Abstract
Environmental issue related applications have globally surfaced as hottest areas of research, wherein luminescent metal-organic frameworks (LMOFs) with functionalized pores put unique signature in real-time monitoring of multiple classes of toxic compounds, and overcome many of the challenges of conventional materials. We report a two-fold interpenetrated, mixed-ligand Cd(II)-organic framework (CSMCRI-11) [Cd1.5(L)2(bpy)(NO3)]·DMF·2H2O (CSMCRI = Central Salt and Marine Chemical Research Institute, HL = 4- (1H-imidazol-1-yl)benzoic acid, bpy = 4,4′-bipyridine) that exemplifies bipillar-layer structure with two different Cd(II) nodes, and displays notable robustness in diverse organic solvents and water. Intense luminescence signature of the activated MOF (11a) is harnessed in extremely selective and fast responsive sensing of Fe3+ ions in aqueous phase with notable quenching constant (1.91 × 104 M−1) and impressive 166 ppb limit of detection (LOD). The framework further serves as a highly discriminative and quick responsive scaffold for turn-off detection of two noxious oxo-anions (Cr2O7 2− and CrO4 2−) in water, where individual quenching constants (CrO4 2−: 1.46 × 104 M−1; Cr2O7 2−: 2.18 × 104 M−1) and LOD values (CrO4 2−: 179 ppb; Cr2O7 2−: 114 ppb) rank among best sensory MOFs for aqueous phase detection of Cr(VI) species. It is imperative to stress the outstanding reusability of the MOF towards detection of all these aqueous pollutants, besides their vivid monitoring by colorimetric changes under UV-light. Mechanism of selective quenching is comprehensively investigated in light of absorption of the excitation/emission energy of the host framework by individual studied analyte.
Highlights
Severe pollution of earth’s hydrosphere by detrimental chemicals has raised global concerns to human health and ecological systems. (Samanta et al, 2019; Yao et al, 2020) For instance, Fe3+ ion is one of the vital ions existing in the living organism and plays essential role in transportation of oxygen molecule through blood
We further investigated the hydrolytic stability of the framework by exposing it to saturated water vapours at room temperature
A comparison of metal-organic frameworks (MOFs)-based fluorescence sensors for the detection of lethal oxo-anionic Cr(VI) pollutants in water is tabulated in Supplementary Table S7, which indicates that quenching constants from this study rank one of the best values among existing reports
Summary
Severe pollution of earth’s hydrosphere by detrimental chemicals has raised global concerns to human health and ecological systems. (Samanta et al, 2019; Yao et al, 2020) For instance, Fe3+ ion is one of the vital ions existing in the living organism and plays essential role in transportation of oxygen molecule through blood. (Samanta et al, 2019; Yao et al, 2020) For instance, Fe3+ ion is one of the vital ions existing in the living organism and plays essential role in transportation of oxygen molecule through blood. It has a fundamental role in the formation of haemoglobin, enzyme and proteins. CSMCRI-11 exhibits twofold interpenetrated structure with unidirectional pores This framework shows highly selective and sensitive detection of Fe3+ ion and noxious Cr(VI) oxo-anions (CrO42− and Cr2O72−) at ppb level in the aqueous phase. Fast responsive time and excellent sensitivity along with very low limit of detection render this framework one of the best LMOFs among contemporary reports, and promises its utilization as smart material for detection of hazardous contaminants in the aqueous phase
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