Well-dispersed cobalt nanoparticles encapsulated on ZIF-8-derived N-doped porous carbon as an excellent peroxymonosulfate activator for sulfamethoxazole degradation

The practical application of carbon materials supported cobalt (Co)-based heterogeneous materials as excellent peroxymonosulfate (PMS) activators has attracted wide attention in recent years because of their low particle self-agglomeration and low Co leaching. Herein, we developed a new synthetic strategy for designing Co nanoparticles (Co NPs)-encapsulated zeolitic imidazolate frameworks-8-derived porous carbon (NC) (denoted as Co-N@NC-x) by calcinating NC with a polydopamine-chelating Co coating. It was demonstrated that NC could effectively prevent Co agglomeration because it provided rich load sites for Co. Raman and X-ray photoelectron spectroscopy results indicated that the addition of Co could increase the surface defects of NC. Co-N@NC-90 (0.1 g/L) efficiently catalyzed PMS to degrade >96.91 % of sulfamethoxazole (SMX, 20 mg/L) within 90 min with an initial pH of 3.65-9.05 based on the synergistic effect between Co NPs and NC. It was demonstrated that Co NPs were the main active sites, and the defects and carbonyl (C=O) group active sites also contributed to SMX degradation by catalyzing PMS. Graphitic N was an adsorption site for SMX. A singlet oxygen (O-1(2))-dominated non-radical mechanism has been proposed. Additionally, Co-N@NC-90 exhibited excellent stability resulting from NC encapsulation. This work provides a novel approach for the application of metal organic framework-derived carbon-supported metal catalysts in wastewater purification.