Molecularly Modulated Charge Retention Enables Post‐Illumination H 2 O 2 Production in Imine‐Linked Polymers

Decoupling photocatalytic solar fuel generation from continuous illumination is a prerequisite for practical off‐grid applications, yet demands precise control over photogenerated charge retention and dark‐phase utilization. While persistent charge availability post‐light cutoff is central to dark‐state catalysis, a quantitative structure‐dynamics‐function relationship linking molecular design to charge‐retention kinetics and post‐illumination reactivity remains unestablished. Here, we report a molecular tuning strategy of the central amine‐derived units that systematically regulates charge separation, retention timescales, and dark‐state H 2 O 2 production in imine‐linked polymer networks. Systematic evaluation of the series reveals a direct correlation between charge lifetime and dark activity. Compared with the N‐centered reference, the C 3 N 3 ‐centered analogue exhibits drastically prolonged electron‐associated transient lifetime, with a ∼27‐fold longer decay timescale at the picosecond scale and a ∼3‐fold increase at the nanosecond scale. This enhanced charge retention corresponds to a dark‐state H 2 O 2 production of 4941 µmol g −1 within 40 min, ∼1.5‐fold higher than that of the N‐centered counterpart. Density functional theory calculations reveal distinct electronic structures associated within the C 3 N 3 ‐centered framework, providing a favorable electronic environment for electron localization and subsequent utilization. These results establish a molecular structure‐charge retention‐dark reaction relationship for photocatalytic H 2 O 2 production beyond the illumination period.