S-scheme heterojunction fabricated from donor–acceptor COF-R/NVCN photocatalytic degradation of chlorophenols

Visible light-driven degradation of chlorophenols using metal-free photocatalysts has attracted significant attention. Two-dimensional covalent organic frameworks (2D COFs) exhibited high levels of visible-light activity. To address the challenges of insufficient redox capacity and recombination of photogenerated carriers of COFs, an S-scheme heterojunction is constructed from COFs with nitrogen vacancies modified graphitic carbon nitride (NVCN) to improve photocatalytic activity. Introducing electron donors (-OH and -C C) into COF could reduce the optical band gap and increase visible-light absorption. Meanwhile, they can form donor-acceptor (D-A) effects with nitrogen vacancies, thereby redistributing charge and enhancing the transfer rate of photogenerated electrons. Formation of S-scheme heterojunction effectively enhances the migration of photogenerated carriers and redox ability, the optimized heterojunction (COF-C C/NVCN) was able to degrade 98 % 4-chlorophenol within 90 min under visible light irradiation ( k  = 0.044 min –1 ), which was 10–12 times higher than COF-H/NVCN or NVCN. This study provides the great potential of D-A COF/NVCN-based S-scheme heterojunctions for environmental remediation.