Deuteration Induced Electron‐Phonon Coupling Modulation: Suppressing Energy Dissipation and Enhancing Carrier Separation in Organic Photocatalysis

Abstract The electron‐phonon coupling in organic photocatalysts offers a great opportunity for tuning carrier behaviors and energy dissipation toward improving photocatalytic efficiency. Adopting strategies to tailor electron‐phonon coupling and revealing the underlying mechanism are therefore essential for the development of high‐efficiency organic photocatalysts. In this work, an isotope substitution strategy is developed by replacing H in high‐frequency C─H oscillators with D to tune the electron‐phonon coupling strength of both 1,2,3,5‐tetrakis(carbazol‐9‐yl)‐4,6‐dicyanobenzene (4CzIPN) and its polymeric derivative. The fitted Huang–Rhys factors exhibit an ≈1.7‐fold increase upon isotopic deuteration, revealing enhanced electron‐phonon coupling. Comprehensive studies demonstrate that the deuteration strategy can effectively lower exciton binding energy, promote exciton dissociation, and suppress non‐radiative energy dissipation, therefore leading to an improved efficiency toward photocatalytic hydrogen evolution. This study highlights the crucial role of electron‐phonon coupling on photocatalytic systems and presents a novel regulatory strategy for designing high‐efficiency organic photocatalysts.