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Water and small organic molecules as probes for geometric confinement in well-ordered mesoporous carbon materials

Xu, Y. P. and Watermann, T. and Limbach, H. H. and Gutmann, T. and Sebastiani, D. and Buntkowsky, G. (2014):
Water and small organic molecules as probes for geometric confinement in well-ordered mesoporous carbon materials.
16, In: Physical Chemistry Chemical Physics, (20), pp. 9327-9336, [Online-Edition: http://apps.webofknowledge.com/full_record.do?product=WOS&se...],
[Article]

Abstract

Mesoporous carbon materials were synthesized employing polymers and silica gels as structure directing templates. The basic physico-chemical properties of the synthetic mesoporous materials were characterized by H-1 and C-13 MAS solid-state NMR, X-ray diffraction, transmission electron microscopy (TEM) and nitrogen adsorption measurements. The confinement effects on small guest molecules such as water, benzene and pyridine and their interactions with the pore surface were probed by a combination of variable temperature H-1-MAS NMR and quantum chemical calculations of the magnetic shielding effect of the surface on the solvent molecules. The interactions of the guest molecules depend strongly on the carbonization temperature and the pathway of the synthesis. All the guest-molecules, water, benzene and pyridine, exhibited high-field shifts by the interaction with the surface of carbon materials. The geometric confinement imposed by the surface causes a strong depression of the melting point of the surface phase of water and benzene. The theoretical calculation of H-1 NICS maps shows that the observed proton chemical shifts towards high-field values can be explained as the result of electronic ring currents localized in aromatic groups on the surface. The dependence on the distance between the proton and the aromatic surface can be exploited to estimate the average diameter of the confinement structures.

Item Type: Article
Erschienen: 2014
Creators: Xu, Y. P. and Watermann, T. and Limbach, H. H. and Gutmann, T. and Sebastiani, D. and Buntkowsky, G.
Title: Water and small organic molecules as probes for geometric confinement in well-ordered mesoporous carbon materials
Language: English
Abstract:

Mesoporous carbon materials were synthesized employing polymers and silica gels as structure directing templates. The basic physico-chemical properties of the synthetic mesoporous materials were characterized by H-1 and C-13 MAS solid-state NMR, X-ray diffraction, transmission electron microscopy (TEM) and nitrogen adsorption measurements. The confinement effects on small guest molecules such as water, benzene and pyridine and their interactions with the pore surface were probed by a combination of variable temperature H-1-MAS NMR and quantum chemical calculations of the magnetic shielding effect of the surface on the solvent molecules. The interactions of the guest molecules depend strongly on the carbonization temperature and the pathway of the synthesis. All the guest-molecules, water, benzene and pyridine, exhibited high-field shifts by the interaction with the surface of carbon materials. The geometric confinement imposed by the surface causes a strong depression of the melting point of the surface phase of water and benzene. The theoretical calculation of H-1 NICS maps shows that the observed proton chemical shifts towards high-field values can be explained as the result of electronic ring currents localized in aromatic groups on the surface. The dependence on the distance between the proton and the aromatic surface can be exploited to estimate the average diameter of the confinement structures.

Journal or Publication Title: Physical Chemistry Chemical Physics
Volume: 16
Number: 20
Uncontrolled Keywords: nmr chemical-shifts functional perturbation-theory reporting physisorption data angle-spinning nmr gas solid systems activated carbon response properties magnetic-properties microporous carbon graphite surfaces
Divisions: 07 Department of Chemistry
07 Department of Chemistry > Physical Chemistry
Date Deposited: 27 Oct 2014 20:42
Official URL: http://apps.webofknowledge.com/full_record.do?product=WOS&se...
Additional Information:

Ah0oc Times Cited:1 Cited References Count:78

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