An important factor in CH4 activation by Zn ion in comparison with Mg ion in MFI

The superior electron-accepting nature of Zn2+

Akira Oda, Hiroe Torigoe, Atsushi Itadani, Takahiro Ohkubo, Takashi Yumura, Hisayoshi Kobayashi, Yasushige Kuroda

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

We present clear IR and density functional theory (DFT) evidence demonstrating that the electron-accepting nature of Zn2+ ion exchanged in MFI-type zeolite (ZnMFI) plays a dominant role in CH4 activation. The IR study revealed that the heterolytic dissociation of CH 4 takes place on the Zn2+ ion exchanged in MFI under a CH4 atmosphere even near room temperature, whereas a similar reaction scarcely occurred on Mg2+ ion exchanged in MFI, although the ionic radius and charge of Mg2+ are almost the same as those of Zn 2+. These data indicate that the dissociation reaction of CH 4 on Zn2+ in MFI is facilitated not only by the electrostatic interaction but also by the electron-transfer interaction. This interpretation was clearly evidenced by the observed v1 mode of the C-H symmetric stretching vibration, i.e., a larger band shift toward lower wavenumbers, for the molecular CH4 adsorbed on ZnMFI, compared with those for a gaseous CH4 molecule. Additional experiments were also performed by the IR method utilizing CO as a probe molecule that has an electron-donating nature. All experimental data presented were successfully explained in terms of the superior electron-accepting nature of Zn2+ exchanged in MFI. Furthermore, the DFT calculation method completely explained all experimental data by adopting the M7S2 model, which was truncated from the ZnMFI structure; the electron-accepting nature is dominant in the heterolytic activation of CH4 in the Zn2+ ion in MFI in comparison with that of Mg2+ exchanged at the same site. We have thus shown that the electron-transfer interaction between Zn2+ and CH4 plays a key role in the heterolytic CH4 activation process: the σ donation from the σ(C-H) orbital of CH4 toward the Zn 4s orbital through overlapping with each orbital.

Original languageEnglish
Pages (from-to)15234-15241
Number of pages8
JournalJournal of Physical Chemistry C
Volume118
Issue number28
DOIs
Publication statusPublished - Jul 17 2014

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Chemical activation
activation
Ions
Electrons
orbitals
electron transfer
ions
electrons
dissociation
methylidyne
density functional theory
Density functional theory
interactions
Zeolites
molecules
Molecules
Carbon Monoxide
electrostatics
Coulomb interactions
atmospheres

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

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An important factor in CH4 activation by Zn ion in comparison with Mg ion in MFI : The superior electron-accepting nature of Zn2+. / Oda, Akira; Torigoe, Hiroe; Itadani, Atsushi; Ohkubo, Takahiro; Yumura, Takashi; Kobayashi, Hisayoshi; Kuroda, Yasushige.

In: Journal of Physical Chemistry C, Vol. 118, No. 28, 17.07.2014, p. 15234-15241.

Research output: Contribution to journalArticle

Oda, Akira ; Torigoe, Hiroe ; Itadani, Atsushi ; Ohkubo, Takahiro ; Yumura, Takashi ; Kobayashi, Hisayoshi ; Kuroda, Yasushige. / An important factor in CH4 activation by Zn ion in comparison with Mg ion in MFI : The superior electron-accepting nature of Zn2+. In: Journal of Physical Chemistry C. 2014 ; Vol. 118, No. 28. pp. 15234-15241.
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abstract = "We present clear IR and density functional theory (DFT) evidence demonstrating that the electron-accepting nature of Zn2+ ion exchanged in MFI-type zeolite (ZnMFI) plays a dominant role in CH4 activation. The IR study revealed that the heterolytic dissociation of CH 4 takes place on the Zn2+ ion exchanged in MFI under a CH4 atmosphere even near room temperature, whereas a similar reaction scarcely occurred on Mg2+ ion exchanged in MFI, although the ionic radius and charge of Mg2+ are almost the same as those of Zn 2+. These data indicate that the dissociation reaction of CH 4 on Zn2+ in MFI is facilitated not only by the electrostatic interaction but also by the electron-transfer interaction. This interpretation was clearly evidenced by the observed v1 mode of the C-H symmetric stretching vibration, i.e., a larger band shift toward lower wavenumbers, for the molecular CH4 adsorbed on ZnMFI, compared with those for a gaseous CH4 molecule. Additional experiments were also performed by the IR method utilizing CO as a probe molecule that has an electron-donating nature. All experimental data presented were successfully explained in terms of the superior electron-accepting nature of Zn2+ exchanged in MFI. Furthermore, the DFT calculation method completely explained all experimental data by adopting the M7S2 model, which was truncated from the ZnMFI structure; the electron-accepting nature is dominant in the heterolytic activation of CH4 in the Zn2+ ion in MFI in comparison with that of Mg2+ exchanged at the same site. We have thus shown that the electron-transfer interaction between Zn2+ and CH4 plays a key role in the heterolytic CH4 activation process: the σ donation from the σ(C-H) orbital of CH4 toward the Zn 4s orbital through overlapping with each orbital.",
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