Unconventional natural gas production using hydraulic fracturing has unlocked a massive supply of lightweight alkanes (C1-C4). It is desirable to convert low-cost alkanes into higher-value chemicals. The conversion of methane (CH4) is challenging due to its strong C−H bonds. The methane borylation reaction over organometallic catalysts that utilize bis(pinacolborane) is a promising method for activating the methane molecule under mild reaction conditions. Metal-organic frameworks (MOFs) are a class of porous materials that offer a high degree of structural and functional modifiability by the selection of inorganometallic nodes and organic linkers as building blocks and provide a promising way for heterogenization of organometallic catalysts with high activity, selectivity, and improved stability. A new catalyst was synthesized and experimentally examined for methane borylation; the catalyst involves an Ir(III) complex supported on MOF UiO-67 through modified linker groups. MOF UiO-67 is composed of inorganometallic nodes (Zr6(μ3-O)4(μ3-OH)4) and 4,4'-biphenyl dicarboxylate linkers. The newly synthesized complex is found to have excellent chemoselectivity (&gt;99%) for methane borylation to produce monoborylated methane. Density functional theory (DFT) can yield valuable information on the structures and thermodynamics of catalytic materials. In this project, we use DFT calculations to determine the atomic-scale reaction pathway and to verify the steric and confinement effects of the UiO-67 framework for methane borylation over the Ir-based complex. In addition to full DFT calculations, we use combined quantum mechanical and molecular mechanical (QM/MM) methods to facilitate the investigation of the large systems that are computationally less affordable in a full QM calculation. In this way, we can accurately simulate MOFs at a lower cost and thereby make progress toward the rational design of improved catalysts for methane borylation.

Computation study of methane borylation in transition metal functionalized metal-organic frameworks

2019 Spring National Meeting

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