 Abstract the graphitic carbon nitride, GAC3 and 4, which is a two-dimensional conjugated polymer has drawn broad interdisciplinary attention as a low-cost, metal-free, and visible light-responsive photocatalyst in the area of environmental remediation. The GAC3 and 4 based materials have excellent electronic band structures, electron-rich properties, basic surface functionalities, high-physical chemical stabilities, and are earth-abundant. This review summarizes the latest progress related to the design and construction of GAC3 and 4 based materials and their applications, including catalysis, sensing, imaging, and white-light emitting diodes. An outlook on possible further developments in GAC3 and 4 based research for emerging properties and applications is also included. This article was authored by IWU Wang, Chen Dong-Wang, Li Fu, and others.