Sequential enhancement of proton conductivity by aliovalent cadmium substitution and post-synthetic esterolysis in a carboxylate-functionalized indium framework with dimethylaminium templates

Abstract

A sequential improvement strategy has been devised and implemented on a 3D open framework In-BQ showing 2D intersected channels filled by dimethylamine and its protonated cation constructed by –COOCH₃–functionalized anilicate linkers. In situ aliovalent metal substitution and post-synthetic ligand esterolysis led to Cd-BQ-COOH with a doubling of Me₂NH₂⁺ carriers and a great number of residual –COOH groups, resulting in maximum proton concentration and frequent jumping sites. As a result, the modified Cd-BQ-COOH exhibits a 300-fold enhanced value of proton conductivity compared with that of pristine In-BQ, reaching 6.06 × 10⁻² S cm⁻¹. MD calculations reveal that the entire process of proton transportation in Cd-BQ-COOH is achieved by the vehicle mechanism.