Most industries depend mainly on oil and oil-based processes, which resulted in producing large volumes of oily wastewater. One of the most common methods used for the treatment of oily contaminated water is filtration by modified surfaces. In this research g-C3N4 nanostructured material was prepared via thermal condensation method. The samples were characterized by advanced techniques such as XRD, XPS, FTIR scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectrophotometry (EDX). The result showed that g-C3N4 were crystallized in tri-s-triazine phases and their mean crystalline sizes of these nanostructures were 12.17 nm. The high-magnification microscopy images show that the morphology of g-C3N4 was nanosheet. A stainless-steel mesh was modified and coated with the prepared g-C3N4 nanostructured materials to be used for the separation of oil and water mixture. Due to the hydro-phobic nature of the modified meshes, oil drops spread over the mesh surface and the water drops form spherical shapes. The most efficient coating among all the modified meshes was g-C3N4, which was functionalized using silane moiety. The separation efficiency of this coated mesh reached 74.87% and it resulted in fast separation. This mesh can separate different types of oil from the oil/water mixture, such as toluene, mineral oil, 2-ethyl-1-hexanol, and n-pentane with good efficiency. Separation was repeated up to 40 times using the same mesh, and the separation efficiency was measured each time.