A porous liquid / graphene oxide composite membrane and a preparation method and application thereof

Abstract

This invention relates to a porous liquid / graphene oxide composite membrane, its preparation method, and its applications. The composite membrane is a layer in which a porous liquid and graphene oxide are assembled on a porous support. The porous liquid comprises a porous framework material and sterically hindered molecular chain segments. The sterically hindered molecular chain segments include ionic liquids and / or crown ethers. The ionic liquid is composed of paired anionic and cationic groups. The anionic group includes bis(trifluoromethanesulfonyl)imide, and the cationic group includes imidazole and / or pyridine. The composite membrane is prepared using a simple liquid-phase preparation technique. The abundant interfacial interactions between the porous liquid and graphene oxide induce ordered self-assembly, controlling the uniform distribution and directional arrangement of the porous liquid within the two-dimensional graphene oxide membrane layers. This constructs a stable and defect-free two-dimensional graphene oxide membrane confined mass transfer channel, resulting in excellent ion permeability and selectivity, thus enabling its application in the preparation of ion separation products.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, specifically to a porous liquid / graphene oxide composite membrane, its preparation method, and its application. Background Technology

[0002] Ion separation is a common requirement in important industrial processes such as lithium extraction from salt lakes, waste acid recovery, brine purification, and hard water softening. Membrane separation technology has outstanding advantages such as high separation efficiency, high precision, and low energy consumption. In particular, two-dimensional material membranes, represented by graphene oxide membranes, have seen rapid development in ion separation applications in recent years. However, the narrow and tortuous two-dimensional nanochannels in the interlayer of graphene oxide membranes severely limit their separation efficiency. Introducing porous framework materials into the interlayer of graphene oxide membranes can increase the interlayer spacing and provide porous channels, which is an effective means to improve membrane permeability. However, porous framework materials often have poor compatibility with graphene oxide and tend to agglomerate locally. The resulting composite membranes are prone to non-selective defects, leading to reduced membrane selectivity. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, one objective of this invention is to provide a porous liquid / graphene oxide composite membrane in which the porous framework material is uniformly distributed and stably bonded between the membrane layers formed by the graphene oxide composite. This membrane can precisely construct and modulate the spatial structure and wall sites of the confined mass transfer channels within the two-dimensional graphene oxide membrane, thereby simultaneously improving the ion permeability and selectivity of the composite membrane. A second objective of this invention is to provide a porous liquid / graphene oxide composite membrane and its preparation method, which is simple in procedure and suitable for large-scale preparation. A third objective of this invention is to provide an application of the porous liquid / graphene oxide composite membrane.

[0004] One of the objectives of this invention is achieved through the following technical solution:

[0005] A porous liquid / graphene oxide composite membrane, the composite membrane comprising a porous support and a porous liquid material and graphene oxide ordered assembled on the porous support;

[0006] The porous liquid material comprises a porous framework material and sterically hindered molecular chain segments combined with the porous framework material; and the porous framework material comprises at least one of a metal-organic framework, a metal-organic cage, and a porous organic cage; the sterically hindered molecular chain segments comprise ionic liquids and / or crown ethers; in the porous liquid material, the molar ratio of the porous framework material to the sterically hindered molecular chain segments is 1:20 to 1:1;

[0007] The porous support is a porous ultrafiltration membrane and / or microfiltration membrane.

[0008] Preferably, the amount of the porous liquid material assembled on the porous support is 10-100 mg / cm³.2 ;

[0009] And / or, the amount of graphene oxide assembled on the porous support is 0.1-2 mg / cm³. 2 .

[0010] Preferably, in the porous framework material, the metal-organic framework is 2-methylimidazolium zinc salt (ZIF-8) and / or zirconium 1,4-carboxybenzene (UiO-66); the metal-organic cage is MOP-18; and the porous organic cage is at least one of CCl crystal, CC3 crystal, RCC3 crystal, CC5 crystal and KACC crystal.

[0011] Porous framework materials possess micropore scale, well-defined intrinsic windows, and pore cavities, enabling precise sieving of ions with different hydration sizes and providing a rapid three-dimensional ion mass transfer pathway. Steric hindrance molecular segments contain functional groups that do not enter the pores of the porous framework material themselves, but can bind to the porous framework material and graphene oxide through covalent / non-covalent interactions, resulting in uniform distribution and stable bonding of the porous framework material within the graphene oxide film layers. A suitable molar ratio facilitates the full binding and encapsulation of the steric hindrance molecular segments with the porous framework material, yielding a porous liquid. Appropriate solvent selection and concentration range promote good dispersion of the porous liquid in the solvent, avoiding localized aggregation.

[0012] And / or, the ionic liquid in the sterically hindered molecular chain segment includes anionic and cationic groups, wherein the anionic group includes bis(trifluoromethanesulfonyl)imide and the cationic group includes imidazole or pyridine.

[0013] The aforementioned porous support provides sufficient mechanical strength to the membrane. If the pore size of the porous support is too small, it will introduce additional mass transfer resistance, affecting membrane separation efficiency. If the pore size of the porous support is too large, the material will become trapped inside the support channels and fail to form a membrane. The porous support with the pore size provided by this invention exhibits better performance.

[0014] Preferably, the ionic liquid in the sterically hindered molecular chain segment includes at least one of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and N-butylpyridine bis(trifluoromethanesulfonyl)imide salt;

[0015] And / or, the crown ether comprises at least one of 18-crown ether-6, 15-crown ether-5, dicyclohexano-18-crown ether-6, dibenzo-18-crown ether-6, and 4-carboxybenzo-21-crown ether-7.

[0016] Preferably, the graphene oxide is a monodisperse graphene oxide nanosheet with a lateral dimension of 5-50 μm, a monolayer ratio of ≥99%, and an oxygen content of 20%-40%.

[0017] Through research, the inventors discovered that monodisperse graphene oxide nanosheets possess micron-scale lateral dimensions and nanometer-scale thickness, enabling them to stack orderly in a solvent-assisted manner to form a regular two-dimensional layered film structure. Appropriate solvent selection and concentration range are beneficial for the good dispersion of graphene oxide in the solvent, avoiding localized aggregation.

[0018] Preferably, the porous support is a porous ultrafiltration membrane or a microfiltration membrane; the material of the porous support includes at least one of polyacrylonitrile, polycarbonate, nylon, mixed cellulose ester, alumina, zirconium oxide and titanium oxide; the structure of the porous support is sheet-type or plate-type; the average pore size of the porous support is 10-1000 nm.

[0019] The second objective of this invention is achieved by the following technical solution:

[0020] The preparation method of the above-mentioned porous liquid / graphene oxide composite membrane includes the following steps:

[0021] (1) Preparation of porous liquid dispersion: A porous framework material is combined with sterically hindered molecular chain segments to obtain a porous liquid, and the porous liquid is uniformly dispersed in a solvent to obtain a porous liquid dispersion.

[0022] (2) Preparation of graphene oxide dispersion: Graphene oxide is uniformly dispersed in a solvent to obtain graphene oxide dispersion.

[0023] (3) Assembly of porous liquid / graphene oxide composite membrane: The porous liquid dispersion obtained in step (1) and the graphene oxide dispersion obtained in step (2) are assembled on a porous support to form a membrane layer. After drying, the porous liquid / graphene oxide composite membrane is obtained.

[0024] Preferably, in step (1), the solvent includes at least one of methanol, DMF, DCM, formic acid, dichloromethane, chloroform, and methanol-water mixed solution; the concentration of the porous liquid dispersion is 0.01-0.5 mol / L; in step (2), the solvent includes at least one of water, DMSO, NMF, DMF, methanol, and methanol-water mixed solution; the concentration of the graphene oxide dispersion is 0.01-0.5 mg / mL.

[0025] Preferably, in steps (1) and (2), the porous liquid and graphene oxide are uniformly dispersed in the solvent by stirring and / or ultrasonic treatment, respectively; wherein, the stirring time is 10-60 min; the ultrasonic power is 100-700 W and the ultrasonic time is 5-30 min; appropriate stirring and ultrasonic processes are beneficial to assist the porous liquid and graphene oxide in uniform dispersion in the solvent, while excessive ultrasonic power and ultrasonic time will cause the material structure to break.

[0026] In step (3), the assembly method includes spin coating and / or filtration; the spin coating step is as follows: the porous liquid dispersion and the graphene oxide dispersion are sequentially and alternately spin-coated on the porous support, the spin coating speed is 500-2500 rpm, the single spin coating time for each spin coating layer is 30-120s, and the spin coating cycle is 5-60 times.

[0027] The filtration steps are as follows: the porous liquid dispersion and the graphene oxide dispersion are mixed evenly by stirring to obtain a film-forming solution, and then assembled on the porous support by pressure driving; the pressure driving method is pressure filtration or vacuum suction, and the pressure difference is 0.1-1.0 MPa.

[0028] The above-mentioned ordered assembly conditions can prepare a porous liquid / graphene oxide composite film with a continuous and defect-free surface. During the contact process, the porous liquid dispersion and the graphene oxide dispersion form rich interfacial interactions such as van der Waals interactions, hydrogen bonding interactions, π-π interactions, and electrostatic interactions, which makes the porous liquid uniformly distributed and oriented between the graphene oxide film layers, thus constructing a stable and defect-free two-dimensional graphene oxide film confined mass transfer channel.

[0029] Preferably, in step (3), the drying temperature is 25–60°C, and the drying time is 12–36 h. The drying process can remove residual moisture inside the membrane. If the drying temperature is too low, the membrane preparation efficiency will be low. If the drying temperature is too high, it will cause partial reduction or removal of oxygen-containing groups in the graphene oxide membrane, damaging the membrane structure. The drying under the conditions provided by the present invention has a better effect.

[0030] The third objective of this invention is achieved by the following technical solution:

[0031] The above-mentioned porous liquid / graphene oxide composite membrane is used in the preparation of ion separation products.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) The composite membrane of the present invention is a membrane layer in which porous liquid and graphene oxide are assembled on a porous support; wherein, the porous liquid comprises a porous framework material and sterically hindered molecular chain segments; the sterically hindered molecular chain segments comprise ionic liquids and / or crown ethers; the ionic liquid is composed of paired anionic and cationic groups; the anionic group comprises bis(trifluoromethanesulfonyl)imide, and the cationic group comprises imidazole and / or pyridine. Porous liquids are a novel type of material that combines porous framework materials and sterically hindered molecular chain segments, possessing both the porosity of porous framework materials and the functional advantages of sterically hindered molecular chain segments. This invention combines porous framework materials with sterically hindered molecular chain segments to prepare porous liquids. The porous liquids then utilize rich interfacial interactions with graphene oxide nanosheets, including van der Waals interactions, hydrogen bonding, π-π interactions, and electrostatic interactions, to induce ordered assembly and construct stable, defect-free two-dimensional graphene oxide membrane confined mass transfer channels. Within these channels, the nanopores of the porous framework material precisely sieve ions of different hydration sizes and provide rapid three-dimensional ion mass transfer pathways. The functional groups of the sterically hindered molecular chain segments further construct specific interactions with target ions, such as charge and affinity, promoting / restricting specific interactions. The porous liquid synergistically regulates the spatial structure and wall sites of the two-dimensional graphene oxide membrane confined mass transfer channels, achieving a simultaneous improvement in the ion permeability and selectivity of the porous liquid / graphene oxide composite membrane.

[0034] (2) The composite membrane of this invention is prepared using a simple liquid-phase preparation technique. It utilizes the rich interfacial interactions between the porous liquid and graphene oxide to induce ordered self-assembly, controlling the uniform distribution and directional arrangement of the porous liquid within the two-dimensional graphene oxide membrane layers to construct a stable and defect-free confined mass transfer channel. For specific ion separation requirements, nanopores and functional groups matching the porous liquid are designed to customize and modulate the spatial structure and wall sites of the confined mass transfer channel in the two-dimensional graphene oxide membrane. The sub-nanometer windows of the porous framework material can sieve monovalent / divalent ions, while the nanocavities allow monovalent ions to migrate with low resistance. The functional groups of the sterically hindered molecular chain segments can further interact with monovalent ions through hydration "compensation" and "jumping" mechanisms, specifically promoting transport interactions. This synergistically enhances the ion confined mass transfer effect, achieving a simultaneous improvement in ion permeability and selectivity.

[0035] (3) The composite membrane of the present invention can be used to prepare ion separation composite membranes. Based on its good ion permeability and selectivity, this composite membrane is expected to be widely used in ion separation-related fields such as lithium extraction from salt lakes, waste acid recovery, and energy conversion. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of a porous liquid / graphene oxide composite membrane. Detailed Implementation

[0037] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0038] like Figure 1 As shown, this invention combines porous framework materials with sterically hindered molecular chain segments to prepare porous liquids. The porous liquids then utilize rich interfacial interactions with graphene oxide nanosheets, including van der Waals interactions, hydrogen bonding, π-π interactions, and electrostatic interactions, to induce ordered assembly and construct stable, defect-free two-dimensional graphene oxide membrane confined mass transfer channels. Within these channels, the nanopores of the porous framework material precisely sieve ions of different hydration sizes and provide rapid three-dimensional ion mass transfer pathways. The functional groups of the sterically hindered molecular chain segments further construct specific interactions with target ions, such as charge and affinity, promoting / restricting specific interactions. The porous liquid synergistically regulates the spatial structure and wall sites of the two-dimensional graphene oxide membrane confined mass transfer channels, achieving a simultaneous improvement in the ion permeability and selectivity of the porous liquid / graphene oxide composite membrane.

[0039] The CC3 crystals described in this specific embodiment of the invention are synthesized by the following steps: Dichloromethane (11.925 g) is slowly added to 0.3 g of trimesaldehyde. Then, 30 μL of trifluoroacetic acid is added to the mixture. Separately, a solution of 0.3 g of 1,2-diaminocyclohexane (a mixture of cis and trans isomers) in 11.925 g of dichloromethane is slowly added to the mixture. The reactants are covered and stored at room temperature for 120 h. An ethanol-dichloromethane mixture (95% / 5% v / v) is added, and the mixture is centrifuged, washed, and dried to obtain the CC3 crystal product.

[0040] The KACC crystals described in this specific embodiment of the invention are synthesized by the following steps: DL-2,3-diaminopropionic acid monohydrochloride (0.18 g) and KOH (0.336 g) are stirred in methanol (11.925 g) for 30 min to prepare potassium 2,3-diaminopropane. The resulting turbidity is centrifuged, and the clear supernatant is collected as solution A. 1,3,5-triformylbenzene (0.15 g, 0.91 mmol) is dissolved in methanol (83.472 g) at room temperature, and this is labeled solution B. Ethylenediamine (56 mg, 0.69 mmol) and potassium 2,3-diaminopropane (96 mg, 0.69 mmol, solution A) are added to methanol (23.85 g), and this is labeled solution C. Solution C is added to solution B, and the resulting mixture is allowed to stand for 60 h to react. The reacted mixture is then heated in an oil bath at 80 °C until the solvent is completely evaporated. Take the crystals from the beaker wall, wash them three times with ethanol by centrifugation, and dry them under vacuum for 12 hours to obtain the KACC crystal product.

[0041] In a specific embodiment of the present invention, MOP-18 is synthesized by the following steps. 5-OC 12 H 25-H₂mBDC (2.7 g, 7.6 mmol) and anhydrous copper acetate (1.5 g, 7.6 mmol) were dissolved in 100 mL and 50 mL of DMF, respectively, and the two solutions were mixed at room temperature. 100 mL of methanol was added to the mixture, and the mixture was sealed and allowed to react for 24 h. The resulting turbidity was centrifuged, and the blue precipitate was collected and washed three times each with DMF and methanol by centrifugation. After vacuum drying for 12 hours, the MOP-18 product was obtained.

[0042] The UiO-66 described in this specific embodiment of the invention is synthesized by the following steps: Zirconium oxychloride octahydrate (0.21 g, 0.7 mmol) and terephthalic acid (0.5 g, 3.0 mmol) are dissolved in 20 mL of DMF and 9 mL of acetic acid. The mixed solution is heated at 90 °C for 18 hours. After cooling to room temperature, the product is washed three times each with DMF and ethanol by centrifugation, and then dried under vacuum for 12 hours to obtain the UiO-66 product.

[0043] Example 1

[0044] The porous liquid / graphene oxide composite membrane of this embodiment is a membrane layer in which porous liquid and graphene oxide are assembled on a porous support; wherein, the porous liquid includes a porous framework material and sterically hindered molecular chain segments; the sterically hindered molecular chain segments are ionic liquids; the ionic liquid is 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide. The porous framework material is CC3 crystal.

[0045] The preparation method of the above-mentioned porous liquid / graphene oxide composite membrane specifically includes the following steps:

[0046] (1) Preparation of porous liquid dispersion: 0.005 mol CC3 crystals and 0.025 mol 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide were uniformly dispersed in 200 mL methanol-water mixed solution (75% / 25% v / v), stirred for 30 min, and ultrasonically treated at 500 W for 10 min to obtain porous liquid dispersion.

[0047] (2) Preparation of graphene oxide dispersion: 40 mg of graphene oxide (lateral dimension 20 μm, monolayer ratio ≥99%, oxygen content 29%) was uniformly dispersed in 200 mL of water, stirred for 30 min, and ultrasonically treated at 500 W for 10 min to obtain graphene oxide dispersion.

[0048] (3) Assembly of the porous liquid / graphene oxide composite membrane: The porous liquid dispersion obtained in step (1) and the graphene oxide dispersion obtained in step (2) were sequentially assembled on a polyacrylonitrile flat porous support (average pore size of 10 nm) by spin coating. The spin coating speed was 2000 rpm, the spin coating time for each layer was 60 seconds, and the number of spin coating cycles was 30. After the membrane was formed, it was dried at 45°C for 24 h to obtain the porous liquid / graphene oxide composite membrane.

[0049] Example 2

[0050] The porous liquid / graphene oxide composite membrane of this embodiment is a membrane layer in which porous liquid and graphene oxide are assembled on a porous support; wherein, the porous liquid includes a porous framework material and sterically hindered molecular chain segments; the sterically hindered molecular chain segments are ionic liquids; the ionic liquid is 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide. The porous framework material is CC3 crystal.

[0051] As an embodiment of the method for preparing porous liquid / graphene oxide composite membrane of the present invention, the specific steps include:

[0052] (1) Preparation of porous liquid dispersion: 0.005 mol CC3 crystals and 0.1 mol 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide were uniformly dispersed in 210 mL DMF, stirred for 60 min, and ultrasonically treated at 700 W for 5 min to obtain porous liquid dispersion.

[0053] (2) Preparation of graphene oxide dispersion: 100 mg of graphene oxide (transverse dimension 5 μm, monolayer ratio ≥99%, oxygen content 20%) was uniformly dispersed in 200 mL of DMF, stirred for 60 min, and ultrasonically treated at 700 W for 5 min to obtain graphene oxide dispersion.

[0054] (3) Assembly of porous liquid / graphene oxide composite membrane: The porous liquid dispersion obtained in step (1) and the graphene oxide dispersion obtained in step (2) were sequentially assembled on a nylon flat porous support (average pore size of 200 nm) by spin coating. The spin coating speed was 2500 rpm, the spin coating time for each layer was 30 seconds, and the number of spin coating cycles was 60. After the membrane was formed, it was dried at 25°C for 36 h to obtain the porous liquid / graphene oxide composite membrane.

[0055] Example 3

[0056] The porous liquid / graphene oxide composite membrane of this embodiment is a membrane layer in which porous liquid and graphene oxide are assembled on a porous support; wherein, the porous liquid includes a porous framework material and sterically hindered molecular chain segments; the sterically hindered molecular chain segments are crown ethers; the crown ether is dicyclohexano-18-crown ether-6. The porous framework material is KACC crystal.

[0057] The above-mentioned method for preparing porous liquid / graphene oxide composite membranes specifically includes the following steps:

[0058] (1) Preparation of porous liquid dispersion: 0.25 mmol KACC crystals and 0.25 mmol dicyclohexane-18-crown ether-6 were uniformly dispersed in 50 mL of water, stirred for 10 min, and ultrasonically treated at 100 W for 30 min to obtain porous liquid dispersion.

[0059] (2) Preparation of graphene oxide dispersion: 0.5 mg of graphene oxide (transverse dimension 50 μm, monolayer ratio ≥99%, oxygen content 40%) was uniformly dispersed in 50 mL of water, stirred for 10 min, and ultrasonically treated at 100 W for 30 min to obtain graphene oxide dispersion.

[0060] (3) Assembly of porous liquid / graphene oxide composite membrane: The porous liquid dispersion obtained in step (1) and the graphene oxide dispersion obtained in step (2) were sequentially assembled on an alumina sheet porous support (average pore size of 1000 nm) through filtration. The pressure-driven method was pressure filtration with a pressure difference of 0.2 MPa. After the membrane layer was formed, it was dried at 60°C for 12 h to obtain the porous liquid / graphene oxide composite membrane.

[0061] Example 4

[0062] The porous liquid / graphene oxide composite membrane of this embodiment is a membrane layer in which porous liquid and graphene oxide are assembled on a porous support; wherein, the porous liquid includes a porous framework material and sterically hindered molecular chain segments; the sterically hindered molecular chain segments are crown ethers; the crown ether is 15-crown ether-5. The porous framework material is MOP-18.

[0063] The above-mentioned method for preparing porous liquid / graphene oxide composite membranes specifically includes the following steps:

[0064] (1) Preparation of porous liquid dispersion: 0.01 mol MOP-18 crystals and 0.05 mol 15-crown ether-5 were uniformly dispersed in 50 mL of chloroform, stirred for 20 min, and ultrasonically treated at 500 W for 10 min to obtain porous liquid dispersion.

[0065] (2) Preparation of graphene oxide dispersion: 1 mg of graphene oxide (lateral dimension 20 μm, monolayer ratio ≥99%, oxygen content 29%) was uniformly dispersed in 50 mL of methanol, stirred for 20 min, and ultrasonically treated at 500 W for 10 min to obtain graphene oxide dispersion.

[0066] (3) Assembly of the porous liquid / graphene oxide composite membrane: The porous liquid dispersion obtained in step (1) and the graphene oxide dispersion obtained in step (2) were sequentially assembled on a zirconia sheet porous support (average pore size of 100 nm) through filtration. The pressure-driven method was pressure filtration with a pressure difference of 0.6 MPa. After the membrane layer was formed, it was dried at 50 °C for 12 h to obtain the porous liquid / graphene oxide composite membrane.

[0067] Example 5

[0068] The porous liquid / graphene oxide composite membrane of this embodiment is a membrane layer in which porous liquid and graphene oxide are assembled on a porous support; wherein, the porous liquid includes a porous framework material and sterically hindered molecular chain segments; the sterically hindered molecular chain segments are crown ethers; the crown ether is 4-carboxybenzo-21-crown ether-7. The porous framework material is UiO-66.

[0069] The above-mentioned method for preparing porous liquid / graphene oxide composite membranes specifically includes the following steps:

[0070] (1) Preparation of porous liquid dispersion: 0.01 mol UiO-66 crystals and 0.05 mol 4-carboxybenzo-21-crown ether-7 were uniformly dispersed in 50 mL of water, stirred for 20 min, and ultrasonically treated at 500 W for 10 min to obtain porous liquid dispersion.

[0071] (2) Preparation of graphene oxide dispersion: 1 mg of graphene oxide (lateral dimension 20 μm, monolayer ratio ≥99%, oxygen content 29%) was uniformly dispersed in 50 mL of water, stirred for 20 min, and ultrasonically treated at 500 W for 10 min to obtain graphene oxide dispersion.

[0072] (3) Assembly of the porous liquid / graphene oxide composite membrane: The porous liquid dispersion obtained in step (1) and the graphene oxide dispersion obtained in step (2) were sequentially assembled on a mixed cellulose ester plate-type porous support (average pore size of 450 nm) through filtration. The pressure-driven method was pressure filtration with a pressure difference of 0.1 MPa. After the membrane layer was formed, it was dried at 50 °C for 12 h to obtain the porous liquid / graphene oxide composite membrane.

[0073] Comparative Example 1

[0074] As a comparative example of the method for preparing graphene oxide films without porous liquids according to the present invention, the specific steps include:

[0075] (1) Preparation of graphene oxide dispersion: 40 mg of graphene oxide (lateral dimension 20 μm, monolayer ratio ≥99%, oxygen content 29%) was uniformly dispersed in 200 mL of water, stirred for 30 min, and ultrasonically treated at 500 W for 10 min to obtain graphene oxide dispersion.

[0076] (2) Assembly of graphene oxide film: The graphene oxide dispersion obtained in step (1) was spin-coated onto a polyacrylonitrile flat porous support (average pore size of 10 nm). The spin-coating speed was 2000 rpm, the spin-coating time for each layer was 60 seconds, and the spin-coating cycle was 30 times. After the film was formed, it was dried at 45°C for 24 hours to obtain the graphene oxide film.

[0077] Comparative Example 2

[0078] As a comparative example of the method for preparing porous framework material / graphene oxide composite film without ionic liquid of the present invention, the specific steps include:

[0079] (1) Preparation of porous liquid dispersion: 0.005 mol CC3 crystals were uniformly dispersed in 200 mL methanol-water mixed solution (75% / 25% v / v), stirred for 30 min, and ultrasonically treated at 500 W for 10 min to obtain porous framework material dispersion.

[0080] (2) Preparation of graphene oxide dispersion: 40 mg of graphene oxide (lateral dimension 20 μm, monolayer ratio ≥99%, oxygen content 29%) was uniformly dispersed in 200 mL of water, stirred for 30 min, and ultrasonically treated at 500 W for 10 min to obtain graphene oxide dispersion.

[0081] (3) Assembly of porous framework material / graphene oxide composite film: The porous framework material dispersion obtained in step (1) and the graphene oxide dispersion obtained in step (2) were sequentially assembled on a polyacrylonitrile flat porous support (average pore size of 10 nm) by spin coating. The spin coating speed was 2000 rpm, the spin coating time for each layer was 60 seconds, and the number of spin coating cycles was 30. After the film was formed, it was dried at 45℃ for 24 h to obtain a porous liquid / graphene oxide composite film.

[0082] Comparative Example 3

[0083] As a comparative example of the method for preparing ionic liquid / graphene oxide composite films without porous framework materials according to the present invention, the specific steps include the following:

[0084] (1) Preparation of porous liquid dispersion: 0.025 mol 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide was uniformly dispersed in 200 mL methanol-water mixed solution (75% / 25% v / v), stirred for 30 min, and ultrasonically treated at 500 W for 10 min to obtain ionic liquid dispersion.

[0085] (2) Preparation of graphene oxide dispersion: 40 mg of graphene oxide (lateral dimension 20 μm, monolayer ratio ≥99%, oxygen content 29%) was uniformly dispersed in 200 mL of water, stirred for 30 min, and ultrasonically treated at 500 W for 10 min to obtain graphene oxide dispersion.

[0086] (3) Assembly of the ionic liquid / graphene oxide composite membrane: The ionic liquid dispersion obtained in step (1) and the graphene oxide dispersion obtained in step (2) were sequentially assembled on a polyacrylonitrile flat porous support (average pore size of 10 nm) by spin coating. The spin coating speed was 2000 rpm, the spin coating time for each layer was 60 seconds, and the number of spin coating cycles was 30. After the membrane was formed, it was dried at 45°C for 24 h to obtain the porous liquid / graphene oxide composite membrane.

[0087] Comparative Example 4

[0088] The difference between Comparative Example 4 and Example 1 is that the molar ratio of the porous framework material to the ionic liquid in Comparative Example 4 is 1:30. Specifically, the steps include:

[0089] (1) Preparation of porous liquid dispersion: 0.005 mol CC3 crystals and 0.15 mol 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide were uniformly dispersed in 200 mL methanol-water mixed solution (75% / 25% v / v), stirred for 30 min, and ultrasonically treated at 500 W for 10 min to obtain porous liquid dispersion.

[0090] (2) Preparation of graphene oxide dispersion: 40 mg of graphene oxide (lateral dimension 20 μm, monolayer ratio ≥99%, oxygen content 29%) was uniformly dispersed in 200 mL of water, stirred for 30 min, and ultrasonically treated at 500 W for 10 min to obtain graphene oxide dispersion.

[0091] (3) Assembly of the porous liquid / graphene oxide composite membrane: The porous liquid dispersion obtained in step (1) and the graphene oxide dispersion obtained in step (2) were sequentially assembled on a polyacrylonitrile flat porous support (average pore size of 10 nm) by spin coating. The spin coating speed was 2000 rpm, the spin coating time for each layer was 60 seconds, and the number of spin coating cycles was 30. After the membrane was formed, it was dried at 45°C for 24 h to obtain the porous liquid / graphene oxide composite membrane.

[0092] Performance testing

[0093] The membranes from Examples 1-5 and Comparative Examples 1-4 were subjected to permeation tests. The specific test method was as follows: the membrane was placed between the feed side and the permeation side of a self-made U-shaped permeation module, with the membrane surface facing the feed side. The effective area of ​​the membrane was 4.15 cm². 2 Add 75 mL of deionized water to the osmotic side and an equal volume of 0.5 mol / L KCl, NaCl, LiCl, or MgCl2 solution to the feed side. Stir the mixture on both sides using a rotor to eliminate concentration polarization. Measure the ion concentration on the osmotic side every 10 minutes using a conductivity meter for a total of 2 hours. Plot a linear regression graph of the osmotic concentration versus time, with the slope representing the ion permeation rate. Calculate the permeation rate using the formula:

[0094]

[0095] J s (mol m -2 h -1 ) represents the ion permeation rate, Δc / Δt (mg / L) -1 h -1 V represents the change in ion concentration per unit time on the osmotic side. p (L) represents the volume of the solution on the osmotic side, A(m 2 M represents the effective area of ​​the membrane. s (g mol -1 () represents the molecular weight of KCl, NaCl, LiCl, or MgCl2. Calculated according to the selectivity formula:

[0096]

[0097] J s1 Represents K + Permeation rate, J s2 Represents Mg 2+ Permeation rate.

[0098] The data for each group are shown in Table 1.

[0099] Table 1 Ion permeation performance data for each group

[0100]

[0101]

[0102] As shown in Table 1, the porous liquid / graphene oxide composite membranes of Examples 1-5 exhibit higher permeation rates and ion selectivity than the graphene oxide membrane of Comparative Example 1. The porous framework material / graphene oxide composite membrane of Comparative Example 2 shows improved permeation rates but insufficient selectivity. Conversely, the ionic liquid / graphene oxide composite membrane of Comparative Example 3 shows improved selectivity but insufficient permeability. In Comparative Example 4, the molar ratio of porous framework material to ionic liquid in the porous liquid is 1:30, resulting in a decrease in both permeation rate and ion selectivity of the prepared porous liquid / graphene oxide composite membrane. This demonstrates that the porous liquid / graphene oxide composite membranes prepared using specific porous liquid components and ratios of the present invention can achieve simultaneous improvement in ion permeability and selectivity, exhibiting significantly superior ion separation performance.

[0103] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A porous liquid / graphene oxide composite membrane, characterized in that, The composite membrane comprises a porous support and porous liquid material and graphene oxide sequentially and alternately assembled on the porous support; The porous liquid material comprises a porous framework material and sterically hindered molecular chain segments combined with the porous framework material; and the porous framework material comprises at least one of a metal-organic framework, a metal-organic cage, and a porous organic cage; the sterically hindered molecular chain segments comprise ionic liquids and / or crown ethers; in the porous liquid material, the molar ratio of the porous framework material to the sterically hindered molecular chain segments is 1:20 to 1:1; The porous support is a porous ultrafiltration membrane and / or microfiltration membrane.

2. The porous liquid / graphene oxide composite membrane as described in claim 1, characterized in that, The amount of the porous liquid material assembled on the porous support is 10-100 mg / cm2; And / or, the amount of graphene oxide assembled on the porous support is 0.1-2 mg / cm2.

3. The porous liquid / graphene oxide composite membrane as described in claim 1, characterized in that, In the porous framework material, the metal-organic framework is 2-methylimidazolium zinc salt and / or zirconium 1,4-carboxybenzene; the metal-organic cage is MOP-18; the porous organic cage is at least one of CC1 crystal, CC3 crystal, RCC3 crystal, CC5 crystal and KACC crystal; And / or, the ionic liquid in the sterically hindered molecular chain segment includes anionic and cationic groups, and the anionic group includes bis(trifluoromethanesulfonyl)imide, and the cationic group includes imidazole and / or pyridine.

4. The porous liquid / graphene oxide composite membrane as described in claim 1, characterized in that, The ionic liquid in the sterically hindered molecular chain segment includes at least one of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and N-butylpyridine bis(trifluoromethanesulfonyl)imide salt; And / or, the crown ether comprises at least one of 18-crown ether-6, 15-crown ether-5, dicyclohexano-18-crown ether-6, dibenzo-18-crown ether-6, and 4-carboxybenzo-21-crown ether-7.

5. The porous liquid / graphene oxide composite membrane as described in claim 1, characterized in that, The graphene oxide is a monodisperse graphene oxide nanosheet with a lateral size of 5-50 μm, a monolayer ratio of ≥99%, and an oxygen content of 20%-40%.

6. The porous liquid / graphene oxide composite membrane as described in claim 1, characterized in that, The porous support is made of at least one of polyacrylonitrile, polycarbonate, nylon, mixed cellulose ester, alumina, zirconium oxide, and titanium oxide. And / or, the porous support has a sheet or plate structure; And / or, the average pore size of the porous support is 10-1000 nm.

7. The method for preparing the porous liquid / graphene oxide composite membrane according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Preparation of porous liquid dispersion: The porous framework material is combined with sterically hindered molecular chain segments to obtain a porous liquid, and the porous liquid is uniformly dispersed in a solvent to obtain a porous liquid dispersion. (2) Preparation of graphene oxide dispersion: Graphene oxide is uniformly dispersed in a solvent to obtain graphene oxide dispersion. (3) Assembly of porous liquid / graphene oxide composite membrane: The porous liquid dispersion obtained in step (1) and the graphene oxide dispersion obtained in step (2) are assembled on a porous support to form a membrane layer. After drying, the porous liquid / graphene oxide composite membrane is obtained.

8. The method for preparing the porous liquid / graphene oxide composite membrane as described in claim 7, characterized in that, In step (1), the solvent includes at least one of methanol, DMF, DCM, formic acid, dichloromethane, chloroform, and methanol-water mixed solution; And / or, the concentration of the porous liquid dispersion obtained in step (1) is 0.01-0.5 mol / L; And / or, in step (2), the solvent includes at least one of water, DMSO, NMF, DMF, methanol, and methanol-water mixture; And / or, the concentration of the graphene oxide dispersion obtained in step (2) is 0.01-0.5 mg / mL.

9. The method for preparing the porous liquid / graphene oxide composite membrane as described in claim 7, characterized in that, In steps (1) and (2), the porous liquid and graphene oxide are uniformly dispersed in the solvent by stirring and / or ultrasonic treatment, respectively; wherein the stirring time is 10-60 min; the ultrasonic power is 100-700 W and the ultrasonic time is 5-30 min. And / or, in step (3), the assembly method includes spin coating and / or filtration; The spin coating process is as follows: the porous liquid dispersion and the graphene oxide dispersion are sequentially and alternately spin-coated onto the porous support, the spin coating speed is 500-2500 rpm, the single spin coating time for each layer is 30-120 seconds, and the number of spin coating cycles is 5-60. The filtration steps are as follows: the porous liquid dispersion and the graphene oxide dispersion are mixed evenly by stirring to obtain a film-forming solution, and then assembled on the porous support by pressure driving; the pressure driving method is pressure filtration or vacuum suction, with a pressure difference of 0.1-1.0 MPa.

10. The application of the porous liquid / graphene oxide composite membrane according to any one of claims 1 to 6 in the preparation of ion separation products.

Images