Molecularly Modulated Charge Retention Enables Post-Illumination H₂O₂ 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 H₂O₂ 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 C₃N₃-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 H₂O₂ 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 C₃N₃-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 H₂O₂ production beyond the illumination period.