Our investigation on the proton conductivities of two water-stable is structural 3D Co (II) MOFs, {[Co-3(DMPhIDC)(2) (H2O)(6)]center dot 2H(2)O}(n) (1) [DMPhH3IDC = 2-(3,4-dimethylphenyl)-imidazole-4,5-dicarboxylic acid] and {[Co-3(mBrPhIDC)(2)(H2O)(6)]center dot 2H(2)O} (2) [m-BrPhH3IDC = 2-(m-bromophenyl)-imidazole4,5-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 X 10-3 S.cm(-1) and 5.07 X 10(-4) S.cm(-1) (at aqua-ammonia vapor from 1.5 M NH3 center dot H2O solution and 100 degrees C), respectively, which are approximately 1 order of magnitude greater than those maximum values (8.91 x 10(-4) S.cm(-1) and 7.64 X 10(-5) S.cm(-1)) under water vapor (at 98% RH and 100 degrees C). The plausible proton pathways and mechanisms of the MOFs have been proposed in terms of the structural analyses, activation energy calculations, water and NH3 vapor absorptions, and PXRD determinations.