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

25 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

ASJC Scopus subject areas

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

Fingerprint Dive into the research topics of 'An important factor in CH<sub>4</sub> activation by Zn ion in comparison with Mg ion in MFI: The superior electron-accepting nature of Zn<sup>2+</sup>'. Together they form a unique fingerprint.

  • Cite this