Abstract The development of efficient heterostructures combining covalent organic frameworks (COFs) and ideal semiconductors can significantly improve photocatalytic performance for pollutant degradation. Herein, we present the design, synthesis, and characterization of a core‐shell‐structured nanocomposite comprising covalent triazine framework‐encased Fe 3 O 4 magnetic particles employed as a heterojunction photocatalyst for activating peroxymonosulfate (PMS) in phenol degradation. The distinctive internal structure between the TpMa shell (Tp=2,4,6‐trihydroxy‐1,3,5‐benzenetricarboxaldehyde, Ma=melamine) and the Fe 3 O 4 core (Fe 3 O 4 @TpMa) facilitated charge transfer and accelerated charge separation. Furthermore, PMS served as an electron acceptor, enhancing photogenerated charge separation and maximizing the production of reactive oxygen species. The Fe 3 O 4 @TpMa/PMS system demonstrated remarkable photocatalytic performance and stability, achieving complete phenol degradation (10 mg L −1 ) in 40 min. The exceptional photocatalytic activity resulted from the synergistic effect of ⋅OH, SO 4 ⋅ − , O 2 ⋅ − , 1 O 2 , and h + generated in the Fe 3 O 4 @TpMa/PMS system during the degradation process. Overall, this material offers excellent potential for solar‐driven pollutant degradation and enables the development of COF‐based materials for wastewater treatment applications.