A super-permeable separation membrane, a preparation method and application thereof

Abstract

The application discloses an ultra-permeation separation membrane and a preparation method and application thereof. The ultra-permeation separation membrane is assembled by a hydrophobic molecular shell layer and an ultra-fast transmission layer. The membrane can be used for enriching low-concentration organic products such as alcohols in water.

Description

Technical Field

[0001] This invention relates to an ultrapermeable separation membrane, its preparation method and application, belonging to the field of materials and chemical separation. Background Technology

[0002] The excessive consumption of fossil fuels has led to environmental degradation and energy depletion, making the search for renewable and sustainable energy resources an urgent priority. Bio-based platform compounds (such as polyols and furans) prepared through biorefining technology can serve as raw materials for constructing various biofuels and high-value chemicals, thus opening up the biomass chain economy. However, the separation of bio-based platform compounds still faces significant challenges. These compounds mainly originate from the acid-catalyzed hydrolysis of carbohydrates, are produced in dilute aqueous solutions, and have high boiling points. Traditional separation methods (such as distillation, stripping, and vapor phase adsorption) involve phase changes of the components to be separated, resulting in complex processes and high energy consumption. In contrast, pervaporation membrane separation is more energy-efficient and suitable for the efficient separation of bio-based platform compounds. Utilizing pervaporation membranes for the efficient enrichment of low-concentration organic products such as alcohols in water requires further optimization of both membrane construction materials and membrane structure construction methods.

[0003] In the field of membrane materials, metal-organic frameworks (MOFs) are a class of highly ordered porous organic-inorganic hybrid materials formed by the coordination of metal ions (clusters) and organic ligands. Zeolitic imidazolate frameworks (ZIFs), as a subclass of MOFs, are widely used in separation applications due to their unique thermal stability, chemical stability, and microporous properties. To further modulate the framework structure and physicochemical properties of ZIF materials to optimize their application potential in separation systems (Eum K. JACS, 2015, 137:4191), recent reports have described the preparation of dual-ligand ZIF materials by introducing another ligand into the existing ZIF structure for the growth of polycrystalline membranes, thus improving the permeability of propylene molecules in propylene / propane separation systems (Hillman F. ACS Appl. Mater. Interface, 2019, 11:18377). The synthesis of biligand materials using mixed ligands offers new design ideas for the regulation of the material's framework and physicochemical properties, and is expected to provide new opportunities for applications in the field of separation membrane construction.

[0004] In the construction of separation membranes, the construction of the membrane structure is another key to achieving superior organophilic properties. Traditional pervaporation membrane materials used for preferentially permeating organic matter mainly include inorganic molecular sieve membrane materials, organic polymer membrane materials, and organic-inorganic hybrid membrane materials. Although inorganic molecular sieve membranes have good thermal stability, chemical stability, and mechanical strength, the preparation of complete, continuous, and dense molecular sieve membranes requires high precision in terms of processes and substrates. Organic polymer materials have advantages such as good flexibility and film-forming properties, high selectivity, a wide variety, simple preparation processes, and relatively mature technologies, but their stability and mechanical strength still need further improvement. Organic-inorganic hybrid membranes refer to mixed matrix membranes (MMMs) obtained by adding inorganic particles to an organic matrix. They can effectively combine the advantages of both and represent one of the main development directions in the field of pervaporation membrane separation. However, the formation of interfacial defects at the interface of mixed matrix membranes can lead to unsatisfactory separation performance, thus restricting the development of organic-inorganic hybrid membranes for enriching organic matter. Summary of the Invention

[0005] The purpose of this invention is to provide an ultrapermeable separation membrane, its preparation method, and its application. The ultrapermeable separation membrane proposed in this invention divides the membrane structure into an affinity molecular surface layer based on organic polymers and an ultrafast transport layer based on dual-ligand metal-organic framework materials. By using a deconstruction-assembly construction approach, the generation of interface defects is avoided, thereby optimizing the enrichment and separation performance of the membrane.

[0006] An ultrapermeable separation membrane is provided, comprising an affinity molecular surface layer (hydrophobic molecular shell) and an ultrafast transport layer, wherein the affinity molecular surface layer is located outside the ultrafast transport layer.

[0007] Based on the above technical solutions, furthermore, the affinity molecule surface layer is a cross-linked polysiloxane or an ionic liquid.

[0008] Based on the above technical solution, furthermore, the thickness of the affinity molecule surface layer is 0-50 nm, and is not 0.

[0009] Based on the above technical solutions, the ultrafast transport layer is further defined as a continuous nanoparticle layer of dual-ligand metal-organic framework material with a particle size of 10-1000nm (preferably 800-2000nm) or a stacked layer of dual-ligand metal-organic framework nanosheets with a thickness of 1-100nm (preferably 50-100nm).

[0010] This invention also relates to a method for preparing the above-mentioned superpermeable separation membrane, comprising the following steps:

[0011] (1) The dual-ligand metal-organic framework material (dual-ligand MOF material) is fully dispersed in butanol to prepare a dispersion, denoted as solution A, for later use; silicone rubber (hydroxyl polymethylphenylsiloxane) is dissolved in butanol and stirred thoroughly to prepare a silicone rubber solution, denoted as solution B, for later use; solutions A and B are mixed evenly in an ice-water bath to obtain a mixed matrix film casting solution; wherein, the mass ratio of silicone rubber, butanol and dual-ligand metal-organic framework material is 1:2~10:0.1~0.8; the casting solution is prepared by blending the dual-ligand metal-organic framework material as filler particles with silicone rubber;

[0012] (2) The mixed matrix membrane casting solution is coated onto the alumina base membrane to obtain the mixed matrix membrane; an ultrafast transport layer based on a dual-ligand metal-organic framework material is constructed, and the mixed matrix membrane will undergo a subsequent crosslinking reaction in the next step.

[0013] (3) The mixed matrix membrane is placed in an isooctane solution containing silane coupling agent and catalyst for interfacial crosslinking at a temperature of 15-30°C for a time of 0.5-72h, preferably 24h; during this process, the affinity molecule surface layer is assembled through crosslinking.

[0014] Based on the above technical solution, further, in step (1), the preparation method of the dual-ligand type metal-organic framework material includes the following steps:

[0015] One of the divalent zinc or cobalt nitrates, acetates, or halides is dissolved in anhydrous methanol and stirred until homogeneous to obtain a metal solution, which is then set aside. 2-Methylimidazole and 4,5-dichloroimidazole are simultaneously dissolved in anhydrous methanol and stirred until homogeneous to obtain a dual-ligand solution, which is then set aside. The metal solution and the dual-ligand solution are mixed and reacted at 20–30°C (preferably 23–25°C) for 0.5–24 hours (preferably 2 hours). The resulting product is centrifuged and washed with anhydrous methanol to obtain a dual-ligand metal-organic framework material; wherein the molar ratio of the divalent zinc or cobalt ions to the total amount of 2-methylimidazole and 4,5-dichloroimidazole is 1:2.

[0016] Based on the above technical solution, furthermore, the concentration of the metal solution is 0.007–0.1 g / ml, preferably 0.007–0.01 g / ml; the concentration of the dual-ligand solution is 1*10 -5 ~0.2g / ml, preferably 1*10 -5 ~0.02g / ml.

[0017] Based on the above technical solution, further, the molar ratio of the divalent metal zinc or cobalt, 2-methylimidazole and 4,5-dichloroimidazole is 1:1:1.

[0018] Based on the above technical solution, further, in step (1), the preparation method of liquid A is as follows: add solid particles (dual-ligand type metal-organic framework material) to butanol, and fully disperse by ultrasonication in a water bath for 1.5 hours to prepare a dispersion.

[0019] Based on the above technical solution, further, in step (1), the preparation method of the mixed matrix membrane casting solution is as follows: 3-5 drops of solution B are added to solution A for pre-wetting, and solution A is further dispersed evenly by ultrasonic dispersion using a probe ultrasonic instrument under an ice-water bath. Then, all of the solution A after ultrasonic treatment by the probe is added to the remaining solution B while stirring. The resulting AB mixture is then further dispersed by ultrasonic dispersion using a probe ultrasonic instrument under an ice-water bath to obtain the mixed matrix membrane casting solution.

[0020] Based on the above technical solution, further, in step (2), the thickness of the alumina base film is 1-2 mm, and the coating method is dip-coating, spin coating or scraping coating.

[0021] Based on the above technical solutions, a further temperature-controlled multilayer immersion-coating machine is used to construct an ultrafast transport layer based on a dual-ligand metal-organic framework material using the immersion-coating method. The alumina-based film is immersed in the above-obtained mixed matrix film casting solution and then pulled. The immersion speed is 1-8 mm / s, preferably 1-6 mm / s; the immersion time is 10-60 s, preferably 10-20 s; and the pulling speed is 1-8 mm / s, preferably 1-6 mm / s.

[0022] Based on the above technical solution, further, in step (3), the silane coupling agent is tetraethoxysilane, the catalyst is dibutyltin dilaurate, and the mass ratio of silane coupling agent, catalyst and isooctane in the isooctane solution containing silane coupling agent and catalyst is 1:1 to 5:10 to 50, preferably 1:1.3:33.

[0023] The present invention also relates to protecting the above-mentioned superpermeable separation membrane for the enrichment of organic products of low concentrations of alcohols or aldehydes in aqueous solutions.

[0024] Based on the above technical solution, further, the mass concentration of the low-concentration alcohol or aldehyde in water is 0.01-10%, the alcohol includes methanol, ethanol or butanol, and the aldehyde includes furfural.

[0025] This invention prepares dual-ligand MOF materials through a one-pot reaction at 20–30°C. The prepared dual-ligand MOF materials are ideal raw materials for membrane construction, showing good application potential in the field of separation. Moreover, the preparation method is simple and the conditions are mild. The preparation method provided by this invention is universally applicable to other hybrid MOF materials.

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] (1) The preparation process is low in energy consumption and simple, and is a convenient chemical synthesis method;

[0028] (2) The experimental design is ingenious. By introducing ligands with different topological structures, dual-ligand hybrid MOF superpermeable membranes were designed and synthesized, which broadened the construction ideas of hybrid MOF membranes and has certain guiding significance for other hybrid MOF materials.

[0029] (3) The superpermeable membrane in this invention has a high permeability, which is expected to meet the actual application needs of the pervaporation separation industry and has good application prospects. Attached Figure Description

[0030] This invention appendix Figure 5 Size:

[0031] Figure 1 The X-ray diffraction patterns of ZIF-8-71-1-1 powder and ZIF-8 and ZIF-71 in Example 1 are shown.

[0032] Figure 2 This is a SEM image of the ZIF-8-71-1-1 powder material in Example 1.

[0033] Figure 3 This is a surface SEM image of the ultrapermeable membrane based on ZIF-8-71-1-1 powder in Example 1.

[0034] Figure 4 This is a cross-sectional SEM image of the ultrapermeable membrane based on ZIF-8-71-1-1 powder in Example 1.

[0035] Figure 5 This is a schematic diagram of the apparatus used to test the separation performance of the ultrapermeable membrane in the embodiment. Detailed Implementation

[0036] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0037] Example 1. Synthesis of ZIF-8-71-1-1, a dual-ligand material with a ligand molar ratio of 2-methylimidazole:4,5-dichloroimidazole = 1:1, and preparation of a superpermeable membrane loaded with 30% ZIF-8-71-1-1 particles and crosslinked for 1 hour.

[0038] Weigh 0.7 g of zinc nitrate hexahydrate (Sigma-Aldrich, ≥98%) and dissolve it in 90 ml of anhydrous methanol, stirring until dissolved to obtain solution 1. Weigh 0.19 g of 2-methylimidazole (Sigma-Aldrich, ≥98%) and 0.3 g of 4,5-dichloroimidazole (Sigma-Aldrich, ≥98%) and dissolve them in 90 ml of anhydrous methanol, stirring until dissolved to obtain solution 2. Slowly add solution 1 dropwise to solution 2 while stirring continuously, and react at 25 °C for 2 h. After the reaction is complete, transfer the suspension to a centrifuge tube for centrifugation, wash three times with anhydrous methanol, and dry overnight in a 60 °C oven to obtain product ZIF-8-71-1-1.

[0039] 1.026 g of zinc nitrate hexahydrate (Sigma-Aldrich, ≥98%) was dissolved in 70 ml of methanol. The resulting solution was added to 70 ml of a methanol solution containing 2.072 g of 2-methylimidazole, and the mixture was reacted at 25 °C for 1 h. After the reaction was complete, the suspension was transferred to a centrifuge tube and centrifuged. The suspension was washed three times with anhydrous methanol and then dried overnight in a 60 °C oven to obtain the product ZIF-8.

[0040] 0.446 g of zinc acetate dihydrate (Sigma-Aldrich, ≥98%) was dissolved in 90 ml of methanol. The resulting solution was added to 90 ml of a methanol solution containing 1.315 g of 4,5-dichloroimidazole, and the mixture was reacted at 25 °C for 24 h. After the reaction was complete, the suspension was transferred to a centrifuge tube and centrifuged. The suspension was washed three times with anhydrous methanol and then dried overnight in a 60 °C oven to obtain the product ZIF-71.

[0041] The morphology and structure of the dual-ligand MOF material prepared in this invention were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), and compared with the morphology and structure of ZIF-8 and ZIF-71. The results are as follows:

[0042] Figure 1 X-ray diffraction patterns of ZIF-8-71-1-1 powder, ZIF-8, and ZIF-71 in Example 1 are given. The patterns show that the synthesized material exhibits an RHO crystal phase similar to that of ZIF-71.

[0043] Figure 2 The image shows a SEM image of the ZIF-8-71-1-1 powder material from Example 1. SEM results indicate that the synthesized ZIF-8-71-1-1 powder has a cubic morphology with surface-attached nanoparticles, and a particle size of approximately 1.5 μm.

[0044] The ZIF-8-71-1-1 powder material synthesized using the above method was prepared as a 10% (w / w) butanol dispersion without drying. This dispersion was then ultrasonically dispersed in a water bath for 1.5 hours to form a suspension. 4.5g of this suspension was weighed and designated as solution A for later use. Separately, 1.5g of silicone rubber (hydroxyl polymethylphenylsiloxane) was dissolved in 5.95g of butanol and thoroughly stirred to prepare a silicone rubber solution, designated as solution B for later use.

[0045] Subsequently, 0.15 ml of solution B was added to solution A for pre-wetting. Solution A was then ultrasonically dispersed for 5 minutes in an ice-water bath using a probe ultrasonic instrument to further disperse it evenly. Then, all of the solution A after the probe ultrasonic treatment was added to the remaining solution B while stirring. The resulting AB mixture was then ultrasonically dispersed for 10 minutes in an ice-water bath using a probe ultrasonic instrument to obtain a mixed matrix film casting solution, wherein the mass ratio of silicone rubber:butanol:dual-ligand metal-organic framework material particles was 1:6.67:0.3.

[0046] An alumina-based membrane with a diameter of 18 mm and a thickness of 1 mm was immersed in the AB mixture obtained above and then pulled. The immersion speed was 1 mm / s, the immersion time was 10 s, and the pulling speed was 1 mm / s. The mixed matrix membrane obtained by pulling in the casting solution was placed in an isooctane solution of tetraethoxysilane and dibutyltin dilaurate (prepared from 0.3 g tetraethoxysilane, 0.4 g dibutyltin dilaurate, and 10 g isooctane) for interfacial crosslinking to assemble the affinity molecular surface layer. The reaction temperature was 20 °C, and the reaction time was 1 h. Three superpermeable membranes were prepared in parallel using the above steps for performance testing.

[0047] Figure 3 The SEM image of the superpermeable membrane based on ZIF-8-71-1-1 powder in Example 1 is given, showing that the prepared superpermeable membrane has no obvious defects.

[0048] Figure 4 A cross-sectional SEM image of the superpermeable membrane based on ZIF-8-71-1-1 powder in Example 1 is provided, showing that the thickness of the prepared superpermeable membrane is approximately 3.76 micrometers.

[0049] The ability of the superpermeable membrane based on ZIF-8-71-1-1 powder to enrich n-butanol from aqueous solution was tested using a pervaporation method to evaluate its separation performance. The pervaporation apparatus used was as follows: Figure 5As shown, the feed solution in the three-necked flask during the test was n-butanol / water, i.e., a dilute aqueous solution of n-butanol with a mass fraction of 1.0 wt.%, and the test temperature was 80℃. The superpermeable membrane was encapsulated with rubber O-rings in the membrane module shown in the figure and extended approximately 1 cm below the surface of the feed solution. A permeate vacuum was maintained on the back side of the membrane by an oil pump. The permeate was collected at specific time intervals in a liquid nitrogen cold trap and the permeate components were analyzed by gas chromatography (7890 BAgilent). The enrichment and separation performance of the membrane was evaluated using the following parameters. The performance test results of the three parallel membrane sheets are shown in Table 1 below. The test results show that the superpermeable membrane has excellent permeability.

[0050]

[0051]

[0052] In formula (1), J: total flux (kg m³) -2 h -1 )

[0053] W: Permeate mass (kg); Δt: Sampling interval (h); A: Effective separation membrane area (m²) 2 This parameter is used to evaluate the membrane's permeability.

[0054] In formula (2), SF i / H2O Separation factor of component i

[0055] Yi: Mass fraction of component i in the permeate; Xi: Mass fraction of component i in the feed solution; Y H2O : Mass fraction of water in the permeate; X H2O : The mass fraction of water in the feed solution; Yi and Xi represent the mass fractions of component i in the permeate and feed solution, respectively. This parameter is used to evaluate the separation selectivity of the membrane.

[0056] Table 1

[0057]

[0058] Example 2. Synthesis of ZIF-8-71-1-1, a dual-ligand material with a ligand molar ratio of 2-methylimidazole:4,5-dichloroimidazole = 1:1, and preparation of a superpermeable membrane loaded with 30% ZIF-8-71-1-1 particles and crosslinked for 24 hours.

[0059] Weigh 0.7 g of zinc nitrate hexahydrate (Sigma-Aldrich, ≥98%) and dissolve it in 90 ml of anhydrous methanol. Stir to dissolve and prepare solution 1. Weigh 0.19 g of 2-methylimidazole (Sigma-Aldrich, ≥98%) and 0.3 g of 4,5-dichloroimidazole (Sigma-Aldrich, ≥98%) and dissolve them in 90 ml of anhydrous methanol. Stir to dissolve and prepare solution 2. Slowly add solution 1 to solution 2 while stirring continuously. React at 25°C for 2 hours. After the reaction is complete, transfer the suspension to a centrifuge tube and centrifuge. Wash the product ZIF-8-71-1-1 particles three times with anhydrous methanol to obtain a 10% (w / w) butanol dispersion. Sonicate the dispersion in a water bath for 1.5 hours to fully disperse the particles into a suspension. Weigh 4.5 g of the suspension and designate it as solution A. Alternatively, 1.5g of silicone rubber (hydroxyl polymethylphenylsiloxane) is dissolved in 5.95g of butanol and stirred thoroughly to prepare a silicone rubber solution, which is designated as solution B for later use.

[0060] Subsequently, 0.15 ml of solution B was added to solution A for pre-wetting. Solution A was then ultrasonically dispersed for 5 minutes in an ice-water bath using a probe ultrasonic instrument to further disperse it evenly. Then, all of the solution A after the probe ultrasonic treatment was added to the remaining solution B while stirring. The resulting AB mixture was then ultrasonically dispersed for 10 minutes in an ice-water bath using a probe ultrasonic instrument to obtain a mixed matrix film casting solution, wherein the mass ratio of silicone rubber:butanol:dual-ligand metal-organic framework material particles was 1:6.67:0.3.

[0061] An alumina-based membrane with a diameter of 18 mm and a thickness of 1 mm was immersed in the AB mixture obtained above and then pulled. The immersion speed was 1 mm / s, the immersion time was 10 s, and the pulling speed was 1 mm / s. The mixed matrix membrane obtained by pulling in the casting solution was placed in an isooctane solution of tetraethoxysilane and dibutyltin dilaurate (prepared from 0.3 g tetraethoxysilane, 0.4 g dibutyltin dilaurate, and 10 g isooctane) for interfacial crosslinking to assemble the affinity molecular surface layer. The reaction temperature was 20 °C, and the reaction time was 24 h. Three superpermeable membranes were prepared in parallel using the above steps for performance testing. The testing method was the same as in Example 1.

[0062] The performance test results of the three parallel membrane sheets are shown in Table 2 below. The test results show that the superpermeable membrane with a cross-linking reaction time of 24h also has excellent permeability.

[0063] Table 2

[0064]

[0065] Example 3. Synthesis of ZIF-8-71-1-1, a dual-ligand material with a ligand molar ratio of 2-methylimidazole:4,5-dichloroimidazole = 1:1, and preparation of a superpermeable membrane loaded with 50% ZIF-8-71-1-1 particles and crosslinked for 1 hour.

[0066] Weigh 0.14 g of zinc nitrate hexahydrate (Sigma-Aldrich, ≥98%) and dissolve it in 180 ml of anhydrous methanol. Stir until dissolved to obtain solution 1. Weigh 0.38 g of 2-methylimidazole (Sigma-Aldrich, ≥98%) and 0.6 g of 4,5-dichloroimidazole (Sigma-Aldrich, ≥98%) and dissolve them in 180 ml of anhydrous methanol. Stir until dissolved to obtain solution 2. Slowly add solution 1 dropwise to solution 2 while stirring continuously. React at 25°C for 2 hours. After the reaction, transfer the suspension to a centrifuge tube and centrifuge. Wash the product ZIF-8-71-1-1 particles three times with anhydrous methanol to obtain a 10% (w / w) butanol dispersion. Sonicate the dispersion in a water bath for 1.5 hours to fully disperse the particles into a suspension. Weigh 7.5 g of the suspension and designate it as solution A. Alternatively, dissolve 1.5g of silicone rubber (hydroxyl polymethylphenylsiloxane) in 3.25g of butanol, stir thoroughly to prepare a silicone rubber solution, and designate it as solution B for later use.

[0067] Subsequently, 0.15 ml of solution B was added to solution A for pre-wetting. Solution A was then ultrasonically dispersed for 5 minutes in an ice-water bath using a probe ultrasonic instrument to further disperse it evenly. Then, all of the solution A after the probe ultrasonic treatment was added to the remaining solution B while stirring. The resulting AB mixture was then ultrasonically dispersed for 10 minutes in an ice-water bath using a probe ultrasonic instrument to obtain a mixed matrix film casting solution, wherein the mass ratio of silicone rubber:butanol:dual-ligand metal-organic framework material particles was 1:6.67:0.5.

[0068] An alumina-based membrane with a diameter of 18 mm and a thickness of 1 mm was immersed in the AB mixture obtained above and then pulled. The immersion speed was 1 mm / s, the immersion time was 10 s, and the pulling speed was 1 mm / s. The mixed matrix membrane obtained by pulling in the casting solution was placed in an isooctane solution of tetraethoxysilane and dibutyltin dilaurate (prepared from 0.3 g tetraethoxysilane, 0.4 g dibutyltin dilaurate, and 10 g isooctane) for interfacial crosslinking to assemble the affinity molecular surface layer. The reaction temperature was 20 °C, and the reaction time was 1 h, resulting in a superpermeable membrane loaded with 50% ZIF-8-71-1-1 particulate material and with a crosslinking time of 1 h. Three superpermeable membranes were prepared in parallel using the above steps for performance testing. The testing method was the same as in Example 1.

[0069] The performance test results of the three parallel membranes are shown in Table 3 below. The test results show that the superpermeable membrane with a crosslinking reaction time of 1 h and 50% loaded with dual-ligand MOF particles also has excellent permeability.

[0070] Table 3

[0071]

[0072]

[0073] Example 4. Synthesis of a dual-ligand material ZIF-8-71-0.5-1.5 with a ligand molar ratio of 2-methylimidazole:4,5-dichloroimidazole = 0.5:1.5, and preparation of a superpermeable membrane loaded with 30% ZIF-8-71-0.5-1.5 particles and crosslinked for 1 h.

[0074] Weigh 0.53 g of zinc acetate dihydrate (Sigma-Aldrich, ≥98%) and dissolve it in 90 ml of anhydrous methanol. Stir to dissolve and prepare solution 1. Weigh 0.1 g of 2-methylimidazole (Sigma-Aldrich, ≥98%) and 0.5 g of 4,5-dichloroimidazole (Sigma-Aldrich, ≥98%) and dissolve them in 90 ml of anhydrous methanol. Stir to dissolve and prepare solution 2. Slowly add solution 1 to solution 2 while stirring continuously. React at 25°C for 2 hours. After the reaction is complete, transfer the suspension to a centrifuge tube and centrifuge. Wash the product ZIF-8-71-0.5-1.5 particles three times with anhydrous methanol to obtain a 10% (w / w) butanol dispersion. Sonicate the dispersion in a water bath for 1.5 hours to fully disperse the particles into a suspension. Weigh 4.5 g of the suspension and designate it as solution A. Alternatively, 1.5g of silicone rubber (hydroxyl polymethylphenylsiloxane) is dissolved in 5.95g of butanol and stirred thoroughly to prepare a silicone rubber solution, which is designated as solution B for later use.

[0075] Subsequently, 0.15 ml of solution B was added to solution A for pre-wetting. Solution A was then ultrasonically dispersed for 5 minutes in an ice-water bath using a probe ultrasonic instrument to further disperse it evenly. Then, all of the solution A after the probe ultrasonic treatment was added to the remaining solution B while stirring. The resulting AB mixture was then ultrasonically dispersed for 10 minutes in an ice-water bath using a probe ultrasonic instrument to obtain a mixed matrix film casting solution, wherein the mass ratio of silicone rubber:butanol:dual-ligand metal-organic framework material particles was 1:6.67:0.3.

[0076] An alumina-based membrane with a diameter of 18 mm and a thickness of 1 mm was immersed in the AB mixture obtained above and then pulled. The immersion speed was 1 mm / s, the immersion time was 10 s, and the pulling speed was 1 mm / s. The mixed matrix membrane obtained by pulling in the casting solution was placed in an isooctane solution of tetraethoxysilane and dibutyltin dilaurate (prepared from 0.3 g tetraethoxysilane, 0.4 g dibutyltin dilaurate, and 10 g isooctane) for interfacial crosslinking to assemble the affinity molecular surface layer. The reaction temperature was 20 °C, and the reaction time was 1 h, resulting in a superpermeable membrane loaded with 30% ZIF-8-71-0.5-1.5 particulate material and with a crosslinking time of 1 h. Three superpermeable membranes were prepared in parallel using the above steps for performance testing. The testing method was the same as in Example 1.

[0077] The performance test results of the three parallel membrane sheets are shown in Table 4 below. The test results show that the superpermeable membrane loaded with 30% ZIF-8-71-0.5-1.5 particulate material and with a crosslinking time of 1 hour also has excellent permeability.

[0078] Table 4

[0079]

Claims

1. A superpermeable separation membrane, characterized in that, The ultrapermeable separation membrane comprises an affinity molecular surface layer and an ultrafast transport layer; The affinity molecule surface layer is a cross-linked polysiloxane or an ionic liquid; The thickness of the affinity molecule surface layer is 0~50 nm, and is not 0; The ultrafast transport layer is a continuous nanoparticle layer of dual-ligand metal-organic framework material with a particle size of 10-1000 nm or a stacked layer of dual-ligand metal-organic framework nanosheets with a thickness of 1-100 nm; the ultrafast transport layer also contains silicone rubber. The preparation method of the dual-ligand metal-organic framework material includes the following steps: (1) Dissolve one of the nitrate, acetate or halide salts of divalent metal zinc or cobalt in anhydrous methanol and stir until homogeneous to obtain a metal solution; (2) Dissolve 2-methylimidazole and 4,5-dichloroimidazole in anhydrous methanol and stir until homogeneous to obtain a dual-ligand solution; (3) The metal solution obtained in step (1) is mixed with the dual-ligand solution obtained in step (2), and the product is centrifuged after reacting at 20~30℃ for 0.5~24 hours. The product is washed with anhydrous methanol to obtain a dual-ligand metal-organic framework material; wherein the molar ratio of the divalent zinc or cobalt ions to the total of 2-methylimidazole and 4,5-dichloroimidazole is 1:

2.

2. The method for preparing the ultrapermeable separation membrane according to claim 1, characterized in that, Includes the following steps: (1) The dual-ligand metal-organic framework material is dispersed in butanol to prepare a dispersion, denoted as solution A; silicone rubber is dissolved in butanol to prepare a silicone rubber solution, denoted as solution B; solutions A and B are mixed evenly in an ice-water bath to obtain a mixed matrix film casting solution; wherein, the mass ratio of silicone rubber, butanol and dual-ligand metal-organic framework material is 1:2~10:0.1~0.8; (2) The mixed matrix film casting solution is coated onto the alumina base film to obtain the mixed matrix film; (3) The mixed matrix membrane is placed in an isooctane solution containing silane coupling agent and catalyst for interfacial crosslinking at a temperature of 15~30℃ for 0.5h~72h.

3. The preparation method according to claim 2, characterized in that, In step (1), the silicone rubber is hydroxyl polymethylphenylsiloxane. The preparation method of the mixed matrix membrane casting solution is as follows: 3-5 drops of solution B are added to solution A and ultrasonically dispersed evenly under an ice-water bath. Then, all of solution A is added to the remaining solution B while stirring and ultrasonically dispersed evenly to obtain the mixed matrix membrane casting solution. In step (2), the coating method is dip-coating, spin coating, or scraping coating; In step (3), the silane coupling agent is tetraethoxysilane, the catalyst is dibutyltin dilaurate, and the mass ratio of silane coupling agent, catalyst and isooctane in the isooctane solution containing silane coupling agent and catalyst is 1:1~5:10~50.

4. The preparation method according to claim 3, characterized in that, The immersion-pulling method specifically involves immersing and pulling an alumina-based film in a mixed matrix film casting solution. The immersion speed is 1-8 mm / s, the immersion time is 1-60 s, and the pulling speed is 1-8 mm / s.

5. The application of the superpermeable separation membrane according to claim 1 in the enrichment of low concentrations of organic products such as alcohols or aldehydes in water.

6. The application according to claim 5, characterized in that, The low concentration alcohol or aldehyde has a mass concentration of 0.01-10% in water, wherein the alcohol includes methanol, ethanol or butanol, and the aldehyde includes furfural.

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