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

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 {[EuxTb2-x(BIPA)3(DMF)(H2O)3]<middle dot>2DMF<middle dot>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. The colorimetric visual detection of fluoride ions in river was realized through weak double dynamic interactions between mixed lanthanide-organic framework and fluoride ions.