A Water-Stable Luminescent Zn-II Metal-Organic Framework as Chemosensor for High-Efficiency Detection of Cr-VI-Anions (Cr2O72- and CrO42-) in Aqueous Solution

A new luminescent Zn-II-MOF with 1D triangular channels along the b axis, namely NUM-5, has been successfully assembled and well characterized, which features good stability, especially in aqueous solution. Interestingly, this compound exhibits a fast, sensitive and selective luminescence quenching response towards Cr-VI (Cr2O72-/CrO42-) in aqueous solution. The detection limits towards Cr2O72- and CrO42- ions are estimated to be 0.7 and 0.3 ppm, respectively, which are among the lowest detection limits reported for the MOF-based fluorescent probes that can simultaneously detect Cr2O72- and CrO42- in aqueous environment. The possible detection mechanism has been discussed in detail. Moreover, it can be easily regenerated after detection experiments, indicative of excellent recyclability. All these results suggest NUM-5 to be a highly selective and recyclable luminescent sensing material for the quantitative detection of Cr-VI anions in aqueous solution.