Probing Adsorption Interactions In Metal-Organic Frameworks Using X-ray Spectroscopy and Density Functional Theory

ORAL

Abstract

Metal-organic frameworks (MOFs) are currently among the most promising materials for gas separation applications such as carbon capture. We explore the local electronic signatures of molecular adsorption at coordinatively unsaturated binding sites in the metal-organic framework Mg-MOF-74 using X-ray spectroscopy and first principles calculations. \textit{In situ} measurements at the Mg $K$-edge reveal distinct pre-edge absorption features associated with the unique, open coordination of the Mg sites. These spectral features are suppressed upon adsorption of CO$_{2}$ and $N,N'$-dimethylformamide. Density functional theory shows that these spectral changes arise from modifications of local symmetry around the Mg sites upon gas uptake and are strongly dependent on the metal-adsorbate binding strength. Similar sensitivity to local symmetry is expected for any open metal site, making X-ray spectroscopy an ideal tool for examining adsorption in such MOFs.

*This work was supported by the Center for Gas Separations Relevant to Clean Energy Technologies, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001015

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Authors

  • Walter Drisdell

    • Lawrence Berkeley National Laboratory

  • Roberta Poloni

    • SIMAP, laboratoire de Recherche sur les Mat\'eriaux, Grenoble

  • Thomas McDonald

    • University of California, Berkeley

  • Jeffrey Long

    • University of California, Berkeley

  • Berend Smit

    • Dept. of Chemical and Biomolecular Engineering, University of California, Berkeley; Materials Sciences Division, LBNL
    • University of California, Berkeley

  • Jeffery B. Neaton

    • Department of Physics, UC-Berkeley; Molecular Foundry, LBNL
    • Molecular Foundry, LBNL, Department of Physics, UC Berkeley
    • Molecular Foundry, LBNL and Dept. Physics, UC Berkeley
    • Molecular Foundry, Lawrence Berkeley National Laboratory and Department of Physics, University of California, Berkeley
    • UC Berkeley, Dept of Physics; Materials Science Division, LBNL
    • Molecular Foundry, Lawrence Berkeley National Laboratory; Department of Physics, UC-Berkeley
    • The Molecular Foundry, LBNL; Dept. of Physics, University of California, Berkeley
    • Lawrence Berkeley National Laboratory
    • UC Berkeley Department of Physics
    • Lawrence Berkeley Natl Lab and Department of Physics, UC-Berkeley
    • Physics Department, UC Berkeley; Molecular Foundry, Lawrence Berkeley National Lab

  • David Prendergast

    • Lawrence Berkeley National Laboratory
    • The Molecular Foundry, Lawrence Berkeley National Laboratory
    • Lawrence Berkeley National Lab

  • Jeffrey Kortright

    • Lawrence Berkeley National Laboratory