Silicone rubber / mof vertical array hollow fiber composite membrane, and preparation method and application thereof

Abstract

The application discloses a kind of silicon rubber / MOF vertical array hollow fiber composite membrane and preparation method and application thereof, hollow fiber membrane is packaged and made tube-shell type membrane module, first evenly distributed ZIF-8 seed crystal is prepared in PVDF hollow fiber membrane outer or inner surface;Then ZnO precursor solution is injected into membrane module shell side or tube side, and PVDF hollow fiber membrane module of ZnO microrod array growth is obtained by hydrothermal synthesis.Afterwards ligand solution is injected into membrane module shell side or tube side, and the membrane module of ZIF-8@ZnO composite microrod array growth in PVDF hollow fiber membrane outer or inner surface is obtained by solvothermal synthesis;Silicon rubber solution is injected into membrane module shell side or tube side, and silicon rubber / MOF vertical array hollow fiber composite membrane is obtained by drying crosslinking after.The application successfully constructs hollow fiber composite membrane with MOF directional molecular transfer channel in flexible hollow fiber membrane outer or inner surface, realizes the directional transfer of guest molecules in membrane, strengthens the mass transfer process of PV membrane separation, and significantly improves ethanol / water separation performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of membrane separation technology, in particular to a kind of silicon rubber / MOF vertical array hollow fiber composite membrane and its preparation method and application. BACKGROUND

[0002] Overuse of fossil fuels such as coal, oil, and natural gas can cause global warming, environmental pollution, and energy crisis. Bioethanol can be used as a clean energy alternative to fossil fuels due to its renewable, high calorific value, and environmental friendliness, etc. It can serve our country's energy conservation and emission reduction. Separating bioethanol from fermentation broth can effectively improve the production efficiency of fermentation ethanol. Pervaporation (PV) membrane separation technology has attracted widespread attention due to its low energy consumption, high efficiency, and harmlessness to microorganisms. As the core of the PV separation process, the preparation of high-performance PV membranes is crucial. Polymer hollow fiber membranes have become one of the most important membrane types in industrial applications due to their large packing density and effective area, as well as strong self-supporting properties. Therefore, it is of great scientific value and potential application value to prepare high-performance PV membranes on the surface of polymer hollow fiber membranes. The currently widely used polymer membranes are generally subject to the "trade-off effect" between permeability and selectivity, which makes the separation performance of polymer membranes unsatisfactory.

[0003] MOFs are a new type of porous crystalline material, which has been widely used in gas separation, catalysis, and energy storage due to its large specific surface area, pore structure, and strong adsorption capacity. In recent years, researchers have prepared continuous defect-free MOF-based membranes on the surface of hollow fiber membranes to improve the separation performance of the membranes. Wang et al. prepared ZIF-8 membranes on the surface of polypropylene hollow fiber membranes by rapid current-driven synthesis. The prepared ZIF-8 membranes have excellent separation performance for C3H6 / C3H8 binary mixtures. After bending the ZIF-8 membranes, the separation performance of the ZIF-8 membranes remains unchanged (J. Am. Chem. Soc. 2020, 142, 50, 20915-20919). Hou et al. used dip-coating technology to prepare continuous flexible ZIF-8 membranes on the surface of titanium-functionalized polymer hollow fiber membranes, which have good H2 / CO2 separation selectivity (Angew. Chem. Int. Ed. 2016, 55, 3947-3951). These studies have actively promoted the application of MOF-based separation membranes in the field of gas separation. Patent CN202311699790.2 discloses a method for preparing continuous MOF polycrystal-based membranes on the inner surface of polymer hollow fiber membranes by passing metal salt solution and organic ligand solution into the hollow fiber membrane module. The prepared silicon rubber / MOF hollow fiber composite membrane is used for ethanol / water separation after being coated with silicon rubber. However, the existing technology still has limitations in improving the ethanol / water separation performance, and it is of great significance to further improve the separation performance of ethanol / water. SUMMARY

[0004] To solve the above technical problems, the present application provides a kind of silicon rubber / MOF vertical array hollow fiber composite membrane and its preparation method and for efficient PV separation ethanol / water solution.

[0005] Specifically, the present application is realized by the following scheme:

[0006] A kind of preparation method of silicon rubber / MOF vertical array hollow fiber composite membrane, comprising the following steps:

[0007] 1) polymeric hollow fiber membrane is packed and glued in tube, after natural solidification at room temperature, polymeric hollow fiber membrane assembly is obtained, the space inside polymeric hollow fiber membrane is membrane assembly tube, the space between polymeric hollow fiber membrane and membrane assembly shell is membrane assembly shell;

[0008] 2) MOF precursor solution is injected into the shell side or tube side of the methanol wetted membrane module, after standing, the excess MOF precursor solution in the module is removed, and then placed in an oven for self-crystallization to obtain a polymeric hollow fiber membrane module containing MOF seeds;

[0009] 3) metal oxide precursor solution is injected into the shell side or tube side of the membrane module and the ports of the shell side or tube side of the membrane module are sealed, and the membrane module is moved to an oven for reaction; after the reaction is completed, the solution in the shell side or tube side of the membrane module is poured out and cleaned, and the membrane module is placed in an oven for drying to obtain a membrane module with metal oxide rod array grown on the outer or inner surface of the polymeric hollow fiber membrane;

[0010] 4) MOF organic ligand solution is injected into the shell side or tube side of the membrane module, the membrane module is moved to an oven for reaction, and after the reaction is completed, the unreacted organic ligand is removed by cleaning, and then the membrane module is moved to an oven for drying to obtain a membrane module with MOF / metal oxide rod array grown on the outer or inner surface of the polymeric hollow fiber membrane;

[0011] 5) silicon rubber mixed solution is injected into the shell side or tube side of the membrane module, after standing, the membrane module is placed in an oven for crosslinking and curing to obtain the silicon rubber / MOF vertical array hollow fiber composite membrane.

[0012] Further, in step 1), epoxy resin or 704 silicone rubber is used for sealing.

[0013] Further, the hollow fiber membrane is a microfiltration membrane, an ultrafiltration membrane or a nanofiltration membrane; the polymer in the polymeric hollow fiber membrane is polyvinylidene fluoride, polytetrafluoroethylene, polysulfone, polyethersulfone, polyethylene, polypropylene or polyacrylonitrile.

[0014] Further, the MOF organic ligand solution is a mixed solution containing MOF organic ligand and solvent.

[0015] Further, the solvent is a mixed solvent of water and N,N-dimethylformamide in a volume ratio of 1:1-8. Preferably, the volume ratio of water and N,N-dimethylformamide is 1:2-4.

[0016] Further, the MOF precursor solution is an aqueous solution containing metal ions and MOF organic ligands.

[0017] Further, the metal ions and the metal in the metal oxide are both zinc or cobalt; the MOF organic ligand is dimethylimidazole or 4,5-dichloroimidazole.

[0018] Further, the silicone rubber mixed solution is obtained by dissolving silicone rubber, a crosslinking agent and a catalyst in an organic solvent.

[0019] Further, the silicone rubber is polydimethylsiloxane (PDMS), polymethylphenylsiloxane (PMPS) or polymethyloctylsiloxane (POMS); the crosslinking agent is tetraethyl orthosilicate (TEOS), phenyltrimethoxysilane (PTMOS), octyltrimethoxysilane (OTMOS) or γ-aminopropyltriethoxysilane (APTEOS); the catalyst is dibutyltin dilaurate (DBTDL) or di-n-octyltin dilaurate (DOTDL); and the organic solvent is n-heptane, n-hexane or n-pentane.

[0020] Further, the mass ratio of the organic solvent, the silicone rubber, the crosslinking agent and the catalyst is 100-1000:0.5-5:0.1-1:0.02-0.2.

[0021] Further, in step 2), the membrane module wetted with methanol is obtained by injecting methanol into the shell side of the membrane module, standing for 10-60 min, and then removing the excess methanol in the module to obtain a membrane module in which the polymeric hollow fiber membranes are wetted with methanol.

[0022] Further, in step 2), specifically: according to the ratio of 0.1-2 g of zinc nitrate hexahydrate or zinc acetate or cobalt nitrate hexahydrate corresponding to every 10 mL of deionized water, zinc nitrate hexahydrate or zinc acetate or cobalt nitrate hexahydrate is added to deionized water to obtain solution 1; according to the ratio of 1-10 g of dimethylimidazole or 4,5-dichloroimidazole corresponding to every 100 mL of deionized water, dimethylimidazole or 4,5-dichloroimidazole is added to deionized water, and stirred at 100-300 rpm for 10-60 min to obtain solution 2. Solution 1 is added to solution 2, and stirred at 100-300 rpm for 10-60 min to obtain a MOF precursor solution. The obtained MOF precursor solution is injected into the shell side of the hollow fiber membrane module assembly wetted by methanol, and after standing for 10-60 min, the excess MOF precursor solution in the module is removed, and then the membrane module is placed in an oven at 40-60°C for self-crystallization for 0.5-2 h to obtain a polymer hollow fiber membrane module containing MOF seeds.

[0023] Further, in step 3), specifically: according to the ratio of 1-5 g of zinc nitrate hexahydrate or zinc acetate or cobalt nitrate hexahydrate corresponding to every 25 mL of deionized water, zinc nitrate hexahydrate or zinc acetate or cobalt nitrate hexahydrate is added to deionized water, and stirred at room temperature for 10-30 min to fully dissolve to obtain solution 3; according to the ratio of 2-6 g of sodium hydroxide or ammonia water corresponding to every 25 mL of deionized water, sodium hydroxide or ammonia water is added to deionized water, and stirred at room temperature for 10-30 min to fully dissolve to obtain solution 4; solution 3 is added to solution 4, and stirred at room temperature for 10-30 min to obtain a metal oxide precursor solution; wherein the volume ratio of solution 3 to solution 4 is 1:0.5-2; the metal oxide precursor solution is injected into the shell side of the membrane module obtained in step 2) and the shell side port of the membrane module is sealed; then the sealed membrane module is subjected to hydrothermal reaction at 40-100°C for 6-24 h, the solution in the post-reaction membrane module is discharged, and after ethanol washing and drying, a membrane module with metal oxide rod-like arrays grown on the surface of the polymer hollow fiber membrane is obtained.

[0024] Further, in step 4), specifically: according to the ratio of 0.5-3 g of dimethylimidazole or 4,5-dichloroimidazole corresponding to every 3.6 mL of a mixed solution of deionized water and N,N-dimethylformamide in a volume ratio of 1-4:1-8, dimethylimidazole or 4,5-dichloroimidazole is added to the mixed solution of deionized water and N,N-dimethylformamide in a volume ratio of 1:1-8, and stirred at room temperature for 20 min to obtain a MOF organic ligand solution; the MOF organic ligand solution is injected into the shell side of the membrane module obtained in step 3), and after sealing the membrane module and reacting at 50-100°C for 3-18 h, the solution in the post-reaction membrane module is discharged, and after methanol washing and drying, a membrane module with MOF / metal oxide rod-like arrays grown on the surface of the polymer hollow fiber membrane is obtained.

[0025] Further, in step 5), specifically: adding silicone rubber, crosslinking agent and catalyst into organic solvent, stirring for 1-3h to obtain silicone rubber mixed solution, injecting the silicone rubber mixed solution into the shell side of the membrane module obtained in step 4), standing for 0.5-10min, removing the solution in the shell side, and heat crosslinking at 60-120℃ for 4-12h to obtain the silicone rubber / MOF vertical array hollow fiber composite membrane.

[0026] The application also provides a silicone rubber / MOF vertical array hollow fiber composite membrane prepared by the above preparation method.

[0027] The application also provides application of the silicone rubber / MOF vertical array hollow fiber composite membrane in ethanol / water separation.

[0028] Beneficial effects:

[0029] 1. The application successfully solves the problems of membrane failure or non-uniformity of the separation layer caused by the gravity of the casting solution during the preparation of the separation layer by the coating method, by constructing the MOF functional layer on the surface of the polymer hollow fiber membrane and then modifying the polymer to prepare the polymer / MOF composite separation membrane, thereby providing a new idea for the uniform preparation of the polymer / MOF hollow fiber separation membrane.

[0030] 2. The application successfully constructs the MOF vertical directional molecular transfer channel on the surface of the polymer hollow fiber membrane by using the metal oxide rod, especially the ZnO rod, as a sacrificial template, without the need of additional Zn source, realizes the directional and rapid transfer of the guest molecules in the membrane during the PV separation process, strengthens the mass transfer process of the molecules in the membrane, and improves the membrane permeability.

[0031] 3. The micro-nano structure of the MOF / metal oxide composite rod on the surface of the membrane and the simple coating process repair the defects of the ZIF-8 layer without changing the array structure. The prepared silicone rubber / MOF vertical array composite membrane presents superhydrophobicity, effectively reduces the permeation of water molecules in the membrane, and improves the separation selectivity of the membrane.

[0032] 4. The unique array structure on the surface of the silicone rubber / MOF hollow fiber composite membrane prepared by the application increases the actual separation area of the membrane, and effectively improves the separation capacity of the polymer / MOF array composite membrane. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is the transmission electron microscope image of the composite rod in the array structure on the surface of the membrane in Example 1 of the application.

[0034] Figure 2 It is the surface and cross-section SEM image of the silicone rubber / MOF vertical array hollow fiber composite membrane obtained in Example 1 of the application.

[0035] Figure 3 SEM images of the cross-section of the silicone hollow fiber composite membrane obtained in Inventive Example 1.

[0036] Figure 4 SEM images of the surface and cross-section of the MOF vertical array hollow fiber composite membrane obtained in Inventive Example 2.

[0037] Figure 5 SEM images of the cross-section of the ZIF-8@ZnO / PVDF array membrane obtained in Inventive Example 1, Inventive Example 2, Comparative Example 3 and Comparative Example 4 without step 5) treatment.

[0038] Figure 6 Graph of the separation performance comparison results of Inventive Example 1 and Comparative Examples 1 and 2.

[0039] Figure 7 Graph of the separation performance comparison results of Inventive Examples 1 and 2 and Comparative Examples 3 and 4. DETAILED DESCRIPTION

[0040] The content of the present application will be further described below in combination with the drawings, examples and comparative examples, but the scope of the present application claimed is not limited only to the following examples.

[0041] Example 1:

[0042] A preparation method of a silicone / MOF vertical array hollow fiber composite membrane, the specific steps are as follows:

[0043] 1) Five PVDF hollow fiber membranes (inner diameter, 750 μm; outer diameter, 1200 μm; porosity, 67.4%) were packed in a glass tube, and 704 silicone rubber was used for packaging, and dried at room temperature for 48 h to obtain a hollow fiber membrane module.

[0044] 2) Methanol was injected into the shell side of the membrane module, and stood for 20 min, and then the excess methanol in the module was removed to obtain a PVDF membrane wetted hollow fiber membrane module. 0.5948 g of zinc nitrate hexahydrate was added to 10 mL of deionized water to obtain solution 1. 8.2 g of dimethylimidazole was added to 500 mL of deionized water, and stirred at 300 rpm for 30 min to obtain solution 2. Solution 1 was added to solution 2, and stirred at 230 rpm for 15 min to obtain a MOF precursor solution. The obtained MOF precursor solution was injected into the shell side of the methanol wetted hollow fiber membrane module, and after standing for 30 min, the excess MOF precursor solution in the module was removed, and then the membrane module was placed in a 50°C oven for self-crystallization for 1 h to obtain a PVDF hollow fiber membrane module containing MOF seeds.

[0045] 3) 0.4 mol·L-1 Zn(NO3)2·6H2O and 4 mol·L -1 of NaOH aqueous solution, then 25 mL of NaOH aqueous solution was slowly added into the same volume of Zn(NO3)2·6H2O aqueous solution, stirred for 20 min until the solution was transparent, to obtain a ZnO precursor solution. The ZnO precursor solution was injected into the shell side of the PVDF hollow fiber membrane module loaded with MOF crystal seeds described above and the shell side port was sealed, and the module was moved into a 60°C oven for reaction for 18 h. After the reaction was completed, the solution in the shell side of the membrane module was poured out and washed with ethanol for 3 times, and dried in a 60°C oven for 6 h to obtain a ZnO microrod array grown on the surface of the PVDF hollow fiber membrane.

[0046] 4) 0.1478 g of dimethylimidazole was added into a mixed solution of H2O and DMF with a volume ratio of 1:4, and stirred for 20 min until the dimethylimidazole was completely dissolved to prepare a dimethylimidazole solution with a concentration of 0.1 mol·L -1 of dimethylimidazole was then injected into the shell side of the ZnO / PVDF array membrane module obtained above, and moved into a 70°C oven for reaction for 10 h. After the reaction was completed, the unreacted dimethylimidazole was removed by washing with methanol for 3 times. Then the module was moved into a 100°C oven for drying to obtain a ZIF-8@ZnO / PVDF array membrane (as shown in Figure 1 and Figure 5 (a)).

[0047] 5) 0.2 g of PMPS was added into 19.8 mL of n-heptane, and stirred at 300 rpm for 20 min. Then, 0.04 g of TEOS and 0.008 g of DBTDL were added into the above solution, and stirred at 300 rpm for 20 min. The solution was injected into the shell side of the ZIF-8@ZnO / PVDF array membrane module, and after standing for 5 min, the membrane module was placed into an 80°C oven for cross-linking and curing for 4 h to obtain a PMPS-ZIF-8@ZnO / PVDF array membrane (as shown in Figure 2 , wherein Figure 2 (a) and Figure 2 (b) are surface SEM images, Figure 2 (c) is a cross-sectional SEM image).

[0048] Example 2:

[0049] The difference from Example 1 is only that:

[0050] In step 4), a mixed solution of H2O and DMF with a volume ratio of 1:2 was selected (the product obtained after step 4) is as shown in Figure 5 (b)).

[0051] Comparative Example 1:

[0052] The difference from Example 1 is only that:

[0053] The operations of Example 1 Step 2), Step 3) and Step 4) are not performed, to obtain a PDMS / PVDF hollow fiber membrane (as shown in Figure 3 ).

[0054] Comparative Example 2:

[0055] The difference from Example 1 is only that:

[0056] The operation of Example 1 Step 5) is not performed, to obtain a ZIF-8@ZnO / PVDF array membrane (as shown in Figure 4 , wherein, Figure 4 (a) and Figure 4 (b) are surface SEM images, Figure 4 (c) and Figure 4 (d) are cross-sectional SEM images.

[0057] Comparative Example 3:

[0058] The difference from Example 1 is only that:

[0059] In Step 4), a mixed solution of H2O and DMF with a volume ratio of 2:1 is selected (the product obtained after Step 4) is as shown in Figure 5 (c).

[0060] Comparative Example 4:

[0061] The difference from Example 1 is only that:

[0062] In Step 4), a mixed solution of H2O and DMF with a volume ratio of 4:1 is selected (the product obtained after Step 4) is as shown in Figure 5 (d).

[0063] The hollow fiber composite membrane assemblies obtained in each example and comparative example are verified for molecular separation performance by separating and recovering ethanol in an ethanol aqueous solution, and the specific test standards are as follows:

[0064] The effective area of the membrane used for testing is 15 cm 2 , the raw material liquid is 5wt% ethanol aqueous solution, the raw material liquid circulation flow rate is 0.5m / s, and the test system temperature is maintained at 40℃. A vacuum pump is used to maintain the permeation pressure below 100Pa, and the collector is immersed in liquid nitrogen to collect the permeation vapor. Then the composition of the raw material liquid and the permeation liquid is tested by GC-7890II gas chromatograph (China Tianmei Scientific Instrument Co., Ltd.), and each membrane assembly is measured at least three times. The total permeation flux (J, g.m -2 .h -1 ) and the separation factor (β) are calculated according to the following equations:

[0065]

[0066] J i =J×m i (3)

[0067] Where W(g) is the total mass of permeate collected within t hours, and A(m) is the total mass of permeate collected within t hours. 2 (m) represents the effective area of ​​the membrane. f and m p These are the ethanol concentrations (wt%) on the feed side and the permeate side, respectively.

[0068] The comparison results of the separation performance of hollow fiber composite membrane modules obtained from each embodiment and control example are as follows: Figure 6 and Figure 7 As shown. By Figure 6 It can be seen that the ethanol permeation flux and separation factor of the silicone rubber / MOF vertical array hollow fiber composite membrane in Example 1 reached 2 kg / m. -2 .h -1 And 10.5. The separation performance is much higher than that of the silicone rubber hollow fiber composite membrane (0.58 kg·m) prepared in Control Example 1. -2 .h -1 (7.9). Thanks to the construction of vertically oriented molecular transport channels within the membrane using MOF and the reduction of boundary layer resistance during separation by the membrane surface array structure, the "trade-off effect" between permeability and selectivity of pure silicone rubber membranes was broken, achieving a simultaneous improvement in membrane permeability and selectivity. The ethanol permeation flux of the MOF vertical array hollow fiber composite membrane prepared in Comparative Example 2 reached 1.65 kg / m. -2 .h -1 The separation factor was 6.3. This indicates that the MOF layer, acting as a vertically oriented molecular transport channel within the membrane, has a certain separation effect on the separation of ethanol and aqueous solutions by PV. After coating with the silicone rubber matrix in Example 1, the membrane's separation performance was significantly improved; its ethanol permeation flux was 1.1 times that of the MOF vertical array hollow fiber composite membrane prepared in Control Example 2, its water permeation flux was 0.7 times that of the MOF vertical array hollow fiber composite membrane prepared in Control Example 2, and its separation factor was 1.4 times that of the MOF vertical array hollow fiber composite membrane prepared in Control Example 2. This indicates that the coating with the silicone rubber matrix significantly increased the membrane surface dissolution selectivity, increased the permeation of ethanol molecules, hindered the permeation of water molecules, and enhanced the membrane separation performance.

[0069] like Figure 7 As shown, the ethanol permeation flux and separation factor of the silicone rubber / MOF vertical array hollow fiber composite membrane obtained in Example 2 reached 1.88 kg / m. -2 .h -1and 10.5. The ethanol flux of the composite membrane obtained in Example 1 was 0.9 times that of the silicone rubber / MOF vertical array hollow fiber composite membrane obtained in Comparative Example 3, and the separation factor remained stable. The ethanol permeation flux and separation factor of the silicone rubber / MOF vertical array hollow fiber composite membrane obtained in Comparative Example 4 were 1.58 kg.m -2 .h -1 and 10.6. The ethanol permeation flux of the silicone rubber / MOF vertical array hollow fiber composite membrane obtained in Comparative Example 4 was reduced to 1.32 kg.m -2 .h -1 and the separation factor was 10.8. The ethanol permeation flux of the silicone rubber / MOF vertical array hollow fiber composite membrane obtained in Example 1 was 1.5 times that of the silicone rubber / MOF vertical array hollow fiber composite membrane obtained in Comparative Example 3. According to the above results, it can be seen that, as the H2O / DMF volume ratio increased, the dissolution rate of the ZnO microrod increased, ZIF-8 gradually formed in the ligand solution between the ZnO microrods, and the microrod array structure disappeared, forming a continuous ZIF-8 layer on the surface of the membrane. The thicker ZIF-8 layer increased the mass transfer resistance of the guest molecules in the membrane, and the non-directional molecular channels caused uncertainty in the transfer of the guest molecules in the membrane, increased the molecular transfer path, and thus reduced the permeation of ethanol and water molecules. In addition, the disappearance of the microrod array structure caused the effective separation area on the surface of the membrane to decrease, reducing the fluxes of water and ethanol. Because the reduction in the ethanol flux was less than the reduction in the water flux, the separation factor of the membrane slowly increased. Figure 5

[0070] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application.​

Claims

1. A method for preparing a silicone rubber / MOF vertical array hollow fiber composite membrane, characterized in that, Includes the following steps: 1) The polymer hollow fiber membrane is filled and sealed in the tube. After natural curing at room temperature, a polymer hollow fiber membrane module is obtained. The internal space of the polymer hollow fiber membrane is the tube side of the membrane module, and the space between the polymer hollow fiber membrane and the outer shell of the membrane module is the shell side of the membrane module. 2) Inject the MOF precursor solution into the shell side or tube side of the membrane module wetted with methanol. After standing, remove the excess MOF precursor solution in the module and then place it in an oven for self-crystallization to obtain a polymer hollow fiber membrane module containing MOF seeds. 3) Inject the metal oxide precursor solution into the shell side or tube side of the membrane module and seal the shell side or tube side ports of the membrane module, then transfer it to an oven for reaction; after the reaction is completed, pour out the solution in the shell side or tube side of the membrane module and wash it, then put it in an oven to dry, and obtain a membrane module with a metal oxide rod array grown on the surface of the polymer hollow fiber membrane. 4) Inject the MOF organic ligand solution into the shell side or tube side of the membrane module, transfer it to an oven for reaction, and after the reaction is complete, wash to remove unreacted organic ligands, and then transfer it to an oven for drying to obtain a membrane module with MOF / metal oxide rod arrays grown on the outer or inner surface of the polymer hollow fiber membrane. 5) Inject the silicone rubber mixture into the shell side or tube side of the membrane module, let it stand, and then place the membrane module in an oven for cross-linking and curing to obtain the silicone rubber / MOF vertical array hollow fiber composite membrane. The MOF organic ligand solution is a mixed solution containing MOF organic ligands and solvents; The solvent is a mixture of water and N,N-dimethylformamide in a volume ratio of 1:1 to 8.

2. The preparation method according to claim 1, characterized in that, The hollow fiber membrane is a microfiltration membrane, ultrafiltration membrane, or nanofiltration membrane; the polymer in the polymer hollow fiber membrane is polyvinylidene fluoride, polytetrafluoroethylene, polysulfone, polyethersulfone, polyethylene, polypropylene, or polyacrylonitrile.

3. The preparation method according to claim 1, characterized in that, The MOF precursor solution is an aqueous solution containing metal ions and MOF organic ligands.

4. The preparation method according to claim 3, characterized in that, The metal ion and the metal oxide are both zinc or cobalt; the MOF organic ligand is dimethylimidazole or 4,5-dichloroimidazole.

5. The preparation method according to claim 1, characterized in that, The silicone rubber mixture is obtained by dissolving silicone rubber, crosslinking agent, and catalyst in an organic solvent.

6. The preparation method according to claim 5, characterized in that, The silicone rubber is polydimethoxysiloxane, polymethylphenylsiloxane, or polymethyloctylsiloxane; the crosslinking agent is tetraethyl orthosilicate, phenyltrimethoxysilane, octyltrimethoxysilane, or γ-aminopropyltriethoxysilane; the catalyst is dibutyltin dilaurate or dioctyltin dilaurate; and the organic solvent is n-heptane, n-hexane, or n-pentane.

7. A silicone rubber / MOF vertical array hollow fiber composite membrane, characterized in that, Prepared by the preparation method according to any one of claims 1-6.

8. The application of the silicone rubber / MOF vertical array hollow fiber composite membrane according to claim 7 in ethanol / water separation.

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