Enhanced proton conductivity of poly (arylene ether ketone sulfone) containing uneven sulfonic acid side chains by incorporating imidazole functionalized metal-organic framework

In this study, the side-chain type hybrid proton exchange membranes which based on metal-organic frameworks (MOFs) and organic matrix of sulfonated poly (arylene ether ketone sulfone) containing both long and short sulfonic acid side chains (S-C-SPAEKS) were prepared. MOF-801 was used as a template and then imidazole was encapsulated into MOF-801 as additional proton carriers. In imidazole -MOF-801, imidazole was used as a functional group to coordinate with the zirconium metal site of the functional group. Imidazole-MOF-801 and hybrid membranes were characterized by XRD, 1H NMR and FT-IR. These hybrid membranes exhibited excellent proton conductivities and good thermal stabilities. Compared to pure S-C-SPAEKS (0.0487 S cm−1 at 30 °C, 0.0809 S cm−1 at 80 °C), S-C-SPAEKS/0.5% Im-MOF-801 showed a great improvement (0.1205 S cm−1 at 30 °C, 0.1992 S cm−1 at 80 °C), which was about 2.5 times higher than that of pure S-C-SPAEKS and 2 times higher than that of commercial Nafion117 (0.1003 S cm−1 at 80 °C). The results indicated that imidazole functionalized MOFs and uneven side chain structure synergistically made an important contribution to proton transport. This series of hybrid membranes have the potential to be used as alternative proton exchange membranes.