Quaternized covalent triazine regular pore channel anion exchange membrane and preparation method thereof

Abstract

The invention discloses a quaternized covalent triazine regular pore channel anion exchange membrane and a preparation method thereof, and belongs to the technical field of high polymer materials, and the preparation method comprises the following steps: preparing quaternized aromatic nitrile; preparing a quaternized covalent triazine skeleton anion exchange membrane; the anion exchange membrane prepared by the method has a rigid covalent triazine framework, so that the membrane has good mechanical properties, and permanent pore channels on the triazine framework can reduce the ion transmission resistance and increase the ion transmission performance; the triazine framework membrane has a framework structure connected with a longer length, so that the pore channel of the triazine framework membrane is larger, and the ion transmission performance is enhanced; the polymer is connected with a cation exchange group through a carbon-carbon bond, and the alkali stability of the carbon-carbon bond is better, so that the damage of a polymer framework caused by attack of OH <-> to an ether bond is avoided, and the stability of an ion channel and the mechanical property of the membrane are facilitated; and a plurality of cation groups are introduced into the aromatic nitrile, so that the anion exchange membrane with the regular pore channel structure, which is more excellent in ion transmission performance, is prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a quaternized covalent triazine regular pore anion exchange membrane and a preparation method thereof. Background Art

[0002] Anion exchange membranes (AEMs) are widely used in various electrochemical energy technologies, such as fuel cells, water electrolyzers, electrochemical CO2 reduction, etc. In particular, alkaline anion exchange membrane fuel cells (AEMFCs) have the advantages of not relying on precious metal electrocatalysts, no electrolyte leakage, and being environmentally friendly. As a key component of AEMFCs, AEMs need to have high conductivity and good alkaline stability.

[0003] When designing anion exchange membranes, a balance needs to be found between ion exchange capacity (IEC) and dimensional stability. An increase in IEC generally increases the carrier concentration, thereby increasing the ion conductivity of the membrane. However, high IEC may lead to excessive water absorption, making the membrane soft and prone to swelling, reducing mechanical properties. An ideal anion exchange membrane should have a strong backbone structure with strong intermolecular interactions to ensure good dimensional stability and be decorated with abundant ionic groups on the ordered channels to achieve rapid transport of anions. Ionic covalent organic framework (COF) membranes show great potential as anion exchange membranes due to their permanently ordered channels and precise arrangement of ions. The microporous structure provides channels, reduces the ion transport resistance, and allows rapid ion transport within the membrane. Therefore, even AEMs with lower IEC still have high ion transport properties.

[0004] A method for preparing a covalent triazine framework membrane was reported in the journal Nature, Vol. 6117, p. 299. The method involves connecting cationic groups to aromatic nitrile via ether bonds, polymerizing with strong acid catalysis, and casting into a membrane. The polymer skeleton for preparing the triazine framework membrane contains aromatic ether bonds, which are easily affected by OH - The membrane is attacked and broken, resulting in changes in the polymer skeleton, which makes the chemical stability of the membrane worse in high temperature and high alkaline environments. Summary of the invention

[0005] In view of the shortcomings of the existing anion exchange membrane preparation, the present invention provides a quaternized covalent triazine regular pore anion exchange membrane and a preparation method thereof. The anion exchange membrane prepared by the method has a rigid covalent triazine skeleton, which can make the membrane have good mechanical properties. The permanent pores on the triazine skeleton can reduce the ion transmission resistance and increase the ion transmission performance. The skeleton structure with a longer connection makes the pores of the triazine skeleton membrane larger, thereby enhancing the ion transmission performance. The polymer and the cation exchange group are connected by a carbon-carbon bond, and the alkali stability of the carbon-carbon bond is better, thereby avoiding the OH-induced -The destruction of the polymer framework caused by the attack on the ether bonds is beneficial to the stability of the ion channel and the mechanical properties of the membrane; and multiple cationic groups are introduced on the aromatic nitrile to prepare an anion exchange membrane with a regular pore structure and better ion transport performance.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing a quaternized covalent triazine regular pore anion exchange membrane comprises the following steps:

[0008] Step 1: Preparation of quaternized aromatic nitrile;

[0009] Dissolve bromomethyl aromatic nitrile in a solvent, stir to dissolve, then drop a quaternizing agent into the mixed solution, heat to 70-90°C, and stir for 4-6 hours; after the reaction is completed, precipitate the mixed solution in ethyl acetate; finally filter and wash with deionized water to obtain a precipitate, and vacuum dry at 60-80°C for 8-12 hours to obtain a quaternized aromatic nitrile;

[0010] Step 2: Preparation of quaternized covalent triazine skeleton anion exchange membrane;

[0011] The quaternized aromatic nitrile obtained in step 1 is mixed with aromatic nitrile, trifluoromethanesulfonic acid is added dropwise to the mixed solution under ice-salt bath conditions, and stirred to obtain a casting solution, the casting solution is poured on a glass plate, baked at 50-60° C. for 2 hours, and then dried at 100-120° C. to obtain a membrane; after the membrane is cooled to room temperature, the obtained membrane is immersed in a 0.1M NaOH aqueous solution to remove the adsorbed trifluoromethanesulfonic acid, and then the membrane is immersed in a 1M NaOH aqueous solution for 24 hours to obtain an OH-type anion exchange membrane.

[0012] Furthermore, in step 1, A is 2,6-dibromomethyl-4,4'-dicarbonitrile biphenyl, 3,5"-dibromomethyl-[1,1':4',1"-triphenyl]-4,4"-dinitrile or 2,6,2",6"-tetrabromomethyl-[1,1':4',1"-triphenyl]-4,4"-dinitrile.

[0013] Furthermore, in step 1, the solvent is N,N-dimethylacetamide (DMAc).

[0014] Furthermore, in step 1, the quaternizing agent is trimethylamine aqueous solution, piperidine, 3,6,9-triaza-spiro[5,5]undecane, or 1,2-dimethylimidazole.

[0015] Furthermore, in step 1, the molar ratio of the mixed solution to the quaternary ammonium agent is 1:2.5-3.0.

[0017] Furthermore, in step 2, the substance B is 4,4'-biphenylcarbonitrile, [1,1':4',1"-terphenyl]-4,4"-dicarbonitrile or [1,1':4',1"-terphenyl]-4,4"-dicarbonitrile.

[0018] Furthermore, in step 2, the molar ratio of the quaternized aromatic nitrile to the aromatic nitrile is any ratio.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] The invention discloses a quaternized covalent triazine regular pore anion exchange membrane and a preparation method thereof. The anion exchange membrane prepared by the method has a rigid covalent triazine skeleton, which can make the membrane have good mechanical properties. The permanent pores on the triazine skeleton can reduce the ion transmission resistance and increase the ion transmission performance. The skeleton structure is connected longer, so that the pores of the triazine skeleton membrane are larger, thereby enhancing the ion transmission performance. The polymer and the cation exchange group are connected by a carbon-carbon bond, and the alkali stability of the carbon-carbon bond is better, thereby avoiding the OH-induced - The destruction of the polymer framework caused by the attack on the ether bonds is beneficial to the stability of the ion channel and the mechanical properties of the membrane; and multiple cationic groups are introduced on the aromatic nitrile to prepare an anion exchange membrane with a regular pore structure and better ion transport performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0022] Figure 1 The conductivity curve of the trimethylamine anion exchange membrane A prepared in Example 1 is changed with temperature;

[0023] Figure 2 The conductivity curve of the trimethylamine anion exchange membrane B prepared in Example 2 is changed with temperature;

[0024] Figure 3 The conductivity curve of the imidazole anion exchange membrane C prepared in Example 3 is plotted against temperature. DETAILED DESCRIPTION

[0025] In order to clearly and completely describe the technical solution and its specific working process of the present invention, the specific implementation methods of the present invention are as follows in conjunction with the accompanying drawings of the specification:

[0026] Example 1

[0027] This embodiment provides a method for preparing a quaternized covalent triazine regular pore anion exchange membrane, which specifically comprises the following steps:

[0028] Step 1: Preparation of quaternized aromatic nitrile;

[0029] Weigh 2.4 g of 2,6-dibromomethyl-4,4'-dicarbonitrile biphenyl and place it in a 50 ml single-mouth bottle, add 10 ml of N,N-dimethylacetamide (DMAc) to the bottle, and stir to dissolve; add a quaternary ammonium reagent, i.e., a 30 wt.% trimethylamine aqueous solution (3.27 g), dropwise into the above solution and mix evenly, wherein the molar ratio of 2,6-dibromomethyl-4,4'-dicarbonitrile biphenyl to the quaternary ammonium reagent is 1:2.7; heat the reaction solution to 80 degrees Celsius and stir at this temperature for 6 hours; after the reaction is completed, precipitate the mixed solution in ethyl acetate; filter and wash the obtained precipitate with deionized water; vacuum dry at 60°C for 8 hours to obtain a quaternary ammonium aromatic nitrile a, the molecular formula of which is as follows:

[0030]

[0031] Among them, R is

[0032] The quaternizing agent used in this embodiment is trimethylamine solution;

[0033] Step 2: Preparation of quaternized covalent triazine skeleton anion exchange membrane;

[0034] Weigh 0.37g of 4,4'-biphenylcarbonitrile and 0.46g of quaternized aromatic nitrile a, mix and place in a 50ml flask. The molar ratio of 4,4'-biphenylcarbonitrile and quaternized aromatic nitrile a can be any ratio; slowly drop 10ml of trifluoromethanesulfonic acid into the flask under an ice-salt bath for about 8 minutes, and stir for 1.5h to obtain a casting solution, cast the casting solution on a 10cm×10cm glass plate, bake at 50℃ for 2 hours, and then dry at 100℃ to obtain a membrane. When the membrane is cooled to room temperature, immerse the obtained membrane in a 0.1M NaOH aqueous solution to remove the adsorbed trifluoromethanesulfonic acid, and then immerse the membrane in a 1M NaOH aqueous solution for 24 hours to obtain an OH-type anion exchange membrane;

[0035] The reaction equation is as follows:

[0036]

[0037] like Figure 1 As shown, the prepared anion exchange membrane has an ion conductivity of 93.2 mS / cm at 80° C., a water absorption rate of 23.5%, a swelling rate of 7.56%, a tensile strength of 38 MPa, and an elongation at break of 5.12%.

[0038] Example 2

[0039] This embodiment provides a method for preparing a quaternized covalent triazine regular pore anion exchange membrane, which specifically comprises the following steps:

[0040] Step 1: Preparation of quaternized aromatic nitrile;

[0041] Weigh 2.0 g of 3,5"-dibromomethyl-[1,1':4',1"-triphenyl]-4,4"-dinitrile into a 50 ml single-mouth bottle, add 10 ml of DMAc into the bottle, and stir to dissolve. Add the quaternary ammonium reagent, i.e., 30 wt.% trimethylamine aqueous solution (3.27 g), dropwise into the above solution, wherein the molar ratio of 3,5"-dibromomethyl-[1,1':4',1"-triphenyl]-4,4"-dinitrile to the quaternary ammonium reagent is 1:2.7; heat the reaction solution to 80 degrees Celsius and stir at this temperature for 6 hours; after the reaction is completed, precipitate the mixture in 30 ml of ethyl acetate. Filter and wash the obtained precipitate with deionized water; vacuum dry at 60°C for 8 hours to obtain quaternary aromatic nitrile b, the molecular formula is as follows:

[0042]

[0043] R is

[0044] The quaternizing agent used in this embodiment is trimethylamine solution;

[0045] Step 2: Preparation of quaternized covalent triazine skeleton anion exchange membrane;

[0046] Weigh 0.3 g of [1,1':4',1"-terphenyl]-4,4"-dicarbonitrile and 0.312 g of quaternized aromatic nitrile b) and mix them in a 50 ml flask, wherein the molar ratio of [1,1':4',1"-terphenyl]-4,4"-dicarbonitrile to quaternized aromatic nitrile b) can be any ratio; slowly drop 15 ml of trifluoromethanesulfonic acid into the flask under an ice-salt bath for 10 minutes; stir for 2 hours, the solution becomes obviously viscous, and a casting solution is obtained, which is cast on a 10 cm × 10 cm glass plate; bake at 50° C. for 2 hours, and then dry at 100° C. to obtain a membrane; after the membrane is cooled to room temperature, immerse the obtained membrane in a 0.1 M NaOH aqueous solution to remove adsorbed trifluoromethanesulfonic acid, and then immerse the membrane in a 1 M NaOH aqueous solution for 24 hours to obtain an OH-type anion exchange membrane.

[0047] The reaction equation is as follows:

[0048]

[0049] like Figure 2As shown, the prepared anion exchange membrane has an ion conductivity of 102.6 mS / cm at 80° C., a water absorption rate of 19.1%, a swelling rate of 6.33%, a tensile strength of 47 MPa, and an elongation at break of 4.91%.

[0050] Example 3

[0051] This embodiment provides a method for preparing a quaternized covalent triazine regular pore anion exchange membrane, which specifically comprises the following steps:

[0052] Step 1: Preparation of quaternized aromatic nitrile;

[0053] Weigh 2.0 g of 2,6,2",6"-tetrabromomethyl-[1,1':4',1"-triphenyl]-4,4"-dinitrile into a 50 ml single-mouth bottle, add 10 ml of DMAc into the bottle, and stir to dissolve; add quaternary ammonium reagent, i.e. 1,2-dimethylimidazole (1.47 g), dropwise into the above solution, wherein the molar ratio of 2,6,2",6"-tetrabromomethyl-[1,1':4',1"-triphenyl]-4,4"-dinitrile to the quaternary ammonium reagent is 1:5; heat the reaction solution to 80 degrees Celsius and stir at this temperature for 6 hours. After the reaction is completed, pour the mixed solution into ethyl acetate to obtain a yellow-brown precipitate; filter and wash the obtained precipitate with deionized water. Dry under vacuum at 60°C for 8 hours to obtain quaternary aromatic nitrile c, the molecular formula of which is as follows:

[0054]

[0055] R is

[0056] The quaternizing agent used in this embodiment is 1,2-dimethylimidazole;

[0057] Step 2: Preparation of quaternized covalent triazine skeleton anion exchange membrane;

[0058] Weigh 0.3g [1,1':4',1"-terphenyl]-4,4"-dicarbonitrile and 0.554g quaternized aromatic nitrile c and mix them in a 50ml flask. The molar ratio of [1,1':4',1"-terphenyl]-4,4"-dicarbonitrile and quaternized aromatic nitrile c can be any ratio. In an ice-salt bath, slowly drop 15ml trifluoromethanesulfonic acid into the flask for 10 minutes. Stir for 2 hours. When the solution is obviously viscous, cast the casting liquid on a 10cm×10cm glass plate, bake at 50℃ for 2 hours, and then dry at 100℃ to obtain a membrane. When the membrane is cooled to room temperature, immerse the obtained membrane in a 0.1M NaOH aqueous solution to remove the adsorbed trifluoromethanesulfonic acid, and then immerse the membrane in a 1M NaOH aqueous solution for 24 hours to obtain an OH-type anion exchange membrane.

[0059] The reaction equation is as follows:

[0060]

[0061] like Figure 3 As shown, the prepared anion exchange membrane has an ion conductivity of 109.6 mS / cm at 80° C., a water absorption rate of 24.6%, a swelling rate of 7.98%, a tensile strength of 45 MPa, and an elongation at break of 5.33%.

[0062] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0063] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0064] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a quaternized covalent triazine regular pore anion exchange membrane, characterized in that: The specific steps include: Step 1: Preparation of quaternized aromatic nitrile; Dissolve compound A in a solvent, stir to dissolve, then drop the quaternary ammonium reagent into the mixed solution, heat to 80°C, and stir for 6 hours; after the reaction is completed, precipitate the mixed solution in ethyl acetate; finally filter and wash with deionized water to obtain a precipitate, and vacuum dry at 60°C for 8 hours to obtain a quaternary ammonium aromatic nitrile; Step 2: Preparation of quaternized covalent triazine skeleton anion exchange membrane; The quaternized aromatic nitrile obtained in step 1 is mixed with compound B, trifluoromethanesulfonic acid is added dropwise to the mixed solution under ice-salt bath conditions, and stirred to obtain a casting solution, the casting solution is poured on a glass plate, dried at 50° C. for 2 hours, and then dried at 100° C. to obtain a film; After the membrane was cooled to room temperature, the obtained membrane was immersed in a 0.1 M NaOH aqueous solution to remove the adsorbed trifluoromethanesulfonic acid, and then the membrane was immersed in a 1 M NaOH aqueous solution for 24 hours to obtain an OH-type anion exchange membrane.

2. The method for preparing a quaternized covalent triazine regular pore anion exchange membrane according to claim 1, characterized in that: In step 1, the compound A is 2,6-dibromomethyl-4,4'-dicarbonitrile biphenyl, 3,5"-dibromomethyl-[1,1':4',1"-triphenyl]-4,4"-dinitrile or 2,6,2",6"-tetrabromomethyl-[1,1':4',1"-triphenyl]-4,4"-dinitrile.

3. The method for preparing a quaternized covalent triazine regular pore anion exchange membrane according to claim 1, characterized in that: In step 1, the solvent is N,N-dimethylacetamide.

4. The method for preparing a quaternized covalent triazine regular pore anion exchange membrane according to claim 1, characterized in that: In step 1, the quaternizing agent is trimethylamine aqueous solution, piperidine, 3,6,9-triaza-spiro[5,5]undecane, and 1,2-dimethylimidazole.

5. The method for preparing a quaternized covalent triazine regular pore anion exchange membrane according to claim 1, characterized in that: In step 1, the molar ratio of the mixed solution to the quaternary ammonium agent is 1:2.

7.

6. The method for preparing a quaternized covalent triazine regular pore anion exchange membrane according to claim 1, characterized in that: In step 2, the compound B is 4,4'-biphenylcarbonitrile, [1,1':4',1"-terphenyl]-4,4"-dicarbonitrile or [1,1':4',1"-terphenyl]-4,4"-dicarbonitrile.

7. The method for preparing a quaternized covalent triazine regular pore anion exchange membrane according to claim 1, characterized in that: In step 2, the molar ratio of quaternized aromatic nitrile to compound B is 1:

2.

8. A quaternized covalent triazine regular pore anion exchange membrane, characterized in that: The method is prepared by any one of claims 1 to 7.

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