Quantum Chemical Characterization of Structural Single Fe(II) Sites in MIL-Type Metal-Organic Frameworks for the Oxidation of Methane to Methanol and Ethane to Ethanol

Single non-heme Fe(II) ions present as structural moieties in several metal-organic frameworks (e.g., MIL-100, MIL-101, and MIL-808, where MIL indicates Materials of Institute Lavoisier) are identified by Kohn-Sham density functional calculations as promising catalysts for C-H bond activation, with energetic barriers as low as 40 kJ mol^-1 for ethane and 60 kJ mol^-1 for methane following the oxidative activation of iron. The rate-determining step is the activation of N₂O and has a barrier of 140 kJ mol^-1. Through consideration of the full reaction profile leading to the corresponding alcohols, ethanol and methanol, we have identified key changes in the chemical composition of the node that would modulate catalytic activity. The thermal and chemical stabilities of these materials, together with the scalability of their syntheses, make them attractive catalysts for the selective low-temperature conversion of light alkanes to higher-value oxygenates.