Graphyne multilayer composite film and preparation method thereof

Abstract

The application discloses a kind of graphdiyne multilayer composite membrane and preparation method thereof, belong to membrane separation and technical field.Porous base membrane with acetylenic group layer is obtained by two-step modification method, then it is immersed in solution containing graphdiyne monomer and catalyst, and reaction is carried out at a certain temperature, so that graphdiyne material is fully grown on the surface of porous base membrane.Then casting solution of organic polymer, crosslinking agent, catalyst and organic solvent is added to the surface of porous base membrane loaded with graphdiyne, and after the organic solvent is volatilized, it is cured into film at 80 DEG C.The preferential alcohol permeation membrane of the application has a three-layer film structure: organic polymer layer, ultrathin graphdiyne transition layer and porous support layer, effectively avoiding the agglomeration and pore penetration problem of nanomaterial, further strengthening the adsorption process of ethanol.The prepared membrane has high pervaporation alcohol permeation performance, can efficiently and stably recover alcohol, and provides a reference for the development of novel preferential alcohol pervaporation membrane structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of membrane separation and technology, and particularly relates to a graphdiyne multilayer composite membrane and a preparation method thereof. BACKGROUND

[0002] In recent years, bioethanol recovered from biological fermentation has received extensive attention due to its characteristics of alleviating the shortage of fossil energy and further deterioration of the environment and clean recyclability. However, the low product concentration in the fermentation broth often leads to high energy consumption in the bioethanol recovery process. Pervaporation (PV) is considered as an alternative technology for bioethanol recovery. However, due to the persistent lack of robust and high-performance membrane materials, the development of preferential alcohol pervaporation membranes has been lagging behind.

[0003] Polydimethylsiloxane (PDMS) is one of the most widely used membrane materials in preferential alcohol pervaporation membranes, but its separation performance is often limited by the "trade-off" phenomenon between permeability and selectivity. To address this challenge, composite membranes and mixed matrix membranes (MMMs) have been proposed by adding porous fillers to the polymer to adjust the stacking of polymer chains and provide more adsorption sites for permeable molecules, thereby improving the permeation selectivity. So far, various nanomaterials such as metal organic frameworks (MOFs), covalent organic frameworks (COFs), zeolites and carbon nanotubes (CNTs) have been applied for filling.

[0004] However, the preparation methods of loading porous fillers on the membrane surface are mostly blended with polymers, which often leads to phenomena such as nanoparticle agglomeration, polymer pore penetration, etc., seriously affecting the performance of mixed matrix membranes. In the preparation process of pervaporation membranes, reducing agglomeration and pore penetration is one of the most effective ways to improve the separation performance of membranes. Therefore, it is of great significance for selective ethanol recovery to design a membrane that can avoid both particle agglomeration and polymer pore penetration.

[0005] Meanwhile, graphdiyne is a new two-dimensional carbon allotrope formed by sp and sp 2 hybridized carbon atoms connected by covalent bonds. It has the characteristics of structural order, hexagonal pore type and excellent thermal and chemical stability, and its inherent porous system can provide a relatively short transport path for molecules, which is conducive to enhancing the permeation flux.

[0006] Based on the above analysis, the application grows two-dimensional graphdiyne nanomaterial on the substrate in situ to form an ultrathin graphdiyne transition layer, and impregnates an organic polymer, to prepare a composite film with a unique transition layer structure. The transition layer effectively avoids the agglomeration of nanomaterial and the pore penetration of the polymer, and further enhances the adsorption process of ethanol. The recovery of alcohol is realized through the pervaporation process, further enriching the structure types of the alcohol-selective pervaporation membrane, and widening the application field of graphdiyne materials and accelerating the industrial application process. SUMMARY

[0007] The key technical problem to be solved by the application is to provide a preparation method of a graphdiyne multilayer composite film, to avoid the problems of polymer pore penetration and nanomaterial agglomeration, and to further enhance the adsorption of alcohol and improve the performance of the alcohol-selective pervaporation membrane in alcohol recovery. The specific technical scheme is as follows:

[0008] A graphdiyne multilayer composite film, characterized by being divided into three layers from top to bottom: an organic polymer layer, a graphdiyne transition layer, and a lower porous base film support layer; the graphdiyne transition layer is grown from the upper surface of the porous base film upward; the organic polymer layer is loaded on the surface of the graphdiyne transition layer; and the graphdiyne transition layer and the organic polymer layer together constitute a selective separation layer.

[0009] The thickness of the graphdiyne transition layer is 100-400 nm, the thickness of the organic polymer layer is 1-5 μm, and preferably the thickness of the selective separation layer composed of the graphdiyne transition layer and the organic polymer layer is 1.1-5.4 μm.

[0010] The graphdiyne monomer used to grow the graphdiyne transition layer is 1,3,5-triethynylbenzene, which is a nanomaterial with extremely strong hydrophobicity.

[0011] As a preferred embodiment, the porous base film is selected from an organic polymer film, an inorganic film, or an organic / inorganic hybrid film, and has an average pore size of 0.01-100 μm.

[0012] Specifically, the shape of the porous base film can be flat plate type, tube type, or hollow fiber type.

[0013] The preparation method of the graphdiyne multilayer composite film of the application comprises the following steps:

[0014] Step a: the surface of the porous base film is chemically modified with an amino-terminated silane coupling agent to make the surface of the base film have amino active groups, and then a small molecule with an alkyne group capable of reacting with the amino group is grafted to obtain a functionalized porous base film for growing an alkyne group layer;

[0015] Step b, a certain amount of graphdiyne monomer is dissolved in a solvent, and copper acetate powder is added, stirred and ultrasonically treated to prepare a mixed solution of graphdiyne monomer and copper acetate; the functionalized porous base film with alkyne group layer grown in step a is immersed in the mixed solution, and a graphdiyne transition layer is grown on the surface of the porous base film at a certain temperature.

[0016] Step c, an organic polymer, a crosslinking agent and a catalyst are mixed to prepare a crosslinking solution, then the crosslinking solution is mixed with an organic solvent to prepare casting solution 1, a certain amount of casting solution 1 is added to the surface of the porous base film with graphdiyne transition layer grown in step b, and a part of the casting solution 1 is left on the surface of the graphdiyne transition layer to form a corresponding organic polymer layer; then the organic solvent is volatilized for 3-12 h, and the film is reacted at 80℃ for 8 h to prepare a graphdiyne multilayer composite film.

[0017] Specifically, in step a, the chemical modification of the surface of the porous base film with an amino-terminated silane coupling agent preferably comprises: immersing the porous base film in an ethanol solution of an amino-terminated silane coupling agent with a concentration of 0.1-1 mM, protecting with nitrogen, and then reacting at 100-150℃ for 1-3 h; the amino-terminated silane coupling agent is selected from one or more of γ-aminopropyl triethoxysilane, γ-aminopropyl trimethoxysilane, N-β(aminoethyl)-γ-aminopropyl trimethoxysilane, N-β(aminoethyl)-γ-aminopropyl methoxydimethoxysilane, N-β(aminoethyl)-γ-aminopropyl triethoxysilane, N-β(aminoethyl)-γ-aminopropyl methoxydiethoxysilane, phenylaminomethyl triethoxysilane, phenylaminomethyl trimethoxysilane, aminoethyl aminoethyl aminopropyl trimethoxysilane, and polyaminoalkyl trialkylsilane.

[0018] Specifically, in step a, the alkyne group-containing small molecule that reacts with the amino group is selected from one or more of 4-ethynylbenzaldehyde, 3-ethynylbenzaldehyde, 2-ethynylbenzaldehyde, 5-ethynylisophthalic acid, 4-ethynylbenzoic acid, 3,5-diethynylbenzoic acid, 3-ethynylbenzoic acid, 2-ethynylbenzoic acid, 3-ethynyl-4-methylbenzoic acid, and 2-chloro-4-ethynylbenzoic acid. The porous base film after surface amination is immersed in an ethanol solution of the alkyne group-containing small molecule that reacts with the amino group with a concentration of 0.5-5 mg / ml, and then reacted at 100-150℃ for 1-3 h.

[0019] Step b, specifically, the graphdiyne monomer is 1,3,5-triethynylbenzene. The concentration of the graphdiyne monomer is 0.4-5 mg / ml; the solvent used is selected from one of methanol, ethanol, and n-propanol. The concentration of copper acetate is 0.2-1 g / L, and the concentration is preferably 0.5 g / L. The reaction at a certain temperature refers to a reaction at 100℃-150℃ for 2-6 h.

[0020] Specifically, the organic polymer in step c is one or more of polydimethylsiloxane (PDMS), polyether block polyamide (PEBA), polyphenylmethylsiloxane (PPMS), polytrifluoropropylmethylsiloxane (PTFMS) or polytrimethylsilapropyne (PTMSP); the cross-linking agent is one or more of tetraethyl orthosilicate (TEOS), tripropyl orthosilicate (TPOS), vinyltriethoxysilane (VTES), ethyltriethoxysilane (ETES) or trifluoropropyltriethoxysilane (TFPTES); and the catalyst is one or more of dibutyltin dilaurate (DBTDL), monobutyltin oxide (MBTO), dibutyltin oxide (DBTO), tripropyltin oxide (TPTO) or chloroplatinic acid.

[0021] Specifically, the method for loading the organic polymer in step c is one or more of vacuum filtration, titration coating, spraying and dipping.

[0022] Preferably, the content of the organic polymer in the casting solution 1 in step c is 5wt.%-50wt.%.

[0023] Preferably, the organic solvent in step c is one or more of ethanol, n-heptane, n-hexane or cyclohexane; the content of the cross-linking agent in the cross-linking solution is 1wt.%-30wt.% and the content of the catalyst is 0.1wt.%-5wt.%.

[0024] The application of the graphdiyne multilayer composite film of the present application separates bioalcohols from aqueous solution or fermentation broth in the form of pervaporation.

[0025] The technical scheme provided by the application has the beneficial effects that: the application is a three-layer film structure from top to bottom, including an organic polymer layer, a graphdiyne transition layer and a porous support layer. The outermost organic polymer layer effectively improves the separation performance through the dense polymer; the intermediate in-situ grown graphdiyne transition layer can effectively increase the adhesion between the support layer and the inorganic nanomaterial, and effectively avoid the problems of agglomeration and pore penetration affecting the film performance; the innermost porous support layer provides support for the selective separation layer of the film and increases the stability of the film. The prepared graphdiyne multilayer composite film can efficiently and stably recover alcohol. In addition, compared with the traditional pure polymer film, the separation factor of the film is increased by 30%-50% under the condition of the same film thickness. Compared with the nanomaterial and polymer blended casting solution, the in-situ growth method makes the permeation flux and separation factor of the film increase by 30%-50% and 60%-90%, respectively, under the condition of the same amount of graphdiyne monomer, compared with the traditional mixed matrix film. The in-situ grown graphdiyne as an ultrathin transition layer further improves the separation performance of the graphdiyne multilayer composite film, provides inspiration for the development of a new structure of alcohol-preferential permeation film, and further broadens the application field of graphdiyne. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 . The water contact angle test diagram of the graphdiyne multilayer composite film (1-1) prepared in Example 1 of the application, the scanning electron microscope diagrams of the surface (1-2) and the cross section (1-3), the energy dispersive X-ray spectrogram of the Si and Al elements of the cross section (1-4), and the water contact angle test diagram of the graphdiyne transition layer (1-5), the scanning electron microscope diagram of the surface (1-6).

[0027] Figure 2 . The water contact angle test diagram of the pure PDMS film (2-1) prepared in Comparative Example 1 of the application, the scanning electron microscope diagrams of the surface (2-2) and the cross section (2-3).

[0028] Figure 3 . The water contact angle test diagram of the graphdiyne mixed matrix film (3-1) prepared in Comparative Example 2 of the application, the scanning electron microscope diagrams of the surface (3-2) and the cross section (3-3). DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the application clearer, the following will further describe the embodiments of the application in combination with the drawings, but the application is not limited to the following examples. The surface and cross section scanning electron microscope diagrams are observed and measured by using a TESCAN MIAI3 type scanning electron microscope (SEM). The water contact angle is observed and measured by using an SDC-300 type contact angle goniometer.

[0030] The embodiment of the present application provides a graphdiyne multilayer composite and a preparation method thereof, characterized by comprising an organic polymer layer, an ultrathin graphdiyne transition layer grown on the surface of a porous base film and a porous support layer.

[0031] The graphdiyne multilayer composite comprises a selective separation layer formed by the graphdiyne transition layer and the organic polymer layer.

[0032] The preparation method comprises the following steps:

[0033] Step 101: The surface of the porous base film is chemically modified by using an amino-terminated silane coupling agent to make the surface of the base film have an amino active group, and then a small molecule with an alkyne group capable of reacting with the amino group is grafted to obtain a functionalized porous base film with an alkyne group layer.

[0034] Step 102: A certain amount of graphdiyne monomer is dissolved in a solvent, and a certain amount of copper acetate powder is added, stirred and ultrasonically treated to prepare a graphdiyne monomer and copper acetate mixed solution; the porous base film with the alkyne group layer grown in step a is immersed in the monomer and copper acetate solution, and reacted at a certain temperature for 2-6h to make the graphdiyne material grow fully on the surface of the porous base film.

[0035] Step 103: A certain amount of organic polymer, crosslinking agent and catalyst are mixed in a certain proportion to prepare a crosslinking solution, then the crosslinking solution is mixed with an organic solvent to prepare a casting solution 1, and then the porous base film loaded with graphdiyne in step 102 is immersed in the casting solution 1, and the amount of the casting solution added is 5-20L / m 2 After the organic solvent is volatilized for 3-12h, the film is placed in an environment at 80℃ and reacted for 8h to obtain the graphdiyne multilayer composite.

[0036] Specifically, the chemical modification of the surface of the porous base film by using the amino-terminated silane coupling agent in step 101 refers to: the porous base film is immersed in an ethanol solution of the amino-terminated silane coupling agent with a concentration of 0.1-1mM, and after nitrogen protection, it is reacted at 100-150℃ for 1-3h; wherein the concentration of the amino-terminated silane coupling agent can be 0.1mM, 0.3mM, 0.5mM, 0.7mM or 1mM, the reaction temperature can be 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃, and the reaction time can be 1h, 1.5h, 2h, 2.5h or 3h; such settings can ensure that the amino silane coupling agent fully reacts with the base film and uniformly grafts an amino group on the surface of the base film, which is conducive to the growth of the subsequent covalent organic framework separation layer.

[0037] Specifically, the amino-terminated silane coupling agent includes γ-aminopropyl triethoxysilane, γ-aminopropyl trimethoxysilane, N-β(aminoethyl)-γ-aminopropyl trimethoxysilane, N-β(aminoethyl)-γ-aminopropyl methoxydimethoxysilane, N-β(aminoethyl)-γ-aminopropyl triethoxysilane, N-β(aminoethyl)-γ-aminopropyl methoxydiethoxysilane, phenylaminomethyl triethoxysilane, phenylaminomethyl trimethoxysilane, aminoethyl aminoethyl aminopropyl trimethoxysilane, polyaminoalkyl trialkylsilane.

[0038] Specifically, the grafting of the alkyne-containing small-molecule organic compound in step 101 refers to immersing the surface-aminoated porous base film in an ethanol solution containing an alkyne-containing small molecule capable of reacting with amino groups, with a concentration of 0.5-50 mg / ml, and reacting at 100-150°C for 1-3 h; the concentration of the alkyne-containing small-molecule organic compound can be 0.5 mg / ml, 1.5 mg / ml, 2.5 mg / ml, 3.5 mg / ml, 5 mg / ml, the reaction temperature can be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, and the reaction time can be 1 h, 1.5 h, 2 h, 2.5 h, 3 h; such settings can enable the alkyne-containing small-molecule organic compound to be uniformly grafted to the surface of the base film, so that the subsequent graphdiyne material grows uniformly on the surface of the base film.

[0039] As a preference, the alkyne-containing small molecule capable of reacting with amino groups includes one or more of 4-ethynylbenzaldehyde, 3-ethynylbenzaldehyde, 2-ethynylbenzaldehyde, 5-ethynylisophthalic acid, 4-ethynylbenzoic acid, 3,5-diethynylbenzoic acid, 3-ethynylbenzoic acid, 2-ethynylbenzoic acid, 3-ethynyl-4-methylbenzoic acid, and 2-chloro-4-ethynylbenzoic acid.

[0040] Specifically, in the graphdiyne monomer solution in step 102, the graphdiyne monomer is 1,3,5-triethynylbenzene; the concentration of the graphdiyne monomer is 0.4-5 mg / ml, and the specific concentration can be 0.4 mg / ml, 0.8 mg / ml, 1 mg / ml, 2 mg / ml, 3 mg / ml, etc., to ensure that the graphdiyne film grows sufficiently on the surface of the base film to form a dense and defect-free selective separation layer; the solvent is selected from one of methanol, ethanol, and n-propanol; the concentration of copper acetate is 0.2-1 g / L, and the specific concentration is 0.5 g / L, so that the graphdiyne monomer has a suitable reaction rate in the solvent.

[0041] The reaction at a certain reaction temperature in step 102 is 100-150°C for 2-6 h.

[0042] Specifically, the organic polymer is one or more of polydimethylsiloxane (PDMS), polyether block polyamide (PEBA), polyphenylmethylsiloxane (PPMS), polytrifluoropropylmethylsiloxane (PTFMS) or polytrimethylsilapropyne (PTMSP); the cross-linking agent is one or more of tetraethyl orthosilicate (TEOS), tripropyl orthosilicate (TPOS), vinyltriethoxysilane (VTES), ethyltriethoxysilane (ETES) or trifluoropropyltriethoxysilane (TFPTES); and the catalyst is one or more of dibutyltin dilaurate (DBTDL), monobutyltin oxide (MBTO), dibutyltin oxide (DBTO), tripropyltin oxide (TPTO) or chloroplatinic acid.

[0043] Specifically, the transition layer composed of in-situ grown graphdiyne has a thickness of 100-400 nm, the organic polymer layer has a thickness of 1-5 μm, and the selective separation layer composed of the transition layer and the organic polymer layer has a thickness of 1.1-5.4 μm.

[0044] As preferred, the porous base membrane is an organic polymer membrane, an inorganic membrane or an organic / inorganic hybrid membrane. The organic polymer membrane can be a polysulfone membrane (PSf), a polyethylene membrane (PE), a polyethersulfone membrane (PES), a polytetrafluoroethylene membrane (PTFE), a polyvinylidene fluoride membrane (PVDF) or the like; the inorganic membrane can be an alumina membrane (Al2O3), a zirconia membrane (ZrO2), a zinc oxide membrane (ZnO) or the like; and the organic / inorganic hybrid membrane can be a polysulfone / SiO2 membrane, a polysulfone / MOF membrane, a polysulfone / molecular sieve membrane, a polyvinylidene fluoride / SiO2 membrane or the like. The average pore size of the porous base membrane is 10-100 nm. The shape of the porous base membrane can be flat plate, tube or hollow fiber.

[0045] As preferred, the method for loading the organic polymer in step 103 is one or more of vacuum filtration, drop coating, spray coating and dip coating.

[0046] As preferred, the organic solvent in step 103 can be one or more of ethanol, n-heptane, n-hexane or cyclohexane; the content of the cross-linking agent in the cross-linking solution can be 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, and the content of the catalyst can be 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%; and the content of the cross-linking solution in the casting solution can be 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%.

[0047] The application will be further described in the following with specific examples.

[0048] In the following specific examples, the operations involved are carried out under conventional conditions or the conditions recommended by the manufacturer, unless otherwise specified. The raw materials used are conventional products available on the market, unless otherwise specified.

[0049] Example 1

[0050] A tubular ceramic (Al2O3) porous substrate with an average pore size of 0.1 μm and a porosity of 40% was used. The substrate was chemically modified with an amino-terminated silane coupling agent, γ-aminopropyltriethoxysilane. The organic polymer used was polydimethylsiloxane (PDMS), the crosslinking agent used was tetraethyl orthosilicate (TEOS), the catalyst used was dibutyltin dilaurate (DBTDL), and the organic solvent used was n-heptane.

[0051] Step a: The tubular ceramic substrate was immersed in an ethanol solution of an amino-terminated silane coupling agent with a concentration of 1 mM, and after nitrogen protection, the substrate was reacted at 110°C for 2 h to introduce amino groups on the surface of the substrate. The amino-functionalized porous substrate was then immersed in an ethanol solution of 4-ethynylbenzaldehyde with a concentration of 1 mg / ml, and reacted at 110°C for 2 h to obtain an ethynyl-functionalized porous substrate.

[0052] Step b: 10 mg of triethynylbenzene and 15 mg of copper acetate were dissolved in 25 ml of ethanol to prepare a monomer and catalyst mixture solution. The functionalized tubular ceramic substrate obtained in step a was vertically immersed in the prepared monomer and catalyst solution, and reacted at 110°C for 3 h, and then naturally cooled to room temperature to allow the growth of graphdiyne on the surface of the porous substrate.

[0053] Step c: Polydimethylsiloxane (PDMS), 10 wt.% of the crosslinking agent tetraethyl orthosilicate (TEOS), and 1 wt.% of the catalyst dibutyltin dilaurate (DBTDL) were mixed to prepare a crosslinking solution. Then, 10 wt.% of the crosslinking solution was mixed with n-heptane to prepare a casting solution 1. The porous substrate with the grown graphdiyne obtained in step b was immersed in a certain amount of the casting solution 1, and a corresponding organic polymer layer was formed on the surface of the graphdiyne transition layer. After the evaporation of the organic solvent for 3 h, the membrane was placed in an 80°C environment for 8 h to prepare a graphdiyne multilayer composite.

[0054] Figure 1 Figure 1-1 shows that the water contact angle of the graphdiyne multilayer composite prepared in this example is 131°, indicating good hydrophobicity. The SEM surface image Figure 1 Figure 1-2 shows that the surface of the prepared graphdiyne multilayer composite is uniform and defect-free. The SEM cross-sectional image Figure 1 Figure 1-3 shows that the thickness of the organic polymer layer of the prepared graphdiyne multilayer composite is about 3.2 μm. The EDXS cross-sectional imageFigure 1 Fig. 1-4 shows that the thickness of the graphdiyne transition layer is about 150 nm. Figure 1 Fig. 1-5 shows that the water contact angle of the graphdiyne transition layer is 145°, indicating strong hydrophobicity, and the SEM surface Figure 1 Fig. 1-6 shows that the surface of the prepared graphdiyne transition layer is uniform.

[0055] The prepared graphdiyne multilayer composite mold was placed in a pervaporation device for performance test, and the test conditions were as follows: (1) the composition of the raw material liquid was 5wt.% ethanol aqueous solution, and the feed temperature was 60℃; (2) the downstream pressure of the membrane was 200Pa.

[0056] The pervaporation performance of the graphdiyne multilayer composite mold was measured as follows: the permeation flux was 3864gm -2 h -1 , the separation factor was 10.51, and the content of ethanol in the permeate was 36wt.%.

[0057] Comparative Experiment 1

[0058] A tubular ceramic (Al2O3) porous base membrane was used, and the average pore size and porosity of the base membrane were 0.1μm and 40%, respectively. The base membrane was chemically modified by using an amino-terminated silane coupling agent, γ-aminopropyl triethoxysilane. The selected organic polymer was polydimethylsiloxane (PDMS), the selected crosslinking agent was tetraethyl orthosilicate (TEOS), the selected catalyst was dibutyltin dilaurate (DBTDL), and the selected organic solvent was n-heptane.

[0059] In step a, polydimethylsiloxane (PDMS), 10wt.% of the crosslinking agent tetraethyl orthosilicate (TEOS), and 1wt.% of the catalyst dibutyltin dilaurate (DBTDL) were mixed uniformly to prepare a crosslinking solution. Then, 10wt.% of the crosslinking solution was mixed uniformly with ethanol to prepare casting solution 2. The ceramic tube was immersed in the casting solution 2, and a part of the casting solution 2 remained on the surface of the ceramic tube to form a corresponding organic polymer layer. After the organic solvent was volatilized for 3h, the membrane was placed in an environment at 80℃ for 8h to prepare a graphdiyne multilayer composite mold.

[0060] Figure 2 Fig. 2-1 shows that the water contact angle of the pure PDMS membrane prepared in this example is 124°. The SEM results Figure 2 Fig. 2-2 shows that the surface of the prepared pure PDMS membrane is dense and defect-free, Figure 2 Fig. 2-3 shows that the prepared pure PDMS membrane has a two-layer structure, and the thickness of the organic polymer layer is 3.2μm.

[0061] The prepared PDMS polymer membrane was placed in a pervaporation device for performance test, and the test conditions were as follows: (1) the composition of the raw material liquid was 5wt.% ethanol aqueous solution, and the feeding temperature was 60°C; (2) the downstream pressure of the membrane was 200 Pa.

[0062] The measured pervaporation performance of the graphdiyne multilayer composite membrane was as follows: the permeation flux was 4081 gm -2 h -1 -1, the separation factor was 6.983, and the content of ethanol in the permeate was 27wt.%.

[0063] Comparative Experiment 2

[0064] A tubular ceramic (Al2O3) porous substrate membrane was used, and the average pore size and porosity of the substrate membrane were 0.1 μm and 40%, respectively. An amino-terminated silane coupling agent, γ-aminopropyl triethoxysilane, was selected to chemically modify the substrate membrane. A polydimethylsiloxane (PDMS) was selected as the organic polymer, tetraethyl orthosilicate (TEOS) was selected as the crosslinking agent, dibutyltin dilaurate (DBTDL) was selected as the catalyst, and n-heptane was selected as the organic solvent.

[0065] Step a, polydimethylsiloxane (PDMS), 10wt.% crosslinking agent tetraethyl orthosilicate (TEOS), and 1wt.% catalyst dibutyltin dilaurate (DBTDL) were mixed uniformly to prepare a crosslinking solution. Then, 0.1wt.% graphdiyne monomer, 10wt.% crosslinking solution, and ethanol were mixed uniformly to prepare casting solution 3. The ceramic tube was immersed in the casting solution 3, and a part of the casting solution 3 remained on the surface of the ceramic tube to form a corresponding organic polymer layer. After the organic solvent was volatilized for 3h, the membrane was placed in an 80°C environment for 8h to prepare a graphdiyne multilayer composite membrane.

[0066] Figure 3 Figure 3-1 shows that the water contact angle of the graphdiyne mixed matrix membrane prepared in this example was 132°. The SEM results Figure 3 (Figure 3-2) show that the surface of the prepared graphdiyne mixed matrix membrane was dense, Figure 3 Figure 3-3 shows that the prepared graphdiyne mixed matrix membrane was a two-layer structure, and the thickness of the mixed matrix layer was 3.2 μm.

[0067] The prepared PDMS polymer membrane was placed in a pervaporation device for performance test, and the test conditions were as follows: (1) the composition of the raw material liquid was 5wt.% ethanol aqueous solution, and the feeding temperature was 60°C; (2) the downstream pressure of the membrane was 200 Pa.

[0068] The measured pervaporation performance of the graphdiyne multilayer composite membrane was as follows: the permeation flux was 3309 gm -2 h -1 -1, the separation factor was 6.653, and the content of ethanol in the permeate was 26wt.%.

[0069] Example 2

[0070] A tubular ceramic (Al2O3) porous substrate with an average pore size of 0.1 μm and a porosity of 40% was used. The substrate was chemically modified with an amino-terminated silane coupling agent, γ-aminopropyltriethoxysilane. The organic polymer used was polydimethylsiloxane (PDMS), the cross-linking agent used was tetraethyl orthosilicate (TEOS), the catalyst used was dibutyltin dilaurate (DBTDL), and the organic solvent used was n-heptane.

[0071] Step a, the tubular ceramic substrate was immersed in an ethanol solution of the amino-terminated silane coupling agent with a concentration of 1 mM, and after nitrogen protection, the substrate was reacted at 110°C for 2 h to introduce amino groups on the surface of the substrate. Then the amino-functionalized porous substrate was immersed in an ethanol solution of 4-ethynylbenzaldehyde with a concentration of 1 mg / ml, and reacted at 110°C for 2 h to obtain the ethynyl-functionalized porous substrate.

[0072] Step b, 20 mg of triethynylbenzene and 15 mg of copper acetate were dissolved in 25 ml of ethanol to prepare a monomer and catalyst mixture solution. The functionalized tubular ceramic substrate from step a was vertically immersed in the prepared monomer and catalyst solution, and reacted at 110°C for 3 h, and then naturally cooled to room temperature to allow the growth of graphdiyne on the surface of the porous substrate.

[0073] Step c, polydimethylsiloxane (PDMS), 10 wt.% of the cross-linking agent tetraethyl orthosilicate (TEOS), and 1 wt.% of the catalyst dibutyltin dilaurate (DBTDL) were mixed to prepare a cross-linking solution. Then 10 wt.% of the cross-linking solution was mixed with n-heptane to prepare a casting solution 1. The graphdiyne-functionalized porous substrate from step b was immersed in a certain amount of the casting solution 1. Due to the porous structure of the graphdiyne transition layer, the casting solution 1 partially penetrated into the graphdiyne transition layer, leaving a part of the casting solution 1 on the surface of the graphdiyne transition layer to form a corresponding organic polymer layer. After volatilizing the organic solvent for 3 h, the membrane was placed in an 80°C environment for 8 h to prepare a graphdiyne multilayer composite membrane.

[0074] The prepared graphdiyne multilayer composite membrane was placed in a pervaporation device for performance testing. The testing conditions were as follows: (1) the feed liquid was 5 wt.% ethanol aqueous solution, and the feed temperature was 60°C; (2) the downstream pressure of the membrane was 200 Pa.

[0075] The pervaporation performance of the graphdiyne multilayer composite membrane was measured as follows: the permeation flux was 2847 g m-2h-1, the separation factor was 8.33, and the ethanol content in the permeate was 31 wt.%. -2 h -1 ​

[0076] Example 3

[0077] A tubular ceramic (Al2O3) porous substrate with an average pore size of 0.1 μm and a porosity of 40% was used. The substrate was chemically modified with an amino-terminated silane coupling agent, γ-aminopropyltriethoxysilane. The organic polymer used was polydimethylsiloxane (PDMS), the cross-linking agent used was tetraethyl orthosilicate (TEOS), the catalyst used was dibutyltin dilaurate (DBTDL), and the organic solvent used was n-heptane.

[0078] Step a, the tubular ceramic substrate was immersed in a toluene solution of the amino-terminated silane coupling agent with a concentration of 1 mM, and after nitrogen protection, the reaction was carried out at 110°C for 2 h to introduce amino groups on the surface of the substrate. Then the amino-functionalized porous substrate was immersed in a toluene solution of 4-ethynylbenzaldehyde with a concentration of 1 mg / ml, and the reaction was carried out at 110°C for 2 h to obtain the ethynyl-functionalized porous substrate.

[0079] Step b, 10 mg of triethynylbenzene and 15 mg of copper acetate were dissolved in 25 ml of ethanol to prepare a monomer and catalyst mixed solution. The functionalized tubular ceramic substrate prepared in step a was vertically immersed in the prepared monomer and catalyst mixed solution, and the reaction was carried out at 110°C for 3 h, and then naturally cooled to room temperature to allow the growth of graphdiyne on the surface of the porous substrate.

[0080] Step c, polydimethylsiloxane (PDMS), 10 wt.% of the cross-linking agent tetraethyl orthosilicate (TEOS), and 1 wt.% of the catalyst dibutyltin dilaurate (DBTDL) were mixed uniformly to prepare a cross-linking solution. Then 10 wt.% of the cross-linking solution was mixed with n-heptane to prepare a casting solution 1. The graphdiyne-functionalized porous substrate prepared in step b was immersed in a certain amount of the casting solution 1. Due to the porous structure of the graphdiyne transition layer, the casting solution 1 partially penetrated into the graphdiyne transition layer, leaving a part of the casting solution 1 on the surface of the graphdiyne transition layer to form a corresponding organic polymer layer. After volatilizing the organic solvent for 3 h, the membrane was placed in an environment at 80°C for 8 h to prepare a graphdiyne multilayer composite membrane.

[0081] The prepared graphdiyne multilayer composite membrane was placed in a pervaporation device for performance testing. The testing conditions were as follows: (1) the composition of the raw material solution was 5 wt.% ethanol aqueous solution, and the feed temperature was 60°C; (2) the downstream pressure of the membrane was 200 Pa.

[0082] The pervaporation performance of the graphdiyne multilayer composite membrane was measured as follows: the permeation flux was 3360 g m-2h-1, the separation factor was 9.18, and the ethanol content in the permeate was 33 wt.%. -2 h -1 ​

[0083] The above merely provides the preferred embodiment of the present application, and not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a graphdiyne multilayer composite film, characterized in that, It consists of three layers, from top to bottom: an organic polymer layer, a graphyne transition layer, and a lower porous base membrane support layer; the graphyne transition layer grows upward from the upper surface of the porous base membrane; the organic polymer layer is loaded on the surface of the graphyne transition layer; the graphyne transition layer and the organic polymer layer together constitute a selective separation layer; Includes the following steps: Step a: Chemically modify the surface of the porous base membrane with an amino-terminated silane coupling agent to give the base membrane surface amino active groups, and then graft small molecules with alkyne groups that can react with amino groups to obtain a functionalized porous base membrane with alkyne layer. Step b: Dissolve a certain amount of graphyne monomer in a solvent, add copper acetate powder, stir and sonicate to prepare a mixed solution of graphyne monomer and copper acetate; immerse the functionalized porous base film from step a, in which the diatom layer is grown, in the above mixed solution and react at a certain temperature to allow the graphyne transition layer to grow fully on the surface of the porous base film. Step c: Mix the organic polymer, crosslinking agent, and catalyst evenly to prepare a crosslinking solution. Then, mix the crosslinking solution with an organic solvent evenly to prepare casting solution 1. Add a certain amount of casting solution 1 to the surface of the porous base film on which the graphdiyne transition layer has been grown in step b. Leave a portion of casting solution 1 on the surface of the graphdiyne transition layer to form the corresponding organic polymer layer. After evaporating the organic solvent for 3-12 h, place the film at 80 ℃ for 8 h to obtain a graphdiyne multilayer composite film. The organic polymer is one or more of polydimethylsiloxane (PDMS), polyether block polyamide (PEBA), polyphenylmethylsiloxane (PPMS), polytrifluoropropylmethylsiloxane (PTFMS), or polytrimethylsiloxypyridine (PTMSP).

2. The method according to claim 1, characterized in that, The chemical modification of the porous membrane surface using a terminal aminosilane coupling agent described in step a involves immersing the porous membrane in an ethanol solution of a 0.1-1 mM terminal aminosilane coupling agent, and reacting it at 100-150 °C for 1-3 h under nitrogen protection; the terminal aminosilane coupling agent is... γ -aminopropyltriethoxysilane, γ -aminopropyltrimethoxysilane, N - β (aminoethyl)- γ -aminopropyltrimethoxysilane, N - β (aminoethyl)- γ -aminopropylmethoxydimethoxysilane, N - β (aminoethyl)- γ -aminopropyltriethoxysilane, N - β (aminoethyl)- γ -One or more of aminopropylmethoxydiethoxysilane, phenylaminomethyltriethoxysilane, phenylaminomethyltrimethoxysilane, aminoethylaminopropyltrimethoxysilane, and polyaminoalkyltrialkylsilane; The small alkynyl molecule grafted and reacting with amino groups in step a is one or more of the following: 4-acetylenylbenzaldehyde, 3-acetylenylbenzaldehyde, 2-acetylenylbenzaldehyde, 5-acetylenylisophthalic acid, 4-acetylenylbenzoic acid, 3,5-diethynylbenzoic acid, 3-acetylenylbenzoic acid, 2-acetylenylbenzoic acid, 3-acetylenyl-4-methylbenzoic acid, and 2-chloro-4-acetylenylbenzoic acid; the porous substrate membrane after surface amination is immersed in an ethanol solution of the small alkynyl molecule reacting with amino groups at a concentration of 0.5-5 mg / ml, and reacted at 100-150 °C for 1-3 h; Step b, the graphyne monomer is 1,3,5-triethynylbenzene; the concentration of the graphyne monomer is 0.4-5 mg / ml; the solvent used is selected from methanol, ethanol, and n-propanol; the concentration of copper acetate is 0.2-1 g / L; the reaction at a certain temperature refers to the reaction at 100 ℃-150 ℃ for 2-6 h. The crosslinking agent mentioned in step c is one or more of tetraethyl orthosilicate (TEOS), propyl orthosilicate (TPOS), vinyltriethoxysilane (VTES), ethyltriethoxysilane (ETES), or trifluoropropyltriethoxysilane (TFPTES); the catalyst is one or more of dibutyltin dilaurate (DBTDL), monobutyltin oxide (MBTO), dibutyltin oxide (DBTO), tripropyltin oxide (TPTO), or chloroplatinic acid.

3. The method according to claim 1, characterized in that, The organic polymer content in the casting solution 1 described in step c is 5 wt.%-50 wt.%; The organic solvent mentioned in step c is one or more of ethanol, n-heptane, n-hexane, or cyclohexane; the crosslinking agent content in the crosslinking solution is 1 wt.%-30 wt.%, and the catalyst content is 0.1 wt.%-5 wt.%. The method for loading the organic polymer in step c is one or more of the following: vacuum filtration, titration coating, spraying, and dip coating.

4. The method according to claim 1, characterized in that, The thickness of the ultrathin graphyne transition layer composed of in-situ grown graphyne is 100-400 nm, and the thickness of the organic polymer layer is 1-5 μm; the thickness of the selective separation layer composed of the ultrathin graphyne transition layer and the organic polymer layer is 1.1-5.4 μm.

5. The method according to claim 1, characterized in that, The porous base membrane is an organic polymer membrane, an inorganic membrane, or an organic / inorganic hybrid membrane, with an average pore size of 10-100 nm, and a shape of flat plate, tubular, or hollow fiber.

6. The graphdiyne multilayer composite film prepared according to any one of claims 1-5.

7. The application of the graphdiyne multilayer composite membrane according to claim 6, wherein bio-alcohols are separated from aqueous solutions or fermentation broths by pervaporation.

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