Trefoil-Shaped Metal–Organic Cages as Fluorescent Chemosensors for Multiple Detection of Fe³⁺, Cr₂O₇^2–, and Antibiotics

Abstract

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] (<b>1</b>), was synthesized by metal-directed assembly of the ligand 3,3'-[(1<i>E</i>,1'<i>E</i>)-(1,10-phenanthroline-2,9-diyl)bis(ethene-2,1-diyl)]dibenzoic acid (<b>H₂L</b>) and CdI₂ using a solvothermal method. According to single-crystal X-ray analysis, cage <b>1</b> 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 <b>1</b> has excellent fluorescence sensing abilities for Fe³⁺, Cr₂O₇^2-, and nitrofuran and nitroimidazole antibiotics. The sensing ability of <b>1</b> remains unaltered for five cycles toward all analytes. The above results suggested that cage <b>1</b> can be considered a potential multiple sensor for the detection of Fe³⁺, Cr₂O₇^2-, and some antibiotics.