Confining cobalt sites within the matrix of accordion-like tubular carbon nitride for peroxymonosulfate activation to produce sulfate radicals and desirable singlet oxygen

Carbon nitride (C₃N₄) was fabricated as an accordion-like tubular morphology with hollow interior. The atomically dispersed Co sites were successfully confined within the accordion-like tubular C₃N₄ (atCN) matrix and coordinated with N in the Co-N₄ configuration. The resulting Co-atCN catalysts were employed for peroxymonosulfate (PMS) activation towards 4-chlorophenol (4-CP) degradation. The optimal 2.9Co-atCN/PMS system took merely 10 min to completely degrade 4-CP (k = 0.426 min⁻¹). While the accordion-like tubular C₃N₄ with semi-hollow interior (atCN-sh) was applied, the 2.9Co-atCN-sh/PMS system took 60 min on eliminating barely 72.0 % of 4-CP (k = 0.020 min⁻¹). Moreover, 2.9Co-atCN/PMS exhibited excellent activity on the removal of diverse contaminants, for example, methyl orange (MO), methylene blue (MB), 2,4,6-trichlorophenol (TCP), and acetaminophen (ACT). The 100 % removal efficiency reached within only 5, 45, 45, and 20 min, respectively. In addition, good resistance to environmental interferences was also unveiled in the 2.9Co-atCN/PMS system. Electron paramagnetic resonance (EPR) and quenching tests showed that ^•OH, SO₄^{• −}, O₂^{• −} and ¹O₂ were produced in the reaction system of 2.9Co-atCN/PMS for 4-CP degradation, and the dominant oxygen species were determined to be not only conventional SO₄^{• −} but also favorable ¹O₂, and the latter contributed to the good resistance to environmental disturbances.