A fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane and its preparation method

Abstract

The present invention discloses a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane. Among them, the mass ratio of the fluorene-based sulfonated poly(aryl ether ketone sulfone) to bifunctionalized MIL-101-NH2 is 1:0.02 - 0.06. By introducing a bulky fluorene group into the polymer backbone, the hydrophobicity of the backbone is increased, thereby restricting the swelling phenomenon of the membrane due to excessive water absorption. Moreover, the steric hindrance effect of the fluorene group can reduce the degradation of the backbone by oxidants and improve the oxidation stability of the membrane. Bifunctionalized MIL-101-NH2 with hydrophilic groups carboxyl and amino shows excellent proton conduction ability. The rigid framework of bifunctionalized MIL-101-NH2 can restrict the movement of polymer chains, and the carboxyl and amino groups can form hydrogen bond networks with sulfonic acid groups, improving the performance of the hybrid membrane such as dimensional stability, chemical stability and proton conductivity. Experimental results show that the proton conductivity of the hybrid membrane of the present invention is 0.089 S cm o at 80 ‑1 -0.159 S cm ‑1 , and the thickness of the hybrid membrane is 29 - 79 μm.

Description

Technical Field

[0001] The present invention belongs to the two fields of proton exchange membrane fuel cells and polymer chemistry, and specifically relates to a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane and a preparation method thereof. Background Art

[0002] As one of the core components of proton exchange membrane fuel cells, the proton exchange membrane has always received extensive attention and research. The commonly used proton exchange membrane in the market at present is the perfluorosulfonic acid resin (Nafion) membrane. However, the Nafion membrane has problems such as low high-temperature proton conductivity, poor dimensional stability, and high production cost. Therefore, sulfonated aromatic polymers with excellent thermal stability, chemical stability, and mechanical properties have become the most promising proton exchange membrane materials. Among them, sulfonated poly(aryl ether ketone sulfone) has attracted much attention because of its excellent mechanical properties and thermodynamic stability, and its synthesis method is simple. However, the sulfonated poly(aryl ether ketone sulfone) proton exchange membrane will cause excessive water absorption and swelling of the membrane with the increase of the sulfonation degree, resulting in a decrease in the dimensional stability of the membrane.

[0003] In the process of modifying sulfonated aromatic polymers to obtain high proton conductivity and good mechanical properties, metal-organic frameworks (MOFs) have received extensive attention. Metal-organic frameworks have advantages such as large specific surface area, high porosity, and easy functionalization. Among them, functionalized MOFs can enhance the interfacial compatibility between them and the polymer matrix. And the electrostatic interaction between functionalized MOFs and polymers can weaken the migration ability of polymer molecular chains, enhancing the thermal stability and mechanical properties of the hybrid membrane. At the same time, the hydrophilic functional groups introduced on the MOFs can construct a hydrogen bond network with the sulfonic acid groups on the polymers, forming a continuous proton transport channel and improving the proton conductivity of the hybrid membrane. Summary of the Invention

[0004] To overcome the above-mentioned defects existing in the prior art, the present invention mainly provides a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane and a preparation method thereof. By introducing large-volume rigid fluorene groups into the copolymer molecular chain, the present invention constructs a hydrophobic polymer backbone to limit excessive membrane swelling, and utilizes steric hindrance effects to resist the attack of oxidants, thereby improving the oxidation stability of the material. Meanwhile, the introduction of bifunctional MIL-101-NH2 can effectively improve the proton conductivity, dimensional stability, and mechanical properties of this hybrid proton exchange membrane, and its preparation process is simple. Introducing hydrophilic groups carboxyl and amino into the structure of MIL-101-NH2 to construct bifunctional MIL-101-NH2 can enhance its proton conduction ability. The rigid backbone of bifunctional MIL-101-NH2 can restrict the movement of polymer chains, and the carboxyl and amino groups can form hydrogen bond networks with sulfonic acid groups to improve the dimensional stability and proton conductivity of the hybrid membrane. At the same time, the electrostatic interaction between MOFs and the polymer main chain enables the polymer main chain to be closely stacked, restricting the migration of polymer molecular chains, thereby enhancing the mechanical properties and chemical stability of the hybrid membrane.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention provides a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane, and this hybrid proton exchange membrane is composed of fluorene-containing sulfonated poly(aryl ether ketone sulfone) and bifunctional MIL-101-NH2, wherein the mass ratio of fluorene-containing sulfonated poly(aryl ether ketone sulfone) to bifunctional MIL-101-NH2 is 1:0.02 - 0.06.

[0007] In the above solution, the thickness of the hybrid proton exchange membrane is 29 - 79 μm.

[0008] The present invention also provides a preparation method of a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane, which comprises the following steps:

[0009] Step 1: Prepare a solution of fluorene-containing sulfonated poly(aryl ether ketone sulfone);

[0010] Step 2: Add an appropriate amount of bifunctional MIL-101-NH2 to the solution of fluorene-containing sulfonated poly(aryl ether ketone sulfone) obtained in Step 1 to obtain a casting solution;

[0011] Step 3: Cast the casting solution obtained in Step 2 to obtain a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid proton exchange membrane for fuel cells.

[0012] Preferably, the bisphenol monomer is bisphenol AF, bisphenol A, bisphenol B, tetrabromobisphenol A, hexafluorobisphenol A, dimethylbisphenol A, tetrabromobisphenol A, 2,2'-diallylbisphenol A, 4,4'-(1-phenylethyl)bisphenol, tetramethylbiphenyldiol, or allylbisphenol S.

[0013] Preferably, the solvent is one of sulfolane, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), or dimethyl sulfoxide (DMSO).

[0014] Preferably, the water-carrying agent is toluene, benzene, xylene, or petroleum ether.

[0015] In the above solution, the preparation method of the fluorene-based sulfonated poly(aryl ether ketone sulfone) solution in Step 1 is as follows:

[0016] At room temperature, add the fluorene-based sulfonated poly(aryl ether ketone sulfone) to the solvent and stir for 24 - 48 hours to obtain a uniform solution of the fluorene-based sulfonated poly(aryl ether ketone sulfone). The mass-volume fraction of the fluorene-based sulfonated poly(aryl ether ketone sulfone) solution is 0.03 - 0.06 g / mL. Preferably, the solvent is one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), or dichloromethane (DCM).

[0017] In the above solution, the preparation method of the casting solution in Step 2 is as follows:

[0018] Add the bifunctionalized MIL-101-NH2 to the fluorene-based sulfonated poly(aryl ether ketone sulfone) solution, ultrasonically disperse for 1 - 3 hours, and continue to stir for 1 - 2 days to obtain a uniformly dispersed solution. Among them, the mass ratio of the fluorene-based sulfonated poly(aryl ether ketone sulfone) to the bifunctionalized MIL-101-NH2 is 1:0.02 - 0.06.

[0019] In the above solution, the specific operation of Step 3 is as follows:

[0020] Cast the casting solution on a clean glass plate of 8 cm × 8 cm, place it in an oven at 60 - 80 °C and dry for 48 - 72 hours, demold with deionized water, then acidify with sulfuric acid for 24 - 48 hours, and then wash with deionized water until the acid on the membrane surface is completely removed to obtain a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane for fuel cells.

[0021] In the above solution, the preparation method of the fluorene-based sulfonated poly(aryl ether ketone sulfone) is as follows:

[0022] Under nitrogen protection, a mol of bisphenol fluorene, b mol of 4,4'-difluorobenzophenone, c mol of 4,4'-sulfonyldichlorodiphenyl sulfone and d mol of bisphenol monomer are added into a three-necked flask (100 ml). Subsequently, a certain amount of solvent, water-carrying agent and salt-forming agent are added into the above three-necked flask, and then the condensation reflux and mechanical stirring are turned on. The temperature is raised to 130-140 °C to start water-carrying, and the water-carrying agent is discharged after 4-5 hours of condensation reflux. Subsequently, the temperature is raised to 170-180 °C and the reaction is continued for 4-7 hours. The viscous solution is discharged into deionized water to obtain fluorene-based sulfonated poly(aryl ether ketone sulfone), where a + d = b + c.

[0023] Preferably, the bisphenol monomer is preferably bisphenol A, bisphenol B, tetrabromobisphenol A, hexafluorobisphenol A, dimethylbisphenol A, tetrabromobisphenol A, 2,2'-diallylbisphenol A, 4,4'-(1-phenylethyl)bisphenol, tetramethylbiphenol or allylbisphenol S, more preferably bisphenol AF. The solvent is preferably N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and most preferably sulfolane. The salt-forming agent is anhydrous potassium carbonate, and the water-carrying agent is benzene, xylene, petroleum ether, and most preferably toluene.

[0024] In the above scheme, the preparation method of the bifunctional MIL-101-NH2 metal-organic framework is as follows:

[0025] 1 - 20 parts of 2 - aminoterephthalic acid and 1 - 32 parts of chromium(III) nitrate nonahydrate are dissolved in sodium hydroxide solution in turn. Stir magnetically at room temperature until the solid is completely dissolved. After ultrasonicating the solution for 1 - 3 hours, transfer it to a reaction kettle and react at 120 - 170 °C for 24 - 48 hours. After the reaction is completed, centrifuge and wash the solution. Place it at 60 - 80 °C for 24 - 36 hours for drying to obtain the product MIL - 101 - NH2. At 0 - 35 °C, 0.1 - 1 g of L - glutamic acid, 3 - 10 ml of distilled water, 3 - 10 ml of solvent, and 1 - 5 ml of acid - binding agent are added to a three - necked flask equipped with mechanical stirring in turn. After the solid is completely dissolved, slowly drop 0.5 - 2.5 g of di - tert - butyl dicarbonate solution into the above - mentioned solution. After the dropping is completed, react for 4 - 6 hours. After the reaction is completed, remove the solvent and acid - binding agent by reduced pressure distillation. Add 5 - 15 ml of water, extract with an organic solvent, and combine the organic layers. Filter the organic layer dried with 5 - 10 g of anhydrous magnesium sulfate by suction filtration and concentrate the filtrate under reduced pressure. Lyophilize the concentrated solution for 1 - 3 days, and recrystallize the lyophilized product in an organic solvent. Obtain glutamic acid with protected amino group. At 0 - 15 °C, add the glutamic acid with protected amino group and 0.2 - 2 g of 1 - (3 - dimethylaminopropyl) - 3 - ethylcarbodiimide hydrochloride (EDCI) to 10 - 30 ml of buffer solution. After stirring for 0.5 - 1 hour, add 0.1 - 1.5 g of N - hydroxysuccinimide (NHS) and 0.1 - 1.1 g of MIL - 101 - NH2 to the solution, ultrasonicate for 30 - 90 minutes, and then stir for 3 - 4 hours. After the reaction is completed, centrifuge and wash it. Dry at 60 - 80 °C for 24 - 36 hours. Add the product to 40 - 60 ml of dichloromethane (DCM), and slowly drop 20 - 55 ml of trifluoroacetic acid (TFA) into the above - mentioned solution. Stir at room temperature for 6 - 8 hours. After the reaction is completed, centrifuge the solution. Dry at 60 - 80 °C for 24 - 36 hours. Obtain bifunctionalized MIL - 101 - NH2.

[0026] Preferably, in the bifunctionalized MIL - 101 - NH2, the molar ratio of 2 - aminoterephthalic acid to chromium(III) nitrate nonahydrate is 1:1 - 1.2, and the molar ratio of MIL - 101 - NH2 to glutamic acid is 1:0.9 - 1.2.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The present invention first provides a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane. Among them, the mass ratio of the fluorene-based sulfonated poly(aryl ether ketone sulfone) to bifunctionalized MIL-101-NH2 is 1:0.02 - 0.06. Introducing a fluorene group into the main chain is beneficial to improving the hydrophobicity of the main chain. Under the synergistic effect of the hydrophobic main chain and the steric hindrance of the fluorene group, the oxidation stability of the membrane is improved. In addition, the rigid fluorene group can improve the dimensional stability of the main chain. MIL-101-NH2 with excellent thermodynamic properties and chemical stability was synthesized by a hydrothermal synthesis method. Bifunctionalized MIL-101-NH2 with both amino and carboxyl groups was prepared by an amidation reaction. Bifunctionalized MIL-101-NH2 has both proton acceptors and donors, which can accelerate the proton transport rate. In addition, the electrostatic interaction between the amino group and the main chain sulfonic acid group, as well as the hydrogen bond network formed between the amino, carboxyl, and sulfonic acid groups, can not only increase the compatibility between the MOFs and the polymer matrix, thereby improving the dimensional stability, chemical stability, and mechanical properties of the hybrid membrane, but also improve the proton conductivity of the hybrid membrane. The experimental results show that the proton conductivity of the hybrid membrane of the present invention is 0.089 S cm -1 -0.159 S cm -1 , and the thickness of the hybrid membrane is 29 - 79 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the change curve of the proton conductivity of the hybrid membrane;

[0030] Figure 2 is the change curve of the thermal stability of the hybrid membrane. DETAILED IMPLEMENTATION METHODS

[0031] The present invention will be further described below in conjunction with the embodiments.

[0032] Example 1

[0033] A fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane for fuel cells and its preparation method are as follows:

[0034] (1) Under nitrogen protection, 0.4 mol of bisphenol fluorene, 0.7 mol of 4,4'-difluorobenzophenone, 0.3 mol of 4,4'-sulfonyldichlorodiphenylsulfone and 0.6 mol of bisphenol monomer were added into a three-necked flask (100 ml). Subsequently, sulfolane, toluene and anhydrous potassium carbonate were added into the above three-necked flask, and then the condenser reflux and mechanical stirring were turned on. The temperature was raised to 130 - 140 °C to start water-carrying, and the water-carrying agent was discharged after 4 - 5 hours of condenser reflux. Subsequently, the temperature was raised to 170 - 180 °C and the reaction continued for 4 - 7 hours. The viscous solution was discharged into deionized water to obtain fluorene-based sulfonated poly(aryl ether ketone sulfone). Among them, the bisphenol monomer is preferably bisphenol A, bisphenol B, tetrabromobisphenol A, hexafluorobisphenol A, dimethylbisphenol A, tetrabromobisphenol A, 2,2'-diallylbisphenol A, 4,4'-(1-phenylethyl)bisphenol, tetramethylbiphenyldiol or allylbisphenol S, and more preferably bisphenol AF;

[0035] (2) 0.018 g of sodium hydroxide was weighed and dissolved in 54 ml of deionized water. 0.326 g of 2-aminoterephthalic acid and 0.72 g of chromium(III) nitrate nonahydrate were weighed and dissolved in the above solution. The solution was stirred at room temperature until the solids were completely dissolved. After ultrasonic treatment of the solution for 1 hour, it was transferred to a reaction kettle and reacted at 150 °C for 24 hours. After the reaction was completed, the solution was centrifuged and washed, washed three times with DMF, three times with water, and twice with ethanol. It was dried at 80 °C for 24 hours to obtain the product MIL-101-NH2;

[0036] (3) Under the condition of 20 °C, 0.736 g of L-glutamic acid was weighed and added into a three-necked flask (100 ml). 5 ml of distilled water, 5 ml of acetone and 2.1 ml of triethylamine were respectively measured and added into the above three-necked flask, and mechanical stirring was started. 1.2 g of di-tert-butyl dicarbonate was completely dissolved in 5 ml of acetone, and it was added dropwise to the above solution. The reaction was carried out for 6 hours. After the reaction was completed, acetone and triethylamine were removed by distillation under reduced pressure, and then it was dissolved in 5 ml of water. It was extracted three times with anhydrous ether and four times with ethyl acetate, and the organic layers were combined. It was washed twice with saturated brine, and the organic layer was dried with anhydrous sodium sulfate. After drying was completed, the filtrate was obtained by suction filtration. The filtrate was concentrated under reduced pressure, and the concentrated solution was freeze-dried for 2 days. The freeze-dried product was recrystallized from ethyl acetate - petroleum ether (volume ratio 1:2) to obtain glutamic acid with protected amino group;

[0037] (4) At 0 - 5 °C, weigh 0.846 g of amino - protected glutamic acid and 0.838 g of EDCI, add them to 20 ml of buffer solution, and stir for 0.5 - 1 hour. Weigh 0.414 g of NHS and a certain amount of MIL - 101 - NH2, add them to the above - mentioned solution, ultrasonicate for 30 minutes and then stir for 3 - 4 hours. After the reaction is completed, centrifuge and wash the solution, and wash it 3 times with water. Dry it at 80 °C for 24 hours. Add the product to a 50 - ml beaker containing 11 ml of DCM, dropwise add 5.5 ml of TFA to the solution, and stir at room temperature for 6 - 8 hours. After the reaction is completed, centrifuge the solution and dry it at 80 °C for 24 hours. Obtain bifunctionalized MIL - 101 - NH2;

[0038] (5) Weigh 0.3 g of fluorene - containing sulfonated poly(aryl ether ketone sulfone) and put it into a beaker, add 10 ml of N - methylpyrrolidone (NMP) solvent, and stir at room temperature for 24 hours to obtain a homogeneous solution. The preferred solvents include, but are not limited to, N,N - dimethylformamide (DMF), N,N - dimethylacetamide (DMAc), N - methylpyrrolidone (NMP), or dimethyl sulfoxide (DMSO), dichloromethane (DCM);

[0039] (6) Weigh 0.006 g of bifunctionalized MIL - 101 - NH2 and add it to the homogeneous solution in step (5). Ultrasonically disperse for 3 hours, and then continue magnetic stirring for 48 hours, where the mass ratio of fluorene - containing sulfonated poly(aryl ether ketone sulfone) to bifunctionalized MIL - 101 - NH2 in the mixed solution is 1:0.02.

[0040] Cast the casting solution obtained in step (6) onto a clean glass plate of 8 cm × 8 cm, place it in an oven at 80 °C and dry for 48 hours. After naturally cooling to room temperature, demold it in deionized water, acidify it with 2 mol / L sulfuric acid for 24 hours, and then repeatedly rinse it in deionized water to remove the residual sulfuric acid, thus obtaining a fluorene - containing sulfonated poly(aryl ether ketone sulfone) hybrid membrane. Test the obtained fluorene - containing sulfonated poly(aryl ether ketone sulfone) hybrid membrane at 80 °C, and the conductivity of the hybrid membrane is 0.132 S cm -1 , the membrane thickness is 33 μm. Test it at 30 °C, and its conductivity is 0.069 S cm -1 .

[0041] Example 2

[0042] (1) Under nitrogen protection, 0.4 mol of bisphenol fluorene, 0.7 mol of 4,4'-difluorobenzophenone, 0.3 mol of 4,4'-sulfonyldichlorodiphenylsulfone and 0.6 mol of bisphenol monomer were added into a three-necked flask (100 ml). Subsequently, sulfolane, toluene and anhydrous potassium carbonate were added into the above three-necked flask, and then the condensation reflux and mechanical stirring were turned on. The temperature was raised to 125 - 130 °C to start water-carrying, and the water-carrying agent was discharged after 4 - 5 hours of condensation reflux. Subsequently, the temperature was raised to 170 - 175 °C and the reaction was continued for 4 - 7 hours. The viscous solution was discharged into deionized water to obtain fluorene-based sulfonated polyaryletherketone sulfone. Among them, the bisphenol monomer is preferably bisphenol A, bisphenol B, tetrabromobisphenol A, hexafluorobisphenol A, dimethylbisphenol A, tetrabromobisphenol A, 2,2'-diallylbisphenol A, 4,4'-(1-phenylethyl)bisphenol, tetramethylbiphenyldiol or allylbisphenol S, and more preferably bisphenol AF;

[0043] (2) 0.018 g of sodium hydroxide was weighed and dissolved in 54 ml of deionized water. 0.326 g of 2-aminoterephthalic acid and 0.72 g of chromium(III) nitrate nonahydrate were weighed and dissolved in the above solution. The solution was stirred at room temperature until the solids were completely dissolved. After ultrasonic treatment of the solution for 1 hour, it was transferred to a reaction kettle and reacted at 150 °C for 24 hours. After the reaction was completed, the solution was centrifuged and washed, washed three times with DMF, three times with water, and twice with ethanol. It was dried at 80 °C for 24 hours to obtain the product MIL-101-NH2;

[0044] (3) Under the condition of 20 °C, 0.736 g of L-glutamic acid was weighed and added into a three-necked flask (100 ml). 5 ml of distilled water, 5 ml of acetone and 2.1 ml of triethylamine were respectively measured and added into the above three-necked flask, and mechanical stirring was started. 1.2 g of di-tert-butyl dicarbonate was completely dissolved in 5 ml of acetone and added dropwise to the above solution. The reaction was carried out for 6 hours. After the reaction was completed, acetone and triethylamine were removed by distillation under reduced pressure, and then it was dissolved in 5 ml of water. It was extracted three times with anhydrous ether and four times with ethyl acetate, and the organic layers were combined. It was washed twice with saturated brine, and the organic layer was dried with anhydrous sodium sulfate. After drying was completed, the filtrate was obtained by suction filtration, the filtrate was concentrated under reduced pressure, the concentrated solution was freeze-dried for 2 days, and the freeze-dried product was recrystallized in ethyl acetate - petroleum ether (volume ratio 1:2) to obtain glutamic acid with protected amino group;

[0045] (4) At 0 - 5 °C, weigh 0.846 g of amino - protected glutamic acid and 0.838 g of EDCI, add them to 20 ml of buffer solution, and stir for 0.5 - 1 hour. Weigh 0.414 g of NHS and a certain amount of MIL - 101 - NH2, add them to the above - mentioned solution, ultrasonicate for 30 minutes and then stir for 3 - 4 hours. After the reaction is completed, centrifuge and wash the solution, and wash it 3 times with water. Dry it at 80 °C for 24 hours. Add the product to a 50 - ml beaker containing 11 ml of DCM, dropwise add 5.5 ml of TFA to the solution, and stir at room temperature for 6 - 8 hours. After the reaction is completed, centrifuge the solution and dry it at 80 °C for 24 hours. Obtain bifunctionalized MIL - 101 - NH2;

[0046] (5) Weigh 0.3 g of fluorene - containing sulfonated poly(aryl ether ketone sulfone) and put it into a beaker, add 10 ml of N - methylpyrrolidone (NMP) solvent, and stir at room temperature for 24 hours to obtain a homogeneous solution. The preferred solvents include, but are not limited to, N,N - dimethylformamide (DMF), N,N - dimethylacetamide (DMAc), N - methylpyrrolidone (NMP), or dimethyl sulfoxide (DMSO), dichloromethane (DCM);

[0047] (6) Weigh 0.012 g of bifunctionalized MIL - 101 - NH2 and add it to the homogeneous solution in step (5). Ultrasonically disperse for 3 hours, and then continue magnetic stirring for 48 hours, where the mass ratio of fluorene - containing sulfonated poly(aryl ether ketone sulfone) to bifunctionalized MIL - 101 - NH2 in the mixed solution is 1:0.04.

[0048] Cast the casting solution obtained in step (6) onto a clean glass plate of 8 cm × 8 cm, put it into an oven at 80 °C and dry for 48 hours. After naturally cooling to room temperature, demold it in deionized water, acidify it with 2 mol / L sulfuric acid for 24 hours, and then repeatedly rinse it in deionized water to remove the residual sulfuric acid, thus obtaining a fluorene - containing sulfonated poly(aryl ether ketone sulfone) hybrid membrane. Test the obtained fluorene - containing sulfonated poly(aryl ether ketone sulfone) hybrid membrane at 80 °C, and the conductivity of the hybrid membrane is 0.159 S cm -1 , the membrane thickness is 33 μm. Test it at 30 °C, and its conductivity is 0.104 S cm -1 .

[0049] Example 3

[0050] (1) Under nitrogen protection, 0.4 mol of bisphenol fluorene, 0.7 mol of 4,4'-difluorobenzophenone, 0.3 mol of 4,4'-sulfonyldichlorodiphenylsulfone and 0.6 mol of bisphenol monomer were added to a three-necked flask (100 ml). Subsequently, sulfolane, toluene and anhydrous potassium carbonate were added to the above three-necked flask, and then the condensation reflux and mechanical stirring were turned on. The temperature was raised to 120 - 130 °C to start water-carrying, and the water-carrying agent was discharged after 4 - 5 hours of condensation reflux. Subsequently, the temperature was raised to 170 - 175 °C and the reaction was continued for 4 - 7 hours. The viscous solution was discharged into deionized water to obtain fluorene-based sulfonated poly(aryl ether ketone sulfone). Among them, the bisphenol monomer is preferably bisphenol A, bisphenol B, tetrabromobisphenol A, hexafluorobisphenol A, dimethylbisphenol A, tetrabromobisphenol A, 2,2'-diallylbisphenol A, 4,4'-(1-phenylethyl)bisphenol, tetramethylbiphenyldiol or allylbisphenol S, and more preferably bisphenol AF;

[0051] (2) 0.018 g of sodium hydroxide was weighed and dissolved in 54 ml of deionized water. 0.326 g of 2-aminoterephthalic acid and 0.72 g of chromium(III) nitrate nonahydrate were weighed and dissolved in the above solution. It was stirred at room temperature until the solid was completely dissolved. The solution was ultrasonicated for 1 hour and then transferred to a reaction kettle and reacted at 150 °C for 24 hours. After the reaction, the solution was centrifuged and washed, washed three times with DMF, three times with water, and twice with ethanol. It was dried at 80 °C for 24 hours to obtain the product MIL-101-NH2;

[0052] (3) Under the condition of 20 °C, 0.736 g of L-glutamic acid was weighed and added to a three-necked flask (100 ml). 5 ml of distilled water, 5 ml of acetone and 2.1 ml of triethylamine were respectively measured and added to the above three-necked flask, and mechanical stirring was started. 1.2 g of di-tert-butyl dicarbonate was completely dissolved in 5 ml of acetone, and it was added dropwise to the above solution. The reaction was carried out for 6 hours. After the reaction was completed, acetone and triethylamine were removed by distillation under reduced pressure, and then it was dissolved in 5 ml of water. It was extracted three times with anhydrous ether and four times with ethyl acetate, and the organic layers were combined. It was washed twice with saturated brine, and the organic layer was dried with anhydrous sodium sulfate. After drying, the filtrate was obtained by suction filtration, the filtrate was concentrated under reduced pressure, the concentrated solution was freeze-dried for 2 days, and the freeze-dried product was recrystallized in ethyl acetate - petroleum ether (volume ratio 1:2) to obtain glutamic acid with protected amino group;

[0053] (4) At 0 - 5 °C, weigh 0.846 g of amino - protected glutamic acid and 0.838 g of EDCI, add them to 20 ml of buffer solution, and stir for 0.5 - 1 hour. Weigh 0.414 g of NHS and a certain amount of MIL - 101 - NH2, add them to the above - mentioned solution, ultrasonicate for 30 minutes and then stir for 3 - 4 hours. After the reaction is completed, centrifuge and wash the solution, and wash it 3 times with water. Dry it at 80 °C for 24 hours. Add the product to a 50 - ml beaker containing 11 ml of DCM, dropwise add 5.5 ml of TFA to the solution, and stir at room temperature for 6 - 8 hours. After the reaction is completed, centrifuge the solution and dry it at 80 °C for 24 hours to obtain bifunctionalized MIL - 101 - NH2;

[0054] (5) Weigh 0.3 g of fluorene - containing sulfonated poly(aryl ether ketone sulfone) and put it into a beaker, add 10 ml of N - methylpyrrolidone (NMP) solvent, and stir at room temperature for 24 hours to obtain a homogeneous solution. The preferred solvents include, but are not limited to, N,N - dimethylformamide (DMF), N,N - dimethylacetamide (DMAc), N - methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), or dichloromethane (DCM);

[0055] (6) Weigh 0.018 g of bifunctionalized MIL - 101 - NH2 and add it to the homogeneous solution obtained in step (5). Ultrasonically disperse for 3 hours, and then continue magnetic stirring for 48 hours, where the mass ratio of fluorene - containing sulfonated poly(aryl ether ketone sulfone) to bifunctionalized MIL - 101 - NH2 in the mixed solution is 1:0.06.

[0056] Cast the casting solution obtained in step (6) onto a clean glass plate of 8 cm×8 cm, put it into an oven at 80 °C and dry for 48 hours. After naturally cooling to room temperature, demold it in deionized water, acidify it with 2 mol / L sulfuric acid for 24 hours, and then repeatedly rinse it in deionized water to remove the residual sulfuric acid, thus obtaining a fluorene - containing sulfonated poly(aryl ether ketone sulfone) hybrid membrane.

[0057] The obtained fluorene - containing sulfonated poly(aryl ether ketone sulfone) hybrid membrane was tested at 80 °C. The conductivity of the hybrid membrane was 0.083 S cm -1 , the membrane thickness was 33 μm. When tested at 30 °C, its conductivity was 0.025 S cm -1 .

[0058] Figure 1 This is a graph showing the variation of proton conductivity with temperature for pure fluorene - containing sulfonated poly(aryl ether ketone sulfone) in the present invention, and the hybrid membranes prepared in Example 1, Example 2, and Example 3. Among them, the hybrid membrane prepared in Example 2 has the highest proton conductivity.

[0059] Figure 2Thermogravimetric curves of pure fluorene-based sulfonated poly(aryl ether ketone sulfone) (F-SPAEKS), and hybrid membranes prepared in Example 1, Example 2, and Example 3 in the present invention. The addition of bifunctionalized MIL-101-NH2 significantly improves the thermal stability of the hybrid membranes. The hybrid membranes have three decomposition stages in the TGA curve. The first decomposition stage is at 40 °C - 240 °C, and the weight loss in this stage is due to the volatilization of residual moisture and solvents in the hybrid membranes. The second decomposition stage is between 300 °C - 450 °C. At around 300 °C, the sulfonic acid groups on the polymer main chain and the glutamic acid branches on the bifunctionalized MIL-101-NH2 begin to detach and degrade. Finally, above 500 °C, the polymer main chain and the MOF metal-organic framework are thermally decomposed.

[0060] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane, characterized in that, This hybrid membrane is composed of a fluorene-containing sulfonated poly(aryl ether ketone sulfone) blended with an amino- and carboxyl-functionalized MIL-101-NH2 metal-organic framework. Among them, the mass ratio of the fluorene-containing sulfonated poly(aryl ether ketone sulfone) to the amino- and carboxyl-functionalized MIL-101-NH2 is 1:0.

04. Among them, for the amino- and carboxyl-functionalized MIL-101-NH2 metal-organic framework, its preparation method is as follows: Dissolve 1-20 parts of 2-aminoterephthalic acid and 1-32 parts of chromium(III) nitrate nonahydrate in a sodium hydroxide solution in sequence, and magnetically stir at room temperature until the solid is completely dissolved. After ultrasonicating the solution for 1-3 hours, transfer it to a reaction kettle and react at 120-170 °C for 24-48 hours. After the reaction is completed, centrifuge and wash the solution, and place it at 60-80 °C for 24-36 hours for drying to obtain the product MIL-101-NH2. At 0-35 °C, add 0.1-1 g of L-glutamic acid, 3-10 mL of distilled water, 3-10 mL of acetone, and 1-5 mL of acid-binding agent to a three-necked flask in sequence. After the solid is completely dissolved, slowly drop 0.5-2.5 g of di-tert-butyl dicarbonate solution into the above solution. After the dropping is completed, react for 4-6 hours. After the reaction is completed, remove the solvent and the acid-binding agent by vacuum distillation, add 5-15 mL of water, extract with an organic solvent, combine the organic layers, filter the organic layer dried with 5-10 g of anhydrous magnesium sulfate by suction filtration, concentrate the filtrate under reduced pressure, lyophilize the concentrated solution for 1-3 days, and recrystallize the lyophilized product in an organic solvent to obtain glutamic acid with protected amino groups. At 0-15 °C, add 0.1-1 g of glutamic acid with protected amino groups and 0.2-2 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride to 10-30 mL of buffer solution, stir for 0.5-1 hour, then add 0.1-1.5 g of N-hydroxysuccinimide (NHS) and 0.1-1.1 g of MIL-101-NH2 to the solution, ultrasonicate for 30-90 minutes and then stir for 3-4 hours. After the reaction is completed, centrifuge and wash it, and dry it at 60-80 °C for 24-36 hours. Add the product to 40-60 mL of dichloromethane (DCM), and slowly drop 20-55 mL of trifluoroacetic acid (TFA) into the above solution, stir at room temperature for 6-8 hours. After the reaction is completed, centrifuge the solution and dry it at 60-80 °C for 24-36 hours to obtain the amino- and carboxyl-functionalized MIL-101-NH2 metal-organic framework.

2. The preparation method of a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane according to claim 1, characterized in that, The organic part is a fluorene-based sulfonated poly(aryl ether ketone sulfone), and its preparation method is as follows: Under nitrogen protection, a mol of bisphenol fluorene, b mol of 4,4'-difluorobenzophenone, c mol of 4,4'-sulfonated dichlorodiphenyl sulfone and d mol of bisphenol monomer are added to a 100 mL three-necked flask. Subsequently, a certain amount of solvent, water-carrying agent and salt-forming agent are added to the above three-necked flask, and the condensation reflux and mechanical stirring are started. The temperature is raised to 130-140 o °C to start water-carrying, and the water-carrying agent is discharged after 4-5 hours of condensation reflux. Subsequently, the temperature is raised to 170-180 o °C and the reaction is continued for 4-7 hours. The viscous solution is discharged into deionized water to obtain a fluorene-based sulfonated poly(aryl ether ketone sulfone), where a + d = b + c.

3. The preparation method of a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane according to claim 2, wherein For the fluorene-containing sulfonated poly(aryl ether ketone sulfone), the bisphenol monomers described in its preparation method are bisphenol A, bisphenol B, tetrabromobisphenol A, hexafluorobisphenol A, dimethylbisphenol A, 2,2'-diallylbisphenol A, 4,4'-(1-phenylethyl)bisphenol, tetramethylbiphenyldiol, or allylbisphenol S, the solvent is N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, or sulfolane, the salt-forming agent is anhydrous potassium carbonate, and the water-carrying agent is benzene, xylene, petroleum ether, or toluene.

4. The preparation method of a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane according to claim 1, characterized in that, The molar ratio of the above-mentioned 2-aminoterephthalic acid to chromium(III) nitrate nonahydrate is 1:1-1.

6.

5. The preparation method of a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane according to claim 1, characterized in that, It includes the following steps: Step 1: Prepare a sulfonated poly(aryl ether ketone sulfone) solution containing a fluorene group; Step 2: Add an appropriate amount of amino- and carboxyl-functionalized MIL-101-NH2 to the sulfonated poly(aryl ether ketone sulfone) solution containing a fluorene group obtained in Step 1 to obtain a casting solution; Step 3: Cast the casting solution obtained in Step 2 to obtain a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane for fuel cells.

6. The preparation method of a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane according to claim 5, characterized in that, The preparation method of the sulfonated poly(aryl ether ketone sulfone) solution containing a fluorene group in the above Step 1 is as follows: At room temperature, add the sulfonated poly(aryl ether ketone sulfone) containing a fluorene group to a solvent and stir for 24 - 48 hours to obtain a homogeneous solution of the sulfonated poly(aryl ether ketone sulfone) containing a fluorene group. The mass-volume fraction of the sulfonated poly(aryl ether ketone sulfone) solution containing a fluorene group is 0.03 - 0.06 g / mL.

7. The preparation method of a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane according to claim 5, characterized in that, The preparation method of the sulfonated poly(aryl ether ketone sulfone) / amino- and carboxyl-functionalized MIL-101-NH2 metal-organic framework solution in the above Step 2 is as follows: Add the amino- and carboxyl-functionalized MIL-101-NH2 to the sulfonated poly(aryl ether ketone sulfone) solution, and ultrasonically disperse the solution for 1 - 3 hours, then continue stirring for 1 - 2 days to obtain a uniformly dispersed solution. Among them, the mass ratio of the sulfonated poly(aryl ether ketone sulfone) containing a fluorene group to the amino- and carboxyl-functionalized MIL-101-NH2 is 1:0.

04.

8. The preparation method of a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid membrane according to claim 5, characterized in that, The specific operation steps of the above step three for film laying are as follows: Cast the casting solution on a clean glass plate of 8 cm × 8 cm, and dry it in an oven at 60-80 o °C for 48-72 hours, demold with deionized water, treat it with sulfuric acid acidification for 24-48 hours, and then wash it with deionized water until the acid on the membrane surface is completely removed, to obtain a fluorene-based sulfonated poly(aryl ether ketone sulfone) hybrid proton exchange membrane for fuel cells.

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