Ionic liquid-loaded metal-organic framework system for nanoionic device applications

Metal-organic frameworks, which are three-dimensional nanoporous materials composed of metal ions and organic ligands, have recently attracted significant attention as functional materials owing to their structural flexibility in the material design of uniform-size nanopores. In this study, basic investigations of the electrical properties of Cu₃(btc)₂ (btc; 1,3,5-benzenetricarboxylic acid) were carried out using single crystalline samples. We determined that the pore-filling solvent absorbed by capillary condensation strongly dominated the electrical properties of Cu₃(btc)₂ single crystals. The extremely dense and highly insulating nanopores of Cu₃(btc)₂ enabled us to use liquids as solids by absorbing the liquids into the nanopores. By loading an ionic liquid, which is composed of tunable ionic compound (salt) with superior characteristics for electrolyte use, this substance can be used as a "solid electrolyte" for application to solid-state nanoionic devices without compromising its original ion transport property. (author)