Phenothiazine derivatives have attracted tremendous research attention due to their rich redox-active properties. In this work, a phenothiazine-based, highly crystalline, and two-dimensional covalent organic framework (PTz-An-COF) was developed. PTz-An-COF exhibited a low bandgap of 1.92 eV with a broad visible-light absorption. Interestingly, PTz-An-COF can serve as an efficient photoinitiator for visible-light-induced radical polymerization of methyl acrylate. Remarkably, PTz-An-COF as a photoinitiator can be easily recycled and maintains the same catalytic activity as that of pristine PTz-An-COF. This work provides new insights into the development of high-performance heterogeneous photocatalysts for radical polymerization.