Porous polymeric graphitic carbon nitride nanosheets were obtained by ithium chloride ions in situ intercalating bulk materials in polycondensation process and followed by liquid exfoliation in water.

The nanosheets with 2–3 nm in thickness and high density in-plane pore with 2–3 nm diameters, which exhibit superior photocatalytic efficiency for hydrogen evolution and enhanced photocurrent responses in comparison of bulk materials.

Compared to bulk materials, nanosheets possess a higher surface area (186.3 m² g⁻¹), high density mespores with 2–3 nm diameter, enlarged bandgap (by 0.16 eV), prolonged charge carrier lifetime, improved electronic transport ability, increased charge carrier density and enhanced photocurrent responses, which make great contributions to the improvement of photocatalysis.