Metal–Organic Framework with Near-Infrared Luminescence for “Switch-on” Determination of Kaempferol and Quercetin by the Antenna Effect

The establishment of a reliable and sensitive method
for the detection
of flavonoids, such as kaempferol (Kae) and quercetin (Que), is important
and challenging in food chemistry and pharmacology because numerous
structural analogues may interfere with the detection. Until now,
designing an efficient switch-on fluorescence sensing strategy for
Kae and Que was still in the unachievable stage. In this work, a switch-on
near-infrared (NIR) luminescence sensing assay for Kae and Que was
fabricated based on a metal–organic framework (MOF) called
IQBA-Yb for the first time. The fluorescence enhancing mechanism was
that analytes served as additional “antenna” of Yb3+, leading to the efficient switch-on NIR emission under excitation
at 467 nm. Meanwhile, the combination results of experiment and theoretical
calculation revealed that there existed hydrogen bonds between Kae,
Que, and the MOF skeleton, further promoting the energy transfer between
the analyte and Yb3+ and facilitating fluorescence enhancement
response. The developed probe possessed excellent sensing capability
for Kae and Que, accompanied by a wide linear range (0.04–70,
0.06–90 μM), low detection limit (0.01, 0.06 μM),
and short response time (20 min, 6 min), which was used to determine
the Kae and Que contents in Green Lake and eatable Que samples with
satisfactory results.