Sustainable and mild exfoliation of bulk crystalline carbon nitride into ultrathin nanosheets via ion-exchange in pure-water

Semiconducting two-dimensional (2D) materials, or nanosheets, have been gaining wide attention in photocatalysis field due to their abundant active sites, short charge diffusion length, and more powerful photo-reduction/-oxidation ability than that of the bulk counterparts. The heptazine-based crystalline carbon nitride, named poly(heptazine imide) (PHI), is a polymer semiconductor being extensively investigated in the past decade. PHI nanosheets have demonstrated the superiority in photocatalytic reactions over bulk PHI, however, the current strategies to derive PHI nanosheets are generally costly, energy-consuming, as well as destructive. Herein, PHI nanosheets are sustainably and mildly synthesized by simply agitation of the bulk PHI in deionized water, which acts as both ion-exchange and stabilization agents. As-prepared PHI nanosheets exhibit significantly improved photocatalytic hydrogen evolution activity than that of the bulk PHI under visible light irradiation. The sustainable and large-scale synthesis of PHI nanosheets was proposed to stimulate the exfoliation research of other 2D materials.