Controllable synthesis of graphitic carbon nitride nanomaterials for solar energy conversion and environmental remediation: The road travelled and the way forward

In recent years, graphitic carbon nitride (g-C₃N₄) has elicited interdisciplinary research attention and experienced a renaissance as a highly active metal-free and visible-light-driven photocatalyst due to it bringing about a dramatic cost-effective increase in the conversion of solar energy into electricity and fuels, along with its use under solar light for environmental purification. This is because of its appropriate electronic energy band structures, efficient optical absorption, and extraordinary thermochemical stability. In the current review, the cutting-edge research progress in the synthesis and design of high-efficiency g-C₃N₄-based nanomaterial photocatalysts with controllable structures and morphologies will be rationally discussed with special focus on a plenitude of not only photocatalytic applications in pollutant degradation and bacterial disinfection, but also photoredox applications towards H₂ production from water splitting, photocatalytic O₂ reduction to produce H₂O₂, N₂ photofixation, and photoreduction of CO₂. Finally, this critical review will conclude with a summary and some outlooks on the ongoing challenges, which provide new research opportunities for the advancement of g-C₃N₄-based metal-free nanomaterial photocatalysts. It is envisaged that this review article will shed light on and pave the way for new research avenues for the rational design and synthesis of the next generations of g-C₃N₄ heterogeneous photocatalysts for the advancement of a sustainable future.