Computational Discovery of Stable Metal-Organic Frameworks for Methane-to-Methanol Catalysis

The challenge of direct partial oxidation of methaneto methanolhas motivated the targeted search of metal-organic frameworks(MOFs) as a promising class of materials for this transformation becauseof their site-isolated metals with tunable ligand environments. Thousandsof MOFs have been synthesized, yet relatively few have been screenedfor their promise in methane conversion. We developed a high-throughputvirtual screening workflow that identifies MOFs from a diverse spaceof experimental MOFs that have not been studied for catalysis, yetare thermally stable, synthesizable, and have promising unsaturatedmetal sites for C-H activation via a terminal metal-oxo species.We carried out density functional theory calculations of the radicalrebound mechanism for methane-to-methanol conversion on models ofthe secondary building units (SBUs) from 87 selected MOFs. While weshowed that oxo formation favorability decreases with increasing 3dfilling, consistent with prior work, previously observed scaling relationsbetween oxo formation and hydrogen atom transfer (HAT) are disruptedby the greater diversity in our MOF set. Accordingly, we focused onMn MOFs, which favor oxo intermediates without disfavoring HAT orleading to high methanol release energies a key feature formethane hydroxylation activity. We identified three Mn MOFs comprisingunsaturated Mn centers bound to weak-field carboxylate ligands inplanar or bent geometries with promising methane-to-methanol kineticsand thermodynamics. The energetic spans of these MOFs are indicativeof promising turnover frequencies for methane to methanol that warrantfurther experimental catalytic studies.

Automated summary

The study focuses on the direct partial oxidation of methane to methanol using metal-organic frameworks (MOFs). By developing a high-throughput virtual screening workflow, researchers identified three promising Mn MOFs for methane-to-methanol conversion. These MOFs exhibit favorable kinetics and thermodynamics, indicating their potential for further experimental catalytic studies.