A multi-responsive carbazole-functionalized Zr(IV)-based metal-organic framework for selective sensing of Fe(III), cyanide and p -nitrophenol

A new, luminescent Zr(IV)-based metal-organic framework (MOF) material (1) having UiO-67 framework topology and incorporating 9H-carbazole-2,7-dicarboxylic acid (2,7-H2CDC) as ligand was synthesized under solvothermal conditions. The phase-purity of the material was examined by X-ray powder diffraction (XRPD) analysis, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric (TG) and elemental analysis. Thermogravimetric analysis indicates that the compound is thermally stable up to 250 °C. According to the fluorescence titration experiments, the activated compound (1′) displays highly selective and sensitive detection behavior towards Fe3+ and CN− ions as well as p-nitrophenol (PNP) even in the presence of relevant potentially competing analytes. Recyclability experiments suggest that 1′ is highly photostable and reusable for the sensing of Fe3+ ions and PNP. The change in the fluorescence intensity of 1′ in presence of Fe3+ (turn-off) and CN− (turn-on) ions might be attributed to electron transfer and deprotonation processes, respectively. Furthermore, the luminescence turn-off property of 1′ in the existence of PNP can be assigned to both energy and electron transfer processes as well as electrostatic interactions of the MOF compound with PNP. Owing to its excellent detection performance, 1′ is a potential fluorescent sensor material for the long-term, real-field sensing of Fe3+, CN− and PNP.