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-C 3 N 4 nanosheets has rarely been reported. In this paper, a facile way from size-dependent design is highlighted to fabricate ultrathin graphitic carbon nitride (g-C 3 N 4 ) 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-C 3 N 4 nanomesh possess a wealth of meso- and macropores, a high surface area of 177.2 m 2 g −1 and a large pore volume of 0.921 cm 3 g −1 . As expected, the g-C 3 N 4 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. • Ultrathin g-C 3 N 4 nanomesh were prepared from size-dependent design. • Hydrogen bonds fracture and oligomerization occur in crystal cracking. • Nanomesh favors risen optical absorption, charge transfer and pairs separate. • Superior performance owing to N defects and ultrathin multihole structure.