Autocatalytic Synthesis of Bifluoride Ionic Liquids by SuFEx Click Chemistry

Ionic liquids with bifluoride anions possess properties such as high conductivity, wide electrochemical windows, and low viscosity that make them attractive materials for various electrochemical devices. However, owing to the lack of reliable synthetic routes, bifluoride-based ionic liquids have seldom been explored. Herein, an autocatalytic strategy for the HF-free synthesis of bifluoride-based sulfonamide ionic liquids based on the sulfur(VI) fluoride exchange (SuFEx) reaction is reported. This reaction requires no chromatographic purification, and yields are quantitative. The thermophysical properties (phase transition behavior and decomposition temperature) and electrochemical stabilities of the resulting products were studied. The products with alkyl, aryl, and perfluoroalkyl side chains exhibited extraordinarily wide electrochemical windows (up to 6.0 V) with reproducible results among multiple replicate measurements.