Cooperative Proton and Li‐ion Conduction in a 2D‐Layered MOF via Mechanical Insertion of Lithium Halides

Abstract Ionic conduction in highly designable and porous metal–organic frameworks has been explored through the introduction of various ionic species (H + , OH − , Li + , etc.) using post‐synthetic modification such as acid, salt, or ionic liquid incorporation. Here, we report on high ionic conductivity ( σ >10 −2 S cm −1 ) in a two‐dimensionally (2D)‐layered Ti‐dobdc (Ti 2 (Hdobdc) 2 (H 2 dobdc), H 4 dobdc: 2,5‐dihydroxyterephthalic acid) via LiX (X=Cl, Br, I) intercalation using mechanical mixing. The anionic species in lithium halide strongly affect the ionic conductivity and durability of conductivity. Solid‐state pulsed‐field gradient nuclear magnetic resonance (PFG NMR ) verified the high mobility of H + and Li + ions in the temperature range of 300–400 K. In particular, the insertion of Li salts improved the H + mobility above 373 K owing to strong binding with H 2 O. Furthermore, the continuous increase in Li + mobility with temperature contributed to the retention of the overall high ionic conductivity at high temperatures.