Two Stable Zn (II) Coordination Polymers as Dual-Functional Luminescent Sensors for Efficient Detection of Nitrofurazone, Pefloxacin, and Cr2O72- in Water

Two new Zn (II) coordination polymers, {[Zn (OBA)(L)]<middle dot>H2O}(n) (1) and {[Zn-2(TCPA)(2)(L)(2)]<middle dot>H2O}(n) (2), were synthesized under hydrothermal condition. Here, L = 2-(1H-imidazol-1-yl)methyl)-5,6-dimethyl-1H-benzo[d]imidazole, H(2)OBA = 4,4 '-dicarboxydiphenyl ether, H(2)TCPA = tetrachloroterephthalic acid. Structural analyses revealed that 1 exhibits a 2D hcb topology of {6(3)} while 2 displays a four-connected 2D sql layer with the point symbol of {4(4).6(2)}. Both 1 and 2 are extended to 3D supramolecular frameworks through hydrogen bonding interactions. These CPs demonstrate remarkable thermal and chemical stability across a wide pH range of 3 to 12. Notably, they can serve as dual-functional luminescent sensors for the sensitive, selective, and recyclable detection of nitrofurazone (NFZ)/Cr2O72- ions (for 1) and pefloxacin (PEF)/Cr2O72- ions (for 2) in aqueous solutions. The limits of detection (LODs) of 1 towards NFZ and Cr2O72- ions are 2.20 x 10(-7) and 4.90 x 10(-7) mol<middle dot>L-1, respectively. For 2, the LOD is 5.42 x 10(-8) mol<middle dot>L-1 for PEF and 3.40 x 10(-7) mol<middle dot>L-1 for Cr2O72- ions. It is worth noting that this is the first report of luminescent Zn (II)-CPs based on L ligands for the sensing of NFZ, PEF, and Cr2O72- ions. And the quenching mechanism was deeply investigated.