A multi-responsive pH stable-MOF for prevalent Hg(i), Hg(ii) and organochlorine pesticide detection

Abstract

The development of water-stable multipurpose sensory materials is of urgent need for the rapid and selective detection of toxic mercury ions and organochlorine pesticides in aqueous media. Although many sensor materials have been developed for Hg²⁺ detection, reports on Hg₂²⁺ detection are relatively scarce. On the other hand, the development of a multipurpose material capable of efficiently detecting toxic analytes—Hg₂²⁺, Hg²⁺ and organochlorine pesticides—within a single platform has remained largely unexplored, particularly from economic and practical perspectives. Herein, we have developed a chemically stable Co-MOF, named MOF: IITKGP-80, for the selective detection of mercury ions and toxic organochlorine pesticides (like 2,6-dichloro-4-nitroaniline, DCN) by a mixed-ligand synthesis approach with two judiciously chosen sulphur-rich ligands. The resulting MOF structure is highly water stable and stable over a wide pH range (2–12) and is enriched with exposed S-sites, conferring the distinct advantages of soft donor capability to the softer metal ions by effectively mimicking the sulphur-containing amino acids (like cystine or methionine) for the selective interaction with Hg-ions over other metal ions. Along with the outstanding aqueous medium-sensing ability of mercury ions, MOF: IITKGP-80 also showed excellent detection performance for the toxic organochlorine pesticide, DCN. Both energy and electron-transfer mechanisms are proven responsible for the observed fluorescence quenching of the MOF by DCN, as evidenced by quantum-chemical insights. The superior sensitivity, excellent LOD, and exceptional recyclability make this chemically stable MOF stand out as a promising solution for safeguarding ecosystems from the hazardous effects of mercury ions and pesticides.