Multi-responsive fluorescent sensitivities of a novel 2D Cu-CP with visual turn-off sensing toward nitrofuran antibiotics, Cr(VI) and MnO4− in aqueous solutions

Abstract

Herein, a novel fluorescent coordination polymer [Cu2(edda)(bpy)2]·6H2O (Cu-CP; H4edda = 5,5′-(ethane-1,2-diylbis(oxy)) diisophthalic acid; bpy = 2,2′-bipyridine) was designed and successfully architected using semi-rigid tetracarboxylic acid ligand H4edda combined with N,N′-donor linker bpy through a hydrothermal method. Single-crystal structural analysis reveals that the adjacent Cu1 centers are linked by 3′- and 5- carboxyl groups of edda4− linker to form a one-dimensional Cu(II)-edda4− chain, which is further strutted by 3- and 5′- carboxyl groups in edda4− ligand to generate a two-dimensional (2D) network with sql topology. Notably, bpy molecules do not actually dedicate to the formation of this 2D network, which merely saturate the configuration of Cu ions. Apart from the great thermal and acid/base stabilities, the π-conjugated nature of H4edda endows Cu-CP with the traits of strong fluorescent emission in both solid state and aqueous solution. Interestingly, Cu-CP can act as a multifunctional platform for effectively detecting nitrofurazone (NFZ), nitrofurantoin (NFT), Cr2O72−, CrO42− and MnO4− via fluorescence quenching effects in an aqueous system. The fabricated Cu-CP fluorescent sensor shows distinguished sensitivity and anti-interference performance as well as low detection limits (3.55 nM for NFZ; 1.02 nM for NFT; 0.58 μM for Cr2O72−, 0.68 μM for CrO42− and 4.59 μM for MnO4−). The underlying quenching mechanisms have been studied through in-depth experimental and computational researches.