Significantly Enhancing the Lithium Ionic Conductivity of Metal-Organic Frameworks via a Postsynthetic Modification Strategy

Metal-organic frameworks (MOFs), due to their possessing a porous structure, are potential candidates for solid-state ionic conduction materials. Moreover, uncoordinated carboxylic acid groups (-COOH) of MOFs can be used as postsynthetic modification sites, which are favorable for lithium ion exchange. Herein, we synthesized a unique multiple carboxylic zinc metal-organic framework (Zn-MOF-COOH) containing uncoordinated carboxylic acid groups. Zn-MOF-COOLi was synthesized through deprotonation using LiOH via a straightforward acid-base reaction at room temperature (RT), thereby exhibiting better good electrochemical properties. The lithium ionic conductivity (sigma) increased from 1.81 x 10(-5) to 1.65 x 10(-4) S.cm(-1), lithium ion transference number (t(Li)+) rose from 0.67 to 0.77, and the electrochemical window improved from 2.0-5.5 to 1.5-6.5 V. This work offers a new strategy to improve the sigma of MOFs and a new perspective toward manufacturing of high-performance solid-state ionic conduction materials.