CN108159893B - Metal organic framework composite ultrafiltration membrane material and preparation and application thereof - Google Patents

Abstract

The invention discloses a metal-organic framework composite ultrafiltration membrane material and its preparation and application, belonging to the technical field of water treatment. Aiming at the problems that the purification of various tetraoxate inorganic anions in the current industrial production discharge water is difficult to handle and the existing adsorption materials are insufficient, the present invention firstly synthesized a metal-organic framework polymer with special selectivity for regular tetrahedral structure tetraoxate anions. At the same time, the preparation method of the novel environmental functional composite membrane material-metal organic framework composite ultrafiltration membrane material is created, and the composite membrane material of the present invention can efficiently realize ClO ₄ ^, PO ₄ ³ , TcO ₄ ^, One-step separation of tetrahedral-structured tetraoxoate anion pollutants such as CrO ₄ ^‑ and AsO ₄ ^3‑ .

Description

A kind of metal organic framework composite ultrafiltration membrane material and its preparation and application

technical field

The invention belongs to the technical field of water treatment, and more particularly relates to a metal-organic framework composite ultrafiltration membrane material and its preparation and application.

Background technique

Metal-organic framework coordination polymers are a new type of porous coordination polymer materials. Since their discovery, they have received extensive attention from researchers for more than ten years. From their initial interest in synthesizing a wide variety of structures, they now focus on the environmental field. important progress has been made in the application. Due to some advantages of metal organic framework coordination polymers, such as large specific surface area, many active sites, and easy control of crystal structure, they are widely used in energy gas storage, separation and catalysis; at the same time, due to their water stability The defect of low performance makes it relatively backward in the research direction of water environment pollution treatment. Generally speaking, aside from its water stability, metal-organic framework coordination polymers have great advantages in the removal of ionic pollutants in water compared with other adsorption materials. First, its huge specific surface area and a large number of active sites can efficiently enrich ionic pollutants in water; secondly, its easy-to-control structure enables it to give full play to its selection advantages for target pollutants in water; finally, when the water environment When complex and changeable, target pollutants, especially low-concentration ionic pollutants with small hydration radius, metal-organic framework coordination polymers can achieve high-efficiency enrichment and capture of target ions (Fei H, Rogow DL, Oliver SR. Reversible anion exchange and catalytic properties of two cationic metal-organic frameworks based on Cu(I) and Ag(I)[J]. Journal of the American Chemical Society, 2010, 132(20): 7202-7209; Honghan Fei, Latisha Paw U , DavidL.Rogow,etc.Synthesis,Characterization,and Catalytic Application of aCationic Metal-Organic Framework:Ag ₂ (4,4′-bipy) ₂ (O ₃ SCH ₂ CH ₂ SO ₃ )[J].Chemistry of Materials,2010 , 22(6), 2027-2032). Therefore, how to improve the stability of metal-organic framework coordination polymers in water has become the primary goal of vigorously developing this new type of environmental functional material.

As a common method for synthesizing new materials in the environmental field, loading can coordinate various substances that are not related to each other to form a unified whole, and complement each other to play their respective environmental functions. Therefore, metal organic framework coordination polymers are loaded on membranes. The formation of composite films on the surface has become a research hotspot nowadays. The composite of this functional material and membrane can not only play the role of metal-organic framework coordination polymer to remove target pollutants, but also realize one-step separation of water pollutants without secondary treatment. At the same time, the problem of water stability of metal-organic framework coordination polymers can be solved. In terms of the combination method, some research results have been obtained in the preparation of this composite membrane: Chinese patent 201510446599.6 published on December 9, 2015 discloses a method for preparing a reverse diffusion in-situ self-assembled MOFs nanofiltration membrane, By in situ forming a hybrid separation layer of MOFs/polymer on the surface of the base membrane, and controlling the concentration and diffusion time of the solution on both sides of the base membrane to control the structure of the separation layer, the nano hybrid membrane of MOFs was formed, which was successfully applied to dye removal. However, the MOFs film growth obtained by in situ growth by this method is relatively lack of uniformity; Chinese patent 201710371618.2 published on August 8, 2017 introduces a new preparation method of MOFs-PVDF composite film, which solves the problem of partial film. In the modification method, there are problems of poor hydrophilicity of the membrane, agglomeration of nanoparticles, and low mechanical strength, but this method has many operation steps and is difficult to apply.

Tetrahedral tetrahedral anions, such as ClO ₄ ^- , PO ₄ ^3- , TcO ₄ ^- , CrO ₄ ^- , AsO ₄ ^3- , etc. are common anionic pollutants in natural water bodies, and most of their salts All species have good water solubility, and are difficult to volatilize or be naturally degraded. At the same time, they diffuse quickly in the surface or groundwater environment, retain for a long time, and have bioaccumulation. With the production activities of human beings, more and more such anionic pollutants enter the natural water body through industrial discharge, and participate in the material cycle of nature, causing serious harm to the ecological environment over time. Once these anions enter the human body through the environment through the food chain, and then circulate from body fluids to various organs, if they accumulate to a certain concentration, they will cause human body dysfunction and organ damage.

At present, the commonly used treatment methods for such pollutants are: adsorption, precipitation, chemical/electroreduction, and biodegradation. Due to the high stability and chemical inertness, high solubility and high toxicity of such pollutants, common physical methods such as precipitation are basically ineffective; chemical/electroreduction treatment efficiency is not high, and energy consumption is high; although biodegradation reduction has a certain treatment effect , but the requirements for environmental conditions are high, and microorganisms are difficult to domesticate. Therefore, the adsorption method is currently the most suitable method to deal with such water pollution. However, due to the low concentration of such anions in natural water, and at the same time, there are many other common inorganic anions in the water. Interference, such as chloride ion, sulfate ion , nitrate ions, fluoride ions, etc. Therefore, the competition effect of coexisting ions is also the main factor affecting the treatment effect. Therefore, it is the key to find an adsorbent material with high efficiency, high selectivity and no environmental influence.

SUMMARY OF THE INVENTION

1. The problem to be solved

In view of the problems that the purification of various tetraoxoate inorganic anions in the current industrial production discharge water is difficult to handle and the existing adsorption materials are insufficient, the present invention provides a metal-organic framework composite ultrafiltration membrane material, and correspondingly provides the composite ultrafiltration membrane. The preparation method can efficiently realize the one-step separation of tetrahedral structure tetraoxoate anion pollutants such as ClO ₄ ^- , PO ₄ ³ - , TcO ₄ ^- , CrO ₄ ^- , AsO ₄ ^3- and the like in water.

2. Technical solutions

In order to solve the above problems, the technical scheme adopted in the present invention is as follows:

A metal-organic framework composite ultrafiltration membrane material, which uses polyvinylidene fluoride as a membrane carrier and a metal-organic framework coordination polymer as a load, and the two are combined through hydroxyl groups;

The metal organic framework coordination polymer has a basic chain structure of "bipy-Cu-bipy", and the bipy is 2,2'-bipyridine.

Further, the metal-organic framework composite ultrafiltration membrane material is used for the treatment of tetrahedral structure tetraoxoate anions polluted water body, and the normal tetrahedral structure tetraoxoate anions include ClO ₄ ^- , PO ₄ ³ - , TcO One or more of ₄ ^- , CrO ₄ ^- , AsO ₄ ³ , and MnO ₄ ^- .

The preparation method of the metal-organic framework composite ultrafiltration membrane material comprises the following steps:

(1) After mixing and dissolving bipyridine, copper nitrate, sodium oxalate and water according to the molar ratio of (0.9-1.2): (1-1.1): (1.05-1.35): (510-550), under certain conditions The following reaction is performed, and the obtained mixed product is repeatedly washed with water and ethanol to separate a solid product, and oven-dry to obtain a metal-organic framework coordination polymer;

(2) Mix butyrolactone, polyvinylidene fluoride and dimethylacetamide in a molar ratio of (0.3-0.6): (7.5-10.7): (36-40), and after stirring the reaction under certain conditions, the The casting liquid is poured on a smooth and flat glass plate, and after being scraped, it is immersed in pure water for a period of time to form a polyvinylidene fluoride film, which is then soaked in alkali solution for a period of time;

(3) Immerse the polyvinylidene fluoride film obtained in step (2) in a benzyl chloride/n-heptane solution for a period of time, and then immerse it in a 5-50 wt% metal-organic framework coordination polymer/n-hexane mixed solution , that is, a metal-organic framework composite ultrafiltration membrane material with a loading of 5-50 wt % is obtained.

Further, the reaction temperature of the step (1) is 160-190° C., the reaction time is 3-5 days, and the reaction device is an autoclave.

Further, the reaction temperature of the step (2) is 40-50° C., the stirring time is 6-10 hours, and the reaction environment is an anaerobic environment.

Further, the alkali solution in the step (2) is a mixture of one or both of sodium hydroxide solution and potassium hydroxide solution, and the concentration of the alkali solution is 20-23wt%.

Further, the soaking time of the membrane in the step (2) is 5-10 minutes in pure water, and the soaking time in the alkaline solution is 30-50 minutes.

Further, the concentration of benzyl chloride in the benzyl chloride/n-heptane solution in the step (3) is 0.1-0.5wt%.

Further, in the step (3), the soaking time of the polyvinylidene fluoride film in the benzyl chloride/n-heptane solution is 10-30 minutes.

Further, in the step (3), the soaking time of the polyvinylidene fluoride film in the metal organic framework coordination polymer/n-hexane mixed solution is 30-60 minutes.

3. Beneficial effects

Compared with the prior art, the beneficial effects of the present invention are:

(1) The present invention firstly synthesizes a metal-organic framework polymer with special selectivity to tetrahedral structure tetraoxate anion, and provides a preparation method of the novel environmental functional composite membrane material. The preparation method is simple and effectively solves the problem. The poor hydrophilicity of the membrane caused by the general blending method, the agglomeration of the polymer particles leads to the poor dispersion of the casting solution, and it is easy to block the membrane pores, thereby reducing the water flux of the metal-organic framework composite membrane and low mechanical strength. This combination method has good innovation and reference significance for the compounding of the same type of substances or the compounding of different types of substances;

(2) The metal-organic framework coordination polymer in the present invention is designed for the tetrahedral anion of the target tetrahedral structure, and has selective specificity for the target, so the treatment effect is good, even if the concentration of various coexisting anions is far away When higher than the target anion, advanced treatment and safety control can still be achieved.

Description of drawings

Fig. 1 is the synthesis and structural representation of the metal-organic framework composite ultrafiltration membrane material of the present invention;

Fig. 2 is the scanning electron microscope schematic diagram of the composite ultrafiltration membrane material of the present invention, wherein a is the SEM image of the original PVDF membrane surface after magnification of 500 times; b is the metal-organic framework composite ultrafiltration with a loading amount of 30wt% after magnification of 500 times SEM image of the membrane surface;

3 is a graph showing the outflow curve of the metal-organic composite ultrafiltration membrane material with the loading amount of 30 wt% to perchlorate in the present invention.

Detailed ways

The present invention will be further described below with reference to specific embodiments.

Example 1

The preparation method of the metal-organic framework composite ultrafiltration membrane material of the present embodiment comprises the following steps:

(1) after mixing and dissolving bipyridine, copper nitrate, sodium oxalate and water according to the molar ratio of 0.9:1:1.05:510, react at 160° C. for 3 days in an autoclave, and the obtained mixed product is subjected to water and After repeated washing with ethanol, the solid product is separated and dried to obtain a metal-organic framework coordination polymer with "bipy-Cu-bipy" as the basic chain structure;

(2) Mix butyrolactone, polyvinylidene fluoride and dimethylacetamide in a molar ratio of 0.3:7.5:36, heat and stir at 40°C for 6 hours under anaerobic conditions, pour the casting liquid on a smooth surface After scraping the glass plate, soak it in pure water for 5 minutes, and then soak the resulting polyvinylidene fluoride film in a sodium hydroxide solution with a concentration of 20wt% for 30 minutes;

(3) The polyvinylidene fluoride film obtained in step (2) was immersed in a 0.1 wt% benzyl chloride/n-heptane solution for 10 minutes, and then immersed in a 5 wt% "bipy-Cu-bipy" metal-organic framework for coordination The polymer/n-hexane mixed solution was placed in the mixed solution for 30 minutes to obtain a metal-organic framework composite ultrafiltration membrane material with a loading of 5 wt%.

Figure 1 is a schematic diagram of the synthesis and structure of the metal-organic framework composite ultrafiltration membrane material.

Example 2

The preparation method of the metal-organic framework composite ultrafiltration membrane material of the present embodiment comprises the following steps:

(1) after mixing and dissolving bipyridine, copper nitrate, sodium oxalate and water according to the molar ratio of 1.2:1.1:1.35:550, react at 190° C. for 5 days in an autoclave, and the obtained mixed product is subjected to water and After repeated washing with ethanol, the solid product is separated and dried to obtain a metal-organic framework coordination polymer with "bipy-Cu-bipy" as the basic chain structure;

(2) Mix butyrolactone, polyvinylidene fluoride and dimethylacetamide in a molar ratio of 0.6:10.7:40, heat and stir at 50°C for 10 hours under anaerobic conditions, pour the casting liquid on a smooth surface After scraping the glass plate, soak it in pure water for 10 minutes, and then soak the resulting polyvinylidene fluoride film into a sodium hydroxide solution with a concentration of 23wt% for 50 minutes;

(3) The polyvinylidene fluoride film obtained in step (2) was immersed in a 0.5 wt% benzyl chloride/n-heptane solution for 30 minutes, and then immersed in a 10 wt% "bipy-Cu-bipy" metal-organic framework for coordination The polymer/n-hexane mixed solution was placed in the mixed solution for 60 minutes to obtain a metal-organic framework composite ultrafiltration membrane material with a loading of 10 wt%.

Example 3

The preparation method of the metal-organic framework composite ultrafiltration membrane material of the present embodiment comprises the following steps:

(1) After mixing and dissolving bipyridine, copper nitrate, sodium oxalate and water according to the molar ratio of 1:1:1.3:535, react at 180° C. for 4 days in an autoclave, and the obtained mixed product is subjected to water and After repeated washing with ethanol, the solid product is separated and dried to obtain a metal-organic framework coordination polymer with "bipy-Cu-bipy" as the basic chain structure;

(2) Mix butyrolactone, polyvinylidene fluoride and dimethylacetamide in a molar ratio of 0.5:8.2:37, heat and stir at 45°C for 7 hours under anaerobic conditions, pour the casting liquid on a smooth surface After being scraped flat, it was soaked in pure water for 9 minutes, and the resulting polyvinylidene fluoride film was soaked in sodium hydroxide solution with a concentration of 22wt% for 45 minutes;

(3) The polyvinylidene fluoride film obtained in step (2) was immersed in a 0.2 wt% benzyl chloride/n-heptane solution for 25 minutes, and then immersed in a 30 wt% "bipy-Cu-bipy" metal-organic framework for coordination The polymer/n-hexane mixed solution was placed in the mixed solution for 55 minutes to obtain a metal-organic framework composite ultrafiltration membrane material with a loading of 30 wt%.

Example 4

The preparation method of the metal-organic framework composite ultrafiltration membrane material of the present embodiment comprises the following steps:

(1) After mixing and dissolving bipyridine, copper nitrate, sodium oxalate and water according to the molar ratio of 1:1:1.3:535, react at 180° C. for 4 days in an autoclave, and the obtained mixed product is subjected to water and After repeated washing with ethanol, the solid product is separated and dried to obtain a metal-organic framework coordination polymer with "bipy-Cu-bipy" as the basic chain structure;

(2) Mix butyrolactone, polyvinylidene fluoride and dimethylacetamide in a molar ratio of 0.5:8.2:37, heat and stir at 45°C for 7 hours under anaerobic conditions, pour the casting liquid on a smooth surface After being scraped flat, it was soaked in pure water for 9 minutes, and the resulting polyvinylidene fluoride film was soaked in potassium hydroxide solution with a concentration of 22wt% for 45 minutes;

(3) The polyvinylidene fluoride film obtained in step (2) was immersed in a 0.2 wt% benzyl chloride/n-heptane solution for 25 minutes, and then immersed in a 50 wt% "bipy-Cu-bipy" metal-organic framework for coordination The polymer/n-hexane mixed solution was placed in the mixed solution for 55 minutes to obtain a metal-organic framework composite ultrafiltration membrane material with a loading of 50 wt%.

The mechanical tensile test was carried out on the ordinary polyvinylidene fluoride membrane and the four metal-organic framework composite ultrafiltration membranes with different loadings in Examples 1 to 4, and the results were 16.4MPa, 18.5MPa, 19.2MPa, 21.6MPa in turn. , 13.6MPa, the results show that, compared with other loadings of the composite ultrafiltration membrane, when the loading is 30wt%, the membrane strength is the best.

The contact angle test was carried out on the common polyvinylidene fluoride membrane and the four metal-organic framework composite ultrafiltration membranes with different loadings in Examples 1 to 4, and the obtained results were 87.6°, 57.3°, 41.4°, 39.1° and 36.7°, the results show that the hydrophilicity of the membrane is getting better and better with the increase of the loading and the loading amount of the metal-organic framework coordination polymer, which is beneficial to the application of the membrane material in practical water treatment.

The water flux tests were carried out on ordinary polyvinylidene fluoride membranes and four metal-organic framework composite ultrafiltration membranes with different loadings in Examples 1 to 4, and the results were 417, 413, 396, 387 and 328 L m in turn. ^-2 h ^-1 bar ^-1 , the results show that the loading of the metal-organic framework coordination polymer will block the membrane pores to a certain extent, but when the loading is between 5% and 30%, the water flux of the membrane will not be affected. Changes have little impact.

The anti-fouling tests were carried out on common polyvinylidene fluoride membranes and four metal-organic framework composite ultrafiltration membranes with different loadings in Examples 1 to 4, and the retention rates of the obtained membrane materials for pollutants were 43%, 45 %, 46%, 51% and 89%, the results show that when the load is larger, the interception effect of pollutants is better, and it also shows that it is easier to be polluted.

The scanning electron microscope test was carried out on the ordinary polyvinylidene fluoride membrane and the four kinds of metal-organic framework composite ultrafiltration membranes with different loadings in Examples 1 to 4. The SEM images before and after the metal-organic framework loading shown in Figure 2 can be It can be seen that the metal-organic framework coordination polymer is uniformly dispersed on the surface of the polyvinylidene fluoride membrane, forming a complete metal-organic framework composite ultrafiltration membrane material.

Considering the tensile strength, hydrophilicity, water flux, antifouling property and SEM test results, 30wt% metal-organic framework coordination polymer loading is the most suitable for practical applications.

Example 5

Taking perchlorate (ClO ₄ ^- ) as the representative of the tetrahedral tetrahedral anion, three groups of coexisting anion mixtures (chloride ion/perchlorate ion, bromide ion) were prepared with a volume of 100 mL and a perchlorate concentration of 50 mg/L. /perchlorate ion, nitrate ion/perchlorate ion, the concentration ratio of each group of coexisting ions and perchlorate is set to 0-20), the composite membrane material with a loading of 30wt% is put into the mixed solution, 50 After the reaction for 1 hour, the anion concentration in each group was sampled and analyzed, and the perchlorate removal rate of each group was shown in Table 1.

Table 1 Perchlorate removal rate of composite membrane materials for mixed solutions of different types and concentration ratios of perchlorate coexisting anions

The data in Table 1 shows that under the interference of various coexisting anions, even if the concentration of coexisting anions is high, it has little effect on the actual treatment effect of the composite membrane material. The selectivity of tetraoxoate anion represented by chlorate is generally better than that of other structural forms of anions (such as Cl ^- , Br ^- and NO ₃ ^- ), which proves that the ultrafiltration membrane material of the present invention has selective specificity for tetraoxoate anion .

Example 6

Prepare 25L of perchlorate (ClO ₄ ^- ) solution with a concentration of 10mg/L. Taking the ultrafiltration cup as the reaction device, the ultrafiltration membrane supported by 30wt% activated carbon and the composite ultrafiltration membrane with the metal-organic framework coordination polymer content of 30wt% of the present invention were placed in the ultrafiltration cup respectively, and the experiment of solution passing through the membrane was carried out. . By testing the concentration of perchlorate ions in the effluent, the perchlorate ion efflux curve shown in Figure 3 was obtained, and the treatment capacity of reducing the perchlorate concentration to 2 mg/L was about 800 BV. The treatment capacity of the membrane to reduce the perchlorate concentration to the range of 2mg/L is about 30BV.

Example 7

Prepare 25L of phosphate radical (PO ₄ ^3- ) solution with a concentration of 10 mg/L. Taking the ultrafiltration cup as the reaction device, the ultrafiltration membrane supported by 30wt% activated carbon and the composite ultrafiltration membrane with the metal-organic framework coordination polymer content of 30wt% of the present invention were placed in the ultrafiltration cup respectively, and the experiment of solution passing through the membrane was carried out. . By testing the concentration of phosphate ions in the effluent, the treatment volume that reduces the phosphate concentration to within the range of 2 mg/L is about 650 BV, while the treatment that reduces the phosphate concentration to the range of 2 mg/L compared to the ultrafiltration membrane supported by activated carbon The amount is about 250BV.

Example 8

Prepare 25L of permanganate (MnO ₄ ^- ) solution with a concentration of 10mg/L. Taking the ultrafiltration cup as the reaction device, the ultrafiltration membrane supported by 30wt% activated carbon and the composite ultrafiltration membrane with the metal-organic framework coordination polymer content of 30wt% of the present invention were placed in the ultrafiltration cup respectively, and the experiment of solution passing through the membrane was carried out. . By testing the concentration of permanganate ions in the effluent, the treatment amount that can reduce the concentration of permanganate to 2 mg/L is about 430BV, while the ultrafiltration membrane supported by activated carbon reduces the concentration of permanganate to the range of 2 mg/L. The processing capacity is about 195BV.

The material of the present invention solves the problems of low treatment efficiency, poor selectivity and easy influence of coexisting ions on tetrahedral anions in water by other materials, so it is more suitable for advanced treatment of such polluted water bodies.

Claims (9)

1. A metal organic framework composite ultrafiltration membrane material is characterized in that polyvinylidene fluoride is used as a membrane carrier, a metal organic framework coordination polymer is used as a load, and the polyvinylidene fluoride and the metal organic framework coordination polymer are combined through hydroxyl;

the metal-organic framework coordination polymer takes bipy-Cu-bipy as a basic chain structure, and the bipy is 2, 2' -bipyridine;

the preparation method of the metal organic framework composite ultrafiltration membrane material comprises the following steps:

(1) bipyridine, copper nitrate, sodium oxalate and water are mixed according to the weight ratio of (0.9-1.2): (1-1.1): (1.05-1.35): (510-550), reacting under certain conditions after mixing and dissolving in a molar ratio, repeatedly washing the obtained mixed product with water and ethanol, separating out a solid product, and drying to obtain a metal organic framework coordination polymer;

(2) butyrolactone, polyvinylidene fluoride and dimethylacetamide according to the weight ratio of (0.3-0.6): (7.5-10.7): (36-40), stirring and reacting under certain conditions, pouring the casting solution on a smooth and flat glass plate, leveling, placing the glass plate in pure water for soaking for a period of time to generate a polyvinylidene fluoride membrane, and soaking the generated polyvinylidene fluoride membrane in alkali liquor for a period of time;

(3) and (3) soaking the polyvinylidene fluoride membrane obtained in the step (2) in a benzyl chloride/n-heptane solution for a period of time, and then soaking the polyvinylidene fluoride membrane in a 5-50 wt% metal-organic framework coordination polymer/n-hexane mixed solution to obtain the metal-organic framework composite ultrafiltration membrane material.

2. The metal-organic framework composite ultrafiltration membrane material of claim 1, wherein the metal-organic framework composite ultrafiltration membrane material is used for treatment of water polluted by regular tetrahedron-structured tetraalkoxide anions comprising C1O₄ ^-、PO₄ ^3-、TcO₄ ^-、CrO₄ ^-、AsO₄ ³、MnO₄ ^-One or more than one of (a).

3. The metal-organic framework composite ultrafiltration membrane material as claimed in claim 1, wherein the reaction temperature in the step (1) is 160-190 ℃, the reaction time is 3-5 days, and the reaction device is a high-pressure reaction kettle.

4. The metal-organic framework composite ultrafiltration membrane material according to claim 1 or 3, wherein the reaction temperature in the step (2) is 40-50 ℃, the stirring time is 6-10 hours, and the reaction environment is an anaerobic environment.

5. The metal-organic framework composite ultrafiltration membrane material of claim 4, wherein the alkali solution in the step (2) is one or a mixture of a sodium hydroxide solution and a potassium hydroxide solution, and the concentration of the alkali solution is 20-23 wt%.

6. The metal-organic framework composite ultrafiltration membrane material according to claim 1 or 5, wherein the membrane in the step (2) is soaked in pure water for 5-10 minutes and in alkaline solution for 30-50 minutes.

7. The metal-organic framework composite ultrafiltration membrane material according to claim 1 or 5, wherein the concentration of the benzyl chloride in the benzyl chloride/n-heptane solution of step (3) is 0.1-0.5 wt%.

8. The metal-organic framework composite ultrafiltration membrane material of claim 7, wherein the soaking time of the polyvinylidene fluoride membrane in the benzyl chloride/n-heptane solution in the step (3) is 10-30 minutes.

9. The metal-organic framework composite ultrafiltration membrane material according to claim 1 or 8, wherein the soaking time of the polyvinylidene fluoride membrane in the metal-organic framework coordination polymer/n-hexane mixed solution in the step (3) is 30-60 minutes.

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