Semiconductor photocatalytic technology has been proved as an effective way to solve the problems of both environmental pollution and energy shortage. It can be applied for the degradation, transformation and mineralization of pollutants in the environment, and for the conversion of solar energy as well. Graphite phase carbon nitride (g-C₃N₄) and bismuth based composite materials have become the hot research topic because of their excellent photocatalytic performance. This paper reviews the preparation methods of g-C₃N₄ and its composites with different bismuth compounds. We also reviews the recent advances of the application of g-C₃N₄ and Bi composites in the environmental purification, including the elimination of pollutants in water, the light induced bacterial inactivation, and the photoinduced hydrolysis for hydrogen production. Taking the elimination of organic contaminants in water as an example, this paper elaborate detailedly their mechanisms of photocatalytic degradation. Finally, we prospect the new development and application potential of the g-C₃N₄ and Bi based composite photocatalytic materials in the environmental field.

Contents
1 Introduction
2 Synthesis of g-C₃N₄
2.1 Thermal polymerization method
2.2 Solvothermal synthesis
2.3 Electrochemical deposition
2.4 Solid phase synthesis
3 Preparation of g-C₃N₄ and bismuth based composites
3.1 Preparation of g-C₃N₄/Bi based halide oxides composites
3.2 Preparation of g-C₃N₄ and bismuth metal salts composites
3.3 Preparation of g-C₃N₄ and other bismuth compounds
4 Application of composites in the environment
4.1 Removal of organic pollutants in water environment
4.2 Photocatalytic hydrogen production by water splitting
4.3 Application of composite materials in other areas
5 Reaction mechanisms
6 Conclusion