Mn–N coordination-induced interfacial electron enrichment on g-C3N4 nanosheets for enhanced peroxymonosulfate activation via dual reactive oxygen species pathways

Graphitic carbon nitride (g-C 3 N 4 ), featuring high chemical stability, structural tunability, and a nitrogen-rich framework, is an attractive support for heterogeneous peroxymonosulfate (PMS) activation. However, its catalytic performance is often limited by insufficient accessible active sites and sluggish interfacial electron transfer. Herein, we report a 2-methylimidazole (2-MI)-assisted pre-assembly strategy for constructing curled Mn-modified carbon nitride nanosheets (Mn/CN) via supramolecular precursor regulation followed by thermal polycondensation. Structural characterizations indicate that Mn species are highly dispersed in the carbon nitride matrix and likely form Mn–N X -coordinated environments, which induce local electron redistribution and generate interfacial electron-enriched features. Coupled with the curled nanosheet architecture and enhanced accessible surface area, these structural and electronic merits facilitate PMS adsorption/activation and accelerate interfacial electron transfer. Electron paramagnetic resonance and quenching experiments demonstrate that both radical and non-radical pathways contribute to the Mn/CN/PMS system, in which 1 O 2 and O 2 •− are the dominant reactive oxygen species, while SO 4 •− and •OH play auxiliary roles. As a result, the optimized Mn/CN catalyst exhibits efficient RhB degradation, good reusability, and wide pH adaptability. This work provides a feasible strategy for the construction of highly dispersed Mn–N X -modified carbon nitride catalysts and offers insight into interfacial electronic regulation for efficient PMS-based wastewater treatment.