Graphitic C ₃ N ₄ -Confined B Enables Bifunctional Lattice N Atoms for Photocatalytic CH ₄ Conversion

The photocatalytic conversion of CH4 and O2 to C1 oxygenates represents a promising route for chemical synthesis, yet current systems predominantly depend on metal-based catalysts to achieve efficient light harvesting and charge separation. Herein, we report a metal-free alternative using boron confined within g-C3N4 (B/C3N4), which achieves a C1 oxygenates production rate of 28.1 μmol gcat.–1 h–1 with a 60% improvement in activity compared with pristine g-C3N4. Combined experimental and theoretical investigations reveal that boron confinement in g-C3N4 induces orbital delocalization, which enhances charge carrier separation and creates dual-functional nitrogen sites that facilitate CH4 oxidation and O2 reduction reactions. Delocalized nitrogen sites with the lowest unoccupied molecular orbital are responsible for reducing O2 to •OH radicals, whereas counterparts with the highest occupied molecular orbital facilitate the oxidation of CH4 to •CH3 radicals. The resulting •OH radicals can either oxidize CH4 to generate •CH3 or directly combine with transient •CH3 radicals, initiating a cascade reaction that sequentially yields CH3OH, HOCH2OH, and HCOOH.