A hydrogen-bonded organic framework membrane with tunable pore environment, its preparation method and application

Abstract

This invention discloses a hydrogen-bonded organic framework membrane with tunable pore environment, its preparation method, and its applications. The method first forms oligomeric building blocks through confined condensation at the liquid-liquid interface, and then effectively suppresses random nucleation and island crystallization through hydrogen-bonded supramolecular crystallization and ordered self-assembly, promoting lateral bonding and defect self-correction at the interface. This results in a continuous, dense, crack-free, uniformly thick hydrogen-bonded organic framework membrane with regular nanochannels. By selecting aldehyde-containing linkers with different structures, while maintaining a basic consistency between the framework topology and channel geometry, the chemical microenvironment of the pore wall, especially the density of heteroatom sites, can be tunably constructed, thereby achieving control over Cs. + / Sr 2+ Cs + / La 3+ and Cs + / Zr 4+ The system exhibits high selectivity for separation, good separation performance, structural stability, and promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation materials and nuclear waste treatment technology, specifically relating to a hydrogen-bonded organic framework membrane with adjustable pore environment, its preparation method and application. Background Technology

[0002] With the development of nuclear energy development and utilization, radioactive waste treatment, and related resource recycling technologies, the efficient separation and selective removal of metal ions in complex systems has attracted increasing attention. Especially in fields such as nuclear waste, metallurgical separation, and the preparation of special functional materials, metal ions with different valence states, different hydration characteristics, and different migration behaviors often coexist in solution systems. How to achieve highly selective separation of target ions has always been an important research direction in the fields of separation science and membrane technology.

[0003] Currently, membrane separation technology shows promising application prospects in the field of ion separation due to its advantages such as low energy consumption, continuous process, compact device, ease of scale-up, and modular integration. However, existing membrane separation processes mainly rely on mechanisms such as pore size sieving, surface charge interaction, concentration-driven processes, or coordination adsorption. For complex metal ion systems with significant competitive transport, it is often difficult to simultaneously achieve high selectivity, high throughput, and good stability. Especially in sub-nanometer confined transport processes, factors such as ion size, hydration structure, interfacial interactions, desolvation behavior, and migration barriers are coupled, making it difficult for traditional separation mechanisms to achieve precise differentiation and effective control of different metal ions.

[0004] Inspired by the selective transport mechanism of biological ion channels, if an ordered and tunable chemical microenvironment can be constructed on the inner wall of membrane pores, it is hoped that differentiated recognition and selective transport of different metal ions can be achieved by regulating the adsorption, desolvation, and migration behavior of ions during transport. Therefore, crystalline porous materials with regular pore structure and designable pore wall environment are considered important candidate systems for constructing high-performance ion separation membranes.

[0005] Hydrogen-bonded organic frameworks (HFRs), a class of crystalline porous materials constructed based on intermolecular hydrogen bonding, possess characteristics such as designable structure, regular pores, easily tunable functional sites, and expandable composition, demonstrating potential application value in molecular recognition, separation and purification, and ion transport. If constructed as continuous membranes, they are expected to combine the ordered transport advantages of crystalline channels with the engineering application advantages of membrane separation processes, thus providing a new technical pathway for the efficient and selective separation of complex metal ion systems.

[0006] However, existing hydrogen-bonded organic framework materials are mostly assembled through reversible non-covalent interactions. During the film formation process, problems such as random nucleation, discrete grain growth, and insufficient film continuity can easily occur. As a result, the obtained film materials are prone to defects such as intergranular defects, non-selective transport channels, and insufficient structural stability, which limits their separation performance and practical applications.

[0007] Furthermore, existing technologies still lack effective solutions for how to further regulate the chemical environment of the pore walls while maintaining the continuity of the membrane and the orderliness of the pores, so as to achieve differentiated transport and highly selective separation of different metal ions, especially metal ions with different valence states.

[0008] Therefore, developing a hydrogen-bonded organic framework membrane with a continuous structure, few defects, tunable pore microenvironment, and suitable for the selective separation of metal ions is of great significance for improving the separation efficiency and selectivity of target metal ions in complex systems. Summary of the Invention

[0009] The technical problem to be solved by this invention is to provide a hydrogen-bonded organic framework membrane with tunable pore environment, its preparation method, and its application. This method utilizes a coupling mechanism of liquid-liquid interface confined condensation and hydrogen bond-guided supramolecular crystallization to form a continuous, dense hydrogen-bonded organic framework membrane with regular nanochannels. Furthermore, by selecting aldehyde-containing linkers with different structures, the chemical microenvironment of the membrane pore walls can be controlled, achieving selective separation of metal ions with different valence states.

[0010] To address the above technical problems, this invention discloses a method for preparing a hydrogen-bonded organic framework membrane with tunable pore environment, comprising the following steps:

[0011] (1) The aqueous phase containing polyamine monomers and the organic phase containing aldehyde linkers are placed on both sides of a porous support substrate. The aqueous phase containing polyamine monomers and the organic phase containing aldehyde linkers are in contact to form a liquid-liquid interface. The porous support substrate is pre-fixed in the center of the membrane pool to support the hydrogen-bonded organic framework selective membrane layer formed subsequently. The hydrogen-bonded organic framework composite membrane obtained in this way has good mechanical stability.

[0012] (2) The polyamine monomer and the aldehyde-containing linker first undergo a confined condensation reaction at the liquid-liquid interface to form discrete oligomeric building units. These discrete oligomeric building units grow laterally and continuously in the interface plane through hydrogen bonding and supramolecular crystallization to form a hydrogen-bonded organic framework selective layer.

[0013] (3) After the reaction is complete, the hydrogen-bonded organic framework selective layer is washed, dried or solvent-replaced to obtain a hydrogen-bonded organic framework film.

[0014] Furthermore, the specific steps include:

[0015] (1) Dissolve the polyamine monomer in an acidic aqueous solution to prepare an aqueous solution with a concentration of 0.01 to 5 mmol / L; dissolve the aldehyde linker in an organic solvent to prepare an organic solution with a concentration of 0.04 to 20 mmol / L; place the aqueous solution and the organic solution on both sides of a porous support substrate, and the aqueous solution and the organic solution are in contact to form a liquid-liquid interface;

[0016] (2) Under the conditions of 0 to 80 °C (preferably 35 °C), the polyamine monomer and the aldehyde-containing linker first undergo a confined condensation reaction in the interface region formed above, forming discrete oligomeric building units in situ. These building units are interconnected in an ordered manner through hydrogen bonding and supramolecular crystallization, and grow laterally and continuously in the interface plane to form a hydrogen-bonded organic framework selective layer.

[0017] The above reaction belongs to the coupling mechanism of confined imine condensation and hydrogen bond-directed supramolecular assembly. At the liquid-liquid interface, the amino group on the polyamine monomer first undergoes a condensation reaction with an aldehyde group in the aldehyde-containing linker to form discrete oligomeric building units in situ. Subsequently, these discrete oligomeric building units achieve ordered interconnection and assembly through hydrogen bonding with unreacted aldehyde groups or other hydrogen bond donors, or through hydrogen bonding between aldehyde groups and other hydrogen bond donors, combined with the supramolecular crystallization process.

[0018] Because the above process is regulated by the spatial confinement effect of the liquid-liquid interface, it can effectively suppress random nucleation and island crystallization, and promote the lateral continuous growth of the film along the interface plane, ultimately forming a continuous, dense hydrogen-bonded organic framework film with a crystalline ordered structure.

[0019] (3) After the reaction is complete, the hydrogen-bonded organic framework selective layer is washed with organic solvent, lower alcohol and deionized water in sequence (to remove unreacted monomers and physically adsorbed impurities), and then dried or solvent replaced to obtain hydrogen-bonded organic framework film.

[0020] Furthermore, in step (1), the polyamine monomer is selected from polyamine monomers having a tetrahedral configuration, and the aldehyde-containing linker is selected from aromatic dialdehyde linkers or linkers containing one aldehyde group and one hydrogen bond donor; the hydrogen bond donor is a carboxyl group, aldehyde group, hydroxyl group, hydrazine, amide or acylhydrazine.

[0021] Further, in step (1), the polyamine monomer is selected from one or more of tetra(4-aminophenyl)methane, tetra(4-aminophenyl)silane, tetra(4-amino-3-hydroxyphenyl)methane, 2,2',7,7'-tetraamino-9,9'-spirodifluorene, 2,2',7,7'-tetraamino-3,3',6,6'-tetramethyl-9,9'-spirodifluorene, 1,3,5,7-tetra(4-aminophenyl)adamantane, pentaerythritol tetra(4-aminophenyl) ether, 3,3',5,5'-tetra(4-aminophenyl)-2,2',6,6'-tetramethylbiphenyl, and 2,2',6,6'-tetra(4-aminophenyl)-3,3',5,5'-tetramethylbiphenyl.

[0022] The aldehyde-containing linker is selected from one or more of 2,2'-bipyridine-5,5'-dicarboxaldehyde, 2,2'-bipyrimidine-5,5'-dicarboxaldehyde, 4'-formyl-[1,1'-biphenyl]-4-carboxylic acid, 4-(5-formylpyridin-2-yl)benzoic acid, 5-formylpyridinecarboxylic acid, 5'-formyl-[2,2'-bipyridine]-5-carboxylic acid, 5'-formyl-[2,2'-bipyrimidine]-5-carboxylic acid, 2-(5-formylpyridin-2-yl)pyrimidine-5-amine, and 2-(5-hydrazylpyrimidine-2-yl)pyridine-5-carboxaldehyde.

[0023] Furthermore, the molar ratio of the polyamine monomer to the aldehyde linker is 1:4, or close to 1:4.

[0024] Furthermore, in step (1), the acidic aqueous solution is selected from one or more of the following: acetic acid aqueous solution, trifluoroacetic acid aqueous solution, hydrochloric acid aqueous solution, sulfuric acid aqueous solution, nitric acid aqueous solution, methanesulfonic acid aqueous solution, and p-toluenesulfonic acid aqueous solution; the concentration of the acidic aqueous solution is 0.1–6 M.

[0025] The organic solvent is selected from one or more of ethyl acetate, mesitylene, toluene, dichloromethane, chloroform, benzene, and o-dichlorobenzene;

[0026] The porous support substrate is selected from one of polyacrylonitrile membrane, polyethersulfone membrane, polyvinylidene fluoride membrane, and alumina ceramic membrane, with polyacrylonitrile ultrafiltration membrane being preferred.

[0027] Furthermore, in step (3), the organic solvent is selected from one or more of ethyl acetate, mesitylene, toluene, dichloromethane, chloroform, benzene, and o-dichlorobenzene; the lower alcohol is selected from ethanol, methanol, or a mixture of the two.

[0028] Furthermore, in step (3), the solvent used in the solvent replacement treatment is a low-boiling-point polar solvent that is miscible with water, such as methanol, ethanol, etc.

[0029] The present invention also discloses a hydrogen-bonded organic framework membrane prepared by the aforementioned preparation method. The hydrogen-bonded organic framework membrane has a continuous, dense and crystalline ordered selective layer and regular nanochannels. The effective pore size of the nanochannels is 0.7 to 2.0 nm, and the membrane thickness is 50 nm to 5 μm.

[0030] This invention further discloses a hydrogen-bonded organic framework membrane prepared by the aforementioned method and its application in the selective separation of metal ions, preferably the selective separation of monovalent metal ions and multivalent metal ions, such as Cs. + With Sr 2+ La 3+ Zr 4+ Separation of other multivalent metal ions.

[0031] Methods for selective separation of metal ions: Hydrogen-bonded organic framework membranes are placed in diffusion cells, permeation cells, or electro-assisted separation devices, allowing the solutions to be separated to contact the membrane. The differential modulation of the migration energy barriers of different metal ions by the membrane pore microenvironment achieves highly selective separation of the target ions. The specific separation mechanism is as follows:

[0032] By selecting aldehyde-containing linkers with different structures, the nitrogen site density on the inner wall of the membrane pores can be controlled without changing the overall framework topology and channel geometry, making the pore microenvironment the main variable affecting the differences in ion transport. As the nitrogen site density on the pore wall increases, multivalent ions, especially high charge density ions, face higher energy barriers during pore entry, adsorption, desolvation, and migration, while monovalent ions can still achieve rapid hopping migration along low-barrier paths.

[0033] The beneficial effects of this invention are:

[0034] (1) This invention proposes a confined assembly film formation strategy mediated by interfacial chemical reaction. First, oligomeric building blocks are formed by confined condensation at the liquid-liquid interface. Then, through hydrogen bond-guided supramolecular crystallization and ordered self-assembly, random nucleation and island crystallization are effectively suppressed, and lateral bonding and defect self-correction of the film layer at the interface are promoted. Thus, a continuous, dense, crack-free, uniform thickness hydrogen bonded organic framework film with regular nanochannels is obtained.

[0035] (2) This invention can independently regulate the chemical microenvironment of the pore wall by selecting aldehyde-containing linkers with different structures while maintaining the basic stability of the pore geometry. In particular, it can systematically regulate the nitrogen site density of the pore wall, thereby effectively decoupling the geometric confinement effect from the chemical microenvironment effect, providing a new approach for constructing crystalline ion separation channels with programmable migration barriers.

[0036] (3) The hydrogen-bonded organic framework membrane constructed in this invention does not rely solely on size sieving or electrostatic repulsion, but rather establishes differentiated migration barriers for metal ions of different valence states through the synergistic regulation of ion adsorption, desolvation, and migration processes via the pore microenvironment, thereby achieving efficient and selective transport. Results show that this membrane material exhibits high efficiency for Cs... + / Sr 2+ Cs + / La 3+ and Cs + / Zr 4+ The selectivity can be as high as 2400, 17800 and >50000, Cs + Flux reached 2.1 mol / (m 2 It maintains good structural stability and separation performance even after 1000 hours of continuous operation, and is expected to be applied in fields such as nuclear waste treatment, separation of complex metal ions and related resource recovery. Attached Figure Description

[0037] Figure 1 A schematic diagram of liquid-liquid interface confined condensation-hydrogen bond self-assembly into a film;

[0038] Figure 2 MALDI-TOF plot of discrete oligomeric building blocks obtained in Example 1 (vertical axis represents signal strength, horizontal axis represents mass-to-charge ratio).

[0039] Figure 3 This is a cross-sectional SEM image of the hydrogen-bonded organic framework membrane prepared in Example 1.

[0040] Figure 4 The N2 adsorption isotherm of the hydrogen-bonded organic framework membrane prepared in Example 1 is shown in the figure (the vertical axis represents the amount of nitrogen adsorbed, and the horizontal axis represents the relative pressure).

[0041] Figure 5 The image shows the pore size distribution of the hydrogen-bonded organic framework membrane prepared in Example 1 (the vertical axis represents the pore volume change rate within a unit pore size range, and the horizontal axis represents the pore size).

[0042] In the figure: 1. Aqueous phase solution containing polyamine monomers; 2. Organic phase solution containing aldehyde linkers; 3. Porous support substrate. Detailed Implementation

[0043] The present invention will be further explained below with reference to the embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0044] In the following embodiments, the polyamine monomer is referred to as group A monomer, and its structural formula is shown in Figure (I); the aldehyde-containing linker is referred to as group B monomer, and its structural formula is shown in Figure (II).

[0045] like Figure 1 As shown in the following examples, the polyamine monomer of group A and the aldehyde-containing linker of group B form a hydrogen-bonded organic framework film at the liquid-liquid interface through confined condensation and hydrogen bond self-assembly mechanism.

[0046] Group A polyamine monomers include:

[0047] A1: Tetra(4-aminophenyl)methane; A2: Tetra(4-aminophenyl)silane; A3: Tetra(4-amino-3-hydroxyphenyl)methane; A4: 2,2',7,7'-tetraamino-9,9'-spirodifluorene; A5: 2,2',7,7'-tetraamino-3,3',6,6'-tetramethyl-9,9'-spirodifluorene; A6: 1,3,5,7-tetra(4-aminophenyl)adamantane; A7: Pentaerythritol tetra(4-aminophenyl) ether; A8: 3,3',5,5'-tetra(4-aminophenyl)-2,2',6,6'-tetramethylbiphenyl; A9: 2,2',6,6'-tetra(4-aminophenyl)-3,3',5,5'-tetramethylbiphenyl.

[0048]

[0049] (I)

[0050] Group B aldehyde-containing linkers include:

[0051] B1: 2,2'-Bipyridine-5,5'-dicarboxaldehyde; B2: 2,2'-Bipyrimidine-5,5'-dicarboxaldehyde; B3: 4'-Formyl-[1,1'-Biphenyl]-4-carboxylic acid; B4: 4-(5-Formylpyridin-2-yl)benzoic acid; B5: 5-Formylpyridinecarboxylic acid; B6: 5'-Formyl-[2,2'-Bipyrimidine]-5-carboxylic acid; B7: 5'-Formyl-[2,2'-Bipyrimidine]-5-carboxylic acid; B8: 2-(5-Formylpyridin-2-yl)pyrimidine-5-amine; B9: 2-(5-Hydroxypyrimidine-2-yl)pyridine-5-carboxaldehyde.

[0052]

[0053] (II)

[0054] Example 1

[0055] Preparation and Ion Separation Performance of A1 / B1 Combined Hydrogen-Bonded Organic Framework Membranes

[0056]

[0057] (1) The polyacrylonitrile ultrafiltration membrane was fixed in the center of the diffusion cell. Tetra(4-aminophenyl)methane (A1) was dissolved in a 1 mol / L aqueous acetic acid solution to prepare an aqueous phase solution with a concentration of 0.01 mmol / L; 2,2'-bipyridine-5,5'-dicarboxaldehyde (B1) was dissolved in a mixed solvent of ethyl acetate and mesitylene, wherein the volume ratio of ethyl acetate to mesitylene was 1:1, to prepare an organic phase solution with a concentration of 0.04 mmol / L. The prepared aqueous phase solution and organic phase solution were added to both sides of the polyacrylonitrile ultrafiltration membrane, respectively, so that the aqueous phase solution and organic phase solution came into contact and formed a liquid-liquid interface.

[0058] (2) The reaction was carried out at 35 °C for 24 h. During the reaction, A1 and B1 first underwent a confined condensation reaction at the interface region to form discrete oligomeric building units containing imine bonds. Subsequently, the discrete oligomeric building units, relying on the hydrogen bonding between unreacted functional groups and the ordered intermolecular stacking, further underwent supramolecular crystallization and lateral aggregation on the surface of the support to form a continuous and dense hydrogen-bonded organic framework selective layer.

[0059] like Figure 2 As shown, the MALDI-TOF mass spectrometry results indicate that the molecular weight of the discrete oligomeric building blocks formed above is 1153, which is consistent with the theoretical structure of the oligomeric building blocks obtained by the above reaction formula.

[0060] (3) After the reaction was completed, the hydrogen-bonded organic framework selective layer was washed with ethyl acetate, ethanol and deionized water in sequence to remove unreacted monomers and surface adsorbed impurities, and then dried under vacuum at 40 °C for 12 h to obtain the A1-B1 type hydrogen-bonded organic framework composite film.

[0061] The obtained composite membrane was characterized, such as... Figure 3 As shown, the SEM cross-sectional results indicate that the thickness of the selected layer is approximately 254 nm, with a clear film structure and distinct interfaces. Figure 4 As shown, the specific surface area of ​​this membrane material is 840 m². 2 / g. For example... Figure 5 As shown, pore size analysis results indicate that the effective pore size of the membrane is approximately 1.06 nm.

[0062] The ion separation performance of the obtained composite membrane was tested. 0.1 mol / L solutions of CsCl, SrCl2, LaCl3, and ZrCl4 were used as feed solutions for testing, and the tests were conducted under static diffusion conditions for 3 h. The results showed that the membrane effectively separated CsCl, SrCl2, LaCl3, and ZrCl4. + / Sr 2+ Cs + / La 3+ and Cs + / Zr 4+The selectivity can reach 80, 750 and >1500 respectively, among which Cs + The flux can reach 0.1 mol / (m 2 The result (·h) indicates that the membrane has excellent performance in the selective separation of monovalent / multivalent metal ions.

[0063] Example 2

[0064] Preparation and Ion Separation Performance of A2 / B2 Combined Hydrogen-Bonded Organic Framework Membranes

[0065]

[0066] (1) The polyethersulfone membrane was fixed in the center of the diffusion cell. Tetra(4-aminophenyl)silane (A2) was dissolved in a 3 mol / L aqueous acetic acid solution to prepare an aqueous phase solution with a concentration of 0.5 mmol / L; 2,2'-bipyrimidine-5,5'-dicarboxaldehyde (B2)9 was dissolved in a mixed solvent of ethyl acetate / trimethylbenzene, wherein the volume ratio of ethyl acetate to trimethylbenzene was 2:1, to prepare an organic phase solution with a concentration of 2.0 mmol / L. The prepared aqueous phase solution and organic phase solution were added to both sides of the polyethersulfone membrane, respectively, and the aqueous phase solution and organic phase solution came into contact to form a liquid-liquid interface.

[0067] (2) The reaction was carried out at 80 °C for 100 h. During the reaction, A2 and B2 first underwent a condensation reaction in the confined region of the interface to form discrete oligomeric building units containing imine bonds. The MALDI-TOF mass spectrometry results showed that the molecular weight was 1180, which was consistent with the theoretical structure of the oligomeric building units obtained by the above reaction formula. Subsequently, the oligomeric building units further underwent supramolecular crystallization and lateral linkage on the surface of the support by relying on the hydrogen bonding between unreacted functional groups and the ordered intermolecular stacking, forming a continuous and dense hydrogen-bonded organic framework selective layer.

[0068] (3) After the reaction was completed, the hydrogen-bonded organic framework selective layer was washed with ethyl acetate, ethanol and deionized water in sequence to remove unreacted monomers and surface adsorbed impurities, and then dried under vacuum at 40 °C for 12 h to obtain the A2-B2 type hydrogen-bonded organic framework composite film.

[0069] The resulting composite membrane was characterized. SEM cross-sectional results showed that the thickness of the selected layer was approximately 480 nm, with a clear membrane structure and distinct interfaces. Pore size analysis indicated that the effective pore size of the membrane was approximately 1.06 nm.

[0070] The ion separation performance of the obtained composite membrane was tested. 0.5 mol / L solutions of CsCl, SrCl2, LaCl3, and ZrCl4 were used as feed solutions for testing, and the tests were conducted under static diffusion conditions for 3 h. The results showed that the membrane effectively separated CsCl, SrCl2, LaCl3, and ZrCl4.+ / Sr 2+ Cs + / La 3+ and Cs + / Zr 4+ The selectivity can reach 280, 1750 and >3500 respectively, among which Cs + The flux can reach 0.6 mol / (m 2 The result (·h) indicates that the membrane has excellent performance in the selective separation of monovalent / multivalent metal ions.

[0071] Example 3

[0072] Preparation and Ion Separation Performance of A3 / B3 Combined Hydrogen-Bonded Organic Framework Membranes

[0073]

[0074] (1) The polyethersulfone membrane was fixed in the center of the diffusion cell. Tetra(4-amino-3-hydroxyphenyl)methane (A3) was dissolved in a 6 mol / L aqueous acetic acid solution to prepare an aqueous phase solution with a concentration of 5 mmol / L; 4'-formyl-[1,1'-biphenyl]-4-carboxylic acid (B3) was dissolved in a mixed solvent of ethyl acetate / trimethylbenzene, wherein the volume ratio of ethyl acetate to trimethylbenzene was 3:1, to prepare an organic phase solution with a concentration of 20 mmol / L. The prepared aqueous phase solution and organic phase solution were added to both sides of the polyethersulfone membrane, respectively, and the aqueous phase solution and organic phase solution came into contact to form a liquid-liquid interface.

[0075] (2) The reaction was carried out at 50 °C for 100 h. During the reaction, A3 and B3 first underwent a condensation reaction in the confined region of the interface to form an oligomeric building block containing an imine bond; the MALDI-TOF mass spectrometry results showed that its molecular weight was 1276, which was consistent with the theoretical structure of the oligomeric building block obtained by the above reaction formula. Subsequently, the oligomeric building block further underwent supramolecular crystallization and lateral linkage on the surface of the support by relying on the hydrogen bonding between unreacted functional groups and the ordered intermolecular stacking, forming a continuous and dense hydrogen-bonded organic framework selective layer.

[0076] (3) After the reaction was completed, the hydrogen-bonded organic framework selective layer was washed with ethyl acetate, ethanol and deionized water in sequence to remove unreacted monomers and surface adsorbed impurities, and then dried under vacuum at 40 °C for 12 h to obtain the A3-B3 type hydrogen-bonded organic framework composite film.

[0077] The resulting composite membrane was characterized. SEM cross-sectional results showed that the selected layer thickness was approximately 5 μm, with a clear membrane structure and distinct interfaces. Pore size analysis indicated that the effective pore size of the membrane was approximately 1.12 nm.

[0078] The ion separation performance of the obtained composite membrane was tested. 1 mol / L solutions of CsCl, SrCl2, LaCl3, and ZrCl4 were used as feed solutions for testing, and the tests were conducted for 1000 h under a 1 V driving voltage. The results showed that the membrane effectively separated CsCl, SrCl2, LaCl3, and ZrCl4. + / Sr 2 + Cs + / La 3+ and Cs + / Zr 4+ The selectivity can reach 2400, 17800 and >50000 respectively, among which Cs + The flux can reach 2.1 mol / (m 2 The result (·h) indicates that the membrane has excellent performance in the selective separation of monovalent / multivalent metal ions.

[0079] Example 4

[0080] Preparation and Ion Separation Performance of A4 / B4 Combined Hydrogen-Bonded Organic Framework Membranes

[0081]

[0082] (1) The polyvinylidene fluoride membrane was fixed in the center of the diffusion cell. 2,2',7,7'-tetraamino-9,9'-spirodifluorene (A4) was dissolved in 1 mol / L trifluoroacetic acid aqueous solution to prepare an aqueous solution with a concentration of 0.1 mmol / L; 4-(5-formylpyridin-2-yl)benzoic acid (B4) was dissolved in ethyl acetate to prepare an organic solution with a concentration of 0.4 mmol / L. The prepared aqueous solution and organic solution were added to both sides of the polyvinylidene fluoride membrane, respectively. The aqueous solution and organic solution came into contact to form a liquid-liquid interface.

[0083] (2) The reaction was carried out at 0 °C for 6 h. During the reaction, A4 and B4 first underwent a condensation reaction in the interfacial confinement region to form an oligomeric building block containing imine bonds. The MALDI-TOF mass spectrometry results showed that its molecular weight was 1212, which was consistent with the theoretical structure of the oligomeric building block obtained by the above reaction formula. Subsequently, the oligomeric building block further underwent supramolecular crystallization and lateral linkage on the surface of the support by relying on the hydrogen bonding between unreacted functional groups and the ordered intermolecular stacking, forming a continuous and dense hydrogen-bonded organic framework selective layer.

[0084] (3) After the reaction was completed, the hydrogen-bonded organic framework selective layer was washed with ethyl acetate, ethanol and deionized water in sequence to remove unreacted monomers and surface adsorbed impurities, and then dried under vacuum at 40 °C for 12 h to obtain A4-B4 type hydrogen-bonded organic framework composite film.

[0085] The resulting composite membrane was characterized. SEM cross-sectional results showed that the thickness of the selected layer was approximately 360 nm, with a clear membrane structure and distinct interfaces. Pore size analysis indicated that the effective pore size of the membrane was approximately 1.21 nm.

[0086] The ion separation performance of the obtained composite membrane was tested. 0.25 mol / L solutions of CsCl, SrCl2, LaCl3, and ZrCl4 were used as feed solutions for testing, and the tests were conducted for 1000 h under a 1 V driving voltage. The results showed that the membrane effectively separated CsCl, SrCl2, LaCl3, and ZrCl4. + / Sr 2+ Cs + / La 3+ and Cs + / Zr 4+ The selectivity can reach 480, 11400 and 21000 respectively, of which Cs + The flux can reach 1.1 mol / (m 2 The result (·h) indicates that the membrane has excellent performance in the selective separation of monovalent / multivalent metal ions.

[0087] Example 5

[0088] Preparation and Ion Separation Performance of A5 / B5 Combined Hydrogen-Bonded Organic Framework Membranes

[0089]

[0090] (1) The alumina membrane was fixed in the center of the diffusion cell. 2,2',7,7'-tetraamino-3,3',6,6'-tetramethyl-9,9'-spirodifluorene (A5) was dissolved in 1 mol / L hydrochloric acid aqueous solution to prepare an aqueous solution with a concentration of 0.25 mmol / L; 5-formylpyridinecarboxylic acid (B5) was dissolved in mesitylene to prepare an organic solution with a concentration of 1 mmol / L. The prepared aqueous solution and organic solution were added to both sides of the alumina membrane, respectively, and the aqueous solution and organic solution came into contact to form a liquid-liquid interface.

[0091] (2) The reaction was carried out at 20 °C for 72 h. During the reaction, A5 and B5 first underwent a condensation reaction in the interfacial confinement region to form an oligomeric building unit containing imine bonds. The MALDI-TOF mass spectrometry results showed that its molecular weight was 964, which was consistent with the theoretical structure of the oligomeric building unit obtained by the above reaction formula. Subsequently, the oligomeric building unit further underwent supramolecular crystallization and lateral linkage on the surface of the support by relying on the hydrogen bonding between unreacted functional groups and the ordered intermolecular stacking, forming a continuous and dense hydrogen-bonded organic framework selective layer.

[0092] (3) After the reaction was completed, the hydrogen-bonded organic framework selective layer was washed with ethyl acetate, ethanol and deionized water in sequence to remove unreacted monomers and surface adsorbed impurities, and then dried under vacuum at 40 °C for 12 h to obtain A5-B5 type hydrogen-bonded organic framework composite film.

[0093] The resulting composite membrane was characterized. SEM cross-sectional results showed that the thickness of the selected layer was approximately 569 nm, and the membrane structure was clear with distinct interfaces. Pore size analysis results showed that the effective pore size of the membrane was approximately 0.7 nm.

[0094] The ion separation performance of the obtained composite membrane was tested. 0.25 mol / L solutions of CsCl, SrCl2, LaCl3, and ZrCl4 were used as feed solutions for testing, and the tests were conducted for 400 h under a 0.5 V driving voltage. The results showed that the membrane effectively separated CsCl, SrCl2, LaCl3, and ZrCl4. + / Sr 2+ Cs + / La 3+ and Cs + / Zr 4+ The selectivity can reach 540, 12400 and 28000 respectively, of which Cs + The flux can reach 1.3 mol / (m 2 The result (·h) indicates that the membrane has excellent performance in the selective separation of monovalent / multivalent metal ions.

[0095] Example 6

[0096] Preparation and Ion Separation Performance of A6 / B6 Combined Hydrogen-Bonded Organic Framework Membranes

[0097]

[0098] (1) The polyethersulfone membrane was fixed in the center of the diffusion cell. 1,3,5,7-tetra(4-aminophenyl)adamantane (A6) was dissolved in 0.1 mol / L hydrochloric acid aqueous solution to prepare an aqueous phase solution with a concentration of 1 mmol / L; 5'-formyl-[2,2'-bipyridine]-5-carboxylic acid (B6) was dissolved in a mixed solvent of ethyl acetate / trimethylbenzene, wherein the volume ratio of ethyl acetate to trimethylbenzene was 1:3, to prepare an organic phase solution with a concentration of 4 mmol / L. The prepared aqueous phase solution and organic phase solution were added to both sides of the polyethersulfone membrane, respectively, and the aqueous phase solution and organic phase solution came into contact to form a liquid-liquid interface.

[0099] (2) The reaction was carried out at 80 °C for 100 h. During the reaction, A6 and B6 first underwent a condensation reaction in the interfacial confinement region to form an oligomeric building block containing imine bonds. The MALDI-TOF mass spectrometry results showed that its molecular weight was 1340, which was consistent with the theoretical structure of the oligomeric building block obtained by the above reaction formula. Subsequently, the oligomeric building block further underwent supramolecular crystallization and lateral linkage on the surface of the support by relying on the hydrogen bonding between unreacted functional groups and the ordered intermolecular stacking, forming a continuous and dense hydrogen-bonded organic framework selective layer.

[0100] (3) After the reaction was completed, the hydrogen-bonded organic framework selective layer was washed with ethyl acetate, ethanol and deionized water in sequence to remove unreacted monomers and surface adsorbed impurities. Then it was vacuum dried at 40 °C for 12 h to obtain the A6-B6 type hydrogen-bonded organic framework composite film.

[0101] The resulting composite membrane was characterized. SEM cross-sectional results showed that the thickness of the selected layer was about 820 nm, the membrane structure was clear and the interface was distinct. Pore size analysis results showed that the effective pore size of the membrane was about 2.0 nm.

[0102] The ion separation performance of the obtained composite membrane was tested. The tests were conducted using 1 mol / L solutions of CsCl, SrCl2, LaCl3, and ZrCl4 as feed solutions, respectively, under static diffusion conditions for 1000 h. The results showed that the membrane effectively separated CsCl, SrCl2, LaCl3, and ZrCl4. + / Sr 2+ Cs + / La 3+ and Cs + / Zr 4+ The selectivity can reach 1600, 14300 and >50000 respectively, among which Cs + The flux can reach 0.8 mol / (m 2 The result (·h) indicates that the membrane has excellent performance in the selective separation of monovalent / multivalent metal ions.

[0103] Example 7

[0104] Preparation and Ion Separation Performance of A7 / B7 Combined Hydrogen-Bonded Organic Framework Membranes

[0105]

[0106] (1) The polyacrylonitrile ultrafiltration membrane was fixed in the center of the diffusion cell. Pentaerythritol tetra(4-aminophenyl) ether (A7) was dissolved in 3 mol / L aqueous acetic acid solution to prepare an aqueous phase solution with a concentration of 3 mmol / L; 5'-formyl-[2,2'-bipyrimidine]-5-carboxylic acid (B7) was dissolved in a mixed solvent of ethyl acetate / trimethylbenzene, wherein the volume ratio of ethyl acetate to trimethylbenzene was 5:1, to prepare an organic phase solution with a concentration of 12 mmol / L. The prepared aqueous phase solution and organic phase solution were added to both sides of the polyacrylonitrile ultrafiltration membrane, respectively, so that the aqueous phase solution and organic phase solution came into contact and formed a liquid-liquid interface.

[0107] (2) The reaction was carried out at 35 °C for 72 h. During the reaction, A7 and B7 first underwent a condensation reaction in the interfacial confinement region to form an oligomeric building unit containing imine bonds. The MALDI-TOF mass spectrometry results showed that its molecular weight was 1348, which was consistent with the theoretical structure of the oligomeric building unit obtained by the above reaction formula. Subsequently, the oligomeric building unit further underwent supramolecular crystallization and lateral linkage on the surface of the support by relying on the hydrogen bonding between unreacted functional groups and the ordered intermolecular stacking, forming a continuous and dense hydrogen-bonded organic framework selective layer.

[0108] (3) After the reaction is completed, the hydrogen-bonded organic framework selective layer is washed with ethyl acetate, ethanol and deionized water to remove unreacted monomers and surface adsorbed impurities, and then dried under vacuum at 40 °C for 12 h to obtain A7-B7 type hydrogen-bonded organic framework composite film.

[0109] The obtained composite membrane was characterized. SEM cross-sectional results showed that the thickness of the selected layer was about 520 nm, the membrane structure was clear and the interface was distinct. The pore size analysis results showed that the effective pore size of the membrane was about 1.6 nm.

[0110] The ion separation performance of the obtained composite membrane was tested. 0.5 mol / L solutions of CsCl, SrCl2, LaCl3, and ZrCl4 were used as feed solutions for testing, and the tests were conducted for 1000 h under static diffusion. The results showed that the membrane effectively separated CsCl, SrCl2, LaCl3, and ZrCl4. + / Sr 2+ Cs + / La 3+ and Cs + / Zr 4+ The selectivity can reach 3200, 4300 and 14000 respectively, among which Cs + The flux can reach 0.5 mol / (m 2 The result (·h) indicates that the membrane has excellent performance in the selective separation of monovalent / multivalent metal ions.

[0111] Example 8

[0112] Preparation and Ion Separation Performance of A8 / B8 Combined Hydrogen-Bonded Organic Framework Membranes

[0113]

[0114] (1) The polyacrylonitrile ultrafiltration membrane was fixed in the center of the diffusion cell. 3,3',5,5'-tetra(4-aminophenyl)-2,2',6,6'-tetramethylbiphenyl (A8) was dissolved in 3 mol / L trifluoroacetic acid aqueous solution to prepare an aqueous phase solution with a concentration of 0.25 mmol / L; 2-(5-formylpyridin-2-yl)pyrimidine-5-amine (B8) was dissolved in a mixed solvent of ethyl acetate / trimethylbenzene, wherein the volume ratio of ethyl acetate to trimethylbenzene was 1:1, to prepare an organic phase solution with a concentration of 1 mmol / L. The prepared aqueous phase solution and organic phase solution were added to both sides of the polyacrylonitrile ultrafiltration membrane, respectively, so that the aqueous phase solution and organic phase solution came into contact and formed a liquid-liquid interface.

[0115] (2) The reaction was carried out at 35 °C for 48 h. During the reaction, A8 and B8 first underwent a condensation reaction in the interfacial confinement region to form an oligomeric building block containing imine bonds. The MALDI-TOF mass spectrometry results showed that its molecular weight was 1330, which was consistent with the theoretical structure of the oligomeric building block obtained by the above reaction formula. Subsequently, the oligomeric building block further underwent supramolecular crystallization and lateral linkage on the surface of the support by relying on the hydrogen bonding between unreacted functional groups and the ordered intermolecular stacking, forming a continuous and dense hydrogen-bonded organic framework selective layer.

[0116] (3) After the reaction was completed, the hydrogen-bonded organic framework selective layer was washed with ethyl acetate, ethanol and deionized water in sequence to remove unreacted monomers and surface adsorbed impurities. Then it was vacuum dried at 40 °C for 12 h to obtain the A8-B8 type hydrogen-bonded organic framework composite film.

[0117] The obtained composite membrane was characterized. SEM cross-sectional results showed that the thickness of the selected layer was about 50 nm, the membrane structure was clear and the interface was distinct. Pore size analysis results showed that the effective pore size of the membrane was about 1.7 nm.

[0118] The ion separation performance of the obtained composite membrane was tested. 0.25 mol / L solutions of CsCl, SrCl2, LaCl3, and ZrCl4 were used as feed solutions for testing, and the tests were conducted for 1000 h under static diffusion. The results showed that the membrane effectively separated CsCl, SrCl2, LaCl3, and ZrCl4. + / Sr 2 + Cs + / La 3+ and Cs + / Zr 4+The selectivity can reach 230, 780 and 5400 respectively, of which Cs + The flux can reach 0.23 mol / (m 2 The result (·h) indicates that the membrane has excellent performance in the selective separation of monovalent / multivalent metal ions.

[0119] Example 9

[0120] Preparation and Ion Separation Performance of A9 / B9 Combined Hydrogen-Bonded Organic Framework Membranes

[0121]

[0122] (1) The polyacrylonitrile ultrafiltration membrane was fixed in the center of the diffusion cell. 2,2',6,6'-tetra(4-aminophenyl)-3,3',5,5'-tetramethylbiphenyl (A9) was dissolved in 3 mol / L aqueous acetic acid solution to prepare an aqueous solution with a concentration of 1 mmol / L; 2-(5-hydrazylpyrimidin-2-yl)pyridine-5-carboxaldehyde (B9) was dissolved in a mixed solvent of ethyl acetate / trimethylbenzene, wherein the volume ratio of ethyl acetate to trimethylbenzene was 3:1, to prepare an organic solution with a concentration of 4 mmol / L. The prepared aqueous solution and organic solution were added to both sides of the polyacrylonitrile ultrafiltration membrane, respectively, so that the aqueous solution and organic solution came into contact and formed a liquid-liquid interface.

[0123] (2) The reaction was carried out at 35 °C for 72 h. During the reaction, A9 and B9 first underwent a condensation reaction in the interfacial confinement region to form an oligomeric building unit containing imine bonds; the MALDI-TOF mass spectrometry results showed that its molecular weight was 1362, which was consistent with the theoretical structure of the oligomeric building unit obtained by the above reaction formula. Subsequently, the oligomeric building unit further underwent supramolecular crystallization and lateral linkage on the surface of the support by relying on the hydrogen bonding between unreacted functional groups and the ordered intermolecular stacking, forming a continuous and dense hydrogen-bonded organic framework selective layer.

[0124] (3) After the reaction is completed, the hydrogen-bonded organic framework selective layer is washed with ethyl acetate, ethanol and deionized water in sequence to remove unreacted monomers and surface adsorbed impurities, and then dried under vacuum at 40 °C for 12 h to obtain A9-B9 type hydrogen-bonded organic framework composite film.

[0125] The obtained composite membrane was characterized. SEM cross-sectional results showed that the thickness of the selected layer was about 360 nm, the membrane structure was clear and the interface was distinct. Pore size analysis results showed that the effective pore size of the membrane was about 1.8 nm.

[0126] The ion separation performance of the obtained composite membrane was tested. The tests were conducted using 1 mol / L solutions of CsCl, SrCl2, LaCl3, and ZrCl4 as feed solutions, respectively, under static diffusion conditions for 1000 h. The results showed that the membrane effectively separated CsCl, SrCl2, LaCl3, and ZrCl4. + / Sr 2+ Cs + / La 3+ and Cs + / Zr 4+ The selectivity can reach 578, 3200 and 24500 respectively, of which Cs + The flux can reach 0.98 mol / (m 2 The result (·h) indicates that the membrane has excellent performance in the selective separation of monovalent / multivalent metal ions.

[0127] The MALDI-TOF test results of Examples 1-9 indicate that the formation mechanism of the hydrogen-bonded organic framework membrane belongs to the oligomer-mediated assembly pathway.

[0128] Comparative Example 1

[0129] Anion exchange membrane materials were synthesized according to the method provided in the literature ACS Sustainable Chemistry & Engineering (2023) DOI: 10.1021 / acssuschemeng.3c00891. The ion separation performance was tested according to the experimental procedure and electrolyte concentration in Example 1. The results are as follows: Cs + / Sr 2+ Cs + / La 3+ and Cs + / Zr 4+ The selectivity was 12.5, 79.6, and 305, where Cs + The flux can reach 0.89 mol / (m 2 ·h).

[0130] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a hydrogen-bonded organic framework membrane with tunable pore environment, characterized in that, Includes the following steps: (1) The aqueous phase containing polyamine monomers and the organic phase containing aldehyde linkers are placed on both sides of a porous support substrate. The aqueous phase containing polyamine monomers and the organic phase containing aldehyde linkers are in contact to form a liquid-liquid interface. (2) The polyamine monomer and the aldehyde-containing linker first undergo a confined condensation reaction at the liquid-liquid interface to form discrete oligomeric building units. These discrete oligomeric building units grow laterally and continuously in the interface plane through hydrogen bonding and supramolecular crystallization to form a hydrogen-bonded organic framework selective layer. (3) After the reaction is complete, the hydrogen-bonded organic framework selective layer is washed, dried or solvent-replaced to obtain a hydrogen-bonded organic framework film.

2. The preparation method according to claim 1, characterized in that, Specifically, the following steps are included: (1) Dissolve the polyamine monomer in an acidic aqueous solution to prepare an aqueous solution with a concentration of 0.01 to 5 mmol / L; dissolve the aldehyde linker in an organic solvent to prepare an organic solution with a concentration of 0.04 to 20 mmol / L; An aqueous solution and an organic solution are placed on opposite sides of a porous support substrate, and the aqueous solution and the organic solution are in contact to form a liquid-liquid interface. (2) Under the conditions of 0 to 80 °C, the polyamine monomer and the aldehyde-containing linker first undergo a confined condensation reaction in the interface region formed above, forming discrete oligomeric building units in situ. These building units are interconnected in an ordered manner through hydrogen bonding and supramolecular crystallization, and grow laterally and continuously in the interface plane to form a hydrogen-bonded organic framework selective layer. (3) After the reaction is complete, the hydrogen-bonded organic framework selective layer is washed with organic solvent, lower alcohol and deionized water in sequence, and then dried or solvent replaced to obtain hydrogen-bonded organic framework film.

3. The preparation method according to claim 2, characterized in that, In step (1), the polyamine monomer is selected from polyamine monomers with a tetrahedral configuration, and the aldehyde-containing linker is selected from aromatic dialdehyde linkers or linkers containing one aldehyde group and one hydrogen bond donor; the hydrogen bond donor is a carboxyl group, aldehyde group, hydroxyl group, hydrazine, amide or acylhydrazine.

4. The preparation method according to claim 3, characterized in that, In step (1), the polyamine monomer is selected from one or more of tetra(4-aminophenyl)methane, tetra(4-aminophenyl)silane, tetra(4-amino-3-hydroxyphenyl)methane, 2,2',7,7'-tetraamino-9,9'-spirodifluorene, 2,2',7,7'-tetraamino-3,3',6,6'-tetramethyl-9,9'-spirodifluorene, 1,3,5,7-tetra(4-aminophenyl)adamantane, pentaerythritol tetra(4-aminophenyl) ether, 3,3',5,5'-tetra(4-aminophenyl)-2,2',6,6'-tetramethylbiphenyl, and 2,2',6,6'-tetra(4-aminophenyl)-3,3',5,5'-tetramethylbiphenyl. The aldehyde-containing linker is selected from one or more of 2,2'-bipyridine-5,5'-dicarboxaldehyde, 2,2'-bipyrimidine-5,5'-dicarboxaldehyde, 4'-formyl-[1,1'-biphenyl]-4-carboxylic acid, 4-(5-formylpyridin-2-yl)benzoic acid, 5-formylpyridinecarboxylic acid, 5'-formyl-[2,2'-bipyridine]-5-carboxylic acid, 5'-formyl-[2,2'-bipyrimidine]-5-carboxylic acid, 2-(5-formylpyridin-2-yl)pyrimidine-5-amine, and 2-(5-hydrazylpyrimidine-2-yl)pyridine-5-carboxaldehyde.

5. The preparation method according to claim 3 or 4, characterized in that, The molar ratio of the polyamine monomer to the aldehyde linker is 1:

4.

6. The preparation method according to claim 2, characterized in that, In step (1), the acidic aqueous solution is selected from one or more of the following: acetic acid aqueous solution, trifluoroacetic acid aqueous solution, hydrochloric acid aqueous solution, sulfuric acid aqueous solution, nitric acid aqueous solution, methanesulfonic acid aqueous solution, and p-toluenesulfonic acid aqueous solution; the concentration of the acidic aqueous solution is 0.1–6 M. The organic solvent is selected from one or more of ethyl acetate, mesitylene, toluene, dichloromethane, chloroform, benzene, and o-dichlorobenzene; The porous support substrate is selected from one of polyacrylonitrile membrane, polyethersulfone membrane, polyvinylidene fluoride membrane, and alumina ceramic membrane, with polyacrylonitrile ultrafiltration membrane being preferred.

7. The preparation method according to claim 2, characterized in that, In step (3), the organic solvent is selected from one or more of ethyl acetate, mesitylene, toluene, dichloromethane, chloroform, benzene, and o-dichlorobenzene; the lower alcohol is selected from ethanol, methanol, or a mixture of the two.

8. The preparation method according to claim 2, characterized in that, In step (3), the solvent used in the solvent replacement treatment is a low-boiling-point polar solvent that is miscible with water.

9. A hydrogen-bonded organic framework membrane prepared according to any one of claims 1-8, characterized in that, The hydrogen-bonded organic framework membrane has a continuous, dense, and crystalline ordered selective layer and regular nanochannels, the effective pore size of which is 0.7–2.0 nm and the membrane thickness is 50 nm–5 μm.

10. The application of a hydrogen-bonded organic framework membrane prepared according to any one of claims 1-8 or the hydrogen-bonded organic framework membrane as described in claim 9 in the selective separation of metal ions.

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