Protonation‐Triggered Unlocking of Interlayer Carbon Nitride for Rapid Nanosheet Preparation

ABSTRACT The intrinsic topological and electronic merits of graphitic carbon nitride (g‑C 3 N 4 ) are fundamentally obscured by strong π‐π stacking interactions and hydrogen‐bonding interactions. Overcoming these noncovalent barriers without compromising the structural integrity remains a formidable chemical challenge. Herein, we report a targeted electrostatic decoupling strategy via protonation that rapidly unlocks the intralayer framework of g‑C 3 N 4 into discrete, highly crystalline two‐dimensional (2D) nanosheets under ambient conditions. By utilizing trifluoromethanesulfonic acid, selective protonation at the heterocyclic nitrogen sites induces pronounced interlayer electrostatic repulsion and simultaneous intralayer electronic reconstruction, achieving an unprecedented production efficiency of 200 mg·mL −1 ·h −1 . Crucially, the high aspect ratio and structural fidelity of the as‐exfoliated nanosheets enable unambiguous direct observation of the intrinsic lyotropic liquid‐crystalline phase transition in pure g‑C 3 N 4 , resolving long‐standing ambiguities regarding its mesoscopic assembly behavior. Furthermore, the 2D nanosheets display over 50‐fold enhancement in photocatalytic hydrogen peroxide production activity compared to their bulk counterpart, attributed to the reduced thickness and significantly increased exposure of active sites. This work not only provides an efficient route for the exfoliation of layered polymers but also opens new opportunities for their solution‐phase processing.