Ghent University Academic Bibliography

Advanced

Water coordination and dehydration processes in defective UiO-66 type metal organic frameworks

Matthias Vandichel, Julianna Hajek UGent, An Ghysels UGent, Arthur De Vos UGent, Michel Waroquier UGent and Veronique Van Speybroeck UGent (2016) CRYSTENGCOMM. 18(37). p.7056-7069
abstract
The UiO-66 metal organic framework is one of the most thermally and chemically stable hybrid materials reported to date. However, it is also accepted that the material contains structurally embedded defects, which may be engineered to enhance properties towards specific applications such as catalysis, sensing, etc. The synthesis conditions determine to a large extent the level of perfection of the material and additionally the catalytic activity may be enhanced by post-synthesis activation at high temperature under vacuum, in which defect coordinating species (H2O, HCl, monocarboxylic modulators, etc.) evaporate. The molecular level characterization of defects is extremely challenging from both theoretical and experimental points of view. Such experimental endeavor was recently proposed via experimental SXRD measurements, also unraveling the coordination of water on the Zr-O-Zr defect sites [Angew. Chem., Int. Ed., 2015, 54, 11162-11167]. The present work provides a theoretical understanding of defect structures in UiO-66(Zr) by means of periodic density functional theory calculations and ab initio molecular dynamics simulations. A range of defect structures are generated with different numbers of missing linkers. For each of the defects, the free energetic and mechanical stability is discussed and the coordination of water and charge balancing hydroxide ions is studied. For catalysis applications, the material is mostly pretreated to remove water by dehydration reactions. For each of the proposed defect structures, mechanistic pathways for dehydration reactions of the Zr-bricks are determined employing nudged elastic band (NEB) calculations. During the dehydroxylation trajectory, loose hydroxyl groups and terephthalate decoordinations are observed. Furthermore, dehydration reactions are lower activated if terephthalate linkers are missing in the immediate environment of the inorganic brick. The creation of defects and the dehydration processes have a large impact on the mechanical properties of the material, which is evidenced by lower bulk moduli and elastic constants for structures with more defects.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
SINGLE-CRYSTAL, WAVE BASIS-SET, CATALYTIC PERFORMANCE, VANADIUM MIL-47, DENSITY, CYCLOHEXENE, TRANSITION, ATOMIC LAYER DEPOSITION, TOTAL-ENERGY CALCULATIONS, INITIO MOLECULAR-DYNAMICS
journal title
CRYSTENGCOMM
CrystEngComm
volume
18
issue
37
pages
7056 - 7069
Web of Science type
Article
Web of Science id
000384465500012
JCR category
CRYSTALLOGRAPHY
JCR impact factor
3.474 (2016)
JCR rank
5/26 (2016)
JCR quartile
1 (2016)
ISSN
1466-8033
DOI
10.1039/c6ce01027j
language
English
UGent publication?
yes
classification
A1
copyright statement
I have transferred the copyright for this publication to the publisher
id
8157765
handle
http://hdl.handle.net/1854/LU-8157765
date created
2016-11-17 15:07:43
date last changed
2017-10-03 13:48:20
@article{8157765,
  abstract     = {The UiO-66 metal organic framework is one of the most thermally and chemically stable hybrid materials reported to date. However, it is also accepted that the material contains structurally embedded defects, which may be engineered to enhance properties towards specific applications such as catalysis, sensing, etc. The synthesis conditions determine to a large extent the level of perfection of the material and additionally the catalytic activity may be enhanced by post-synthesis activation at high temperature under vacuum, in which defect coordinating species (H2O, HCl, monocarboxylic modulators, etc.) evaporate. The molecular level characterization of defects is extremely challenging from both theoretical and experimental points of view. Such experimental endeavor was recently proposed via experimental SXRD measurements, also unraveling the coordination of water on the Zr-O-Zr defect sites [Angew. Chem., Int. Ed., 2015, 54, 11162-11167]. The present work provides a theoretical understanding of defect structures in UiO-66(Zr) by means of periodic density functional theory calculations and ab initio molecular dynamics simulations. A range of defect structures are generated with different numbers of missing linkers. For each of the defects, the free energetic and mechanical stability is discussed and the coordination of water and charge balancing hydroxide ions is studied. For catalysis applications, the material is mostly pretreated to remove water by dehydration reactions. For each of the proposed defect structures, mechanistic pathways for dehydration reactions of the Zr-bricks are determined employing nudged elastic band (NEB) calculations. During the dehydroxylation trajectory, loose hydroxyl groups and terephthalate decoordinations are observed. Furthermore, dehydration reactions are lower activated if terephthalate linkers are missing in the immediate environment of the inorganic brick. The creation of defects and the dehydration processes have a large impact on the mechanical properties of the material, which is evidenced by lower bulk moduli and elastic constants for structures with more defects.},
  author       = {Vandichel, Matthias and Hajek, Julianna and Ghysels, An and De Vos, Arthur and Waroquier, Michel and Van Speybroeck, Veronique},
  issn         = {1466-8033},
  journal      = {CRYSTENGCOMM},
  keyword      = {SINGLE-CRYSTAL,WAVE BASIS-SET,CATALYTIC PERFORMANCE,VANADIUM MIL-47,DENSITY,CYCLOHEXENE,TRANSITION,ATOMIC LAYER DEPOSITION,TOTAL-ENERGY CALCULATIONS,INITIO MOLECULAR-DYNAMICS},
  language     = {eng},
  number       = {37},
  pages        = {7056--7069},
  title        = {Water coordination and dehydration processes in defective UiO-66 type metal organic frameworks},
  url          = {http://dx.doi.org/10.1039/c6ce01027j},
  volume       = {18},
  year         = {2016},
}

Chicago
Vandichel, Matthias, Julianna Hajek, An Ghysels, Arthur De Vos, Michel Waroquier, and Veronique Van Speybroeck. 2016. “Water Coordination and Dehydration Processes in Defective UiO-66 Type Metal Organic Frameworks.” Crystengcomm 18 (37): 7056–7069.
APA
Vandichel, M., Hajek, J., Ghysels, A., De Vos, A., Waroquier, M., & Van Speybroeck, V. (2016). Water coordination and dehydration processes in defective UiO-66 type metal organic frameworks. CRYSTENGCOMM, 18(37), 7056–7069.
Vancouver
1.
Vandichel M, Hajek J, Ghysels A, De Vos A, Waroquier M, Van Speybroeck V. Water coordination and dehydration processes in defective UiO-66 type metal organic frameworks. CRYSTENGCOMM. 2016;18(37):7056–69.
MLA
Vandichel, Matthias, Julianna Hajek, An Ghysels, et al. “Water Coordination and Dehydration Processes in Defective UiO-66 Type Metal Organic Frameworks.” CRYSTENGCOMM 18.37 (2016): 7056–7069. Print.