Ligand‐Regulated Assembly of Cobalt–Porphyrin Metal–Organic Frameworks for Efficient Photocatalytic Singlet Oxygen Generation

ABSTRACT Efficiently modulating intersystem crossing (ISC) to maximize singlet oxygen ( ¹ O ₂ ) generation while simultaneously expanding framework topology remains a significant challenge in porphyrinic metal‐organic framework (PMOF) design. Herein, a ligand‐regulation strategy utilizing a custom‐designed flexible linker, meso‐tetra(4′‐(3‐carboxylphenyl)phenyl)porphyrin (3‐TCBPP) is reported, to construct two novel cobalt–porphyrin frameworks. The extended flexibility of the ligand directs the solvothermal assembly to achieve distinct topological architectures of a 1D chain motif (QPF‐11) and a rare flu topology featuring trinuclear Co ₃ clusters (QPF‐12). Spectroscopic analyses and density functional theory calculations reveal that the paramagnetic Co(II) centers play a pivotal role in optimizing spin dynamics. The open‐shell metal nodes induce substantial metal–porphyrin orbital mixing and reduce the singlet–triplet energy gap, thereby facilitating rapid ISC via spin–orbit coupling. Remarkably, despite their distinct structural dimensions and topologies, both PMOFs exhibit comparable and highly efficient catalytic performance in the photooxidation of 1,5‐dihydroxynaphthalene to juglone. This comparative study reveals that the local electronic configuration of the Co(II) nodes exerts a dominant influence on the photophysical properties, enabling both frameworks to maintain high catalytic efficiency despite their distinct structural topologies. This work provides valuable insights into the structure–property relationships of PMOFs for selective photooxidation.