Vaporesponsive Lanthanide Metal-Organic Frameworks as Selective Luminescent Spin Quantum Sensors for Biogenic Amines

Detecting biogenic amines (BAs) is a topic of particular interest for future technological applications of metal-organic frameworks (MOFs) in food quality control. Herein, we demonstrate that integrating lanthanide single-ion magnets (SIMs) into MOFs offers a convenient route for developing a new class of luminescent spin quantum sensors for BA sensing, termed Ln SIM-MOFs. This study focuses on the well-known family of lanthanide(III) sesquioxalate hydrates of general formula {[Ln^III₂(ox)₃(H₂O)₆]·xH₂O}_n, which feature a 2D hexagonal layer structure. Upon selective adsorption of methylamine over di- or trimethylamine vapors, these compounds exhibit either a partial quenching of the luminescence [Ln = Eu 1a (x = 3) and Tb 2a (x = 3)] or a dramatic change of the spin dynamics from a slower to a faster relaxing phase [Ln = Er 3a (x = 2.5)]. The dual luminescent and magnetic vaposwitching behavior observed in this series of dynamic Ln SIM-MOFs offers new design principles to obtain multifunctional and multiresponsive molecular materials for the chemical sensing of volatile organic compounds (VOCs), resulting from industrial procedures or food degradation.