Photocarrier\nDynamics of Two-Dimensional Aza-Fused\nCovalent Organic Frameworks as Bifunctional Photocatalysts toward\nOverall Water Splitting

Designing\nhigh-efficiency bifunctional photocatalysts toward photoinduced\noverall water splitting is one of the most promising and challenging\nresearch directions for clean energy generation. By employing static\nelectronic structure calculation and nonadiabatic molecular dynamics\n(NAMD) simulation, we herein established a recently synthesized two-dimensional\n(2D) aza-fused covalent organic framework (aza-COF) as a potential\nbifunctional photocatalyst toward overall water splitting reactions.\nOur calculated results reveal that the overpotentials for hydrogen\nevolution reaction and oxygen evolution reaction are only 0.06 and\n0.31 V, respectively, at pH = 4. The dynamics of photoexcited charge\ncarriers studied through NAMD simulation predicts the electron–hole\nrecombination time (25.15 ns), and this confirms that the photogenerated\nelectron and hole carriers migrate to the active sites for the occurrence\nof reaction before they recombine. Therefore, our results suggest\nthat the 2D aza-COFs exhibit great potential as metal-free and single-material\nphotocatalysts toward overall water splitting under visible light.