Dual-ligand Eu-MOF for ratiometric fluorescence sensing and visual detection of fluoride ions

Abstract

An excess of fluoride ions (F⁻) can contribute to environmental pollution and can pose risks to human health. Hence, establishing an affordable, fast, and effective approach is crucial for detecting F⁻. Herein, we constructed a dual-emission Eu-AIP/BDC MOF through a dual-ligand strategy using 5-amino isophthalic acid (5-AIP) and terephthalic acid (H₂BDC) as ligands and Eu³⁺ ions as metal nodes. 5-AIP retained its own emission at 406 nm and its amino group was utilized to response F⁻ ions; BDC was employed to sensitize Eu³⁺ ions through the antenna effect procedure for the emission at 616 nm. Consequently, Eu-AIP/BDC MOF exhibited dual-emission under single excitation at 280 nm. F⁻ ions enhanced the emission at 406 nm and quenched the emission at 616 nm, enabling the ratiometric fluorescence detection of F⁻ ions with a detection limit of 0.326 μM. The intensity changes of the two emissions resulted in obvious color changes for the visual detection of F⁻ ions. The successful detection of F⁻ in real samples (e.g., toothpaste and water) validated the probe's practicality for on-site environmental and biomedical applications. Thus, we demonstrated an efficient dual-ligand strategy to accomplish dual-emission and thus identify targets within single MOFs for both ratiometric sensing and visual detection application with improved performance.