Synthesis of Poly(heptazine imide) Ultrathin Nanosheets via Dialysis-Delamination of Potassium Poly(heptazine imide) for Photocatalysis

Semiconductor ultrathin nanosheets are considered excellent photocatalysts due to their abundant surface-active sites and high photogenerated charge separation efficiencies. However, the formation of the ultrathin nanosheets is typically accompanied by a reduction in crystallinity, which can compromise their photocatalytic performance. Herein, ∼0.5 nm thick poly(heptazine imide) (PHI) ultrathin nanosheets were easily synthesized via dialysis-delamination of potassium poly(heptazine imide) (PHI-K). Remarkably, these nanosheets exhibit considerably enhanced crystallinity. Due to improved photogenerated charge separation and increased surface area, the ultrathin nanosheets display pronounced superiority in photocatalytic hydrogen evolution over both PHI-K and acid-treated PHI-K (PHI-H). Co-modified with Pt@CrOx and CoOH groups, the ultrathin nanosheets exhibit 300 and 27 times higher photocatalytic overall water splitting activity than PHI-K and PHI-H, respectively. Overall, this work presents a method to prepare organic semiconductor ultrathin nanosheets with enhanced crystallinity.