Single-Atom-Modulated Reactive Oxygen Species Generation and Network Crosslinking in Porphyrin-Based Metallacages for Selective Photocatalysis

Precise control over the photocatalytic selectivity by single atoms is ubiquitous in natural systems but remains a formidable challenge for artificial photocatalysts. Here, we present a series of porphyrin-based metallacages with nearly identical architectures that differ only in the central metal atoms (Co, Ni, Cu, and Zn) of the porphyrin ligands. The distinct d-orbital electron distribution of these metal centers governs ligand-to-metal charge transfer, resulting in divergent reactive oxygen species (ROS) generation pathways. The Co–porphyrin cage promotes electron transfer to produce superoxide anion (O₂^•−), whereas the Zn–porphyrin cage favors energy transfer to generate singlet oxygen (¹O₂); Ni- and Cu-porphyrin cages exhibit dual behavior. These variations lead to distinct oxidation selectivity of α-terpinene, yielding either p-cymene (via O₂^•−) or ascaridole (via ¹O₂). Moreover, secondary coordination between the porphyrin metals and poly(4-vinylpyridine) affords robust supramolecular networks for heterogeneous catalysis with enhanced stability and recyclability. This study establishes single-atom modulation within metallacage frameworks as an effective strategy to control ROS generation and photocatalytic selectivity, paving the way toward the practical applications of metallacage-based photocatalytic systems.