B. Karimi et al.
nitrogen heteroatoms in the carboneous framework might
also be responsible for the relatively uniform distribution of
PdNPs throughout the mesoporous structure and the inhibi-
tion of Pd agglomeration during the reaction, resulting in
high durability, high stability, and recycling characteristics of
were purchased from Fluka. 1,3-Dialkylimidazolium bromide was pre-
pared according to standard methods and their purities were established
1
3
1
before utilization by C NMR and H NMR. Briefly, a solution of dry
toluene (50 mL), freshly distilled 1-methylimidazole (73.1 mmol) and 2-
bromo-1-phenylethane (80.3 mmol) was refluxed for 24 h under an argon
atmosphere. The resulting two phase reaction mixture was then allowed
to cool at room temperature. The separated ionic liquid (IL) layer was
2
. In order to further clarify this issue, we isolated
washed with dry toluene and dry Et
anion-exchange reaction was carried out in dry methylene chloride con-
4
taining 1 mmol of 1,3-dialkylimidazolium bromide and 1 mmol of H SO .
2
O and dried under vacuum. The
Pd@CMK-3 from the aerobic oxidation of benzyl alcohol
under optimal reaction conditions. The recovered
Pd@CMK-3 was then studied by using transmission electron
microscopy to hopefully find a reason for the lower activity
of Pd@CMK-3. As can be clearly seen in this image (Fig-
ure 5b vs. 5a) Pd@CMK-3 showed an extensive agglomera-
tion after the first reaction cycle under our described reac-
tion conditions. This observation supports the notion that
the extensive agglomeration of PdNPs in Pd@CMK-3 during
the first reaction cycle is the major reason for its lower ob-
served activity (Table 1, entry 25).
2
The solution was refluxed for 48 h until any hydrogen chloride by-prod-
uct was removed. After evaporation of the solvent under vacuum, 1-
methyl-3-phenethyl-1H-imidazolium hydrogen sulfate (MPIHS) 1 was
isolated in good yield.
The carbonization process was performed in a Nabertherm furnace (L 3/
1
1/P330) under an inert atmosphere of Ar. The pore structures of the
prepared materials were observed by transmission electron microscopy
(Philips CM-200 and Titan Krios TEM, see Supporting Information) and
were verified further by the nitrogen sorption isotherm (Belsorp,
BELMAX, Japan). The palladium content of the catalyst was determined
using atomic absorption spectrometry (Varian) using the standard addi-
tion method. Gas chromatography analyses were performed on Varian
CP-3800 using a flame ionization detector (FID) using suitable internal
1
Conclusion
standards. NMR spectra were recorded using a Bruker ( H frequency:
1
3
4
00 MHz, C frequency: 100 MHz).
Preparation of SBA-15: Briefly, 0.017 mol of pluronic P123
EO20PO70EO20 (EO=ethylene oxide, PO= propylene oxide), Mav
800, Aldrich) was dissolved in 193 mol of H O and 5.9 mol of concen-
trated HCl at 358C. Consequently, 1 mol of tetraethyl orthosilicate
TEOS) was added to the solution. The mixture was stirred vigorously at
In conclusion, a novel mesoporous carbon (IFMC) with
a uniqe nano-fibrous morphology was successfully prepared
through the carbonization of ionic liquid 1-methyl-3-phe-
nethyl-1H-imidazolium hydrogen sulfate (1) in the presence
of SBA-15 as structural transducing agent. The material was
then used as a powerful and effective support to stabilize
PdNPs. The resulting composite material (Pd@IFMC; 2)
was shown for the first time to be an active catalyst for aero-
bic oxidation of alcohols with either molecular oxygen or air
on water at room temperature and also at 408C, which is
relatively low for such reactions. Remarkably, the current
Pd@IFMC catalyst system shows much higher catalytic ac-
tivity compared to Pd@CMK-3 and well-known Pd/C cata-
lyst systems. It also shows superior reactivity than the previ-
ously reported metal NP/carbon catalyst systems on neat
water at low temperatures. Besides the easy recovery and
reusability of this catalyst, the employment of very mild re-
action conditions and the possibility to perform the transfor-
mation in the absence of any organic solvent make this cata-
lyst system a valuable candidate for green chemistry pro-
cesses. We speculate that the unique properties discovered
in the present nano-fibrillated mesoporous carbon would
open new challenging areas in the design and synthesis of
new types of supported catalyst systems employing various
transition-metal nanoparticles for application in organic cat-
alytic reactions under mild reaction conditions.
(
=
5
2
(
358C for 20 h followed by an aging step at 808C for 24 h. The solid prod-
ucts were filtered off and washed with ethanol. After drying at room-
temperature, SBA-15 was obtained by subsequent removal of the surfac-
tant by extraction with ethanol.
Preparation of IFMC (Ionic Liquid derived Nano Fibrillated Mesoporous
Carbon): To synthesize IFMC, a dry acetonitrile solution of IL (1 mL of
1-methyl-3-phenethyl-1H-imidazolium hydrogen sulfate (MPIHS) 1 in
25 mL of acetonitrile) was added drop wise to a suspension of SBA-15 in
acetonitrile. After 24 h of stirring at room temperature, the solvent was
removed under reduced pressure. The resultant powder was impregnated
2 2 4
with an aqueous solution of sulfuric acid (4 g H O, 0.14 g H SO ) and
placed at 1008C in a vacuum drying oven. After 6 h, the oven tempera-
ture was increased to 1608C and maintained for 6 h until a dark brown
powder was obtained. MPIHS 1 (0.4 mL) was incorporated again into
mesoporous silica hosts by the same procedure. The SBA-15/1 composite
was then kept in an argon flow at 9008C for 3 h to carbonize the IL. In
order to remove the silica template, the black powder was stirred in a so-
lution of 2m sodium hydroxide at 508C for 24 h. The filtered nanoporous
carbon was washed several times with deionized water and ethanol and
vacuum dried.
Preparation of Pd@IFMC 2 (IFMC-stabilized Pd nanoparticles): A sus-
pension of IFMC (50 mg) in dry degassed THF (40 mL) was placed in
a
100 mL round-bottom flask and sonicated for 30 min. Pd
ACHTUNGTRENNUNG( OAc)
2
(
0.036 mmol) was dissolved in THF (20 mL) and added to the IFMC sus-
pension. To prepare the PdNPs onto IFMC, hydrazine hydrate (10 mL)
was added to the suspension under vigorous stirring. After vigorous stir-
ring at room temperature for 1 h, one drop of 30% H O was added. The
2 2
resulting Pd@IFMC 2 was filtered, washed several times with THF, and
dried. The ILMC-stabilized PdNPs was stored in a sealed container.
Experimental Section
[2a]
Preparation of CMK-3 (carbon mesoporous from Korea):
Typically,
the resultant template-free SBA-15 was impregnated with an aqueous so-
lution of sucrose (1.25 g sucrose in 5 g H O) containing 0.14 g sulfuric
General information: Pluronic P123 (EO20PO70EO20 (EO= ethylene
oxide, PO= propylene oxide), Mav = 5800) was purchased from Aldrich.
Palladium(II) acetate was obtained commercially from Acros Organics.
2
acid and placed in a vacuum drying oven at 1008C. After 6 h the oven
temperature was increased to 1608C and maintained for 6 h until a dark
brown or black powder was achieved. The impregnation step was repeat-
ed once with sucrose (0.8 g). The resultant composite was kept in an
argon flow at 9008C for 2 h to carbonize the sucrose. In order to remove
the silica template, the black powder was stirred in a solution of ethanol
1
-Methylimidazole, 2-phenylethyl bromide, tetraethyl orthosilicate
(
TEOS), sulfuric acid (95–98%), hydrochloric acid (37%) and solvents
were obtained from Merck Company and used without purification. (3-
Mercaptopropyl)triethoxysilane and anhydrous potassium carbonate
&
6
&
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 0000, 00, 0 – 0
ÝÝ
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