Synergism of defect and band engineering in ultra-thin metal free organic C(CN) 3 nanosheet for efficient photocatalytic CO 2 reduction

Photocatalytic CO 2 conversion is an effective and promising strategy for alleviating carbon emissions and energy crisis. Herein, an aqueous ultrasonic method is applied to exfoliate bulk half metallic C(CN) 3 into ultra-thin atomic layered C(CN) 3 nanosheets. It found that after 20 h of ultrasonic treatment, the as-obtained C(CN) 3 -20 presents a significantly improved photocatalytic CO 2 reduction activity. The CO production rate reaches 285.3 μmol g −1  h −1, fiftyfold of the bulk C(CN) 3. The significant improvement in photocatalytic performance can be attributed to the following factors: (1) exfoliation reduces the particle size and increases the specific surface areas of the material. Thus, the atomic utilization efficiency is improved; (2) the bandgap of the material is enlarged after exfoliation, while suitable bandgap further promotes photocatalytic CO 2 conversion; (3) the optimized surface defect concentration enhances the separation efficiency of photogenerated electrons and holes. This study demonstrates the synergistic effect of defect regulation and band engineering on photoelectric property modulation for metal-free organic C(CN) 3, enabling highly selective and efficient CO 2 photoconversion.