Coumarin-embedded MOF UiO-66 as a selective and sensitive fluorescent sensor for the recognition and detection of Fe3+ ions

Abstract

A fluorescent composite, HCAA@UiO-66, was prepared by encapsulating fluorescent 7-hydroxycoumarin-4-acetic acid (HCAA) molecules in the pores of a metal–organic framework (MOF, UiO-66). The encapsulation of HCAA in the pores of UiO-66 does not affect its crystalline and porous structure. HCAA@UiO-66 in ethanol displays a strong fluorescence emission and a highly selective fluorescence response towards Fe³⁺ ions. The fluorescence intensity of HCAA@UiO-66 at 451 nm shows a satisfactory linear relationship with the concentration of Fe³⁺ ions in a wide range of 0–400 μmol L⁻¹ with a low detection limit (LOD) of 4.87 × 10⁻⁶ mol L⁻¹. The fluorescence quenching is attributed to the interaction of Fe³⁺ ions with HCAA@UiO-66 and the absorption competition quenching (ACQ). HCAA@UiO-66 proved that the encapsulation of fluorescent dyes in the MOF is an efficient approach to fabricate fluorescent chemosensors for the determination of metal ions.