Tetraphenylethylene-based covalent organic frameworks as fluorescent chemosensor for rapid sensitive recognition and selective turn-on fluorescence detection of trace-level Al3- ion

Tetraphenylethylene-based covalent organic framework (COF-DHTA) was prepared and then well characterized. COF-DHTA processes regular pore structure and high thermal stability. COF-DHTA suspension in DMF displays moderate fluorescence emission in DMF suspension and a highly selective fluorescence turn-on response towards Al3+ ions. The fluorescence intensity of COF-DHTA suspension at the emission peak 352 nm exhibits a good linear relationship with the concentration of the added Al3+ ions with a very low detection limit of 0.927 mu mol/L. The selective and sensitive fluorescence enhancement recognition and detection for Al3+ ions can be attributed to the coordination of Al3+ ions with N and O atoms on the COF-DHTA and the suppression of photoinduced electron transfer (PET). The results of the N-2 adsorption experiment, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculation verified the coordination interaction between Al3+ ion and the N and O chelating sites on COF-DHTA. This work may pave the way to reasonable design fluorescent COF chemosensors for the recognition and detection of specific metal ions.

Automated summary

COF-DHTA shows moderate fluorescence emission and a highly selective fluorescence turn-on response towards Al3+ ions in DMF suspension. The coordination of Al3+ ions with N and O atoms on COF-DHTA and the suppression of PET contribute to the selective and sensitive fluorescence enhancement recognition and detection. This work may lead to the design of fluorescent COF chemosensors for specific metal ion recognition and detection.