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 (σ) increased from 1.81 × 10–5 to 1.65 × 10–4 S·cm–1, lithium ion transference number (tLi+) 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 σ of MOFs and a new perspective toward manufacturing of high-performance solid-state ionic conduction materials.金属有机框架（Metal–organic frameworks, MOFs）因具备多孔结构，成为固态离子传导材料的潜在候选材料。此外，MOFs的未配位羧酸基团（−COOH）可作为后合成修饰位点，有助于锂离子交换。本文合成了一种含未配位羧酸基团的独特多羧酸锌基金属有机框架（Zn-MOF-COOH）。通过氢氧化锂（LiOH）在室温（RT）下经简便的酸碱反应进行去质子化，成功制备得到Zn-MOF-COOLi，该材料展现出更优异的电化学性能：锂离子电导率（σ）从1.81 × 10–5 S·cm–1提升至1.65 × 10–4 S·cm–1，锂离子迁移数（tLi+）从0.67提升至0.77，电化学窗口从2.0–5.5 V拓宽至1.5–6.5 V。本研究为提升MOFs的锂离子电导率提供了新策略，也为高性能固态离子传导材料的制备提供了新视角。