A Zn-based metal–organic framework as bifunctional chemosensor for the detection of nitrobenzene and Fe3+

In this report, three metal-organic frameworks (MOFs) were synthesized by hydrothermal reactions with 4,4′,4″-nitrilotribenzoic acid (H3NTB), 1,10-phenanthroline (phen) and water by introducing Zn(Ⅱ), Mn(Ⅱ) and Cu(Ⅱ) center ions, namely, [Zn(HNTB)(phen)]n (Ⅰ), [Mn(HNTB)(phen)•H2O]n (Ⅱ) and {[Cu(HNTB)(phen)•H2O]•H2O}n (Ⅲ). Single-crystal X-ray diffraction data analyses demonstrate that Ⅰ-Ⅲ are assembled into three-dimensional frameworks based on the building blocks of {ZnO4N2}, {MnO3N2} and {CuO4N2} through the connections of HNTB2−, intermolecular hydrogen bonds and the π … π interactions between pyridine rings, respectively. The fluorescent properties of Ⅰ-Ⅲ have been systematically studied in different solutions containing certain metal ions and organic molecules. As a result, Zn-MOF (I) exhibits a dual-responsive fluorescent sensor toward nitrobenzene (NB) and Fe3+ with high selectivity, stability and anti-interference ability at the existence of other corresponding analytes originating from its excellent fluorescent quenching efficiency. Moreover, the possible sensing mechanisms for the above analytes have also been elucidated, which are testified by PXRD analysis, ICP-AES, UV–vis spectra, XPS and the density functional theory (DFT).