Ionic covalent organic framework membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of novel separation membrane materials, and discloses an ionic covalent organic framework membrane as well as a preparation method and application thereof. An amine monomer and an aldehyde monomer are respectively dissolved in water and an organic solvent, and the continuous defect-free ionic covalent organic framework membrane is formed by in-situ growth on the surface of a carboxylated porous support base membrane through a limited interface polymerization method. And the membrane structure and the separation performance can be optimized by regulating and controlling the monomer concentration and the reaction time. The preparation process is simple, convenient and controllable, the prepared membrane is applied to pervaporation butanol-water separation, high permeability and high selectivity are shown, and good long-term operation stability is achieved. In addition, the prepared membrane can also be applied to separation of other types of alcohol-water and separation of pervaporation salt-water, and has good universality application.

Description

Technical Field

[0001] The invention belongs to the technical field of novel separation membrane materials, and specifically relates to an ionic covalent organic framework membrane and a preparation method and application thereof. Background Art

[0002] Membrane separation is an efficient and energy-saving technology with the advantages of high selectivity, simple operation, and environmental protection. High-performance membrane materials are the key to membrane separation technology. Organic polymer membranes, as the most promising industrial membrane materials, are usually restricted by the trade-off effect and it is difficult to achieve high permeability and high selectivity at the same time. Inorganic membranes have regular pores and stable structures, but they are fragile and have harsh preparation conditions. Therefore, it is of great significance to develop a new type of membrane material that has both the toughness of organic polymers and the regular pores and stable structures of inorganic materials to obtain separation membranes with high permeability, high selectivity and high stability.

[0003] Organic molecular sieve membranes prepared based on microporous organic materials have received extensive attention in the field of molecular separation. Among them, covalent organic frameworks (COFs) are a new type of crystalline porous materials chemically assembled from molecular building blocks. They have the characteristics of regular pores, high porosity, and controllable structure, making them a promising candidate for high-performance membrane materials. As a new generation of organic molecular sieve membrane materials, the long-range ordered pore structure of COF is conducive to the rapid transmission of molecules. The diversity of COF molecular building blocks gives the pores and framework structures adjustability, providing the possibility for the regulation of the physicochemical properties of the pores. Among them, the ionic COF has regularly arranged ionic groups on the pore walls, which can specifically act on the target molecules, giving it new functions different from neutral COF, and has great prospects in precise molecular separation. However, traditional COF synthesis strategies usually form insoluble and difficult-to-process microcrystalline powders, and cannot form continuous defect-free COF membranes. Harsh synthesis conditions such as high temperature are not conducive to the large-scale preparation of COF membranes. In particular, ionic COF membranes usually have slow reaction rates and low yields due to the steric hindrance and strong electron-withdrawing effect of ionic groups, which limits their preparation and application. The literature (Dual-activation interfacial polymerization based anionic covalentorganic framework nanofiltration membrane for high-flux dye separation, Chemical Engineering Journal, 456 (2023), 141008) reported that a self-supporting ionic COF membrane was prepared by a dual-activation interfacial polymerization strategy for dye separation; a Chinese invention patent (CN115501763A) provided an interfacial polymerization strategy to prepare a guanidine-containing ionic COF membrane for ion separation. However, both are not suitable for the separation of liquid small molecule mixtures. At present, it is still a huge challenge to directly prepare a continuous defect-free ionic COF film on the surface of a porous support base membrane and use it for the separation of liquid small molecule mixtures. Summary of the invention

[0004] In view of the above problems, the present invention provides a method for preparing an ionic covalent organic framework membrane. Through the carboxylation modification of the porous supporting base membrane, the ionic covalent organic framework can be confined to grow on the surface of the porous supporting base membrane to form a continuous, defect-free and structurally complete membrane layer; the covalent bonding mode helps to strengthen the interfacial interaction and maintain the stability of the membrane structure, so that it can resist the adverse evolution of the membrane structure in the liquid environment; the hydrophilic ionic groups in the membrane can enhance the selective separation of water molecules. The process is simple and controllable, showing a separation performance superior to that of polymer membranes.

[0005] In order to achieve the purpose of the present invention, the technical solution adopted is as follows:

[0006] The method for preparing the ionic covalent organic framework membrane prepared by the present invention comprises the following steps:

[0007] Dissolving the amine monomer and the aldehyde monomer in water and an organic solvent respectively to obtain an aqueous phase solution and an oil phase solution;

[0008] The carboxylated porous support base membrane is fixed on the device, and the aqueous solution and the oily solution are added to both sides of the device respectively, and the device is sealed and allowed to react;

[0009] The membrane is taken out and washed to remove the residual unreacted monomers, thereby obtaining an ionic covalent organic framework membrane.

[0010] As a preferred solution of the method for preparing the ionic covalent organic framework membrane of the present invention, the porous supporting base membrane can be one of carboxylated polyacrylonitrile ultrafiltration membrane, carboxylated polyvinyl alcohol ultrafiltration membrane and carboxylated polyvinylidene fluoride ultrafiltration membrane.

[0011] The carboxylation modification method of the porous support base membrane can be the carboxylation treatment method for the porous support base membrane in the prior art in the art. For example, polyvinyl alcohol ultrafiltration membrane and polyvinylidene fluoride ultrafiltration membrane can be carboxylated by a physical coating method, and polyacrylonitrile ultrafiltration membrane can be carboxylated by a chemical grafting method.

[0012] As a preferred embodiment of the method for preparing the ionic covalent organic framework membrane of the present invention, the method for preparing the carboxylated polyacrylonitrile ultrafiltration membrane comprises firstly heat-treating the polyacrylonitrile ultrafiltration membrane with a sodium hydroxide or potassium hydroxide aqueous solution having a concentration of 1.0-3.0 mol / L at 40-80°C for 1.0-3.0 h, and then treating it with a morpholineethanesulfonic acid buffer solution containing hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

[0013] As a preferred scheme of the preparation method of the ionic covalent organic framework membrane of the present invention, the amine monomer is 2,5-diaminobenzenesulfonic acid or 2,5-diaminobenzene-1,4-disulfonic acid, and the concentration is 1-20mmol / L; the aldehyde monomer is trimesaldehyde or trialdehyde phloroglucinol, and the concentration is 0.5-10mmol / L.

[0014] More preferably, the concentration of the aldehyde monomer is 1-10 mmol / L;

[0015] Even more preferably, the concentration of the aldehyde monomer is 3-10 mmol / L, and the concentration of the amine monomer is 5-20 mmol / L.

[0016] As a preferred embodiment of the method for preparing the ionic covalent organic framework membrane of the present invention, the reaction time is 12-168h;

[0017] More preferably, the reaction time is 48-96h;

[0018] Even more preferably, the reaction time is 72-96h.

[0019] As a preferred embodiment of the method for preparing the ionic covalent organic framework membrane of the present invention, the organic solvent in the oil phase solution is n-octanoic acid or n-hexane.

[0020] Another object of the present invention is to provide an ionic covalent organic framework membrane.

[0021] Another object of the present invention is to provide an ionic covalent organic framework membrane for use in pervaporation alcohol-water separation or pervaporation salt-water separation.

[0022] As a preferred solution for applying the ionic covalent organic framework membrane of the present invention to pervaporation alcohol-water separation, the alcohol includes any one of ethanol, isopropanol, isobutanol and butanol, and the alcohol concentration is 80-95wt%.

[0023] As a preferred solution for applying the ionic covalent organic framework membrane of the present invention to pervaporation salt-water separation, the salt is sodium chloride, and the salt concentration is 0.1-7.5 wt %.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention modifies the porous support base membrane by carboxylation, thereby inducing the confined growth of the ionic covalent organic framework on the surface of the porous support base membrane to form a continuous membrane layer; and the covalent bonding mode maintains the stability of the membrane structure, so that it can resist the adverse evolution of the membrane structure in the liquid environment. The membrane structure and separation performance can be optimized by changing the organic monomer concentration and reaction time; the prepared ionic covalent organic framework membrane pores are uniformly distributed with hydrophilic ion groups, which endows the membrane pore channels with water molecule selective transmission characteristics, which helps to improve the membrane's selective separation of water molecules. The method is simple, controllable, green and environmentally friendly, and can be prepared under mild conditions.

[0026] The prepared ionic covalent organic framework membrane is applied to pervaporation alcohol-water separation, which can show high permeation flux and high separation factor, and has good long-term separation stability; the prepared ionic covalent organic framework membrane is applied to pervaporation salt-water separation, which also shows good permeation flux and high retention efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0028] Figure 1 The surface and cross-section scanning electron microscope images of membrane 1;

[0029] Figure 2 The surface and cross-section scanning electron microscope images of membrane 2;

[0030] Figure 3 The surface and cross-section scanning electron microscope images of membrane 3;

[0031] Figure 4 The surface and cross-section scanning electron microscope images of membrane 4;

[0032] Figure 5 Surface and cross-sectional SEM images of membrane 5;

[0033] Figure 6 The surface scanning electron microscope image of the comparative film;

[0034] Figure 7 This is the long-term stability diagram of membrane 1. DETAILED DESCRIPTION

[0035] In order to further understand the purpose, content and advantages of the present invention, the specific embodiments of the present invention are now described in detail as follows, but it is not limited to the following examples, and it is freely matched according to actual conditions. The endpoints and any values ​​of the scope disclosed in this article are not limited to the precise scope and value. For numerical ranges, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between separate point values, one or more new numerical ranges can be combined with each other, and these numerical ranges should be considered as specifically disclosed in this article.

[0036] The separation performance testing method of the membrane in the following examples and comparative examples is as follows:

[0037] The prepared membrane material is applied to pervaporation alcohol-water separation and pervaporation salt-water separation, the alcohol content in the raw liquid is 90wt%, the temperature is 80°C, and the permeation flux and separation factor of the ionic covalent organic framework membrane are measured; the sodium chloride content in the raw liquid is 3.5wt%, the temperature is 80°C, and the permeation flux and retention rate of the ionic covalent organic framework membrane are measured. It should be noted that this test method is only for the convenience of parallel comparison of membrane material performance, and does not mean that the membrane material provided by the present invention can only be used for pervaporation alcohol-water separation or pervaporation salt-water separation under the above conditions. The membrane material provided by the present invention can be used for pervaporation separation of alcohol-water and salt-water of any concentration required to be separated in the art, for example, the alcohol concentration is 80-95wt%, and the salt concentration is 0.1-7.5wt%.

[0038] The present invention provides a method for preparing an ionic covalent organic framework membrane, comprising the following steps:

[0039] Dissolving the amine monomer and the aldehyde monomer in water and an organic solvent respectively to obtain an aqueous phase solution and an oil phase solution;

[0040] The carboxylated porous support base membrane is fixed on the device, and the aqueous solution and the oily solution are added to both sides of the device respectively, and the device is sealed and allowed to react;

[0041] The membrane is taken out and washed to remove the residual unreacted monomers, thereby obtaining an ionic covalent organic framework membrane.

[0042] As a preferred embodiment, the amine monomer is 2,5-diaminobenzenesulfonic acid or 2,5-diaminobenzene-1,4-disulfonic acid, and the concentration is 1-20mmol / L; the aldehyde monomer is trimesic acid or trialdehyde phloroglucinol, and the concentration is 0.5-10mmol / L; the reaction time is 12-168h. The carboxylated porous support base membrane actually refers to the porous support base membrane after modification, and the membrane surface is uniformly modified with carboxyl groups, which is conducive to the confined growth of the covalent organic framework on the surface of the base membrane, forming a continuous defect-free membrane layer, and the covalent bonding mode maintains the stability of the membrane structure, so that it can resist the adverse evolution of the membrane structure in the liquid environment. On this basis, the concentration of amine monomers and aldehyde monomers, as well as the reaction time, can be controlled to optimize the membrane structure and separation performance. Through this optimization, the membrane material can be used for pervaporation alcohol-water separation or pervaporation salt-water separation, and good separation effects can be obtained. When used for pervaporation butanol-water separation, the permeate flux is 9000g m -2 h -1 Above, the separation factor is above 175.

[0043] As a further preferred embodiment, the concentration of the aldehyde monomer is controlled to be 1-10 mmol / L, the reaction time is 48-96 h, and when the membrane material is used for pervaporation butanol-water separation, the permeate flux is 9000 g m -2 h -1 Above, the separation factor is above 1200.

[0044] As a further preferred embodiment, the concentration of the aldehyde monomer is controlled to be 3-10 mmol / L, the concentration of the amine monomer is controlled to be 5-20 mmol / L, the reaction time is controlled to be 72-96 h, and when the membrane material is used for pervaporation butanol-water separation, the permeate flux can be close to 10000 g m -2 h -1 In some specific cases, the permeate flux can even reach 12000 g m -2 h -1 The separation factor can reach more than 1700, for example, the concentration of aldehyde monomers is 3-10 mmol / L, the concentration of amine monomers is 10-20 mmol / L, and the reaction time is 72-96 h.

[0045] The following is further described in detail with reference to some specific embodiments and comparative examples:

[0046] Example 1

[0047] This embodiment provides a method for preparing an ionic covalent organic framework membrane, specifically:

[0048] 1) placing the polyacrylonitrile ultrafiltration membrane in a 1.5 mol / L, 55° C. sodium hydroxide solution for heat treatment for 1.0 h, then treating it with a morpholineethanesulfonic acid solution containing hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide for 4 h, repeatedly washing it with deionized water, and rolling the water stains on the membrane surface with a rubber roller to obtain a carboxylated polyacrylonitrile ultrafiltration membrane;

[0049] 2) Prepare a 5.0 mmol / L octanoic acid solution of trialdehyde pyrogallol (oil phase solution) and a 10 mmol / L 2,5-diaminobenzenesulfonic acid aqueous solution (aqueous phase solution), respectively, fix the carboxylated polyacrylonitrile ultrafiltration membrane on the device, add the aqueous phase solution and the oil phase solution on both sides of the device, seal it and let it react at room temperature for 72 hours; take out the membrane, wash it with methanol and deionized water to remove the residual unreacted monomers, and obtain an ionic covalent organic framework membrane, recorded as membrane 1.

[0050] Membrane 1 was used for pervaporation butanol-water separation, with a permeate flux of 12620 g m -2 h -1 , the separation factor is 3161; membrane 1 is applied to pervaporation isopropanol-water separation, and the permeate flux is 10432 g m -2 h-1 , the separation factor is 1529; membrane 1 is applied to pervaporation isobutanol-water separation, and the permeate flux is 10601 g m -2 h -1 , the separation factor is 1629; membrane 1 is applied to pervaporation salt-water separation, and the permeate flux is 75 kg m -2 h -1 , the retention rate is 99.94%. Figure 1 Surface and cross-sectional scanning electron microscopy images of membrane 1.

[0051] Example 2

[0052] The difference between this embodiment and embodiment 1 is that the reaction time in step 2) is adjusted to 12 hours, and the processes of the remaining steps are all referred to embodiment 1, to obtain an ionic covalent organic framework membrane, which is recorded as membrane 2.

[0053] Membrane 2 was used for pervaporation butanol-water separation, with a permeate flux of 13152 g m -2 h -1 , the separation factor is 175. Figure 2 Surface and cross-sectional scanning electron microscopy images of membrane 2.

[0054] Example 3

[0055] The difference between this embodiment and embodiment 1 is that the reaction time in step 2) is adjusted to 24 hours, and the processes of the remaining steps are all referred to embodiment 1, to obtain an ionic covalent organic framework membrane, which is recorded as membrane 3.

[0056] Membrane 3 was used for pervaporation butanol-water separation, with a permeate flux of 11316 g m -2 h -1 , the separation factor is 559. Figure 3 Surface and cross-sectional scanning electron microscopy images of membrane 3.

[0057] Example 4

[0058] The difference between this embodiment and embodiment 1 is that the reaction time in step 2) is adjusted to 48 hours, and the processes of the remaining steps are all referred to embodiment 1, to obtain an ionic covalent organic framework membrane, which is recorded as membrane 4.

[0059] Membrane 4 was used for pervaporation butanol-water separation, with a permeate flux of 9981 g m -2 h -1 , the separation factor is 1304. Figure 4 Surface and cross-sectional scanning electron microscopy images of membrane 4.

[0060] Example 5

[0061] The difference between this embodiment and embodiment 1 is that the reaction time in step 2) is adjusted to 96 hours, and the processes of the remaining steps are all referred to embodiment 1, to obtain an ionic covalent organic framework membrane, which is recorded as membrane 5.

[0062] Membrane 5 was used for pervaporation butanol-water separation, with a permeate flux of 10641 g m -2 h -1 , the separation factor is 2430. Figure 5 Surface and cross-sectional scanning electron microscopy images of membrane 5.

[0063] Table 1

[0064]

[0065] The reaction time affects the formation and crystallization process of the ionic covalent organic framework membrane, thereby affecting the separation performance of the membrane. The imine covalent organic framework conforms to the dynamic imine exchange mechanism. The organic monomers polymerize quickly in the early stage of the reaction, usually forming an amorphous structure. As the reaction time increases, the dynamic process of imine bond breaking and reforming gradually self-repairs the defects, forming a more orderly and stable structure with a crystal structure. The ionic groups are regularly arranged in the pore walls with higher crystallinity, forming a fast selective transmission channel for water molecules, which is conducive to the fast selective permeation of water molecules. At the same time, as the reaction time increases, the ionic covalent organic framework membrane layer gradually grows and covers the surface of the porous supporting base membrane. However, when the reaction time is too long, the permeation flux and separation factor of the membrane decrease. Therefore, optimizing the reaction time can optimize the membrane structure and obtain high separation performance.

[0066] Example 6

[0067] The difference between this embodiment and embodiment 1 is that the concentration of trialdehyde pyrogallol in step 2) is adjusted to 10 mmol / L, and the concentration of 2,5-diaminobenzenesulfonic acid is adjusted to 1.0 mmol / L, and the remaining steps and processes are all based on embodiment 1 to obtain the ionic covalent organic framework membrane of this embodiment, which is recorded as membrane 6.

[0068] Membrane 6 was used for pervaporation butanol-water separation, with a permeate flux of 9256 g m -2 h -1 , the separation factor is 1255.

[0069] Example 7

[0070] The difference between this embodiment and embodiment 1 is that the concentration of trialdehyde pyrogallol in step 2) is adjusted to 10 mmol / L, and the concentration of 2,5-diaminobenzenesulfonic acid is adjusted to 5.0 mmol / L, and the remaining steps and processes are all based on embodiment 1 to obtain the ionic covalent organic framework membrane of this embodiment, which is recorded as membrane 7.

[0071] Membrane 7 was used for pervaporation butanol-water separation, with a permeate flux of 10789 g m -2 h -1 , the separation factor is 1697.

[0072] Example 8

[0073] The difference between this embodiment and embodiment 1 is that the concentration of trialdehyde pyrogallol in step 2) is adjusted to 10 mmol / L, and the concentration of 2,5-diaminobenzenesulfonic acid is adjusted to 10 mmol / L, and the remaining steps and processes are all referred to embodiment 1, to obtain the ionic covalent organic framework membrane of this embodiment, which is recorded as membrane 8.

[0074] Membrane 8 was used for pervaporation butanol-water separation, with a permeate flux of 9719 g m -2 h -1 , the separation factor is 2682.

[0075] Example 9

[0076] The difference between this embodiment and embodiment 1 is that the concentration of trialdehyde pyrogallol in step 2) is adjusted to 10 mmol / L, and the concentration of 2,5-diaminobenzenesulfonic acid is adjusted to 20 mmol / L, and the remaining steps and processes are all referred to embodiment 1, to obtain the ionic covalent organic framework membrane of this embodiment, which is recorded as membrane 9.

[0077] Membrane 9 was used for pervaporation butanol-water separation, with a permeate flux of 10133 g m -2 h -1 , the separation factor is 2909.

[0078] Example 10

[0079] The difference between this embodiment and embodiment 1 is that the concentration of trialdehyde phloroglucinol in step 2) is adjusted to 0.5 mmol / L, and the remaining steps and processes are all referred to embodiment 1, to obtain the ionic covalent organic framework membrane of this embodiment, which is recorded as membrane 10.

[0080] Membrane 10 was used for pervaporation butanol-water separation, with a permeate flux of 11245 g m -2 h -1 , the separation factor is 821.

[0081] Embodiment 11

[0082] The difference between this embodiment and embodiment 1 is that the concentration of trialdehyde phloroglucinol in step 2) is adjusted to 1.0 mmol / L, and the remaining steps and processes are all referred to embodiment 1, to obtain the ionic covalent organic framework membrane of this embodiment, which is recorded as membrane 11.

[0083] Membrane 11 was used for pervaporation butanol-water separation, with a permeate flux of 9428 g m-2 h -1 , the separation factor is 1232.

[0084] Example 12

[0085] The difference between this embodiment and embodiment 1 is that the concentration of trialdehyde phloroglucinol in step 2) is adjusted to 3.0 mmol / L, and the remaining steps and processes are all referred to embodiment 1, to obtain the ionic covalent organic framework membrane of this embodiment, which is recorded as membrane 12.

[0086] Membrane 12 was used for pervaporation butanol-water separation, with a permeate flux of 12339 g m -2 h -1 , the separation factor is 1796.

[0087] Embodiment 13

[0088] The difference between this embodiment and embodiment 1 is that the trialdehyde phloroglucinol in step 2) of embodiment 1 is replaced by trimesic acid, and the remaining steps and processes are all based on embodiment 1 to obtain the ionic covalent organic framework membrane of this embodiment, which is recorded as membrane 13.

[0089] Membrane 13 was used for pervaporation butanol-water separation, with a permeate flux of 9662 g m -2 h -1 , the separation factor is 1267.

[0090] Embodiment 14

[0091] The difference between this embodiment and embodiment 1 is that the 2,5-diaminobenzenesulfonic acid in step 2) of embodiment 1 is replaced by 2,5-diaminobenzene-1,4-disulfonic acid, and the remaining steps and processes are all based on embodiment 1 to obtain the ionic covalent organic framework membrane of this embodiment, which is recorded as membrane 14.

[0092] Membrane 14 was used for pervaporation butanol-water separation, with a permeate flux of 9175 g m -2 h -1 , the separation factor is 2065.

[0093] Table 2

[0094]

[0095]

[0096] Regulating the concentration of organic monomers will affect the separation performance of ionic covalent organic framework membranes. As the concentration of amine monomers increases, the permeation flux of the membrane decreases and then stabilizes, while the separation factor gradually increases. As the concentration of aldehyde monomers increases, the permeation flux of the membrane is relatively stable, while the separation factor first increases and then changes little. It can be seen that increasing the concentration of organic monomers helps to form a complete membrane layer on the surface of the porous support base membrane. In addition, the hydrophilic ionic groups are regularly arranged in the pore walls with higher crystallinity, which enhances the selective transmission of water molecules and achieves high permeability and high selectivity. In addition, by changing the type of organic monomers, a continuous and complete ionic covalent organic framework membrane can also be prepared, and it exhibits good separation performance, indicating that this method has a certain universality.

[0097] Comparative Example 1

[0098] The difference between this comparative example and Example 1 is that in the adjustment step 1), the treatment with the morpholineethanesulfonic acid solution of hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is no longer performed, and the remaining steps and processes are all referred to Example 1 to obtain the ionic covalent organic framework membrane of this comparative example, which is recorded as comparative membrane 1.

[0099] Comparative membrane 1 was used for pervaporation butanol-water separation, and the permeate flux was 3067 g m -2 h -1 , the separation factor is 1115. Figure 6 This is a surface scanning electron microscope image of comparative film 1.

[0100] Table 3

[0101]

[0102] The surface of the ionic covalent organic framework membrane formed on the porous support membrane without carboxyl modification is rough ( Figure 6 ), the interface between the membrane layer and the support layer is weak, the separation performance is not ideal, especially the permeation flux is too low, this is because the disordered growth causes it to be amorphous and the pore channels are no longer connected. The surface of the porous support base membrane modified by carboxylation forms a uniform and continuous ionic covalent organic framework membrane layer, and the permeation flux and separation factor are both high. This is because the functionalization of the porous support base membrane is conducive to the confined anchoring of organic monomers on the surface of the base membrane, inducing the confined growth of the covalent organic framework on the surface of the porous support base membrane.

[0103] In summary, the present invention provides a method for preparing an ionic covalent organic framework membrane, and the surface functionalization of the porous support base membrane is conducive to the confined growth of the ionic covalent organic framework on its surface. The preparation method of the present invention is simple and controllable, and the prepared ionic covalent organic framework membrane can be applied to pervaporation alcohol-water separation and pervaporation salt-water separation, and exhibits good long-term separation stability in the pervaporation alcohol-water separation process, and has broad industrial application prospects, which has very important guiding significance for the preparation of porous framework structure membranes.

[0104] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can make many modifications without departing from the purpose of the present invention, which are all protected by the present invention.

[0105] The above is only a preferred specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field within the technical scope disclosed by the present invention, according to the technical solution and its concept of the present invention, shall be covered within the protection scope of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for preparing an ionic covalent organic framework membrane, characterized in that: The following steps are included: Dissolving an amine monomer and an aldehyde monomer in water and an organic solvent respectively to obtain an aqueous phase solution and an oil phase solution; the amine monomer is 2,5-diaminobenzenesulfonic acid or 2,5-diaminobenzene-1,4-disulfonic acid, with a concentration of 1-20 mmol / L; the aldehyde monomer is trimesaldehyde or trialdehyde phloroglucinol, with a concentration of 0.5-10 mmol / L; The carboxylated porous support base membrane is fixed on the device, and the aqueous solution and the oil phase solution are added to both sides of the device respectively, and the device is sealed and allowed to react for 12-168 hours; The membrane is taken out and washed to remove the residual unreacted monomers, thereby obtaining an ionic covalent organic framework membrane.

2. The method for preparing an ionic covalent organic framework membrane according to claim 1, characterized in that: The porous supporting base membrane comprises one of a carboxylated polyacrylonitrile ultrafiltration membrane, a carboxylated polyvinyl alcohol ultrafiltration membrane or a carboxylated polyvinylidene fluoride ultrafiltration membrane.

3. The method for preparing an ionic covalent organic framework membrane according to claim 1, characterized in that: The preparation method of carboxylated polyacrylonitrile ultrafiltration membrane comprises the following steps: firstly, heat-treating the polyacrylonitrile ultrafiltration membrane with a sodium hydroxide or potassium hydroxide aqueous solution with a concentration of 1.0-3.0 mol / L at 40-80° C. for 1.0-3.0 h, and then treating it with a morpholineethanesulfonic acid buffer solution containing hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

4. The method for preparing an ionic covalent organic framework membrane according to claim 1, characterized in that: The concentration of the aldehyde monomer is 1-10 mmol / L, and the reaction time is 48-96 hours.

5. The method for preparing an ionic covalent organic framework membrane according to claim 1, characterized in that: The concentration of the aldehyde monomer is 3-10 mmol / L, the concentration of the amine monomer is 5-20 mmol / L, and the reaction time is 72-96 hours.

6. The method for preparing an ionic covalent organic framework membrane according to claim 1, characterized in that: The organic solvent used for the oil phase solution is n-octanoic acid or n-hexane.

7. The method for preparing an ionic covalent organic framework membrane according to claim 1, characterized in that: The aldehyde monomer is trialdehyde phloroglucinol, and the concentration is 3-10 mmol / L; the amine monomer is 2,5-diaminobenzenesulfonic acid, and the concentration is 5-20 mmol / L; and the reaction time is 72-96 hours.

8. An ionic covalent organic framework membrane prepared according to any one of the preparation methods of claims 1-7.

9. The use of the ionic covalent organic framework membrane according to claim 8, characterized in that: Used for pervaporation alcohol-water separation, or pervaporation salt-water separation.

10. The use of the ionic covalent organic framework membrane according to claim 9, characterized in that: The alcohol is any one of ethanol, isopropanol, isobutanol and butanol, and the alcohol concentration is 80-95wt%; the salt is sodium chloride, and the salt concentration is 0.1-7.5wt%.

Images