Selective Catalytic Olefin Epoxidation with Mn^II-Exchanged MOF-5

Partial substitution of Zn^II by Mn^II in Zn₄O(terephthalate)₃ (MOF-5) leads to a distorted all-oxygen ligand field supporting a single Mn^II site, whose structure was confirmed by Mn K-edge X-ray absorption spectroscopy. The Mn^II ion at the MOF-5 node engages in redox chemistry with a variety of oxidants. With ^tBuSO₂PhIO, it produces a putative Mn^IV-oxo intermediate, which upon further reaction with adventitious hydrogen is trapped as a Mn^III-OH species. Most intriguingly, the intermediacy of the high-spin Mn^IV-oxo species is likely responsible for catalytic activity of the Mn^II-MOF-5 precatalyst, which in the presence of ^tBuSO₂PhIO catalyzes oxygen atom transfer reactivity to form epoxides from cyclic alkenes with >99% selectivity. These results demonstrate that MOF secondary building units serve as competent platforms for accessing terminal high-valent metal-oxo species that consequently engage in catalytic oxygen atom transfer chemistry owing to the relatively weak ligand fields provided by the SBU.