The pressing necessity to mitigate climate change and decrease greenhouse gas emissions has driven the advancement of heterostructure-based photocatalysts for effective CO₂ reduction. This study introduces a novel heterojunction photocatalyst formed by integrating potassium-doped polymeric carbon nitride (KPCN) with metallic Zn₃N₂, synthesized via a microwave-assisted molten salt method. The resulting Schottky contact effectively suppresses the reverse diffusion of electrons, achieving spatial separation of photogenerated charges and prolonging their lifetime, which significantly enhances photocatalytic activity and efficiency. Additionally, the incorporation of Zn₃N₂ improves CO₂ adsorption capacity, a critical factor for effective reduction. Comprehensive characterization, including theoretical simulations, reveals that photogenerated electrons migrate efficiently from KPCN to Zn₃N₂, facilitating optimal charge separation. Under visible light irradiation, the Zn₃N₂/KPCN composite demonstrates remarkable photocatalytic activity, attaining CH₄ production rate of 32.28 μmol g⁻