Achieving High Intrinsic Proton Conductivity via Functionalization of MOF-808 by Ionic Liquid

Achieving high intrinsic proton conductivity is essential for the development of stable proton conductors in proton exchange membrane fuel cells. Herein, an ionic liquid (IL) with a hydrosulfate anion, an imidazole ring, and a sulfonate group beneficial to proton transfer was used to functionalize a metal–organic framework (MOF-808) by replacing the formates coordinated with Zr. The obtained MOF-808-IL exhibits high intrinsic proton conductivity of 1.28 × 10^–1 S cm^–1 at 60 °C and 100% relative humidity (RH), which exceeds those of most of the MOF-based proton conductors. Moreover, the proton transfer mechanism has been elucidated by the combination of the crystal structure and variable temperature Fourier transform infrared spectra. This study provides a strategy for achieving ultrahigh proton conductivity and a model for analyzing the proton conducting mechanism.