Dynamic inner-outer dual-cycles drive selective periodate activation for nearly exclusive singlet oxygen production toward sustainable water purification.

Selective singlet oxygen (1O2) generation via periodate (PI) activation is constrained by radical-mediated competition and insufficient endogenous electron supply at metal centers. Herein, we report a spatially partitioned inner-outer dual-cycle catalytic system, consisting of nitrogen-doped carbon-confined zero-valent cobalt core encapsulated by a MnO2 shell (Co/NC/MnO2), which achieves 95.93% 1O2 selectivity. The MnO2 shell orchestrates electron redistribution to drive heterolytic I-O cleavage and OO release, effectively suppressing radical pathways without undergoing significant valency change. Simultaneously, the Co° core acts as an embedded electron donor, continuously supplying electrons through the NC interlayer to sustain concurrent Co/Mn redox cycling. This dynamic synergistic coupling drastically accelerates interfacial kinetics, enabling 100% removal of diverse electron-rich contaminants within 10 min. Furthermore, the system demonstrates outstanding operational stability over 192 h in a continuous-flow reaction, while life cycle assessment (LCA) confirms its low environmental footprint. This work introduces a new architectural paradigm for selective 1O2 production via the inner-outer cycle concept and inspires advanced synergistic dual-site engineering for sustainable water purification.