A stable zinc-based metal–organic framework as fluorescent sensor for detecting Cr2O72−, Fe3+ and L-Cysteine with high sensitivity and selectivity

In this report, a novel metal–organic framework [Zn(BMTH)]n (1) (H2BMTH = 5,6-benzimidazole diacylhydrazide) based on the coordination of acylhydrazide ligand and Zn2+ was synthesized, in which the H2BMTH ligand was generated via in situ acylation reaction between benzimidazole-5,6-dicarboxylic acid and N2H4. X-ray single-crystal diffraction analyses indicate that compound 1 displays a three-dimensional (3-D) network with the point (Schläfli) symbol of (42⋅63⋅8), where a parallelogram channel with the size of 11.63 × 10.59 Å2 is observed. Furthermore, 1 is a promising luminescent sensor for detecting Cr2O72− and Fe3+. Note that Fe3+ solution was incorporated into compound 1 to construct the new sensor, Fe3+@1. As expected, Fe3+@1 can sense L-Cysteine (L-Cys) selectively, which can be designed as a novel “turn-on” fluorescence sensor of L-Cys. The study of fluorescence performance indicates that in the range of 0–25 µM for L-Cys, the variation of the proposed approach exhibits a good linear relationship with corresponding detection limits of 0.892 µM.