A novel cadmium metal–organic framework-based multiresponsive fluorescent sensor demonstrating outstanding sensitivities and selectivities for detecting NB, Fe3+ ions and Cr2O72− anions

Abstract

A Cd(II) metal–organic framework (MOF) [Cd₃(L)(NTB)₂(DMA)₂]·2DMA (Cd-MOF, DMA = N,N-dimethylacetamide) was solvothermal prepared in the presence of N-donor ligand L (L = (E)-4,4′-(ethene-1,2-diyl)bis[(N-pyridin-3-yl)benzamide]) and O-donor ligand H₃NTB (H₃NTB = 4,4′,4′′-nitrilotribenzoic acid). The Cd-MOF is a 3D framework based on 2D [Cd₃(NTB)₂]_n bilayers and semi-rigid bidentate L ligands, which exhibit a novel 2,3,6-connected network with {8²·10⁸·12·18⁴}{8}₆ topology. Moreover, the Cd-MOF represents the first metal–organic complex assembled by the H₃NTB and bis(amide)-bis(pyridyl) co-ligands and displays remarkable fluorescence and stability as well as fluorescence quenching phenomenon towards Al³⁺, Cu²⁺, Cr³⁺, Fe³⁺ cations, Cr₂O₇²⁻ anion and nitrobenzene (NB). In particular, Cd-MOF can sensitively and selectively detect Fe³⁺, Cr₂O₇²⁻ and NB, and the limit of detection (LOD) values of Fe³⁺, Cr₂O₇²⁻ ions and NB are 5.1 × 10⁻⁵ M, 5.3 × 10⁻⁵ M and 4.2 × 10⁻⁵ M, respectively.