Two-dimensional (2D) heterojunctions composed of two or more 2D materials have unique electronic features at the nanoscale interfacial region, endowing the possibility of efficient carrier transport and migration. In this work, a novel heterojunction composite Bi4O5I2/g-C3N5/Bi2O2CO3(BIC) was designed and synthesized by an alkaline solution-induced growth method. XRD, XPS, and TEM analyses showed that the contact mode of each component nanosheet is a close type, and the interface is clear, which facilitates the carrier transfer between semiconductors. The study of the energy band structure shows that the BIC heterojunction establishes a close-contact Type I and Z-scheme energy band arrangement, which not only ensures the material has excellent redox ability but realizes effective carrier separation. This study provides a potential catalyst for photocatalytic treatment of wastewater, as well as a new idea for designing new and efficient catalysts through bismuth-based materials and carbon nitride materials.