A Comparative Investigation of Proton Conductivities for Two Metal?Organic Frameworks under Water and Aqua-Ammonia Vapors

摘要

Our investigation on the proton conductivities of two water-stable isostructural 3D Co(II) MOFs, {[Co_(3)(DMPhIDC)_(2)(H_(2)O)_(6)]·2H_(2)O}_( n ) ( 1 ) [DMPhH_(3)IDC = 2-(3,4-dimethylphenyl)-imidazole-4,5-dicarboxylic acid] and {[Co_(3)( m -BrPhIDC)_(2)(H_(2)O)_(6)]·2H_(2)O} ( 2 ) [ m -BrPhH_(3)IDC = 2-( m -bromophenyl)-imidazole-4,5-dicarboxylic acid], under water or aqua-ammonia vapor shows that the optimized proton conductivities of both 1 and 2 under aqua-ammonia vapor are 4.41 × 10~(–3) S·cm~(–1) and 5.07 × 10~(–4) S·cm~(–1) (at aqua-ammonia vapor from 1.5 M NH_(3)·H_(2)O solution and 100 °C), respectively, which are approximately 1 order of magnitude greater than those maximum values (8.91 × 10~(–4) S·cm~(–1) and 7.64 × 10~(–5) S·cm~(–1)) under water vapor (at 98% RH and 100 °C). The plausible proton pathways and mechanisms of the MOFs have been proposed in terms of the structural analyses, activation energy calculations, water and NH_(3) vapor absorptions, and PXRD determinations.