Enhancing photocatalytic efficiency through surface modification to manipulate internal electron-hole distribution

Abstract

In this study, we synthesized ten g-C₃N₄-based covalent organic frameworks (COFs) and identified CN-306 as the most effective catalyst for visible-light-driven hydrogen peroxide (H₂O₂) production. Systematic optimization revealed that increasing ethanol proportions in the reaction medium significantly enhanced H₂O₂ yield, achieving a remarkable production rate of 5352 μmol g⁻¹h⁻¹ with a surface quantum efficiency of 7.27% at λ = 420 nm. Intriguingly, mechanistic investigations uncovered that excessive generation of singlet oxygen (¹O₂) acts as a critical inhibitory factor, impeding H₂O₂ accumulation. Multimodal characterization techniques combined with density functional theory (DFT) calculations were employed to unravel the origin of CN-306’s superior performance. Theoretical analyses demonstrated that CN-306 exhibits enhanced electron-hole separation efficiency, attributed to its reduced energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), which facilitates photocarrier migration and suppresses detrimental recombination. Furthermore, this work elucidates the structure-function relationships governing site-specific functional group modifications in COFs and their profound influence on photocatalytic activity. These findings provide molecular-level insights into rational catalyst design for optimizing surface structures and advancing solar-driven H₂O₂ synthesis applications.