An ionic covalent organic framework membrane and a preparation method and application thereof

Abstract

The application 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 a continuous defect-free ionic covalent organic framework membrane is formed in situ on the surface of a carboxylated porous support base membrane through a limited interface polymerization method. The membrane structure and separation performance can be optimized by adjusting the monomer concentration and reaction time. The preparation process is simple and controllable, the prepared membrane is applied to pervaporation butanol-water separation, and high permeability and high selectivity are exhibited, and the prepared membrane also has good long-term operation stability. In addition, the prepared membrane can also be applied to other kinds of alcohol-water separation and pervaporation salt-water separation, and has good universal application.

Description

Technical Field

[0001] This invention belongs to the field of novel separation membrane materials technology, specifically relating to an ionic covalent organic framework membrane, its preparation method, and its application. Background Technology

[0002] Membrane separation is a highly efficient and energy-saving technology with advantages such as high selectivity, ease of operation, and environmental friendliness. High-performance membrane materials are key to membrane separation technology. Organic polymer membranes, as the most promising industrial membrane materials, are often limited by the trade-off effect, making it difficult to simultaneously achieve high permeability and high selectivity. Inorganic membranes possess regular pores and stable structures, but suffer from fragility and demanding preparation conditions. Therefore, developing a new type of membrane material that combines the toughness of organic polymers with the regular pores and stable structure of inorganic materials is of great significance for obtaining separation membranes with high permeability, high selectivity, and high stability.

[0003] Organic molecular sieve membranes based on microporous organic materials have attracted widespread attention in the field of molecular separation. Among them, covalent organic frameworks (COFs) are a new type of crystalline porous material chemically assembled from molecular building blocks, possessing characteristics such as regular pores, high porosity, and controllable structure, making them promising candidates for high-performance membrane materials. As a new generation of organic molecular sieve membrane materials, the long-range ordered pore structure of COFs facilitates rapid molecular transport, and the diversity of COF molecular building blocks endows the pore and framework structures with tunability, providing possibilities for the regulation of pore physicochemical properties. Ionic COFs, in particular, have regularly arranged ionic groups on their pore walls, which can specifically act on target molecules, endowing them with new functions different from neutral COFs, and showing great promise in precise molecular separation. However, traditional COF synthesis strategies usually result in insoluble and difficult-to-process microcrystalline powders, making it impossible to form continuous, defect-free COF membranes. Harsh synthesis conditions such as high temperatures are not conducive to the large-scale preparation of COF membranes. In particular, ionic COF membranes, due to the steric hindrance and strong electron-withdrawing effect of ionic groups, typically have slow reaction rates and low yields, limiting 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) reports the preparation of a self-supported ionic COF membrane using a dual-activation interfacial polymerization strategy for dye separation; Chinese invention patent (CN115501763A) provides an interfacial polymerization strategy for preparing a guanidine-containing ionic COF membrane for ion separation. However, neither of these methods is suitable for the separation of small liquid molecule mixtures. Currently, directly preparing continuous, defect-free ionic COF films on the surface of porous supported membranes for the separation of small liquid molecule mixtures remains a significant challenge. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for preparing an ionic covalent organic framework membrane. Through carboxylation modification of a porous supporting membrane, an ionic covalent organic framework can be confined and grown on the surface of the porous supporting membrane, forming a continuous, defect-free, and structurally complete membrane layer. The covalent bonding mode helps to strengthen interfacial interactions, maintain the stability of the membrane structure, and enable it to resist adverse evolution of the membrane structure in a liquid environment. The hydrophilic ionic groups within the membrane can enhance the selective separation of water molecules. This process is simple and controllable, exhibiting separation performance superior to that of polymer membranes.

[0005] To achieve the objectives of this invention, the following technical solution is adopted:

[0006] The method for preparing the ionic covalent organic framework membrane of the present invention includes the following steps:

[0007] Amine monomers and aldehyde monomers were dissolved in water and organic solvents, respectively, to obtain aqueous solutions and oil solutions.

[0008] A carboxylated porous support membrane was fixed on the device, and an aqueous solution and an oil solution were added to both sides of the device, respectively. After sealing, the device was allowed to stand for reaction.

[0009] The membrane was removed and washed to remove any remaining unreacted monomers, yielding an ionic covalent organic framework membrane.

[0010] As a preferred embodiment of the preparation method of the ionic covalent organic framework membrane of the present invention, the porous supporting substrate 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 for porous support membranes can be any of the existing carboxylation treatment methods for porous support membranes in the art. For example, polyvinyl alcohol ultrafiltration membranes and polyvinylidene fluoride ultrafiltration membranes can be modified by carboxylation through physical coating methods, while polyacrylonitrile ultrafiltration membranes can be modified by carboxylation through chemical grafting methods.

[0012] As a preferred embodiment of the preparation method of the ionic covalent organic framework membrane of the present invention, the method for preparing the carboxylated polyacrylonitrile ultrafiltration membrane includes: firstly, heat-treating the polyacrylonitrile ultrafiltration membrane with an aqueous solution of sodium hydroxide or potassium hydroxide at 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 morpholine ethanesulfonic acid buffer solution containing hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

[0013] In a preferred embodiment 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, with a concentration of 1-20 mmol / L; the aldehyde monomer is pyromellitic methyl ether or trialdehyde-resorcinol, with a concentration of 0.5-10 mmol / L.

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

[0015] 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] In a preferred embodiment of the method for preparing the ionic covalent organic framework membrane of the present invention, the reaction time is 12-168 h.

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

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

[0019] In 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 embodiment of the ionic covalent organic framework membrane described in this invention for pervaporation alcohol-water separation, wherein the alcohol includes any one of ethanol, isopropanol, isobutanol, and butanol, and the alcohol concentration is 80-95 wt%.

[0023] As a preferred embodiment of the ionic covalent organic framework membrane described in this invention for pervaporation salt-water separation, wherein the salt is sodium chloride with a concentration of 0.1-7.5 wt%.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] This invention induces the confined growth of ionic covalent organic frameworks on the surface of a porous support membrane through carboxylation modification, forming a continuous membrane layer. The covalent bonding mode maintains the stability of the membrane structure, enabling it to resist adverse evolution in liquid environments. The membrane structure and separation performance can be optimized by changing the concentration of organic monomers and the reaction time. The prepared ionic covalent organic framework membrane has uniformly distributed hydrophilic ionic groups in its pores, endowing the membrane channels with selective water molecule transport properties, which helps to improve the selective separation of water molecules. This method is simple, controllable, environmentally friendly, and can be prepared under mild conditions.

[0026] When the prepared ionic covalent organic framework membrane is applied to pervaporation alcohol-water separation, it exhibits high permeation flux and high separation factor, as well as good long-term separation stability. When the prepared ionic covalent organic framework membrane is applied to pervaporation salt-water separation, it also exhibits good permeation flux and high retention efficiency. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0028] Figure 1 Here are scanning electron microscope (SEM) images of the surface and cross-section of membrane 1;

[0029] Figure 2 Here are scanning electron microscope (SEM) images of the surface and cross-section of membrane 2;

[0030] Figure 3 Here are scanning electron microscope (SEM) images of the surface and cross-section of membrane 3;

[0031] Figure 4 Scanning electron microscope (SEM) images of the surface and cross-section of membrane 4;

[0032] Figure 5 Here are scanning electron microscope (SEM) images of the surface and cross-section of membrane 5;

[0033] Figure 6 For comparison, see the surface scanning electron microscope image of the membrane;

[0034] Figure 7 This is a graph showing the long-term stability of membrane 1. Detailed Implementation

[0035] To further understand the purpose, content, and advantages of this invention, specific embodiments of the invention are described in detail below. However, these embodiments are not limited to the examples described below and should be freely combined according to actual circumstances. The endpoints and values ​​of the ranges disclosed herein are not limited to the precise ranges and values. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] The following examples and comparative examples use the following methods to test the separation performance of the membranes:

[0037] The prepared membrane material was applied to pervaporation alcohol-water separation and pervaporation salt-water separation. The feed solution contained 90 wt% alcohol and was at 80°C. The permeation flux and separation factor of the ionic covalent organic framework membrane were measured. The feed solution contained 3.5 wt% sodium chloride and was at 80°C. The permeation flux and rejection rate of the ionic covalent organic framework membrane were measured. It should be noted that this testing method is only for facilitating parallel comparisons of membrane material performance and does not imply that the membrane material provided by this invention can only perform pervaporation alcohol-water separation or pervaporation salt-water separation under the above conditions. The membrane material provided by this invention can perform pervaporation separation of alcohol-water and salt-water of any concentration required for separation in the art, for example, alcohol concentration of 80-95 wt% and salt concentration of 0.1-7.5 wt%.

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

[0039] Amine monomers and aldehyde monomers were dissolved in water and organic solvents, respectively, to obtain aqueous solutions and oil solutions.

[0040] A carboxylated porous support membrane was fixed on the device, and an aqueous solution and an oil solution were added to both sides of the device, respectively. After sealing, the device was allowed to stand for reaction.

[0041] The membrane was removed and washed to remove any remaining unreacted monomers, yielding an ionic covalent organic framework membrane.

[0042] In a preferred embodiment, 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 pyromellitic methyl methoxymethyl aldehyde or trialdehyde pyrogallol, with a concentration of 0.5-10 mmol / L; and the reaction time is 12-168 h. The carboxylated porous support membrane refers to a modified porous support membrane with uniformly modified carboxyl groups on its surface. This facilitates the confined growth of the covalent organic framework on the membrane surface, forming a continuous, defect-free membrane layer. The covalent bonding mode maintains the stability of the membrane structure, enabling it to resist adverse evolution in a liquid environment. By controlling the concentrations of the amine and aldehyde monomers, as well as the reaction time, the membrane structure and separation performance can be optimized. Through this preferred embodiment, the membrane material can achieve good separation results when used for pervaporation alcohol-water separation or pervaporation salt-water separation. When used for pervaporation butanol-water separation, the permeate flux is consistently above 9000 g / m³. -2 h -1 The separation factor is above 175.

[0043] As a further preferred embodiment, the concentration of aldehyde monomers is controlled at 1-10 mmol / L, the reaction time is 48-96 h, and the permeate flux of the membrane material used for pervaporation butanol-water separation is consistently above 9000 g / m³. -2 h -1 The separation factor is above 1200.

[0044] In a further preferred embodiment, the concentration of aldehyde monomers is controlled at 3-10 mmol / L, the concentration of amine monomers at 5-20 mmol / L, the reaction time at 72-96 h, and the permeate flux of the membrane material used for pervaporation butanol-water separation can approach 10000 g m -2 h -1 Even higher. In some specific cases, the permeation flux can even reach 12000 g m³. -2 h -1 The separation factor can reach over 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 detailed description is provided in conjunction with some specific embodiments and comparative examples:

[0046] Example 1

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

[0048] 1) The polyacrylonitrile ultrafiltration membrane was heat-treated in a 1.5 mol / L sodium hydroxide solution at 55 °C for 1.0 h, and then treated with a morpholine ethanesulfonic acid solution containing hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide for 4 h. The membrane was repeatedly washed with deionized water and the water stains on the membrane surface were dried by rolling with a rubber roller to obtain a carboxylated polyacrylonitrile ultrafiltration membrane.

[0049] 2) Prepare an octanoic acid solution (oil phase solution) of 5.0 mmol / L trialdehyde phloroglucinol and an aqueous solution (aqueous phase solution) of 10 mmol / L 2,5-diaminobenzenesulfonic acid. Fix the carboxylated polyacrylonitrile ultrafiltration membrane on the device. Add the aqueous phase solution and the oil phase solution to both sides of the device, respectively. After sealing, allow the reaction to stand at room temperature for 72 h. Remove the membrane and wash it with methanol and deionized water to remove the residual unreacted monomers to obtain an ionic covalent organic framework membrane, denoted as membrane 1.

[0050] Membrane 1 was applied to pervaporation butanol-water separation, with a pervaporation flux of 12620 g / m³. -2 h -1 The separation factor was 3161; when membrane 1 was applied to the pervaporation separation of isopropanol and water, the permeate flux was 10432 g m³. -2 h-1 The separation factor was 1529; when membrane 1 was applied to the pervaporation of isobutanol-water separation, the permeate flux was 10601 g m³. -2 h -1 The separation factor was 1629; membrane 1 was applied to pervaporation salt-water separation, with a permeate flux of 75 kg m³. -2 h -1 The retention rate was 99.94%. Figure 1 The images show scanning electron microscope (SEM) images of the surface and cross-section of membrane 1.

[0051] Example 2

[0052] The difference between this embodiment and Example 1 is that the reaction time in step 2) is adjusted to 12 hours, while the remaining steps are the same as in Example 1, resulting in an ionic covalent organic framework membrane, denoted as membrane 2.

[0053] Membrane 2 was applied to pervaporation butanol-water separation, with a permeation flux of 13152 g / m³. -2 h -1 The separation factor is 175. Figure 2 The images show scanning electron microscope (SEM) images of the surface and cross-section of membrane 2.

[0054] Example 3

[0055] The difference between this embodiment and Example 1 is that the reaction time in step 2) is adjusted to 24 hours, while the remaining steps are the same as in Example 1, resulting in an ionic covalent organic framework membrane, denoted as membrane 3.

[0056] Membrane 3 was applied to pervaporation butanol-water separation, with a permeation flux of 11316 g / m³. -2 h -1 The separation factor is 559. Figure 3 The images show scanning electron microscope (SEM) images of the surface and cross-section of membrane 3.

[0057] Example 4

[0058] The difference between this embodiment and Example 1 is that the reaction time in step 2) is adjusted to 48 hours, while the remaining steps are the same as in Example 1, resulting in an ionic covalent organic framework membrane, denoted as membrane 4.

[0059] Membrane 4 was applied to pervaporation butanol-water separation, with a permeation flux of 9981 g / m³. -2 h -1 The separation factor is 1304. Figure 4 The images show scanning electron microscope (SEM) images of the surface and cross-section of membrane 4.

[0060] Example 5

[0061] The difference between this embodiment and Example 1 is that the reaction time in step 2) is adjusted to 96 hours, while the remaining steps are the same as in Example 1, resulting in an ionic covalent organic framework membrane, denoted as membrane 5.

[0062] Membrane 5 was applied to pervaporation butanol-water separation, with a permeation flux of 10641 g / m³. -2 h -1 The separation factor is 2430. Figure 5 The images show scanning electron microscope (SEM) images of the surface and cross-section of membrane 5.

[0063] Table 1

[0064]

[0065] Reaction time affects the formation and crystallization processes of ionic covalent organic framework membranes, thus influencing their separation performance. Imine-based covalent organic frameworks conform to a dynamic imine exchange mechanism; in the initial stages of the reaction, organic monomers polymerize rapidly, typically forming amorphous structures. As reaction time increases, the dynamic process of imine bond breaking and rearrangement gradually repairs defects, resulting in a more ordered and stable crystalline structure. The orderly arrangement of ionic groups within the highly crystalline pore walls forms rapid and selective transport channels for water molecules, facilitating rapid and selective water permeation. Simultaneously, with increasing reaction time, the ionic covalent organic framework membrane layer gradually grows, covering the surface of the porous supporting substrate. However, excessively long reaction times reduce the membrane's permeation flux and separation factor. Therefore, optimizing the reaction time can optimize the membrane structure, thereby achieving high separation performance.

[0066] Example 6

[0067] The difference between this embodiment and Example 1 is that the concentration of trialdehyde phloroglucinol in step 2) is adjusted to 10 mmol / L and the concentration of 2,5-diaminobenzenesulfonic acid is adjusted to 1.0 mmol / L. The remaining steps are the same as in Example 1, and the ionic covalent organic framework membrane of this embodiment is obtained, which is denoted as membrane 6.

[0068] Membrane 6 was applied to pervaporation butanol-water separation, with a permeation flux of 9256 g / m³. -2 h -1 The separation factor is 1255.

[0069] Example 7

[0070] The difference between this embodiment and Example 1 is that the concentration of trialdehyde phloroglucinol in step 2) is adjusted to 10 mmol / L and the concentration of 2,5-diaminobenzenesulfonic acid is adjusted to 5.0 mmol / L. The remaining steps are the same as in Example 1, and the ionic covalent organic framework membrane of this embodiment is obtained, which is referred to as membrane 7.

[0071] Membrane 7 was applied to pervaporation butanol-water separation, with a permeation flux of 10789 g / m³. -2 h -1 The separation factor is 1697.

[0072] Example 8

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

[0074] Membrane 8 was applied to pervaporation butanol-water separation, with a permeation flux of 9719 g / m³. -2 h -1 The separation factor is 2682.

[0075] Example 9

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

[0077] Membrane 9 was applied to pervaporation butanol-water separation, with a permeation flux of 10133 g / m³. -2 h -1 The separation factor is 2909.

[0078] Example 10

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

[0080] Membrane 10 was applied to pervaporation butanol-water separation, with a permeation flux of 11245 g / m³. -2 h -1 The separation factor is 821.

[0081] Example 11

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

[0083] Membrane 11 was applied to pervaporation butanol-water separation, with a permeation flux of 9428 g / m³.-2 h -1 The separation factor is 1232.

[0084] Example 12

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

[0086] Membrane 12 was applied to pervaporation butanol-water separation, with a permeation flux of 12339 g / m³. -2 h -1 The separation factor is 1796.

[0087] Example 13

[0088] The difference between this embodiment and Example 1 is that the trialdehyde phloroglucinol in step 2) of Example 1 is replaced with pyromellitic pyrrolizaldehyde, and the remaining steps are the same as in Example 1, so as to obtain the ionic covalent organic framework membrane of this embodiment, which is referred to as membrane 13.

[0089] Membrane 13 was applied to pervaporation butanol-water separation, with a permeation flux of 9662 g / m³. -2 h -1 The separation factor is 1267.

[0090] Example 14

[0091] The difference between this embodiment and Example 1 is that 2,5-diaminobenzenesulfonic acid in step 2) of Example 1 is replaced with 2,5-diaminobenzene-1,4-disulfonic acid. The remaining steps are the same as in Example 1, and the ionic covalent organic framework membrane of this embodiment is obtained, which is denoted as membrane 14.

[0092] Membrane 14 was applied to pervaporation butanol-water separation, with a permeation flux of 9175 g / m³. -2 h -1 The separation factor is 2065.

[0093] Table 2

[0094]

[0095]

[0096] Adjusting the concentration of organic monomers affects the separation performance of ionic covalent organic framework membranes. With increasing amine monomer concentration, the membrane permeation flux decreases and then stabilizes, while the separation factor gradually increases. With increasing aldehyde monomer concentration, the membrane permeation flux remains relatively stable, while the separation factor initially increases and then changes little. This indicates that increasing the organic monomer concentration helps form a complete membrane layer on the porous support substrate surface. Furthermore, the orderly arrangement of hydrophilic ionic groups within the highly crystalline pore walls enhances the selective transport of water molecules, achieving high permeability and high selectivity. Moreover, changing the type of organic monomer can also produce continuous and complete ionic covalent organic framework membranes exhibiting good separation performance, demonstrating the general applicability of this method.

[0097] Comparative Example 1

[0098] The difference between this comparative example and Example 1 is that step 1) is adjusted so that the treatment with morpholine ethanesulfonic acid solution of hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is no longer performed. The remaining steps are the same as in Example 1. The resulting ionic covalent organic framework membrane is referred to as control membrane 1.

[0099] Comparative membrane 1 was applied to pervaporation butanol-water separation, with a permeation flux of 3067 g / m³. -2 h -1 The separation factor is 1115. Figure 6 For comparison, see the surface scanning electron microscope image of film 1.

[0100] Table 3

[0101]

[0102] The surface of the ionic covalent organic framework membrane formed on the uncarboxylated porous support substrate membrane is rough. Figure 6 The interfacial interaction between the membrane layer and the support layer is weak, resulting in unsatisfactory separation performance, especially low permeation flux. This is due to the amorphous structure caused by disordered growth, leading to the loss of interconnected pore channels. In contrast, carboxylation-modified porous support membranes form a uniform and continuous ionic covalent organic framework membrane layer with higher permeation flux and separation factor. This is because functionalization of the porous support membrane facilitates the confined anchoring of organic monomers on the membrane surface, inducing the confined growth of the covalent organic framework on the porous support membrane surface.

[0103] In summary, this invention provides a method for preparing ionic covalent organic framework membranes. Functionalization of the porous support substrate surface facilitates the confined growth of ionic covalent organic frameworks on its surface. The preparation method of this invention is simple and controllable. The prepared ionic covalent organic framework membrane can be applied to pervaporation alcohol-water separation and pervaporation salt-water separation, exhibiting good long-term separation stability in the pervaporation alcohol-water separation process, and has broad prospects for industrial application. This provides significant guidance for the preparation of porous framework membranes.

[0104] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many modifications under the guidance of the present invention without departing from the spirit of the present invention, and these modifications are all within the scope of protection of the present invention.

[0105] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

Claims

1. A method for preparing an ionic covalent organic framework membrane, characterized in that: Includes the following steps, Amine monomers and aldehyde monomers are dissolved in water and organic solvents, respectively, to obtain aqueous solutions and oil solutions; the amine monomers are 2,5-diaminobenzenesulfonic acid or 2,5-diaminobenzene-1,4-disulfonic acid, with a concentration of 1-20 mmol / L; the aldehyde monomers are pyromellitic methyl ester or trialdehyde-resorcinol, with a concentration of 0.5-10 mmol / L. The carboxylated porous support membrane was fixed on the device, and aqueous solution and oil solution were added to both sides of the device respectively. After sealing, the reaction was allowed to stand for 12-168 h. The membrane was removed and washed to remove any remaining unreacted monomers, yielding an ionic covalent organic framework membrane. The porous support base membrane is a carboxylated polyacrylonitrile ultrafiltration membrane. The preparation method of the carboxylated polyacrylonitrile ultrafiltration membrane includes the following steps: first, heat-treat the porous support base membrane with a sodium hydroxide or potassium hydroxide aqueous solution with a concentration of 1.0-3.0 mol / L at 40-80 ℃ for 1.0-3.0 h, and then treat it with a morpholine ethanesulfonic acid buffer solution containing hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide.

2. 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 h.

3. 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 h.

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

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

6. An ionic covalent organic framework membrane prepared by any one of the preparation methods described in claims 1-5.

7. The application of the ionic covalent organic framework membrane according to claim 6, characterized in that: Used for pervaporation alcohol-water separation or pervaporation salt-water separation.

8. The application of the ionic covalent organic framework membrane according to claim 7, characterized in that: The alcohol is any one of ethanol, isopropanol, isobutanol, and butanol, with an alcohol concentration of 80-95 wt%; the salt is sodium chloride, with a salt concentration of 0.1-7.5 wt%.

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