Water-Resistant Fluoro-Switchable MOF and Reconfigurable Bio-Composite for Nanomolar Level Ultra-Fast Monitoring of Organo-Arsenic and Antibiotic Feed-Additives.

A mixed-ligand-based novel 3D Cd(II)-based metal-organic framework (MOF) is devised from π-electron-rich organic struts that shows two-fold interpenetrated bilayer-pillar structure. The strong luminescence of the MOF gets remarkably quenched by roxarsone (ROX) organo-arsenic in water. The material further exemplifies one-of-a-kind fluoro-switchable probe for antibiotics and exhibits massive turn-off emission by tetracycline (TTC), whereas sulfamethazine (SMZ) triggers an unprecedented 120% emission enhancement. Apart from regenerative, fast-responsive, and selective fluoro-detection of all three feed-additives, particularly significant is nanomolar limits of detection (LOD) of ROX (48.9 nm), whereas LOD for SMZ (33.9 nm) ranks lowest, and that of TTC (22.8 nm) stands second lowest among reported sensory MOFs. Besides varying degrees of energy transfer contribution for turn-off detection by ROX and TTC, density functional theory calculations manifest changes in MOF energy levels by individual organo-aromatics and additionally describe framework-analyte supramolecular interactions. The MOF sensor works equally well in different wastewater specimens and a wide pH range with good recovery percentage. To broaden the practical scope of the material, cheap MOF@paper strip as well as reconfigurable MOF@chitosan@paper bio-composite is developed and successfully employed for the instantaneous turn-off detection of ROX and fluoro-switchable monitoring of both the antibiotics at their low concentrations.