Preparation method of interface confinement cross-linked fluorinated covalent organic framework solvent-resistant nanofiltration membrane

Abstract

The invention discloses a preparation method of an interface confinement cross-linked fluorinated covalent organic framework solvent-resistant nanofiltration membrane, which comprises the following steps: by taking an aromatic amine monomer and a fluorinated aldehyde monomer as reaction raw materials, carrying out interfacial polymerization reaction to obtain fluorinated covalent organic framework nanoparticles; the nano particles are used as a main membrane forming material, and the fluorinated covalent organic framework nano element membrane is formed on the surface of a porous support membrane through self-assembly by pressure filtration; and preparing the solvent-resistant nanofiltration membrane through an interface confinement cross-linking method. According to the invention, the membrane preparation process is obviously simplified, the energy consumption is reduced, the preparation efficiency and the amplification performance are improved, and an efficient membrane separation technology with an application prospect is provided for efficient separation of substances in an organic solvent system and effective recovery of organic solvent resources.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation, and particularly relates to a method for preparing an interface-confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane. Background Technology

[0002] In modern industrial production, organic solvents are widely used in numerous fields such as chemical engineering, pharmaceuticals, fine chemicals, petrochemicals, paints and coatings, printing, and textiles. It is estimated that over 3,000 different organic solvents are currently in widespread use. However, traditional separation technologies (such as distillation, rectification, and solvent extraction) generally suffer from problems such as complex processes, high energy consumption, low efficiency, and the use of large amounts of volatile organic solvents, making it difficult to meet the demands of modern green and efficient production. Compared to these traditional solvent treatment technologies, organic solvent nanofiltration (OSN) technology, as an emerging organic solvent treatment technology, has attracted widespread attention due to its advantages such as low energy consumption, no phase change or chemical reaction during separation, and high separation efficiency. As the core of OSN membrane separation technology, the permeation selectivity of the membrane determines the separation efficiency of the OSN process. Although traditional polymer OSN membranes can be used for the separation of organic solvent systems, they are typically composed of tightly packed amorphous polymer chains, resulting in generally low solvent permeation flux, low separation precision, and poor solvent resistance.

[0003] Covalent organic framework (COF) materials offer new opportunities for constructing high-flux OSN membranes due to their highly ordered nanopores, high specific surface area, and excellent chemical stability. Theoretically, COF membranes can provide solvent permeation flux far exceeding that of traditional polymer membranes. However, existing COF membranes face two major bottlenecks when used for the separation of small organic molecules in solvents: First, their inherent pore size (generally >2 nm) cannot effectively separate organic molecules with molecular weights less than 1000 Da based on size sieving mechanisms; second, currently reported high-performance COF membrane preparation methods (such as in-situ growth, LB layer-by-layer stacking, and electrochemical synthesis) generally suffer from drawbacks such as cumbersome synthesis steps, harsh conditions (usually requiring long-term reactions under high temperature and vacuum conditions), long cycles, poor reproducibility, and difficulty in large-scale scaling, which seriously hinder their practical application (J.Am.Chem.Soc.2011,133,19816-19822,Angew. ChemInt. Ed. 2025.64.e202422333). Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing an interface-confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane.

[0005] The overall concept of this invention is to use aromatic amine monomers and fluorinated aldehyde monomers as reactants to obtain fluorinated covalent organic framework nanoparticles through interfacial polymerization. Using these nanoparticles as the main film-forming material, a fluorinated covalent organic framework nano-unit membrane is formed by self-assembly on the surface of a porous support membrane through pressure filtration. Then, a solvent-resistant nanofiltration membrane is prepared using an interfacial confined crosslinking method. During the above film-forming process, polyamine monomer molecules and crosslinking agents undergo interfacial confined crosslinking reactions within the confined space formed by the fluorinated covalent organic framework nano-units. The resulting polymer molecular chains can effectively control the membrane pore size and simultaneously generate strong covalent bonds between the nano-units, improving the membrane's solvent resistance stability. This film-forming method not only significantly simplifies the membrane preparation process, reduces energy consumption, and improves preparation efficiency and scalability, but also successfully prepares a solvent-resistant nanofiltration membrane with high permeability and high separation selectivity through the synergy of "fine pore size control" and "high-speed transport channels." This provides a promising high-efficiency membrane separation technology for the efficient separation of substances in organic solvent systems and the effective recovery of organic solvent resources.

[0006] Based on the above ideas, the technical solution adopted by the present invention is as follows: a method for preparing an interface-confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane, characterized by comprising the following steps: 1) Dissolve 0.05~0.3 parts by mass of aromatic amine monomer in 100 parts by mass of aqueous solution containing catalyst to prepare an aqueous solution, and dissolve 0.02~0.1 parts by mass of fluorinated aromatic aldehyde monomer in 100 parts by mass of organic solvent to prepare an organic solution. Pour the above organic solution into the aqueous solution and carry out interfacial polymerization reaction to obtain fluorinated covalent organic framework nanoparticles. 2) The above-mentioned fluorinated covalent organic framework nanoparticles were prepared into a dilute dispersion, and after ultrasonic treatment, they were filtered under pressure to form a fluorinated covalent organic framework nanoparticle membrane on the surface of a porous support membrane. 3) Dissolve 0.05-0.3 parts by mass of polyamine monomer molecules in 100 parts by mass of alkaline aqueous solution to prepare a polyamine aqueous solution; dissolve 0.1-0.3 parts by mass of crosslinking agent molecules in 100 parts by mass of organic solvent to prepare a crosslinking agent solution; then immerse the polyamine aqueous solution on the surface of the fluorinated covalent organic framework nanomembrane obtained in step 2), remove excess polyamine aqueous solution to form a fluorinated covalent organic framework nanomembrane loaded with polyamine monomers; then pour the crosslinking agent solution onto the surface of the above nanomembrane, and carry out an interface-confined crosslinking reaction at 20-30℃ for 1-20 min, remove excess crosslinking agent solution, and finally dry to obtain an interface-confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane.

[0007] The aromatic amine monomer molecule mentioned in step 1) above is selected from p-phenylenediamine, melamine, tetra(4-aminophenyl)methane, or 1,3,5-tris(4-aminophenyl)benzene; the catalyst mentioned in step 1) is selected from acetic acid, p-toluenesulfonic acid, formic acid, trifluoroacetic acid, or polyphosphoric acid; the fluorinated aromatic aldehyde monomer molecule mentioned in step 1) is selected from 2-fluorobenzaldehyde, 2,4-difluorobenzaldehyde, p-fluorobenzaldehyde, p-trifluoromethylbenzaldehyde, or 2,3,5,6-tetrafluorop-diphenylaldehyde; the organic phase solvent mentioned in step 1) is one or more mixed solvents selected from n-hexane, dimethyl sulfoxide, cyclohexane, or isoparaffinic hydrocarbons IsoparG; in step 2) The porous support membrane is selected from cellulose triacetate microfiltration membrane, nylon microfiltration membrane, polyvinylidene fluoride microfiltration membrane, or polytetrafluoroethylene microfiltration membrane; the polyamine monomer molecule in step 3) is selected from ethylenediamine, diethylenetriamine, cyclohexanediamine, m-phenylenediamine, or piperazine; the alkali in the alkaline aqueous solution in step 3) is selected from sodium hydroxide, sodium bicarbonate, sodium phosphate, sodium carbonate, or triethylamine; the crosslinking agent molecule in step 3) is selected from trimesoyl chloride, terephthaloyl chloride, toluene diisocyanate, or N-hydroxysuccinimide ester; the organic phase solvent in step 3) is one or more of cyclohexane, n-heptane, n-hexane, or Isopar G.

[0008] The mass percentage concentration of the catalyst in the aqueous catalyst solution described in step 1) is 0.5-5%; the interfacial polymerization reaction conditions described in step 1) are 60-80℃ for 12-72 h; the mass percentage concentration of the fluorinated covalent organic framework nanoparticles in the dilute dispersion described in step 2) is 0.01-0.05%; the ultrasonic treatment conditions described in step 2) are 20-40℃ for 20-40 kHz for 10-30 min; the pressure filtration conditions described in step 2) are filtration at 20-30℃ under 0.1-0.3 MPa pressure; the mass percentage concentration of the alkaline aqueous solution described in step 3) is 10-40%; the impregnation time of the polyamine aqueous solution described in step 3) is 10-30 min; and the drying treatment conditions described in step 3) are drying at 50-80℃ for 5-20 min.

[0009] The aforementioned interface-confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane can be used for the separation of antibiotics of different molecular weights.

[0010] The separation performance testing method of the solvent-resistant nanofiltration membrane of the interfacial confined crosslinked fluorinated covalent organic framework of the present invention is as follows: The composite membrane is placed in a conventional testing device in the art. Before testing, the membrane is pre-pressurized at an operating pressure of 0.3 MPa for 1 h. Then, under the test conditions of 25°C and 0.2 MPa, the methanol permeate flux (J) and tetracycline rejection rate (R) of the membrane are measured. The calculation formulas are: J=ΔV / (A·ΔP·Δt); R=1-C p / C f Where ΔV is the volume of feed liquid permeating through the membrane, and A is the effective area of ​​the membrane (19.625 cm²). 2 Δt - running time, C p -Opermeate concentration, C f - Feed solution concentration; The absorbance of the solution is measured by ultraviolet spectroscopy, and the concentration of the antibiotic solution can be obtained according to the measured absorbance-concentration standard curve.

[0011] This invention uses aromatic amine monomers and fluorinated aldehyde monomers as reactants to obtain fluorinated covalent organic framework nanoparticles through interfacial polymerization. Using these nanoparticles as the main film-forming material, a fluorinated covalent organic framework nano-unit membrane is formed by self-assembly on the surface of a porous support membrane through pressure filtration. A solvent-resistant nanofiltration membrane is then prepared using an interfacial confined crosslinking method. During the film-forming process, the polyamine monomer molecules and crosslinking agents undergo interfacial confined crosslinking reactions within the confined space formed by the fluorinated covalent organic framework nano-units. The resulting polymer molecular chains effectively control the membrane pore size and simultaneously generate strong covalent bonds between the nano-units, improving the membrane's solvent resistance. The solvent-resistant nanofiltration membrane preparation method of this invention not only significantly simplifies the membrane preparation process, reduces energy consumption, and improves preparation efficiency and scalability, but also successfully prepares a solvent-resistant nanofiltration membrane with high permeability and high separation selectivity through the synergy of "fine pore size control" and "high-speed transport channels." The methanol permeation flux of this solvent-resistant nanofiltration membrane is higher than 15 L·m⁻¹. -2 ·h -1 ·bar -1 It has a retention rate of over 95% for antibiotic molecules with a molecular weight greater than 500 Da, providing a promising high-efficiency membrane separation technology for the efficient separation of substances in organic solvent systems and the effective recovery of organic solvent resources. Detailed Implementation

[0012] The following are embodiments of the present invention, but the present invention is not limited to the embodiments.

[0013] Example 1: 0.05 g of 1,3,5-tris(4-aminophenyl)benzene was dissolved in 100 g of an aqueous solution containing 0.5 wt% acetic acid to prepare an aqueous phase solution. 0.02 g of 2,3,5,6-tetrafluoro-p-dibenzaldehyde was dissolved in 100 g of n-hexane to prepare an organic phase solution. The organic phase solution was then added to the aqueous phase solution, and interfacial polymerization was carried out at 60 °C for 12 h to obtain fluorinated covalent organic framework nanoparticles. A 0.01 wt% dispersion of the fluorinated covalent organic framework nanoparticles was prepared, ultrasonically treated at 20 °C and 20 kHz for 10 min, and then pressure filtered at 0.1 MPa and 20 °C to self-assemble on the surface of a nylon microfiltration membrane to form a fluorinated covalent organic framework nanomembrane. 0.05 g of piperazine was dissolved in 100 g of 10 wt% sodium hydroxide aqueous solution to prepare a piperazine aqueous solution. 0.1 g of pyromellitic methyl chloride was dissolved in 100 g of IsoparG organic solvent to prepare a crosslinking agent solution. The piperazine aqueous solution was then immersed on the surface of a fluorinated covalent organic framework nanomembrane for 10 min. After removing excess piperazine aqueous solution, a fluorinated covalent organic framework nanomembrane loaded with piperazine monomer was formed. A pyromellitic methyl chloride IsoparG solution was then poured onto the surface of the above nanomembrane, and an interfacial confined crosslinking reaction was carried out at 20 °C for 1 min. After removing excess pyromellitic methyl chloride IsoparG solution, the membrane was dried at 50 °C for 5 min to obtain an interfacial confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane.

[0014] Solvent-resistant nanofiltration membranes with interfacial confined crosslinking fluorinated covalent organic frameworks, used at 25°C and 0.2 MPa pressure, for 0.05 g·L⁻¹ -1 The filtration separation efficiency of doxorubicin hydrochloride and tetracycline methanol solution was as follows: methanol permeation flux was 15.1 L·m⁻¹. -2 ·h -1 ·bar -1 The retention rates for doxorubicin hydrochloride and tetracycline were 99.1% and 98.5%, respectively.

[0015] Example 2: 0.3 g of 1,3,5-tris(4-aminophenyl)benzene was dissolved in 100 g of an aqueous solution containing 5 wt% acetic acid to prepare an aqueous phase solution. 0.1 g of 2,3,5,6-tetrafluoro-p-dibenzaldehyde was dissolved in 100 g of n-hexane to prepare an organic phase solution. The organic phase solution was then added to the aqueous phase solution, and interfacial polymerization was carried out at 80 °C for 72 h to obtain fluorinated covalent organic framework nanoparticles. A 0.05 wt% dispersion of the fluorinated covalent organic framework nanoparticles was prepared, ultrasonically treated at 40 °C and 40 kHz for 30 min, and then pressure filtered at 0.3 MPa and 30 °C to self-assemble on the surface of a nylon microfiltration membrane to form a fluorinated covalent organic framework nanomembrane. 0.3 g of piperazine was dissolved in 100 g of 40 wt% sodium hydroxide aqueous solution to prepare a piperazine aqueous solution. 0.3 g of pyromellitic methyl methacrylate (PMC) chloride was dissolved in 100 g of IsoparG organic solvent to prepare a crosslinking agent solution. The piperazine aqueous solution was then immersed on the surface of a fluorinated covalent organic framework nanomembrane for 30 min. After removing excess piperazine aqueous solution, a fluorinated covalent organic framework nanomembrane loaded with piperazine monomer was formed. PMC chloride IsoparG solution was then poured onto the surface of the above nanomembrane, and an interfacial confined crosslinking reaction was carried out at 30 °C for 20 min. After removing excess PMC chloride IsoparG solution, the membrane was dried at 80 °C for 20 min to obtain an interfacial confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane.

[0016] Solvent-resistant nanofiltration membranes with interfacial confined crosslinking fluorinated covalent organic frameworks, used at 25°C and 0.2 MPa pressure, for 0.05 g·L⁻¹ -1 The filtration separation efficiency of doxorubicin hydrochloride and tetracycline methanol solution was as follows: methanol permeation flux was 15.7 L·m⁻¹. -2 ·h -1 ·bar -1 The retention rates for doxorubicin hydrochloride and tetracycline were 99.2% and 98.1%, respectively.

[0017] Example 3: 0.036 g of 1,3,5-tris(4-aminophenyl)benzene was dissolved in 100 g of an aqueous solution containing 0.5 wt% acetic acid to prepare an aqueous phase solution. 0.0315 g of 2,3,5,6-tetrafluoro-p-dibenzaldehyde was dissolved in 100 g of n-hexane to prepare an organic phase solution. The organic phase solution was poured into the aqueous phase solution, and interfacial polymerization was carried out at 80 °C for 24 h to obtain fluorinated covalent organic framework nanoparticles. The fluorinated covalent organic framework nanoparticles were prepared into a 0.05 wt% dispersion, ultrasonicated at 25 °C and 40 kHz for 15 min, and then pressure filtered at 0.1 MPa and 25 °C to form a fluorinated covalent organic framework nanomembrane on the surface of a nylon microfiltration membrane. 0.2 g piperazine was dissolved in 100 g of 40 wt% sodium hydroxide aqueous solution to prepare a piperazine aqueous solution. 0.132 g pyromellitic chloride was dissolved in 100 g of IsoparG organic solvent to prepare a crosslinking agent solution. The piperazine aqueous solution was then immersed on the surface of a fluorinated covalent organic framework nanomembrane for 10 min. After removing excess piperazine aqueous solution, a fluorinated covalent organic framework nanomembrane loaded with piperazine monomer was formed. The pyromellitic chloride IsoparG solution was then poured onto the surface of the above nanomembrane, and an interfacial confined crosslinking reaction was carried out at 25 °C for 1.5 min. After removing excess pyromellitic chloride IsoparG solution, the membrane was dried at 60 °C for 10 min to obtain an interfacial confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane.

[0018] Solvent-resistant nanofiltration membranes with interfacial confined crosslinking fluorinated covalent organic frameworks, used at 25°C and 0.2 MPa pressure, for 0.05 g·L⁻¹ -1 The filtration separation efficiency of doxorubicin hydrochloride and tetracycline methanol solution was as follows: methanol permeation flux was 15.2 L·m⁻¹. -2 ·h -1 ·bar -1 The retention rates for doxorubicin hydrochloride and tetracycline were 98.8% and 98.7%, respectively.

[0019] Comparative Example 1 Following the steps of Example 3, fluorinated covalent organic framework nanoparticles were prepared using 1,3,5-tris(4-aminophenyl)benzene and 2,3,5,6-tetrafluoro-p-dibenzaldehyde as raw materials. The fluorinated covalent organic framework nanoparticles were formulated into a dispersion and subjected to ultrasonic treatment. Then, they were subjected to pressure filtration (preparation conditions as described in Example 3) to form a fluorinated covalent organic framework nanomembrane on the surface of a nylon microfiltration membrane.

[0020] Comparative Example 2 Following the steps in Example 3, a polyamide membrane was prepared by directly using piperazine and pyromellitic trimethylol chloride as raw materials and performing an interfacial crosslinking reaction on the surface of a nylon microfiltration membrane (preparation conditions as described in Example 3).

[0021] Table 1. Comparison of separation performance of different types of membranes prepared in Example 3 and Comparative Examples 1-2

[0022] The results in Table 1 show that composite membranes can be prepared by all three methods, but there are significant differences in their methanol permeation flux and antibiotic molecule rejection rates. This is because the membrane preparation methods and membrane materials are different, which leads to significant differences in the physicochemical structure and separation performance of the resulting membranes.

[0023] In Comparative Example 1, fluorinated covalent organic framework nanoparticles were used as building blocks to self-assemble into a loosely structured nano-separation layer on the surface of a porous support membrane. This resulted in a high methanol flux but a very low rejection rate for small antibiotic molecules. In Comparative Example 2, a polyamide composite membrane was prepared by interfacial polymerization using polyamine monomers and crosslinking agent monomers as film-forming materials. The polyamide molecular chains within the membrane were densely crosslinked, resulting in high mass transfer resistance, very low methanol flux, and a high rejection rate for antibiotic molecules. These results indicate that polymer membranes prepared using either covalent organic framework nanoparticles or polyamide polymers alone struggle to overcome the trade-off between solvent permeability and separation selectivity.

[0024] In Example 3, fluorinated covalent organic framework nanoparticles were used as the main film-forming material. A fluorinated covalent organic framework nanomembrane was formed by self-assembly on the surface of a porous support membrane through pressure filtration. Further, polyamine monomer molecules and crosslinking agents underwent interfacial confined crosslinking reactions within the confined space formed by the aforementioned nanomembranes, resulting in a solvent-resistant nanofiltration membrane with a continuous pore structure. The pore size of this membrane can be controlled at the sub-nanometer scale, and the pore walls are hydrophobic, enabling the membrane to possess both high solute selectivity and high solvent permeability. Simultaneously, the membrane is primarily composed of rigid framework fluorinated covalent organic framework nanomaterials with strong covalent crosslinking, giving the membrane excellent solvent resistance during long-term service.

[0025] Example 4: 0.036 g of p-phenylenediamine was dissolved in 100 g of an aqueous solution containing 0.5 wt% p-toluenesulfonic acid to prepare an aqueous phase solution. 0.0315 g of 2,4-difluorobenzaldehyde was dissolved in 100 g of a dimethyl sulfoxide-n-hexane mixed solvent to prepare an organic phase solution. The organic phase solution was poured into the aqueous phase solution, and interfacial polymerization was carried out at 70 °C for 12 h to obtain fluorinated covalent organic framework nanoparticles. A 0.01 wt% dispersion of the fluorinated covalent organic framework nanoparticles was prepared, ultrasonically treated at 25 °C and 25 kHz for 20 min, and then pressure filtered at 0.1 MPa and 20 °C. The resulting fluorinated covalent organic framework nanomembrane self-assembled on the surface of a cellulose triacetate microfiltration membrane. 0.1 g of ethylenediamine was dissolved in 100 g of 10 wt% sodium bicarbonate aqueous solution to prepare an ethylenediamine aqueous solution. 0.1 g of terephthaloyl chloride was dissolved in 100 g of cyclohexane organic solvent to prepare a crosslinking agent solution. The ethylenediamine aqueous solution was then immersed on the surface of a fluorinated covalent organic framework nanomembrane for 10 min. After removing excess ethylenediamine aqueous solution, a fluorinated covalent organic framework nanomembrane loaded with ethylenediamine monomer was formed. A terephthaloyl chloride cyclohexane solution was then poured onto the surface of the above nanomembrane, and an interfacial confined crosslinking reaction was carried out at 25 °C for 5 min. After removing excess terephthaloyl chloride cyclohexane solution, the membrane was dried at 60 °C for 15 min to obtain an interfacial confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane.

[0026] Solvent-resistant nanofiltration membranes with interfacial confined crosslinking fluorinated covalent organic frameworks, used at 25°C and 0.2 MPa pressure, for 0.05 g·L⁻¹ -1 The filtration separation efficiency of doxorubicin hydrochloride and tetracycline methanol solution was as follows: methanol permeation flux was 17.4 L·m⁻¹. -2 ·h -1 ·bar -1 The retention rates for doxorubicin hydrochloride and tetracycline were 97.2% and 98.5%, respectively.

[0027] Example 5: 0.072 g of tetrakis(4-aminophenyl)methane was dissolved in 100 g of an aqueous solution containing 1 wt% formic acid to prepare an aqueous phase solution. 0.063 g of 2-fluorobenzaldehyde was dissolved in 100 g of cyclohexane to prepare an organic phase solution. The organic phase solution was then added to the aqueous phase solution, and interfacial polymerization was carried out at 80 °C for 24 h to obtain fluorinated covalent organic framework nanoparticles. The fluorinated covalent organic framework nanoparticles were prepared into a 0.02 wt% dispersion, sonicated at 25 °C and 30 kHz for 25 min, and then pressure filtered at 0.1 MPa and 25 °C to self-assemble into a fluorinated covalent organic framework nanomembrane on the surface of a polytetrafluoroethylene microfiltration membrane. 0.15 g of diethylenetriamine was dissolved in 100 g of 25 wt% sodium phosphate aqueous solution to prepare a diethylenetriamine aqueous solution. 0.15 g of pyromellitic diisocyanate was dissolved in 100 g of cyclohexane organic solvent to prepare a crosslinking agent solution. The diethylenetriamine aqueous solution was then immersed on the surface of a fluorinated covalent organic framework nanomembrane for 15 min. After removing the excess diethylenetriamine aqueous solution, a fluorinated covalent organic framework nanomembrane loaded with diethylenetriamine monomer was formed. A pyromellitic diisocyanate cyclohexane solution was then poured onto the surface of the above nanomembrane, and an interfacial confined crosslinking reaction was carried out at 30 °C for 20 min. After removing the excess pyromellitic diisocyanate cyclohexane solution, the membrane was dried at 70 °C for 10 min to obtain an interfacial confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane.

[0028] Solvent-resistant nanofiltration membranes with interfacial confined crosslinking fluorinated covalent organic frameworks, used at 25°C and 0.2 MPa pressure, for 0.05 g·L⁻¹ -1 The filtration separation efficiency of doxorubicin hydrochloride and tetracycline methanol solution was as follows: methanol permeation flux was 17.3 L·m⁻¹. -2 ·h -1 ·bar -1 The retention rates for doxorubicin hydrochloride and tetracycline were 98.4% and 97.6%, respectively.

[0029] Example 6: 0.036 g of melamine was dissolved in 100 g of an aqueous solution containing 3 wt% trifluoroacetic acid to prepare an aqueous phase solution. 0.0315 g of 2,3,5,6-tetrafluoro-p-dibenzaldehyde was dissolved in 100 g of IsoparG solvent to prepare an organic phase solution. The organic phase solution was then added to the aqueous phase solution, and interfacial polymerization was carried out at 80 °C for 24 h to obtain fluorinated covalent organic framework nanoparticles. A 0.03 wt% dispersion of the fluorinated covalent organic framework nanoparticles was prepared, ultrasonically treated at 35 °C and 40 kHz for 20 min, and then pressure filtered at 0.15 MPa and 20 °C. This resulted in the self-assembly of fluorinated covalent organic framework nanomembranes on the surface of a polyvinylidene fluoride (PVDF) microfiltration membrane. 0.3 g of cyclohexanediamine was dissolved in 100 g of 30 wt% sodium carbonate aqueous solution to prepare a cyclohexanediamine aqueous solution. 0.3 g of N-hydroxysuccinimide ester was dissolved in 100 g of n-heptane organic solvent to prepare a crosslinking agent solution. The cyclohexanediamine aqueous solution was then immersed on the surface of the fluorinated covalent organic framework nanomembrane for 10 min. After removing the excess cyclohexanediamine aqueous solution, a fluorinated covalent organic framework nanomembrane loaded with cyclohexane monomer was formed. The N-hydroxysuccinimide ester n-heptane solution was then poured onto the surface of the above nanomembrane. An interface-confined crosslinking reaction was carried out at 20 °C for 15 min. After removing the excess N-hydroxysuccinimide ester n-heptane solution, the membrane was dried at 80 °C for 15 min to obtain an interface-confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane.

[0030] Solvent-resistant nanofiltration membranes with interfacial confined crosslinking fluorinated covalent organic frameworks, used at 25°C and 0.2 MPa pressure, for 0.05 g·L⁻¹ -1 The filtration separation efficiency of doxorubicin hydrochloride and tetracycline methanol solution was as follows: methanol permeation flux was 16.7 L·m⁻¹. -2 ·h -1 ·bar -1 The retention rates for doxorubicin hydrochloride and tetracycline were 97.9% and 98.5%, respectively.

[0031] Example 7: 0.108 g of 1,3,5-tris(4-aminophenyl)benzene was dissolved in 100 g of an aqueous solution containing 4 wt% polyphosphoric acid to prepare an aqueous phase solution. 0.0315 g of p-fluorobenzaldehyde was dissolved in 100 g of n-hexane to prepare an organic phase solution. The organic phase solution was then added to the aqueous phase solution, and interfacial polymerization was carried out at 60 °C for 12 h to obtain fluorinated covalent organic framework nanoparticles. A 0.01 wt% dispersion of the fluorinated covalent organic framework nanoparticles was prepared, ultrasonically treated at 25 °C and 40 kHz for 10 min, and then pressure filtered at 0.2 MPa and 30 °C to self-assemble on the surface of a nylon microfiltration membrane to form a fluorinated covalent organic framework nanomembrane. 0.22 g of m-phenylenediamine was dissolved in 100 g of 35 wt% triethylamine aqueous solution to prepare an aqueous solution of m-phenylenediamine. 0.25 g of N-hydroxysuccinimide ester was dissolved in 100 g of n-hexane organic solvent to prepare a crosslinking agent solution. The aqueous solution of m-phenylenediamine was then immersed on the surface of the fluorinated covalent organic framework nanomembrane for 10 min. After removing the excess aqueous solution of m-phenylenediamine, a fluorinated covalent organic framework nanomembrane loaded with m-phenylenediamine monomer was formed. The n-hexane solution of N-hydroxysuccinimide ester was then poured onto the surface of the above nanomembrane and subjected to an interface-confined crosslinking reaction at 20 °C for 10 min. After removing the excess n-hexane solution of N-hydroxysuccinimide ester, the membrane was dried at 60 °C for 10 min to obtain an interface-confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane.

[0032] Solvent-resistant nanofiltration membranes with interfacial confined crosslinking fluorinated covalent organic frameworks, used at 25°C and 0.2 MPa pressure, for 0.05 g·L⁻¹ -1 The filtration separation efficiency of doxorubicin hydrochloride and tetracycline methanol solution was as follows: methanol permeation flux was 15.3 L·m⁻¹. -2 ·h -1 ·bar -1 The retention rates for doxorubicin hydrochloride and tetracycline were 98.6% and 97.8%, respectively.

[0033] Example 8: 0.076 g of melamine was dissolved in 100 g of an aqueous solution containing 0.5 wt% acetic acid to prepare an aqueous phase solution. 0.0315 g of p-trifluoromethylbenzaldehyde was dissolved in 100 g of IsoparG solvent to prepare an organic phase solution. The organic phase solution was poured into the aqueous phase solution and interfacial polymerization was carried out at 65 °C for 72 h to obtain fluorinated covalent organic framework nanoparticles. The above-mentioned fluorinated covalent organic framework nanoparticles were prepared into a 0.02 wt% dispersion, sonicated at 20 °C and 30 kHz for 15 min, and then filtered under pressure at 0.2 MPa and 25 °C. This allowed the fluorinated covalent organic framework nanomembrane to self-assemble on the surface of a cellulose triacetate microfiltration membrane. A m-phenylenediamine aqueous solution was prepared by dissolving 0.15 g of m-phenylenediamine in 100 g of a 40 wt% triethylamine aqueous solution. A crosslinking agent solution was prepared by dissolving 0.2 g of trimesoyl chloride in 100 g of n-hexane. The m-phenylenediamine aqueous solution was then immersed in the surface of the fluorinated covalent organic framework nanomembrane for 10 min, and excess m-phenylenediamine was removed, forming a fluorinated covalent organic framework nanomembrane loaded with m-phenylenediamine monomers. A trimesoyl chloride n-hexane solution was then poured onto the surface of the nanomembrane, and an interfacial confined crosslinking reaction was carried out at 25 °C for 10 minutes. After removing excess pyromellitic methyl chloride hexane solution by 1 min, the membrane is dried at 60 °C for 15 min to obtain an interface-confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane.

[0034] Solvent-resistant nanofiltration membranes with interfacial confined crosslinking fluorinated covalent organic frameworks, used at 25°C and 0.2 MPa pressure, for 0.05 g·L⁻¹ -1 The filtration separation effect of doxorubicin hydrochloride and tetracycline methanol solution was as follows: methanol permeation flux was 17 L·m -2 ·h -1 ·bar -1 The retention rates for doxorubicin hydrochloride and tetracycline were 98.7% and 98.0%, respectively.

Claims

1. A method for preparing an interface-confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane, characterized in that: Includes the following steps: 1) Dissolve 0.05~0.3 parts by mass of aromatic amine monomer in 100 parts by mass of aqueous solution containing catalyst to prepare an aqueous solution, and dissolve 0.02~0.1 parts by mass of fluorinated aromatic aldehyde monomer in 100 parts by mass of organic solvent to prepare an organic solution. Pour the above organic solution into the aqueous solution and carry out interfacial polymerization reaction to obtain fluorinated covalent organic framework nanoparticles. 2) The above-mentioned fluorinated covalent organic framework nanoparticles were prepared into a dilute dispersion, and after ultrasonic treatment, they were filtered under pressure to form a fluorinated covalent organic framework nanoparticle membrane on the surface of a porous support membrane. 3) Dissolve 0.05-0.3 parts by mass of polyamine monomer molecules in 100 parts by mass of alkaline aqueous solution to prepare a polyamine aqueous solution; dissolve 0.1-0.3 parts by mass of crosslinking agent molecules in 100 parts by mass of organic solvent to prepare a crosslinking agent solution; then immerse the polyamine aqueous solution on the surface of the fluorinated covalent organic framework nanomembrane obtained in step 2), remove excess polyamine aqueous solution to form a fluorinated covalent organic framework nanomembrane loaded with polyamine monomers; then pour the crosslinking agent solution onto the surface of the above nanomembrane, and carry out an interface-confined crosslinking reaction at 20-30℃ for 1-20 min, remove excess crosslinking agent solution, and finally dry to obtain an interface-confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane.

2. The method for preparing the solvent-resistant nanofiltration membrane of the interface-confined crosslinked fluorinated covalent organic framework as described in claim 1, characterized in that: The aromatic amine monomer molecule mentioned in step 1) is selected from p-phenylenediamine, melamine, tetra(4-aminophenyl)methane, or 1,3,5-tris(4-aminophenyl)benzene; the catalyst mentioned in step 1) is selected from acetic acid, p-toluenesulfonic acid, formic acid, trifluoroacetic acid, or polyphosphoric acid; the fluorinated aromatic aldehyde monomer molecule mentioned in step 1) is selected from 2-fluorobenzaldehyde, 2,4-difluorobenzaldehyde, p-fluorobenzaldehyde, p-trifluoromethylbenzaldehyde, or 2,3,5,6-tetrafluorop-diphenylaldehyde; the organic phase solvent mentioned in step 1) is one or more mixed solvents selected from n-hexane, dimethyl sulfoxide, cyclohexane, or isoparaffinic hydrocarbons IsoparG.

3. The method for preparing the solvent-resistant nanofiltration membrane of the interface-confined crosslinked fluorinated covalent organic framework as described in claim 1, characterized in that: The porous support membrane mentioned in step 2) is selected from one of the following: cellulose triacetate microfiltration membrane, nylon microfiltration membrane, polyvinylidene fluoride microfiltration membrane, or polytetrafluoroethylene microfiltration membrane.

4. The method for preparing the solvent-resistant nanofiltration membrane of the interface-confined crosslinked fluorinated covalent organic framework as described in claim 1, characterized in that: The polyamine monomer molecule mentioned in step 3) is selected from one of ethylenediamine, diethylenetriamine, cyclohexanediamine, m-phenylenediamine, or piperazine; the alkali in the alkaline aqueous solution mentioned in step 3) is selected from one of sodium hydroxide, sodium bicarbonate, sodium phosphate, sodium carbonate, or triethylamine; the crosslinking agent molecule mentioned in step 3) is selected from one of pyromellitic acid, terephthaloyl chloride, toluene diisocyanate, or N-hydroxysuccinimide ester; the organic phase solvent mentioned in step 3) is one or more of cyclohexane, n-heptane, n-hexane, or IsoparG.

5. The method for preparing an interface-confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane according to any one of claims 1-4, characterized in that: The mass percentage concentration of the catalyst in the aqueous solution of the catalyst mentioned in step 1) is 0.5-5%; the interfacial polymerization reaction conditions mentioned in step 1) are 60-80℃ for 12-72 h.

6. The method for preparing an interface-confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane according to any one of claims 1-4, characterized in that: The mass percentage concentration of fluorinated covalent organic framework nanoparticles in the dilute dispersion in step 2) is 0.01~0.05%; the ultrasonic treatment conditions in step 2) are 20~40℃, ultrasonicated at 20~40KHZ for 10~30min; the pressure filtration conditions in step 2) are filtration at 20~30℃ and 0.1~0.3 MPa pressure.

7. The method for preparing an interface-confined crosslinked fluorinated covalent organic framework solvent-resistant nanofiltration membrane according to any one of claims 1-4, characterized in that: The mass percentage concentration of the alkaline aqueous solution in step 3) is 10-40%; the immersion time of the polyamine aqueous solution in step 3) is 10-30 min; and the drying conditions in step 3) are drying at 50-80℃ for 5-20 min.

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