Organic motif's functionalization via covalent linkage in carbon nitride: An exemplification in photocatalysis

Carbon nitride (commonly termed as g-C₃N₄) is a promising π-conjugated polymeric organic metal-free semiconductor. An inexpensive chemical synthesis procedure, phenomenal chemical stability and tuneable electronic structure of g-C₃N₄ has provoked its tremendous interest in photocatalysis. However, intrinsic limitations of pristine g-C₃N₄, such as low specific surface area, low visible light absorption ability and fast electron-hole recombination rate are quite unsatisfactory and decline it's photocatalytic efficiency. Therefore, considerable amount of efforts have been devoted to overcome these limitations by engineering the electronic structure of g-C₃N₄ at the molecular level. One of the ways is rational modifications in the electronic structure of conjugated g-C₃N₄ by integrating diversified set of organic motifs via covalent linkage which is highly recommended. Such covalent functionalization of organic motifs onto the surface of g-C₃N₄ provides strong covalent interaction between functionalized moieties and g-C₃N₄ synergistically improving the stability, electronic and optical properties. In this review, we attempt to highlight covalent engineering aspects of g-C₃N₄ electronic structure by integrating molecular organic motifs through post modification and pre-modification strategy, as it results in relative degree of improvement in physiochemical properties and its effect in photocatalytic applications.