Dual-Ligand Eu-MOF for Ratiometric Fluorescence Sensing and Visual Detection of Fluoride Ions

Abstract

Excess of fluoride ions (F⁻) can contribute to environmental pollution and pose risks to human health, so establishing an affordable, fast, and effective approach becomes crucial for detecting F⁻. Here we constructed a dual-emission Eu-AIP/BDC MOF through a dual-ligand strategy with 5-amino isophthalic acid (5-AIP) and terephthalic acid (H2BDC) as the ligands, while Eu3+ ions are employed as the metal nodes. 5-AIP retained its own emission at 406 nm and was utilized to response F− ions with the amino groups; 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, while quenching the emission at 616 nm, allowing ratiometric fluorescence detection of F− with the detection limit of 0.326 μM. The intensity changes of the two emissions resulted in obvious color changes for visual detection of F− ions. The successful detection of F⁻ in real samples (e.g., toothpaste and water) validates the probe’s practicality for on-site environmental and biomedical applications. Thus, we exhibited the efficiency using dual-ligand strategy to accomplish dual-emission and thus identification of targets within single MOFs for both ratiometric sensing and visual detection application with the improved performance.