π‐Electronic Effects Dictate Interlayer Charge Transfer in Covalent Organic Frameworks With Boosted Photocatalytic Activity

ABSTRACT Understanding interlayer charge transfer is central to the rational design of two‐dimensional (2D) covalent organic frameworks (COFs) for high‐performance photocatalysis. Herein, we successfully modulate the interlayer charge transfer in donor–imine–donor type COFs by regulating the π‐electronic character of knots and linkers. We demonstrate that the rigid pyrene‐based knot with profound π‐electronic effect promotes efficient interlayer charge transfer, whereas the twisted biphenyl‐based counterpart effectively inhibits it combining with experimental and theoretical calculations. Specifically, the pyrene‐based units endow enhanced conjugation, improved planarity, and strengthened π–π stacking, giving rise to a substantially larger interlayer charge transfer amount for the fully rigid R–R–COF compared with the twisted T–T–COF. Consequently, R–R–COF achieves a superior H 2 evolution rate of 80.6 mmol g −1 h −1 , 89.6 times that of T–T–COF (0.9 mmol g −1 h −1 ) under identical conditions. Additionally, we reveal that topological selectivity correlates closely with the electronic nature of the knot. This work establishes π‐electronic effect as a key determinant of both interlayer charge transfer efficiency and photocatalytic activity, and provides a rational design strategy for advanced COF‐based photocatalysts.