In this study, a series of hydrophilic graphitic carbon nitride (g-C3N4) nanosheets was synthesized with various oxygen donor compounds to produce OH, COOH and SO3H groups on the surface of g-C3N4 and incorporated in polyamide layer (PA) of thin film nanocomposite (TFN) membrane to fabricate reverse osmosis (RO) membranes with excellent antifouling and desalination properties. The results of FTIR and EDX analysis indicated the successful introduction of functional groups on the g-C3N4 nanosheets surface. The average surface roughness of the modified membranes with COOH functionalized g-C3N4 nanosheets decreased to 3.2 nm with 82% decrease compared with g-C3N4 modified membranes. The effect of incorporated g-C3N4 nanosheets on the performance of the membranes was studied using pure water flux, NaCl and BSA solution filtration. The outcomes showed that introducing of the functionalized g-C3N4 nanosheets in the PA active layer of the membranes improved considerably the membrane permeation without decrease in rejection performance. The modified membrane with COOH functionalized g-C3N4 nanosheets showed maximum pure water flux of 91.8 L/m(2) h with 54% increase compared with g-C3N4 modified membranes.