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

Abstract

Four new coordination polymers, [Zn(TPTA)_0.5(BIBP)] (1), [Mn(TPTA)_0.5(BIBP)_0.5(DMF)] (2), [Zn_1.5(TPTA)]·DMF·H₂O (3), and [Cd_1.5(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.