We report the low-temperature catalytic reactivity of Zn+ ions confined in ZSM-5 zeolite toward CO oxidation. In situ DRIFT and ESR spectroscopy demonstrated that molecular O-2 is readily activated by Zn+ ion to produce O-2(-) species at room temperature (298 K) via facile electron transfer between Zn+ ion and O-2 and that the formation of the active O-2(-) species is responsible for the high activity of the ZnZSM-5 catalyst toward CO oxidation.