Density Functional Theory Study in Photocatalytic Water Splitting via Covalent Triazine Frameworks Functioned by Benzothiophene Sulfone

Photocatalytic overall water splitting (PWS) offers a green, economical, and sustainable pathway for hydrogen production. However, the efficiency is still hindered by severe charge recombination in catalysts, high energy barriers for water oxidation, and sluggish reaction kinetics. Therefore, it is crucial to address these challenges by enhancing charge separation efficiency, accelerating reaction kinetics, and lowering PWS energy barriers. In this work, we constructed donor–acceptor covalent triazine-based organic frameworks (CTFs), such as CTF-BP, CTF-DBT, and CTF-DBTS, using biphenyl (BP), benzothiophene (DBT), and benzothiophene sulfone (DBTS) as basic units, respectively. DFT calculations revealed that all three CTFs exhibit comparable bandgaps with strong visible-light absorption. Notably, strong dipole moments between donor and acceptor units were observed within these frameworks, effectively promoting in-plane charge separation. DBT and DBTS derivatives generated stronger dipole moments compared to biphenyl. Furthermore, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) pathway analyses demonstrated that CTF-DBTS substantially reduces energy barriers for both half-reactions relative to CTF-DBT and CTF-BP, exhibiting the most promising potential for PWS. This work provides a reference for the application of DBTS-incorporated COFs in PWS systems.