摘要： Two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanoplates (CNNP) have become a hot research topic in photocatalysis due to their small thickness and large specific surface area that favors charge transport and catalytic surface reactions. However, the wide application of 2D g-C3N4 nanoplates prepared by ordinary methods suffers from increased band gaps with a poor solar harvesting capability caused by the strong quantum confinement effect and reduced conjugation distance. In this paper, a facile approach of exfoliation and the following fast thermal treatment of the bulk g-C3N4 is proposed to obtain a porous few-layered g-C3N4 with nitrogen defects. Due to the preferable crystal, textural, optical and electronic structures, the as-obtained porous CNNP demonstrated a significantly improved photocatalytic activity towards water splitting than the bulk g-C3N4 and even the 3 nm-thick CNNP obtained by sugar-assisted exfoliation of the bulk g-C3N4. The difference in the enhancement factors between the H2O splitting and organic decomposition has revealed the effect of N defects. This study offers insightful outlooks on the scalable fabrication of a porous few-layered structure with a promoted photocatalytic performance.