Vapor-Induced Superionic Conduction of Magnesium Ions in a Metal–Organic Framework
Yuto Yoshida, Kenichi Kato, Masaaki Sadakiyo
Abstract
This is a first report on a novel approach for a significant enhancement in the ionic conductivity of Mg ions in solid, induced by organic vapor. The Mg ions located inside the pores of a metal–organic framework (MOF) exhibited a drastic change in mobility in the presence of anhydrous organic vapors of various guest molecules such as MeOH and MeCN. A systematic study on the ionic conductivity of the model compound, Mg-MOF-74 ⊃ {Mg(TFSI)2}x (x ≤ 0.15), incorporating only the Mg salts inside the pores, under various organic vapors, showed that the MOF adsorbed the guest molecules to form highly mobile ionic carriers and provide an excellent ion-conducting pathways for high ionic conductivity at ambient temperature. Mg-MOF-74 ⊃ {Mg(TFSI)2}0.15 showed a superionic conductivity of 2.6 × 10–4 S cm–1 at 25 °C under MeOH vapor. In addition, this is the first case of the “Mg ion”-conductive MOF with direct evidence of Mg2+ transport (tMg2+ = 0.47, for Mg-MOF-74 ⊃ {Mg(TFSI)2}0.15 under MeCN vapor).