Supramolecular responsive channel anion exchange membrane and preparation method and application thereof

Abstract

The application belongs to the technical field of electrodialysis, and particularly relates to a supramolecular responsive channel anion exchange membrane and a preparation method and application thereof. The preparation method comprises the following steps: taking biphenyl, diphenyl-18-crown-6, N-methyl-4-piperidone and tetraphenylporphyrin, and dissolving the above substances in dichloromethane; under ice bath conditions, a constant speed of trifluoroacetic acid is added to the above mixture, and then trifluoromethanesulfonic acid is added, and the reaction lasts for 3-5 hours; the obtained green viscous mixture is eluted into deionized water to obtain a solid; 0.5-1g of the above solid is dissolved in 10-15mL of a casting membrane solvent to obtain a green transparent solution; the above transparent solution is poured on a glass plate and dried in a vacuum drying box to obtain an anion exchange membrane. The anion exchange membrane prepared by the application has small resistance, visual pH response and good desalination performance, and can be used in the technical field of electrodialysis desalination membrane materials.

Description

Technical Field

[0001] This invention belongs to the field of electrodialysis technology, specifically relating to a supramolecular responsive channel anion exchange membrane, its preparation method, and its application. Background Technology

[0002] In the development of anion exchange membrane materials, while traditional membrane materials have been applied in various fields, several shortcomings have gradually become apparent. Typically, these membranes rely on classic ion exchange groups such as quaternary ammonium salts and tertiary amine groups. However, this design faces numerous challenges in practical application.

[0003] First, quaternary ammonium salt anion exchange membranes are prone to Hoffmann degradation in alkaline environments, leading to reduced chemical stability and material deactivation, thus weakening their reliability and lifespan under strongly alkaline conditions. Although tertiary amine ion exchange membranes improve alkali resistance by introducing tertiary amine groups, the resulting conductivity issues limit their widespread application. Furthermore, due to their relatively simple structure, traditional membranes lack adaptability to complex ionic environments, resulting in poor ion selectivity, especially with a significant decrease in membrane efficiency when multiple component ions coexist.

[0004] Secondly, due to the limitations of the ion channel design within traditional anion exchange membranes, their ion permeability is poor, affecting processing speed and efficiency. This problem is particularly pronounced in applications requiring rapid processing and large-scale industrial applications, becoming a bottleneck restricting their application. The lack of flexibility and adaptability in traditional membrane structures leads to low ion transport efficiency and increased resistance in practical applications. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a supramolecular responsive anion exchange membrane, its preparation method, and its applications. The anion exchange membrane prepared by this invention exhibits low resistance, visible pH response, and excellent desalination performance, making it suitable for use in the field of electrodialysis desalination membrane materials.

[0006] To achieve the above technical objectives, the technical solution adopted in the embodiments of the present invention is as follows:

[0007] In a first aspect, embodiments of the present invention provide a method for preparing a supramolecular responsive channel anion exchange membrane, comprising the following steps:

[0008] (1) Take 3-5g of biphenyl, 0.5-1g of dibenzo-18-crown-6, 4-5mL of N-methyl-4-piperidinone and 0.01-0.2g of tetraphenylporphyrin, and dissolve the above substances in 5-20mL of dichloromethane;

[0009] (2) Under ice bath conditions, add 1-3 mL of trifluoroacetic acid dropwise to the mixed solution in step (1) at a constant rate, and then add 10-33 mL of trifluoromethanesulfonic acid. The reaction lasts for 3-5 hours.

[0010] (3) The green viscous mixture was poured into deionized water and eluted to obtain a solid;

[0011] (4) Take 0.5-1g of the solid from step (3) and dissolve it in 10-15mL of casting solvent to obtain a green transparent solution;

[0012] (5) Pour the above transparent solution onto a glass plate and place it in a vacuum drying oven. Dry it at 60-80°C for 10-24 hours to obtain an anion exchange membrane.

[0013] Further, in step (4), the casting solvent is one or more of dimethyl sulfoxide, N,N-dimethylacetamide and N,N-dimethylformamide.

[0014] Furthermore, in step (5), the thickness of the anion exchange membrane is controlled at 80–110 μm.

[0015] Furthermore, in step (3), when eluting with deionized water, elute 3 to 5 times to ensure that the residual solvent is completely washed away.

[0016] Furthermore, the anion exchange membrane is soaked in an acidic aqueous solution before use.

[0017] Secondly, embodiments of the present invention provide an anion exchange membrane with supramolecular responsive channels, which is prepared using the preparation method described in the first aspect.

[0018] Thirdly, embodiments of the present invention provide the application of the supramolecular responsive channel anion exchange membrane described in the second aspect as a membrane material for electrodialysis desalination.

[0019] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows:

[0020] 1) Enhanced chemical stability: The present invention adopts a porphyrin structure, which makes the membrane exhibit color changes under different acid and alkaline conditions, providing intuitive pH response capability. This visualization feature helps to monitor the usage status, while also improving the chemical stability of the membrane and extending its service life, making it more reliable than traditional membranes.

[0021] 2) Lower resistance: The optimized supramolecular structure design enables the novel anion exchange membrane to effectively reduce the membrane resistance, especially with the synergistic effect of the tertiary amine structure, which significantly improves the conductivity, which is crucial for efficient desalination processes.

[0022] 3) Easy to industrialize: The preparation process of the supramolecular responsive channel anion exchange membrane of the present invention is simple and does not require quaternization. The synthesis steps are simple and easy to industrialize. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] Example 1

[0025] A method for preparing a supramolecularly responsive channel anion exchange membrane includes the following steps:

[0026] (1) Take 4.2g of biphenyl, 0.9g of dibenzo-18-crown-6, 4.1mL of N-methyl-4-piperidinone and 0.02g of tetraphenylporphyrin, and dissolve the above substances in 10mL of dichloromethane;

[0027] (2) Under ice bath conditions, add 2 mL of trifluoroacetic acid to the mixture in step (1) at a constant rate, then add 25 mL of trifluoromethanesulfonic acid and let the reaction continue for 4 hours.

[0028] (3) Pour the green viscous mixture obtained in step (2) into deionized water and wash it to obtain a colored solid (the green color will become darker as the amount of tetraphenylporphyrin increases);

[0029] (4) Dissolve 0.75g of the solid polymer obtained in step (3) in 15mL of dimethyl sulfoxide to obtain a green transparent solution;

[0030] (5) Pour the above green transparent solution onto a glass plate and place it in a vacuum drying oven. Dry it at 80°C for 24 hours to obtain a weakly basic anion exchange membrane AEM-1.

[0031] Example 2

[0032] A method for preparing a supramolecularly responsive channel anion exchange membrane includes the following steps:

[0033] (1) Take 4.2g of biphenyl, 0.9g of dibenzo-18-crown-6, 4.1mL of N-methyl-4-piperidinone and 0.04g of tetraphenylporphyrin, and dissolve the above substances in 10mL of dichloromethane;

[0034] (2) Under ice bath conditions, add 2 mL of trifluoroacetic acid to the mixture in step (1) at a constant rate, then add 25 mL of trifluoromethanesulfonic acid and let the reaction continue for 4 hours.

[0035] (3) Pour the green viscous mixture obtained in step (2) into deionized water and wash it to obtain a colored solid (the green color will become darker as the amount of tetraphenylporphyrin increases);

[0036] (4) Dissolve 0.75g of the solid polymer obtained in step (3) in 15mL of dimethyl sulfoxide to obtain a green transparent solution;

[0037] (5) Pour the above green transparent solution onto a glass plate and place it in a vacuum drying oven. Dry it at 80°C for 24 hours to obtain a weakly basic anion exchange membrane AEM-2.

[0038] Example 3

[0039] A method for preparing a supramolecularly responsive channel anion exchange membrane includes the following steps:

[0040] (1) Take 4.2g of biphenyl, 0.9g of dibenzo-18-crown-6, 4.1mL of N-methyl-4-piperidinone and 0.1g of tetraphenylporphyrin, and dissolve the above substances in 10mL of dichloromethane;

[0041] (2) Under ice bath conditions, add 2 mL of trifluoroacetic acid to the mixture in step (1) at a constant rate, then add 25 mL of trifluoromethanesulfonic acid and let the reaction continue for 4 hours.

[0042] (3) Pour the green viscous mixture obtained in step (2) into deionized water and wash it to obtain a colored solid (the green color will become darker as the amount of tetraphenylporphyrin increases);

[0043] (4) Dissolve 0.75g of the solid polymer obtained in step (3) in 15mL of dimethyl sulfoxide to obtain a green transparent solution;

[0044] (5) Pour the above green transparent solution onto a glass plate and place it in a vacuum drying oven. Dry it at 80°C for 24 hours to obtain a weakly basic anion exchange membrane AEM-3.

[0045] The performance of the anion exchange membranes prepared in Examples 1-3 was tested below:

[0046] Test 1: The resistance of the anion exchange membranes prepared in Examples 1-3 was tested and compared with commercial quaternary ammonium type AMX and tertiary amine type ACM anion exchange membranes.

[0047] Table 1. Comparison of membrane surface resistance between the anion exchange membranes prepared in Examples 1-3 and commercial membranes with different functional groups.

[0048]

[0049] Table 1 shows that the tertiary amine anion exchange membranes prepared in Examples 1-3 exhibit lower resistance under direct testing conditions due to their unique structure, which is particularly significant compared to the traditional tertiary amine anion exchange membrane ACM. After activation with acidic solution, the surface resistance of the tertiary amine anion exchange membranes prepared in Examples 1-3 is comparable to that of the commercial quaternary ammonium type AMX membrane. This indicates that the tertiary amine anion exchange membrane can respond efficiently to pH changes and significantly reduce energy consumption.

[0050] Test 2: The chemical stability of the anion exchange membranes prepared in Examples 1-3 in sodium hydroxide solution was tested to investigate their chemical stability. The weight loss rate was used as an indicator, and the weight difference was used as an indicator to evaluate their chemical stability. The results are shown in Table 2.

[0051] The following steps are included when conducting a weightlessness rate test:

[0052] (1) The weakly basic anion exchange membranes prepared in Examples 1-3 and the commercial membrane quaternary ammonium type AMX were completely dried in a vacuum oven at 80°C for 24 hours, and the weight of the samples was recorded.

[0053] (2) Soak the dried ion exchange membrane sample in 2.0M sodium hydroxide solution at 80℃ for 24h, 48h and 96h, then carefully wipe the residual solution on the sample surface and wash the soaked membrane with water until the water becomes neutral.

[0054] (3) The ion exchange membrane sample was dried under vacuum at 80℃ for 24h, and then the membrane weight was re-weighed. The weight loss was used to characterize the alkali resistance stability of the membrane.

[0055] Table 2. Weight loss rate of the membrane after immersion in 2.0 mol / L sodium hydroxide solution at different time periods.

[0056] AMX weight loss rate (%) 10.2 15.2 19.3 AEM-1 weight loss rate (%) 1.2 1.5 1.6 AEM-2 weight loss rate (%) 1.3 1.5 1.6 AEM-3 weight loss rate (%) 1.1 1.2 1.3

[0057] As shown in Table 2, traditional quaternary ammonium anion exchange membranes (AMX) often experience a certain degree of weight loss due to Hoffmann degradation. However, the tertiary amine anion exchange membranes prepared in Examples 1-3 exhibit a lower weight loss rate due to their unique stable structure and the characteristics of tertiary amine functional groups, further highlighting their superior chemical stability.

[0058] Test 3: The water absorption rate of the anion exchange membranes prepared in Examples 1-3 and the commercial quaternary ammonium type AMX membranes was compared at different temperatures. The specific operation was as follows: The membrane samples were completely dried in a vacuum drying oven at 80℃ for 24h, and the length of the membrane samples was recorded. Then, the dried ion exchange membrane samples were immersed at 20℃, 30℃, and 40℃ for 48h, respectively, and the residual solution on the sample surface was carefully wiped off. The weight of the membrane samples was recorded, and the weight change of the samples compared to the dry state was calculated.

[0059] Table 3. Water absorption rates of the anion exchange membranes and AMX membranes prepared in Examples 1-3 at different temperatures.

[0060] AMX 20.21 25.88 31.79 AEM-1 10.05 12.58 14.38 AEM-2 12.15 13.78 15.13 AEM-3 15.87 16.23 17.33

[0061] As shown in Table 3, the anion exchange membranes prepared in Examples 1-3, due to their rigid polymer framework, exhibited a much less pronounced trend in water absorption rate with increasing temperature compared to the AMX membranes with flexible polymer chain structures. This indicates that the anion exchange membranes prepared in Examples 1-3 possess good thermal stability and are not easily deformed by heat, thus demonstrating excellent structural stability at high temperatures.

[0062] This invention introduces porphyrin and crown ether supramolecular structures to provide an anion exchange membrane with supramolecular responsive channels. The porphyrin structure endows the membrane with pH-responsive properties, causing it to exhibit different colors under different acid and alkaline conditions. This visualization feature not only improves the membrane's state monitoring capabilities but also provides users with intuitive operational guidance. The supramolecular channels formed by the crown ether structure effectively increase the membrane's ion cross-chain transport capacity, enhance ion permeability, and significantly reduce resistance, especially when combined with tertiary amine structures, exhibiting even more pronounced advantages.

[0063] By integrating these innovative supramolecular designs, this invention produces an anion exchange membrane that surpasses traditional membranes in all aspects of performance. It not only possesses higher chemical stability and ion selectivity but also demonstrates superior performance in terms of permeability and resistance optimization. Such progress fully demonstrates the enormous potential of supramolecular chemistry in membrane materials science, providing a solid foundation and broad prospects for future technological development and practical applications.

[0064] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a supramolecularly responsive channel anion exchange membrane, characterized in that, Includes the following steps: (1) Take 3~5g of biphenyl, 0.5~1g of dibenzo-18-crown-6, 4~5mL of N-methyl-4-piperidinone and 0.01~0.2g of tetraphenylporphyrin, dissolve the above substances in 5~20mL of dichloromethane to obtain a mixed solution; (2) Under ice bath conditions, add 1~3 mL of trifluoroacetic acid to the mixed solution in step (1) at a constant rate, then add 10~33 mL of trifluoromethanesulfonic acid. The reaction continues for 3~5 hours to obtain a green viscous mixture. (3) The green viscous mixture was poured into deionized water and eluted to obtain a solid; (4) Take 0.5~1g of the solid from step (3) and dissolve it in 10~15mL of casting solvent to obtain a green transparent solution; (5) Pour the above transparent solution onto a glass plate and place it in a vacuum drying oven. Dry it at 60~80℃ for 10~24h to obtain a weakly basic anion exchange membrane. The weakly basic anion exchange membrane has pH response characteristics and exhibits different colors under different acid and alkaline conditions. The thickness of the weakly basic anion exchange membrane is controlled at 80~110μm. Before use, the weakly basic anion exchange membrane is soaked in an acidic aqueous solution. The weakly basic anion exchange membrane is used as a membrane material for electrodialysis desalination.

2. The method for preparing a supramolecularly responsive channel anion exchange membrane according to claim 1, characterized in that, In step (4), the casting solvent is one or more of dimethyl sulfoxide, N,N-dimethylacetamide and N,N-dimethylformamide.

3. The method for preparing a supramolecularly responsive channel anion exchange membrane according to claim 1, characterized in that, In step (3), when eluting with deionized water, elute 3 to 5 times to ensure that the residual solvent is washed away.

4. An anion exchange membrane with supramolecular responsive channels, prepared by the preparation method according to any one of claims 1-3.

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