A kind of MOF membrane for lithium ion high-efficiency selective separation, its preparation method and MOF membrane

Abstract

This invention belongs to the field of membrane separation technology, specifically relating to a method for preparing a MOF membrane for efficient and selective separation of lithium ions and the MOF membrane itself. The MOF membrane comprises a matrix membrane, an adhesive layer, and a selective layer. The matrix membrane is CEM, the adhesive layer is PVA, and the selective layer is UIO-66-SO3H. This invention proposes an adhesive-assisted growth strategy to construct a biomimetic ion transport channel MOF selective layer with a dual nano-confinence effect on the surface of the matrix membrane. This design achieves a strong interconnection and transport network between the matrix membrane and the MOF functional layer through the adhesive layer, significantly improving the permeation rate and selectivity of lithium ions. The prepared MOF membrane exhibits excellent antioxidant properties and can effectively resist the erosion of oxidizing media in practical applications, thereby greatly extending the service life of the membrane material in harsh environments.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, specifically relating to a membrane for the efficient and selective separation of lithium ions, its preparation method, and MOF membrane. Background Technology

[0002] Driven by both the global energy transition and the goal of carbon neutrality, energy storage systems, as a key infrastructure supporting the large-scale application of new energy sources and grid stability, have entered a period of rapid development. Lithium-ion batteries, as a core energy storage technology, are experiencing explosive market demand. This growth has brought unprecedented opportunities for upstream lithium resource extraction technologies, driving breakthroughs in innovative processes such as lithium extraction from low-grade brine in salt lakes. Improving lithium extraction efficiency through technological innovation is becoming 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 ponds and spodumene mining) are facing severe environmental and sustainability challenges: evaporation ponds not only consume large amounts of land and water resources but also easily lead to soil salinization and ecological degradation; while hard rock mining suffers from low ore grade, high energy consumption, and severe tailings pollution, resulting in low resource utilization and high environmental costs. Against this backdrop, developing new green and low-carbon extraction technologies has become an industry consensus, with lithium extraction from salt lakes emerging as a key direction due to its advantages of large resource reserves and low energy consumption. This technology aims to directly extract lithium from salt lake brine, and its core challenge lies in achieving efficient separation of magnesium and lithium ions. Because the hydrated ionic radii of the two are similar and their chemical properties are alike, traditional methods are difficult to use for separation, 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 emerging such as adsorption and membrane-based separation (e.g., reverse osmosis and nanofiltration). Among these, selective electrodialysis (SEED) has attracted considerable attention due to its high efficiency and sustainability. This technology relies on an electric field-driven ion exchange membrane (IEM) to achieve precise lithium-ion separation. It can be coupled with other processes and can be integrated with renewable energy sources, exhibiting both environmental friendliness and economic feasibility. However, developing ion exchange membranes with high lithium-ion selectivity remains a core challenge. Such membrane materials need to achieve precise lithium-ion identification in complex solution environments. Breakthroughs in this area are crucial not only for the lithium extraction industry but will also drive the development of related fields such as desalination, resource recovery, and electrochemical energy storage. Traditional polymer cation exchange membranes are limited by the inherent properties of the materials themselves, while novel membrane materials, with their tunable pore structures and surface chemistry, exhibit superior ion selectivity, transport efficiency, and stability, potentially bringing revolutionary progress to lithium resource extraction and even industrial separation technologies.

[0005] MOFs, as crystalline porous materials formed by the self-assembly of metal nodes and organic ligands, have become an ideal platform for constructing high-performance ion-selective separation membranes due to their highly ordered pore structure and precisely tunable pore size. 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 rationally designing assembly strategies for metal clusters and functionalized ligands, enabling efficient recognition and selective transport of target ions. The transport behavior of ions within these channels is synergistically regulated by multiple mechanisms, including size sieving, Donan repulsion, ion dehydration effects, and diffusion within the pores. Key influencing factors include pore size, surface chemistry, charge distribution, hydration state, and ion-pore interactions. Water-stable MOF materials, represented by UIO-66, have shown broad application prospects in nanofluidic devices, seawater desalination, and ion separation due to their excellent structural stability and tunability.

[0006] Chinese invention patent application number 201911379573.9 discloses a method for preparing defect-free MOF-801 membranes, primarily providing a novel method for preparing defect-free metal-organic framework thin films, offering high-performance selective films for the separation field. While this method successfully obtains MOF membranes, the complex post-processing steps result in a cumbersome and time-consuming overall process, significantly hindering the large-scale production and practical application of the membranes. Therefore, exploring preparation strategies that circumvent complex processes and are more suitable for large-scale production has become crucial for promoting the practical application of this technology. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a MOF membrane for efficient and selective separation of lithium ions and its preparation method. This membrane utilizes an "adhesion-assisted growth" strategy to construct a functionalized selective layer on its surface. The sulfonated biomimetic ion channels effectively enhance the permeation rate and selectivity of lithium ions. The adhesive layer promotes tight connectivity and interconnection of the transport network between the matrix membrane and the MOF layer, thereby significantly accelerating ion transport. Furthermore, this MOF membrane possesses excellent antioxidant properties, further expanding its application potential in harsh environments.

[0008] To achieve the objectives of this invention, the following technical solution is adopted:

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

[0010] In this invention, the adhesive layer is a prepared PVA solution.

[0011] Furthermore, the selection layer is made of UIO-66-SO3H material.

[0012] Furthermore, the PVA content in the adhesive layer is 1.5 wt%.

[0013] Furthermore, the hydrothermal synthesis time of the selective layer is 12 to 36 hours.

[0014] The present invention also provides a method for preparing the aforementioned MOF membrane, wherein the preparation method comprises the following steps:

[0015] S1. Dissolve ZrCl4, H2BDC, and 2-NaSO3-H2BDC in DMF, then add concentrated hydrochloric acid and acetic acid. Sonicate the mixture until completely dissolved, then pour it into a reaction vessel. The reaction vessel is then heated in an oven at 80°C. UIO-66-SO3H nanoparticles are then collected by centrifugation and washed three times with DMF and ethanol, respectively. Finally, the nanoparticles are dried at 80°C.

[0016] S2. Dissolve PVA in deionized water heated to 90℃. Add UIO-66-SO3H nanoparticles to the solution, then sonicate the mixture and cool it to room temperature to obtain the adhesive layer solution.

[0017] S3. Dissolve H₂BDC and 2-NaSO₃-H₂BDC in DMF, then add concentrated hydrochloric acid and acetic acid, and sonicate until completely dissolved to prepare a ligand solution. Simultaneously, dissolve ZrCl₄ in DMF and sonicate until completely dissolved to prepare a metal salt solution. Place the CEM in a 40℃ oven, then immerse the heated membrane surface in a strong adhesive solution. After dip-coating, dry and cure the membrane at 80℃ for 1 hour to form a strong and stable adhesive layer. Then, place the treated membrane in a moistened reaction vessel, pour in the two prepared solutions, heat to 80℃, remove the MOF membrane, wash with DMF and ethanol, and dry in an 80℃ oven to obtain the prepared MOF membrane.

[0018] The preparation method of this invention first uses a hydrothermal growth method to prepare UIO-66-SO3H nanoparticles, then prepares a PVA binder layer solution, and finally prepares a MOF membrane through a binder-assisted growth strategy. The method not only improves the lithium-ion permeability and selectivity of the membrane, but also enables interconnection of the transport network, promoting faster lithium-ion transport and exhibiting better antioxidant properties. Compared with other methods, this method has the following advantages: the process is simple, low-cost, and widely applicable; the formed selective layer is thin, with strong antioxidant properties and long-lasting modification effects. It is superior to traditional modification methods in terms of stability, service life, and performance.

[0019] Furthermore, in step S1, the ultrasonic treatment of the mixture lasts for 20 minutes, the reaction vessel is heated in an 80°C oven for 12–36 hours, and the drying time is 12 hours.

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

[0021] Furthermore, in step S3, the dipping time is 5 minutes, and the hydrothermal reaction time is 12–36 hours.

[0022] The present invention also provides the application of the MOF membrane in lithium resource extraction.

[0023] The MOF membrane provided by this invention has high performance and antioxidant properties, and has broad application prospects in lithium resource extraction.

[0024] Based on the above technical solution, the CEM used in this invention is an untreated Tingrun brand commercial CEM.

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

[0026] 1) The MOF membrane provided by this invention is formed through stable metal-organic coordination bonds, which significantly improves the tolerance to oxidative environments and can operate stably under oxidative stress conditions, avoiding frequent replacement of membrane materials and reducing maintenance costs;

[0027] 2) The MOF membrane provided by this invention has a thin selective layer, which allows for precise control of pore size, achieving highly selective separation, greatly simplifying the extraction process and improving lithium purity;

[0028] 3) This method has the characteristics of simple preparation process and high efficiency. The required equipment is all conventional instruments. The process cycle is short, there are no special requirements for the production environment, and the manufacturing cost is low. It can be widely used in the large-scale preparation of MOF membranes.

[0029] 4) MOF membrane separation is a physical sieving process that does not require the addition of chemical reagents, reducing secondary pollution. Furthermore, MOF membranes can be prepared on a large scale using low-cost methods, which reduces the overall recycling cost.

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

[0031] 6) A biomimetic ion transport channel MOF selective layer with dual nano-confinence effect was constructed on the surface of the matrix membrane. The strong interconnection and transport network between the matrix membrane and the MOF functional layer were realized through the adhesive layer, which significantly improved the permeation rate and selectivity of lithium ions. The prepared MOF membrane exhibited excellent antioxidant properties and could effectively resist the corrosion of oxidizing media in practical applications, thereby greatly extending the service life of the membrane material in harsh environments. Attached Figure Description

[0032] Figure 1 The images are scanning electron microscope (SEM) surface images of the films M0 and M3 prepared in Comparative Example 1 and Example 3.

[0033] Figure 2 This is a scanning electron microscope cross-sectional image of the membrane M3 prepared in Example 3;

[0034] Figure 3 Atomic force microscopy images of membranes M0 and M3 prepared in Comparative Example 1 and Example 3;

[0035] Figure 4 This is a comparison chart of the ion flux of M1 to M5 in Examples 1 to 5 and M0 in Comparative Example 1;

[0036] Figure 5 This is a comparison chart of the ion selectivity of M1 to M5 in Examples 1 to 5 and M0 in Comparative Example 1;

[0037] Figure 6 This is a comparison chart of the antioxidant properties of M1 to M5 in Examples 1 to 5 and M0 in Comparative Example 1. Detailed Implementation

[0038] The following are specific embodiments of the present invention. The described embodiments are intended to further illustrate the present invention, but are not intended to limit the scope of the present invention.

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[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 invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0041] Example 1

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

[0043] S1. Dissolve ZrCl4 (0.481 g), H2BDC (0.243 g), and a certain amount of 2-NaSO3-H2BDC in 70 mL of DMF, then add 5 mL of concentrated hydrochloric acid and 5 mL of acetic acid. Sonicate the mixture for 20 min until completely dissolved, then pour it into a reaction vessel. Afterward, heat the reaction vessel in an oven at 80 °C for 12 h. Then, collect the UIO-66-SO3H nanoparticles by centrifugation, and wash them three times with DMF and ethanol, respectively. Finally, dry the nanoparticles at 80 °C for 12 h.

[0044] S2. Dissolve 1.5 wt% PVA in deionized water heated to 90°C. Add an appropriate amount of UIO-66-SO3H nanoparticles to the solution, then sonicate the mixture and cool it to room temperature to obtain the adhesive layer solution.

[0045] S3. Dissolve 0.243g H2BDC and 0.178g 2-NaSO3-H2BDC in 30mL DMF, then add 5mL concentrated hydrochloric acid and 5mL acetic acid, and sonicate until completely dissolved to prepare a ligand solution. Simultaneously, dissolve 0.481g ZrCl4 in 40mL DMF and sonicate until completely dissolved to prepare a metal salt solution. Place the CEM in a 40℃ oven, then immerse the heated membrane surface in a strong adhesive solution. After immersion for 5 minutes, dry and cure the membrane at 80℃ for 1 hour to form a strong and stable adhesive layer. Then place the treated membrane in a moistened reaction vessel, pour in the two prepared solutions, heat at 80℃ for 12 hours, remove the MOF membrane, wash with DMF and ethanol, and dry in an 80℃ oven to obtain the prepared MOF membrane, denoted as M1.

[0046] Example 2

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

[0048] S1. Dissolve ZrCl4 (0.481 g), H2BDC (0.243 g), and a certain amount of 2-NaSO3-H2BDC in 70 mL of DMF, then add 5 mL of concentrated hydrochloric acid and 5 mL of acetic acid. Sonicate the mixture for 20 min until completely dissolved, then pour it into a reaction vessel. Afterward, heat the reaction vessel in an oven at 80 °C for 18 h. Then, collect the UIO-66-SO3H nanoparticles by centrifugation, and wash them three times with DMF and ethanol, respectively. Finally, dry the nanoparticles at 80 °C for 12 h.

[0049] S2. Dissolve 1.5 wt% PVA in deionized water heated to 90°C. Add an appropriate amount of UIO-66-SO3H nanoparticles to the solution, then sonicate the mixture and cool it to room temperature to obtain the adhesive layer solution.

[0050] S3. Dissolve 0.243g H2BDC and 0.178g 2-NaSO3-H2BDC in 30mL DMF, then add 5mL concentrated hydrochloric acid and 5mL acetic acid, and sonicate until completely dissolved to prepare a ligand solution. Simultaneously, dissolve 0.481g ZrCl4 in 40mL DMF and sonicate until completely dissolved to prepare a metal salt solution. Place the CEM in a 40℃ oven, then immerse the heated membrane surface in a strong adhesive solution. After immersion for 5 minutes, dry and cure the membrane at 80℃ for 1 hour to form a strong and stable adhesive layer. Then place the treated membrane in a moistened reaction vessel, pour in the two prepared solutions, heat at 80℃ for 18 hours, remove the MOF membrane, wash with DMF and ethanol, and dry in an 80℃ oven to obtain the prepared MOF membrane, denoted as M2.

[0051] Example 3

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

[0053] S1. Dissolve ZrCl4 (0.481 g), H2BDC (0.243 g), and a certain amount of 2-NaSO3-H2BDC in 70 mL of DMF, then add 5 mL of concentrated hydrochloric acid and 5 mL of acetic acid. Sonicate the mixture for 20 min until completely dissolved, then pour it into a reaction vessel. Afterward, heat the reaction vessel in an oven at 80 °C for 24 h. Then, collect the UIO-66-SO3H nanoparticles by centrifugation, and wash them three times with DMF and ethanol, respectively. Finally, dry the nanoparticles at 80 °C for 12 h.

[0054] S2. Dissolve 1.5 wt% PVA in deionized water heated to 90°C. Add an appropriate amount of UIO-66-SO3H nanoparticles to the solution, then sonicate the mixture and cool it to room temperature to obtain the adhesive layer solution.

[0055] S3. Dissolve 0.243g H2BDC and 0.178g 2-NaSO3-H2BDC in 30mL DMF, then add 5mL concentrated hydrochloric acid and 5mL acetic acid, and sonicate until completely dissolved to prepare a ligand solution. Simultaneously, dissolve 0.481g ZrCl4 in 40mL DMF and sonicate until completely dissolved to prepare a metal salt solution. Place the CEM in a 40℃ oven, then immerse the heated membrane surface in a strong adhesive solution. After immersion for 5 minutes, dry and cure the membrane at 80℃ for 1 hour to form a strong and stable adhesive layer. Then place the treated membrane in a moistened reaction vessel, pour in the two prepared solutions, heat at 80℃ for 24 hours, remove the MOF membrane, wash with DMF and ethanol, and dry in an 80℃ oven to obtain the prepared MOF membrane, denoted as M3.

[0056] Example 4

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

[0058] S1. Dissolve ZrCl4 (0.481 g), H2BDC (0.243 g), and a certain amount of 2-NaSO3-H2BDC in 70 mL of DMF, then add 5 mL of concentrated hydrochloric acid and 5 mL of acetic acid. Sonicate the mixture for 20 min until completely dissolved, then pour it into a reaction vessel. Afterward, heat the reaction vessel in an oven at 80 °C for 30 h. Then, collect the UIO-66-SO3H nanoparticles by centrifugation, and wash them three times with DMF and ethanol, respectively. Finally, dry the nanoparticles at 80 °C for 12 h.

[0059] S2. Dissolve 1.5 wt% PVA in deionized water heated to 90°C. Add an appropriate amount of UIO-66-SO3H nanoparticles to the solution, then sonicate the mixture and cool it to room temperature to obtain the adhesive layer solution.

[0060] S3. Dissolve 0.243g H2BDC and 0.178g 2-NaSO3-H2BDC in 30mL DMF, then add 5mL concentrated hydrochloric acid and 5mL acetic acid, and sonicate until completely dissolved to prepare a ligand solution. Simultaneously, dissolve 0.481g ZrCl4 in 40mL DMF and sonicate until completely dissolved to prepare a metal salt solution. Place the CEM in a 40℃ oven, then immerse the heated membrane surface in a strong adhesive solution. After immersion for 5 minutes, dry and cure the membrane at 80℃ for 1 hour to form a strong and stable adhesive layer. Then place the treated membrane in a moistened reaction vessel, pour in the two prepared solutions, heat at 80℃ for 30 hours, remove the MOF membrane, wash with DMF and ethanol, and dry in an 80℃ oven to obtain the prepared MOF membrane, denoted as M4.

[0061] Example 5

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

[0063] S1. Dissolve ZrCl4 (0.481 g), H2BDC (0.243 g), and a certain amount of 2-NaSO3-H2BDC in 70 mL of DMF, then add 5 mL of concentrated hydrochloric acid and 5 mL of acetic acid. Sonicate the mixture for 20 min until completely dissolved, then pour it into a reaction vessel. Afterward, heat the reaction vessel in an oven at 80 °C for 36 h. Then, collect the UIO-66-SO3H nanoparticles by centrifugation, and wash them three times with DMF and ethanol, respectively. Finally, dry the nanoparticles at 80 °C for 12 h.

[0064] S2. Dissolve 1.5 wt% PVA in deionized water heated to 90°C. Add an appropriate amount of UIO-66-SO3H nanoparticles to the solution, then sonicate the mixture and cool it to room temperature to obtain the adhesive layer solution.

[0065] S3. Dissolve 0.243g H2BDC and 0.178g 2-NaSO3-H2BDC in 30mL DMF, then add 5mL concentrated hydrochloric acid and 5mL acetic acid, and sonicate until completely dissolved to prepare a ligand solution. Simultaneously, dissolve 0.481g ZrCl4 in 40mL DMF and sonicate until completely dissolved to prepare a metal salt solution. Place the CEM in a 40℃ oven, then immerse the heated membrane surface in a strong adhesive solution. After immersion for 5 minutes, dry and cure the membrane at 80℃ for 1 hour to form a strong and stable adhesive layer. Then place the treated membrane in a moistened reaction vessel, pour in the two prepared solutions, heat at 80℃ for 36 hours, remove the MOF membrane, wash with DMF and ethanol, and dry in an 80℃ oven to obtain the prepared MOF membrane, denoted as M5.

[0066] Comparative Example 1

[0067] The characterization method used in this comparative example is the same as that in the above examples, except that the prepared MOF membrane is replaced with a commercial CEM before treatment, denoted as M0.

[0068] Experimental Example 1

[0069] The films of Comparative Example 1 and Example 3 were observed under a scanning electron microscope. The surface of M0 was as follows: Figure 1 As shown in (a), the surface and cross-section of M3 are respectively as follows: Figure 1 (b) As shown in Figure 2. Furthermore, the films of Comparative Example 1 and Example 3 were characterized under an atomic force microscope, and the images of M0 and M3 are shown below. Figure 3 As shown in (a) and 3(b).

[0070] Through image comparison and analysis, it can be clearly seen that a uniform and dense selective layer is formed on the surface of the membrane prepared in Example 3. This characteristic morphology not only confirms the successful preparation of the MOF membrane, but more importantly, it provides a reliable process verification basis for subsequent large-scale production, marking a key breakthrough in MOF membrane manufacturing technology.

[0071] Experimental Example 2

[0072] This test case investigated the permeation performance, selectivity, and antioxidant performance of the membranes prepared in the various embodiments and comparative examples of the present invention.

[0073] Experimental methods: The lithium-ion permeability and selectivity test methods were referenced in: D. Yang, Y. Yang, T. Wong, S. Iguodala, A. Wang, L. Lovell, F. Foglia, P. Fouquet, C. Breakwell, Z. Fan, Y. Wang, M. Britton, D. D. Williams, N. Shah, T. Xu, N. B. McKeown, M.-M. Titirici, K. E. Jelfs, Q. Song, Solution-processable polymer membranes with hydrophilic subnanometrepores for sustainable lithium extraction, Nat. Water. 3(2025) 319-333. Among these, the antioxidant property was assessed by immersing the membrane material in a 30 wt% H2O2 solution for 48 h and measuring the remaining weight.

[0074] The test results are as follows Figure 4 , 5 and Figure 6 As shown. Figure 4 , 5 The figures show the lithium-ion permeability and selectivity of each membrane. Figure 6 The graph shows the antioxidant properties of each membrane. Figure 4 , 5 As can be seen, compared with CEM(M0) in Comparative Example 1, the MOF membranes (M1, M2, M3, M4, M5) prepared by the method of the present invention have significantly improved ion flux and selectivity. Figure 6 As can be seen, compared with CEM(M0) in Comparative Example 1, the MOF membranes (M1, M2, M3, M4, M5) prepared by the method of this invention exhibit significantly improved antioxidant properties. The excellent antioxidant properties of the ion exchange membrane can significantly extend its service life, avoiding membrane structure damage and functional group failure caused by oxidative degradation, thereby maintaining high ion selectivity and separation efficiency. Furthermore, it can enhance the stability of the membrane under high pressure, strong acid / alkali, or highly oxidizing environments, ensuring the continuity and economy of the separation process. In summary, the MOF membranes prepared by the method of this invention possess excellent permeation performance, selectivity, and antioxidant properties.

[0075] This invention elucidates its basic principles, main technical features, and innovative advantages. For those skilled in the art, the implementation of this invention is not limited to the specific embodiments shown in the specification; it can be implemented in various specific forms without departing from the core concept and essential characteristics of this invention. Therefore, the embodiments listed in this specification should be understood as illustrative rather than restrictive. The scope of protection of this invention is defined by the claims. Any equivalent transformations or modifications made based on the substantive content of this invention, as long as they conform to the technical features defined in the claims, should be included within the scope of protection of this invention.

[0076] It should be noted that although this specification describes the invention using a segmented approach, the technical solutions involved in each embodiment are not independent of each other. This segmented approach is merely a technical description method used for ease of understanding. Those skilled in the art should consider the specification as an organic whole when understanding this invention. The technical features in each embodiment can be combined or adjusted according to actual needs to form various technical solutions that can be understood and implemented by those skilled in the art, and all of these solutions should be considered within the scope of protection covered by this invention.

Claims

1. A method for preparing a MOF membrane for efficient and selective separation of lithium ions, characterized in that, Includes the following steps: S1. Dissolve ZrCl4, H2BDC and 2-NaSO3-H2BDC in DMF, add concentrated hydrochloric acid and acetic acid, sonicate the mixture until completely dissolved, pour into a reaction vessel and heat to 80°C in an oven, collect UIO-66-SO3H nanoparticles by centrifugation, wash with DMF and ethanol three times respectively, and then dry the nanoparticles. S2. Dissolve PVA in deionized water at 90℃, add UIO-66-SO3H nanoparticles to the solution, perform ultrasonic treatment, and cool to room temperature to obtain an adhesive solution. S3. Dissolve H2BDC and 2-NaSO3-H2BDC in DMF, add concentrated hydrochloric acid and acetic acid, and sonicate until completely dissolved to prepare a ligand solution; dissolve ZrCl4 in DMF and sonicate until completely dissolved to prepare a metal salt solution; place the CEM in an oven at 40℃, then immerse the heated membrane surface in a strong adhesive solution. After dip coating, dry and cure the membrane at 80℃ for 1 hour to form an adhesive layer; place the treated membrane in a reaction vessel, pour the prepared ligand solution and metal salt solution into the reaction vessel, and heat for hydrothermal reaction. Remove the MOF membrane, wash it with DMF and ethanol, and then dry it in an oven.

2. 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 reactor is heated in an 80°C oven for 12–36 hours.

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°C for 12 hours.

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 ultrasonic treatment of the mixture lasts for 20 minutes.

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 percentage of PVA is 1.5 wt%.

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 dipping time is 5 minutes, and the hydrothermal reaction time is 12 to 36 hours.

7. A MOF membrane prepared using the MOF membrane preparation method for efficient and selective separation of lithium ions as described in any one of claims 1 to 6, characterized in that, The MOF membrane comprises a matrix membrane, an adhesive layer, and a selective layer. The matrix membrane is CEM, the adhesive layer is PVA, and the selective layer is UIO-66-SO3H.

8. The MOF membrane according to claim 7, characterized in that, The MOF membrane is used for lithium extraction.

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