MOF-Directed Synthesis of Crystalline Ionic Liquids with Enhanced Proton Conduction

Arranging ionic liquids (ILs) with long-range order can not only enhance their performance in a desired application, but can also help elucidate the vital between structure and properties. However, this is still a challenge and no example has been reported to date. Herein, we report a feasible strategy to achieve a crystalline IL via coordination self-assembly based reticular chemistry. IL1MOF, was prepared by designing an IL bridging ligand and then connecting them with metal clusters. IL1MOF has a unique structure, where the IL ligands are arranged on a long-range ordered framework but have a labile ionic center. This structure enables IL1MOF to break through the typical limitation where the solid ILs have lower proton conductivity than their counterpart bulk ILs. IL1MOF shows 2-4 orders of magnitude higher proton conductivity than its counterpart IL monomer across a wide temperature range. Moreover, by confining the IL within ultramicropores (<1 nm), IL1MOF suppresses the liquid-solid phase transition temperatures to lower than -150 degrees C, allowing it to function with high conductivity in a subzero temperature range.

Automated summary

By designing a reliable coordination self-assembly method, a crystalline IL for IL1MOF was successfully achieved. IL1MOF has a structure with long-range ordered arrangement and high ionic conductivity, maintaining high conductivity even in subzero temperatures as low as -150 degrees Celsius.