Efficient Proton Transport in Stable Functionalized Channels of Zirconium Metal–Organic Frameworks

Abstract

Exploring stable proton-conducting materials with high and durable proton conductivity is expected, but it is still a challenge. Here, we report a strategy of modifying the channels of Zr-metal–organic frameworks (MOFs) [UiO-66, Zr6O4(OH)4(bdc)6, bdc = 1,4-benzenedicarboxylate/MOF-808, Zr6O4(OH)4(BTC)2(HCOO)5(H2O)1(OH)1, BTC = benzenetricarboxylate] by an ionic liquid, 1-(propyl-3-sulfonate) imidazolium hydrosulfate, ([(CH2)3SO3H-HIM]HSO4), via the free-solvent reaction to synthesize stable IL@UiO-66 and IL@MOF-808, which show ultrahigh proton conductivities of 1.42 × 10–1 and 7.01 × 10–1 S cm–1 at 70 °C and 98% relative humidity. The conductivity values are comparable to the highest performance of reported MOF-based proton conductors. Furthermore, the proton conduction mechanism of IL@UiO-66 is clearly clarified by the conjoint analysis of the well-defined crystal structure and proton dynamics. Notably, IL@UiO-66 and IL@MOF-808 are fabricated into hybrid membranes with efficient proton transport and good performance stabilities, which lay the foundation for further application. This work provides a basis for studying the proton conduction mechanism and has a promotion on the iterative cycle of understanding, design, and evaluation of advanced proton-conducting materials.