Dual-Emissive Metal–Organic Framework as aFluorescent “Switch” for Ratiometric Sensing of Hypochloriteand Ascorbic Acid

The detection of hypochlorite (ClO–) content in tap water is extremely important because excess amounts of hypochlorite can convert into highly toxic species and inadequate amounts of hypochlorite cannot fully kill bacteria and viruses. Although several metal–organic frameworks (MOFs) have been successfully employed as fluorescent sensors for hypochlorite detection, all these sensors are based on single emission that responds to the dose of hypochlorite. Ratiometric sensors are highly desirable, which can improve the sensitivity, accuracy, and reliability via self-calibration. Herein, a nanoscale dual-emission multivariate 5-5-Eu/BPyDC@MOF-253-NH2 was synthesized by sequential mixed-ligand self-assembly and postsynthesis method. Among the two emission bands of 5-5-Eu/BPyDC@MOF-253-NH2, the strong blue emitting derived from ligands is sensitive to hypochlorite, while the red emitting derived from Eu(III) almost keeps invariable. Therefore, 5-5-Eu/BPyDC@MOF-253-NH2 was exploited as a fluorescent ratiometric...