Reaction Pathways and Microkinetic Modeling of <i>n</i>‑Butane Oxidation to 1‑Butanol on Cu, Cu₃Pd, Pd, Ag₃Pd, and PdZn (111) Surfaces

Density functional theory (DFT) calculations and microkinetic modeling are used to model reactions in the oxidation of <i>n</i>-butane to 1-butanol, 1-butanal, and 1-butene over pure metal and metal alloy (111) surfaces. Specifically, catalytic thermodynamic and kinetic energies are calculated with DFT, and linear scaling relationships are developed that link these values to simpler “descriptors” of catalytic activity. The scaling relationships are used in microkinetic modeling to identify the optimal descriptor values, which maximize the rate and selectivity to 1-butanol. Degree of rate control (DRC) analysis is performed to reveal the catalytic intermediates and transition states that have the greatest influence on the rate. The Cu₃Pd­(111) and Ag₃Pd­(111) surfaces are found to be the most active for <i>n</i>-butane oxidation to 1-butanol, with Cu₃Pd additionally exhibiting high selectivity for 1-butanol. Achieving high activity and selectivity toward 1-butanol is found to require a precise balance of the catalyst affinity for OH* and O*, with catalysts that bind these species too strongly garnering large coverages of O*, which block active sites and inhibit the rate of <i>n</i>-butane conversion, and catalysts that bind these species too weakly promoting dehydrogenation of C₄ species, as this process supplies H atoms that can convert OH* and O* to the more-stable H₂O*. Catalytic affinity for C* is also found to have a significant impact on selectivity toward 1-butanol, since the formation energy of C* on catalyst surfaces is found to correlate to catalytic ability to break C–H bonds, with catalysts that bind C* too strongly tending to overdehydrogenate C₄ species. The reaction C₄H₉* + O* ↔ C₄H₉O* + * is found to be rate-controlling on those catalysts that are most active for 1-butanol production

Optimizing Open Iron Sites in Metal–Organic Frameworks for Ethane Oxidation: A First-Principles Study

Activation of the C–H bonds in ethane to form ethanol is a highly desirable, yet challenging, reaction. Metal–organic frameworks (MOFs) with open Fe sites are promising candidates for catalyzing this reaction. One advantage of MOFs is their modular construction from inorganic nodes and organic linkers, allowing for flexible design and detailed control of properties. In this work, we studied a series of single-metal atom Fe model systems with ligands that are commonly used as MOF linkers and tried to understand how one can design an optimal Fe catalyst. We found linear relationships between the binding enthalpy of oxygen to the Fe sites and common descriptors for catalytic reactions, such as the Fe 3d energy levels in different reaction intermediates. We further analyzed the three highest-barrier steps in the ethane oxidation cycle (including desorption of the product) with the Fe 3d energy levels. Volcano relationships are revealed with peaks toward higher Fe 3d energy and stronger electron-donating group functionalization of linkers. Furthermore, we found that the Fe 3d energy levels positively correlate with the electron-donating strength of functional groups on the linkers. Finally, we validated our hypotheses on larger models of MOF-74 iron sites. Compared with MOF-74, functionalizing the MOF-74 linkers with NH₂ groups lowers the enthalpic barrier for the most endothermic step in the reaction cycle. Our findings provide insight for catalyst optimization and point out directions for future experimental efforts

Review and Analysis of Molecular Simulations of Methane, Hydrogen, and Acetylene Storage in Metal–Organic Frameworks

Review and Analysis of Molecular Simulations of Methane, Hydrogen, and Acetylene Storage in Metal–Organic Framework