Two Zn(II)/Cd(II) coordination polymers based on 5-(3,5-dicarboxybenzyloxy)isophthalic acid for selective detection 4-nitrophenol and fluazinam in aqueous medium

Two new Zn(II)/Cd(II) coordination polymers, namely, {[Zn2(L)(CAS)]·H2O}n (1) and {[Cd2(L)(CAS)]·DMF·H2O}n (2) [H4L = 5-(3,5-dicarboxybenzyloxy)isophthalic acid, CAS = 1,2,4,5-tetra(4-pyridyl)benzene] were synthesized by solvothermal method and characterized by single-crystal X-ray diffraction, elemental analysis, thermogravimetric analysis and powder X-ray diffraction. In complex 1, CAS and Zn(II) are interconnected to form a 2D diamond structure. The 2D layers are interlinked by L4− ligands to generate a 3D network structure. The L4− ligands, CAS and Cd(II) in complex 2 are cross-linked to form a 2D planar structure. The 3D structure is formed by coordination bonds between the two layers. Complexes 1 and 2 could detect p-nitrophenol (4-NP) by fluorescence quenching, and the detection limits were 0.344 and 0.554 μM, respectively. Complex 1 can also be used for sensitive and selective detection of fluazinam (FLU) by fluorescence quenching with the detection limit was 0.185 μM. Additionally, the fluorescence quenching mechanism was also investigated. These new Zn(II)/Cd(II) coordination polymers could be used as dual-functional sensors on NACs and pesticides.