Stable Ln-MOFs as multi-responsive photoluminescence sensors for the sensitive sensing of Fe3+, Cr2O72−, and nitrofuran

Abstract

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