Stable Ln-MOFs as multi-responsive photoluminescence sensors for sensitively sensing Fe3+, Cr2O72-, and nitrofuran

Two families of lanthanide(III) metal-organic frameworks (Ln-MOFs) constructed from 2-(4-pyridyl)-terephthalic acid (H2pta) ligand, namely [Ln4(pta)5(Hpta)2(H2O)4]·xH2O (1-Eu, 2-Gd), [Ln(Hpta)(C2O4)]·3H2O (3-Tb, 4-Dy, 5-Er and 6-Ho) (C2O4 = oxalic acid), have been discovered by solvothermal method. On the basis of thermodiffractometry, all MOFs remain their crystallinity and main structure below 370 °C. Utilizing their excellent water stability and chemical stability, the luminescence studies have been carried out. Notably, Eu-MOF and Tb-MOF are indicative of pronounced luminescence, as well as high stability in water and other organic solvents. The luminescence explorations reveal that Eu-MOF possesses good selectivity for testing Fe3+ in aqueous phase via fluorescence quenching, while Tb-MOF behaves as a multifunctional chemical sensor for the detections of Fe3+ cation and Cr2O72- anion in aqueous media and the recognition of nitrofuran (NIF) in DMF solvent. The recyclability and stability of Eu-MOF and Tb-MOF after sensing experiments are observed to be adequate. By virtue of the superior stability, detection efficiency, applicability and reusability, Eu-MOF and Tb-MOF can be the promising fluorescent materials for practical sensing.