Enhanced luminescence of NH2-UiO-66 for selectively sensing fluoride anion in water medium

Fluoride anion plays an important role in dental health and the treatment of osteoporosis. On the other hand, over exposure to fluoride may lead to severely diseases. Therefore, quantitative analysis of fluoride ions with high specificity and sensitivity by facile and rapid method is in urgent demand. In this paper, an amino-group functionalized MOFs NH2-UiO-66 is synthesized by treating Zr4+ ions and 2-aminaterephthalic acid under hydrothermal condition. A drastic fluorescence enhancement of NH2-UiO-66 at 455 nm induced by fluoride ions is demonstrated. Using NH2-UiO-66 as a receptor, a high selective and sensitive fluorescent detection of F- ions in aqueous solution is achieved. This detection is free from interferences of the co-existing anions and cations, such as Cl-, Br- and I-, NO3-, SO42-, PO43-, CO32-, metal ions and humic acid, etc, for which the allowed amount is up to 1.0 g L−1. The detection limit of F- anion is 0.229 mg L−1. The F- anion-enhanced fluorescent sensing mechanism can be ascribed to the formation of hydrogen bonds between the guest F- anions and the free amino groups in NH2-UiO-66, which result in incremental electron transfer from organic ligands to Zr-oxo clusters. These studies indicate that the luminescent MOF material of NH2-UiO-66 as fluorescent probes may hold promising application in highly selective and sensitive detection of F- anions together with facile receptor fabrication and regeneration.