The graphene-like carbon nitride (C₃N₄) nanomaterials have sparked global interest owing to their exclusive optical and electronic properties. Herein, a cost-effective, nonhazardous, and environment-friendly nonmetal, such as sulfur (S), phosphorus (P), and boron (B)-doped graphitic carbon nitride (g-C₃N₄), was synthesized through thermal decomposition of urea. Moreover, diverse morphologies were obtained, which exhibited excellent photocatalytic activity. The synthesized nonmetal-doped g-C₃N₄ composites were exercised for the photodegradation of methyl blue (MB) under visible light irradiation. In the photodegradation process, the decontamination removal rate of MB is achieved by (S-g-C₃N_4, P-g-C₃N₄, B-g-C₃N₄, and g-C₃N₄) samples of about 99%, 87%, 60%, and 40%, respectively, and the maximum pseudo-first-order reaction constant “K” 44.00 min × 10^–3 was achieved. S-doped g-C₃N₄ showed enhanced photodegradation activity in comparison with pristine g-C₃N₄ and other nonmetal-doped g-C₃N₄ composites due to a favorable bandgap of 2.4 eV, attributing to more visible energy absorption. The promising photodegradation mechanism of MB using g-C₃N₄ composites is discussed. Moreover, the photodegradation route MB and the possible photocatalytic mechanism are mainly investigated.