MOF (Metal Organic Framework) membrane for efficiently and selectively separating lithium ions, preparation method of MOF membrane and MOF membrane

Abstract

The invention belongs to the technical field of membrane separation, and particularly relates to a preparation method of an MOF membrane for efficient and selective separation of lithium ions and the MOF membrane. The MOF film comprises a matrix film, a bonding layer and a selection layer, the matrix film is CEM, the bonding layer is PVA, and the selection layer is UIO-66-SO3H; a bonding auxiliary growth strategy is provided, a bionic ion transmission channel MOF selection layer with the double-nanometer confinement effect is constructed on the surface of the matrix membrane, firm interconnection and transmission network communication between the matrix membrane and the MOF selection layer are achieved through the bonding layer, the permeation rate and selectivity of lithium ions are remarkably improved, and the service life of the matrix membrane is prolonged. The prepared MOF film shows excellent oxidation resistance and can effectively resist erosion of oxidizing media in practical application, so that the service life of a film material in a severe environment is greatly prolonged.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of membrane separation technology, and particularly relates to a membrane for high-efficiency selective separation of lithium ions, a preparation method thereof and a MOF membrane. BACKGROUND

[0002] Under the dual driving of global energy transformation and carbon neutralization goals, new energy vehicles have completely replaced traditional fuel vehicles and become the mainstream of the industry. Energy storage systems, as a key infrastructure supporting the large-scale application of new energy and the stability of the power grid, have also entered a high-speed development channel. Lithium-ion batteries, as the core energy storage technology, have shown explosive growth in market demand, with an annual growth rate of more than 30% in key fields such as transportation, electronic equipment, and renewable energy. According to forecasts, lithium batteries will account for 70% of the global battery market by 2025, and the global market size is expected to exceed $139 billion in 2026. This growth trend has brought unprecedented development opportunities for upstream lithium extraction technologies, driving continuous breakthroughs in innovative processes such as low-grade salt lake brine lithium extraction. Through technological innovation to improve lithium extraction efficiency, it has become a key path to address resource constraints, reduce environmental pressure, and create significant economic benefits and investment value.

[0003] Traditional lithium extraction processes, such as evaporation pond methods and lithium spodumene mining, are facing severe environmental and sustainability challenges: evaporation pond methods not only occupy a large amount of land and water resources, but also easily lead to soil salinization and ecological degradation; while hard rock mining causes low resource utilization and high environmental costs due to low ore grade, high energy consumption, and serious tailings pollution. In this context, developing green and low-carbon new extraction technologies has become an industry consensus, among which salt lake lithium extraction has become a key direction due to its large resource reserves and low energy consumption. This technology aims to directly extract lithium from salt lake brine, and the core challenge lies in achieving efficient separation of magnesium and lithium ions; due to their similar hydrated ion radii and chemical properties, traditional methods have difficulty in separating them, and the separation efficiency directly determines the overall lithium extraction efficiency and the purity of the final product.

[0004] In recent years, significant progress has been made in lithium ion separation technology, with various methods such as adsorption and membrane-based separation (e.g., reverse osmosis and nanofiltration) emerging. Among these methods, selective electrodialysis has attracted considerable attention due to its high efficiency and sustainability. This technology relies on ion exchange membranes (IEM) driven by an electric field to achieve precise screening of lithium ions. It can be coupled with other processes and operated with renewable energy, making it environmentally friendly and economically feasible. However, developing ion exchange membranes with high lithium ion selectivity remains a core challenge. Such membranes must accurately identify lithium ions in complex solution environments, and their breakthrough is crucial not only for lithium extraction but also for the development of related fields such as desalination, resource recovery, and electrochemical energy storage. Traditional polymeric cation exchange membranes are limited by their inherent properties, while new membrane materials with adjustable pore structures and surface chemical properties exhibit better ion selectivity, transport efficiency, and stability, promising revolutionary progress in lithium resource extraction and industrial separation technology.

[0005] MOFs are a type of crystalline porous material formed by self-assembly of metal nodes and organic ligands. With their highly ordered and precisely tunable pore structures, MOFs have become an ideal platform for constructing high-performance ion-selective separation membranes. Inspired by the excellent selectivity and transport efficiency of biological ion channels, researchers have successfully constructed biomimetic ion channels with size sieving and chemical recognition functions in MOFs by designing appropriate assembly strategies for metal clusters and functional ligands. These channels can efficiently identify and selectively transport target ions. The transport behavior of ions in these channels is regulated by multiple mechanisms, including size sieving, Donnan exclusion, ion dehydration effects, and intra-pore diffusion. Key factors include pore size, surface chemical properties, charge distribution, hydration state, and ion-pore interactions. Water-stable MOFs, represented by UIO-66, have shown great potential in nanofluidic devices, seawater desalination, and ion separation due to their excellent structural stability and tunability.

[0006] A Chinese invention patent with application number 201911379573.9 discloses a defect-free MOF-801 membrane. It provides a new preparation method for defect-free metal-organic framework thin films, offering high-performance selective membranes for the separation field. Although this preparation method can successfully obtain MOF membranes, it requires complex post-treatment procedures, resulting in a cumbersome and time-consuming overall process. This significantly hinders the large-scale production and practical application of the membranes. Therefore, exploring preparation strategies that can avoid complex procedures and are more suitable for large-scale production is crucial for promoting the practical application of this technology. SUMMARY

[0007] The present application aims to overcome the deficiencies of the prior art, and provide a MOF membrane for efficient and selective separation of lithium ions and a preparation method thereof.

[0008] To achieve the object of the present application, the present application adopts the following technical solutions:

[0009] A MOF membrane for efficient and selective separation of lithium ions, the MOF membrane comprising a substrate membrane, an adhesive layer and a selective layer, wherein the substrate membrane is CEM, the adhesive layer is PVA, and the selective layer is UIO-66-SO3H.

[0010] In the present application, the adhesive layer is a PVA solution prepared.

[0011] Further, the selective layer is UIO-66-SO3H material.

[0012] Further, the mass fraction of PVA in the adhesive layer is 1.5wt%.

[0013] Further, the hydrothermal synthesis time of the selective layer is 12-36h.

[0014] The present application also provides a preparation method of the MOF membrane, wherein the preparation method comprises the following steps:

[0015] S1, dissolving ZrCl4, H2BDC and 2-NaSO3-H2BDC in DMF, then adding concentrated hydrochloric acid and acetic acid, ultrasonic treating the mixture until completely dissolved, and pouring it into a reaction kettle, then heating the reaction kettle in an oven at 80℃, then collecting UIO-66-SO3H nanoparticles by centrifugation, and then washing them with DMF and ethanol respectively for 3 times, finally drying the nanoparticles at 80℃;

[0016] S2, dissolving PVA in deionized water heated at 90℃, and then adding UIO-66-SO3H nanoparticles into the solution, ultrasonic treating the mixed solution, and cooling it to room temperature to obtain an adhesive layer solution;

[0017] S3, dissolve H2BDC and 2-NaSO3-H2BDC in DMF, then add concentrated hydrochloric acid and acetic acid, and ultrasonic until completely dissolved to prepare a ligand solution. At the same time, dissolve ZrCl4 in DMF, and ultrasonic until completely dissolved to prepare a metal salt solution. At the same time, place CEM in a 40℃ oven, and then immerse the surface of the heated film in a strong adhesive solution. After the dip coating is completed, dry and cure the film at 80℃ for 1h to form a firm and stable adhesive layer. Then, place the treated film in a wet reaction kettle, and pour the two prepared solutions into the reaction kettle, heat at 80℃, take out the MOF film, wash with DMF and ethanol, and then dry in an 80℃ oven to obtain the prepared MOF film.

[0018] The preparation method of the application first uses a hydrothermal growth method to prepare UIO-66-SO3H nanoparticles, then prepares a PVA adhesive layer solution, and finally prepares a MOF film through an adhesive-assisted growth strategy. According to the method, the lithium ion permeation and selectivity of the film are improved, the transport network is interconnected, the lithium ion transmission is faster, and the oxidation resistance is better. Compared with other methods, the method has the following advantages: the process is simple, the cost is low, the application range is wide, the selective layer formed is thin, the oxidation resistance is strong, and the modification effect is durable. In terms of stability, service life and performance, it is superior to traditional modification methods.

[0019] Further, in step S1, the mixture is ultrasonically treated for 20min, the reaction kettle is heated in an 80℃ oven for 12-36h, and the drying time is 12h.

[0020] Further, in step S2, the mass fraction of PVA in the adhesive layer solution is 1.5wt%.

[0021] Further, in step S3, the dip coating time is 5min, and the hydrothermal reaction time is 12-36h.

[0022] The application also provides the application of the MOF film in lithium resource extraction.

[0023] The MOF film provided by the application has high performance and oxidation resistance, and has a broad application prospect in lithium resource extraction.

[0024] Based on the above technical solution, the CEM used in the application is an untreated Timrun brand commercial CEM.

[0025] Compared with the prior art, the application has the following advantages:

[0026] 1) The MOF membrane provided by the application is formed through stable metal-organic coordination bonds, significantly improves the resistance to oxidative environment, can stably operate under oxidative stress conditions, avoids frequent replacement of membrane materials, and reduces maintenance cost;

[0027] 2) The MOF membrane provided by the application has a pore size that can be accurately controlled due to the presence of a thin selection layer, realizes high-selectivity separation, greatly simplifies the extraction process and improves lithium purity;

[0028] 3) The method has the characteristics of simple preparation process and high efficiency, the required equipment is all conventional instruments, the process cycle is short, there is no special requirement for the production environment, the manufacturing cost is low, and the method can be widely applied to the large-scale preparation of MOF membranes;

[0029] 4) The MOF membrane separation is a physical screening process, does not require the addition of chemical reagents, reduces secondary pollution, and the MOF membrane can be prepared on a large scale by a low-cost method, thereby reducing the comprehensive recovery cost.

[0030] 5) The MOF membrane prepared by the method can be directly integrated into existing membrane separation equipment without modifying the production line, has strong adaptability, and is suitable for industrial promotion.

[0031] 6) A biomimetic ion transport channel MOF selection layer with double nanometer confinement effect is constructed on the surface of the matrix membrane, the matrix membrane and the MOF functional layer are firmly interconnected and the transmission network is penetrated through the adhesive layer, the permeation rate and selectivity of lithium ions are significantly improved, the prepared MOF membrane exhibits excellent oxidation resistance and can effectively resist the erosion of oxidative media in actual application, thereby greatly prolonging the service life of the membrane material in harsh environments. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The scanning electron microscope surface images of the membranes M0 and M3 prepared in Comparative Example 1 and Example 3 are shown in the following figure;

[0033] Figure 2 The scanning electron microscope cross-sectional image of the membrane M3 prepared in Example 3 is shown in the following figure;

[0034] Figure 3 The atomic force microscope images of the membranes M0 and M3 prepared in Comparative Example 1 and Example 3 are shown in the following figure;

[0035] Figure 4 The ion flux comparison graphs of M1-M5 in Examples 1-5 and M0 in Comparative Example 1 are shown in the following figure;

[0036] Figure 5 The ion selectivity comparison graphs of M1-M5 in Examples 1-5 and M0 in Comparative Example 1 are shown in the following figure;

[0037] Figure 6The antioxidation performance comparison chart of M1-M5 in examples 1-5 and M0 in comparative example 1. DETAILED DESCRIPTION

[0038] The following is a detailed description of the application, the described examples are intended to further illustrate the application, and not to limit the scope of the application.

[0039] The technical solutions in the embodiments of the application will be described clearly and completely in the following with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing the specific embodiments only and is not intended to be limiting of the application.

[0041] Example 1

[0042] A MOF membrane for high-efficiency selective separation of lithium ions, wherein the MOF membrane comprises a substrate membrane, an adhesive layer and a selection layer, the substrate membrane is CEM, the adhesive layer is PVA, and the selection layer is UIO-66-SO3H, which is prepared by the following steps:

[0043] S1, dissolve ZrCl4(0.481g), H2BDC(0.243g) and a certain amount of 2-NaSO3-H2BDC in 70mL DMF, then add 5mL concentrated hydrochloric acid and 5mL acetic acid. The mixture is ultrasonically treated for 20min until completely dissolved, and then poured into a reaction kettle. After that, the reaction kettle is heated in an oven at 80℃ for 12h. Then, the UIO-66-SO3H nanoparticles are collected by centrifugation, and then washed with DMF and ethanol respectively for 3 times. Finally, the nanoparticles are dried at 80℃ for 12h;

[0044] S2, dissolve 1.5wt% PVA in deionized water heated at 90℃. And add an appropriate amount of UIO-66-SO3H nanoparticles into the solution, then ultrasonically treat the mixed solution, and cool to room temperature to obtain the adhesive layer solution;

[0045] S3, 0.243g H2BDC and 0.178g 2-NaSO3-H2BDC were dissolved in 30mL DMF, then 5mL concentrated hydrochloric acid and 5mL acetic acid were added, and ultrasonic treatment was performed until complete dissolution to prepare a ligand solution. At the same time, 0.481g ZrCl4 was dissolved in 40mL DMF, and ultrasonic treatment was performed until complete dissolution to prepare a metal salt solution. At the same time, the CEM was placed in a 40℃ oven, and then the surface of the heated membrane was immersed in a strong adhesive solution. After 5min of dip coating, the membrane was dried and cured at 80℃ for 1h to form a firm and stable adhesive layer. After that, the treated membrane was placed in a wet reaction kettle, and the two prepared solutions were poured into the reaction kettle, heated at 80℃ for 12h, and then the MOF membrane was taken out, washed with DMF and ethanol, and dried in an 80℃ oven to obtain the prepared MOF membrane, which was recorded as M1.

[0046] Example 2

[0047] A MOF membrane for efficient and selective separation of lithium ions, wherein the MOF membrane comprises a substrate membrane, an adhesive layer and a selection layer, the substrate membrane is CEM, the adhesive layer is PVA, and the selection layer is UIO-66-SO3H, which is prepared by the following steps:

[0048] S1, ZrCl4(0.481g), H2BDC(0.243g) and a certain amount of 2-NaSO3-H2BDC were dissolved in 70mL DMF, then 5mL concentrated hydrochloric acid and 5mL acetic acid were added. The mixture was ultrasonically treated for 20min until complete dissolution, and then poured into a reaction kettle. After that, the reaction kettle was heated in an oven at 80℃ for 18h. Then, the UIO-66-SO3H nanoparticles were collected by centrifugation, and then washed with DMF and ethanol respectively for 3 times. Finally, the nanoparticles were dried at 80℃ for 12h;

[0049] S2, 1.5wt% PVA was dissolved in deionized water heated at 90℃. Then a certain amount of UIO-66-SO3H nanoparticles were added to the solution, and the mixed solution was ultrasonically treated and cooled to room temperature to obtain an adhesive layer solution;

[0050] S3, 0.243g H2BDC and 0.178g 2-NaSO3-H2BDC were dissolved in 30mL DMF, then 5mL concentrated hydrochloric acid and 5mL acetic acid were added, and ultrasonic treatment was performed until complete dissolution to prepare a ligand solution. At the same time, 0.481g ZrCl4 was dissolved in 40mL DMF, and ultrasonic treatment was performed until complete dissolution to prepare a metal salt solution. At the same time, the CEM was placed in a 40℃ oven, and then the surface of the heated membrane was immersed in a strong adhesive solution. After immersion coating for 5min, the membrane was dried and cured at 80℃ for 1h to form a firm and stable adhesive layer. After that, the treated membrane was placed in a wet reaction kettle, and the two prepared solutions were poured into the reaction kettle, heated at 80℃ for 18h, and then the MOF membrane was taken out, washed with DMF and ethanol, and dried in an 80℃ oven to obtain the prepared MOF membrane, which was recorded as M2.

[0051] Example 3

[0052] A MOF membrane for efficient and selective separation of lithium ions, wherein the MOF membrane comprises a substrate membrane, an adhesive layer and a selection layer, the substrate membrane is CEM, the adhesive layer is PVA, and the selection layer is UIO-66-SO3H, which is prepared by the following steps:

[0053] S1, ZrCl4(0.481g), H2BDC(0.243g) and a certain amount of 2-NaSO3-H2BDC were dissolved in 70mL DMF, then 5mL concentrated hydrochloric acid and 5mL acetic acid were added. The mixture was ultrasonically treated for 20min until complete dissolution, and then poured into a reaction kettle. After that, the reaction kettle was heated in an oven at 80℃ for 24h. Then, the UIO-66-SO3H nanoparticles were collected by centrifugation, and then washed with DMF and ethanol respectively for 3 times. Finally, the nanoparticles were dried at 80℃ for 12h;

[0054] S2, 1.5wt% PVA was dissolved in deionized water heated at 90℃. Then a certain amount of UIO-66-SO3H nanoparticles were added to the solution, and the mixed solution was ultrasonically treated and cooled to room temperature to obtain an adhesive layer solution;

[0055] S3, 0.243g H2BDC and 0.178g 2-NaSO3-H2BDC were dissolved in 30mL DMF, then 5mL concentrated hydrochloric acid and 5mL acetic acid were added, and ultrasonic treatment was performed until complete dissolution to prepare a ligand solution. At the same time, 0.481g ZrCl4 was dissolved in 40mL DMF, and ultrasonic treatment was performed until complete dissolution to prepare a metal salt solution. At the same time, the CEM was placed in a 40℃ oven, and then the surface of the heated membrane was immersed in a strong adhesive solution. After immersion coating for 5min, the membrane was dried and cured at 80℃ for 1h to form a firm and stable adhesive layer. After that, the treated membrane was placed in a wet reaction kettle, and the two prepared solutions were poured into the reaction kettle, heated at 80℃ for 24h, and then the MOF membrane was taken out, washed with DMF and ethanol, and then placed in a 80℃ oven to dry, to obtain the prepared MOF membrane, which was recorded as M3.

[0056] Example 4

[0057] A MOF membrane for efficient and selective separation of lithium ions, wherein the MOF membrane comprises a substrate membrane, an adhesive layer and a selection layer, the substrate membrane is CEM, the adhesive layer is PVA, and the selection layer is UIO-66-SO3H, which is prepared by the following steps:

[0058] S1, ZrCl4(0.481g), H2BDC(0.243g) and a certain amount of 2-NaSO3-H2BDC were dissolved in 70mL DMF, then 5mL concentrated hydrochloric acid and 5mL acetic acid were added. The mixture was ultrasonically treated for 20min until complete dissolution, and then poured into a reaction kettle. After that, the reaction kettle was heated in an oven at 80℃ for 30h. Then, the UIO-66-SO3H nanoparticles were collected by centrifugation, and then washed with DMF and ethanol respectively for 3 times. Finally, the nanoparticles were dried at 80℃ for 12h;

[0059] S2, 1.5wt% PVA was dissolved in deionized water heated at 90℃. Then a certain amount of UIO-66-SO3H nanoparticles were added to the solution, and then the mixed solution was ultrasonically treated and cooled to room temperature to obtain an adhesive layer solution;

[0060] S3, 0.243g H2BDC and 0.178g 2-NaSO3-H2BDC were dissolved in 30mL DMF, then 5mL concentrated hydrochloric acid and 5mL acetic acid were added, and ultrasonic treatment was performed until complete dissolution to prepare a ligand solution. At the same time, 0.481g ZrCl4 was dissolved in 40mL DMF, and ultrasonic treatment was performed until complete dissolution to prepare a metal salt solution. At the same time, the CEM was placed in a 40℃ oven, and then the surface of the heated membrane was immersed in a strong adhesive solution. After immersion coating for 5min, the membrane was dried and cured at 80℃ for 1h to form a firm and stable adhesive layer. After that, the treated membrane was placed in a wet reaction kettle, and the two prepared solutions were poured into the reaction kettle, heated at 80℃ for 30h, and then the MOF membrane was taken out, washed with DMF and ethanol, and dried in an 80℃ oven to obtain the prepared MOF membrane, which was recorded as M4.

[0061] Example 5

[0062] A MOF membrane for efficient and selective separation of lithium ions, wherein the MOF membrane comprises a substrate membrane, an adhesive layer and a selection layer, the substrate membrane is CEM, the adhesive layer is PVA, and the selection layer is UIO-66-SO3H, which is prepared by the following steps:

[0063] S1, ZrCl4(0.481g), H2BDC(0.243g) and a certain amount of 2-NaSO3-H2BDC were dissolved in 70mL DMF, then 5mL concentrated hydrochloric acid and 5mL acetic acid were added. The mixture was ultrasonically treated for 20min until complete dissolution, and then poured into a reaction kettle. After that, the reaction kettle was heated in an oven at 80℃ for 36h. Then, the UIO-66-SO3H nanoparticles were collected by centrifugation, and then washed with DMF and ethanol respectively for 3 times. Finally, the nanoparticles were dried at 80℃ for 12h;

[0064] S2, 1.5wt% PVA was dissolved in deionized water heated at 90℃. Then a certain amount of UIO-66-SO3H nanoparticles were added to the solution, and the mixed solution was ultrasonically treated and cooled to room temperature to obtain an adhesive layer solution;

[0065] S3, 0.243 g H2BDC and 0.178 g 2-NaSO3-H2BDC were dissolved in 30 mL DMF, then 5 mL concentrated hydrochloric acid and 5 mL acetic acid were added, and ultrasonic was applied until complete dissolution to prepare a ligand solution. Meanwhile, 0.481 g ZrCl4 was dissolved in 40 mL DMF, and ultrasonic was applied until complete dissolution to prepare a metal salt solution. Meanwhile, the CEM was placed in a 40°C oven, and then the surface of the heated film was immersed in the strong adhesion solution. After immersion coating for 5 min, the film was dried and solidified at 80°C for 1 h to form a firm and stable adhesion layer. Then the treated film was placed in a wet reaction kettle, and the two prepared solutions were poured into the reaction kettle, heated at 80°C for 36 h, and then the MOF film was taken out, washed with DMF and ethanol, and dried in an 80°C oven to obtain the prepared MOF film, which was recorded as M5.

[0066] Comparative Example 1

[0067] The characterization methods used in this comparative example are the same as those in the above examples, except that the prepared MOF film is replaced by a commercial CEM before treatment, which is recorded as M0.

[0068] Test Example 1

[0069] The films of Comparative Example 1 and Example 3 were placed under a scanning electron microscope, and the surface of M0 was as shown in Figure 1 (a), and the surface and cross-section of M3 were as shown in Figure 1 (b) and 2, respectively. In addition, the films of Comparative Example 1 and Example 3 were placed under an atomic force microscope for characterization, and the images of M0 and M3 were as shown in Figure 3 (a) and 3(b), respectively.

[0070] Through comparison and analysis of the images, it can be clearly seen that the surface of the film prepared in Example 3 forms a uniform and dense selection layer, which not only confirms the successful preparation of the MOF film, but more importantly provides a reliable process verification basis for subsequent large-scale production, marking a key breakthrough in MOF film manufacturing technology.

[0071] Test Example 2

[0072] The permeability, selectivity and oxidation resistance of the films prepared in the various examples and comparative examples of the present application were investigated.

[0073] Test method: Lithium ion permeability and selectivity test method refers to the literature: D. Yang, Y. Yang, T. Wong, S. Iguodala, A. Wang, L. Lovell, F. Foglia, P. Fouquet, C. Breakwell, Z. Fan, Y. Wang, M. M. Britton, D. R. Williams, N. Shah, T. Xu, N. B. McKeown, M.-M. Titirici, K. E. Jelfs, Solution-processable polymer membranes with hydrophilic subnanometer pores for sustainable lithium extraction, Nat. Water. 3 (2025) 319-333. Among them, the anti-oxidation property is to immerse the membrane material in a 30wt% H2O2 solution for 48h, and to determine the residual weight to evaluate the anti-oxidation performance.

[0074] The test results are shown in Figure 4 , 5 and Figure 6 . Figure 4 , 5 are the lithium ion permeability and selectivity diagrams of each membrane, Figure 6 is the anti-oxidation performance diagram of each membrane. Figure 4 , 5 It can be seen that compared with CEM (M0) in Comparative Example 1, the ion flux and selectivity of the MOF membrane (M1, M2, M3, M4, M5) prepared by the method of the application are significantly improved. Figure 6 It can be seen that compared with CEM (M0) in Comparative Example 1, the anti-oxidation performance of the MOF membrane (M1, M2, M3, M4, M5) prepared by the method of the application is significantly improved. The excellent anti-oxidation performance of the ion membrane can significantly prolong its service life, avoid the destruction of the membrane structure and the failure of the functional groups caused by oxidative degradation, and thus maintain high ion selectivity and separation efficiency. In addition, it can also enhance the stability of the membrane in high pressure, strong acid / alkali or high oxidation environment, and ensure the continuity and economy of the separation process. In summary, the MOF membrane prepared by the method of the application has excellent permeability, selectivity and anti-oxidation performance.

[0075] The present application sets forth its basic principles, main technical features and innovative advantages. For those skilled in the art, the embodiments of the present application are not limited to the specific examples shown in the specification, and can be implemented in various specific forms without departing from the core concept and essential characteristics of the present application. Therefore, the examples listed in the specification should be understood as exemplary descriptions rather than restrictive provisions. The scope of protection of the present application is defined by the claims, and any equivalent transformation or modification based on the essential content of the present application should be included within the scope of protection of the present application, as long as it meets the technical features defined in the claims.

[0076] It should be noted that although the present specification is described in the form of separate embodiments, the technical solutions involved in each embodiment are not mutually independent. This separate description method is only a technical description means adopted for the convenience of understanding. Those skilled in the art should consider the specification as a whole when understanding the present application. The technical features in each embodiment can be combined or adjusted according to actual needs to form various technical solutions that those skilled in the art can understand and implement, and these solutions should be considered as the protection scope of the present application.

Claims

1. A method for MOF membrane preparation for high efficient and selective separation of lithium ion, characterized in that, Comprising the following steps: S1, dissolving ZrCl4, H2BDC and 2-NaSO3-H2BDC in DMF, adding concentrated hydrochloric acid and acetic acid, and ultrasonic treating the mixture until completely dissolved, pouring into a reaction kettle, heating to 80℃ in an oven, collecting UIO-66-SO3H nanoparticles by centrifugation, washing with DMF and ethanol for 3 times respectively, and then drying the nanoparticles; S2, dissolving PVA in deionized water at 90℃, and adding UIO-66-SO3H nanoparticles into the solution, and ultrasonic treating until cooled to room temperature; S3, dissolving H2BDC and 2-NaSO3-H2BDC in DMF, adding concentrated hydrochloric acid and acetic acid, and ultrasonic treating until completely dissolved to prepare a ligand solution; dissolving ZrCl4 in DMF, and ultrasonic treating until completely dissolved to prepare a metal salt solution; placing CEM in an oven at 40℃, then immersing the surface of the heated film in a strong adhesive solution, and after the dip coating is completed, drying and curing the film at 80℃ for 1h to form an adhesive layer; placing the treated film in a reaction kettle, and pouring the prepared two solutions into the reaction kettle for heating, taking out the MOF film, washing with DMF and ethanol, and then drying in an oven.

2. The method for preparing MOF membranes for high-efficient and selective separation of lithium ions according to claim 1, characterized in that, In step S1, the reaction kettle is heated in an 80℃ oven for 12-36h.

3. The method for preparing a MOF membrane for efficient and selective separation of lithium ions according to claim 1, characterized in that, In step S1, the nanoparticles are dried at 80℃ for 12h.

4. The method for preparing a MOF membrane for efficient and selective separation of lithium ions according to claim 1, characterized in that, In step S1, the mixture is ultrasonic treated for 20min.

5. The method for preparing a MOF membrane for efficient and selective separation of lithium ions according to claim 1, characterized in that, In step S2, the mass fraction of PVA is 1.5wt%.

6. The method for preparing a MOF membrane for efficient and selective separation of lithium ions according to claim 1, characterized in that, In step S3, the dip coating time is 5min, and the hydrothermal reaction time is 12-36h.

7. A MOF membrane prepared by the method of any one of claims 1 to 6. The MOF film comprises a matrix film, an adhesive layer and a selection layer, the matrix film is CEM, the adhesive layer is PVA, and the selection layer is UIO-66-SO3H.

8. The MOF film of claim 7, wherein, The MOF film is applied to the extraction of lithium resources.

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