Regenerable Luminescent Triarylborane-Functionalized Rare-Earth Metal-Organic Frameworks as Solid-State Small Molecule Sensors

Abstract: Fluoride anions (F-) are commonly found in everyday items and known to have positive medicinal uses. Despite their importance, overconsumption can lead to dental and skeletal fluorosis, amongst other health issues. In pursuit of a more effective method to detect trace amounts of anions in aqueous media, we synthesized two triarylborane-functionalized lanthanide metal-organic frameworks (LnBMOFs) to act as solid-state luminescent sensors. The LnBMOFs, EuBMOF and TbBMOF use europium and terbium, respectively as these metal ions display strong luminescent properties. The electrophilic nature of the triarylborane ligand makes it an ideal candidate for sensing high affinity fluoride, whilst also providing steric bulk to enhance the selectivity and stability of the LnBMOFs. We further demonstrate that LnBMOFs are capable of sensing other common anions including cyanide and hydroxide, expanding the scope of these sensors, while maintaining a high degree of sensitivity. The structural design of these LnBMOFs provide a turn-on/off effect, where the luminescence is regenerated and maintains stability through several cycles upon washing with water.