Encapsulating NH4Br in a metal organic framework: achieving remarkable proton conduction in a wide relative humidity range

Abstract

Proton-conducting materials are key components for constructing high-energy-density electronic devices. In this work, by accumulating NH₄Br into the nanospace of the classical metal organic framework MIL-101-Cr, a proton conductivity as high as 1.53 × 10⁻¹ S cm⁻¹ was achieved at 363 K and 100% RH. The proton conduction of NH₄Br@MIL-101-Cr was also high even at lower relative humidity; for instance, it was ∼10⁻² S cm⁻¹ at 75% RH. The activation energy was calculated to be 0.11 eV for NH₄Br@MIL-101-Cr, indicative of tight H-bond networks and a low barrier to proton transfer, and confirming the occurrence of pure proton conduction as well.