In this study, first, graphitic carbon nitride was treated with hydrogen peroxide (abbreviated as H2O2-g-C3N4), then was used as a new hydrophilic nanomaterial in the fabrication of polyethersulfone (PES) mixed matrix membrane (MMM) for improving flux, protein and dye separation efficiency and antifouling properties. The H2O2-g-C3N4 nanosheet was inserted into the doping solution to fabricate PES/ H2O2-g-C3N4 nanocomposite membrane with the non-solvent induced phase inversion procedure. The results of the SEM and AFM images and also porosity and contact angle analysis were indicated that the modified membranes with H2O2-g-C3N4 had more porosity, smoother surface and more hydrophilic. Also, the influence of various weight percentage of H2O2-g-C3N4 was investigated systematically on the membrane performance. By blending of H2O2-g-C3N4 nanosheet in the membrane matrix, the permeability was raised from 4.1 (for bare membrane) to 30.1 L m(-2) h(-1) bar(-1). Additionally, the effect of the H2O2-g-C3N4 material on the antifouling features indicated that the flux recover ratio of the H2O2-g-C3N4 MMMs was improved and the resistance parameters were reduced. Also, the effect of the H2O2-g-C3N4 material on the antifouling features indicated that the flux recover ratio of the H2O2-g-C3N4 MMMs was improved and the resistance parameters were reduced. Finally, the dye rejection efficiency of the nanocomposite membranes for Orange II and Reactive Yellow 168 was improved. As a result, it could be mentioned that the mixing low amount of H2O2-g-C3N4 in the membrane structure could significantly improve the membrane flux and antifouling properties without reduction in membrane rejection efficiency. (C) 2021 Elsevier Ltd. All rights reserved.