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Access Molecular Mobility in High-Tec
Nanoporous Materials by NMR
Frank Stallmach, Tobias Splith, Carsten Horch,
Anne-Kristin Pusch
University of Leipzig
Faculty of Physics and Earth Sciences
Institute for Experimental Physics I
Dept. Physics of Interfaces
Web: http://www.uni-leipzig.de/~gfp/research
Motivation
Transport and storage of fluids in porous materials is a
topic encountered in many branches of science and
engineering [1].
NMR studies
– provide direct access to these properties,
– are valuable for characterization of modern
nanoporous materials.
[1] J. Bear, Dynamics of Fluids in Porous Media, originally published 1972
Dover Publications Inc., New York, 1988
Relevant pore size
IUPAC classification [2]
Pore diameter dp
• macroporous
> 50 nm
• mesoporous
2 nm - 50 nm
• microporous
< 2 nm
submicro< 0.7 nm
ultramicro< 0.4 nm
nanoporous
a10-9 m
[2] J. Rouquerol et al., Pure & Appl. Chem., 66, 1739-1758, 1994
Relevant pore size
Classification according to commonly
used length units in SI [3]
IUPAC classification [2]
Pore diameter dp
• macroporous
> 50 nm
• mesoporous
2 nm - 50 nm
• microporous
< 2 nm
submicro< 0.7 nm
ultramicro< 0.4 nm
milliporous
a10-3 m
microporous
a10-6 m
nanoporous
a10-9 m
[2] J. Rouquerol et al., Pure & Appl. Chem., 66, 1739-1758, 1994
[3] T.J. Mays, Studies in Surface Science and Catalysis, 160, 57-62, 2007
High-tec nanoporous materials
• microporous materials
zeolites ZSM-58
metal-organic frameworks (MOF)
ZIF-8 and CuBTC
• formulated adsorbents
shaped bodies of MOFs
Basolite A520 (Al-Fum)
Applications and pore fluids
storage
separation
catalysis
methane
carbon dioxide
hydrocarbons, water, Li+, …
NMR methods
\ b o D', n( p ), T ,...
o Dii , TR D
g (t )
M xy t T2 , pT2 on
n p, d p Information available from NMR data
F. Stallmach, J. Kärger, Adsorption (1999).
I. Zeolite ZSM-58
50 μm
d / 10-10 m
• high-silica zeolite (SiO2), no cations
• two-dimensional pore system
along <100> , xy-plane
• narrow 8-ring windows
CO2 and CH4 adsorption
d / 10-10 m
CO2 3.3
CH4 3.8
13C
and 1H PFG NMR
d / 10-10 m
CO2 3.3
CH4 3.8
T. Splith, Master thesis (2013).
2D diffusion of CO2 and CH4 in ZSM-58
unitary
unitary CO2
d / 10-10 m
Simulation
(1,3) MD
(2) TST
B.-T. Bleken, et al. / MMM (2013).
Metal-Organic Frameworks
+
=
metal centres + organic linkers = 3D nanoporous frameworks
MOF-5
O. M. Yaghi et al., Nature 1999; Nature 2003
2. Metal-Organic Framework – ZIF 8
Zeolitic Imidazolate Frameworks
ZIF-8 = [Zn(Me-IM)2]n
• SOD structure type
• three dimensional pore system
dp = 11.6 u 10-10 m
• narrow 8-ring windows
dw = 3.4 u 10-10 m
Park, et al., PNAS, 2006
Adsorption of CO2 and CH4 in ZIF-8
CO2
CH4
Spin echo attenuation for 13CO2 in ZIF-8
30 – 20 % gas phase @ 14 bar
70 - 80 % adsorbed phase
Self-diffusion of CO2 in ZIF-8
MD I
MD {
MD II
NMR
8 d p / bar d 18
Pusch, et al.,
Adsorption, 2012
Self-diffusion in binary CO2/CH4 mixtures
d / 10-10 m
ZIF-8 3.4
CO2 3.3 c
CH4 3.8 z
8 d p / bar d 18
Pusch, et al.,
Adsorption, 2012
3. Metal-Organic Framework – CuBTC
CuBTC (Cu2BTC3)
BTC =
Chui, et al., Science, 1999.
• three dimensional pore system
dc,d = 12.4/10.5 u 10-10 m
• small side pocket
db = 4.9 u 10-10 m
• Sm = 150 m2 g-1
Getzschmann et al., MMM, 2010.
High-Pressure NMR porosimetry
Low-field NMR setup with fR (1H) = 5.01 MHz
P
VR
VC
VC
CO2
CH4
CH4 in CuBTC – 1H CPMG NMR
High-pressure adsorption of CH4
C. Horch, et al., JMR, 2014.
CH4 in CuBTC – 1H CPMG NMR
High-pressure adsorption of CH4
adsorbed
free gas
C. Horch, et al., JMR, 2014.
CH4 in CuBTC
High-pressure adsorption of CH4
adsorbed
free gas
x4
CH4 and CO2 in CuBTC
Co-adsorption of CO2
adsorbed
free gas
4. Methane adsorption in formulated MOFs for
gas storage application
U. Müller et al., Chemie Ingenieur Technik 2013, 85, 1726–1733
Methane adsorption measured by low-field 1H NMR
Basolite A250
30 bar
Methane adsorption measured by low-field 1H NMR
Basolite A250
Summary
• NMR porosimetry in materials research – Experimental
studies of mobility and adsorption of molecules confined
to micropores
• 1H and 13 C PFG NMR diffusiometry
CH4 / CO2 selectivity in ZIF-8 and ZSM-58
• 1H NMR relaxometry at elevated CH4 pressures
improvement of gas adsorption studies for
characterization of microporous adsorbents
Acknowledgement
Group Physics of Interfaces
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Carsten Horch
Anne Pusch
Mikulas Peksa
Tobias Splith
Markus Wehring
Marcel Gratz
Steffen Beckert
Stefan Schlayer
Lutz Moschkowitz
…
Partners at Universities Leipzig, Hannover, Bochum, Delft, Prague, …
DFG International Research Training Group “Diffusion in Porous Materials”
EU-India collaborative research Project AMCOS (project no. 233502 )
DFG SPP 1362 “Metal-organic Frameworks ”
23/03/2012
BASF SE and Baker Hughes Inc.
23/03/2012
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