Achieving Superprotonic Conduction with a 2D Fluorinated Metal-Organic Framework

Abstract

A hydrolytically stable metal-organic framework (MOF) material, named KAUST-7′, was derived from a structural phase change of KAUST-7 upon exposure to conditions akin to protonic conduction (363 K/95% relative humidity). KAUST 7′ exhibited a superprotonic conductivity as evidenced by the impedance spectroscopic measurement revealing an exceptional conductivity up to 2.0 × 10-2 S cm-1 at 363 K and under 95% RH, a performance maintained over 7 days. Ab initio molecular dynamics simulations suggested that the water-mediated proton transport mechanism is governed by water assisted reorganization of the H-bond network involving the fluorine moieties in KAUST-7′ and the guest water molecules. The notable level of performances combined with a very good hydrolytic stability positions KAUST-7′ as a prospective proton-exchange membrane alternative to the commercial benchmark Nafion. Furthermore, the remarkable RH sensitivity of KAUST-7′ conductivity, substantially higher than previously reported MOFs, offers great opportunities for deployment as a humidity sensor.