A Salen-based covalent organic polymer as highly selective and sensitive fluorescent sensor for detection of Al.sup.3+, Fe.sup.3+ and Cu.sup.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 .sup.13C 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.sup.3+, while the obtained polymer also exhibited the dramatic fluorescence quenching for the sensing of Fe.sup.3+ and Cu.sup.2+. The detection limits were calculated to be 0.248 [micro]M for Salen-COP@Al.sup.3+, 0.545 [micro]M for Salen-COP@Fe.sup.3+ and 0.140 [micro]M for Salen-COP@Cu.sup.2+, respectively. Furthermore, the Salen-COP was founded to be a reversible chemosensor for Al.sup.3+, Fe.sup.3+ and Cu.sup.2+ ions, which provided a unique opportunity in the development of multi-response polymer-based sensors.