Nickel single atoms anchored on a bipyridine-based covalent organic framework: boosting active sites for photodegradation of acetaminophen

It remains crucial but challenging to construct single-atom photocatalysts based on covalent organic framework (COF) materials in a simple, fast, and controllable manner and to clarify their structure-efficacy relationship. Here, a single-atom photocatalyst (Ni-TpBpy) featuring atomically dispersed Ni sites with a high loading content and a specific tetra-coordinated N₂-Ni-Cl₂ environment in a bipyridine-based COF was for the first time rapidly synthesized using dielectric barrier discharge (DBD) plasma and a wet chemical method. Visible light-driven Ni-TpBpy can achieve 97.8% photodegradation efficiency of acetaminophen at 0.177 min^-1 in 30 min, outperforming other advanced photocatalysts. Experimental studies and density-functional theory (DFT) calculation clarified the role of well-dispersed Ni active sites in enhanced photodegradation, which not only narrowed the bandgap, facilitating carrier separation and migration, but also promoted the generation of reactive superoxide radicals. This study represents the first use of single-atom Ni-TpBpy in the efficient photocatalytic degradation of emerging pollutants with remarkable stability and universality, bringing new insights into the application of COF-based single-atom materials in environmental remediation.