A newly-constructed hydrolytically stable Co(II) coordination polymer showing dual responsive fluorescence sensing of pH and Cu²⁺

Fluorescent chemosensors based on coordination polymers (CPs) have received particular attention in monitoring the pH values and appropriate analytes in environmental and biological systems owing to their extreme superiorities. Herein, a novel solvent-dependent fluorescent Co(II)-CP, [Co(asba)(2-mmzm) (H2O)(2)]center dot 3H(2)O (1), was obtained through the assembly between Co2+ and 2-amino-4-sulfobenzoic acid (H(2)asba) in the presence of the flexible hydrophobic ligand 1,4-bis[(2-methyl-1H-imidazol-1-yl)methyl] benzene (2-mmzm). 1 is a 1D coordination polymer, which is further linked by a 1D hydrogen-bonded tape into a 3D supramolecular network. 1 shows high hydrolytic stability as well as strong acidic and basic resistance. Remarkably, 1 is a quite rare example that shows dual responsive fluorescence sensing of pH and Cu2+. 1 shows distinct sensing behavior toward pH with interesting different sensing mechanisms in three continuous pH ranges. Moreover, 1 demonstrates high accuracy in determining the pH of artificial gastric juices. 1 could also sensitively and selectively sense Cu2+ ions over a number of interfering metal ions. The limit of detection (LOD) for Cu2+ reaches the 2.4 mu M level.