Assessment of synthesis methods and hetero-element doping as strategies to modulate the photo-catalytic properties of nitrogen rich g-C3N5 polymorph

Carbon nitrides (CN) are notable for being metal-free and simple to produce options compared to conventional materials used in catalytic applications, particularly in photocatalysis. In recent years, a nitrogen-rich polymorph of CN, typically known as g-C 3 N 5 , demonstrated distinctly improved structural, optical, and electronic characteristics when compared to conventional g-C 3 N 4 . The enhanced characteristics of g-C 3 N 5 particles are attributed to the incorporation of an additional nitrogen atom within the lattice framework. These additional nitrogen atoms can be incorporated within basic heptazine units, the foundational blocks of the CN network, selectively at different positions by adequately selecting the precursors and the synthetic methods. This leads to a variety of linkage pattern which in turn alters the density of states and modulate the overall textural and opto-electronic properties. Additionally, numerous strategies have been employed to enhance the photocatalytic performance of g-C 3 N 5, such as defect engineering and heteroatom doping. In this regard, this review aims to comprehensively analyse different types of C 3 N 5 polymorphs reported in recent years, focusing on the synthesis procedures, type of nitrogen linkage, and structural changes witnessed after doping, leading to distinct ring arrangements, and how these changes influence their performance in specific photocatalytic applications. This thorough analysis will assist us in determining the optimal synthesis protocol and understanding structural alterations that occur, followed by heteroatom doping, guiding a promising way for future research on g-C 3 N 5 .