Synergistic 2D MoO₃/g-C₃N₄ heterostructures for highly efficient photocatalytic removal of cationic dyes: a response surface methodology approach

2D MoO₃/g-C₃N₄ nanosheets were synthesized via a simple impregnation–hydrothermal approach and investigated as efficient photocatalysts for the degradation of cationic dyes in water. Structural and compositional analyses confirmed the successful formation of a tightly coupled heterostructure. Density functional theory (DFT) calculations revealed a strong interfacial contact and pronounced electronic interaction between MoO₃ and g-C₃N₄, resulting in a markedly reduced HOMO–LUMO gap and efficient interfacial charge transfer. The photocatalytic performance was evaluated using methylene blue (MB) and crystal violet (CV) under UV irradiation, achieving complete MB degradation and ∼90% CV removal within 30 min. The corresponding pseudo-first-order rate constants were 0.0995 min⁻ 1 MB and 0.0749 min⁻ 1 CV. Mechanistic investigations supported a direct Z-scheme charge-transfer pathway, where electrons preferentially accumulate on g-C₃N₄ and holes on MoO₃, preserving strong redox capability. The enhanced activity is attributed to efficient charge separation and the generation of reactive species (•O₂⁻ and h⁺). The composite also exhibited excellent stability and reusability, highlighting its promise for wastewater treatment applications.