Supplementary Material (ESI) for Chemical Communications
This journal is © The Royal Society of Chemistry 2008
Nanometer-sized Titania hosted inside MOF-5
Maike Müller,a Xiaoning Zhanga, Yuemin Wangb and Roland A. Fischer*a
Anorganische Chemie II, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780, Bochum,
Germany, Fax: +49 (0)234 32-14174; Tel: +49 (0)234 32-24174; E-mail: [email protected]
a
b
Technische Chemie, Ruhr-Universität Bochum, Bochum, Germany
Supporting Information
XPS measurements were carried out in an ultra-high vacuum (UHV) set-up equipped with a high
resolution Gammadata-Scienta SES 2002 analyzer. Monochromatic Al Kα X-ray source (1486.6 eV;
anode operating at 14 kV and 55 mA) was used as incident radiation. The base pressure in the
measurement chamber was around 2 ×10−10 mbar. XP spectra were recorded in the fixed transmission
mode. The analyzer slit width was set to 0.4 mm and a pass energy of 200 eV was chosen, resulting in
an overall energy resolution better than 0.7 eV. Charging effects were compensated by applying a
flood gun. The binding energies were calibrated based on the hydrocarbon C1s peak at 285 eV. Prior
to individual elemental scans a survey scan was taken for all the samples in order to detect all the
elements present.
Figure S1 XP survey spectra of the different MOF samples: (a) MOF-5; (b) TiO2@MOF-5
(as-synthesized) (c) TiO2@MOF-5 (annealed, 250°C 2d).
Zn 2p
O KLL
Intensity / arb. units
Zn LMM
O 1s
C 1s Ti 2p
Zn 3p
c
b
a
0
200
400
600
Binding Energy / eV
800
1000
Figure S2 High-resolution XP Zn 2p, Zn L3M45M45, C1s, O1s and Ti 2p spectra of MOF-5
and TiO2@MOF-5 samples (as-synthesized and annealed).
Zn 2p
Zn L3M45M45
2p3/2
1022.2
TiO2@MOF-5 (annealed)
Intensity / arb. units
Intensity / arb. units
2p1/2
1045.5
TiO2@MOF-5 (as-synthesized)
MOF-5
1050
1040
1030
987.5
TiO2@MOF-5 (annealed)
TiO2@MOF-5 (as-synthesized)
MOF-5
975
1020
980
Binding energy / eV
985
990
995
1000 1005
Kinetic Energy / eV
The Zn 2p spectrum shows two peaks at 1022.5 and 1045.5 eV which are assigned to
the 2p3/2 and 2p1/2 components, respectively. The Zn 2p core levels are not sensitive
to the oxidation state of zinc. The latter can be clearly identified by the Zn L3M45M45
Auger spectra. The corresponding peak observed at 987.5eV (kinetic energy, KE)
demonstrates the presence of Zn2+ species in MOF-5
Intensity / arb. units
C 1s
285
TiO2@MOF-5 (annealed)
carbonylate
289.5
TiO2@MOF-5 (as-synthesized)
281.6
carbide
282.4
MOF-5
295
281
290
285
280
Binding energy / eV
The C1s spectra are dominated by the intense hydrocarbon peak at 285 eV. The
weak peak at 289.5 eV is characteristic for the carbonylate species (-COO) in MOF-5.
In addition, a carbidic C1s peak is observed at 282.4 eV and shifts to lower binding
energies after the modification of MOF-5 with TiO2, indicating the formation of TiC
species.
carbonylate 531.5
O 1s
528.6
Intensity /arb. units
TiO2@MOF-5
(annealed)
TiO2@MOF-5
(as-synthesized)
MOF-5
540
535
530
525
520
Binding energy / eV
The existence of the carbonylate species is also confirmed by the O1s peak at about
531.5 eV. For MOF-5, an additional peak is detected at 529.3 eV which is related to
the presence of Zn4O groups in the MOFs structure. After the inclusion of TiO2, the
oxide-related O 1s peak increases in intensity and shifts slightly to lower binding
energies, revealing the formation of TiO2 species.
Intensity / arb. units
Ti 2p
2p1/2
2p3/2
464
458.5
TiO2@MOF-5 (annealed)
456.2
462.2
TiO2@MOF-5 (as-synthesized)
470
465
460
455
450
Binding energy / eV
The formation of TiO2 is further identified by the XPS data for Ti 2p core levels. At room
temperature, the doublet peak observed at 458.5 and 464 eV is characteristic for
TiO2 species. Another doublet peak is seen at 456.2 and 462.2 eV which can originate
from the TiO2 precursors (TiOiPr4). After heating to higher temperatures (T=250 °C), the
TiO2 precursors further decompose to yield TiO2 as supported by the increase of the
TiO2 relative concentration.
Figure S3 TG/DTA of a TiO2@MOF-5 sample (as-synthesized).
Figure S4 TG/DTA of TiO2@MOF-5 sample annealed at different temperatures in
comparison to a typical MOF-5 sample.