A Three-Dimensional Porous Mn(II)-Metal–Organic Framework Based on a Caged Structure Showing High Room-Temperature Proton Conductivity

Abstract

A metal–organic framework (MOF) from Mn(II) salts and 2,6-dicarboxy-4-hydroxypyridine, formulated as (H3O)[(Mn4(CAM)3]·H2O (1) (H3CAM = chelidamic acid or 2,6-dicarboxy-4-hydroxypyridine), was obtained. The compound was characterized by infrared spectrometry, thermogravimetric analysis, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and single-crystal XRD. Complex 1 contains a H3O+ counterion and a porous three-dimensional porous anionic network with large cage cavities constructed by the Mn(II) center and the μ6-2,6-dicarboxy-4-hydroxypyridine ligand. The compound shows a high proton conductivity (s) of 2.06 × 10–3 S cm–1 at 25 °C under 100% relative humidity, which exceeds the room-temperature proton conductivities of most reported proton conductors of cage-based MOFs.