Synergy of crystallinity modulation and intercalation engineering in carbon nitride for boosted H₂O₂ photosynthesis

Photosynthesis of hydrogen peroxide (H₂O₂) by selective oxygen reduction is a green and cost-effective alternative to the energy-intensive anthraquinone process. Although inexpensive polymeric graphitic carbon nitride (g-C₃N₄) exhibits the ability to produce H₂O₂, its disordered and amorphous structure leads to a high recombination rate of photogenerated carriers and hinders charge transfer between layers. Herein, we predict that stacked polymeric g-C₃N₄ with ion intercalation (K⁺ and I^-) can improve carrier separation and transfer by multiscale computational simulations. The electronic structures of g-C₃N₄ were tailored and modified by intercalating K⁺ and I^- into the layer-by-layer structures. Guided by the computational predictions, we achieved efficient solar-driven H₂O₂ production by employing this facile and ion-intercalated crystalline g-C₃N₄. An H₂O₂ production rate of 13.1 mM g^-1 h^-1 and an apparent quantum yield of 23.6% at 400 nm were obtained. The synergistic effects of crystallinity regulation and dual interstitial doping engineering triggered the formation of new light absorption centers, the establishment of rapid charge diffusion channels, and the enhancement of two-electron oxygen reduction characteristics. This work sheds light on the dual tuning of crystallinity and electronic structure and broadens the design principles of organic-conjugated polymer photocatalysts for environmental remediation and energy conservation.