Effective Approach to Promoting the Proton Conductivity of Metal–Organic Frameworks by Exposure to Aqua–Ammonia Vapor

We explored the proton conductivities of two 3D Co^II metal–organic frameworks (MOFs), {[Co₃(<i>m</i>-ClPhIDC)₂(H₂O)₆]·2H₂O}_<i>n</i> [<b>1</b>; <i>m</i>-ClPhH₃IDC = 2-(<i>m</i>-chlorophenyl)­imidazole-4,5-dicarboxylic acid] and {[Co₃(<i>p</i>-ClPhHIDC)₃(H₂O)₃]·6H₂O}_<i>n</i> (<b>2</b>; <i>p</i>-ClPhH₃IDC = 2-(<i>p</i>-chlorophenyl)­imidazole-4,5-dicarboxylic acid), under water and aqua–ammonia vapors, respectively. The experimental results revealed that the proton conductivities of <b>1</b> and <b>2</b> at aqua–ammonia vapor were 2.89 × 10^–2 and 4.25 × 10^–2 S/cm, respectively, and approximately 2 orders of magnitude greater than those at water vapor. On the basis of the activation energy, water and ammonia vapor absorption, and powder X-ray diffraction patterns, their proton-conduction mechanisms have been discussed. We believe that this is a novel approach to drastically improving the proton conductivity of MOFs