Luminescent metal organic frameworks–based chemiluminescence resonance energy transfer platform for turn–on detection of fluoride ion

A luminescent metal organic frameworks (MOFs)–based chemiluminescence resonance energy transfer (CRET) platform was constructed for turn–on detection of fluoride ion. A hybrid MOFs was prepared by encapsulating strong fluorescence 2′,7′–dichlorofluorescein (DCF) into the frames of NH₂–MIL–101(Al) MOFs, which led to a significant suppression of fluorescence signal of DCF. In the presence of fluoride ion, it destroyed the structure of the hybrid MOFs and released DCF molecules from the frames due to the formation of more stable aluminum hexafluoride complex ions [AlF₆ ³⁻] between fluoride ion and aluminum ion. The released DCF molecules accepted the energy originating from the chemical reaction of bis(2,4,6–trichlorophenyl)oxalate (TCPO) with hydrogen peroxide (H₂O₂), producing a strong chemiluminescence (CL) emission. The CL signal was strong dependent on the concentration of fluoride ion presented and showed a linear response in the range of 0.5–80.0 μmol L⁻¹ (9.5 μg L⁻¹–1.52 mg L⁻¹). The detection limit was 0.05 μmol L⁻¹ (about 0.95 μg L⁻¹) fluoride ion and the relative standard deviations was 2.3% for 40.0 μmol L⁻¹ fluoride ion solution (n = 11). This MOFs–based CRET method was successfully applied to the determination of fluoride ion in drinking water samples, demonstrating its potential application in analysis of real samples.