Molecular engineering modulated electronic structure of carbon nitride boosting nonradical dominated PMS activation for efficient organic pollutant degradation

Abstract

Nonradical-dominated persulfate oxidation reactions on polymeric carbon nitride (PCN) have received increasing attention for the removal of organic pollutants, yet are severely hampered by the irregular movement and rapid recombination of charge carriers. Herein, benzothiazole (BT) and benzimidazole (BM) were grafted onto the edges of PCN to modulate their electronic structure for efficient peroxymonosulfate (PMS) activation. Experimental and theoretical analysis demonstrate that BT and BM units as electron donors not only significantly enhances light absorption, but also facilitates directional charge transport. Besides, the more favorable PMS adsorption by CN-BT and CN-BM compared to PCN further promote electron transfer. Interestingly, the BM unit with stronger electron-donating capacity endow CN-BM with faster carrier separation and more efficient PMS activation. More importantly, the PMS on the CN-BM surface could form metastable CN-BM/PMS* surface complex with enhanced oxidation properties, significantly facilitating the nonradical oxidation of BPA. Accordingly, the CN-BM/PMS/vis system exhibits the highest reaction kinetic constants (0.31 min⁻¹) for BPA degradation, which is 5.2 times higher than that of the PCN/PMS/vis system (0.06 min⁻¹). This work provides new guidance for molecular engineering on carbon nitride and insights into water purification.