Photocatalytic hydrogen production by donor-π-acceptor type covalent triazine frameworks involving different π bridges

Covalent triazine frameworks (CTFs) involving donor-pi bridge-acceptor (D-pi-A) motifs with the electron-withdrawing triazine unit as the acceptor have been regarded as one of the most promising materials for photocatalytic water splitting. The intrinsic features of pi-bridges play a critical role in tailoring the polymer properties as well as the photocatalytic performance. Introducing suitable conjugated units as the pi-bridge is expected to effectively tune the electronic structure of the resultant D-pi-A CTFs and facilitate photo-generated charge separation. However, systematic studies on how different pi-bridges would influence the photoelectronic properties of D-pi-A type CTFs are still limited. Herein, three types of CTFs with well-defined D-pi-A structures named Ben-CTF, BenT-CTF and BenP-CTF were synthesized to investigate the effects of different pi-bridges (benzene, thiophene and pyridine units) on the performance of photocatalytic water splitting for hydrogen production. Comprehensive experiments and density functional theory (DFT) calculations revealed that BenP-CTF with the pyridine unit as the pi-bridge exhibited superior charge migration ability and higher photocatalytic hydrogen evolution reaction (HER) rates compared to the other CTFs. This work may provide a reference for the rational design and controllable synthesis of CTF materials for efficient photocatalysis. A novel pyridine-bridged covalent triazine framework (CTF), BenP-CTF, exhibited much higher photocatalytic activity for water splitting to hydrogen than benzene-bridged Ben-CTF and thiophene-bridged BenT-CTF due to enhanced built-in electric field.

Automated summary

This study investigated the effects of different pi-bridges on the performance of photocatalytic water splitting by synthesizing three types of CTFs. The results showed that BenP-CTF with the pyridine unit as the pi-bridge exhibited superior charge migration ability and higher photocatalytic hydrogen evolution rates compared to the other CTFs.