Electronic Modulation of K⁺‐Intercalated Polymeric Carbon Nitride via ─C≡N/─OH Functionalization for Efficient Photocatalytic H ₂ O ₂ Production

Polymeric carbon nitride (PCN) holds great promise for photocatalytic H 2 O 2 production owing to its excellent stability and structural tunability. However, the inferior overall photocatalytic performance of PCN owing to its limited charge separation efficiency is a longstanding challenge. Herein, a K⁺‐doped bridge‐type PCN featuring ─C≡N and ─OH surface groups is synthesized via thermal polymerization. K‐PCN exhibits superior efficiency for photocatalytic H 2 O 2 production (8647.78 µM·h −1 ) with a quantum efficiency of 17.92% at 420 nm, remarkably surpassing that of PCN (86.96 µM·h −1 and 0.129%). K⁺ ions tend to reside within the interlayers of PCN, where they create K + ‐bridges that reduce interlayer spacing, strengthen π–π stacking, and improve crystallinity, thereby accelerating charge transport by shortening carrier migration pathways and suppressing recombination. Moreover, K + perturbs the local electronic structure via interaction with nitrogen lone pairs, thereby narrowing the bandgap and enhancing visible‐light absorption. The introduction of ─C≡N and ─OH groups enrich the surface with polar sites, with ─C≡N promoting O 2 adsorption and activation through electron delocalization and ─OH increasing hydrophilicity and O 2 concentration via hydrogen bonding. This study elucidates the pathway and mechanism of photocatalytic oxygen reduction and provides novel insights into the reasonable design of bridge‐type group‐modified PCN for efficient H 2 O 2 production.