---
_id: '63920'
abstract:
- lang: eng
  text: Coordinatively unsaturated sites (CUS) present a key feature of alumina based
    catalysts as they are believed to act as Lewis-acid sites in heterogeneously catalyzed
    reactions. In the present study, the direct observation of active species on a
    fluoride-doped aluminum oxide catalyst is demonstrated. This new fluoride-doped
    aluminum oxide exhibits strong Lewis-acid sites and superior catalytic activity
    as compared to gamma-Al2O3. To emphasize the labile state of Lewis-acid sites,
    two distinctive states of the catalysts surface are addressed using H-1-Al-27
    cross polarization (CP) MAS NMR. On the one hand, the highly dehydrated and active
    state after calcination at 700 degrees C and on the other hand the rehydrated
    and catalytically inactive surface (produced by contact to air) are probed. These
    experiments revealed the presence of significant amounts of coordinatively unsaturated
    sites in the form of 4-and 5-fold coordinated Al-sites on the highly dehydrated
    surface. In contrast to this, the rehydrated sample exhibited a severely restructured
    surface caused by the chemisorption of H2O which is ’constituted in a manner that
    was proposed in earlier models for gamma-Al2O3 surfaces.
author:
- first_name: L.
  full_name: Ahrem, L.
  last_name: Ahrem
- first_name: G.
  full_name: Scholz, G.
  last_name: Scholz
- first_name: Torsten
  full_name: Gutmann, Torsten
  id: '118165'
  last_name: Gutmann
- first_name: B.
  full_name: Calvo, B.
  last_name: Calvo
- first_name: G.
  full_name: Buntkowsky, G.
  last_name: Buntkowsky
- first_name: E.
  full_name: Kemnitz, E.
  last_name: Kemnitz
citation:
  ama: Ahrem L, Scholz G, Gutmann T, Calvo B, Buntkowsky G, Kemnitz E. Direct Observation
    of Coordinatively Unsaturated Sites on the Surface of a Fluoride-Doped Alumina
    Catalyst. <i>Journal of Physical Chemistry C</i>. 2017;121(22):12206–12213. doi:<a
    href="https://doi.org/10.1021/acs.jpcc.7b02535">10.1021/acs.jpcc.7b02535</a>
  apa: Ahrem, L., Scholz, G., Gutmann, T., Calvo, B., Buntkowsky, G., &#38; Kemnitz,
    E. (2017). Direct Observation of Coordinatively Unsaturated Sites on the Surface
    of a Fluoride-Doped Alumina Catalyst. <i>Journal of Physical Chemistry C</i>,
    <i>121</i>(22), 12206–12213. <a href="https://doi.org/10.1021/acs.jpcc.7b02535">https://doi.org/10.1021/acs.jpcc.7b02535</a>
  bibtex: '@article{Ahrem_Scholz_Gutmann_Calvo_Buntkowsky_Kemnitz_2017, title={Direct
    Observation of Coordinatively Unsaturated Sites on the Surface of a Fluoride-Doped
    Alumina Catalyst}, volume={121}, DOI={<a href="https://doi.org/10.1021/acs.jpcc.7b02535">10.1021/acs.jpcc.7b02535</a>},
    number={22}, journal={Journal of Physical Chemistry C}, author={Ahrem, L. and
    Scholz, G. and Gutmann, Torsten and Calvo, B. and Buntkowsky, G. and Kemnitz,
    E.}, year={2017}, pages={12206–12213} }'
  chicago: 'Ahrem, L., G. Scholz, Torsten Gutmann, B. Calvo, G. Buntkowsky, and E.
    Kemnitz. “Direct Observation of Coordinatively Unsaturated Sites on the Surface
    of a Fluoride-Doped Alumina Catalyst.” <i>Journal of Physical Chemistry C</i>
    121, no. 22 (2017): 12206–12213. <a href="https://doi.org/10.1021/acs.jpcc.7b02535">https://doi.org/10.1021/acs.jpcc.7b02535</a>.'
  ieee: 'L. Ahrem, G. Scholz, T. Gutmann, B. Calvo, G. Buntkowsky, and E. Kemnitz,
    “Direct Observation of Coordinatively Unsaturated Sites on the Surface of a Fluoride-Doped
    Alumina Catalyst,” <i>Journal of Physical Chemistry C</i>, vol. 121, no. 22, pp.
    12206–12213, 2017, doi: <a href="https://doi.org/10.1021/acs.jpcc.7b02535">10.1021/acs.jpcc.7b02535</a>.'
  mla: Ahrem, L., et al. “Direct Observation of Coordinatively Unsaturated Sites on
    the Surface of a Fluoride-Doped Alumina Catalyst.” <i>Journal of Physical Chemistry
    C</i>, vol. 121, no. 22, 2017, pp. 12206–12213, doi:<a href="https://doi.org/10.1021/acs.jpcc.7b02535">10.1021/acs.jpcc.7b02535</a>.
  short: L. Ahrem, G. Scholz, T. Gutmann, B. Calvo, G. Buntkowsky, E. Kemnitz, Journal
    of Physical Chemistry C 121 (2017) 12206–12213.
date_created: 2026-02-07T08:56:18Z
date_updated: 2026-02-17T16:19:24Z
doi: 10.1021/acs.jpcc.7b02535
extern: '1'
intvolume: '       121'
issue: '22'
keyword:
- al-27 nmr
- characterization
- Chemistry
- cross-polarization
- dynamic nuclear-polarization
- eta-alumina
- gamma-alumina
- hydroxy fluorides
- ions
- Materials Science
- pentacoordinated al3+
- Science & Technology - Other Topics
- solid-state nmr
- spectroscopic
- structural insights
language:
- iso: eng
page: 12206–12213
publication: Journal of Physical Chemistry C
publication_identifier:
  issn:
  - 1932-7447
status: public
title: Direct Observation of Coordinatively Unsaturated Sites on the Surface of a
  Fluoride-Doped Alumina Catalyst
type: journal_article
user_id: '100715'
volume: 121
year: '2017'
...