Trefoil-Shaped Metal-Organic Cages as Fluorescent Chemosensors for Multiple Detection of Fe3+, Cr2O72-, and Antibiotics.

The construction of metal-organic cages (MOCs) with specific structures and fluorescence sensing properties is of much importance and challenging. Herein, a novel phenanthroline-based metal-organic cage, [Cd3L3·6MeOH·6H2O] (1), was synthesized by metal-directed assembly of the ligand 3,3'-[(1E,1'E)-(1,10-phenanthroline-2,9-diyl)bis(ethene-2,1-diyl)]dibenzoic acid (H2L) and CdI2 using a solvothermal method. According to single-crystal X-ray analysis, cage 1 exhibits a rare trefoil-shaped structure. Meanwhile, the discrete MOCs are further stacked into a 3D porous supramolecular structure through abundant intermolecular C-H···O interactions. Additionally, through exploration of fluorescence sensing on cations, anions, and antibiotics in aqueous solution, the experimental results indicate that cage 1 has excellent fluorescence sensing abilities for Fe3+, Cr2O72-, and nitrofuran and nitroimidazole antibiotics. The sensing ability of 1 remains unaltered for five cycles toward all analytes. The above results suggested that cage 1 can be considered a potential multiple sensor for the detection of Fe3+, Cr2O72-, and some antibiotics.