Size-dependent design of ultrathin g-C3N4 nanomesh with N defects towards superior visible-light photocatalytic efficiency

The bottom-up approach from precursors to directly obtain porous g-C₃N₄ nanosheets has rarely been reported. In this paper, a facile way from size-dependent design is highlighted to fabricate ultrathin graphitic carbon nitride (g-C₃N₄) nanomesh with across-plane multihole and N defects. Control of melamine precursor size is believed to determine the lateral dimension and thickness of the resulting nanosheets. By hydrothermal treatment, the reduced size of precursor is achieved during which phase transformation, hydrogen bond breakage and oligomerization occur simultaneously. The resultant g-C₃N₄ nanomesh possess a wealth of meso- and macropores, a high surface area of 177.2 m² g⁻¹ and a large pore volume of 0.921 cm³ g⁻¹. As expected, the g-C₃N₄ nanomesh exhibited superior visible-light photocatalytic efficiency owing to more active sites, increased optical absorption ability, fast mass transfer and charge migration, as well as efficient photogenerated charge pairs separation, benefiting from N defects and ultrathin multihole structure.