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Nanoconfinement of Molecular Magnesium Borohydride Captured in a Bipyridine-Functionalized Metal-Organic Framework

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DOI

  • Andreas Schneemann, Sandia National Laboratories CA
  • ,
  • Liwen F. Wan, Lawrence Livermore National Laboratory
  • ,
  • Andrew S. Lipton, Pacific Northwest National Laboratory
  • ,
  • Yi Sheng Liu, Advanced Light Source, Berkeley
  • ,
  • Jonathan L. Snider, Sandia National Laboratories CA
  • ,
  • Alexander A. Baker, Lawrence Livermore National Laboratory
  • ,
  • Joshua D. Sugar, Sandia National Laboratories CA
  • ,
  • Catalin D. Spataru, Sandia National Laboratories CA
  • ,
  • Jinghua Guo, Advanced Light Source, Berkeley
  • ,
  • Tom S. Autrey, Pacific Northwest National Laboratory
  • ,
  • Mathias Jørgensen, Sandia National Laboratories CA
  • ,
  • Torben R. Jensen
  • Brandon C. Wood, Lawrence Livermore National Laboratory
  • ,
  • Mark D. Allendorf, Sandia National Laboratories CA
  • ,
  • Vitalie Stavila, Sandia National Laboratories CA

The lower limit of metal hydride nanoconfinement is demonstrated through the coordination of a molecular hydride species to binding sites inside the pores of a metal-organic framework (MOF). Magnesium borohydride, which has a high hydrogen capacity, is incorporated into the pores of UiO-67bpy (Zr6O4(OH)4(bpydc)6 with bpydc2- = 2,2'-bipyridine-5,5'-dicarboxylate) by solvent impregnation. The MOF retained its long-range order, and transmission electron microscopy and elemental mapping confirmed the retention of the crystal morphology and revealed a homogeneous distribution of the hydride within the MOF host. Notably, the B-, N-, and Mg-edge XAS data confirm the coordination of Mg(II) to the N atoms of the chelating bipyridine groups. In situ11B MAS NMR studies helped elucidate the reaction mechanism and revealed that complete hydrogen release from Mg(BH4)2 occurs as low as 200 °C. Sieverts and thermogravimetric measurements indicate an increase in the rate of hydrogen release, with the onset of hydrogen desorption as low as 120 °C, which is approximately 150 °C lower than that of the bulk material. Furthermore, density functional theory calculations support the improved dehydrogenation properties and confirm the drastically lower activation energy for B-H bond dissociation.

OriginalsprogEngelsk
TidsskriftACS Nano
Vol/bind14
Nummer8
Sider (fra-til)10294-10304
Antal sider11
ISSN1936-0851
DOI
StatusUdgivet - aug. 2020

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