Assembly of four new cobalt coordination polymers modulated by N-coligands: sensitive and selective sensing of nitroaromatics, Fe3+ and Cr2O72− in water†
Four new Co coordination polymers (CPs), formulated as [Co(L)(phen)] (1, 1D), [Co3(L)3(phen)2·4H2O] (2, 2D), [Co3(L)3(2,2′-bipy)2·8H2O] (3, 2D) and [Co2(L)3(4,4′-bipy)2·] (4, 3D) (H2L = 6-methoxy-2,2′-sulfone-4,4′-dicarboxylic acid, phen = 1,10-phenanthroline, 2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine), have been solvothermally synthesized based on a functional dicarboxylate bridging ligand in the presence of various N-coligands. Complex 1 features a 3D supramolecular architecture composed of parallel linear chains assembled via π–π interactions. Complexes 2 and 3 have similar structures, which are both (4,4)-connected 2D networks possessing 1D channels based on linear trinuclear [Zn3(CO2)6N4] clusters. Complex 4 contains (4,4)-connected 2D layers based on binuclear clusters, which are further linked into a 3D pillar-layered framework by 4,4′-bipy. Luminescence studies indicate that 2 and 3 both show strong fluorescence and good stability in water, and they can be used as multi-responsive sensors for selective sensing of nitroaromatics, Fe3+ and Cr2O72− in water via luminescence quenching with fast response. Remarkably, 2 and 3 can be conveniently regenerated for at least four times without sacrificing their quenching efficiencies. The possible mechanisms for the luminescence quenching have been investigated in detail.