Long‐Range π–π Stacking Brings High Electron Delocalization for Enhanced Photocatalytic Activity in Hydrogen‐Bonded Organic Framework

Unlike many studies that regulate transport and separation behaviour of photogenerated charge carriers through controlling the chemical composite, our work demonstrates this goal can be achieved through simply tuning the molecular π–π packing from short‐range to long‐range within hydrogen‐bonded organic frameworks (HOFs) without altering the building blocks or network topology. Further investigations reveal that the long‐range π–π stacking significantly promotes electron delocalization and enhances electron density, thereby effectively suppressing electron‐hole recombination and augmenting the charge transfer rate. Simultaneously, acting as a porous substrate, it boosts electron density of Pd nanoparticle loaded on its surfaces, resulting in remarkable CO2 photoreduction catalytic activity (CO generation rate: 48.1 μmol/g/h) without the need for hole scavengers. Our study provide insight into regulating the charge carrier behaviours in molecular assemblies based on hydrogen bonds, offering a new clue for efficient photocatalyst design. Natural systems optimize charge carrier behavior via molecular spatial arrangement, a phenomenon largely unexplored in artificial systems. PFC‐1, a hydrogen‐bonded organic framework with controllable π‐stacking, offers valuable insights into this process. Varying π‐stacking perpendicular to the π‐conjugated plane in HOFs alters electron density, redox potential, and charge carrier transport and separation, thereby enhancing catalytic performance.