Metal organic framework fiber membrane and application

Abstract

The application belongs to the field of MOF functional films, and relates to a metal organic framework fiber film and application. The metal organic framework fiber film is prepared by a method comprising the following steps: dissolving polyacrylonitrile, tetra(4-tetrazolylphenyl)ethylene and ethylene glycol dimethyl methacrylate in a first organic solvent to obtain a spinning solution; electrospinning the spinning solution and vacuum drying to obtain a PAN / H4TTPE film; immersing the PAN / H4TTPE film in a methanol solution containing azobisdimethyl isopropyl cyanide and irradiating and cross-linking under a UV lamp; contacting the cross-linked PAN / H4TTPE film with a Cu(NO3)2.3H2O solution, then adding concentrated hydrochloric acid, and slowly shaking until the solution is yellow-green; and then sealing and heating to react to obtain a metal organic framework fiber film MOF / PAN. The MOF / PAN fiber film prepared by the application has the advantages of simple preparation method, low cost, good stability and removal effect, and easy recycling and reuse.

Description

Technical Field

[0001] The present invention belongs to the field of MOF functional membranes, and in particular, relates to a metal organic framework fiber membrane and its application. Background Art

[0002] In recent years, environmental pollution has garnered widespread attention. Studies have shown that pesticide pollution is a major cause of environmental pollution, primarily due to its overuse. Organophosphorus pesticides (OPPs) are the most widely used pesticides in my country. Among them, chlorpyrifos is a highly effective, broad-spectrum organophosphorus insecticide. Long-term application can have long-term adverse effects on water bodies, and through continuous migration and transformation, it can ultimately harm human health through the food chain. Therefore, it is necessary to find appropriate methods to remove organophosphorus pesticides.

[0003] There are many methods for removing organophosphorus pesticides, primarily biological, chemical, catalytic, and adsorption. Biological methods are difficult to operate, require complex bacterial screening, and are significantly affected by environmental factors. Chemical methods for treating organophosphorus pollutants can achieve high removal efficiencies without causing secondary pollution, but they are relatively expensive. Of these methods, catalytic and adsorption are relatively simple and economical.

[0004] Metal-organic frameworks (MOFs), as an emerging porous material, have attracted widespread attention from scientists. MOFs are widely used for the adsorption and removal of organophosphorus pesticides due to their advantages, including high porosity, low density, large specific surface area, regular pore structure, adjustable pore size, diverse topological structures, and tailorability. Liu et al. successfully prepared a novel biomimetic metal-organic framework (Fe3O4-g-C3N4-PDA@MIL-101) with a high specific surface area, multi-microchannel structure, and strong thermochemical stability. This material has high adsorption efficiency and is an ideal adsorbent for removing organophosphorus pesticides from Chinese cabbage and green onion samples.

[0005] Since MOF itself is a powder structure, it has the following problems in practical applications:

[0006] (1) MOF is unstable in aqueous solution and its structure is prone to collapse. These disadvantages limit the application of MOF in water treatment. (2) Due to the large surface tension, the metal particles in MOF are prone to agglomeration, which leads to a significant decrease in the catalytic activity of MOF. (3) MOF is difficult to handle and recycle, which is not conducive to reuse.

[0007] Therefore, there is an urgent need to develop new MOF composites. Summary of the Invention

[0008] The present invention provides a metal-organic framework fiber membrane (MOF / PAN fiber membrane) for removing organophosphorus pesticides to address the aforementioned issues. The MOF / PAN fiber membrane prepared in this invention features a simple preparation method, low cost, good stability and removal efficiency, and is easily recyclable and reusable.

[0009] In order to achieve the above object, the present invention provides a metal organic framework fiber membrane, which is prepared by a method comprising the following steps:

[0010] Step 1: dissolving polyacrylonitrile, tetrakis(4-tetrazolylphenyl)ethylene and ethylene glycol dimethacrylate in a first organic solvent, and stirring overnight at room temperature to fully dissolve them to obtain a spinning solution;

[0011] Step 2: electrospinning the spinning solution. After spinning, the solution is placed in a vacuum dryer to obtain a PAN / H4TTPE membrane.

[0012] Step 3: Soak the PAN / H4TTPE film obtained in step 2 in a methanol solution containing azobisisoheptanonitrile and irradiate under ultraviolet light for cross-linking;

[0013] Step 4: Dissolve Cu(NO3)2·3H2O in a second organic solvent until fully dissolved to obtain solution B;

[0014] Step 5: Place Solution B and the cross-linked PAN / H4TTPE membrane in a reagent bottle, then add concentrated hydrochloric acid and shake slowly until the solution turns yellow-green;

[0015] Step 6: Seal the reagent bottle in step 5 with sealing film, heat and react. After the reaction is completed, wash the membrane and vacuum dry it to obtain a metal organic framework fiber membrane MOF / PAN.

[0016] According to a preferred embodiment of the present invention, in step 1, the molecular weight of the polyacrylonitrile is 100,000-200,000; the first organic solvent is N,N-dimethylformamide; relative to 1g of polyacrylonitrile, the amount of the tetrakis(4-tetrazolylphenyl)ethylene is 100-150mg, the amount of the ethylene glycol dimethacrylate is 0.5-1.5mL, and the amount of the first organic solvent is 6-10mL.

[0017] According to a preferred embodiment of the present invention, in step 2, the electrospinning conditions include: humidity of 30%-50%, voltage of 13-15KV, spinning rate of 0.8-1.2mL / h, and receiver speed of 190-210rpm; the vacuum drying conditions include: temperature of 30-60°C and time of 10-20 hours.

[0018] According to a preferred embodiment of the present invention, in step 3, based on the mass of H4TTPE in the PAN / H4TTPE film, the amount of the methanol solution of azobisisoheptanonitrile is 4-6 mL relative to 1 mg of H4TTPE in the PAN / H4TTPE film; the concentration of the methanol solution of azobisisoheptanonitrile is 0.1-0.3 g / 100 mL; the power of the ultraviolet lamp is 8-12 W, and the irradiation cross-linking time is 1-3 hours.

[0019] According to a preferred embodiment of the present invention, in step 4, the amount of the second organic solvent used is 20-40 mL relative to 1 g of Cu(NO3)2·3H2O; the second organic solvent is a mixed solution of equal volumes of DMF and ethanol.

[0020] According to a preferred embodiment of the present invention, in step 5, the amount of concentrated hydrochloric acid added is 10-20 μL relative to 1 mL of solution B.

[0021] According to a preferred embodiment of the present invention, in step 6, the temperature of the water bath reaction is 50-70°C and the time is 20-28 hours; the washing adopts ethanol and the washing times are 2-5 times; the conditions of the vacuum drying include: temperature 30-60°C and time 10-20 hours.

[0022] The metal organic framework fiber membrane of the present invention can be used to remove organophosphorus pesticides.

[0023] Electrospinning is a simple and effective method for producing fiber membranes, offering advantages such as ease of production, low cost, and process control. Furthermore, the resulting fiber membranes exhibit strong mechanical properties, large surface area, and high porosity, potentially complementing the shortcomings of MOFs.

[0024] The technical solution of the present invention has the following advantages:

[0025] 1. Simple preparation: MOF / PAN fiber membrane can be obtained by electrospinning first and then in situ growth.

[0026] 2. In situ growth does not require reaction under high temperature and high pressure, and the preparation process is relatively safe.

[0027] 3. Electrospinning is low-cost and can be applied on a large scale.

[0028] 4. In the process of preparing the spun fiber membrane, the cross-linking agent EGDMA is added and light-induced polymerization is used to make the spun fiber membrane resistant to the corrosion of organic solvents and improve the performance of the composite material.

[0029] 5. The material has a very good removal effect and can also achieve 100% removal effect on high concentration chlorpyrifos solution.

[0030] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings.

[0032] Figure 1 SEM images of PAN / H4TTPE spinning membrane (left) and MOF / PAN fiber membrane (right).

[0033] Figure 2 This is a high-resolution lens mapping image of the MOF / PAN fiber membrane prepared in Example 1.

[0034] Figure 3a This is a photo of the MOF / PAN fiber membrane prepared in Example 1.

[0035] Figure 3b This is a photograph of the MOF / PAN composite material prepared in Comparative Example 1 without adding EGDMA.

[0036] Figure 4 This is the removal effect of MOF / PAN fiber membrane on 10 μg / mL chlorpyrifos solution in different solvents.

[0037] Figure 5 The removal kinetics of 10 μg / mL chlorpyrifos solution by MOF / PAN fibers.

[0038] Figure 6 This is the removal effect of MOF / PAN fiber membrane on solutions with different concentrations of chlorpyrifos. DETAILED DESCRIPTION

[0039] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0040] Example 1

[0041] Preparation of MOF / PAN fiber membrane

[0042] Step 1: Dissolve 1 g of polyacrylonitrile (PAN, molecular weight 150,000), 120 mg of tetrakis(4-tetrazolylphenyl)ethylene (H4TTPE), and 2 mL of ethylene glycol dimethacrylate (EGDMA) in 8 mL of N,N-dimethylformamide (DMF) and stir overnight at room temperature to fully dissolve them to obtain solution A, which is the spinning solution.

[0043] Step 2: Solution A was electrospun at a humidity of 40%, a voltage of 13.5 kV, a spinning rate of 1.1 mL / h, and a receiver speed of 200 rpm. After spinning, the membrane was vacuum-dried at 40°C for 12 hours to obtain a PAN / H4TTPE membrane.

[0044] Step 3: Immerse one-twelfth of the PAN / H4TTPE membrane obtained in step 2 (the mass of H4TTPE contained is about 10 mg) in 50 mL of a methanol solution containing 0.1 g of azobisisoheptanenitrile and irradiate under a UV lamp (10 W) for 2 hours for crosslinking;

[0045] Step 4: Place the cross-linked PAN / H4TTPE membrane obtained in step 3 into a 100 mL blue-capped reagent bottle;

[0046] Step 5: Dissolve 0.36 g of Cu(NO3)2·3H2O in 10 mL of a mixture of DMF and ethanol (1:1, v:v) to obtain solution B.

[0047] Step 6: Pour solution B into the 100 mL blue-capped reagent bottle in step 4, then add 150 μL of concentrated hydrochloric acid and shake slowly until the solution turns yellow-green;

[0048] Step 7: Seal the 100 mL blue-capped reagent bottle in step 6 with sealing film and react in a water bath at 60°C for 24 hours. After the reaction, wash the membrane three times with ethanol and then vacuum dry it at 60°C for 12 hours to obtain a MOF / PAN fiber membrane.

[0049] SEM characterization of PAN / H4TTPE spinning membrane and MOF / PAN fiber membrane was carried out. Figure 1 Scanning electron microscope images and Figure 2 High-resolution lens mapping images show that MOF was grown in situ on the PAN / H4TTPE spinning membrane, and MOF-spun fiber membrane was successfully synthesized. Figure 3a This is a photo of MOF / PAN fiber membrane.

[0050] Comparative Example 1

[0051] The fiber membrane was prepared according to the method of Example 1, except that EGDMA was not added during the preparation process. Figure 3bAs shown in the figure, it can be seen that almost no MOF is generated on the surface of the spun fiber membrane, or very little MOF is grown, and the fiber membrane is obviously thinner (compared to Figure 3a ), it is possible that part of the membrane is dissolved by the organic solvent, resulting in the inability to grow MOF materials in situ on the fiber membrane.

[0052] Example 2

[0053] Removal of 10 μg / mL chlorpyrifos solution by MOF / PAN fiber membrane in different solvents.

[0054] Step 1: Prepare solvents with different ratios of water and methanol according to the table below.

[0055] Water and methanol ratio Amount of water added (mL) Amount of methanol added (mL) Solvent volume (mL) Water:methanol=5:1 10 2 12 Water:methanol=2:1 8 4 12 Water:methanol=1:1 6 6 12 Water:methanol=1:2 4 8 12 Water:methanol=1:5 2 10 12 Water:methanol=1:10 1 10 11

[0056] Step 2: Prepare 5 mL of 10 μg / mL chlorpyrifos solution using different solvents;

[0057] Step 3: 5 mg of MOF / PAN fiber membrane was immersed in 1 mL of 10 μg / mL chlorpyrifos solution prepared in different solvents and shaken on a horizontal shaker at 85 rpm in the dark for 1 hour;

[0058] Step 4: After step 3, the supernatant after the reaction was filtered through a 0.22 μm filter membrane (nylon 66) to obtain the test solution;

[0059] Step 5: The test solution obtained in step 4 is quantitatively determined by HPLC (high performance liquid chromatography). The minimum detection limit of the HPLC method is 250 ng / mL.

[0060] The calculation formula for the removal rate is:

[0061] (where C0 is the initial concentration of chlorpyrifos, C t is the concentration of the chlorpyrifos supernatant after the reaction)

[0062] The removal effect of MOF / PAN fiber membrane on 10 μg / mL chlorpyrifos solution in different solvents is shown in Figure 2. Figure 4 As shown in the figure, the MOF / PAN fiber membrane demonstrated high removal efficiency for a 10 μg / mL chlorpyrifos solution in various solvents. The highest removal rate, reaching 100%, was achieved in a 1:10 water:methanol mixture. Therefore, a 1:10 water:methanol mixture was ultimately selected as the solvent for the MOF / PAN fiber membrane to remove chlorpyrifos.

[0063] Example 3 Removal kinetics of 10 μg / mL chlorpyrifos solution by MOF / PAN fiber membrane

[0064] Step 1: Prepare a 10 μg / mL chlorpyrifos solution using a mixture of water and methanol in a ratio of 1:10 as solvent;

[0065] Step 2: Immerse 5 mg of MOF / PAN fiber membrane in 1 mL of a 10 μg / mL chlorpyrifos solution. Shake the sample in the dark on an 85 rpm horizontal shaker for different time periods (0, 1, 2, 5, 10, 15, 20, 30, and 40 min). The blank control is 0, in which no MOF / PAN fiber membrane is added.

[0066] Step 3: When each sample reaches the set time, remove it from the horizontal shaker, aspirate the supernatant, and filter it with a 0.22 μm filter membrane (nylon 66) to obtain the test solution;

[0067] Step 4: The test solution obtained in step 3 is quantitatively determined by HPLC (high performance liquid chromatography).

[0068] The results are as follows Figure 5 As shown, it can be seen that the MOF / PAN fiber membrane has a fast removal rate for 10 μg / mL chlorpyrifos solution, and can reach 100% removal in 5 minutes.

[0069] Example 4 Removal of chlorpyrifos solutions of different concentrations by MOF / PAN fiber membrane

[0070] Step 1: Using a mixture of water and methanol (1:10) as solvent, prepare 5 μg / mL, 10 μg / mL, 20 μg / mL, 40 μg / mL, 80 μg / mL, 160 μg / mL, and 320 μg / mL chlorpyrifos solutions by gradient dilution method;

[0071] Step 2: 5 mg of MOF / PAN fiber membrane was immersed in 1 mL of the above-mentioned chlorpyrifos solution with different concentrations, and shaken in the dark on a horizontal shaker at 85 rpm for 15 minutes;

[0072] Step 3: After step 2, the supernatant was aspirated and filtered through a 0.22 μm filter membrane (nylon 66) to obtain the test solution;

[0073] Step 4: The test solution obtained in step 3 is quantitatively determined by HPLC (high performance liquid chromatography).

[0074] The results are as follows Figure 6 As shown in the figure, it can be seen that the MOF / PAN fiber membrane has a high removal effect on chlorpyrifos solutions with different concentrations, indicating that the MOF / PAN fiber membrane has good removal performance.

[0075] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A metal organic framework fiber membrane, wherein the metal organic framework fiber membrane is prepared by a method comprising the following steps: Step 1: dissolving polyacrylonitrile, tetrakis(4-tetrazolylphenyl)ethylene and ethylene glycol dimethacrylate in a first organic solvent, and stirring overnight at room temperature to fully dissolve them to obtain a spinning solution; Step 2: electrospinning the spinning solution. After spinning, the solution is placed in a vacuum dryer to obtain a PAN / H4TTPE membrane. Step 3: Soak the PAN / H4TTPE film obtained in step 2 in a methanol solution containing azobisisoheptanonitrile and irradiate under ultraviolet light for cross-linking; Step 4: Dissolve Cu(NO3)2·3H2O in a second organic solvent until fully dissolved to obtain solution B; Step 5: Place Solution B and the cross-linked PAN / H4TTPE membrane in a reagent bottle, then add concentrated hydrochloric acid and shake slowly until the solution turns yellow-green; Step 6: Seal the reagent bottle in step 5 with a sealing film, heat and react, and after the reaction is completed, wash the membrane and vacuum dry it to obtain a metal organic framework fiber membrane.

2. The metal organic framework fiber membrane according to claim 1, wherein In step 1, The molecular weight of the polyacrylonitrile is 100,000-200,000; The first organic solvent is N,N-dimethylformamide; Relative to 1 g of polyacrylonitrile, the amount of tetrakis(4-tetrazolylphenyl)ethylene is 100-150 mg, the amount of ethylene glycol dimethacrylate is 0.5-1.5 mL, and the amount of the first organic solvent is 6-10 mL.

3. The metal organic framework fiber membrane according to claim 1, wherein: In step 2, The electrospinning conditions include: humidity of 30%-50%, voltage of 13-15V, spinning rate of 0.8-1.2mL / h, and receiver speed of 190-210rpm; The vacuum drying conditions include: a temperature of 30-60° C. and a time of 10-20 hours.

4. The metal organic framework fiber membrane according to claim 1, wherein In step 3, Based on the mass of H4TTPE in the PAN / H4TTPE film, the amount of the methanol solution of azobisisoheptanenitrile used is 4-6 mL relative to 1 mg of H4TTPE in the PAN / H4TTPE film; The concentration of the methanol solution of azobisisoheptanonitrile is 0.1-0.3 g / 100 mL; The power of the ultraviolet lamp is 8-12W, and the irradiation and cross-linking time is 1-3 hours.

5. The metal organic framework fiber membrane according to claim 1, wherein In step 4, The amount of the second organic solvent used is 20-40 mL relative to 1 g of Cu(NO3)2·3H2O; The second organic solvent is a mixed solution of DMF and ethanol in equal volumes.

6. The metal organic framework fiber membrane according to claim 1, wherein: In step 5, the amount of concentrated hydrochloric acid added is 10-20 μL relative to 1 mL of solution B.

7. The metal organic framework fiber membrane according to claim 1, wherein: In step 6, the washing is performed with ethanol for 2-5 times; The vacuum drying conditions include: a temperature of 30-60° C. and a time of 10-20 hours.

8. Use of the metal organic framework fiber membrane according to any one of claims 1 to 7 in removing organophosphorus pesticides.

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