A Temperature-Responsive Smart Europium Metal-Organic Framework Switch for Reversible Capture and Release of Intrinsic Eu Ions.

Stimuli-responsive structural transformations are emerging as a scaffold to develop a charming class of smart materials. A metal-organic framework (MOF) undergoes a reversible temperature-stimulated single-crystal to single-crystal transformation, showing a specific behavior of fast capture/release of free Eu in the channels at low and room temperatures. At room temperature, compound is obtained with one free carboxylate group severing as further hook, featuring one-dimensional square channels filled with intrinsic free europium ions. Trigged by lowering the ambient temperature, is gained. In , the intrinsic free europium ions can be fast captured by the carboxylate-hooks anchored in the framework, resulting in the structural change and its channel distortion. To the best of our knowledge, this is the first report of such a rapid and reversible switch stemming from dynamic control between noncovalent and covalent Eu-ligand interactions. Utilizing MOF to detect highly explosive 2,4,6-trinitrophenol at room temperature and low temperature provides a glimpse into the potential of this material in fluorescence sensors.