Unveiling the photocatalytic potential of mesoporous carbon nitride in environmental applications: Properties, synthesis and doping strategies

Abstract

Graphitic carbon nitride (in simple terms, g-C₃N₄) is a metal-free semiconductor polymer material with many properties, alike graphene, and having a composition of carbon and nitrogen with some hydrogen impurity in its structure. However, unlike graphene, g-C₃N₄ possesses an intermediate energy gap between the valence and conduction band. High thermal and chemical stability with a conjugated polymerised geometric arrangement of g-C₃N₄ enhances its photon harvesting potential, leading to improved photocatalytic oxidation and reduction efficiency. The π-conjugated system in g-C₃N₄ possesses great potential for tuning the delocalised electrons as well as the intercalation of foreign structures which synergise the catalytic effects and enhance the redox efficiency by several folds. The tunable optoelectronic properties, HOMO-LUMO positioning and the hybridisation of the molecular orbital between g-C₃N₄ and dopant molecule expand the horizon of the fate of g-C₃N₄ polymer in numerous areas as a photocatalyst material with tremendous potential. In this article, the facile synthetic routes for the g-C₃N₄ synthesis are discussed along with the mechanisms for enhanced catalytic efficiencies of pristine g-C₃N₄ via various doping, co-doping and heterojunction engineering. Furthermore, the use of machine learning methods for analysis, as well as validation of its exceptional photocatalytic potential, is briefly summarised.