Dynamic Covalent Cage: A Selective and Robust Fluorescence Sensor for Copper Ion Detection in Aqueous Solutions

The development of advanced sensing systems for the selective detection of metal ions, such as copper (Cu 2+ ), is a pressing challenge in modern analytical and environmental chemistry due to their dual role as essential elements in biological systems and potential toxins at elevated concentrations. Herein, a novel fluorescent organic cage based on a triphenylamine (TPA) chromophore is introduced, designed specifically for the detection of Cu 2+ ions in water. The design concept involves the incorporation of two dynamic covalent bonds: acylhydrazone and disulfide, within a single cage structure, imparting adaptability and exceptional sensing performance. This cage demonstrates a distinct “turn‐off” fluorescence response, with a pronounced signal decrease upon Cu 2+ binding, offering reliable and accurate quantitative detection. Additionally, the system provides qualitative, visible colorimetric responsivity, enabling straightforward, visual detection without the need for advanced instrumentation. Its high selectivity toward Cu 2+ , combined with a low detection limit of 4.75 μM, ensures precise analysis even in the presence of competing metal ions. Practical applicability is demonstrated through the successful detection of Cu 2+ in real water samples, highlighting the system's potential for environmental monitoring and field application.