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

• Accordion-like tubular carbon nitride was fabricated to immobilize atomically dispersed Co. • The resultant Co- at CN efficiently removed 4-chlorophenol via triggering peroxymonosulfate. • The Co- at CN/PMS system exhibited good tolerance to environmental interferences. • The decent performance was benefited from dominant roles of 1 O 2 and SO 4 • − during the degradation. Carbon nitride (C 3 N 4 ) was fabricated as an accordion-like tubular morphology with hollow interior. The atomically dispersed Co sites were successfully confined within the accordion-like tubular C 3 N 4 ( at CN) matrix and coordinated with N in the Co-N 4 configuration. The resulting Co- at CN catalysts were employed for peroxymonosulfate (PMS) activation towards 4-chlorophenol (4-CP) degradation. The optimal 2.9Co- at CN/PMS system took merely 10 min to completely degrade 4-CP ( k = 0.426 min −1 ). While the accordion-like tubular C 3 N 4 with semi-hollow interior ( at CN-sh) was applied, the 2.9Co- at CN-sh/PMS system took 60 min on eliminating barely 72.0 % of 4-CP ( k = 0.020 min −1 ). Moreover, 2.9Co- at CN/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- at CN/PMS system. Electron paramagnetic resonance (EPR) and quenching tests showed that • OH, SO 4 • − , O 2 • − and 1 O 2 were produced in the reaction system of 2.9Co- at CN/PMS for 4-CP degradation, and the dominant oxygen species were determined to be not only conventional SO 4 • − but also favorable 1 O 2 , and the latter contributed to the good resistance to environmental disturbances.