Four new coordination polymers based on a pyridinetetracarboxylate ligand: syntheses, structures and high CO2/CH4 separation

Four new coordination polymers, [Zn(TPTA)0.5(BIBP)] (1), [Mn(TPTA)0.5(BIBP)0.5(DMF)] (2), [Zn1.5(TPTA)]·DMF·H2O (3), and [Cd1.5(TPTA)]·DMF·2H2O (4) (H4TPTA = 5,5′-(pyridine-2,5-diyl)diisophthalic acid, BIBP = 4,4′-bis(imidazol-1-yl)biphenyl), have been synthesized under solvothermal conditions and fully characterized. Single-crystal X-ray diffraction analysis revealed that complex 1 is a three-dimensional (3D) 3-fold interpenetrating architecture with (4·64·8)2(42·62·82) topology. Complex 2 possesses a 3D 2-fold interpenetrating framework based on binuclear Mn2 units with (412·63) topology. Both complexes 3 and 4 exhibit trinuclear 3D non-interpenetrating (4,8)-connected networks with (46)2(412·612·84) topology. The fluorescence properties of 1, 3 and 4 have been also measured. Importantly, gas adsorption studies for 1–4 show highly selective adsorption of CO2 over CH4.