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

Abstract

The 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.

Metal–Organic Framework-Based Fluorescent Sensors for the Detection of Pharmaceutically Active Compounds

“…These attributes render MOFs as exceptional luminescent materials. The enduring porosity and cooperative luminescent characteristics intrinsic to MOFs offer significant utility in developing luminescent sensing materials tailored for the recognition of certain analytes. , The strategic selection of the metal ions and precise modulation of functional groups within MOFs hold the key to unlocking distinctive properties that amplify their ability to detect targeted analytes. Many luminescent MOFs have demonstrated their efficacy in diverse applications such as sensing of various antibiotics, drugs, volatile organic compounds, nitro explosives, toxic heavy metals, carcinogenic anions, organotoxins, pesticides, biomolecules, and bioimaging. − Several factors, such as the presence of metal nodes and highly conjugated organic spacers, cause the appearance of fluorescence property in MOFs (often noticeable in lanthanide-based MOFs due to the antenna effect).…”

The {Cu2I2} cluster bearing metal organic frameworks: crystal structures and fluorescence detecting performances towards cysteine and explosive molecules

“…[1][2][3][4][5] Fluorescent (FL) MOFs have been well investigated and widely explored in varied applications. [6][7][8][9] Notably, the fluorescence in MOFs could arise from metal ions, organic linkers, guest molecules, and the energy transfer between metal ions and organic ligands (MLCT or LMCT). 10 Therefore, exploring FL MOFs with new structural features and novel FL centers is of great importance to enrich the family of MOFs and provide new emission mechanisms for the future design of FL MOFs aiming for specific applications.…”

pH-Stable Zn(II) Coordination Polymer as a Multiresponsive Turn-On and Turn-Off Fluorescent Sensor for Aqueous Medium Detection of Al(III) and Cr(VI) Oxo-Anions

“…In this context, coordination polymers (CPs) and/or metal–organic frameworks (MOFs) are attracting immense interest due to their intriguing properties, such as an accessible high surface area, ordered crystalline structure, permanent porosity, functional tunability, structural diversity, unique flexibility, and variable morphologies. − In particular, owing to the presence of well-organized chromophores (Lewis acid and basic sites) in their chemically tailorable framework, CPs/MOFs exhibit excellent luminescent properties. ,, Such superior properties make them fascinating as an effective sensing probe for the detection of variable analytes including toxic metal ions, hazardous anions, explosives, antibiotics, pesticides, and small organic molecules. ,,− Moreover, the specific host–guest interactions between the incoming analytes and the accessible functional groups of the framework bring more advantages in terms of easy operability, fast responsivity, high selectivity, good sensitivity, and multiple recyclabilities . − Taking advantage of such superiorities, although a large number of CPs/MOFs have been explored for the rapid detection of toxic metal cations and noxious oxo-anions individually or combinedly having turn-off luminescence only, ,,,, multiresponsive behavior with one turn-off and another turn-on luminescent detection by a single CP/MOF platform remains unexplored so far. Compared to single-analyte recognition, frameworks showing simultaneous and rapid sensing for multiple analytes are highly desirable and on-demand as they can increase the versatility and multipurpose usage possibility of the developed sensory materials. ,− On the other hand, although a decent number of coordination frameworks have displayed excellent luminescent performance with high sensitivity and selectivity, their insufficient hydrolytic stability, as well as chemical instability, , forced them to detect targeted analytes in a nonaqueous medium. , However, to make the developed framework affordable and easy to handle, it is desirable to develop robust sensor materials that ca...…”