A pair of structurally isomeric metal-carboxylate frameworks (MCFs) with an identical formula of [Me 2 NH 2 ] 2 [Co 3 (1,4-bdc) 4 ]·4DMF (1 and 2, Me 2 NH 2 = protonated dimethylamine, 1,4-bdcH 2 = 1,4-benzenedicarboxylic acid and DMF = N,N′-dimethylformamide) have been synthesized from identical reactants at 160 °C and room temperature, respectively. Although both compounds feature the same bcg net (a uninodal eight-connected net) based on the Co 3 (OOCR) 8 clusters as eight-connected nodes, the isomers exhibit different magnetic behaviours...