A method for preparing highly stable MOF membranes by in-situ growth assisted by concentrated precursor solution and its application in gas-liquid separation.

Abstract

This invention discloses a method for preparing highly stable MOF membranes through in-situ growth assisted by a concentrated precursor solution and its application in gas-liquid separation. The method involves directly immersing a porous support in a concentrated precursor solution for in-situ crystallization, forming a continuous and dense highly stable MOF membrane layer on the surface of the porous support in one step. It also includes collecting highly stable MOF powder with high yield and high crystallinity from the system. The highly stable MOF membrane and the highly stable MOF powder are from the same material system. This process significantly simplifies the membrane fabrication process and achieves dual optimization of MOF membrane structure and powder quality through precise control of in-situ growth parameters. The prepared highly stable MOF membrane and highly stable MOF powder exhibit excellent separation performance and long-term operational stability in various gas-liquid separation scenarios, demonstrating good potential for industrial applications.

Description

Technical Field

[0001] This invention belongs to the field of separation technology, specifically relating to a method for preparing highly stable MOF membranes by in-situ growth assisted by concentrated precursor solutions and its application in gas-liquid separation. Background Technology

[0002] Separation and purification are core unit operations in chemical production processes, and their efficiency directly affects product quality and process economy, playing a crucial role in achieving efficient resource utilization and green sustainable development. Traditional separation technologies, such as distillation, are energy-intensive and costly, necessitating the development of simple and efficient new separation technologies. Membrane separation, as a novel separation process driven by pressure difference, possesses significant advantages such as high separation efficiency, low energy consumption, and simple operation, as it is not limited by phase transitions or thermodynamic equilibrium, and is considered an important development direction for next-generation separation technologies. Metal-organic frameworks (MOFs) are porous network coordination polymers formed by coordination bonds between metal (cluster) nodes and organic bridging ligands. Due to their excellent porosity, uniform and controllable pore size, rich structural designability and modifiability, they are widely used as building blocks in the preparation of crystalline molecular sieve membranes.

[0003] In particular, highly stable MOF materials constructed based on the classical hard-soft acid-base theory, due to the excellent structural stability conferred by the robust metal-linkage coordination bonds, have shown significant separation application potential under harsh environments such as high temperature, high humidity, and acid-base conditions, and have become an important research direction in the field of MOF membranes. However, these MOF materials usually have high growth energy barriers, facing key technical challenges in the film formation process: under conventional reaction conditions, the heterogeneous nucleation density on the support surface is low, which easily leads to insufficient continuity of the prepared film layer or the generation of grain boundary defects. This often requires improvement through complex support surface modification or multi-step growth processes, which not only increases the complexity and cost of the process, but also affects the reproducibility and large-scale preparation of the membrane. In addition, to avoid bulk nucleation in the reaction system, existing MOF membrane preparation processes mostly use low-concentration precursor solutions, resulting in low MOF crystal yield and insufficient crystallinity in the system. It is difficult to achieve effective recovery of highly stable MOF powder simultaneously during the film formation process, resulting in low raw material utilization and limited overall process efficiency.

[0004] Therefore, how to achieve efficient preparation of highly stable MOF membranes while simplifying processes and controlling costs, and simultaneously improve raw material utilization efficiency, has become a key link in promoting the industrial application of this type of membrane material from the laboratory. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing highly stable MOF membranes through in-situ growth assisted by a concentrated precursor solution and its application in gas-liquid separation. This method employs an in-situ growth strategy assisted by a concentrated precursor solution. Utilizing the growth atmosphere of the concentrated precursor solution, by increasing the supersaturation of the reaction system, the nucleation driving force and reagent molecule collision frequency are simultaneously enhanced, effectively promoting heterogeneous nucleation of MOF crystals on the porous support surface and achieving high crystallinity in the bulk solution. Ultimately, under relatively mild conditions, a continuous, dense, highly stable MOF membrane and highly stable MOF powder with high yield and high crystallinity are simultaneously obtained. Furthermore, by synergistically controlling growth parameters, the membrane structure and powder yield can be optimized simultaneously. This method can simultaneously prepare highly stable MOF membranes and MOF powders in a one-step reaction, providing a new technical path to overcome the aforementioned process bottlenecks. The prepared highly stable MOF membranes and MOF powders exhibit excellent separation performance and long-term operational stability in various gas-liquid separation systems.

[0006] This method not only significantly lowers the barrier to preparing highly stable MOF membranes, but also achieves efficient simultaneous preparation of membrane layers and powders, providing a new strategy for the large-scale production of MOF materials. This research is of great strategic significance for promoting the technological upgrading of MOF materials in the separation field and enhancing my country's independent innovation capabilities in functional materials and chemical environmental protection industries, demonstrating broad prospects for industrial promotion and practical application potential.

[0007] This invention is achieved through the following technical solution: A method for preparing a highly stable MOF membrane by in-situ growth assisted by a concentrated precursor solution includes the following steps: directly immersing a porous support in a concentrated precursor solution to carry out an in-situ crystallization reaction, thereby forming a continuous and dense highly stable MOF membrane layer on the surface of the porous support in one step; the concentrated precursor solution includes a metal source, an organic ligand, and a solvent, wherein the concentration of the metal source and the organic ligand in the concentrated precursor solution is 0.1~5 mol / L.

[0008] It also includes collecting highly stable MOF powder from the system after in-situ crystallization reaction to obtain highly stable MOF powder with high yield and high crystallinity; the highly stable MOF film and the highly stable MOF powder are from the same material system.

[0009] The concentrated precursor solution further includes functional reagents; the functional reagents include coordination modifiers, deprotonating agents, or surfactants; the concentration of the functional reagents in the concentrated precursor solution is 0.01~1 mol / L.

[0010] The porous carrier can be flat, tubular, or hollow fiber. The porous carrier material includes metal oxides, elemental metals, non-metal oxides, carbides, or polymer materials. Further, the metal oxide includes alumina, titanium oxide, or zirconium oxide; the metal includes stainless steel or porous nickel; the non-metal oxide includes silicon oxide or glass; the carbide includes silicon carbide; and the polymer includes polyvinylidene fluoride, polyethersulfone, polyacrylonitrile, or polyamide. The pore size of the porous carrier is 1 nm to 100 μm. Preferably, the porous carrier is a flat porous alumina carrier with a pore size of 70 nm.

[0011] It also includes pre-modifying the surface of the porous support: introducing metal compounds, hydroxyl functional groups, or carboxyl functional groups to modify the thin layer through physical adsorption, chemical grafting, or deposition. Further, the porous support is pre-modified using physical deposition methods (such as spin / dip coating or magnetron sputtering), chemical deposition methods (such as sol-gel or electrochemical deposition), chemical vapor deposition, or atomic layer deposition.

[0012] The metal source includes one or more of the following: elemental metal, metal oxide, metal hydroxide, metal salt, and metal alkoxide; further, the metal source includes one or two of the following: metal salt and metal alkoxide.

[0013] The metallic elements include one or more of zinc, cobalt, nickel, copper, magnesium, iron, aluminum, chromium, zirconium, titanium, and hafnium; further, the metallic source includes one or more of zinc, cobalt, aluminum, zirconium, and titanium.

[0014] The organic ligand includes one of carboxylic acid, imidazole, or pyridine ligands. Further, the organic ligand includes one or more of 2-methylimidazole, terephthalic acid, trimellitic acid, and their derivatives (2-methylimidazole, terephthalic acid, or derivatives of trimellitic acid).

[0015] The molar ratio of the metal source to the organic ligand is 1:10 to 10:1.

[0016] The solvent includes one or more of water, methanol, ethanol, acetone, dichloromethane, tetrahydrofuran, acetonitrile, benzene, toluene, N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMA). Further, the solvent includes one or more of water, methanol, and N,N-dimethylformamide.

[0017] The coordination modifier includes one of monodentate carboxylic acids and mineral acids; the deprotonating agent includes one of carboxylates and inorganic bases; the surfactant includes one of ionic and nonionic surfactants. Further, the monodentate carboxylic acid includes one or more of formic acid, acetic acid, propionic acid, butyric acid, valeric acid, trifluoroacetic acid, and benzoic acid; the mineral acid includes one or two of hydrochloric acid and hydrofluoric acid; the carboxylate includes one or two of sodium formate and sodium acetate; the inorganic base includes one or two of triethylamine and ammonia; and the surfactant includes one or more of hexadecyltrimethylbromobromo (CTAB), fatty acid glycerides, and polyvinylpyrrolidone (PVP).

[0018] The in-situ crystallization reaction is an in-situ solvothermal synthesis method, and the heating method is a forced-air oven heating, single-mode microwave heating, multi-mode microwave heating or ultrasonic-assisted heating.

[0019] The in-situ crystallization temperature is 0~300 ℃, and the crystallization time is 5 min~360 h; further, the crystallization temperature is 25~150 ℃, and the crystallization time is 10 min~72 h.

[0020] Furthermore, the highly stable MOF membrane includes polycrystalline MOF membranes constructed based on the hard acid-hard base coordination principle or the soft acid-soft base coordination principle; polycrystalline MOF membranes constructed based on the hard acid-hard base coordination principle include MIL-140s, MIL-125, MIL-53, UiO-66 or MIP-177; polycrystalline MOF membranes constructed based on the soft acid-soft base coordination principle include ZIF-8 or ZIF-67.

[0021] The high-stability MOF film has a thickness of 20 nm to 20 μm and a grain size of 20 nm to 10 μm.

[0022] This invention also provides an application of the highly stable MOF membrane synthesized by the above method in gas or liquid separation. Further, gas separation includes hydrogen purification, carbon dioxide capture, natural gas purification, low-carbon hydrocarbon separation, or inert gas separation; liquid separation includes solvent dehydration, seawater desalination, dye retention, water treatment, ion separation, organic matter separation, chiral compound resolution, or water pollutant purification. The highly stable MOF membrane exhibits excellent separation performance and long-term operational stability under harsh environments.

[0023] This invention also provides an application of the highly stable MOF powder synthesized by the above method in gas or liquid separation. Further, gas separation includes carbon dioxide capture, CH4 / N2 separation, or low-carbon hydrocarbon separation; liquid separation includes solvent dehydration or water pollutant purification. The highly stable MOF powder exhibits excellent separation performance and long-term operational stability under harsh environments.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects: The core innovation of this invention lies in the construction of a unique reaction system of "concentrated precursor solution growth atmosphere," which achieves the following synergistic effects: First, the high concentration of metal ions and organic ligands in the concentrated environment can directly provide sufficient nucleation sites on the carrier surface and in the solution system, significantly reducing the nucleation energy barrier of high-stability MOFs, thereby effectively solving the problem of difficult heterogeneous nucleation of high-stability MOFs in traditional methods; Second, the concentrated precursor solution system greatly increases the effective collision frequency of reactant molecules, making the crystal growth kinetics easier to control, and thus achieving controllable preparation of high-stability MOF films under mild conditions; Third, while the film layer grows in situ, highly crystalline high-stability MOF powder is simultaneously precipitated in the solution phase, forming a simple and efficient preparation mode of "one batch, two products."

[0025] Overall, this invention offers significant process advantages: highly stable MOF membranes and highly stable MOF powders can be simultaneously prepared through a single in-situ growth process, eliminating the need for complex procedures such as seed layer introduction or secondary growth, thus greatly simplifying the production process and reducing equipment and labor costs. Furthermore, by precisely controlling the in-situ growth parameters, dual optimization of membrane structure and powder quality can be achieved—ensuring the integrity of the highly stable MOF membrane structure and meeting the requirements for efficient separation while simultaneously obtaining highly stable MOF powders with excellent crystallinity. Attached Figure Description

[0026] Figure 1 X-ray diffraction (XRD) pattern of the MIL-140A film prepared in Example 1; Figure 2 The image shows a scanning electron microscope (SEM) image of the MIL-140A membrane prepared in Example 1. Figure 3 XRD pattern of MIL-140A powder prepared in Example 1; Figure 4 SEM image of MIL-140A powder prepared in Example 1; Figure 5 Long-term CO2 / CH4 mixed component gas separation performance of the MIL-140A membrane prepared in Example 1; Figure 6 The dye rejection performance of the MIL-140A membrane prepared in Example 1; Figure 7 The gas adsorption behavior of the MIL-140A powder prepared in Example 1; Figure 8 XRD pattern of the ZIF-8 film prepared in Example 2; Figure 9SEM image of the ZIF-8 membrane prepared in Example 2; Figure 10 XRD pattern of ZIF-8 powder prepared in Example 2; Figure 11 SEM image of ZIF-8 powder prepared in Example 2; Figure 12 The long-cycle C3H6 / C3H8 mixed component gas separation performance of the ZIF-8 membrane prepared in Example 2; Figure 13 XRD pattern of the ZnO-modified ZIF-8 film prepared in Example 3; Figure 14 SEM image of the ZnO-modified ZIF-8 film prepared in Example 3; Figure 15 XRD pattern of the UiO-66 film prepared in Example 4; Figure 16 SEM image of the UiO-66 membrane prepared in Example 4; Figure 17 XRD pattern of UiO-66 powder prepared in Example 4; Figure 18 SEM image of UiO-66 powder prepared in Example 4; Figure 19 XRD pattern of the MIL-125-NH2 membrane prepared in Example 5; Figure 20 SEM image of the MIL-125-NH2 membrane prepared in Example 5; Figure 21 XRD pattern of MIL-125-NH2 powder prepared in Example 5; Figure 22 SEM image of MIL-125-NH2 powder prepared in Example 5; Figure 23 XRD patterns of MIL-140A membranes regulated by different types of monodentate carboxylic acids prepared in Example 6; Figure 24 SEM images of MIL-140A membranes regulated by different types of monodentate carboxylic acids prepared in Example 6; Figure 25 Gas separation performance of MIL-140A membranes regulated by different types of monodentate carboxylic acids prepared in Example 6; Figure 26 Gas adsorption behavior of MIL-140A powder regulated by different types of monodentate carboxylic acids prepared in Example 6; Figure 27 XRD pattern of the film prepared in Comparative Example 1; Figure 28 XRD pattern of the powder prepared in Comparative Example 1. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0028] The porous support used in the examples was a commercially available flat-plate porous α-Al₂O₃ support. The porous support had a diameter of 18 mm, a thickness of 1 mm, and a surface pore size of 70 nm.

[0029] Example 1: Simultaneous preparation of MIL-140A membrane and MIL-140A powder by in-situ growth assisted by concentrated precursor solution A concentrated precursor solution was prepared by mixing zirconium tetrachloride as the metal source, terephthalic acid as the organic ligand, and DMF as the solvent. The concentrations of the metal source and the organic ligand were 0.6 mol / L, with a molar ratio of 1:1. A porous alumina support was immersed in the prepared concentrated precursor solution, and a MIL-140A membrane was prepared by in-situ solvothermal method (blown oven, 175 °C, 24 h). XRD and SEM results showed that a continuous MIL-140A membrane was successfully prepared. Figure 1 and 2 ), and highly crystalline MIL-140A powder was collected ( Figure 3 and 4 ).

[0030] The gas separation performance of the prepared MIL-140A membrane in a long-term CO2 / CH4 mixture (molar ratio: 1:1) at room temperature and pressure was systematically evaluated. Over a certain period, the CO2 permeability (~691.1 Barrer) and CO2 / CH4 gas selectivity (~26.5) of the MIL-140A membrane remained stable, demonstrating excellent gas performance stability. Figure 5 Furthermore, the dye retention performance of the prepared MIL-140A membrane at room temperature (dye concentration of 200 mg / L) was systematically evaluated using a cross-flow dye retention device. The prepared MIL-140A membrane exhibited excellent retention performance for Congo red, methylene blue, and methylene blue dyes at room temperature. Figure 6 ).

[0031] The adsorption curves of CO2 and other gases from the collected MIL-140A powder were systematically evaluated, demonstrating excellent CO2 adsorption capacity and CO2 / CH4 and CO2 / N2 adsorption selectivity. Figure 7 ).

[0032] Example 2: Preparation of ZIF-8 membranes and ZIF-8 powders by in-situ growth assisted by concentrated precursor solution Zinc nitrate hexahydrate was used as the metal source, 2-methylimidazole as the organic ligand, and methanol as the solvent to obtain a concentrated precursor solution. The concentrations of the metal source and the organic ligand were 0.2 mol / L, and the molar ratio was 1:1. A porous alumina support was immersed in the prepared concentrated precursor solution, and a ZIF-8 membrane was prepared by in-situ solvothermal method (forced-air drying oven, 100 °C, 9 h). XRD and SEM showed that a continuous ZIF-8 membrane was successfully prepared. Figure 8 and 9 ), and highly crystalline ZIF-8 powder was collected ( Figure 10 and 11 ).

[0033] The gas separation performance of the prepared ZIF-8 membrane under long-term conditions of C3H6 / C3H8 mixed components (molar ratio: 1:1) at room temperature and pressure was systematically evaluated. Within 50 h, the C3H6 permeability of the ZIF-8 membrane was ~51.3 × 10⁻⁶. -10 mol m -2 s -1 Pa -1 The selectivity of both C3H6 and C3H8 mixtures (~24.7) remained stable, demonstrating excellent performance stability. Figure 12 ).

[0034] Example 3: Simultaneous preparation of ZnO-modified ZIF-8 membranes by in-situ growth assisted by concentrated precursor solution Using zinc nitrate hexahydrate as the metal source, 2-methylimidazole as the organic ligand, and methanol as the solvent, a concentrated precursor solution was obtained by mixing. The concentrations of the metal source and the organic ligand were 0.2 mol / L, and the molar ratio was 1:1. ZnO was then modified (for detailed synthesis procedures, please refer to the reference: [reference needed]). J. Mater. Chem. A A porous alumina support (2013, 1, 10635.) was immersed in a prepared concentrated precursor solution, and ZIF-8 membranes were prepared by in-situ solvothermal method (blown oven, 100 °C, 9 h). XRD and SEM showed that a continuous ZIF-8 membrane was successfully prepared. Figure 13 and 14 The gas separation performance test conditions were the same as in Example 2, indicating that the prepared ZIF-8 membrane exhibited excellent C3H6 / C3H8 mixed gas selectivity (~35.2).

[0035] Example 4: Preparation of UiO-66 film and UiO-66 powder by in-situ growth assisted by concentrated precursor solution Using zirconium tetrachloride as the metal source, terephthalic acid as the organic ligand, and water and DMF as a mixed solvent, a concentrated precursor solution was obtained. The concentrations of the metal source and organic ligand were 0.2 mol / L, with a molar ratio of 1:1. The molar ratio of water to DMF in the mixed solvent was 1:10. A porous alumina support was immersed in the prepared concentrated precursor solution, and a UiO-66 membrane was prepared by in-situ solvothermal method (multimode microwave, 110 ℃, 0.5 h). XRD and SEM results showed that a continuous UiO-66 membrane supported by a porous alumina support was successfully prepared. Figure 15 and 16 ), and highly crystalline UiO-66 powder was collected ( Figure 17 and 18 ).

[0036] Example 5: Preparation of MIL-125-NH2 membranes and MIL-125-NH2 powder by in-situ growth assisted by concentrated precursor solution. Using tetraisopropyl titanate as the metal source, aminoterephthalic acid as the organic ligand, and methanol and DMF as a mixed solvent, a concentrated precursor solution was obtained. The concentrations of the metal source and organic ligand were 0.3 mol / L, with a molar ratio of 1:1, and the molar ratio of methanol to DMF in the mixed solvent was 1:10. A porous alumina support was immersed in the prepared concentrated precursor solution, and a MIL-125-NH2 membrane was prepared by in-situ solvothermal method (single-mode microwave, 160 ℃, 1 h). XRD and SEM showed that a continuous MIL-125-NH2 membrane supported by a porous alumina support was successfully prepared. Figure 19 and 20 ), and highly crystalline MIL-125-NH2 powder was collected ( Figure 21 and 22 ).

[0037] Example 6: Modulation of the textural properties of MIL-140A membrane and MIL-140A powder Zirconium tetrachloride was used as the metal source, terephthalic acid as the organic ligand, and various monodentate carboxylic acids as coordination modifiers. DMF was used as the solvent to obtain a concentrated precursor solution. The concentrations of the metal source and organic ligand were 0.6 mol / L, with a molar ratio of 1:1. The monodentate carboxylic acid modifiers included formic acid, acetic acid, propionic acid, octanoic acid, trifluoroacetic acid, and benzoic acid, with a molar ratio of 5:1 to the metal source. A series of MIL-140A membranes were prepared by immersing a porous alumina support in the prepared concentrated precursor solution and using an in-situ solvothermal method (blown oven, 175 °C, 24 h). XRD and SEM results showed that different types of monodentate carboxylic acids significantly affected the structure and crystallinity of the MIL-140A membranes supported on the porous alumina support. Figure 23 and 24 ).

[0038] The gas separation performance of a series of prepared MIL-140A membranes under long-term H2 / CH4 and CO2 / CH4 mixed components (molar ratio: 1:1) at room temperature and pressure was systematically evaluated. Experimental results showed that different monodentate carboxylic acids significantly affected the membrane separation performance, with the MIL-140A membrane prepared by acetic acid exhibiting the best H2 / CH4 and CO2 / CH4 selectivity. Figure 25 Furthermore, different types of monodentate carboxylic acids can simultaneously regulate the gas adsorption capacity of MIL-140A powder. Figure 26 ).

[0039] Comparative Example 1: Preparation of MIL-140A film and MIL-140A powder by in-situ growth assisted by diluted precursor solution A concentrated precursor solution was prepared by mixing zirconium tetrachloride as the metal source, terephthalic acid as the organic ligand, and DMF as the solvent. The concentrations of the metal source and the organic ligand were 0.02 mol / L, with a molar ratio of 1:1. A porous alumina support was immersed in the prepared concentrated precursor solution, and a MIL-140A membrane was prepared by in-situ solvothermal method (blown oven, 175 ℃, 24 h). XRD showed that a continuous membrane layer could not be formed on the surface of the porous support. Figure 27 ), and can only collect amorphous powder ( Figure 28 ).

Claims

1. A method for preparing highly stable MOF membranes by in-situ growth assisted by concentrated precursor solution, characterized in that: The porous support is directly immersed in a concentrated precursor solution to carry out an in-situ crystallization reaction, thereby forming a continuous, dense, and highly stable MOF film on the surface of the porous support in one step. The concentrated precursor solution includes a metal source, an organic ligand, and a solvent, and the concentration of the metal source and the organic ligand in the concentrated precursor solution is 0.1~5 mol / L.

2. The method for preparing highly stable MOF membranes by in-situ growth assisted by concentrated precursor solution as described in claim 1, characterized in that: It also includes collecting highly stable MOF powder from the system after the in-situ crystallization reaction, wherein the highly stable MOF film and the highly stable MOF powder are from the same material system.

3. The method for preparing highly stable MOF membranes by in-situ growth assisted by concentrated precursor solution as described in claim 1, characterized in that: The concentrated precursor solution further includes functional reagents; the functional reagents include coordination modifiers, deprotonating agents, or surfactants; the concentration of the functional reagents in the concentrated precursor solution is 0.01~1 mol / L.

4. The method for preparing highly stable MOF membranes by in-situ growth assisted by concentrated precursor solution as described in claim 1, characterized in that: The porous carrier includes flat plate type, tubular type or hollow fiber type; the porous carrier material includes metal oxide, metal element, non-metal oxide, carbide or polymer material; the pore size of the porous carrier is 1 nm to 100 μm.

5. The method for preparing highly stable MOF membranes by in-situ growth assisted by concentrated precursor solution as described in claim 1, characterized in that: It also includes pre-modification treatment of the porous carrier surface: introducing metal compounds, hydroxyl functional groups or carboxyl functional groups to modify the thin layer through physical adsorption, chemical grafting or deposition.

6. The method for preparing highly stable MOF membranes by in-situ growth assisted by concentrated precursor solution as described in claim 1, characterized in that: The metal source includes one or more of the following: elemental metals, metal oxides, metal hydroxides, metal salts, and metal alkoxides; the metal element includes one or more of the following: zinc, cobalt, nickel, copper, magnesium, iron, aluminum, chromium, zirconium, titanium, and hafnium. The molar ratio of the metal source to the organic ligand is 1:10 to 10:

1.

7. The method for preparing highly stable MOF membranes by in-situ growth assisted by concentrated precursor solution as described in claim 1, characterized in that: The organic ligand includes one of a carboxylic acid, an imidazole, or a pyridine ligand; The solvent includes one or more of water, methanol, ethanol, acetone, dichloromethane, tetrahydrofuran, acetonitrile, benzene, toluene, N,N-dimethylformamide, and N,N-dimethylacetamide.

8. The method for preparing highly stable MOF membranes by in-situ growth assisted by concentrated precursor solution as described in claim 1, characterized in that: The in-situ crystallization temperature is 0~300 ℃, and the crystallization time is 5 min~360 h; The MOF membrane material is a polycrystalline MOF membrane material constructed based on the hard acid-hard base coordination principle or the soft acid-soft base coordination principle.

9. The application of a highly stable MOF membrane synthesized by the method of claim 1 in gas or liquid separation.

10. The application of a highly stable MOF powder synthesized by the method of claim 2 in gas or liquid separation.

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