Electron‐Hole Trap Regulation in Porous Ultrathin g‐C 3 N 4 Nanosheet for Enhanced Photocatalytic H 2 Evolution and CO 2 Reduction

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Graphitic carbon nitride (g‐C 3 N 4 ) is a prospective photocatalyst for solar‐to‐chemical conversion, but the rapid electron‐hole recombination rate in pristine g‐C 3 N 4 (CN) limits its activity. Herein, S/N co‐doped porous ultrathin g‐C 3 N 4 nanosheet (MCN‐NS) is synthesized to improve the charge‐carrier transport from bulk to surface and regulate electron‐hole trapping sites. The porous ultrathin nanosheets facilitate charge dynamics, and S/N dopants act as electron/hole trapping sites, respectively, creating an intrinsic donor–acceptor configuration that reduces charge recombination rate in MCN‐NS compared to CN. As a result, MCN‐NS demonstrates an enhanced photocatalytic H 2 evolution rate of 8228 μmol h −1 g −1 , which is 32.3 times higher than that of CN, with an apparent quantum yield (AQY) of 15.2% at 400 nm. Additionally, MCN‐NS shows efficient CO 2 to CO and CH 4 conversion rates of 89.5 and 18.6 μmol h −1 g −1 , respectively, in pure water without sacrificial agents or co‐catalysts. This work presents a practical route for controlling charge dynamics in g‐C 3 N 4 and improving solar‐to‐chemical conversion efficiency.