Multiscale Model for a Metal-Organic Framework: High-Spin Rebound Mechanism in the Reaction of the Oxoiron(IV) Species of Fe-MOF-74

We performed ONIOM QM/MM calculations to understand how ethane is hydroxylated and ethanol is converted to acetaldehyde by an oxoiron(IV) species generated within an iron-containing metal organic framework called Fe-MOF-74. The calculations showed that the ethane hydroxylation proceeds via a high-spin rebound mechanism. The conversion of ethanol into acetaldehyde should occur more favorably via H-abstraction from the O-H bond than via C-H cleavage, although the O-H bond of ethanol is stronger than the C(1)-H bond. This trend can be rationalized by the effect of proton-coupled electron transfer, which stabilizes the transition state for O-H cleavage.