Preparation method and application of thiolated Mg-MOF-74 polysulfone composite membrane

Abstract

The invention discloses a preparation method and application of a sulfhydrylated Mg-MOF-74 polysulfone composite membrane. The preparation method comprises the following steps: introducing a hydrophilic polymer into a polysulfone base material through a free radical polymerization method, and carrying out non-solvent induced phase separation to obtain a modified polysulfone membrane; the preparation method comprises the following steps: modifying Mg-MOF-74 nano particles by using a silane coupling agent containing a sulfydryl group, so as to obtain sulfhydrylated Mg-MOF-74; and modifying the P-PSF membrane by using the sulfhydrylated Mg-MOF-74 nanoparticles to construct a surface micro-nano coarse structure, and finally obtaining the sulfhydrylated Mg-MOF-74 polysulfone composite membrane with oil-water separation and heavy metal ion adsorption functions. According to the preparation method disclosed by the invention, a silane coupling agent containing a sulfydryl group and hydroxyl on the surface of the Mg-MOF-74 are creatively coupled to obtain the sulfhydrylated Mg-MOF-74, and the sulfhydrylated Mg-MOF-74 has a wide application value in the fields of oily sewage treatment, heavy metal ion adsorption and the like.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials and functional materials, and specifically designs an application of a thiolated Mg-MOF-74 polysulfone composite membrane in heavy metal adsorption and oil-water separation. Background Art

[0002] The rapid advancement of economic development and industrialization has brought many conveniences to human life, but it has also caused increasingly serious problems such as ecological and water pollution. 2+ , Pb 2+ , Cu 2+ etc.) are widely discharged into the water, posing a huge threat to the ecosystem and human health. Although traditional oil-water treatment technologies (mechanical, chemical, membrane separation, gravity separation) can provide solutions for some oil-water separation, they are inefficient, prone to secondary pollution, and can cause difficult-to-handle complex heavy metal residues and oil-water emulsion problems. There are many studies on membrane separation technology, but its high price, inability to effectively separate heavy metal ions, and easy pore clogging have greatly limited its application in the field of oil-water separation. Therefore, it is of great significance to design and prepare a new oil-water separation membrane that is economical, efficient, and can adsorb heavy metal ions.

[0003] Metal-organic frameworks (MOFs) have rapidly gained popularity in recent years. MOFs, with their unique porous structure, tunable chemical properties, and high specific surface area, have become a research hotspot in water treatment. Mg-MOF-74, with its ultra-high specific surface area, rich pore structure, and exceptional thermal and chemical stability, has been the focus of much current research on Mg-MOF-74, aiming to improve gas adsorption and separation efficiency. An et al. [An H, Tian W, Lu X, et al. Chemical Engineering Journal, 2023, 469:144052.] proposed a method for preparing a hierarchically porous Mg-MOF-74 that significantly improved its carbon dioxide adsorption performance, exhibiting excellent low-pressure adsorption performance, making it suitable for carbon capture in real flue gas environments. Ma et al. [Ma M, Zhou A, Hong T, et al. Chemical Engineering Journal, 2023, 476:146845.] achieved precise tuning of the crystal structure, morphology, and pore structure of Mg-MOF-74 by adjusting the polarity of the reaction solvent, thereby increasing its carbon dioxide adsorption capacity. Among the reported MOFs, nanostructured Mg-MOF-74 has achieved good results in gas adsorption due to its unique framework structure. Unfortunately, however, the high adsorption performance of Mg-MOF-74 is rarely extended to wastewater treatment. In fact, the central Mg atom of Mg-MOF-74 is non-toxic and will not cause secondary pollution to the water body. This is very important for the practical application of Mg-MOF-74 in wastewater treatment. Thiol can form stable complexes with heavy metal ions to capture heavy metal ions in the chemical bonds on the surface of thiol. Thiol is an excellent ligand, and its Lewis acid-base interaction with various heavy metal ions (Hg 2+ , Pb 2+ and Cu 2+ Xia et al. [Xia Z, Baird L, Zimmerman N, Yeager M. Applied Surface Science, 2017, 416: 565-73.] introduced thiol groups on the surface of γ-ALOOH nanowhisker film through acidic catalysis, forming a thin thiol coating on the surface of the nanowhisker film. The γ-ALOOH nanowhisker film treated with thiol functional groups showed better adsorption of heavy metal ions, including Hg 2 + , Pb 2+ and Cu 2+However, Mg-MOF-74 lacks effective functional groups in its structural design, resulting in deficiencies in metal adsorption. Its limited application in gas absorption and lack of functional groups have limited its further development and application in heavy metal ion adsorption and oil-water separation. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method and application of a thiolated Mg-MOF-74 polysulfone composite membrane. The preparation method has strong operability, a wide range of raw material sources, and good separation and adsorption properties for different types of oil-water mixtures and heavy metal ions.

[0005] To address the above-mentioned challenges, the present invention utilizes polysulfone as the membrane substrate. A hydrophilic polymer is introduced into the membrane material via free radical polymerization. Through rational synthetic design and post-modification strategies, thiol groups are introduced onto Mg-MOF-74, optimizing surface properties and targeted performance enhancements. This results in a roughened micro-nanostructure and a polysulfone membrane capable of adsorbing heavy metal ions for oil-water separation. The resulting membrane can efficiently separate stable water-in-oil and oil-in-water emulsions, exhibiting excellent anti-fouling and recyclability, and has broad application prospects.

[0006] The present invention proposes a preparation and application of a thiolated Mg-MOF-74 polysulfone composite membrane, and the technical solution adopted is as follows:

[0007] A hydrophilic polymer is introduced into a polysulfone substrate via free radical polymerization, yielding a P-PSF membrane after non-solvent-induced phase separation. Mg-MOF-74 nanoparticles are modified with a silane coupling agent containing a thiol group to yield thiolated Mg-MOF-74. The thiolated Mg-MOF-74 nanoparticles are then used to modify the P-PSF membrane, creating a surface micro-nano roughened structure that is then loaded onto the membrane surface. This ultimately yields a thiolated Mg-MOF-74 polysulfone composite membrane capable of oil-water separation and heavy metal ion adsorption. The strong coordination of the thiol groups enables the capture of heavy metal ions in solution, while hydrogen bonding and electrostatic interactions between the particles and the membrane surface further enhance the particle stability on the membrane surface. The micro-nano roughened structure and excellent self-cleaning properties endow the membrane with a high specific surface area and efficient separation capability. This preparation method utilizes readily available raw materials and is highly operational. It has broad application value in heavy metal ion pollution treatment and wastewater treatment.

[0008] The present invention proposes a preparation and application of a thiolated Mg-MOF-74 polysulfone composite membrane. The specific steps are as follows:

[0009] (1) Introducing a hydrophilic polymer into polysulfone by free radical polymerization: polysulfone is dissolved in an appropriate amount of solvent A, and then monomer B is added to the solution. The reaction system is subjected to atomic free radical polymerization at 45-75°C under the action of a crosslinker C and an initiator D in a nitrogen or argon atmosphere for 6-10 hours; the reaction solution is ultrasonically debubbled, the film is scraped with a scraper, and phase inversion is performed in a water coagulation bath; the scraping parameters are an ambient temperature of 20-30°C, a humidity of 30-50%, and a scraping thickness of 100-300 μm.

[0010] (2) Dissolve magnesium nitrate hexahydrate and 2,5-dihydroxyterephthalic acid in solvent E, sonicate for 20-40 minutes, place in a polytetrafluoroethylene reactor, heat at 110-140°C for 16-19 hours, remove, wash with dimethylformamide and ethanol, dry at 45-75°C in vacuum for 6-9 hours, and grind to obtain Mg-MOF-74. Dissolve Mg-MOF-74, polyvinylpyrrolidone, and ammonia water in solvent F, add (3-mercaptopropyl)-trimethoxysilane dropwise with vigorous stirring, filter after stirring for a period of time, and dry at 45-75°C in vacuum for 6-9 hours to obtain thiolated Mg-MOF-74.

[0011] (3) Dispersing the thiolated Mg-MOF-74 in solvent G to obtain a mixed solution, immersing the P-PSF membrane prepared in (1) in the mixed solution for reaction at a reaction temperature of 20-30°C and a reaction time of 4-6 hours; finally, drying under vacuum at 45-75°C for 6-9 hours to obtain the thiolated Mg-MOF-74 polysulfone composite membrane.

[0012] The mass ratio of the solvent A, polysulfone, monomer B, crosslinking agent C and initiator D in step (1) of the present invention is 1000-2500:300-600:100-200:1-5:1-5.

[0013] The mass ratio of Mg-MOF-74, polyvinyl pyrrolidone, aqueous ammonia and solvent F in step (2) of the present invention is 50-80:3-5:110-150:10000-15000.

[0014] The mass ratio of the thiolated Mg-MOF-74 to the solvent G in step (3) of the present invention is 5-10:700-1000.

[0015] The solvent A is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, ethanol, and deionized water.

[0016] The monomer B is one or more of 2-hydroxyethyl methacrylate, methacryloyloxyethyl trimethylammonium chloride, and hydroxyethyl acrylate.

[0017] The cross-linking agent C is one or more of N-methyldiallylamine, N,N-methylenebisacrylamide, and divinylbenzene;

[0018] The initiator D is one or more of ammonium persulfate, azobisisobutyronitrile, and diacyl peroxide.

[0019] The solvent E is one or more of deionized water, ethanol, methanol, n-propanol, isopropanol, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0020] The solvent F is one or more of deionized water, ethanol, methanol, n-propanol, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0021] The solvent G is one or more of deionized water, ethanol, methanol, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0022] The invention discloses an application of a thiolated Mg-MOF-74 polysulfone composite membrane prepared in the present invention in the selective separation of oil-water mixtures.

[0023] The invention discloses an application of a thiolated Mg-MOF-74 polysulfone composite membrane prepared by the invention in adsorbing heavy metal ions.

[0024] The thiolated Mg-MOF-74 polysulfone composite membrane prepared by the present invention exhibits superhydrophilicity and superoleophilicity in air, while exhibiting superoleophobicity and superhydrophobicity underwater. The thiolated Mg-MOF-74 polysulfone composite membrane prepared by the present invention has excellent self-cleaning properties and can maintain excellent heavy metal adsorption and energy absorption after repeated use.

[0025] The thiolated Mg-MOF-74 polysulfone composite membrane prepared by the present invention can efficiently adsorb heavy metal ions in a solution and reduce the content of heavy metal ions in the solution.

[0026] The preparation method of the thiolated Mg-MOF-74 polysulfone composite membrane prepared by the present invention is simple and has strong operability.

[0027] The present invention introduces a hydrophilic polymer into a polysulfone substrate by free radical polymerization, and obtains a modified polysulfone membrane (P-PSF) after non-solvent-induced phase separation; Mg-MOF-74 nanoparticles are modified with a silane coupling agent containing a thiol group to obtain thiolated Mg-MOF-74; the P-PSF membrane is modified with the thiolated Mg-MOF-74 nanoparticles to construct a surface micro-nano rough structure, and finally a thiolated Mg-MOF-74 polysulfone composite membrane with oil-water separation and adsorption of heavy metal ions is obtained. The present invention innovatively couples a silane coupling agent containing a thiol group with the hydroxyl groups on the surface of Mg-MOF-74 to obtain thiolated Mg-MOF-74. Among them, the strong coordination effect of the thiol group can capture heavy metal ions in the solution, the hydrogen bonding effect and electrostatic interaction between the particles and the membrane surface can further improve the stability of the particles on the membrane surface, and the micro-nano rough structure and excellent self-cleaning properties give the membrane a high specific surface area and efficient separation ability. The preparation method has readily available raw materials and strong operability, and has wide application value in the fields of oily wastewater treatment, heavy metal ion adsorption, and the like. BRIEF DESCRIPTION OF THE DRAWINGS The following is a further detailed description of the implementation method of the present invention in conjunction with the accompanying drawings.

[0028] Figure 1 This is a mechanism diagram for preparing thiolated Mg-MOF-74 polysulfone composite membrane;

[0029] Figure 2 The XRD, IR, XPS and EDS characterization diagrams of the thiolated Mg-MOF-74 polysulfone composite membrane are shown;

[0030] Figure 3 It is a schematic diagram of the synthesis process for preparing thiolated Mg-MOF-74 polysulfone composite membrane;

[0031] Figure 4 Scanning electron micrographs of (aa”) pure polysulfone membrane, (bb”) P-PSF, (cc”) thiolated Mg-MOF-74, and (dd”) thiolated Mg-MOF-74 polysulfone composite membrane at different magnifications;

[0032] Figure 5 The contact angles of the prepared thiolated Mg-MOF-74 polysulfone composite membrane to water (a) in air and oil (b) in air.

[0033] Figure 6 The contact angles of (a) oil under water and (b) water under oil of the prepared thiolated Mg-MOF-74 polysulfone composite membrane.

[0034] Figure 7The prepared thiolated Mg-MOF-74 polysulfone composite membrane shows (a) the pulling process of an oil droplet under water and (b) the pulling process of a water droplet under oil (the oil is n-hexane).

[0035] Figure 8 The water contact angles of (a) pure polysulfone membrane of Comparative Example 1 and (b) P-PSF membrane of Comparative Example 2 after only the introduction of hydrophilic polymer;

[0036] Figure 9 The separation process of (a) oil-in-water emulsion and (b) water-in-oil emulsion by the prepared thiolated Mg-MOF-74 polysulfone composite membrane;

[0037] Figure 10 The particle size analysis of the prepared thiolated Mg-MOF-74 polysulfone composite membrane before and after separation of (a) oil-in-water emulsion and (b) water-in-oil emulsion.

[0038] Figure 11 The separation flux and separation efficiency of the prepared thiolated Mg-MOF-74 polysulfone composite membrane for five different (a) oil-in-water emulsions and (b) water-in-oil emulsions: toluene, n-hexane, n-heptane, petroleum ether, and liquid paraffin;

[0039] Figure 12 The prepared thiolated Mg-MOF-74 polysulfone composite membrane is effective for heavy metal ions Hg 2+ , Pb 2+ , Cu 2+ removal efficiency. DETAILED DESCRIPTION

[0040] The present invention is further described below with reference to specific examples, but the protection scope of the present invention is not limited thereto.

[0041] Example 1:

[0042] A method for preparing a thiolated Mg-MOF-74 polysulfone composite membrane (reaction route and preparation process are shown in FIG Figure 1 and Figure 3 As shown), comprising the following process steps:

[0043] (1) The hydrophilic polymer was introduced into polysulfone by free radical polymerization: 3.8 g of polysulfone (Dongwan Haosheng New Materials Co., Ltd., model 6010) was dissolved in 20 g of solvent N-methylpyrrolidone, and then 1 g of monomer methacryloyloxyethyl trimethylammonium chloride was added to the solution. The reaction system was polymerized under the action of 0.01 g of cross-linking agent N,N'-methylenebisacrylamide and 0.01 g of initiator 2'2-azobisisobutyronitrile. The polymerization time was 8 h at 60 ° C under nitrogen atmosphere; the reaction solution was ultrasonically debubbled and film was scraped with a film scraper at 25 ° C to a thickness of 200 μm. Finally, the phase was inverted in a water coagulation bath to obtain a P-PSF membrane.

[0044] (2) 7.68 g of hexahydromagnesium nitrate and 0.632 g of 2,5-dihydroxyterephthalic acid were dissolved in a mixed solution of 120 mL of dimethylformamide, 8 mL of deionized water, and 8 mL of ethanol. The solution was ultrasonicated for 35 min until it became transparent and then transferred to a polytetrafluoroethylene reactor. The solution was heated at 110 °C for 18 h and then naturally cooled. The product was washed with ethanol and vacuum dried in a vacuum drying oven at 60 °C for 9 h. The product was taken out and ground to obtain Mg-MOF-74.

[0045] (3) 0.5 g of Mg-MOF-74, 0.03 g of polyvinylpyrrolidone and 1.1 mL of ammonia water were dissolved in a mixed solution consisting of 60 mL of anhydrous ethanol and 60 mL of deionized water. 0.2 g of (3-mercaptopropyl)-trimethoxysilane was added dropwise under vigorous stirring and reacted for 4 h. The mixture was filtered and vacuum dried at 45 °C for 9 h to obtain thiolated Mg-MOF-74.

[0046] (4) Disperse 0.5 g of thiolated Mg-MOF-74 in 70 mL of ethanol to obtain a mixed solution, and quickly immerse the membrane prepared in (1) in the mixed solution to react, thereby loading the thiolated Mg-MOF-74 nanoparticles onto the membrane. The reaction temperature is 20° C., and the reaction time is 6 h. Finally, a thiolated Mg-MOF-74 polysulfone composite membrane is obtained.

[0047] The XRD, IR, XPS and EDS characterization of the thiolated Mg-MOF-74 polysulfone composite membrane are as follows: Figure 2 As shown, Figure (a) and Figure (b) are the XRD spectra of Mg-MOF-74 and thiolated Mg-MOF-74 (HS-Mg-MOF-74), respectively. The spectrum of HS-Mg-MOF-74 retains the characteristic peaks of Mg-MOF-74, but the intensity of specific peaks is significantly weakened or completely disappears compared with the original material. This structural change may be caused by the coordination effect of the thiol group. Figure (c) and Figure (d) are the infrared spectra of Mg-MOF-74 and HS-Mg-MOF-74, respectively. 575cm -1The peak at 890 cm is related to the Mg-O stretching vibration. -1 (Si-C stretching), 1090cm -1 (Si-O stretching) and 2565cm -1 The characteristic peaks of (-SH) indicate the successful grafting of thiol groups onto the Mg-MOF-74 surface. Figure (e) shows the full XPS spectrum of the thiolated Mg-MOF-74 polysulfone composite membrane, showing distinct peaks at O1s (529.08 eV), N1s (423.08 eV), C1s (282.08 eV), S2p (161.08 eV), Si2p (100.08 eV), and Mg2p (50.04 eV). Figure (f) shows three distinct peaks at 529.3 eV, 531.8 eV, and 532.6 eV in the O1s spectrum, attributed to Si-O-Mg, C=O, and Si-O-Si bonds, respectively. The appearance of Si-O-Si bonds indicates that (3-mercaptopropyl)-trimethoxysilane (MPTS) has successfully undergone hydrolysis and condensation to form a siloxane network. Si-O-Mg bonds also demonstrate the successful incorporation of hydrolyzed MPTS into HS-Mg-MOF-74. Analysis of the Si 2p spectrum (Figure (g)) reveals two new peaks at 101.1 eV and 101.9 eV, corresponding to Si-O-Si and C-Si-O bonds, respectively, confirming the successful synthesis of MPTS. The S2p spectrum (Figure (h)) exhibits a primary S2p3 / 2 peak at 162.9 eV, characteristic of thiol groups, confirming the effective thiol functionalization of the MOF surface. Analysis of the C1s spectrum (Figure (i)) reveals a C-N bond at 285.5 eV, verifying the interaction between the particle and the P-PSF substrate. Figure (j) shows an EDS analysis of the thiolated Mg-MOF-74 polysulfone composite membrane. The membrane contains C, N, O, Si, S, and Mg elements, with sulfur uniformly distributed on the surface, further confirming the successful incorporation of HS-Mg-MOF-74 into the P-PSF substrate. The above experimental results verified the successful preparation of thiolated Mg-MOF-74 polysulfone composite membrane.

[0048] The scanning electron microscopy image of the prepared thiolated Mg-MOF-74 polysulfone composite membrane is as follows: Figure 4 (dd”);

[0049] The contact angles of the prepared thiolated Mg-MOF-74 polysulfone composite membrane (a) to water in air and (b) to oil in air are shown in FIG. Figure 5 As shown; the contact angle of the prepared thiolated Mg-MOF-74 polysulfone composite membrane (a) oil under water, (b) the contact angle of water under oil as shown Figure 6 As shown;

[0050] The prepared thiolated Mg-MOF-74 polysulfone composite membrane (a) pull-up process of oil droplets under water and (b) pull-up process of water droplets under oil (the oil is n-hexane) are as follows Figure 7 As shown;

[0051] The separation flux and separation efficiency of the prepared thiolated Mg-MOF-74 polysulfone composite membrane for five different (a) oil-in-water emulsions and (b) water-in-oil emulsions are as follows: Figure 11 As shown;

[0052] Figure 12 The prepared toluene, n-hexane, n-heptane, petroleum ether, liquid paraffin to heavy metal ions Hg 2+ , Pb 2+ , Cu 2+ removal efficiency.

[0053] Example 2:

[0054] A thiolated Mg-MOF-74 polysulfone composite membrane (reaction route and preparation process shown in FIG Figure 1 and Figure 3 As shown), comprising the following process steps:

[0055] (1) The hydrophilic polymer was introduced into polysulfone by free radical polymerization: 4.4 g of polysulfone was dissolved in 24 g of solvent N-methylpyrrolidone, and then 1.3 g of monomer methacryloyloxyethyl trimethylammonium chloride was added to the solution. The reaction system was polymerized under the action of 0.02 g of cross-linking agent N,N'-methylenebisacrylamide and 0.02 g of initiator 2'2-azobisisobutyronitrile. The polymerization time was 7 h at 70 ° C under nitrogen atmosphere. The reaction solution was ultrasonically debubbled and film was scraped with a film scraper at 30 ° C to a thickness of 250 μm. Finally, the phase inversion was carried out in a water coagulation bath to obtain a P-PSF membrane.

[0056] (2) 8 g of hexahydromagnesium nitrate and 0.8 g of 2,5-dihydroxyterephthalic acid were dissolved in a mixed solution of 140 mL of dimethylformamide, 10 mL of deionized water, and 10 mL of ethanol. The solution was ultrasonicated for 30 min until it became transparent and then transferred to a polytetrafluoroethylene reactor. The solution was heated at 120 °C for 17 h and then naturally cooled. The product was washed with ethanol and dried in a vacuum drying oven at 70 °C for 6 h. The product was taken out and ground to obtain Mg-MOF-74.

[0057] (3) 0.6 g of Mg-MOF-74, 0.04 g of polyvinylpyrrolidone and 1.3 mL of ammonia water were dissolved in a mixed solution consisting of 70 mL of anhydrous ethanol and 70 mL of deionized water. 0.3 g of (3-mercaptopropyl)-trimethoxysilane was added dropwise under vigorous stirring and reacted for 5 h. The mixture was filtered and vacuum dried at 60 °C for 7 h to obtain thiolated Mg-MOF-74.

[0058] (4) Disperse 0.6 g of thiolated Mg-MOF-74 in 80 mL of ethanol to obtain a mixed solution, and quickly immerse the membrane prepared in (1) in the mixed solution to react, thereby loading the thiolated Mg-MOF-74 nanoparticles onto the membrane. The reaction temperature is 25° C., and the reaction time is 5 h. Finally, a thiolated Mg-MOF-74 polysulfone composite membrane is obtained.

[0059] Example 3:

[0060] A thiolated Mg-MOF-74 polysulfone composite membrane (reaction route and preparation process shown in FIG Figure 1 and Figure 3 As shown), comprising the following process steps:

[0061] (1) The hydrophilic polymer was introduced into polysulfone by free radical polymerization: 2.5 g of polysulfone was dissolved in 18 g of solvent N-methylpyrrolidone, and then 0.8 g of monomer methacryloyloxyethyl trimethylammonium chloride was added to the solution. The reaction system was polymerized under the action of 0.008 g of cross-linking agent N,N'-methylenebisacrylamide and 0.008 g of initiator 2'2-azobisisobutyronitrile. The polymerization time was 6 h at 75 ° C under nitrogen atmosphere. The reaction solution was ultrasonically debubbled and film was scraped with a scraper at 25 ° C to a thickness of 230 μm. Finally, the phase inversion was carried out in a water coagulation bath to obtain a P-PSF membrane.

[0062] (2) 6 g of hexahydromagnesium nitrate and 0.6 g of 2,5-dihydroxyterephthalic acid were dissolved in a mixed solution of 100 mL of dimethylformamide, 6 mL of deionized water, and 6 mL of ethanol. The solution was ultrasonicated for 20 min until it became transparent and then transferred to a polytetrafluoroethylene reactor. The solution was heated at 120 °C for 16 h and then naturally cooled. The product was washed with ethanol and dried in a vacuum drying oven at 50 °C for 7 h. The product was taken out and ground to obtain Mg-MOF-74.

[0063] (3) 0.4 g of Mg-MOF-74, 0.02 g of polyvinylpyrrolidone and 0.9 mL of ammonia water were dissolved in a mixed solution consisting of 40 mL of anhydrous ethanol and 40 mL of deionized water. 0.1 g of (3-mercaptopropyl)-trimethoxysilane was added dropwise under vigorous stirring and reacted for 4 h. The mixture was filtered and vacuum dried at 55 °C for 6 h to obtain thiolated Mg-MOF-74.

[0064] (4) 0.4 g of thiolated Mg-MOF-74 was dispersed in 60 mL of ethanol to obtain a mixed solution, and the membrane prepared in (1) was quickly immersed in the mixed solution to react, thereby loading the thiolated Mg-MOF-74 nanoparticles onto the membrane. The reaction temperature was 30° C. and the reaction time was 4 h. Finally, a thiolated Mg-MOF-74 polysulfone composite membrane was obtained.

[0065] Comparative Example 1:

[0066] (1) Dissolve 5 g of polysulfone in 45 g of N-methylpyrrolidone and stir at 60°C for 6 h;

[0067] (2) The solution obtained in (1) was allowed to stand for a period of time to remove bubbles, and the membrane was scraped with a scraper, and phase inversion was carried out in a methanol coagulation bath to obtain a pure polysulfone membrane.

[0068] The scanning electron microscopy image of the prepared pure polysulfone membrane is as follows Figure 4 (a, a') shown;

[0069] The water contact angle of the prepared pure polysulfone membrane in air is as follows Figure 8 As shown in (a).

[0070] Comparative Example 2:

[0071] (1) The hydrophilic polymer was introduced into polysulfone by free radical polymerization: polysulfone was dissolved in N-methylpyrrolidone solvent, and 1 g of monomer methacryloyloxyethyl trimethylammonium chloride was added to the solution. The reaction system was reacted under the action of crosslinker N,N'-methylenebisacrylamide and initiator azobisisobutyronitrile at 70 °C under nitrogen atmosphere for 8 h.

[0072] (2) The reaction solution in (1) was ultrasonically debubbled, the film was scraped with a scraper, and phase-inverted in a water coagulation bath to obtain a P-PSF membrane.

[0073] The scanning electron microscope image of the prepared P-PSF membrane is as follows: Figure 4 (b, b');

[0074] The water contact angle of the prepared P-PSF film in air is as follows: Figure 8 (b) shown.

[0075] The above embodiments are not limitations of the present invention, and the present invention is not limited to the above embodiments. As long as the requirements of the present invention are met, they belong to the protection scope of the present invention.

[0076] The present invention couples a silane coupling agent containing a mercapto group with hydroxyl groups on the surface of Mg-MOF-74 to produce thiolated Mg-MOF-74. The strong coordination of the mercapto groups allows the capture of heavy metal ions in solution. The hydrogen bonding and electrostatic interactions between the particles and the membrane surface further enhance the stability of the particles on the membrane surface. The micro-nano rough structure and excellent self-cleaning properties impart a high specific surface area and efficient separation capability to the membrane. The preparation method utilizes readily available raw materials and is highly operable. It has broad application value in areas such as heavy metal ion pollution treatment and sewage treatment.

Claims

1. A method for preparing a thiolated Mg-MOF-74 polysulfone composite membrane, characterized in that: The following steps are involved: (1) polysulfone is dissolved in solvent A, and then monomer B is added to the solution. The reaction system reacts under the action of crosslinking agent C and initiator D, and atomic free radical polymerization is performed under nitrogen or argon atmosphere to obtain a reaction solution. The reaction solution is subjected to ultrasonic debubbling, and the film is scraped with a scraping machine, and phase inversion is performed in a water coagulation bath to obtain a modified polysulfone membrane; (2) dissolving Mg-MOF-74, polyvinyl pyrrolidone, and ammonia in solvent F, adding (3-mercaptopropyl)-trimethoxysilane dropwise under stirring, stirring for a period of time, filtering, and vacuum drying to obtain mercaptolated Mg-MOF-74; (3) Dispersing the thiolated Mg-MOF-74 in solvent G to obtain a mixed solution, immersing the P-PSF membrane prepared in (1) in the mixed solution for reaction, and vacuum drying to obtain the thiolated Mg-MOF-74 polysulfone composite membrane.

2. The method for preparing the thiolated Mg-MOF-74 polysulfone composite membrane according to claim 1, wherein: In step (1), the mass ratio of the solvent A, polysulfone, monomer B, crosslinking agent C and initiator D is 1000-2500:300-600:100-200:1-5:1-5; Wherein, the solvent A is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, ethanol, and deionized water; The monomer B is one or more of 2-hydroxyethyl methacrylate, methacryloyloxyethyl trimethylammonium chloride, and hydroxyethyl acrylate; The cross-linking agent C is one or more of N-methyldiallylamine, N,N-methylenebisacrylamide, and divinylbenzene; The initiator D is one or more of ammonium persulfate, azobisisobutyronitrile, and diacyl peroxide.

3. The method for preparing the thiolated Mg-MOF-74 polysulfone composite membrane according to claim 1, wherein: In step (1), the time of atomic radical polymerization is 6-10 hours, and the temperature of atomic radical polymerization is 45-75° C.; The parameters of the scraping film are as follows: ambient temperature 20-30°C, humidity 30-50%, and scraping film thickness 100-300μm.

4. The method for preparing the thiolated Mg-MOF-74 polysulfone composite membrane according to claim 1, wherein: In step (2), the preparation of Mg-MOF-74 includes: Magnesium nitrate hexahydrate and 2,5-dihydroxyterephthalic acid were dissolved in solvent E, and after ultrasonication, the mixture was placed in a polytetrafluoroethylene reactor and heated. After heating, the mixture was washed with dimethylformamide and ethanol, and then vacuum dried. The dried particles were ground to obtain Mg-MOF-74. The mass ratio of the magnesium nitrate hexahydrate, 2,5-dihydroxyterephthalic acid and solvent E is 35-50:3-6:500-1000.

5. The method for preparing the thiolated Mg-MOF-74 polysulfone composite membrane according to claim 1, wherein: In step (2), the mass ratio of the Mg-MOF-74, polyvinyl pyrrolidone, aqueous ammonia and solvent F is 50-80:3-5:110-150:10000-15000.

6. The method for preparing the thiolated Mg-MOF-74 polysulfone composite membrane according to claim 1, wherein: In step (2), the ultrasonication time is 20-40 min, the heating time in the polytetrafluoroethylene reactor is 16-19 h, and the heating temperature is 110-140° C.; The vacuum drying temperature is 45-75°C, and the vacuum drying time is 6-9h.

7. The method for preparing the thiolated Mg-MOF-74 polysulfone composite membrane according to claim 1, wherein: In step (2), the solvent E is one or more of deionized water, ethanol, methanol, n-propanol, isopropanol, N,N-dimethylformamide, and N,N-dimethylacetamide; The solvent F is one or more of deionized water, ethanol, methanol, n-propanol, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

8. The method for preparing the thiolated Mg-MOF-74 polysulfone composite membrane according to claim 1, wherein: In step (3), the mass ratio of the thiolated Mg-MOF-74 to the solvent G is 5-10:700-1000; the reaction time is 4-6 hours; The solvent G is one or more of deionized water, ethanol, methanol, N,N-dimethylformamide, and N,N-dimethylacetamide.

9. Use of the thiolated Mg-MOF-74 polysulfone composite membrane prepared by the preparation method according to any one of claims 1 to 8 in adsorbing heavy metal ions.

10. Use of the thiolated Mg-MOF-74 polysulfone composite membrane prepared by the preparation method according to any one of claims 1 to 8 in the selective separation of oil-water mixtures.

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