Targeted Exfoliation and Reassembly of Polymeric Carbon Nitride for Efficient Photocatalysis

Switching the properties of photocatalytic materials targetedly and exerting these advantages fully in different photoredox reactions are crucial for the sufficient utilization of solar energy but still presents a significant challenge. This study presents a facile, green, and reversible exfoliation–reassembly strategy to switch the features of polymeric carbon nitride (CN) favorably for different photoredox reactions. The giant expansion effect of in situ‐generated H₂O molecules confined to the interlayer results in the mass production of ultrathin polymeric CN nanosheets, giving a high yield, i.e., up to 48%, of ultrathin nanosheets in a mild solution (pH ≈1.3). Interestingly, the exfoliation–reassembly process as well as the properties of CN are largely reversible via alternating the interlayer groups. Moreover, the exfoliated and reassembled CN achieve a superior photocatalytic activity for isopropanol degradation (acetone: 345 µmol h^?1; CO₂: 23 µmol h^?1) and H₂ evolution (1370 µmol h^?1), resulting in a high apparent quantum yield of 27% and 46%, respectively, at ≈420 nm.