Carbon nitride grafted with single-atom manganese and 2-hydroxy-4,6-dimethylpyrimidine: A visible-light-driven photocatalyst for enhanced ozonation of organic pollutants

The development of durable and highly efficient visible-light-driven photocatalysts is essential for the photocatalytic ozonation process towards degrading organic pollutants. This study presents CN-MA, a novel photocatalyst synthesized by grafting carbon nitride (CN) with single-atom Mn and 2-hydroxy-4,6-dimethylpyrimidine (HDMP) via one-step thermal polymerization. Experimental characterization and theoretical calculation results reveal that incorporating single-atom Mn and HDMP into CN alters the charge density distribution on the heptazine rings. This modification enhances the absorption of visible light and reduces exciton binding energy, leading to improved separation and migration of photogenerated charge carriers. Moreover, the single-atom Mn provides abundant active sites for O 3 adsorption and activation, which increases the utilization of photogenerated electrons to produce highly reactive oxidative species. Consequently, CN-MA exhibits superior photocatalytic ozonation activity, achieving 94% mineralization of phenol within 60 min and maintaining excellent stability over multiple cycles. The research also proposes a plausible reaction mechanism based on free-radical trapping experiments and steady-state concentration experiments using molecular probes. This strategy advances the development of molecular-engineered catalysts co-modified with single metal atoms, thereby enhancing the photocatalytic ozonation process for the degradation of organic pollutants.