Thiophene-incorporated CTFs with boosted intramolecular charge transfer and defect-abundant networks for potent photosensitized oxidation of organics

Abstract

Simultaneously modulating the adsorption and electronic properties of pure conjugated polymers for efficient photosensitized oxidation of organics is environmentally desirable but still challenging. Of interest to us in this work was to construct artificial defective donor-sensitizer-acceptor covalent triazine framework (CTF) and probe how the transformation of barely active pure polymers into high-efficiency photosensitizer occurred. The thiophene/cyano (–Th/–CN) donor–acceptor (D–A) configurations in the structural terminations were facilely formed by incorporating thiophene units into CTF (denoted as CTF-xTh), which simultaneously induced plenty of defect sites spread over the polymer networks. Experimental and theoretical studies revealed that the incorporated D–A dyads could serve as charge delivery channels for intramolecular charge transfer transition and render the photogenerated charges spatially delocalized at the –Th/–CN terminated edge sites, which impels the proceeding of photoactivation reaction with oxyanions (represented by HSO5−). Moreover, the edge defects could serve as high-energy adsorption sites for enriching organics (represented by bisphenol-A (BPA)), which enables the generated reactive species to be in close proximity to contaminants to have greater chances of attacking these molecules. With these merits, a 4-fold enhancement of HSO5− conversion and a 10-fold improvement of BPA adsorption were found in Vis/ HSO5−/CTF-5Th system as compared with corresponding pristine CTF system, and thus the overall BPA removal increased by 8 times. This work demonstrated the first instance of using D-A tailored CTF for photosensitized oxidation of organics and provided new opportunities toward designing of novel polymers for visible-light-driven photocatalysis.