Mixed lanthanide–organic frameworks with borono groups for colorimetric detection of excess fluoride levels in rivers

Abstract

Chronic fluoride (F⁻) toxicity has been endemic at least 25 countries around the world due to prolonged consumption of contaminated water, posing a great threat to human health. Rapid and convenient visual methods for F⁻ ion detection are hence needed for public safety. In this work, we show a series of novel mixed lanthanide–organic frameworks, namely {[Eu_xTb_2−x(BIPA)₃(DMF)(H₂O)₃]·2DMF·3H₂O}_n (H₂BIPA = 5-boronoisophthalic acid; x = 0, 0.12, 0.28, 0.30, 0.68, 1.04 and 2 for 1–7, respectively), with abundant recognition sites of borono groups for convenient and visual detection of excess F⁻ ions in river water. Wide linear range for F⁻ ion detection can be obtained through systematic optimization of sensing materials. A rare double dynamic sensing process between F⁻ ions and lanthanide–organic frameworks was clearly revealed though single-crystal X-ray diffraction and transient fluorescence techniques.