A Water‐Stable Cationic SIFSIX MOF for Luminescent Probing of Cr2O72− via Single‐Crystal to Single‐Crystal Transformation

Abstract

AbstractThe sensing and monitoring of toxic oxo‐anion contaminants in water are of significant importance to biological and environmental systems. A rare hydro‐stable SIFSIX metal−organic framework, SiF6@MOF‐1, {[Cu(L)2(H2O)2]·(SiF6)(H2O)}n, with exchangeable SiF62− anion in its pore is strategically designed and synthesized, exhibiting selective detection of toxic Cr2O72− oxo‐anion in an aqueous medium having high sensitivity, selectivity, and recyclability through fluorescence quenching phenomena. More importantly, the recognition and ion exchange mechanism is unveiled through the rarely explored single‐crystal‐to‐single crystal (SC‐SC) fashion with well‐resolved structures. A thorough SC‐SC study with interfering anions (Cl−, F−, I−, NO3−, HCO3−, SO42−, SCN−, IO3−) revealed no such transformations to take place, as per line with quenching studies. Density functional theory calculations revealed that despite a lesser binding affinity, Cr2O72− shows strong orbital mixing and large driving forces for electron transfer than SiF62−, and thus enlightens the fluorescence quenching mechanism. This work inaugurates the usage of a SIFSIX MOF toward sensing application domain under aqueous medium where hydrolytic stability is a prime concern for their plausible implementation as sensor materials.