A water stable and highly fluorescent Zn(ii) based metal–organic framework for fast detection of Hg2+, CrVI, and antibiotics

Abstract

The development of luminescent metal–organic frameworks for effective sensing and monitoring of environmental pollutants is of great significance for human health and environmental protection. In this work, a novel water-stable Zn^II-based luminescent coordination polymer, namely {[Zn(BBDF)(ATP)]·2DMF·3H₂O}_n ((BBDF = 2,7-bis(1H-benzimidazol-1-yl)-9,9-dimethyl-9H-fluorene) and H₂ATP = 2-aminoterephthalic acid), was designed and obtained using the mixed-ligand method. Structural analysis indicated that 1 presents a two-fold interpenetrated two-dimensional layer structure with one dimensional (1D) channels along the a axis. Intriguingly, the uncoordinated –NH₂ group was danged onto the pore walls of 1. Remarkably, compound 1 shows good aqueous stability at different pH values of 3–13 and exhibits a fluorescence turn-off sensing behavior for Hg²⁺, Cr₂O₇²⁻, CrO₄²⁻, and antibiotics (NFZ, NFT) in aqueous solution with high selectivity and sensitivity. The limits of detection (LOD) are 0.12 μM (Hg²⁺), 0.17 μM (Cr₂O₇²⁻), 0.21 μM (CrO₄²⁻), 0.098 μM (NFZ), and 0.14 μM (NFT). The luminescence quenching mechanism analysis by experiment and theoretical calculation revealed that the competitive absorption and the photoinduced electron transfer process are largely responsible for the sensing of the two antibiotics, while the weak interaction contributes to the selective luminescence quenching for Hg²⁺.