MOF-derived metal-free N-doped porous carbon mediated peroxydisulfate activation via radical and non-radical pathways: Role of graphitic N and C-O

The development of metal-free catalysts with high activity and stability for persulfate activation draws increasing attention due to their promising performance and environmental benignity. Herein, hierarchically porous nitrogen (N)-doped carbon (N-C) with merits of highly-dispersed nitrogen, large surface area and controllable structure is synthesized. The as-prepared N-C exhibits outstanding performance for peroxydisulfate activation in the degradation of diverse organic pollutants, as well as a wide working pH range of 3-10. Impressively, an annealing strategy can regulate C-O and graphitic N contents in N center dot C and their quantitative correlations with the reaction rate constants reveal that the C-O and graphitic N in N-C are active sites. Furthermore, peroxydisulfate activation by N-C involves with three pathways in which the contribution from radicals (SO4 center dot-, center dot OH) are comparatively weak and non-radical pathways including singlet oxygen (O-1(2)) and electron transfer are dominant. The contribution of O-1(2) is diminishing with delay of reaction while the electron transfer shows the opposite trend. Besides, good recycling performance is achieved by facile re-annealing of N-C. This work provides new insights into the reaction mechanism of persulfate catalysis and can guide future catalyst development in advanced oxidation process.