An europium(III) metal-organic framework as a multi-responsive luminescent sensor for highly sensitive and selective detection of 4-nitrophenol and I- and Fe3+ ions in water

A luminescence sensor based on an europium(III)-based lanthanide-organic framework, [Eu(BCB)(DMF)]center dot(DMF)(1.5)(H2O)(2) (1), was synthesized via a solvothermal method using 4,4',4 ''-benzenetricarbonyltribenzoic acid (H3BCB) as a bridging ligand. Single-crystal X-ray diffraction indicates that Eu centers are eight-coordinated with a trigonal dodecahedron and a square antiprismatic configuration, and adjacent Eu atoms are bridged by BCB organic linkers to form a 3D rod-packing structure. Photoluminescence studies show that compound 1 emits bright red luminescence and behaves as a multi-responsive luminescent sensor toward 4-nitrophenol (4-NP) and I- and Fe3+ ions in water with high sensitivity, selectivity and low detection limits. Furthermore, the possible luminescence sensing mechanisms were also investigated by PXRD analysis, UV-vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The recognition mechanism for 4-NP and I- ions can be attributed to the competition absorption and that for Fe3+ ions is considered to be a multi-quenching mechanism dominated by competition absorption. This study demonstrates that the lanthanide-based MOF might be a promising candidate for the detection of 4-NP and I- and Fe3+ ions in aqueous medium.