MXene-MOF composite membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of membrane separation, in particular to an MXene-MOF composite membrane as well as a preparation method and application thereof. The MXene-MOF composite membrane comprises a base membrane, an MXene nanosheet and an MOF material, wherein the MXene nanosheet and the MOF material are located on the surface of one side of the base membrane; the MXene nanosheet comprises a single-layer nanosheet, and the MOF material is located between sheet layers of the MXene nanosheet and located on the surface of the MXene nanosheet; the MOF material comprises MIL-101 (Fe) coated with quinone; the mass ratio of the MXene nanosheet to the MOF material is 1: (1-9). The MXene-MOF composite membrane disclosed by the invention has photocatalytic self-cleaning capability, stable flux and relatively high hydrophilicity, meanwhile, the anti-pollution performance of the MXene-MOF composite membrane is improved, and the flux and the rejection rate of the MXene-MOF composite membrane are considered.

Description

Technical Field

[0001] The present application relates to the field of membrane separation technology, and specifically to a MXene-MOF composite membrane and a preparation method and application thereof. Background Art

[0002] Although membrane separation technology has the advantages of high separation efficiency, no secondary pollution, energy saving and environmental protection, long-term stable operation, etc., membrane fouling, that is, the strong adhesion of pollutants to the membrane surface during operation, leads to scaling, reduced permeability and reduced separation efficiency, which limits the practical application of membrane separation technology in the field of oil-water separation.

[0003] Therefore, developing separation membranes with self-cleaning properties, anti-fouling ability, and stable flux is the key to addressing these challenges. Summary of the invention

[0004] The present application provides a MXene-MOF composite membrane and a preparation method and application thereof, which can enable the MXene-MOF composite membrane to have photocatalytic self-cleaning ability, stable flux and high hydrophilicity, while improving the anti-pollution performance of the MXene-MOF composite membrane, and taking into account the flux and retention rate of the MXene-MOF composite membrane.

[0005] In a first aspect, the present application provides a MXene-MOF composite film, which includes a base film, and MXene nanosheets and MOF materials located on one surface of the base film; the MXene nanosheets include single-layer nanosheets, and the MOF material is located between the sheets of the MXene nanosheets and on the surface of the MXene nanosheets; the MOF material includes quinone-coated MIL-101 (Fe); the mass ratio of the MXene nanosheets to the MOF material is 1: (1-9).

[0006] In some embodiments, the deposition amount of MXene nanosheets and MOF materials on the surface of the substrate is 1-100 μg / cm 2 .

[0007] In some embodiments, the MXene nanosheets include Ti 3 C 2 T x .

[0008] In some embodiments, the base film includes any one of a polyvinylidene fluoride film, a polyethersulfone film, a polysulfone film, and a polyethylene film.

[0009] In some embodiments, the lateral size of the MXene nanosheet is 8-10 μm, and the thickness of the MXene nanosheet is 1-3 nm.

[0010] In some embodiments, the average particle size of the MOF material is 220-300 nm.

[0011] In a second aspect, the present application provides a method for preparing the MXene-MOF composite membrane of the first aspect of the present application, the preparation method comprising: providing MXene nanosheets and MOF materials; depositing a mixed solution comprising MXene nanosheets and MOF materials on one side surface of a base membrane by vacuum-assisted filtration to obtain a MXene-MOF composite membrane.

[0012] In some embodiments, the step of providing MXene nanosheets and MOF materials includes: performing HCl-LiF system wet chemical etching and organic solvent-assisted intercalation on MAX powder to obtain MXene nanosheets.

[0013] In some embodiments, the step of providing MXene nanosheets and MOF materials includes: mixing catechol with MIL-101(Fe) and then performing ultrasonic-assisted oxidation to obtain quinone-coated MIL-101(Fe); the mass ratio of catechol to MIL-101(Fe) is 1:(4-6); and the ultrasonic treatment time in the ultrasonic-assisted oxidation is 50-70 min.

[0014] In some embodiments, the step of depositing a mixed solution including MXene nanosheets and MOF materials on one side surface of the base film by vacuum-assisted filtration includes: before vacuum-assisted filtration, ultrasonically treating the mixed solution including MXene nanosheets and MOF materials.

[0015] In some embodiments, the oxidant for ultrasound-assisted oxidation comprises H 2 O 2 ; Catalysts for ultrasound-assisted oxidation include CuSO 4 ;CuSO 4 The concentration of H 2 O 2 The concentration is 3-7mmol / L.

[0016] In some embodiments, the preparation method further comprises: pre-treating the base film before assembling, wherein the pre-treatment comprises ultrasonic treatment.

[0017] In some embodiments, the preparation method further comprises: heat treating the assembled MXene-MOF composite membrane at a temperature of 55° C.-65° C. and for a time of 3-5 min.

[0018] In a third aspect, the present application provides an application of the MXene-MOF composite membrane of the first aspect of the present application in wastewater treatment.

[0019] In the embodiment of the present application, a bionic layer is formed on the MIL-101 (Fe) nanoparticles, so that the modified MIL-101 (Fe) nanoparticles show better light absorption ability and better hydrophilicity, so that the MXene-MOF composite membrane has photocatalytic self-cleaning ability, and it can operate stably during the separation process. The single-layer MXene nanosheet has a large specific surface area, which can make the MXene-MOF composite membrane have a higher flux. By combining quinone-coated MIL-101 (Fe) and a single-layer MXene nanosheet, the MXene-MOF composite membrane can have photocatalytic self-cleaning ability, stable flux and high hydrophilicity, and can also make the MXene-MOF composite membrane take into account both high flux and high retention rate during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application.

[0021] Figure 1 Scanning electron microscope (SEM) images of modified MXene nanosheets provided in some embodiments of the present application; Figure 2 Scanning electron microscope (SEM) images of modified MIL-101 (Fe) nanoparticles provided in some embodiments of the present application; Figure 3 A scanning electron microscope (SEM) image of the surface of the MXene-MOF composite membrane prepared in Example 2; Figure 4 A scanning electron microscope (SEM) image of a cross section of the MXene-MOF composite membrane prepared in Example 2; Figure 5 This is a test chart of the cyclic stability of the MXene-MOF composite film prepared in Example 2 under visible light irradiation. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings, but it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present application.

[0023] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0024] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0025] In the description of the embodiments of the present application, the term "and / or" is merely a term used to describe the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0026] In the description of the embodiments of the present application, the term "plurality" refers to more than two (including two).

[0027] Unless otherwise specified, the test temperature of each parameter mentioned in this application is 25°C.

[0028] MXene is a two-dimensional material composed of transition metal carbides, nitrides or carbonitrides (also known as MAX phase derivatives). Its high specific surface area provides excellent adsorption capacity, making MXene widely concerned in the field of wastewater treatment. MXene can effectively remove pollutants such as heavy metal ions, organic compounds and oil from water. However, the long separation process often leads to problems such as interlayer swelling, reduced separation efficiency and accumulation of pollutants in MXene, which have an adverse effect on the long-term performance of MXene membranes.

[0029] In view of this, the present application provides a MXene-MOF composite membrane and its preparation method and application, which can enable the MXene-MOF composite membrane to have photocatalytic self-cleaning ability, stable flux and high hydrophilicity, while improving the anti-pollution performance of the MXene-MOF composite membrane, and taking into account the flux and retention rate of the MXene-MOF composite membrane.

[0030] In a first aspect, the present application provides a MXene-MOF composite membrane, wherein the MXene-MOF composite membrane comprises a base membrane, and MXene nanosheets and MOF materials located on a surface of one side of the base membrane; The MXene nanosheets include single-layer nanosheets, and the MOF material is located between the sheets of the MXene nanosheets and on the surface of the MXene nanosheets; the MOF material includes quinone-coated MIL-101(Fe); the mass ratio of the MXene nanosheets to the MOF material is 1:(1-9).

[0031] Metal-organic frameworks (MOFs) are three-dimensional crystalline materials with porous structures formed by the coordination of metal ions or clusters with organic ligands. As photocatalysts, MOF materials can complete the inorganic transformation of organic compounds with minimal by-products and have good application prospects in wastewater treatment. Among Fe-MOF materials, MIL-101 (Fe) has become an excellent photocatalyst due to its high specific surface area, excellent light absorption performance, good thermal stability and chemical stability, and controllable surface chemical properties.

[0032] In the embodiment of the present application, a bionic layer is formed on the MIL-101 (Fe) nanoparticles, so that the modified MIL-101 (Fe) nanoparticles show better light absorption ability and better hydrophilicity, so that the MXene-MOF composite membrane has photocatalytic self-cleaning ability, and it can operate stably during the separation process. The single-layer MXene nanosheet has a large specific surface area, which can make the MXene-MOF composite membrane have a higher flux. By combining quinone-coated MIL-101 (Fe) and a single-layer MXene nanosheet, the MXene-MOF composite membrane can have photocatalytic self-cleaning ability, stable flux and high hydrophilicity, and can also make the MXene-MOF composite membrane take into account both high flux and high retention rate during operation.

[0033] Exemplarily, the mass ratio of MXene nanosheets to MOF materials can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9. Optionally, it can be 1:(3-7).

[0034] When the mass ratio of MXene nanosheets and MOF materials is within the above range, the MXene nanosheets and MOF materials can cooperate with each other, thereby improving the stability of the MXene nanosheet structure and enabling the MXene-MOF composite membrane to have both a higher flux and a higher retention rate during operation.

[0035] In some embodiments, the deposition amount of MXene nanosheets and MOF materials on the surface of the base film can be 1-100 μg / cm 2 , for example, 1 μg / cm 2 , 10μg / cm 2 , 20μg / cm 2 , 30μg / cm 2 40μg / cm 2 , 50μg / cm 2 , 60μg / cm 2 , 70μg / cm 2 , 80μg / cm 2 , 90μg / cm 2 , 100μg / cm 2. In this way, the relationship between the flux and the interception rate of the MXene-MOF composite membrane can be balanced, so that the MXene-MOF composite membrane can take into account both high flux and high interception rate during operation. In the embodiments of the present application, the deposition amount of MXene nanosheets and MOF materials on the surface of the base membrane refers to the total mass of MXene nanosheets and MOF materials per unit area.

[0036] In some embodiments, MXene nanosheets may include Ti 3 C 2 T x .

[0037] Ti 3 C 2 T x It has good hydrophilicity, large specific surface area and abundant surface modification groups.

[0038] In some embodiments, the base film may include any one of a polyvinylidene fluoride film, a polyethersulfone film, a polysulfone film, and a polyethylene film.

[0039] In some embodiments, the lateral size of the MXene nanosheets may be 8-10 μm, and the thickness of the MXene nanosheets may be 1-3 nm.

[0040] The lateral size of a MXene nanosheet refers to the size of the MXene nanosheet in the length or width direction when the MXene nanosheet is laid flat on a plane.

[0041] The lateral size and thickness of MXene nanosheets within the above range can increase the specific surface area of ​​MXene nanosheets, so that they have more interface contact areas with MOF materials, enhance the interface effect between MXene nanosheets and MOF materials, promote the separation and transfer of photogenerated carriers, and thus improve the photocatalytic performance of the composite film. The lateral size and thickness of MXene nanosheets within the above range can also provide a more uniform stress distribution, thereby improving the mechanical strength and flexibility of the composite film and increasing its life in practical applications. The lateral size and thickness of MXene nanosheets within the above range may also form a more regular membrane surface structure, reducing the probability of pollutants adhering to the membrane surface. In addition, the enhanced photocatalytic self-cleaning ability can also assist in the degradation of organic pollutants, further improving the anti-pollution performance of the composite film.

[0042] In some embodiments, the average particle size of the MOF material may be 220-300 nm.

[0043] When the average particle size of the MOF material is within the above range, the MOF material can have a higher specific surface area, thereby improving the catalytic performance of the MOF material.

[0044] In a second aspect, the present application provides a method for preparing a MXene-MOF composite film, the preparation method comprising: providing MXene nanosheets and MOF materials; A mixed solution including MXene nanosheets and MOF materials is deposited on one side of the base membrane by vacuum-assisted filtration to obtain a MXene-MOF composite membrane.

[0045] The mixed solution of the embodiment of the present application includes MXene nanosheets and MOF materials. The MXene nanosheets can assist in dispersing the MOFs materials, thereby improving the problem of poor dispersibility of MOF particles. The mixed solution including MXene nanosheets and MOF materials is deposited on one side of the base film by vacuum-assisted filtration, which can increase the binding force between the MXene nanosheets and the MOF materials and the base film, and at the same time make the MXene nanosheets neatly stacked, closely arranged, and the interlayer spacing more uniform. The surface of the MXene-MOF composite film presents a groove structure, thereby improving the anti-fouling performance of the MXene-MOF composite film.

[0046] In addition, the preparation method of the MXene-MOF composite membrane has a simple process, and the prepared MXene-MOF composite membrane can be used in the wastewater treatment process for a long time.

[0047] In some embodiments, the pressure of vacuum-assisted filtration may be 0.8-1 bar.

[0048] In some embodiments, the step of providing MXene nanosheets and MOF materials may include: performing HCl-LiF system wet chemical etching and organic solvent-assisted intercalation on MAX powder to obtain MXene nanosheets.

[0049] Single-layer MXene nanosheets can be obtained through wet chemical etching in the HCl-LiF system and organic solvent-assisted intercalation. Figure 1 Scanning electron microscope (SEM) images of modified MXene nanosheets provided in some embodiments of the present application. The MXene nanosheets prepared by wet chemical etching and organic solvent-assisted intercalation have larger lateral dimensions and lower thickness.

[0050] In some embodiments, the molar concentration of hydrochloric acid in the HCl-LiF system is 7-11 mol / L, the mass content of LiF is 0.03-0.07 g / mL, and the mass content of MAX powder is 0.02-0.04 g / mL.

[0051] In some embodiments, the organic solvent used for organic solvent-assisted intercalation may include one or both of dimethyl sulfoxide (DMSO) and dichloromethane (DCM).

[0052] MAX powder refers to a natural layered carbonitride inorganic non-metallic material composed of three elements. MAX powder is a type of nano-layered transition metal compound with a hexagonal lattice structure. The molecular formula is M n+1 AX n , (where M is generally a pre-transition metal, A is mainly a 13-15 main group element, X is carbon and / or nitrogen, and n is usually 1-3). MAX powder has a unique crystal structure of alternating MX and A layers, which makes it have the excellent properties of both metals and ceramics, such as good thermal and electrical conductivity, machinability, as well as good oxidation resistance, corrosion resistance, friction and wear resistance, etc.

[0053] In some embodiments, the step of performing HCl-LiF system wet chemical etching and organic solvent-assisted intercalation on MAX powder includes: adding MAX powder to a LiF / HCl mixed solution, stirring continuously for 40-60 hours under a 35°C-40°C water bath heating condition, so that the "Al" layer is completely etched. Add pure water for centrifugation and washing until the pH value of the supernatant is about 6. After centrifugation, take the bottom product and ultrasonicate it under nitrogen for 20-40 minutes.

[0054] Furthermore, the ultrasonic treatment product was mixed with dimethyl sulfoxide (DMSO) at a ratio of 1 g: (15 mL-25 mL) and stirred for 2-4 h. After stirring, an equal volume of dichloromethane (DCM) was added to the MXene / DMSO mixture and mixed thoroughly. Then water was added and the mixture was centrifuged at 7000-9000 rpm for 3 to 5 times to completely remove the dimethyl sulfoxide and dichloromethane residues. After washing with water and centrifuging 5 times, a single-layer MXene nanosheet was obtained.

[0055] In some embodiments, the step of providing MXene nanosheets and MOF materials may include: mixing catechol with MIL-101(Fe) and then performing ultrasound-assisted oxidation to obtain quinone-coated MIL-101(Fe).

[0056] Catechol can form a biomimetic layer on MIL-101 (Fe) nanoparticles through ultrasound-assisted oxidation, that is, catechol can be oxidized to quinone through ultrasound-assisted oxidation and coated on at least part of the surface of MIL-101 (Fe). As a result, the modified MIL-101 (Fe) nanoparticles show better light absorption ability and better hydrophilicity.

[0057] In some embodiments, the mass ratio of catechol to MIL-101(Fe) may be 1:(4-6).

[0058] The mass ratio of catechol to MIL-101(Fe) within the above range can further enhance the light absorption capacity and hydrophilicity of the quinone-coated MIL-101(Fe), further enhance the photocatalytic self-cleaning ability of the MXene-MOF composite film, and thus enhance the hydrophilicity and anti-fouling properties of the MXene-MOF composite film.

[0059] In some embodiments, the ultrasonic treatment time in ultrasonic assisted oxidation can be 50-70 minutes, for example, 50 minutes, 55 minutes, 60 minutes, 65 minutes, 70 minutes, or a range consisting of any two of the above values. The thickness and uniformity of the bionic layer have an important influence on the photocatalytic performance. The ultrasonic treatment time within the above range can improve the uniformity of the coating layer. In addition, adjusting the ultrasonic treatment time can adjust the density of the formed bionic layer, and the thickness of the bionic layer within a suitable range, reduce the adhesion of pollutants on the surface of the MXene-MOF composite film, and enhance the anti-pollution ability, so as to take into account the relationship between the flux, catalytic activity and its stability and anti-pollution ability of the MOF material.

[0060] In some embodiments, the step of depositing a mixed solution including MXene nanosheets and MOF materials on one side surface of the base film by vacuum-assisted filtration may include: ultrasonically treating the mixed solution including MXene nanosheets and MOF materials before vacuum-assisted filtration.

[0061] Ultrasonic treatment can make the MXene nanosheets and MOF materials mixed more evenly, thereby improving the uniformity of mixing of MXene nanosheets and MOF materials on the surface of the base membrane, further improving the anti-pollution performance of the MXene-MOF composite membrane, and taking into account the flux and retention rate of the MXene-MOF composite membrane.

[0062] In some embodiments, the oxidant for ultrasound-assisted oxidation may include H 2 O 2 .

[0063] In some embodiments, the catalyst for ultrasound-assisted oxidation may include CuSO 4 .

[0064] H 2 O 2 OH - Free radicals have strong oxidizing properties. In this embodiment, CuSO 4 With H 2 O 2Combined with the above, catechol can be oxidized to quinone and coated on at least part of the surface of MIL-101(Fe), and the above process can be faster, the oxidation process is mild and controllable, and the reaction process does not produce gas and can be carried out at room temperature. In addition, the system of MXene and quinone-coated MIL-101(Fe) suspension can be made more stable and uniform, and the particle size of quinone-coated MIL-101(Fe) loaded on the surface of MXene can be made uniform.

[0065] In some embodiments, CuSO 4 The concentration can be 8-12mmol / L, for example, 8mmol / L, 9mmol / L, 10mmol / L, 11mmol / L, 12mmol / L, or a range consisting of any two of the above values.

[0066] In some embodiments, H 2 O 2 The concentration can be 3-7mmol / L, for example, 3mmol / L, 4mmol / L, 5mmol / L, 6mmol / L, 7mmol / L, or a range consisting of any two of the above values.

[0067] By adjusting CuSO 4 and H 2 O 2 The concentration of is within the above range, which can make the process of oxidizing catechol to quinone and coating it on at least part of the surface of MIL-101(Fe) faster, the oxidation process is mild and controllable, and the reaction process does not generate gas and can be carried out at room temperature. In addition, it can also make the system of MXene and quinone-coated MIL-101(Fe) suspension more stable and uniform, and make the quinone-coated MIL-101(Fe) particles loaded on the MXene surface uniform in size.

[0068] Exemplarily, the steps of mixing catechol with MIL-101(Fe) and then subjecting the mixture to ultrasound-assisted oxidation to obtain quinone-coated MIL-101(Fe) include: pouring a terephthalic acid (PTA) solution into FeCl 3 6H 2 O solution, stirring continuously to mix thoroughly. Pour the mixed solution into a high pressure reactor and react at 100℃-120℃ for 18-22h. After the reaction is complete, wash the MIL-101 (Fe) solid with anhydrous ethanol for at least 5 times and transfer to a vacuum oven at 55℃-65℃ to dry for 10h-14h. Take 400-600mg of the dried MIL-101 (Fe) powder and add it to the H 2 O 2 (10mmol / L) and CuSO 4100 mL of a mixed solution of 5 mmol / L was added to the mixture. 100 mg of catechol was added to the mixture, and then ultrasonic treatment was performed for 1 h. After the ultrasonic treatment, centrifugation, washing and drying were performed in the same manner as MIL-101 (Fe) to obtain quinone-coated MIL-101 (Fe).

[0069] The pressure of the high-pressure reactor in the above reaction can be 2 bar-3 bar.

[0070] Figure 2 Scanning electron microscope (SEM) images of modified MIL-101 (Fe) nanoparticles provided in some embodiments of the present application. The crystals of the modified MOF material are complete octahedral structures, and the surface of the modified MOF is obviously coated with a layer of quinone obtained by oxidation of catechol.

[0071] In some embodiments, the preparation method further comprises: pre-treating the base film before assembling, and the pre-treatment may include ultrasonic treatment, thereby removing impurities on the surface of the base film, thereby increasing the bonding force between the MXene nanosheets and the base film, and between the MOF material and the base film.

[0072] Illustratively, the ultrasonic treatment may include placing the base membrane in deionized water and performing ultrasonic treatment.

[0073] In some embodiments, the preparation method further comprises: heat treating the assembled MXene-MOF composite membrane, the heat treatment temperature may be 55° C.-65° C., and the heat treatment time may be 3-5 min.

[0074] By setting the heat treatment time and temperature within the above range, the MXene-MOF composite membrane can be fully dried, and the stability of the MXene-MOF composite membrane structure can be improved, so that the MXene-MOF composite membrane has both a higher flux and a higher retention rate.

[0075] The first aspect of the present application is the application of the MXene-MOF composite membrane in wastewater treatment.

[0076] In some embodiments, the wastewater includes wastewater containing an oil-water emulsion.

[0077] Illustratively, the oil phase in the oil-water mixed emulsion includes one or more of n-hexane, cyclohexane, n-heptane, isooctane and petroleum ether.

[0078] Example The following examples describe the content of the present application in more detail, and these examples are only for illustrative purposes, because it is obvious to those skilled in the art that various modifications and variations are made within the scope of the present application. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the examples are commercially available.

[0079] Example 1 Preparation of MXene nanosheets: 1.6g LiF was dissolved in 30mL 9mol / L HCl solution and stirred continuously at room temperature for 10min to obtain a LiF / HCl mixed solution. Then 1g MAX powder was added to the LiF / HCl mixed solution in small amounts and multiple times, and stirred continuously for 48h under heating conditions at 35-40℃ water bath to completely etch the "Al layer. Pure water was added for centrifugation and washing until the pH value of the supernatant was about 6. After centrifugation, the bottom product was taken and ultrasonicated for 30min under nitrogen conditions. The ultrasonicated product was then mixed with dimethyl sulfoxide (DMSO) at a ratio of 1g: 20mL and stirred for 3h. After stirring, an equal volume of dichloromethane (DCM) was added to the MXene / DMSO mixture and mixed thoroughly. Then water was added and the mixture was centrifuged at 8000rpm for 3 to 5 times to completely remove dimethyl sulfoxide and dichloromethane residues. After further washing with water and centrifugation for 5 times, a single-layer MXene nanosheet was obtained.

[0080] Preparation of MOF materials: 0.166 g of terephthalic acid (PTA) was dissolved in 18 mL of N,N-dimethylformamide (DMF) solution and ultrasonicated for 20 min to completely dissolve it to obtain a terephthalic acid (PTA) solution. 3 6H 2 O was dissolved in 18 mL of N,N-dimethylformamide (DMF) solution and ultrasonicated for 20 min to completely dissolve it to obtain FeCl 3 6H 2 O solution. Subsequently, the terephthalic acid (PTA) solution was added with continuous stirring to FeCl 3 6H 2 O solution, stirring continuously for 1 hour to make it completely mixed. Pour the mixed solution into a high pressure reactor with a pressure of 2-3 bar, and react at 110℃ for 20 hours. After the reaction is completed, wash the MIL-101 (Fe) solid with anhydrous ethanol for at least 5 times and transfer it to a vacuum oven at 60℃ to dry for 12 hours. Take 500 mg of the dried MIL-101 (Fe) powder and add it to the H2 O 2 (10mmol / L) and CuSO 4 (5mmol / L) 100mL mixed solution. Then, 100mg of catechol was added to the mixture, and then ultrasonic treatment was performed for 1h. After the ultrasonic treatment, centrifugation, washing and drying were performed in the same way as MIL-101 (Fe) to obtain quinone-coated MIL-101 (Fe).

[0081] Preparation of MXene-MOF composite membrane: MXene nanosheets and quinone-coated MIL-101(Fe) were added to solvent water at a mass ratio of 1:3 to obtain a mixed solution, which was then loaded onto a vacuum filtration device with an effective area of ​​12.56 cm 2 The deposition amount of MXene nanosheets and quinone-coated MIL-101(Fe) on the surface of polyethersulfone membrane is 32 μg / cm 2 , and then heat treated in an oven at 60 °C for 3-5 min to obtain a MXene-MOF composite membrane.

[0082] Example 2 The preparation method of the rest of the MXene-MOF composite membrane is the same as that of Example 1 except for the following differences.

[0083] MXene nanosheets and quinone-coated MIL-101(Fe) were added to solvent water at a mass ratio of 1:5 to obtain a mixed solution, which was then loaded onto a vacuum filtration device with an effective area of ​​12.56 cm 2 The deposition amount of MXene nanosheets and quinone-coated MIL-101(Fe) on the surface of polyethersulfone membrane is 48 μg / cm 2 , and then heat treated in an oven at 60 °C for 3-5 min to obtain a MXene-MOF composite membrane.

[0084] Example 3 The preparation method of the rest of the MXene-MOF composite membrane is the same as that of Example 1 except for the following differences.

[0085] MXene nanosheets and quinone-coated MIL-101(Fe) were added to solvent water at a mass ratio of 1:7 to obtain a mixed solution, which was then loaded onto a vacuum filtration device with an effective area of ​​12.56 cm 2 The deposition amount of MXene nanosheets and quinone-coated MIL-101(Fe) on the surface of polyethersulfone membrane is 64 μg / cm 2 , and then heat treated in an oven at 60 °C for 3-5 min to obtain a MXene-MOF composite membrane.

[0086] Example 4 Except for the following differences, the preparation method of the remaining MXene-MOF composite membranes is the same as that of Example 1.

[0087] MXene nanosheets and quinone-coated MIL-101(Fe) were added to water as a solvent at a mass ratio of 1:1 to obtain a mixed solution. The mixed solution was loaded onto the surface of a polyethersulfone membrane with an effective area of 12.56 cm 2 through a vacuum filtration device, and the deposition amount of MXene nanosheets and quinone-coated MIL-101(Fe) on the surface of the polyethersulfone membrane was 25 μg / cm 2 , and then heat-treated in an oven at 60 °C for 3 - 5 min to obtain the MXene-MOF composite membrane.

[0088] Example 5 Except for the following differences, the preparation method of the remaining MXene-MOF composite membranes is the same as that of Example 1.

[0089] MXene nanosheets and quinone-coated MIL-101(Fe) were added to water as a solvent at a mass ratio of 1:9 to obtain a mixed solution. The mixed solution was loaded onto the surface of a polyethersulfone membrane with an effective area of 12.56 cm 2 through a vacuum filtration device, and the deposition amount of MXene nanosheets and quinone-coated MIL-101(Fe) on the surface of the polyethersulfone membrane was 80 μg / cm 2 , and then heat-treated in an oven at 60 °C for 3 - 5 min to obtain the MXene-MOF composite membrane.

[0090] Example 6 Except for the following differences, the preparation method of the remaining MXene-MOF composite membranes is the same as that of Example 2.

[0091] Preparation of MOF material: Dissolve 0.166 g of terephthalic acid (PTA) in 18 mL of N,N-dimethylformamide (DMF) solution, and ultrasonicate for 20 min to completely dissolve it to obtain a terephthalic acid (PTA) solution. Dissolve 0.270 g of FeCl 3 ·6H 2 O in 18 mL of N,N-dimethylformamide (DMF) solution, and ultrasonicate for 20 min to completely dissolve it to obtain an FeCl 3 ·6H 2 O solution. Subsequently, the terephthalic acid (PTA) solution was added to FeCl 3 ·6H 2O solution, stirring continuously for 1 hour to make it completely mixed. Pour the mixed solution into a high-pressure reactor and react at 110°C for 20 hours. After the reaction is completed, wash the MIL-101 (Fe) solid with anhydrous ethanol for at least 5 times and transfer it to a vacuum oven at 60°C to dry for 12 hours. Take 500 mg of the dried MIL-101 (Fe) powder and add it to the H 2 O 2 (5mmol / L) and CuSO 4 (5mmol / L) 100mL mixed solution. Then, 100mg of catechol was added to the mixture, and then ultrasonic treatment was performed for 1h. After the ultrasonic treatment, centrifugation, washing and drying were performed in the same way as MIL-101 (Fe) to obtain quinone-coated MIL-101 (Fe).

[0092] Example 7 The preparation method of the rest of the MXene-MOF composite membrane is the same as that of Example 2 except for the following differences.

[0093] Preparation of MOF materials: 0.166 g of terephthalic acid (PTA) was dissolved in 18 mL of N,N-dimethylformamide (DMF) solution and ultrasonicated for 20 min to completely dissolve it to obtain a terephthalic acid (PTA) solution. 3 6H 2 O was dissolved in 18 mL of N,N-dimethylformamide (DMF) solution and ultrasonicated for 20 min to completely dissolve it to obtain FeCl 3 6H 2 O solution. Subsequently, the terephthalic acid (PTA) solution was added with continuous stirring to FeCl 3 6H 2 O solution, stirring continuously for 1 hour to make it completely mixed. Pour the mixed solution into a high-pressure reactor and react at 110°C for 20 hours. After the reaction is completed, wash the MIL-101 (Fe) solid with anhydrous ethanol for at least 5 times and transfer it to a vacuum oven at 60°C to dry for 12 hours. Take 500 mg of the dried MIL-101 (Fe) powder and add it to the H 2 O 2 (10mmol / L) and CuSO 4 (5mmol / L) 100mL mixed solution. Then, 100mg of catechol was added to the mixture, and then ultrasonic treatment was performed for 150min. After the ultrasonic treatment, centrifugation, washing and drying were performed in the same way as MIL-101(Fe) to obtain quinone-coated MIL-101(Fe).

[0094] Comparative Example 1 The preparation method of the remaining MXene composite membranes is the same as that of Example 2 except for the following differences.

[0095] MXene nanosheets were added to solvent water to obtain a mixed solution, and the mixed solution was loaded on a vacuum filtration device with an effective area of ​​12.56 cm 2 The deposition amount of MXene nanosheets on the surface of polyethersulfone membrane is 8 μg / cm 2 , and then heat treated in an oven at 60 °C for 3-5 min to obtain a MXene composite film.

[0096] Comparative Example 2 The preparation method of the rest of the MXene-MOF composite membrane is the same as that of Example 2 except for the following differences.

[0097] Preparation of MOF materials: 0.166 g of terephthalic acid (PTA) was dissolved in 18 mL of N,N-dimethylformamide (DMF) solution and ultrasonicated for 20 min to completely dissolve it to obtain a terephthalic acid (PTA) solution. 3 6H 2 O was dissolved in 18 mL of N,N-dimethylformamide (DMF) solution and ultrasonicated for 20 min to completely dissolve it to obtain FeCl 3 6H 2 O solution. Subsequently, the terephthalic acid (PTA) solution was added with continuous stirring to FeCl 3 6H 2 O solution, and continued stirring for 1 hour to make it completely mixed. The mixed solution was poured into a high-pressure reactor and reacted at 110°C for 20 hours. After the reaction was completed, the MIL-101 (Fe) solid was washed with anhydrous ethanol for at least 5 times and transferred to a vacuum oven at 60°C for drying for 12 hours to obtain MIL-101 (Fe).

[0098] Test Section (1) Morphology testing of MXene nanosheets, MOF materials, and MXene-MOF composite films The morphological characteristics of MXene nanosheets, MOF materials and MXene-MOF composite films were observed by scanning electron microscopy (SEM).

[0099] (2) Testing of water flux and flux recovery rate Water flux The flux of a membrane is measured by recording the volume of water passing through the membrane in a certain time, where a certain volume of pure water passes through an effective area of ​​12.56 cm at a pressure of 1 bar. 2 separation membrane.

[0100] Before the formal test, the sample was compacted with pure water at a pressure of 1 bar for 10 minutes to reduce the error during the test. Water flux (J, in L·m -2 ·h -1 bar -1 )The calculation formula is as follows: J = V / (A×t×P) Where V (in L) is the volume of water collected within t (in h), A (in m 2 ) is the effective area of ​​the separation membrane, and P (in bar) is the pressure.

[0101] Light to Flux Recovery Rate Hexane / water emulsion was used as simulated wastewater, and after filtration, it was washed with water and washed with water + light treatment. The photocatalytic self-cleaning operation involves immersing the membrane that has filtered the simulated wastewater in a solution containing H 2 O 2 The membrane was then exposed to a xenon lamp (300W, >400nm) for 15 min and the water flux of the membrane was measured to demonstrate its photocatalytic self-cleaning ability. The flux recovery rate (FRR) was calculated by the following formula: FRR = F 0 / F 1 ×100% Where F0 and F1 represent the initial water flux and the water flux after photocatalytic self-cleaning of the composite membrane, respectively.

[0102] (3) Test of interception rate The oil phase concentration is 1%, which is emulsified oil. The specific preparation method is: by mixing different oils (n-hexane, cyclohexane, n-heptane, isooctane and petroleum ether) with water at a volume ratio of 1:99, and using 200 mg / L sodium dodecyl sulfate as a surfactant, and then stirring at 1200 rpm for 20 hours, and adding oil red to facilitate the measurement of the oil phase concentration, an oil-water emulsion is obtained.

[0103] The calculation formula of the retention rate of oil-water emulsion is as follows: R = (1 - C 1 / C 0 )×100% In the formula, C 0 and C 1 represent the concentration of oil in the feed emulsion and filtrate samples, respectively, and can be quantified by measuring the absorbance of the oil-water emulsion at 507 nm using an ultraviolet spectrophotometer (UV5100, China).

[0104] (4) Contact angle test Water contact angle The obtained composite film was cut into a 1 cm × 1 cm square, and the film surface was pasted on a glass slide with the film facing up and then placed on a contact angle meter. Deionized water was dropped onto the film surface with a 5 μL probe to measure its water contact angle, which was then analyzed using OneAttension software. The average value was taken after 5 measurements.

[0105] Underwater oil contact angle The obtained composite film was cut into a 1 cm × 1 cm square, and the film was pasted on a glass slide with the film surface facing up and placed in a glass container filled with ionized water. Then it was placed in a contact angle meter, and the oil phase was dropped onto the film surface with a 5 μL probe to measure its underwater oil contact angle, which was then analyzed using OneAttension software. The average value was taken after 5 measurements.

[0106] The test results of Examples 1-7 and Comparative Examples 1-2 are shown in Table 1.

[0107] Table 1

[0108] Table 2

[0109] From the test results in Table 1 and Table 2, it can be seen that the MXene-MOF composite membrane has good hydrophilicity and water permeability, the MXene-MOF composite membrane has both high pure water flux and retention rate, and the MXene-MOF composite membrane has excellent anti-pollution and photocatalytic self-cleaning properties. Figure 3 This is a scanning electron microscope (SEM) image of the surface of the MXene-MOF composite membrane prepared in Example 2. Figure 4 This is a scanning electron microscope (SEM) image of the cross-section of the MXene-MOF composite membrane prepared in Example 2.

[0110] Figure 5 This is a test diagram of the cyclic stability of the MXene-MOF composite film prepared in Example 2 under visible light irradiation. Figure 5 It can be seen that the MXene-MOF composite membrane still has a high flux and retention rate after 10 cycles of visible light irradiation, that is, the MXene-MOF composite membrane has excellent anti-pollution and photocatalytic self-cleaning properties.

[0111] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application is described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A MXene-MOF composite membrane, characterized in that: The MXene-MOF composite film includes a base film, and MXene nanosheets and MOF materials located on one surface of the base film; The MXene nanosheets include single-layer nanosheets, and the MOF material is located between the sheets of the MXene nanosheets and on the surface of the MXene nanosheets; the MOF material includes quinone-coated MIL-101 (Fe); The mass ratio of the MXene nanosheets to the MOF material is 1:(1-9).

2. The MXene-MOF composite membrane according to claim 1, characterized in that The deposition amount of the MXene nanosheets and the MOF material on the surface of the base film is 1-100 μg / cm 2 .

3. The MXene-MOF composite membrane according to claim 1, characterized in that The MXene nanosheets include Ti3C2T x and / or, The base film includes any one of a polyvinylidene fluoride film, a polyethersulfone film, a polysulfone film, and a polyethylene film.

4. The MXene-MOF composite membrane according to claim 1, characterized in that The lateral size of the MXene nanosheet is 8-10 μm, and the thickness of the MXene nanosheet is 1-3 nm; and / or, The average particle size of the MOF material is 220-300 nm.

5. A method for preparing the MXene-MOF composite membrane according to any one of claims 1 to 4, characterized in that: The preparation method comprises: Provide MXene nanosheets and MOF materials; A mixed solution including the MXene nanosheets and the MOF material is deposited on one side surface of the base film by vacuum assisted filtration to obtain a MXene-MOF composite film.

6. The preparation method according to claim 5, characterized in that: The step of providing MXene nanosheets and MOF materials comprises: Performing HCl-LiF system wet chemical etching and organic solvent-assisted intercalation on the MAX powder to obtain the MXene nanosheets; and / or, Quinone-coated MIL-101(Fe) was obtained by mixing catechol with MIL-101(Fe) and then oxidizing it by ultrasound-assisted oxidation. The mass ratio of the catechol to the MIL-101(Fe) is 1:(4-6); The ultrasonic treatment time in the ultrasonic-assisted oxidation is 50-70 minutes.

7. The preparation method according to claim 5, characterized in that: The step of depositing a mixed solution including MXene nanosheets and MOF materials on one side of the base film by vacuum assisted filtration comprises: Prior to the vacuum-assisted filtration, the mixed solution including the MXene nanosheets and the MOF material is subjected to ultrasonic treatment.

8. The preparation method according to claim 5, characterized in that: The oxidant of the ultrasonic assisted oxidation includes H2O2; the catalyst of the ultrasonic assisted oxidation includes CuSO4; The concentration of the CuSO4 is 8-12 mmol / L, and the concentration of the H2O2 is 3-7 mmol / L.

9. The preparation method according to claim 5, characterized in that: The preparation method further comprises: pre-treating the base film before assembling, wherein the pre-treatment comprises ultrasonic treatment; and / or, The preparation method further comprises: heat treating the assembled MXene-MOF composite film, wherein the heat treatment temperature is 55° C.-65° C., and the heat treatment time is 3-5 min.

10. Use of the MXene-MOF composite membrane according to any one of claims 1 to 4 in wastewater treatment.

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