Selective 1O2 Generation from Peroxymonosulfate Activation over N-Doped Carbon Nanosponges for Pollutant Degradation

Recently, carbon-based nanomaterials have attracted significant attention as promising metal-free nanocatalysts for activating persulfates in wastewater treatment via nonradical oxidative pathways (1O2 and electron transfer). Herein, a series of N-doped carbon nanosponges have been designed and synthesized by calcination of organic porphyrins as efficient and metal-free nanocatalysts for activating peroxymonosulfate (PMS) on acid orange 7 (AO7) degradation via a nonradical pathway. In this work, the key point of this strategy is the choice of substituent groups (including –OH, –COOH, and –NO2) on 5,10,15,20-tetraphenylporphyrin (TPP), which could serve both the heteroatom-doped source and the morphological conditioning agent. Further studies reveal that the doping of the N atom in carbon nanosponges could greatly improve their catalytic performance for activating PMS on AO7 degradation by regulating the morphology and physicochemical properties. The quenching tests and EPR analysis verified that 1O2, which contributed to 74.0% of total AO7 degradation, is selectively produced from the TPP-NO2-800/PMS system without any radicals (e.g., SO4•–, O2•–, and HO•). The minor contribution (26.0%) for AO7 elimination is probably attributed to electron transfer between AO7 and PMS.