Preparing highly-dispersed noble metal supported mesoporous silica catalysts by reductive amphiphilic molecules

Article abstract of DOI:10.1039/C6RA23875K

We present an in situ reduction strategy to prepare mesoporous silica supported by highly-dispersed noble metals. First, an amphiphilic molecule with ferrocenyl as a reductive hydrophobic terminal group was designed and synthesized. Next, we used it as a

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Preparing highly-dispersed noble metal supported mesoporous
silica catalysts by reductive amphiphilic molecules†
Shengyang Taoa*, Huan Wanga and Huilong Wanga
Received 00th January 20xx,
Accepted 00th January 20xx
We present an in-situ reduction strategy to prepare mesoporous silica supported with highly-dispersed noble metals. First,
an amphiphilic molecule with ferrocenyl as a reductive hydrophobic terminal group was designed and synthesized. Next,
we used it as a structure-directing agent to self-assemble into mesoporous silica. Then the amphiphile remained in the
mesoporous channels could in-situ reduce gold or palladium salts into corresponding metal nanoparticles. Finally, the
amphiphile was removed through calcination. Through XRD and TEM the mesoporous structure and the highly-dispersed
Au or Pd nanoparticles were confirmed. The reducibility of the amphiphile was proved by XPS, and was further verified by
cyclic voltammetry and thermodynamic calculation. BET analysis showed that the mesoporous catalysts have a specific
surface area above 900 m2/g. The catalysts showed significantly higher catalytic activities to the reduction of 4-nitrophenol
DOI: 10.1039/x0xx00000x
www.rsc.org/
and
Suzuki
reaction
than
the
ones
prepared
via
the
traditional
impregnation
methods.
example post-synthetic functionalization or self-assembly
functionalization23 before loading noble metal ions, but some
of them are quite complicated.
Introduction
Mesoporous materials, known as porous materials whose pore
diameters are from 2 nm to 50 nm,1 have been attaching
considerable attention to the chemists since they were born
for their large specific surface area as well as the controllable
pore diameters and pore structures. They have been widely
applied in diverse fields including catalysis,2-7 adsorption,8-10
In this paper, we synthesized an amphiphilic molecule with a
reductive hydrophobic terminal group (ferrocenyl) to serve as
the structure-directing agent, which can co-hydrolyze with
silicate ester to form mesoporous silica materials similar to
that formed from traditional quaternary ammonium salts
(Scheme 1). Then, the reductive amphiphile can in-situ reduce
gold or palladium salts into corresponding metal nanoparticles
that could be loaded in the mesoporous channels. The
catalysts, i.e. mesoporous silica supported with high-dispersed
noble metal nanoparticles, were finally obtained through
calcination. Compared with the ones prepared by the
traditional impregnation methods, our catalysts show
significantly higher catalytic activity to the reduction of 4-
nitrophenol and Suzuki reaction.
sensors,11-14 cells15,
and sustained drug-release17,
etc.
16
18
Mesoporous materials are mainly prepared by the self-
assembly of surfactants, which act as the structure-directing
19
agent to construct nano-scale channels.
Usually after the
inorganic framework was formed, the surfactants will be
removed through calcination, solvent extraction or other
techniques.
In general, the functionalization of mesoporous materials is
carried out by doping other elements to the frameworks or by
modifying the pore surface structures. For example, noble
metals are traditionally loaded in the mesoporous channels as
catalysts through impregnation20, 21. In this method, it is a
common problem that the noble metal nanoparticles may
grow larger than expected, consequently leading to less
dispersion. Specific control to the pore structure and the
impregnation process will often be necessary,22 without which
it will be difficult to realize the high-dispersion of the metal
nanoparticles via normal methods. There are also other
methods to load noble metals in mesoporous silica, for
Scheme 1 The preparation of noble metal supported mesoporous silica via in-situ
reduction strategy
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chromatography (Eluent: petroleum ether: ethyl acetate = 20:
1, the ratio is by volume).
Experiment Section
Materials
The product is a viscous dark orange liquid. Yield 80%.
1H NMR (400 MHz, CDCl3) : δ(ppm) = 9.47 (s, 2H), 8.50 (s, 1H),
8.12 (s, 2H), 5.03 (s, 2H), 4.81 (s, 2H), 4.40 (s, 2H), 4.21 (m, 7H),
2.09 (m, 2H), 1.83 – 1.60 (m, 2H), 1.54 – 1.19 (m, 14H).
13C NMR (400 MHz, CDCl3) δ(ppm) = 171.76, 145.30, 144.71,
128.43, 77.91, 77.59, 77.27, 71.16, 71.08, 69.84, 69.54, 64.09,
61.75, 49.63, 31.66, 29.23, 29.16, 29.06, 28.96, 28.79, 28.62,
25.79.
Ferrocenecarboxylic acid, 11-bromo-1-undecanol, N,N-
dicyclohexylcarbodimide (DCC), 4-dimethylaminopyridine
(DMAP), pyridine, methanol, petroleum ether, ethyl acetate,
dichloromethane, acetonitrile, tetraethoxysilicane (TEOS),
hydrochloric acid (36%~38%), sodium hydroxide, ammonia
solution (25%~28%), hexadecyltrimethylammonium Bromide
(CTAB) and 95% ethanol were purchased from Sinopharm
Chemical Reagent Co.,Ltd. Chloroauric acid, palladium
chloride, 4-nitrophenol, sodium borohydride, bromobenzene,
iodobenzene, phenylboronic acid and biphenyl were
purchased from the Shanghai Aladdin Bio-chem Technology
Corporation. All reagents were used without further
purification.
HRMS: m/z = 462.2090
Synthesis of the mesoporous silica material (MS)
0.5 g FcC11PyBr was dissolved in a mixture of 4.18 g ammonia
solution and 13.74 g deionized water, then 1.60 g TEOS was
added dropwise under vigorous stirring. The mole ratio of the
compounds is TEOS: FcC11PyBr: NH3: H2O=1:0.12:8:122. The
mixture was further stirred for 2h under room temperature.
Then it was transferred into a stainless autoclave with
polytetrafluoroethylene equipment liner and left for 3 days at
80 ˚C. When the hydrothermal treatment was complete, the
solids were separated through filtration and washed with
deionized water for several times. Finally, the solids were dried
in a vacuum desiccator.
Scheme 2 The synthesis of FcC11PyBr
The obtained mesoporous material (MS) is a brown solid.
Synthesis of 11-bromoundecyl ferrocenecarboxylate (FcC11Br)
As a control experiment, MCM-41 was prepared with the
following procedure: 2.4 g CTAB, 50 mL water, 50 mL 95%
ethanol, 13 mL ammonia solution and 3.5 mL TEOS was added
into a flask and stirred at room temperature for 2 h. Then the
solids were filtered and dried in a vacuum desiccator.
The compound was synthesized according to the literature24.
Ferrocenecarboxylic acid (0.48 g, 2.1 mmol) and 11-bromo-1-
undecanol
dichloromethane (dried with molecular sieves) and stirred for
0.5 h at 0 , then catalytic amount of DMAP (0.05 g, 0.4
were
dissolved
in
50mL
anhydrous
℃
mmol) was added to the mixture. Next, DCC (0.43 g, 2.1 mmol)
was dissolved in 50 ml anhydrous dichloromethane, and the
solution was added to the mixture dropwise. The solution was
stirred at room temperature for 2 days. The mixture was then
filtered and the filtrate was collected. The solvents were
removed under reduced pressure. The crude product was
purified with column chromatography (Eluent: petroleum
ether: ethyl acetate = 20: 1, the ratio is by volume).
The product is an orange crystal. Yield 50%.
1H NMR (400 MHz, CDCl3) δ(ppm) = 4.82 (s, 2H), 4.40 (s, 2H),
4.16 (m, 7H), 3.41 (t, 2H), 1.92 – 1.79 (5, 2H), 1.77 – 1.64 (5,
2H), 1.49 – 1.22 (m, 14H).
13C NMR (400 MHz, CDCl3) δ(ppm) = 77.37, 77.05, 76.74, 71.31,
70.19, 69.81, 64.29, 34.06, 32.84, 29.54, 29.47, 29.41, 29.28,
28.92, 28.76, 28.17, 26.07.
Synthesis of Au-supported (or Pd-supported) mesoporous silica
material (Au@MS or Pd@MS)
The reduction part in the procedure is according to the
literature.25
A solution of 10 mg chloroauric acid (dissolved in 4 ml solvent
consisting of methanol: dichloromethane=3:1) was added
dropwise carefully to 100 mg MS (dispersed in 1ml
dichloromethane) at 0 degree Celsius. The mixture was further
stirred for 30 min. The solid gradually turned dark brown. After
the reaction was complete, the mixture was filtered and the
solids were washed with the solvents (methanol:
dichloromethane=3:1) for several times. Then the solids were
transferred into a quartz boat for calcination. The temperature
of the furnace was raised at the rate of 5 ˚C /min, and
maintained at 300 ˚C for 6h. Finally, the temperature was
slowly cooled down to room temperature and the mesoporous
material Au@MS was obtained.
HRMS: m/z = 463.0925
Synthesis of N-(11-(ferrocenecarboxyloxy)undecyl)pyridinium
bromide (FcC11PyBr)
Pd@MS was synthesized with a similar procedure. 6.5 mg
PdCl2 was dissolved in 35 μl hydrochloric acid in advance
because of the insolubility of palladium chloride. Moreover,
the reaction was carried out at room temperature for 1 h.
As a control experiment, MCM-41 was treated with the same
procedure to obtain Au@MCM-41 and Pd@MCM-41.
FcC11Br (0.46 g, 1 mmol) was dissolved in 50 mL acetonitrile.
Then pyridine (0.14 g, 2 mmol) was added dropwise to the
solution under vigorous stirring. The mixture was refluxed for
24 h. After the reflux the acetonitrile was removed by rotary
evaporator. The final product was obtained through
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Catalytic tests
the nitrogen isotherms using the Barrett–Joyner–Halenda (BJH)
model. The X-ray photoelectron spectroscopy (XPS) data were
obtained on a Shimadzu KROTAS AMICUS X-ray photoelectron
spectrometer. The cyclic voltammetry (CV) curve was
measured on a CHI 660D electrochemical workstation. A Pt
electrode was used as the working electrode referenced by a
saturated calomel electrode, and 0.1 mol/L KCl was used as
the supporting electrolyte. Before the scan, the solution was
bubbled with pure argon for 10 min to remove the dissolved
oxygen. The ultraviolet-visible (UV-Vis) spectra were collected
on a Purkinje TU-1900 UV-visible spectrophotometer. The high
performance liquid chromatography (HPLC) tests were run on
a Shimadzu LC-20A high-performance liquid chromatograph
using 90% methanol/10% water as the mobile phase. The
inductive coupled plasma emission spectroscopy (ICP) tests
were analyzed on a PerkinElmer Optima 2000DV spectrometer.
The critical micellar concentration (CMC) of the amphiphile
was measured by the surface tension method. The surface
tension was measured on a Kruss100C surface tension meter.
1) Catalytic reduction of 4-nitrophenol (4-NP)
0.14 g 4-NP was dissolved in water and diluted into 100 ml. 0.4
g NaBH4 was dissolved in 20 ml deionized water. Then 10 mg
Au@MS and 1000 μl 4-NP solution were added to the NaBH4
solution. The mixture was kept stirred and the reaction was
monitored with a UV-Vis spectrophotometer at 400 nm. The
reference cell of spectrophotometer was deionized water.
2) Catalysis of Suzuki reaction
The procedure is according to the literature.26
Phenylboronic acid (0.6 mmol, 74 mg) and sodium hydroxide
(2 mmol, 80 mg) was dissolved in 10 ml deionized water. Then
0.5 mmol bromobenzene (or iodobenzene) and 10 mg Pd@MS
were added to the mixture. The reaction was refluxed at 80 ˚C
for 5 h. After the reflux, mixture was diluted with methanol
until a homogeneous liquid phase was formed. The catalysts
were recycled through centrifuge. The remaining liquid was
sampled and the yield was further analyzed by HPLC.
3) The calculation of turnover frequency (TOF)
Because of the complexity of the heterogeneous reaction in
liquid phase, the TOF is simplified and calculated by the
following formula according to the literature27:
Results and Discussion
As the structure-directing agent, the hydrophilic group and
hydrophobic group are necessary. Herein, ferrocenyl is chosen
as the hydrophobic terminal and N-alkylpyridinium ion is
chosen as the hydrophilic terminal. To ensure we can assemble
the amphiphile into micellar, the self-assembly need to be
carried out above the critical micellar concentration (CMC) of
the amphiphile. Therefore, we determined the CMC of
FcC11PyBr under experimental condition (Fig. S1). From the
measurement we can infer that the CMC of FcC11PyBr is
0.001mol/L, while the experimental concentration is 0.06mol/L,
indicating that the amphiphile did form micellar during the
assembly process.
ꢁ
TOF ꢀ
ꢁꢂꢃꢄ ∙ ꢅ
In the formular,
n is the moles of the consumed reactant in
time , and ncat is the total moles of the noble metals, which is
t
determined by ICP.
Characterization
The 1H NMR and 13C NMR spectra were measured on
PerkinElmer Bruker Avance II 400 NMR spectrometer with
chemical shifts reported in ppm (CDCl3 as solvent, TMS as
internal standard). The HRMS spectra were obained on Agilent
G6224A Liquid Chromatography
& Time-of-Flight Mass
Spectrometer. The Fourier transform infrared spectoscopy
(FT-IR) spectra were obtained on a Nicolet Avatar 360 FT-IR
spectrometer with the wavenumbers ranging from 4000 cm-1
to 500 cm-1, and the test samples were prepared though KBr
pellet pressing method. The X-ray powder diffraction (XRD)
patters were collected on a Rigaku D/max-2400 X-ray powder
diffractometer, using Cu Kα (λ = 1.5405 Å) radiation. The small-
angle XRD data were collected from
2
θ
wide-angle XRD data were collected from
=0.9˚ to 10˚, and the
=5˚ to 80˚. The
2
θ
transmission electron microscopy (TEM) images were obtained
on a FEI Tecnai F30 transmission electron microscope with a
working voltage of 300kV. The TEM samples were prepared by
depositing a drop of the suspension (containing the samples
suspended in anhydrous ethanol and sonicated for 30 minutes)
on a copper grid coated with a carbon film and followed with
drying. The nitrogen adsorption and desorption isotherms was
measured at 77 K on an ASAP 2010 analyzer (Micromeritics Co.
td.). The samples were degassed under vacuum at 473 K for 2
h. The specific surface areas were calculated using Brunauer–
Emmett–Teller (BET) method. The pore size and pore volume
distributions were calculated from the desorption branches of
Fig. 1. The FT-IR spectra of the surfactant (FcC11PyBr) and the as-synthesized
mesoporous silica (MS)
Fig. 1 is the FT-IR spectra of the amphiphile and the as
synthesized mesoporous silica (MS). It can be noticed that the
absorption at 2930 cm-1, 2860 cm-1, 1460 cm-1 and 1710 cm-1
(corresponding to the C–H and C=N bond vibration of
FcC11PyBr) also appears in the FT-IR of MS. And the absorption
at 1070 cm-1 is the vibration of the Si-O-Si bond, which
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indicates that the amphiphile and the silica formed
Journal Name
a
composite system. From the small angle XRD patterns of the
mesoporous material in Fig. 2a, a strong peak at 2.260˚, and
two weaker peaks at 3.921˚ and 4.500˚ are observed. These
XRD results are basically identical to the XRD patterns of MCM-
41, suggesting a hexagonal channel mesoporous structure. The
peaks remained after the treatment of the noble metal salts as
well as calcination, which indicates the mesoporous material is
stable enough to endure both the noble metal ions and
calcination.
Fig. 2. (a) The small-angle XRD patterns of the mesoporous silica materials; (b) The
wide-angle XRD patterns of the mesoporous silica materials.
The further wide angle XRD patterns show no apparent Au
or Pd diffraction peaks in Fig. 2b. Au@MS showed tiny
diffraction peaks at 38.079˚ and 44.167˚, corresponding to the
(111) and (200) crystal plane. The peaks can be observed both
before and after the calcination, which implies that metal gold
has already existed in Au@MS before calcination, and also
implies the reducibility of the surfactant, i.e. to reduce Au(III)
salts into metal Au. While the diffraction peaks of Pd are
almost unobservable, suggesting that Pd has formed smaller
clusters than the Au nanoparticles. To sum up, the XRD curves
of the mesoporous materials indicate that no large crystals of
the metals exist in the mesoporous materials.
Fig. 3. The XPS patterns of (a) Au@MS (the scan of Fe2p) (b) Au@MS (the scan of Au4f)
(c) Pd@MS (the scan of Pd3d). The patterns of Fe2O3,28, 29 metal Au,30 Cs[AuCl4],31 metal
34, 35
Pd32, 33 and PdCl2
are stimulated according to the data from National Institute of
Standards and Technology (NIST) XPS Database
The XPS results can further confirm this conclusion. As is
shown in Fig. 3a, after the treatment of HAuCl4, the 2p3/2 peak
of Fe appears at 711.14 eV, suggesting that the valance of iron
is +3. The observed data are consistent with the iron(III)
compounds in the literature28. However, it is commonly
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recognized that the valance of iron in ferrocene is +2. 30 min), the Au nanoparticles in the obtained Au@MS is still
Thisindicates that the iron(II) does have been oxidized. The larger than the Pd nanoparticles in Pd@MS. To conclude this
valance of iron has no apparently change after calcination. On part, it is completely feasible to use ferrocenyl-grafted
the other hand, the valance of gold turned zero after the amphiphile to act as both a structure-directing agent and the
treatment, and a peak at 82.75 eV was observed. There is also reductant to load noble metal nanoparticles on mesoporous
no obvious change in the valance of gold after calcination. This silica.
proves that Au(III) has already been reduced to metal gold and
The nitrogen absorption-desorption isotherms (Fig. 5a)
no Au(III) was remained in Au@MS before calcination. show a typical type-IV curve defined by IUPAC, suggesting an
Moreover, the calcination process also did not change the ordered mesoporous structure of silica similar to MCM-41.
valance of gold. These results can further verify that there After loaded with noble metals, both the materials have a
does be a redox reaction between the metal ions and the specific surface area above 900 m2/g (Table 1), providing more
surfactants containing ferrocenyl group. As
a control contacting positions for the reaction. The pore diameter is
experiment, uncalcined Au@MCM-41 did not show Au peaks around 3.2nm, which is far bigger than the normal small
due to the low content of gold, indicating that amphiphile such molecules. Meanwhile, the narrow distribution of pore
as ferrocenyl cannot reduce Au(III) salts. Similar results can be diameters indicates that a formation of uniform mesopores,
observed on Pd@MS, revealing that Pd salts can also be which can reduce the clog during the diffusion and make the
reduced into simple substance supported on the mesoporous substances go in and out of the channels smoothly through the
silica.
catalytic process.
Fig. 4. The cyclic voltammograms of FcC11PyBr aqueous solution and the standard
electrode potentials of related redox couples
In addition, we investigated the redox potential of the
amphiphile by cyclic voltammetry as is shown in Fig. 4. After
converting the potential vs SCE to the potential vs NHE, the
standard electrode potential of FcC11Py2+/FcC11Py+ is 0.687 V,
while the standard electrode potentials of [AuCl4]-/Au and
[PdCl4]2-/Pd are 1.002 V36 and 0.591 V37 respectively.
Obviously, [AuCl4]- can oxidize FcC11PyBr. For palladium,
[PdCl4]2- cannot oxidize FcC11PyBr at standard state. However,
owing to the small difference between the two electrode
potentials, it can be inferred that the reaction of [PdCl4]2- and
FcC11PyBr may reach an equilibrium with sufficient metal
palladium formed. According to a calculation given by the
Nernst Equation (the details are in the supporting
information), the electrode potential of [PdCl4]2-/Pd will
increase to 0.655 V under the experimental conditions. On the
other hand, the electrode potential of FcC11Py2+/FcC11Py+ is
0.629 V when we terminated the reaction. Thus, it is
explainable that [PdCl4]2- can oxidize FcC11PyBr under
experimental conditions. The calculation also agrees with
several facts in our experiments. First, Pd@MS was
synthesized at room temperature for 1h. However, if Au@MS
was prepared under the same condition, the percentage of Au
in Au@MS can reach 6.612%wt and the dispersion of the Au
nanoparticles will be very poor. Secondly, even though we
optimized the condition to reduce HAuCl4 (0 ˚C for 15 min to
Fig. 5. (a) The nitrogen adsorption-desorption isotherms (inset: pore size distribution)
(b) the mesoporous structure of MS in the TEM image
Table 1. The BET analysis results of the as-synthesized mesoporous silica (MS) and MS
loaded with noble metals
Surface area
/m2·g-1
Pore volume
/mL·g-1
Pore
diameter/nm
3.13
Samples
Au@MS
Pd@MS
920.9152
924.4732
0.9000
1.0335
3.14
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The catalytic performance of the supported Au and Pd
nanoparticles are investigated through the hydrogenation of 4-
nitrophenol (4-NP) and Suzuki reaction respectively. For
Au@MS, excellent catalytic activity has been observed. As we
can see in Table 2, 4-NP can be completely reduced in 90
seconds (Table 2, Entry 2), whereas no reduction can be
observed without the presence of Au (Table 2, Entry 1). On the
other hand, Au@MCM-41, i.e. MCM-41 loaded with Au
through traditional impregnation method, was prepared to
compare the catalytic ability with Au@MS. It turns out that
more than an hour is required to consume all the 4-NP under
the same reaction conditions, and the yield in 90 seconds is
only 17.6% (Table 2, Entry 3). To further confirm that the
experimental phenomena were caused by the catalysis of Au
nanoparticles rather than simple physisorption, we measured
the full-spectra scan during the reaction (Fig. 8a). From the
spectrogram we can naturally see the absorption of 4-NP
decrease at 400 nm. Besides, a new absorption peak gradually
appears at 300nm simultaneously, corresponding to the
reduction product 4-aminophenol, excluding the possibility of
the simple physisorption of 4-NP by the mesoporous materials.
For Pd@MS, we choose Suzuki reaction to investigate the
catalytic activities. From the experiments we found good
catalytic activities for both bromobenzene or iodobenzene to
react with phenylboronic acid and form the product biphenyl.
The yield can be both over 90%. The TOF of the reaction is
relatively high (Table 2, Entry 4), which is due to the low
percentage of palladium in the mesoporous material (0.32%).
For bromobenzene, the TOP is 308 h-1. However, for
Pd@MCM-41, which is obtained by traditional impregnation
method, the yield is only 6.184% (Table 2, Entry 5), less than
one tenth of Pd@MS. The results also prove that through in-
situ reduction the obtained mesoporous silica loaded with Pd
nanoparticles showed high catalytic activities. The cycle
experiments indicate that the yield maintained around 70%
after 3 cycles (Fig. 8b). What caused the yield to decrease
should be the damage of silica framework in basic condition,
which further caused the leaching of the Pd nanoparticles. The
reason may also be the small particle size and the small dosage
of the catalysts leading to the unavoidable loss through the
centrifuge.
Fig. 6. The TEM images of (a) Au@MS (b) the Au nanoparticles in Au@MS (c) Pd@MS
(d) the Pd nanoparticles in Pd@MS
The TEM images of the mesoporous materials loaded with
noble metal nanoparticles (Fig. 5b) reveal the uniform
hexagonal channels, most of which are ordered structure and
a little few of which are worm-like structure. Furthermore, the
fine structure of the Au and Pd nanoparticles can be clearly
observed in the HRTEM images (Fig. 6). The nanoparticles have
a size below 10nm, showing excellent lattice structure and
dispersion. It also can be inferred from the TEM results that
the size of the metal nanoparticles will increase as the reaction
time extends (Fig. 7). Consequently, the reduction time should
be controlled no longer than 30 minutes for Au@MS. Larger
nanoparticles usually will decrease the dispersion of the
catalysts and further affect the catalytic activities.
Fig. 8. (a) The UV-vis spectra of 4-nitrophenol solution in presence of Au@MS and
NaBH4. To make the reaction monitored by the full-spectra scan more easily, the
amount of 4-NP was increased. (b) The catalyst recycling test of Pd@MS for the Suzuki
reaction of PhBr and phenylboronic acid
Fig. 7. The TEM images of the Au nanoparticles in Au@MS obtained by different
reaction time: (a) 72h (b) 14h (c) 6h (d) 3h (e) 30min (f) 15min
Table 2 The catalytic performance of the synthesized mesoporous silica catalysts
6 | J. Name., 2012, 00, 1-3
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7
8
9
X. Zhu, W. Wei and Y. Wan, ChemCatChem, 2015,
2956.
B. J. Dou, Q. Hu, J. J. Li, S. Z. Qiao and Z. P. Hao, J. Hazard.
Mater., 2011, 186, 1615-1624.
D. Perez-Quintanilla, I. del Hierro, M. Fajardo and I. Sierra,
Microporous Mesoporous Mater., 2006, 89, 58-68.
7, 2945-
Noble metal
percentage
(wt%)
Yield
(%)
Entries
Samples
TOF(h-1)
1
2
3
4
5
MS(calcined)
Au@MS
0
0a,b
0
0.2727
0.0613
0.3231
tracec
100.0a
17.60a
90.55b
6.184b
3039
2380
300
-
Au@MCM-41
Pd@MS
10 R. J. Yang, D. Y. Gao, H. Huang, B. Huang and H. Q. Cai,
Microporous Mesoporous Mater., 2013, 168, 46-50.
11 C. X. Lin, W. Zhu, H. W. Yang, Q. An, C. A. Tao, W. N. Li, J. C.
Pd@MCM-41
Cui, Z. L. Li and G. T. Li, Angew. Chem. Int. Ed., 2011, 50
4947-4951.
,
a) Catalytic reduction of 4-nitrophenol for 90 seconds.
12 B. An, S. S. Park, Y. Jung, I. Kim and C. S. Ha, Molecular
Crystals and Liquid Crystals, 2008, 492, 210-220.
13 B. Z. Li, Z. Xu, W. Zhuang, Y. Chen, S. B. Wang, Y. Li, M. L.
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11497.
b) Suzuki reaction of PhI and phenylboronic acid for 5 hours.
c) Not detected by ICP.
14 B. J. Melde, B. J. Johnson and P. T. Charles, Sensors, 2008, 8,
5202-5228.
Conclusion
15 L.-L. Li, H. Sun, C.-J. Fang, Q. Yuan, L.-D. Sun and C.-H. Yan,
Chem. Mater., 2009, 21, 4589-4597.
In this work, we designed and synthesized amphiphile with
ferrocenyl as the hydrophobic group. The synthesized
molecule can act as structure-directing agent to synthesize
16 E. B. Cho, H. Kim and D. Kim, J. Phys. Chem. B, 2009, 113
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,
mesoporous silica with highly ordered hexagonal channels; 17 M. D. Popova, A. Szegedi, I. N. Kolev, J. Mihaly, B. S. Tzankov,
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Meanwhile, the surfactants remained in the channels, and the
ferrocenyl group in the surfactants can reduce Au(III) and Pd(II)
salts into corresponding metal nanoparticles. Through this
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catalytic activities for the catalytic hydrogenation of 4-
nitrophenol and Suzuki reaction compared with those
obtained by the traditional impregnation method. To
conclude, this is an idea to realize fabricating high 22 F. Pinna, Catal. Today, 1998, 41, 129-137.
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performance catalysts by molecule design. On the one hand,
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the designed molecules to achieve atom economy; On the
other hand, the idea may help noble nanoparticles form highly
dispersed system in mesoporous channels, which will promote
the catalytic process. In addition, this is also an idea to prepare
catalytic materials via supramolecular assembly and reaction
1
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synthesizing other new catalytic materials.
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