Immobilization of N-(3-aminopropyl)-imidazole through MOFs in proton conductive membrane for elevated temperature anhydrous applications

The development of anhydrous proton-conductive membranes operating at temperatures above 100°C is a challenge for practical application. To meet the requirements, the N-(3-aminopropyl)-imidazole (NAPI), a proton-carrier molecule, is encapsulated in the frameworks of the Fe-MIL-101-NH2 and then allowed to react with sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) (SPPO) for preparing hybrid proton conductive membrane. Results showed that the dispersed proton conductive metal-organic frameworks (MOFs) in the membrane provide a convenient pathway for proton mobility under high temperature and anhydrous condition. Tuning of the host-guest interaction can generate a good proton-conducting pathway at temperatures above 150°C. It is also presumed that the proton transfer in the membrane is simultaneously contributed from the Grotthuss-type mechanism and the vehicle-type mechanism. This work suggests that a combination of guest molecules and microporous frameworks could afford highly mobile proton carriers in solids. Therefore, the new proton conductive membranes can be designed by incorporating the MOFs into functionalized polymers for applications at high temperature and anhydrous condition.