Preparation method of hybrid iron-based metal organic framework nanofiltration membrane

Abstract

The application discloses a preparation method of a hybrid iron-based metal organic framework nanofiltration membrane. Multiamine molecules, iron salt compounds and polyphenol compounds are used as raw materials. Iron ion coordination polyphenol polymer nanoparticles are designed and synthesized on the surface of a porous ultrafiltration membrane by regulating the coordination assembly rate of iron ions and polyphenol compounds. The iron ion coordination polyphenol polymer nanoparticles are used as templates for iron-based confined crystallization. By regulating the diffusion rate of iron ions and the coordination between the iron ions and organic ligands, iron-based organic frameworks are induced to grow in a confined crystallization mode on the surface of the nanometer templates. Finally, the hybrid iron-based metal organic framework membrane of an ultrathin and stable polyphenol polymer nanoparticle is obtained through chemical crosslinking. The obtained membrane has high solvent permeability and good separation stability, and has application prospects in the field of biological and medical separation.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation and organic solvent treatment, and specifically relates to a method for preparing a hybrid iron-based metal-organic framework nanofiltration membrane. Background Technology

[0002] With the rapid development of the global healthcare and pharmaceutical industries, higher requirements have been placed on the quality and safety of their products. Solvent-resistant nanofiltration, as a novel membrane separation technology, has the characteristics of high separation efficiency, no phase change, simple operation, and easy integration with industrial processes, making it suitable for biopharmaceutical separation systems. However, biopharmaceutical separation systems are characterized by complex material components, acidic or alkaline solutions, and the presence of organic solvents, which places higher demands on membrane separation performance and structural stability [Chemical Society Reviews, 2022, 51(2): 672-719]. Polymer solvent-resistant nanofiltration membranes have been gradually applied in the above-mentioned fields. However, due to the tendency of polymer molecular chains to entangle and pack tightly, polymer membranes have a dense structure, low permeability, wide pore size distribution, and low separation accuracy. MOFs with high specific surface area and adjustable pore structure can endow separation membranes with higher permeability and separation selectivity, making them ideal membrane materials for efficient separation. However, the brittleness and structural instability of MOF materials themselves limit their use in the large-area preparation of structurally stable MOF separation membranes. To meet the specific needs of substance separation and purification in the biomedical field, higher requirements are placed on the permeation selectivity and structural stability of MOF membranes.

[0003] In recent years, researchers have increasingly used MOF materials in the preparation of separation membranes, and significant progress has been made in the preparation of high-performance MOF membranes. Early MOF membranes were mainly mixed-matrix membranes, whose preparation methods were relatively simple, combining the advantages of easy polymer processability with the tunable pore structure and high porosity of MOF materials. However, MOF membranes prepared by this method are usually thick and prone to interfacial defects, leading to reduced membrane separation selectivity. Recently, researchers have used in-situ growth methods to prepare different types of MOF membranes. However, the crystallization nucleation and growth process of MOFs is difficult to control, and grain boundary defects easily arise, causing a decline in membrane separation performance. Therefore, exploring new controllable preparation methods for MOF membranes to obtain MOF separation membranes with both high permeability selectivity and solvent resistance remains a significant challenge.

[0004] This invention proposes a method for preparing solvent-resistant hybrid iron-based metal-organic framework (MOF) nanofiltration membranes using polyphenol polymer nanoparticles as templates via a nano-confined crystallization approach. Specifically, using polyamine molecules, iron salt compounds, and polyphenolic compounds as raw materials, an iron-ion-coordinated polyphenol polymer nanoparticle template is designed and synthesized on the surface of a porous support membrane by controlling the coordination assembly rate between metal ions and polyphenolic compounds. The coordination interaction between organic ligands and iron ions induces the crystallization and growth of MOFs within the confined space at the template interface. Finally, chemical cross-linking yields an ultrathin and stable polyphenol polymer nanoparticle hybrid iron-based metal-organic framework membrane. This membrane preparation method leverages the strong adhesion properties of polyphenol polymers and their strong coordination with iron ions to enhance the interaction between the separation layer and the porous support layer. Simultaneously, the stability of the MOF crystal structure endows the polyphenol polymer nanoparticle hybrid iron-based metal-organic framework membrane with excellent mechanical strength and solvent resistance. Therefore, the resulting membrane exhibits both high solvent permeability and good separation stability, showing promising applications in the field of biomedical separation. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing a hybrid iron-based metal-organic framework nanofiltration membrane. A method for preparing a hybrid iron-based metal-organic framework nanofiltration membrane includes the following steps:

[0006] 1) The polymer porous ultrafiltration membrane is immersed in an aqueous mixed solution composed of polyamine molecules, iron salt compounds and polyphenolic compounds to form an iron ion coordinated polyphenol polymer nanoparticle template in situ on the surface of the polymer porous support membrane, so as to induce the confined crystallization growth of iron-based metal-organic framework materials at its surface interface.

[0007] 2) The porous support membrane loaded with iron ion-coordinated polyphenol polymer nanoparticles was immersed in an ethanol-water mixed solution of organic ligands and subjected to a nano-confined crystallization reaction to obtain a nascent iron-based metal-organic framework hybrid membrane.

[0008] 3) The above-mentioned nascent iron-based metal-organic framework hybrid membrane was immersed in an organic phase solution of polyacyl chloride for chemical cross-linking, then subjected to thermal curing treatment, and finally washed with deionized water to obtain a polyphenol polymer nanoparticle hybrid iron-based metal-organic framework solvent-resistant nanofiltration membrane.

[0009] Wherein: the polyamine molecule in step 1) is piperazine, N-aminoethylpiperazine, ethylenediamine, m-phenylenediamine, p-phenylenediamine, or 1,3,5-triaminobenzene, and its mass fraction is controlled at 0.1-2.0%; the iron salt compound in step 1) is ferric chloride tetrahydrate, anhydrous ferrous chloride, or ferric chloride hexahydrate, and its mass fraction is controlled at 0.001-0.01%; the polyphenolic compound in step 1) is dopamine, tannic acid, catechol, gallic acid, or catechin, and its mass fraction is controlled at 0.05-0.5%; the organic ligand in step 2) is terephthalic acid or trimellitic acid, and its mass fraction is controlled at 0.001-0.01%; the polyacrylamide chloride monomer in step 3) is phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, or trimellitic chloride. Or biphenyl tetracarboxylate chloride, with a mass fraction controlled at 0.1-1.0%; the porous ultrafiltration membrane in step 1) is polysulfone, polyethersulfone, polyacrylonitrile ultrafiltration membrane, or polyvinylidene fluoride ultrafiltration membrane; the solvent in the aqueous mixed solution in step 1) is water and ethanol, with a water-to-ethanol volume ratio controlled at 5:1-5:4; the impregnation conditions in step 1) are 15-25℃ for 20-120s; the water-to-ethanol volume ratio in the ethanol-water mixed solution in step 2) is controlled at 5:1-5:4; the porous support membrane loaded with iron ion-coordinated polyphenol polymer nanoparticles in step 2) is impregnated in the organic ligand solution under the following conditions: 15-25℃ for 2-50min; the solvent in the organic phase solution in step 3) is n-hexane, cyclohexane, heptane, or Isoparium. Solvent G; the conditions for the chemical crosslinking reaction by impregnation with the organic phase solution in step 3) are 15-25°C for 2-10 min; the conditions for the thermosetting treatment in step 3) are 50-70°C for 10-30 min.

[0010] The polyphenol polymer nanoparticle hybrid iron-based metal-organic framework membrane prepared by this method can be used for the separation and purification of biopharmaceutical molecules and nanofiltration of organic solvents.

[0011] The separation performance testing method for the product of this invention is as follows: The hybrid membrane is placed in a conventional pressure-driven flat sheet membrane testing device in the art. Before testing, the membrane is pre-pressed at an operating pressure of 0.3 MPa for 1 hour. Then, under test conditions of 25°C and 0.2 MPa, the permeate flux (J) and the substance rejection rate (R) of the membrane are measured. The calculation formulas are: J = V / (At); R = 1 - C p / C f Where V represents the volume of feed liquid permeating through the membrane, and A represents the effective area of ​​the membrane, which is 22.4 cm². 2 t – runtime, C p - Osmotic concentration, C f - Feed concentration; the concentration of organic matter in the solution is obtained by measuring the ultraviolet absorbance of the solution.

[0012] The polyphenol polymer nanoparticle hybrid iron-based metal-organic framework (MOF) membrane is constructed by in-situ forming metal ion-coordinated polyphenol polymer nanoparticles on the surface of a polymer porous support membrane. Using these nanoparticles as templates, the nucleation, crystallization, and growth processes of MOFs are controlled through confined crystallization. The microstructure and separation performance of the membrane can be optimized by changing the concentrations of iron ions and organic ligands, as well as the confined crystallization time. Due to the strong coordination between iron ions and polyphenolic compounds, and the inherent crystal structure stability of the high-valence metal ion carboxylate framework, the resulting polyphenol polymer nanoparticle hybrid iron-based MOF membrane exhibits excellent solvent resistance. While maintaining high retention efficiency (>96%) of protoporphyrin fluorescent molecules, the membrane also exhibits ethanol permeability as high as ~60.0 L / m³. -2 h -1 bar -1 Furthermore, this method is simple and easy to control, and has good prospects for industrial application in the purification and concentration of biopharmaceutical molecules. Detailed Implementation

[0013] Example 1:

[0014] A polysulfone ultrafiltration membrane was prepared in an ethanol-water mixture (V) containing piperazine (0.1 wt%), tannic acid (0.05 wt%), and ferric chloride hexahydrate (0.001 wt%). 水 :V 乙醇 Immerse the membrane in a solution of Fe (5:1) at 15°C for 20 seconds, remove it, and remove any residual liquid from the membrane surface to obtain a solution composed of Fe. 3+ A polymer film assembled from coordinated polyphenol polymer nanoparticles; using the above polymer film as a template, then using a 0.001% (w / w) pyromellitic acid ethanol-water mixed solution (V 水 :V 乙醇 =5:1) Immersed at 15℃ for 2 min, through Fe 3+ Coordination of polyphenol polymer nanoparticles controls the diffusion rate of iron ions and their coordination with trimesic acid, resulting in the confined crystal growth of FeBTC MOF at the nanoparticle interface, thus obtaining a nascent iron-based metal-organic framework hybrid membrane. The nascent iron-based metal-organic framework hybrid membrane is then chemically crosslinked in a 0.1% trimesicoyl chloride-hexane solution at 15°C for 1 min to remove excess organic solvent. Finally, it is cured at 50°C for 10 min and washed with deionized water to obtain a polyphenol polymer nanoparticle hybrid iron-based metal-organic framework solvent-resistant nanofiltration membrane.

[0015] The above-mentioned polyphenol polymer nanoparticle hybrid iron-based metal-organic framework solvent-resistant nanofiltration membrane was tested for organic solvent nanofiltration at 25°C and 0.1 MPa pressure. For 0.05 g / L... -1The isolation results of protoporphyrin were as follows: ethanol permeability was 15 L m. -2 h - 1 bar -1 The protoporphyrin rejection rate was 70.2%.

[0016] Example 2:

[0017] A polysulfone ultrafiltration membrane was prepared in an ethanol-water mixture (V) containing piperazine (2.0 wt%), tannic acid (0.5 wt%), and ferric chloride hexahydrate (0.01 wt%). 水 :V 乙醇 Immerse the membrane in a solution of Fe (5:4) at 25°C for 120 seconds, remove the membrane and remove any residual liquid from the surface, to obtain a membrane composed of Fe. 3+ A polymer film assembled from coordinated polyphenol polymer nanoparticles; using the above polymer film as a template, then using a 0.01% (w / w) pyromellitic acid ethanol-water mixed solution (V 水 :V 乙醇 =5:4) Immersed at 25℃ for 50 min, through Fe 3+ Coordination of polyphenol polymer nanoparticles controls the diffusion rate of iron ions and their coordination with trimesic acid, resulting in the confined crystal growth of FeBTC MOF at the nanoparticle interface, thus obtaining a nascent iron-based metal-organic framework hybrid membrane. The nascent iron-based metal-organic framework hybrid membrane is then chemically crosslinked in a 1.0% (w / w) trimesicoyl chloride-hexane solution at 25°C for 10 min to remove excess organic solvent. Finally, it is cured at 70°C for 30 min and washed with deionized water to obtain a polyphenol polymer nanoparticle hybrid iron-based metal-organic framework solvent-resistant nanofiltration membrane.

[0018] The above-mentioned polyphenol polymer nanoparticle hybrid iron-based metal-organic framework solvent-resistant nanofiltration membrane was tested for organic solvent nanofiltration at 25°C and 0.1 MPa pressure. For 0.05 g L... -1 The isolation results of protoporphyrin were as follows: ethanol permeability was 15.0 L / m³. - 2 h -1 bar -1 The protoporphyrin rejection rate was 99.5%.

[0019] Example 3:

[0020] A polysulfone ultrafiltration membrane was prepared in an ethanol-water mixture (V) containing piperazine (0.2 wt%), tannic acid (0.2 wt%), and ferric chloride hexahydrate (0.002 wt%). 水 :V 乙醇 Immerse the membrane in a solution of Fe (5:2) at 25°C for 60 seconds, remove it, and remove any residual liquid from the membrane surface to obtain a solution composed of Fe. 3+A polymer film assembled from coordinated polyphenol polymer nanoparticles; using the above polymer film as a template, then using a 0.002% (w / w) pyromellitic acid ethanol-water mixed solution (V 水 :V 乙醇 =5:2) Immersed at 25℃ for 30 min, through Fe 3+ Coordination of polyphenol polymer nanoparticles controls the diffusion rate of iron ions and their coordination with trimesic acid, resulting in the confined crystal growth of FeBTC MOF at the nanoparticle interface, thus obtaining a nascent iron-based metal-organic framework hybrid membrane. The nascent iron-based metal-organic framework hybrid membrane is then chemically crosslinked in a 0.2% trimesicoyl chloride-hexane solution at 25°C for 5 min to remove excess organic solvent. Finally, it is cured at 60°C for 15 min and washed with deionized water to obtain a polyphenol polymer nanoparticle hybrid iron-based metal-organic framework solvent-resistant nanofiltration membrane.

[0021] Comparative Example 1

[0022] Referring to the steps in Example 3, without adding ferric chloride hexahydrate and tannic acid to the aqueous solution, polyamide films were prepared directly from piperazine and trimesoyl chloride as raw materials (preparation conditions refer to Example 3) through interfacial polymerization.

[0023] Comparative Example 2

[0024] Referring to the steps in Example 3, without adding ferric chloride hexahydrate to the aqueous solution, organic nanoparticles were directly formed by oxidative polymerization of piperazine and tannic acid (preparation conditions refer to Example 3), and then cross-linked with trimesoyl chloride to prepare a polyphenol polymer nanomembrane.

[0025] Comparative Example 3

[0026] Referring to the steps in Example 3, Fe was obtained. 3+ Iron ion coordinated polyphenol nanoparticles were assembled into membranes by directly chemically crosslinking them with trimesoyl chloride (preparation conditions refer to Example 3) to prepare iron ion coordinated polyphenol polymer nanomembranes.

[0027] Table 1. Comparison of separation performance of polyamide membranes prepared in Examples 1-3 (Example 3)

[0028]

[0029] The results in Table 1 show that all four methods can prepare solvent-resistant nanofiltration membranes, but there are significant differences in their ethanol flux and protoporphyrin rejection rate. This is due to the different chemical composition and microstructure of the prepared solvent-resistant nanofiltration membranes.

[0030] In Comparative Example 1, the polyamide membrane prepared by interfacial polymerization of polyamines and polyacrylamide chlorides is composed of cross-linked flexible polyamide polymer chains. The membrane has discontinuous sub-nanopores, resulting in a dense structure and high mass transfer resistance. Furthermore, the polyamide polymer chains are prone to swelling and deformation in organic solvents, leading to low ethanol permeability and low rejection rate of organic molecules. In Comparative Example 2, a polyphenol polymer nano-based solvent-resistant nanofiltration membrane was prepared using polyamines, tannic acid, and polyacrylamide chlorides as membrane-forming materials. This membrane is composed of polymer nanoparticles and has a certain sub-nanopore structure. The ethanol flux is improved compared to the pure polyamide membrane, but the polymer nano-based membrane lacks continuous nanochannels, making it difficult to significantly improve the membrane solvent permeability. In Comparative Example 3, the solvent-resistant nanofiltration membrane assembled from iron-ion coordinated polyphenol polymer nanoparticles has similar separation performance to the solvent-resistant nanofiltration membrane in Comparative Example 2, with no significant improvement in ethanol permeation flux and protoporphyrin rejection rate.

[0031] The polyphenol polymer nanoparticle hybrid iron-based metal-organic framework membrane obtained in Example 3 exhibits confined crystallization of FeBTC at the interface of iron-coordinated polyphenol polymer nanoparticles, forming a continuous nanochannel structure within the membrane. Furthermore, the rigid FeBTC MOF crystals suppress polymer chain deformation, enhancing the stiffness of the nanochannels and imparting better solvent resistance to the polyphenol polymer nanoparticle hybrid iron-based metal-organic framework membrane. Therefore, the polyphenol polymer nanoparticle hybrid iron-based metal-organic framework membrane combines ultra-high ethanol permeability with excellent organic molecule retention performance.

[0032] Example 4:

[0033] A polysulfone ultrafiltration membrane was prepared in an ethanol-water mixture (V) containing N-aminoethylpiperazine (0.2 wt%), dopamine (0.2 wt%), and anhydrous ferric chloride (0.002 wt%). 水 :V 乙醇 Immerse the membrane in a solution of Fe (5:2) at 25°C for 60 seconds, remove it, and remove any residual liquid from the membrane surface to obtain a solution composed of Fe. 3+ A polymer film assembled from coordinated polyphenol polymer nanoparticles; using the above polymer film as a template, then using a 0.002% (w / w) pyromellitic acid ethanol-water mixed solution (V 水 :V 乙醇 =5:2) Immersed at 25℃ for 30 min, through Fe 3+By controlling the diffusion rate of iron ions and their coordination with trimesic acid in coordinated polyphenol polymer nanoparticles, FeBTC MOF was grown in a confined crystallization manner at the nanoparticle interface, resulting in a nascent iron-based metal-organic framework hybrid membrane. The nascent iron-based metal-organic framework hybrid membrane was chemically crosslinked in a 0.2% trimesicoyl chloride n-hexane solution at 25°C for 5 min to remove excess organic solvent. Finally, it was cured at 60°C for 15 min and washed with deionized water to obtain a polyphenol polymer nanoparticle hybrid iron-based metal-organic framework solvent-resistant nanofiltration membrane.

[0034] The above-mentioned polyphenol polymer nanoparticle hybrid iron-based metal-organic framework solvent-resistant nanofiltration membrane was tested for organic solvent nanofiltration at 25°C and 0.1 MPa pressure. For 0.05 g L... -1 The isolation results of protoporphyrin were as follows: ethanol permeability was 55.0 L / m³. - 2 h -1 bar -1 The protoporphyrin rejection rate was 99.5%.

[0035] Example 5:

[0036] A polyacrylonitrile ultrafiltration membrane was used to prepare an ethanol-water mixed solution (V) containing m-phenylenediamine (0.2 wt%), gallic acid (0.2 wt%), and ferric chloride tetrahydrate (0.002 wt%). 水 :V 乙醇 Immerse the membrane in a solution of Fe (5:2) at 25°C for 60 seconds, remove it, and remove any residual liquid from the membrane surface to obtain a solution composed of Fe. 3+ A polymer film assembled from coordinated polyphenol polymer nanoparticles; using the above polymer film as a template, then using a 0.002% (w / w) pyromellitic acid ethanol-water mixed solution (V 水 :V 乙醇 =5:2) Immersed at 25℃ for 30 min, through Fe 3+ Coordination of polyphenol polymer nanoparticles controls the diffusion rate of iron ions and their coordination with trimesic acid, resulting in the confined crystal growth of FeBTC MOF at the nanoparticle interface, thus obtaining a nascent iron-based metal-organic framework hybrid membrane. The nascent iron-based metal-organic framework hybrid membrane is then chemically crosslinked in a 0.2% (w / w) terephthaloyl chloride-hexane solution at 25°C for 5 min to remove excess organic solvent. Finally, it is cured at 60°C for 15 min and washed with deionized water to obtain a polyphenol polymer nanoparticle hybrid iron-based metal-organic framework solvent-resistant nanofiltration membrane.

[0037] The above-mentioned polyphenol polymer nanoparticle hybrid iron-based metal-organic framework solvent-resistant nanofiltration membrane was tested for organic solvent nanofiltration at 25°C and 0.1 MPa pressure. For 0.05 g L... -1The isolation results of protoporphyrin were as follows: ethanol permeability was 50.0 L / m³. - 2 h -1 bar -1 The protoporphyrin rejection rate was 95%.

[0038] Example 6:

[0039] A polyethersulfone ultrafiltration membrane was prepared in an ethanol-water mixture (V) containing ethylenediamine (0.2 wt%), catechin (0.2 wt%), and anhydrous ferrous chloride (0.002 wt%). 水 :V 乙醇 Immerse the membrane in a solution of Fe (5:2) at 25°C for 60 seconds, remove it, and remove any residual liquid from the membrane surface to obtain a solution composed of Fe. 3+ A polymer film assembled from coordinated polyphenol polymer nanoparticles; using the above polymer film as a template, then using a 0.002% (w / w) pyromellitic acid ethanol-water mixed solution (V 水 :V 乙醇 =5:2) Immersed at 25℃ for 30 min, through Fe 3+ Coordination of polyphenol polymer nanoparticles controls the diffusion rate of iron ions and their coordination with trimesic acid, resulting in the confined crystal growth of FeBTC MOF at the nanoparticle interface, thus obtaining a nascent iron-based metal-organic framework hybrid membrane. The nascent iron-based metal-organic framework hybrid membrane is then chemically crosslinked in a 0.2% (w / w) phthaloyl chloride-hexane solution at 25°C for 5 min to remove excess organic solvent. Finally, it is cured at 60°C for 15 min and washed with deionized water to obtain a polyphenol polymer nanoparticle hybrid iron-based metal-organic framework solvent-resistant nanofiltration membrane.

[0040] The above-mentioned polyphenol polymer nanoparticle hybrid iron-based metal-organic framework solvent-resistant nanofiltration membrane was tested for organic solvent nanofiltration at 25°C and 0.1 MPa pressure. For 0.05 g L... -1 The isolation results of protoporphyrin were as follows: ethanol permeability was 18.0 L / m³. - 2 h -1 bar -1 The protoporphyrin rejection rate was 85%.

Claims

1. A method for preparing a hybrid iron-based metal-organic framework nanofiltration membrane, characterized in that... The steps include the following: 1) The polymer porous ultrafiltration membrane is immersed in an aqueous mixed solution composed of polyamine molecules, iron salt compounds and polyphenolic compounds to form an iron ion coordinated polyphenol polymer nanoparticle template in situ on the surface of the polymer porous support membrane, thereby obtaining a porous support membrane loaded with iron ion coordinated polyphenol polymer nanoparticles to induce confined crystal growth of iron-based metal-organic framework materials at its surface interface. 2) The porous support membrane loaded with iron ion-coordinated polyphenol polymer nanoparticles was immersed in an ethanol-water mixed solution of organic ligands and subjected to a nano-confined crystallization reaction to obtain a nascent iron-based metal-organic framework hybrid membrane. 3) The above-mentioned nascent iron-based metal-organic framework hybrid membrane was immersed in an organic phase solution of polyacrylamide chloride for chemical cross-linking, then subjected to thermal curing treatment, and finally washed with deionized water to obtain a polyphenol polymer nanoparticle hybrid iron-based metal-organic framework solvent-resistant nanofiltration membrane. Wherein: the polyamine molecule in step 1) is piperazine, N-aminoethylpiperazine, ethylenediamine, m-phenylenediamine, p-phenylenediamine, or 1,3,5-triaminobenzene, and its mass fraction is controlled between 0.1% and 2.0%; the iron salt compound in step 1) is ferric chloride tetrahydrate, anhydrous ferrous chloride, or ferric chloride hexahydrate, and its mass fraction is controlled between 0.001% and 0.01%. The percentage of polyphenolic compounds in step 1) is 0.05-0.5%, including dopamine, tannic acid, catechol, gallic acid, or catechin; the percentage of organic ligands in step 2) is terephthalic acid or trimellitic acid, with a percentage of 0.001-0.01%; the percentage of polyacrylamide chloride monomers in step 3) is phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, trimellitic chloride, or biphenyltetramethyl chloride, with a percentage of 0.1-1.0%; the percentage of porous ultrafiltration membrane in step 1) is polysulfone, polyethersulfone, polyacrylonitrile ultrafiltration membrane, or polyvinylidene fluoride ultrafiltration membrane; the solvent in the aqueous mixed solution in step 1) is water and ethanol, with a volume ratio of water to ethanol controlled at 5:1-5:4; the impregnation conditions in step 1) are 20-120 °C at 15-25 °C. s; In step 2), the volume ratio of water to ethanol in the ethanol-water mixed solution is controlled at 5:1 to 5:4; In step 2), the porous support membrane loaded with iron ion-coordinated polyphenol polymer nanoparticles is immersed in the organic ligand solution under the following conditions: immersion at 15–25°C for 2–50 min; In step 3), the solvent of the organic phase solution is n-hexane, cyclohexane, heptane, or Isopar G solvent; In step 3), the conditions for the chemical crosslinking reaction of the organic phase solution immersion are 15–25°C for 2–10 min; In step 3), the conditions for the thermosetting treatment are 50–70°C for 10–30 min.

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