Fluorescent imine-linked covalent organic framework turn off sensor for sensitive Co²⁺ ions detection

The development of innovative materials capable of detecting heavy metal ions is a crucial goal in the field of environmental remediation. However, achieving high selectivity for specific metal ions remains a challenge. This study designs a novel imine-based COF via Schiff base condensation for efficient detection of cobalt ions (Co²⁺) in environmental samples. The π-conjugation system provides excellent fluorescence properties. The COF contains tertiary amine and imine structures with nitrogen and oxygen atoms, enabling coordination with Co²⁺ as a Lewis base. This interaction disrupts the conjugated structure, causing fluorescence quenching. The experimental results demonstrate that our proposed method stands out in Co²⁺ detection, distinguished by its remarkable simplicity, exceptional sensitivity, rapid response time, and easy operability. The novel imine-based COF sensor exhibits high sensitivity (limit of detection = 8.5 × 10^-13 M), excellent selectivity and stability in fluorescence detection, enabling accurate identification of Co²⁺ in complex environments. This research not only presents an efficient and practical approach for the detection of Co²⁺ but also offers novel theoretical perspectives on the design and application of imine-based COF. The findings lay a solid foundation for the development of COF-based environmental monitoring technologies.