This study explores the potential for improved photocatalytic activity by tailoring the properties of two-dimensional graphitic carbon nitride (g-C₃N₄) through non-metallic molecule modifications. Herein, melamine monomers were thermally polymerized in the presence of organic materials, namely (E)-2-((phenylimino)methyl) phenol, (E)-4-(benzylideneamino)benzoic acid, and (E)-4-((hydroxybenzylidene)amino)benzoic acid, to produce g-C₃N₄-PMP, g-C₃N₄-BAB, and g-C₃N₄-HBAB nanosheet composites, respectively. The investigated Schiff bases offer a variety of functionalities capable of influencing the electronic structure, surface reactive sites, and porosity. Consequently, all of the modified composites exhibited higher efficiency in photocatalytic hydrogen generation compared to pristine g-C₃N₄. Notably, the highest catalytic activity was observed for g-C₃N₄-PMP, with a rate of 1148 µmol•g⁻¹•h⁻¹, which is seven times greater than that of g-C₃N₄. Optical and photoelectrochemical properties of the photocatalysts were analyzed to develop a workable mechanism for photocatalysis. The utilization of organic Schiff bases in conjunction with melamine for the g-C₃N₄ synthesis presents a versatile approach to tailor the properties and augment the photocatalytic performance of the resulting nanocomposite material for diverse environmental and energy-related applications.