A Salen-based covalent organic polymer as highly selective and sensitive fluorescent sensor for detection of Al 3+ , Fe 3+ and Cu 2+ ions

A novel covalent organic polymer (Salen-COP) based on Salen-type Schiff base was synthesized by one-pot protocol involving the self-condensation of 3-formyl-4-hydroxyphenylboronic acid and the subsequent aldehyde–amine condensation with benzene-1,2-diamine. The Salen-COP was characterized by 13 C CP/MAS NMR, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and X-ray powder diffraction spectrometry analysis. The morphological features of Salen-COP were also analyzed using scanning electron microscopy. The Salen-COP exhibited the significant fluorescence enhancing for the sensing of Al 3+ , while the obtained polymer also exhibited the dramatic fluorescence quenching for the sensing of Fe 3+ and Cu 2+ . The detection limits were calculated to be 0.248 µM for Salen-COP@Al 3+ , 0.545 µM for Salen-COP@Fe 3+ and 0.140 µM for Salen-COP@Cu 2+ , respectively. Furthermore, the Salen-COP was founded to be a reversible chemosensor for Al 3+ , Fe 3+ and Cu 2+ ions, which provided a unique opportunity in the development of multi-response polymer-based sensors.