Eu³⁺-Doped Mixed-Ligand UiO-66-Type Metal-Organic Framework for Ratiometric Fluorescence Sensing Fluoride Ions with...

Metal-organic frameworks (MOFs) have emerged as a highly promising platform for various sensing applications due to their tunable structures and functionalities. In the present work, a Eu³⁺-doped mixed-ligand MOF, namely, the Eu³⁺@UiO-66-IPA, exhibited excellent luminescent properties and high fluorescence stability in aqueous media, displaying dual-emission peaks under 395 and 615 nm excitation that were readily visible to the naked eye. Importantly, the presence of fluoride ions (F^-) promoted the "antenna effect" between the ligand and the Eu³⁺ centers, which significantly enhanced the emission intensity of the Eu³⁺ characteristic peak. In addition, the addition of F^- also inhibited the quenching effect of high-energy O-H bonds existing in the aqueous environment. Notably, Eu³⁺@UiO-66-IPA demonstrated exceptional selectivity for F^- over a range of competing anions, with a remarkable limit of detection as low as 0.22 μM. The developed Eu³⁺-doped mixed-ligand MOF system offers a highly promising strategy for the simple and accurate sensing of F^- in practical applications.