Metal-free defects in 2D Nanocarbons toward photocatalytic processes: Revolutionizing solar-to-energy conversion

H₂ and O₂ generation are vital in pursuing sustainable energy, aligning with Sustainable Development Goal 7. 2D photocatalysts are promising due to their unique structure and high surface-to-volume ratio, enhancing catalytic efficiency. Carbon-based materials stand out for their excellent π-π conjugation, strong light absorption, and chemical versatility. Despite limitations, they hinder their broad-scale use, such as limited charge carrier kinetics, restricted light absorption, suboptimal quantum efficiency, graphene's chemical inertness, and agglomeration issues. This review paper mainly highlights the role of metal-free defects in 2D nanocarbons in revolutionizing solar-to-energy conservation. These metal-free photocatalysts are promising candidates for sustainable catalytic processes owing to the defect sites in the carbon matrix, categorized as metal-free point defects and volume defects. The main emphasis is on understanding how point and volume defects improve the overall photocatalytic efficiency. Point defects, including carbon and nitrogen, usually disrupt the electron distribution in the lattice, and volume defects, involving lattice distortions, edge defects, Stone-Wales defects, and pits/voids, generate abundant active sites. This integrated approach, combining defect engineering, material diversity, and practical applications, positions the review as a significant and innovative contribution to the field. Leveraging the properties of carbon-based 2D materials and addressing various challenges through defect engineering can lead to the development of highly effective and sustainable photocatalysts, advancing renewable energy efforts and contributing to global sustainability.