Construction of two Zn(ii)/Cd(ii) multifunctional coordination polymers with mixed ligands for catalytic and sensing properties

With the purpose of exploring the catalytic and sensing properties of crystalline materials, two coordination polymers were rationally constructed by the reactions of Zn(ii)/Cd(ii) ions with methyl-3-hydroxy-5-carboxy-2-thiophenecarboxylate (H2L) and bis(4-pyridylformyl)piperazine (bpfp) mixed ligands. Compound 1 features a 2D layered structure and compound 2 shows a 2D + 2D 3D inclined polycatenation structure. Due to the presence of uncoordinated carbonyl moieties, the two CPs exhibit effective heterogeneous Lewis base catalytic activities to Knoevenagel condensation, and compound 1 shows higher catalytic activity than compound 2 under the same reaction conditions. Interestingly, the two CPs display strong ligand-based photoluminescence both in the solid state and in aqueous solution. More importantly, the sensing test results indicate that compound 2 as a sensor material can selectively recognize l-cysteine through the luminescence quenching effect.