The role of the M-N4 site for the electronic regulation of g-C3N4-based catalysts: A mini-review

In the current era of escalating concerns over energy and water pollution, the quest for highly efficient semiconductor materials has emerged as a critical priority. In this context, semiconductor catalysts based on the M-N ₄ structure constructed on carbon and nitrogen materials have garnered significant attention due to their uniform active sites, distinctive electronic properties, and exceptional redox activity. However, these catalysts often encounter commercial challenges such as unstable metal center atoms and unmanageable coordination numbers. While graphitic carbon nitride (g-C ₃N ₄ ) based on stable tri-s-triazine aromatic heterocycles can effectively address these issues, there is a dearth of discussion on the electronic regulation mechanism of M-N ₄ sites for g-C ₃N ₄-based catalysts. This review aims to provide a comprehensive overview of the configuration of M-N ₄ sites on the g-C ₃N ₄ substrate and to explore the influence of specific M-N ₄ sites on the electronic state density of the g-C ₃N ₄ substrate, thereby enhancing our understanding of the correlation between the electronic structure of the catalyst and its catalytic performance. Furthermore, we present several strategies for regulating the electron density of g-C ₃N ₄-based catalysts containing M-N ₄ sites, including non-metal atom doping, the introduction of vacancies, and the creation of dual-atom catalysts (DACs), with the goal of optimizing the catalyst`s performance and facilitating its practical application. Finally, we discuss the current challenges and potential future directions for g-C ₃N ₄-based catalysts containing g-C ₃N ₄ sites, with the belief that this will offer theoretical guidance for the future design of efficient catalysts and contribute to their successful implementation.