Single-Crystal-to-Single-Crystal Breathing and Guest Exchange in Co^II Metal–Organic Frameworks

Single-crystal-to-single-crystal (SCSC) breathing and guest exchange properties of a series of CoII metal–organic frameworks (MOFs) are reported. A new bis-pyridyl-bis-amide ligand, namely 4,4′-oxybis­(N-(pyridine-4-yl)­benzamide) (LP1), produced two MOFs, namely [{Co­(LP1)­(IPA)}­(DMF)2(H2O)]∞ (1) and [{Co2(LP1)2(TPA)2}­(DMF)4]∞ (2) under solvothermal conditions (IPA = isophthalate, TPA = terephthlate). While 1 showed excellent SCSC breathing responsive to both heat and guests (acetone, DMSO, MeOH, DEF), 2 displayed no breathing under similar conditions. However, it showed excellent SCSC guest (acetone, DMSO) exchange properties. Single-crystal structural analyses revealed that the conformational flexibility of the ligand LP1 played a crucial role both in breathing in 1 and in guest exchange in 2. Compound 1 also displayed heat responsive magnetic changes.