Metal-induced balancing of conjugation and planarity in porphyrin-based monomers to construct the highly crystalline covalent organic frameworks with outstanding visible-light catalytic activity

Covalent organic frameworks (COFs) with long-range ordered periodic structures have emerged as promising photocatalysts for advanced oxidation processes. Herein, we reported a highly crystalline porphyrin-based COF (COF-TAP-Cu) featuring outstanding visible-light-driven oxidation activity. COF-TAP-Cu was obtained via a facile bottom-up metallization strategy that tuned the conjugation and planarity of the porphyrin building block (TAP-H). Incorporation of Ni 2+ or Cu 2+ into TAP-H moderately enhanced the π-conjugation of the resulting metalloporphyrin monomers (TAP-M; M = Ni, Cu), leading to markedly improved crystallinity of the corresponding COFs. Notably, structural analysis indicated that the porphyrin ring in TAP-Ni undergoes pronounced distortion, whereas TAP-Cu retained a near-planar geometry. As a result, COF-TAP-Cu exhibited higher crystallinity and superior photocatalytic oxidation performance compared with the metal-free porphyrin-based COFs (COF-TAP-H) and Ni-anchored porphyrin-based COFs (COF-TAP-Ni). Under visible-light irradiation, COF-TAP-Cu efficiently activated molecular oxygen to produce both O 2 •- ( via electron transfer) and 1 O 2 ( via energy transfer), enabling rapid degradation of sulfadiazine (SDZ) with a removal efficiency of up to 95% within 30 min. This work highlighted a monomer-design strategy that balanced conjugation and planarity to construct highly crystalline porphyrin-based COFs, offering new insights for photocatalytic antibiotic remediation in aquatic environments.