Regenerable Luminescent Triarylborane Lanthanide Metal–Organic Frameworks as Solid-State Sensors

Fluoride anions (F–) are commonly found in everyday items and are known to have positive medicinal uses. Despite their importance, overconsumption can lead to dental and skeletal fluorosis, among 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 F–, while also providing steric bulk to enhance the selectivity and stability of the LnBMOFs. We further demonstrate that LnBMOFs are capable of sensing other small anions including CN– and OH– but also a wider scope of anions including PO43–, SO42–, NO3–, and Cl–, while maintaining a high degree of sensitivity. The structural design of these LnBMOFs provides a turn-on/off effect with some anions, where the luminescence is regenerated and maintains stability through several cycles upon washing with water.