A stable zinc(II)-organic framework as rapid and multi-responsive luminescent sensor for metal ions in water

Abstract

A very stable ZnII-organic framework, {[Zn(Titpe)0.5(bpodc)]·(H2O)3}n (1, Titpe = 1,1,2,2-tetrakis(4-(imidazol-1-yl)phenyl)ethane, bpodc = benzophenone-4,4-dicarboxylic acid), has been synthesized under hydrothermal conditions. Single-crystal X-ray analysis reveals that 1 crystallizes in the monoclinic system and P21/c space group. Its overall structure is a 3-D stacking with a porosity of 20.95% and a 4-c type topological network; it shows good stability in many solvents. Studies of the solution-phase detection of metal cations show that Fe3+ and Cr3+ ions can quench luminescent emission of 1. Fluorescence titration experiments show that 1 is more selective to Fe3+ (Ksv = 2.8 × 104 M−1) than Cr3+ (Ksv = 1.4 × 103 M−1). The solution-phase detection for anions by 1 also show high selectivity and sensitivity for Cr2O72– anions (Ksv = 1.2 × 104 M−1). With water stability and strong blue luminescence, 1 can potentially apply as a reversible multi-responsive luminescence sensor for Fe3+, Cr3+, and Cr2O72– in aqueous solutions.