Photocarrier Dynamics of Two-Dimensional Aza-Fused Covalent Organic Frameworks as Bifunctional Photocatalysts toward Overall Water Splitting

Designing high-efficiency bifunctional photocatalysts toward photoinduced overall water splitting is one of the most promising and challenging research directions for clean energy generation. By employing static electronic structure calculation and nonadiabatic molecular dynamics (NAMD) simulation, we herein established a recently synthesized two-dimensional (2D) aza-fused covalent organic framework (aza-COF) as a potential bifunctional photocatalyst toward overall water splitting reactions. Our calculated results reveal that the overpotentials for hydrogen evolution reaction and oxygen evolution reaction are only 0.06 and 0.31 V, respectively, at pH = 4. The dynamics of photoexcited charge carriers studied through NAMD simulation predicts the electron-hole recombination time (25.15 ns), and this confirms that the photogenerated electron and hole carriers migrate to the active sites for the occurrence of reaction before they recombine. Therefore, our results suggest that the 2D aza-COFs exhibit great potential as metal-free and single-material photocatalysts toward overall water splitting under visible light.