Exploring complete catalytic cycle of methane oxidation to methanol on Cu2O2 stabilized within MIL-53(Al) framework: A combined DFT and microkinetic study

Although inspiration from copper-based natural enzymes has shown promise in improving catalyst design for methane-to-methanol (MTM) oxidation, high productivity, and selectivity under mild conditions remain a significant challenge. This study constructs the dinuclear copper (Cu₂) species stabilized within the metal-organic framework (MOF), MIL-53(Al), containing Cu as efficient catalytic sites and explores the ability of different oxidants (O₂, N₂O, and H₂O₂) to oxidize Cu₂ into the dicopper-oxo (Cu₂O₂) species using density functional theory (DFT) calculations. Our results indicate the kinetic and thermodynamic favorability of Cu₂O₂ species formation using O₂ as an oxidant within the MIL-53(Al) framework. Furthermore, the thermal stability of Cu₂O₂/MIL-53(Al) has been verified via ab initio molecular dynamics (AIMD) calculations. The kinetics of the complete MTM oxidation cycle over Cu₂O₂/MIL-53(Al) have been studied using both DFT and microkinetic simulation methods. The present study predicts that the C-H activation on the Cu₂O₂/MIL-53(Al) has a low free energy barrier (0.77 eV) and that the high stability of CH₃ and its very low free energy barrier in the C-O coupling step favors the methanol formation over the formaldehyde. More importantly, Cu₂O₂/MIL-53(Al) exhibits high methanol selectivity owing to the inhibition of CH₃ dehydrogenation and low methanol desorption energy (0.21 eV). Microkinetic simulations confirm the methanol production under relatively mild reaction conditions (200–280 K and 1 bar). This work provides insights into the feasibility of selective MTM oxidation over this family of MOF under mild conditions.