Synthesis, Structure, and Photoluminescence Properties of a Metal-Organic Framework with Hexagonal Channels: Selective Turn-On Sensing for Mg²⁺ Ion

A three-dimensional Cd²⁺ framework (1) with wide one-dimensional hexagonal channels was prepared based on a tripodal tricarboxylate ligand possessing nitrogen donor atoms. The Cd atoms form a chain structure bridged by carboxylates and aqua ligands. Upon Mg²⁺ ion capture, the fluorescence emission of this porous material was 5.2 times greater than its Mg²⁺-free fluorescence. To the best of our knowledge, such enhancement has not been previously reported for metal–organic framework sensory systems. The sensing performance of 1 is reversible over repeated cycles of Mg²⁺ inclusion and release, revealing the reusability of this material. In the presence of other tested metal ions, Mg²⁺ ions were selectively detected owing to the operation of this “turn-on” mechanism. Thus, this platform is a promising sensor material for selective Mg²⁺ ion recognition.