**2.1 Preparation of g-C3N4 nanosheets**

The g-C3N4 was prepared by a thermal condensation method using melamine as a precursor. 5 g of melamine was kept in an alumina crucible and thermally treated at 550°C for 3 h in a furnace. The obtained agglomerate residues are ground into fine powder and subjected to hydrochloric acid treatment for 12 h to obtain the g-C3N4 nanosheets. The suspension was centrifuged to separate the residual of g-C3N4 nanosheets. The obtained precipitate product was heated at 60°C for overnight to attain the light yellow colored powder of g-C3N4 nanosheets.
