Covalent Organic Framework-Based Photocatalyst for Activation of Peroxymonosulfate: Implications for Degradation of Organic Pollutants

Advanced oxidation processes (AOPs), especially high-efficiency activation of peroxymonosulfate (PMS), have aroused great attention based on their excellent performance along with low toxicity in the degradation of organic pollutants. Although covalent organic frameworks (COFs) have been explored for PMS-activated AOPs, their intrinsic photocatalytic properties are rarely studied in this field. Herein, we designed and prepared a fully conjugated carbon covalent organic framework (TFPT-TCPB COF), which features sp2 C═C linkages, triazine units, and nitrile groups, showing great photocatalytic potential to activation of PMS as an intrinsic photocatalyst. Olefin-linked TFPT-TCPB COF showed much higher removal efficiency (k = 0.048 min–1), 3.5 times the value of rate constant k of TFPT-TAPB COF (k = 0.014 min–1). Meanwhile, the photoactive triazine units endowed the TFPT-TCPB COF with 2.5 times enhancement of the k value than TFPB-TCPB COF embedding only benzene rings (k = 0.013 min–1). Furthermore, the reaction constant k for TFPT-TCPB COF-COOH reached 0.081 min–1, which was 69% higher than that of TFPT-TCPB COF and 27 times higher than that of g-C3N4, proving the positive effects of introducing the hydrophilic carboxyl groups. Also, high chemical stability, reusability, and low biotoxicity offered it an opportunity as a marvelous metal-free photocatalyst for environment remediation.