framework hybrid matrix nanoporous membrane, as detailed below:

[0009] A metal-organic framework (MOF) particle aqueous dispersion is mixed with an aqueous dispersion containing sacrificial template polystyrene spheres, and then ethanol is added to form a mixed solution. The mixed solution is slowly added dropwise to the surface of water to self-assemble and form a MOF / polystyrene monolayer. The MOF / polystyrene monolayer is lifted off the glass substrate, dried, and the polystyrene spheres are removed. An adhesive is added dropwise to the glass substrate carrying the MOF / polystyrene monolayer, and then vacuum heat-treated at 60–90°C for 2–4 hours. The substrate is then immersed in water at 80–90°C for 24–48 hours to separate the resulting monolayer MOF hybrid matrix nanoporous membrane from the glass substrate, thus obtaining a self-supporting monolayer MOF hybrid matrix nanoporous membrane.

[0010] Preferably, the preparation method of the aqueous dispersion of the metal-organic framework particles is as follows:

[0011] Metal salt A and organic ligand A are added to solvent A and mixed evenly to obtain a synthetic solution. The synthetic solution is subjected to a solvothermal reaction. After the reaction is completed, it is allowed to cool naturally and then washed and evenly dispersed in water to obtain an aqueous dispersion of metal-organic framework particles.

[0012] Furthermore, the metal element in the metal salt A is one of Zn, Co, Zr, and Cu; the metal salt A is usually a nitrate, chloride, carbonate, sulfate, or acetate of a metal, preferably one of zinc nitrate, cobalt nitrate, copper nitrate, and zirconium chloride;

[0013] The organic ligand A is one of 2-methylimidazolium, terephthalic acid, trimesic acid, 2-aminoterephthalic acid, and 2-hydroxyterephthalic acid.

[0014] The molar ratio of the metal salt A to the organic ligand A is 1:(0.5-2), preferably 1:1.

[0015] Furthermore, solvent A is one of solvent D, a mixture of formic acid and solvent D, or deionized water, wherein solvent D is at least one of N,N-dimethylacetamide, N,N-diethylformamide, and N,N-dimethylformamide; in order to control the morphology of MOF nanoparticles, the volume of solvent A added is 10-20 mL, and 4-100 L of solvent A is used for every 1 mol of metal salt A; preferably, 5-7 L of solvent A is used for every 1 mol of metal salt A.

[0016] Furthermore, the solution used in the washing process is at least one of methanol, N,N-dimethylacetamide, N,N-diethylformamide, and N,N-dimethylformamide; the mass fraction of the metal-organic framework particles in the resulting aqueous dispersion is 5 wt% to 20 wt%, preferably 10 wt%.

[0017] Furthermore, the solvothermal reaction is carried out in a 50-100 mL sealed container at 40-130 °C for 6-72 hours.

[0018] Preferably, in the aqueous dispersion containing sacrificial template polystyrene spheres, the diameter of the polystyrene spheres is 0.5 μm to 2.0 μm and the mass fraction is 10 wt%; in the mixed solution, the mass ratio of metal-organic framework particles to polystyrene spheres is 1:(2 to 20), and the volume ratio of water to ethanol is 1:(0.75 to 1.25).

[0019] As a preferred method, the polystyrene spheres are removed as follows:

[0020] The dried glass substrate is immersed in solvent B 1 to 3 times, each time for 10 to 30 minutes; the solvent B is one of toluene, dichloromethane, N,N-dimethylacetamide, N,N-diethylformamide, and N,N-dimethylformamide.

[0021] Preferably, the adhesive is a polymer compound with organic solution C as a solvent, and the mass fraction of the polymer compound in the adhesive is 0.15wt% to 0.60wt%. The polymer compound can be selected from one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polymethyl methacrylate (PMMA), polybenzimidazoles (PBI), cellulose acetate (CA), etc., and the organic solution C is one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-diethylformamide, and N,N-dimethylformamide.

[0022] Secondly, the present invention provides a single-layer metal-organic framework hybrid matrix nanoporous membrane obtained by any of the preparation methods described in the first aspect. This single-layer metal-organic framework hybrid matrix nanoporous membrane can be applied to the separation and purification of gases.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) This invention designs a MOF hybrid matrix nanoporous membrane constructed from a single layer of MOF particles by adjusting the spatial arrangement of MOF particles. In the single-layer MOF hybrid matrix nanoporous membrane, the MOF particles are distributed in a single layer, and the gaps between the particles are filled by a polymer binder. The particle surface is not completely covered by the binder, and ordered sub-nanopores still exist for material transport. On the one hand, the transmembrane transport of materials in the single-particle layer MOF hybrid matrix nanoporous membrane only requires a single MOF particle to complete, eliminating the negative effects of polymer blockage and intergranular boundaries on material transport in the nanoporous membrane. On the other hand, its thickness is about 0.5 μm to 1 μm, which is lower than that of traditional material MOF hybrid matrix nanoporous membranes, thus reducing the resistance to transmembrane transport. The combination of these two aspects makes the single-particle layer MOF hybrid matrix nanoporous membrane highly selective and highly permeable.

[0025] (2) The preparation method provided by the present invention provides a design concept for a high-strength ultrathin self-supporting membrane. The ultrathin self-supporting membrane is prepared by MOF particles, sacrificial template and binder solution. The preparation process is simple and inexpensive, and can be used for large-scale production. Attached Figure Description

[0026] Figure 1(a) is a SEM image of the monolayer UiO-66 / polystyrene single particle layer prepared in Example 1 of the present invention; Figure 1 (b)(c)(d) are SEM images of a single-particle layer UiO-66 / polybenzimidazole mixed matrix nanoporous membrane. In the images, (b) is the surface of the membrane on the glass substrate side, (c) is the surface of the membrane on the air side, and (d) is a cross-section.

[0027] Figure 2 The image shows the XRD pattern of the single-particle layer UiO-66 / polybenzimidazole mixed matrix nanoporous membrane prepared in Example 1.

[0028] Figure 3 The image shows the EIS test results of the UiO-66 / polybenzimidazole mixed matrix nanoporous membrane prepared in Example 1 of this invention in an H-cell containing 1 MKCl solution. Detailed Implementation

[0029] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly, provided that there is no mutual conflict.

[0030] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0031] Example 1

[0032] This embodiment provides a monolayer UiO-66 / polybenzimidazole hybrid matrix nanoporous membrane constructed from UiO-66 nanoparticles and the binder polybenzimidazole, and its preparation method. The preparation method includes the following steps:

[0033] (1) Preparation of UiO-66 nanoparticles: UiO-66 was prepared by solvothermal synthesis. Zirconium chloride (34.9 mg) and terephthalic acid (24.9 mg) were dissolved in N,N-dimethylformamide (10 mL) and acetic acid (1.136 mL) by stirring and sonication. The solution was transferred to a 50 mL sealed glass bottle and heat-treated at 125 °C for 12 h. After natural cooling, the powder was separated by centrifugation at 9000 rpm for 6 min. Finally, the obtained powder was washed several times with N,N-dimethylformamide and methanol, and finally dispersed in deionized water to prepare an aqueous dispersion of UiO-66 with a mass fraction of 10 wt%.

[0034] (2) Self-assembly of UiO-66 and polystyrene on liquid surface: Take 100 μL of the 10 wt% UiO-66 aqueous dispersion obtained in step (1) and mix it with 100 μL of the 10 wt% polystyrene aqueous dispersion at a volume ratio of 1:1. Then add 200 μL of ethanol and ultrasonically disperse. Then slowly drop the above-obtained water / ethanol mixture onto the water surface of a glass dish containing a certain amount of deionized water. Self-assemble to form a UiO-66 / polystyrene monolayer. Then use a glass slide to pick up the monolayer, dry it, and then immerse the glass slide in dichloromethane to remove the polystyrene balls. Immersion lasts for 30 minutes each time, and is repeated 3 times.

[0035] (3) Synthesis of a single-layer UiO-66 / polybenzimidazole mixed matrix nanoporous membrane: Take the glass slide with a single UiO-66 layer obtained in step (2), add a 0.3 wt% NMP solution of polybenzimidazole, and then place the glass slide in a vacuum oven for heat treatment at 80°C for 3 hours. Finally, immerse the glass slide in deionized water at 90°C for 24 hours to separate the UiO-66 / polybenzimidazole mixed matrix nanoporous membrane from the glass substrate, thus obtaining a self-supporting UiO-66 / polybenzimidazole mixed matrix nanoporous membrane.

[0036] Example 2

[0037] This embodiment provides a monolayer UiO-66-NH2 / polybenzimidazole hybrid matrix nanoporous membrane constructed from UiO-66-NH2 nanoparticles and polybenzimidazole binder, and its preparation method. The preparation method includes the following steps:

[0038] (1) Preparation of UiO-66 nanoparticles: UiO-66-NH2 was prepared by solvothermal synthesis. Zirconium chloride (34.9 mg) and 2-aminoterephthalic acid (27.2 mg) were dissolved in N,N-dimethylformamide (10 mL) and acetic acid (1.136 mL) by stirring and sonication. The solution was transferred to a 50 mL sealed glass bottle and heat-treated at 125 °C for 12 h. After natural cooling, the powder was separated by centrifugation at 9000 rpm for 6 min. Finally, the obtained powder was washed several times with N,N-dimethylformamide and methanol, and finally dispersed in deionized water to prepare an aqueous dispersion of UiO-66-NH2 with a mass fraction of 10 wt%.

[0039] (2) Self-assembly of UiO-66-NH2 and polystyrene on the liquid surface: Take 100 μL of the aqueous dispersion of UiO-66-NH2 with a mass fraction of 10 wt% obtained in step (1) and mix it with 100 μL of the aqueous dispersion of polystyrene with a mass fraction of 10 wt% in a volume ratio of 1:1. Then add 200 μL of ethanol and ultrasonically disperse. Then slowly drop the above-obtained water / ethanol mixture onto the water surface of a glass dish containing a certain amount of deionized water. Self-assemble to form a UiO-66 / polystyrene monolayer. Then use a glass slide to pick up the monolayer, dry it, and then immerse the glass slide in dichloromethane to remove the polystyrene balls. Immersion lasts for 30 minutes each time, and is repeated 3 times.

[0040] (3) Synthesis of a single-layer UiO-66-NH2 / polybenzimidazole mixed matrix nanoporous membrane: Take the glass slide with a single UiO-66-NH2 layer obtained in step (2), add a 0.3 wt% NMP solution of polybenzimidazole, and then place the glass slide in a vacuum oven for heat treatment at 80°C for 3 h. Finally, immerse the glass slide in deionized water at 90°C for 24 h to separate the UiO-66-NH2 / polybenzimidazole mixed matrix nanoporous membrane from the glass substrate, thus obtaining a self-supporting UiO-66-NH2 / polybenzimidazole mixed matrix nanoporous membrane.

[0041] Example 3

[0042] This embodiment provides a monolayer MOF-808 / polybenzimidazole hybrid matrix nanoporous membrane constructed from MOF-808 nanoparticles and the binder polybenzimidazole, and its preparation method. The preparation method includes the following steps:

[0043] (1) Preparation of MOF-808 nanoparticles: MOF-808 was prepared by solvothermal synthesis. Zirconium oxychloride octahydrate (194.0 mg) and trimesic acid (42.0 mg) were dissolved in N,N-dimethylformamide (10 mL) and formic acid (10 mL) by stirring and ultrasonication. The solution was transferred to a 50 mL sealed glass bottle and heat-treated at 130 °C for 24 hours. After natural cooling, the powder was separated by centrifugation at 9000 rpm for 6 min. Finally, the obtained powder was washed several times with N,N-dimethylformamide and methanol, and then dispersed in deionized water to prepare an aqueous dispersion of MOF-808 with a mass fraction of 10 wt%.

[0044] (2) Self-assembly of MOF-808 and polystyrene on liquid surface: Take 100 μL of the 10 wt% MOF-808 aqueous dispersion obtained in step (1) and mix it with 100 μL of the 10 wt% polystyrene aqueous dispersion at a volume ratio of 1:1. Then add 200 μL of ethanol and ultrasonically disperse. Then slowly drop the above-obtained water / ethanol mixture onto the water surface of a glass dish containing a certain amount of deionized water. Self-assemble to form a MOF-808 / polystyrene monolayer. Then use a glass slide to pick up the monolayer, dry it, and then immerse the glass slide in dichloromethane to remove the polystyrene balls. Immersion lasts for 30 minutes each time, and is repeated 3 times.

[0045] (3) Synthesis of MOF-808 / polybenzimidazole mixed matrix nanoporous membrane with single particle layer: Take the glass slide with MOF-808 single particle layer obtained in step (2), add NMP solution of polybenzimidazole with a mass fraction of 0.25 wt%, and then place the glass slide in a vacuum oven for heat treatment at 80°C for 3 h. Finally, immerse the glass slide in deionized water at 90°C for 24 h to separate the MOF-808 / polybenzimidazole mixed matrix nanoporous membrane from the glass substrate, and obtain a self-supporting MOF-808 / polybenzimidazole mixed matrix nanoporous membrane.

[0046] Example 4

[0047] This embodiment provides a monolayer UiO-67 / polybenzimidazole hybrid matrix nanoporous membrane constructed from UiO-67 nanoparticles and the binder polybenzimidazole, and its preparation method. The preparation method includes the following steps:

[0048] (1) Preparation of UiO-67 nanoparticles: UiO-67 was prepared by solvothermal synthesis. Zirconium oxychloride octahydrate (194.0 mg) and biphenyl dicarboxylic acid (36.3 mg) were dissolved in N,N-dimethylformamide (10 mL) and formic acid (10 mL) by stirring and ultrasonication. The solution was transferred to a 50 mL sealed glass bottle and heat-treated at 125 °C for 12 hours. After natural cooling, the powder was separated by centrifugation at 9000 rpm for 6 min. Finally, the obtained powder was washed several times with N,N-dimethylformamide and methanol, and then dispersed in deionized water to prepare an aqueous dispersion of UiO-67 with a mass fraction of 10 wt%.

[0049] (2) Self-assembly of UiO-67 and polystyrene on liquid surface: Take 100 μL of the aqueous dispersion of 10 wt% UiO-67 obtained in step (1) and mix it with 100 μL of the aqueous dispersion of 10 wt% polystyrene in a volume ratio of 1:1. Then add 200 μL of ethanol and ultrasonically disperse. Then slowly drop the above-obtained water / ethanol mixture onto the water surface of a glass dish containing a certain amount of deionized water. Self-assemble to form a UiO-67 / polystyrene monolayer. Then use a glass slide to pick up the monolayer, dry it, and then immerse the glass slide in dichloromethane to remove the polystyrene balls. Immersion lasts for 30 minutes each time, and is repeated 3 times.

[0050] (3) Synthesis of a single-layer UiO-67 / polybenzimidazole mixed matrix nanoporous membrane: Take the glass slide with a single UiO-67 layer obtained in step (2), add a 0.25 wt% NMP solution of polybenzimidazole, and then place the glass slide in a vacuum oven for heat treatment at 80°C for 3 h. Finally, immerse the glass slide in deionized water at 90°C for 24 h to separate the UiO-67 / polybenzimidazole mixed matrix nanoporous membrane from the glass substrate, thus obtaining a self-supporting UiO-67 / polybenzimidazole mixed matrix nanoporous membrane.

[0051] Example 5

[0052] This embodiment provides a monolayer ZIF-8 / polybenzimidazole hybrid matrix nanoporous membrane constructed from ZIF-8 nanoparticles and the binder polybenzimidazole, and its preparation method. The preparation method includes the following steps:

[0053] (1) Preparation of ZIF-8 nanoparticles: UiO-67 was prepared by solvothermal synthesis. Zirconium oxychloride octahydrate (194.0 mg) and biphenyl dicarboxylic acid (36.3 mg) were dissolved in N,N-dimethylformamide (10 mL) and formic acid (10 mL) by stirring and ultrasonication. The solution was transferred to a 50 mL sealed glass bottle and heat-treated at 125 °C for 12 h. After natural cooling, the powder was separated by centrifugation at 9000 rpm for 6 min. Finally, the obtained powder was washed several times with N,N-dimethylformamide and methanol, and then dispersed in deionized water to prepare an aqueous dispersion of UiO-67 with a mass fraction of 10 wt%.

[0054] (2) Self-assembly of ZIF-8 and polystyrene on liquid surface: Take 100 μL of the aqueous dispersion of 10 wt% UiO-67 obtained in step (1) and mix it with 100 μL of the aqueous dispersion of 10 wt% polystyrene in a volume ratio of 1:1. Then add 200 μL of ethanol and ultrasonically disperse. Then slowly drop the above-obtained water / ethanol mixture onto the water surface of a glass dish containing a certain amount of deionized water. Self-assemble to form a UiO-67 / polystyrene monolayer. Then use a glass slide to pick up the monolayer, dry it, and then immerse the glass slide in dichloromethane to remove the polystyrene balls. Immersion lasts for 30 minutes each time, and is repeated 3 times.

[0055] (3) Synthesis of a single-layer ZIF-8 / polybenzimidazole mixed matrix nanoporous membrane: Take the glass slide with a UiO-67 single-layer substrate obtained in step (2), add a 0.25 wt% NMP solution of polybenzimidazole, and then place the glass slide in a vacuum oven for heat treatment at 80°C for 3 h. Finally, immerse the glass slide in deionized water at 90°C for 24 h to separate the UiO-67 / polybenzimidazole mixed matrix nanoporous membrane from the glass substrate, thus obtaining a self-supporting UiO-67 / polybenzimidazole mixed matrix nanoporous membrane.

[0056] Example 6

[0057] This embodiment provides a monolayer UiO-66 / polybenzimidazole hybrid matrix nanoporous membrane constructed from UiO-66 nanoparticles and cellulose acetate binder, and its preparation method. The preparation method includes the following steps:

[0058] (1) Preparation of UiO-66 nanoparticles: UiO-66 was prepared by solvothermal synthesis. Zirconium chloride (34.9 mg) and terephthalic acid (24.9 mg) were dissolved in N,N-dimethylformamide (10 mL) and acetic acid (1.136 mL) by stirring and sonication. The solution was transferred to a 50 mL sealed glass bottle and heat-treated at 125 °C for 12 h. After natural cooling, the powder was separated by centrifugation at 9000 rpm for 6 min. Finally, the obtained powder was washed several times with N,N-dimethylformamide and methanol, and finally dispersed in deionized water to prepare an aqueous dispersion of UiO-66 with a mass fraction of 10 wt%.

[0059] (2) Self-assembly of UiO-66 and polystyrene on liquid surface: Take 100 μL of the 10 wt% UiO-66 aqueous dispersion obtained in step (1) and mix it with 100 μL of the 10 wt% polystyrene aqueous dispersion at a volume ratio of 1:1. Then add 200 μL of ethanol and ultrasonically disperse. Then slowly drop the above-obtained water / ethanol mixture onto the water surface of a glass dish containing a certain amount of deionized water. Self-assemble to form a UiO-66 / polystyrene monolayer. Then use a glass slide to pick up the monolayer, dry it, and then immerse the glass slide in dichloromethane to remove the polystyrene balls. Immersion lasts for 30 minutes each time, and is repeated 3 times.

[0060] (3) Synthesis of a single-layer UiO-66 / polybenzimidazole mixed matrix nanoporous membrane: Take the glass slide with a single UiO-66 layer obtained in step (2), add a 0.3 wt% NMP solution of polybenzimidazole, and then place the glass slide in a vacuum oven for heat treatment at 80°C for 3 hours. Finally, immerse the glass slide in deionized water at 90°C for 24 hours to separate the UiO-66 / polybenzimidazole mixed matrix nanoporous membrane from the glass substrate, thus obtaining a self-supporting UiO-66 / polybenzimidazole mixed matrix nanoporous membrane.

[0061] The ion conductivity test and characterization results of the intermediate products and monolayer nanoparticle mixed matrix films obtained in Examples 1-6 are shown below:

[0062] Figure 1 (a) is a SEM image of the UiO-66 / polystyrene monolayer prepared in step 2 of Example 1. Figure 1 (a) It is demonstrated that the PS sacrificial template is uniformly distributed in the gaps between UiO-66 nanoparticles, and its removal will provide space for the filling of the binder. Figure 1 (b) is a SEM image of the UiO-66 / PBI monolayer hybrid matrix film synthesized in step 3 of Example 1, on the glass side. Figure 1 (c) is a SEM image of the air-facing side of the UiO-66 / PBI monolayer hybrid matrix membrane synthesized in step 3 of Example 1. Figure 1 (b) and (c) together illustrate the single-particle characteristics of the mixed matrix membrane, proving that the UiO-66 nanoparticles penetrate the composite membrane, and that mass transfer within the membrane will mainly occur within the nanoparticles.

[0063] Figure 2 The image shows the XRD pattern of the UiO-66 / PBI monolayer hybrid matrix film prepared in step 3 of Example 1. Compared with the XRD image of UiO-66 powder, the XRD image of the monolayer UiO-66 hybrid matrix film has only a single peak at around 7°, proving that the UiO-66 nanoparticles in the composite film expose a single crystal plane and exhibit an ordered arrangement.

[0064] Figure 3 The image shows the AC impedance spectroscopy of an H-cell assembled from a UiO-66 / PBI monolayer hybrid matrix membrane prepared in step 3 of Example 1, with dimensions of 1cm × 1cm. Figure 3 This demonstrates that the UiO-66 / PBI monolayer hybrid matrix membrane exhibits a low sheet resistivity (6.3 Ωcm) in a 1 M KCl solution. -2 ).

[0065] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A method for preparing a single-particle layer metal-organic framework hybrid matrix nanoporous membrane, characterized in that, Specifically as follows: A metal-organic framework (MOF) particle aqueous dispersion is mixed with an aqueous dispersion containing sacrificial template polystyrene spheres, and then ethanol is added to form a mixed solution. The mixed solution is slowly added dropwise to the surface of water to form a MOF / polystyrene monolayer through self-assembly. The MOF / polystyrene monolayer is lifted off the glass substrate, dried, and the polystyrene spheres are removed. An adhesive is added dropwise to the glass substrate carrying the MOF / polystyrene monolayer, and then the substrate is subjected to vacuum heat treatment at 60–90°C for 2–4 hours. The substrate is then immersed in water at 80–90°C for 24–48 hours to separate the resulting monolayer MOF hybrid matrix nanoporous membrane from the glass substrate, thus obtaining a self-supporting monolayer MOF hybrid matrix nanoporous membrane. The adhesive is a polymer compound with organic solution C as a solvent, and the mass fraction of the polymer compound in the adhesive is 0.15wt% to 0.60wt%. The polymer compound is one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, polybenzimidazole, and cellulose acetate. The organic solution C is one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-diethylformamide, and N,N-dimethylformamide.

2. The method for preparing a single-particle layer metal-organic framework hybrid matrix nanoporous membrane according to claim 1, characterized in that, The preparation method of the aqueous dispersion of the metal-organic framework particles is as follows: Metal salt A and organic ligand A are added to solvent A and mixed evenly to obtain a synthetic solution. The synthetic solution is subjected to a solvothermal reaction. After the reaction is completed, it is allowed to cool naturally and then washed and evenly dispersed in water to obtain an aqueous dispersion of metal-organic framework particles.

3. The method for preparing a single-particle layer metal-organic framework hybrid matrix nanoporous membrane according to claim 2, characterized in that, The metal element in the metal salt A is one of Zn, Co, Zr, and Cu; the metal salt A is a nitrate, chloride, carbonate, sulfate, or acetate of a metal; the organic ligand A is one of 2-methylimidazolium, terephthalic acid, trimesic acid, 2-aminoterephthalic acid, and 2-hydroxyterephthalic acid; the molar ratio of the metal salt A to the organic ligand A is 1:(0.5-2).

4. The method for preparing a single-particle layer metal-organic framework hybrid matrix nanoporous membrane according to claim 3, characterized in that, The metal salt A is one of zinc nitrate, cobalt nitrate, copper nitrate, and zirconium chloride.

5. The method for preparing a single-particle layer metal-organic framework hybrid matrix nanoporous membrane according to claim 3, characterized in that, The molar ratio of the metal salt A to the organic ligand A is 1:

1.

6. The method for preparing a single-particle layer metal-organic framework hybrid matrix nanoporous membrane according to claim 2, characterized in that, The solvent A is one of solvent D, a mixture of formic acid and solvent D, or deionized water, wherein solvent D is at least one of N,N-dimethylacetamide, N,N-diethylformamide, and N,N-dimethylformamide; the volume of solvent A added is 10 to 20 mL, and 4 to 100 L of solvent A is used for every 1 mol of metal salt A.

7. The method for preparing a single-particle layer metal-organic framework hybrid matrix nanoporous membrane according to claim 6, characterized in that, For every 1 mol of metal salt A, use 5 to 7 L of solvent A.

8. The method for preparing a single-particle layer metal-organic framework hybrid matrix nanoporous membrane according to claim 2, characterized in that, The washing solution is at least one of methanol, N,N-dimethylacetamide, N,N-diethylformamide, and N,N-dimethylformamide; the mass fraction of the metal-organic framework particles in the resulting aqueous dispersion is 5 wt% to 20 wt%.

9. The method for preparing a single-particle layer metal-organic framework hybrid matrix nanoporous membrane according to claim 8, characterized in that, The metal-organic framework particles in the aqueous dispersion have a mass fraction of 10 wt%.

10. The method for preparing a single-particle layer metal-organic framework hybrid matrix nanoporous membrane according to claim 2, characterized in that, The solvothermal reaction is carried out in a 50-100 mL sealed container at 40-130°C for 6-72 hours.

11. The method for preparing a single-particle layer metal-organic framework hybrid matrix nanoporous membrane according to claim 1, characterized in that, In the aqueous dispersion containing sacrificial template polystyrene spheres, the polystyrene spheres have a diameter of 0.5 µm to 2.0 µm and a mass fraction of 10 wt%; in the mixed solution, the mass ratio of metal-organic framework particles to polystyrene spheres is 1:(2 to 20), and the volume ratio of water to ethanol is 1:(0.75 to 1.25).

12. The method for preparing a single-particle layer metal-organic framework hybrid matrix nanoporous membrane according to claim 1, characterized in that, The method for removing the polystyrene balls is as follows: The dried glass substrate is immersed in solvent B 1 to 3 times, each time for 10 to 30 minutes; the solvent B is one of toluene, dichloromethane, N,N-dimethylacetamide, N,N-diethylformamide, and N,N-dimethylformamide.

13. A single-layer metal-organic framework hybrid matrix nanoporous membrane obtained by the preparation method according to any one of claims 1 to 12.

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