B12X11(H2): exploring the limits of isotopologue selectivity of hydrogen adsorption

Toshiki Wulf, Jonas Warneke, Thomas Heine

Research output: Contribution to journalArticlepeer-review

Abstract

We study the isotopologue-selective binding of dihydrogen at the undercoordinated boron site of B12X11(X = H, F, Cl, Br, I, CN) usingab initioquantum chemistry. With a Gibbs free energy of H2attachment reaching up to 80 kJ mol−1(ΔGat 300 K for X = CN), these sites are even more attractive than most undercoordinated metal centers studied so far. We thus believe that they can serve as an edge case close to the upper limit of isotopologue-selective H2adsorption sites. Differences of the zero-point energy of attachment average 5.0 kJ mol−1between D2and H2and 2.7 kJ mol−1between HD and H2, resulting in hypothetical isotopologue selectivities as high as 2.0 and 1.5, respectively, even at 300 K. Interestingly, even though attachment energies vary substantially according to the chemical nature of X, isotopologue selectivities remain very similar. We find that the H-H activation is so strong that it likely results in the instantaneous heterolytic dissociation of H2in all cases (except, possibly, for X = H), highlighting the extremely electrophilic nature of B12X11despite its negative charge. Unfortunately, this high reactivity also makes B12X11unsuitable for practical application in the field of dihydrogen isotopologue separation. Thus, this example stresses the two-edged nature of strong H2affinity, yielding a higher isotopologue selectivity on the one hand but risking dissociation on the other, and helps define a window of adsorption energies into which a material for selective adsorption near room temperature should ideally fall.

Original languageEnglish
Pages (from-to)28466-28475
Number of pages10
JournalRSC Advances
Volume11
Issue number46
DOIs
Publication statusPublished - 2021 Sep 1

Bibliographical note

Funding Information:
TW thanks the European Social Fund for a PhD fellowship. JW is grateful to a Freigeist Fellowship of the Volkswagen foundation. We thank the Center for Information Services and High Performance Computing (ZIH) at TU Dresden for computational resources.

Publisher Copyright:
© The Royal Society of Chemistry 2021.

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)

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