A multi-responsive MOF-based fluorescent probe for detecting Fe3+, Cr2O72− and acetylacetone
A novel Zn2+-based metal–organic framework (MOF) with the formula {[Zn(μ2-η1:η1-BBIP)(μ2-η1:η1:η1-OBA)]·3H2O}n, denoted as JXUST-7, has been successfully assembled using semi-rigid N-donor 3,5-bis(benzimidazol-1-yl)pyridine (BBIP) and flexible 4,4′-oxybisbenzoate (H2OBA). The adjacent Zn2+ ions are linked through an OBA2− ligand with a μ2-η1:η1:η1 bridging mode to form an infinite one-dimensional (1D) Zn2+–OBA2− chain. The neighbouring 1D chains are further connected by a BBIP ligand with a μ2-η1:η1 bridging mode to gain a two-dimensional (2D) sheet layer structure. Topological analysis indicates that the whole 2D structure of JXUST-7 could be simplified as a uninodal sql topology with a point symbol of {44·62}. Furthermore, the opposite parallel 2D layers are further packed by a face-to-face π–π interaction to generate a three-dimensional supramolecular structure. Luminescence experiments reveal that JXUST-7 could be considered as a multi-responsive MOF-based fluorescent probe toward Fe3+, Cr2O72− and acetylacetone (acac) via the fluorescence quenching (turn-off) effect. The detection limits for Fe3+, Cr2O72− and acac are 0.14, 1.33 and 6.53 ppm, respectively. The fluorescence quenching mechanism was analyzed in detail by powder X-ray diffraction, fluorescence lifetime measurement, X-ray photoelectron spectra, theoretical calculation and UV-Vis absorption spectra. More importantly, JXUST-7 could be cyclically utilized at least five times for detecting Fe3+, Cr2O72− and acac.
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