Unveiling Charge Dynamics in Acetylene-Bridged Donor-π-Acceptor Covalent Triazine Framework for Enhanced Photoredox Catalysis

Covalent triazine frameworks (CTFs) with donor-acceptor motifs have been identified as prospective semiconducting materials for photocatalysis. Though donor-acceptor motifs can favor forward intramolecular charge separation, some cases still suffer from backward charge recombination, resulting in the decrease of the photocatalytic activity. Herein, acetylene-bridged CTFs bearing an extended donor-pi-acceptor motif was fabricated to prompt exciton dissociation. Experimental investigations and density functional theory calculations prove that the acetylene moiety can suppress backward charge recombination, minimize exciton binding energy, and enhance charge carrier lifetime, thereby prompting forward charge transfer/separation in comparison to the analogous one without acetylene. Thus, the acetylene-bridged CTFs showcased a higher photocatalytic activity for metal-free photocatalytic oxidative amines coupling with oxygen under visible-light irradiation, and apparent quantum efficiency at 420 nm was achieved up to 32.3%, that is, twofold higher than the one without acetylene. Furthermore, the acetylene moieties can adsorb oxygen molecules and provide active sites to lower the energy barrier and thus significantly enable the photoredox catalysis. This work provides alternative insights into the design and construction of high-performance CTFs, with prospective applications in solar-to-chemical energy conversion.

Automated summary

The acetylene-bridged CTFs, featuring extended donor-π-acceptor motifs, demonstrated higher photocatalytic activity and achieved a higher apparent quantum efficiency in metal-free oxidative amines coupling reaction under visible-light irradiation. The acetylene moieties also provide active sites to enhance photoredox catalysis, showing the potential for high-performance CTFs in solar-to-chemical energy conversion.