Structure and photoluminescence of two-dimensional lanthanide coordination polymers of mixed phthalate and azobenzene dicarboxylate

A new series of two-dimensional [LnIII(abdc)0.5(phth)(H2O)2]·2H2O coordination frameworks, where LnIII = EuIII (I), GdIII (II), TbIII (III), abdc2− = trans-azobenzene-4,4ʹ-dicarboxylate, and phth2− = phthalate, were designed, synthesized and characterized. According to the single crystal data and powder X-ray diffraction, I–III are isostructural and composed of the two-dimensional [LnIII(abdc)0.5(phth)(H2O)2] layers built up of the one-dimensional [LnIII(phth)(H2O)2] ladders and abdc2− linkers. Similarity in layer registry and identical topology to the other coordination polymers of phth2− are presented, from which the successful implementation of reticular concept is illustrated. Correlation between the framework structures and thermal stability as well as the N2 and CO2 sorption/desorption behaviors are included. Solid state photoluminescence of I–III were then investigated manifesting the substantial influence of abdc2− on the completely silent emission of I–III through the phth2−-to-abdc2− energy transfer.