Tin incorporated periodic mesoporous organosilicas (Sn-PMOs): Synthesis, characterization, and catalytic activity in the epoxidation reaction of olefins

Article abstract of DOI:10.1016/j.catcom.2010.11.025

Tin incorporated mesoporous organosilicas (Sn-PMO) having uniform hexagonal arrangements were prepared using alkyl trimethylammonium bromide surfactants under basic reaction conditions. Characterization techniques revealed that the structural ordering, morphology, and the percentage of tin incorporation depend critically on the hydrophobic chain length of surfactants. The Sn-PMO samples are thermally stable up to 500 °C under air atmosphere and were hydrothermally stable up to 100 h in boiling water. The organotinsilicates showed excellent catalytic activity and reusability in the epoxidation of norbornene and cis-cyclooctene than an Sn-MCM-41 due to organic groups in the frame wall positions and the better accessibility of reactants to the active sites.

Full text of DOI:10.1016/j.catcom.2010.11.025

Catalysis Communications 12 (2011) 629–633
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Catalysis Communications
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Short Communication
Tin incorporated periodic mesoporous organosilicas (Sn–PMOs):
Synthesis, characterization, and catalytic activity in the epoxidation reaction of olefins
⁎
Sheetal Sisodiya, S. Shylesh, A.P. Singh
Catalysis Division, National Chemical Laboratory, Pune-411 008, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 11 October 2010
Received in revised form 24 November 2010
Accepted 27 November 2010
Available online 4 December 2010
Tin incorporated mesoporous organosilicas (Sn–PMO) having uniform hexagonal arrangements were
prepared using alkyl trimethylammonium bromide surfactants under basic reaction conditions. Character-
ization techniques revealed that the structural ordering, morphology, and the percentage of tin incorporation
depend critically on the hydrophobic chain length of surfactants. The Sn–PMO samples are thermally stable up
to 500 °C under air atmosphere and were hydrothermally stable up to 100 h in boiling water. The
organotinsilicates showed excellent catalytic activity and reusability in the epoxidation of norbornene and cis-
cyclooctene than an Sn–MCM-41 due to organic groups in the frame wall positions and the better accessibility
of reactants to the active sites.
Keywords:
Mesoporous
Organosilica
Sn–PMO
© 2010 Elsevier B.V. All rights reserved.
Sn–MCM-41
Epoxidation
Hydrothermal stability
1. Introduction
substituted mesoporous solids, however, possess limited hydrothermal
stability due to the presence of high-density silanols and are usually not
After the discovery of silica-based ordered mesoporous materials [1],
extensive research was focused on modifying the silica framework with
various heteroatoms and on the utility of the resulting materials in various
organic transformations. Subsequently, attention has been devoted to the
synthesis of organic–inorganic hybrid mesoporous materials by the co-
condensation or by the post-synthesis grafting of organosilanes on
mesoporous supports [2,3]. However, both syntheses suffered drawbacks,
typically in the percentage of organic groups introduced into the resulting
hybrid nanocomposites. Silsesquioxane materials, on the other hand,
containing one silicon atom bound to one and a half oxygen atoms and
one organic R group, having the general formula (RSiO3/2)n, were
produced as amorphous materials in the late nineties [4,5]. A combination
of the supramolecular templating approach with the silsesquioxane
precursors recently resulted in novel organic–inorganic hybrid materials
referred to as periodic mesoporous organosilicas (PMO) [6–8]. Until now,
organo-bridged hybrid mesoporous materials containing various organic
fragments attracted attention due to their high stability, hydrophobicity,
and good mesostructural ordering [9,10].
stable under harsh reaction conditions [11–14]. On the other hand,
introduction of heteroatoms in the frame walls of periodic mesoporous
organosilicas (PMOs) can improve the stability as well as catalytic
activity of mesoporous metallosilicates [15–18]. Thus, metal containing
mesoporous hybrid materials arise as novel catalysts and receive much
attention because of their increased hydrophobic nature. Furthermore,
these hybrid materials have been reported to be more active in certain
reactions where M-MCM-41 materials were least active [15]. Noting the
importance of various tin substituted porous materials in various
organic transformations, it is worth verifying the introduction of tin into
the framework of PMO (Sn–PMO) and its catalytic evaluation over
conventional tin substituted mesoporous silicas.
In this paper, we describe the first successful synthesis of tin-
containing mesoporous organosilicas prepared using cationic surfac-
tants having different alkyl chain lengths. The materials were
characterized systematically by various physico-chemical techniques
and the catalytic activity was evaluated in the epoxidation reaction of
norbornene and cis-cyclooctene. The recyclability, stability, and
heterogeneity of the Sn–PMO catalyst were further compared with a
Sn–MCM-41 sample having similar tin loadings.
Selective epoxidation reactions of olefins are one of the most
desirable and challenging reactions since epoxides are valuable
intermediates for the synthesis of valuable oxygen containing organic
compounds. Earlier these reactions were carried out by metal
substituted microporous and mesoporous solid materials. Metal-
2. Experimental
2.1. Synthesis of catalysts
The typical molar gel composition for the synthesis of Sn–PMO was
1BTEE:0.67 C18–TMABr:0.0012SnCl4:3.2NaOH:420H2O, where BTEE is
⁎
Corresponding author. Tel.: +91 20 2590 2497; fax: +91 20 2590 2633.
E-mail address: ap.singh@ncl.res.in (A.P. Singh).
1566-7367/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.catcom.2010.11.025

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S. Sisodiya et al. / Catalysis Communications 12 (2011) 629–633
Sn–C16–PMO
Sn–C18–PMO
Sn–C14–PMO
100
100
100
110
200 b
a
b
a
b
a
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
2θ / degrees
2θ / degrees
2θ / degrees
Fig. 1. XRD patterns of Sn–PMO samples, (a) as-synthesized and (b) surfactant-extracted.
1,2 bis (triethoxysilylethane) and C18-TMABr is octadecyltrimethy-
lammoniumbromide. After mixing the reagents, the final gel was
stirred for 20 h at ambient temperature and were further refluxed for
40 h at 95 °C. The white precipitate obtained was then collected by
vacuum filtration, washed with deionized water, and finally dried at
80 °C for 2 h. The surfactant inside the pores of the hybrid material
was removed by stirring 1 g of as-synthesized material with HCl/EtOH
(0.5 g/100 ml) mixture at 70 °C for 6 h. For comparison, a Sn–MCM-41
sample was prepared and the details were reported elsewhere [19].
using different chain length surfactants (Sn–C18–, Sn–C16–, Sn–C14–
PMO) are given in Fig. 1. The surfactant-extracted materials displayed
larger peak intensities than the as-synthesized samples due to an
enhancement of contrast density between the framewalls and pore
channels. The material obtained from the long chain C18– and C16
surfactant showed the characteristic peaks at lower angles (2θb5°)
indexed to the (100), (110), (200) Bragg reflections than over C14
–
–
surfactant [6]. Further, the amount of tin incorporation was measured
as a function of surfactant chain length; the percentage of tin was
found higher over the more hydrophobic chain length templated
mesoporous solids (Table 1). All these results suggest that if the
surfactant chain is long enough and more hydrophobic, it can form a
large pore channel and heteroatom can easily be incorporated along
the pore than in the small pore channels produced by the short chain
length surfactants similar to earlier observations over porous
organosilicates and MCM-41 [20,21]. Nitrogen adsorption–desorption
isotherms of Sn–PMO samples depicted typical type IV isotherm
characteristic of materials having uniform mesopore structures
(Fig. 2). Noteworthy, the BET surface area, pore volume, and pore
diameter of the Sn–PMO materials calculated from the adsorption
isotherms increase monotonically with an increase in the surfactant
chain length implying further a truly surfactant templating mecha-
nism towards the formation of tin substituted organosilica materials
(Table 1). TEM images further showed the ordered pore arrangement
with retention of mesoporous structure, in well accordance with the
XRD and nitrogen physisorption results.
2.2. Characterization
Powder X-ray diffractograms were collected on a Rigaku D MAX III
VC diffraction system using Ni-filtered Cu Kα radiation (λ=1.5404 Å)
over the range 1.5–5° (2θ), with a scan speed of 2° per minute. The
specific surface area, total pore volume, and average pore diameter
were measured by N2 adsorption–desorption method using a NOVA
1200 (Quanta chrome) instrument after activating the samples at
150 °C for 6 h. Solid-state 13C CP MAS NMR and 29Si MAS NMR spectra
were recorded on a Bruker MSL 300 NMR spectrometer with a
resonance frequency of 75.5 MHz and 59.6 MHz for 13C and 29Si, and
the chemical shifts were referenced to glycine and TMS, respectively.
Diffuse reflectance UV–Vis spectra were recorded with a Perkin Elmer
Lambda 650 spectrometer equipped with a diffuse reflectance
attachment, using barium sulphate as reference. Thermal analysis
(TG-DTA) of the samples was conducted using a Pyris Diamond TGA
analyzer with a heating rate of 10 °C min−1 under air atmosphere.
29Si MAS NMR spectra of surfactant extracted Sn–PMO samples
showed the presence of two peaks, one at −58 ppm for T2 sites (C
(OH)Si(OSi)2) and other at −67 ppm for the T3 sites (CSi–(OSi)3). The
spectra are devoid of Qn silicons (Qn =Si(OSi)n(OH)4-n,, n=2–4),
showing a complete retention of bridging organic groups [6]. 13C
CP MAS NMR spectra of the surfactant extracted hybrid samples
showed a sharp peak at 5.2 ppm, corresponding to the –Si–CH2–CH2–
2.3. Catalytic activity measurements
Epoxidation reactions were carried out in a round bottom glass
batch reactor fitted with a water-cooled condenser, using aqueous
H2O2 (30%) or tert-butyl hydrogenperoxide (TBHP, 70%) as oxidants.
The reactant mixtures of alkenes (3 mmol), oxidant (3 mmol), and
acetonitrile solvent (2 g, dried over 4 Å molecular sieves) were added
to the catalyst (10 wt.% of substrate) and heated in an oil bath at 70 °C,
under magnetic stirring (ca. 800 rpm). After a fixed interval of time,
the reaction mixture was cooled to room temperature and the catalyst
was separated from the reaction mixture by centrifugation. The
oxidized products were analyzed using a gas chromatograph (HP
6890) equipped with a flame ionization detector (FID) and a capillary
column (5 μm cross-linked methyl silicone gum, 0.2 mm×50 m) and
further verified by GC-MS (Shimadzu 2000A).
Table 1
Physico-chemical properties of Sn-containing mesoporous materials.
Sample
Sn content ao
d100
SBET
VP
DP
ωt
(mmol/g)a (Å)b (Å)
(m2 g−1
)
(cm3 g1)c (Å)d (Å)e
Sn–C18–PMO 0.26
Sn–C16–PMO 0.24
Sn–C14–PMO 0.19
58.6 50.1 790
54.8 47.4 786
54.5 47.1 711
41.4 36.0 758
0.79
0.55
0.44
0.49
31.0
27.0
24.0
24.6
27.6
27.8
30.5
16.8
Sn–MCM–41
0.15
a
Determined by AAS analysis.
a0 =2d100/√3.
3. Results and discussion
b
c
Vp =pore volume.
d
e
The powder X-ray diffraction patterns of as-synthesized and
surfactant-extracted tin-containing hybrid mesoporous materials
Dp =pore diameter.
ωt =wall thickness=ao −Dp.

S. Sisodiya et al. / Catalysis Communications 12 (2011) 629–633
631
12
640
560
480
400
320
240
160
80
a
a
A
B
10
8
b
b
6
c
c
4
2
0
0.0
0.2
0.4
P/P0
0.6
0.8
1.0
20
40
60
80
100
Pore diameter / A0
Fig. 2. (A) Nitrogen adsorption–desorption isotherms and (B) pore size distribution of Sn–PMO samples: (a) Sn–C18–, (b) Sn–C16–, (c) Sn–14–PMO. The Sn–C18– and Sn–C16–PMO
isotherm is up shifted to +40 and +55 from Y-axis, respectively.
Si– fragments. These results suggest the stability of the mesoporous
framework that no silicon–carbon bond cleavage of the BTEE precursor
occurred during the synthesis or later on surfactant extraction pro-
cedures [6].
UV–Vis analysis was conducted to elucidate the coordination
environment of tin inside the organosilica samples (Fig. 3). The UV–
Visible spectra of Sn–PMO materials showed a sharp absorption band
at 220 5 nm revealing the presence of tin in tetrahedral coordina-
tion [19,22]. However, broad bands above 280 nm for Sn–C14–, Sn–
C16–, and Sn–MCM-41 materials can be assigned to higher coordi-
nated tin sites similar to SnO2 [23]. These results supports our earlier
hypothesis that smaller alkyl chain length surfactants produce small
pore channels and are unable to incorporate all the added tin species
into the framework, thus may form on the support surface as
nanosized SnO2 species. Alternatively, XPS spectra of Sn–PMO showed
peak at binding energy of ~486.6 eV (Sn 3d5/2) characteristic of tin
(IV) mainly in tetrahedral coordination and thereby confirms the well
dispersion of tin inside the PMO matrix [24,25].
280
A
B
215
350
d
c
b
a
200
300
400
500
600
200
300
400
500
600
Wavelength / nm
Fig. 3. UV–vis spectra of (A) Sn–PMO samples (a) Sn–C18–, (b) Sn–C16–, (c) Sn–C14–PMO, (d) Sn–MCM–41; (B) SnO2.
b
a
A
B
C
100
90
80
70
60
50
40
b
a
b
a
200
400
600
800
200
400
600
800
1000
200
400
600
800
1000
Temperature / °C
Temperature / °C
Temperature / °C
Fig. 4. (A) Thermo gravimetric, (B) differential thermo gravimetric, and (C) differential thermal analysis plots of Sn–C18–PMO samples, (a) as-synthesized (b) extracted.

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S. Sisodiya et al. / Catalysis Communications 12 (2011) 629–633
Table 3
Thermal analysis (TG-DTA) of as-synthesized as well as surfactant
Epoxidation of cis-cyclooctene over tin-containing mesoporous catalyst.
extracted Sn–C18–PMO samples, conducted in air from room temper-
ature to 1000 °C, showed a weight loss below 100 °C accounting for the
loss of physisorbed water molecules (Fig. 4). The significant second
weight loss that occurred in the region 150–430 °C can be attributed to
the removal of surfactant in the as-synthesized Sn–C18–PMO, supported
by the sharp exothermic peaks in their DTA plots (Fig. 4). However, no
weight loss in the range of 150–430 °C was observed from the surfactant
extracted Sn–C18–PMO (Fig. 4A, plot b), which implies that solvent
extraction process had removed the entire surfactant groups, in well
agreement with the NMR results. Meanwhile, the matrix decomposition
(the loss of –CH2–CH2– fragments bonded in the frame walls) in both
samples were observed in the range of 500–700 °C, suggesting that the
Sn–PMO samples are thermally stable up to ~500 °C. The hydrothermal
stability of Sn–PMO was evaluated by refluxing the materials in water
(1 g/100 ml) for various time periods and the changes were compared
with a Sn–MCM-41 material. XRD patterns showed that the organosi-
licas retain its structural ordering even after 100-h reflux in boiling
water, whereas the mesopore structure of Sn–MCM-41 gets completely
destroyed after 24-h reflux time. The higher hydrothermal stability of
the organosilicates unambiguously arise from the presence of the
homogeneously dispersed organic groups in the frame wall positions,
which may enhance the hydrophobicity of the materials than the
conventional Sn–MCM-41.
Above-described various characterization techniques revealed
that tin exists as tetrahedral environment in the Sn–PMO matrix
and hence the materials were screened in the epoxidation reactions of
cis-cyclooctene and norbornene using H2O2 and TBHP as oxidants.
Table 2 presents the epoxidation results of norbornene over Sn–PMO
catalysts using TBHP as oxidant at 70 °C in presence of acetonitrile
solvent. The major product for norbornene epoxidation reaction was
exo-2,3-epoxy norbornene with minor quantities of endo-2,3-epoxy
norbornene and exo-+endo-norborneol [26]. As shown in Table 2,
Sn–C18–PMO exhibits higher catalytic activity and selectivity for exo-
2,3-epoxy norbornene than Sn–C16–, Sn–C14–PMO, and Sn–MCM-41
catalysts. In the absence of catalyst, only minor conversion (~2.2%) of
norbornene was obtained. Interestingly, it was noted that the
turnover numbers for Sn–PMO catalyst increase with an increase in
the tin content, which suggest that all the metal sites were equally
active and well dispersed inside the PMO matrix. Table 3 further lists
the catalytic results of the epoxidation of cis-cyclo-octene over Sn–
PMO catalysts. Among the catalyst screened using H2O2 as an oxidant,
Sn–C18–PMO exhibited higher catalytic activity compared to the Sn–
Sample
H2O2
TBHP
Cyclooctene TONa Epoxide
Cyclooctene TON Epoxide
selectivity conversion selectivity
conversion
(Wt.%)
(%)
(%)
(%)
No catalyst
5.0
–
99
99
99
99
99
5.0
–
99
Sn–C18–PMO 24.0
Sn–C16–PMO 21.4
Sn–C14–PMO 15.2
Sn–MCM–41 12.2
73.0
71.8
64.3
62.5
19.6
16.8
14.8
10.1
59.8 100
56.4
62.7
51.7
99
99
99
Reaction conditions: catalyst (g): 0.033; cyclooctene: oxidant (mol): 1; CH3CN (g): 2;
reaction temperature (°C): 70; time (h): 24.
a
Turnover number (moles of cis-cyclooctene converted per mole of Sn atom).
comparable. In the absence of catalyst or by using Sn–MCM-41 as
catalyst, low cis-cyclooctene conversion was observed. Further, the
lower cis-cyclooctene conversion obtained with TBHP than H2O2
oxidant can be related to (a) lower percentage of active oxygen
content in TBHP than in the H2O2 oxidant; (b) active site poisoning
due to the interaction of catalyst with tert-butylalcohol, a by-product
formed from the decomposition of TBHP [27].
The high conversion of cis-cyclooctene and norbornene over Sn–
C18–PMO can be attributed to the higher tin concentration, better
accessibility of reactants to the active sites due to large pore size and
tetrahedral coordination of tin species when using C18– surfactant
compared to the C16– and C14– surfactants [17]. The epoxidation
results confirmed that tetrahedrally coordinated Sn4+ species
possibly form the catalytically active peroxo intermediates with the
oxidants similar to the Ti4+ sites in TS-1 catalysts [28]. Besides, it is
known that the structural ordering can also influence the catalytic
properties of porous materials, since for a structurally ordered
material, all the active sites are readily available for the diffused
reactant species [29]. Hence, in the present case, any of the above
factors or a combination of both may result in higher conversion of
olefins over C18– templated Sn–PMO catalyst.
In order to evaluate the reusability of the Sn–PMO samples, the
Sn–C18–PMO catalyst was filtered off, washed with acetonitrile, dried
at 100 °C for 3 h, and were reused up to three times. Results up to the
third cycle showed that the catalyst retained nearly identical
conversion and selectivities, revealing that the Sn–PMO catalyst is
highly reusable (Table 4). Hot filtration experiments were addition-
ally conducted to elucidate the leaching of tin species in Sn–C18–PMO
and Sn–MCM-41 during epoxidation reactions [30]. Results showed
that the reaction ceased after the removal of Sn–PMO catalyst, while
Sn–MCM-41 showed an increase in the conversion even after removal
of the catalyst (Fig. 5). Hence, the present investigation suggests that
by making more hydrophobic environment inside mesoporous
matrices, the leaching of active metal sites can be greatly reduced.
C16– and Sn–C14–PMO; however, the selectivity for epoxide was
Table 2
Epoxidation of norbornene over tin-containing mesoporous catalyst.
Catalyst
Norbornene TONa
conversion
(wt.%)
Product selectivity (%)
exo-2,3-
endo-2,3-
exo-+endo-
Epoxy
Epoxy
Norborneol
Table 4
norbornene norbornene
Recyclability study of Sn–C18–PMO catalyst in the epoxidation of cis-cyclooctene.
No catalyst
2.2
–
99
–
–
Entry
Cycle
Cyclooctene conversion (wt.%)
Epoxide selectivity (%)
Sn–C18–PMO 39.2
Sn–C16–PMO 32.5
Sn–C14–PMO 25.3
119.0 98.5
109.0 93.5
107.1 88.6
97.7 92.2
1.5
4.3
8.2
3.8
–
2.2
3.1
4.0
1
2
3
4
Fresh
24.0
22.8
22.1
21.7
99
99
99
99
1st cycle
2nd cycle
3rd cycle
Sn–MCM–41
19.1
Reaction conditions: catalyst (g): 0.033; norbornene: oxidant (mol): 1; CH3CN (g): 2;
reaction temperature (°C): 70; time (h): 10.
Reaction conditions: catalyst (g): 0.033; cyclooctene: H2O2 (30%) (mol): 1; CH3CN (g):
2; reaction temperature (°C): 70; time (h): 24.
a
Turnover number (moles of norbornene converted per mole of Sn atom).

S. Sisodiya et al. / Catalysis Communications 12 (2011) 629–633
633
14
Fresh cycle
Fresh cycle
Hot filtration test
25
20
15
10
5
12
10
8
Hot filtration test
6
4
2
0
0
0
5
10
15
20
25
30
0
5
10
15
20
25
30
Time/ h
Time/ h
Fig. 5. Leaching/Hot filtration test studies performed over tin-containing hybrid catalysts in epoxidation reaction of cis-cyclooctene, (A) Sn–C18–PMO, (B) Sn–MCM–41; reaction
conditions: catalyst (g): 0.033; cyclooctene: H2O2 (30%) (mol): 1; CH3CN (g): 2; reaction temperature (°C): 70; time (h): 24.
[2] J.Y. Ying, C.P. Mehnert, M.S. Wong, Angew. Chem. Int. Ed Engl. 38 (1999) 56–77.
[3] F. Hoffmann, M. Cornelius, J. Morell, M. Froba, Angew. Chem. Int. Ed Engl. 45
4. Conclusions
(2006) 3216–3251.
Tin-containing mesoporous materials having –CH2–CH2– groups
in the frame wall positions were successfully synthesized using
cationic surfactants of differed chain lengths. Characterization results
demonstrated that the periodic mesoporous structure as well as the
framewall organic groups remained intact after the removal of
surfactant species and were thermally stable up to 500 °C. Spectro-
scopic characterization techniques confirmed that tin resides as
tetrahedral environment in Sn–PMO samples whereas lower alkyl
chain surfactants showed the formation of agglomerated tin sites.
Catalyst screening in the epoxidation reaction of cis-cyclooctene and
norbornene revealed that Sn–C18–PMO exhibits excellent catalytic
activity and reusability than an Sn–MCM-41 sample. The higher
catalytic activity and stability of Sn–C18–PMO were related to the
higher tin incorporation, better accessibility of reactants to the active
sites, and more hydrophobic environment induced inside the pore
channels of PMO matrix due to the presence of organic groups in the
frame wall positions.
[4] D.A. Loy, K.J. Shea, Chem. Rev. 95 (1995) 1431–1442.
[5] R.J.P. Corriu, Angew. Chem. Int. Ed Engl. 39 (2000) 1376–1398.
[6] S. Inagaki, S. Guan, Y. Fukushima, T. Ohsuna, O. Terasaki, J. Am. Chem. Soc. 121
(1999) 9611–9614.
[7] T. Asefa, M.J. MacLachlan, N. Coombs, G.A. Ozin, Nature 402 (1999) 867–871.
[8] B.J. Melde, B.T. Holland, C.F. Blanford, A. Stein, Chem. Mater. 11 (1999)
3302–3308.
[9] T. Asefa, M.J. MacLachlan, H. Grondey, N. Coombs, G.A. Ozin, Angew. Chem. Int. Ed
Engl. 39 (2000) 1808–1811.
[10] S. Inagaki, S. Guan, T. Ohsuna, T. Terasaki, Nature 416 (2002) 304–307.
[11] K.M. Reddy, I. Moudrakovski, A. Sayari, J. Chem. Soc., Chem. Commun. (1994)
1059–1060.
[12] P. Selvam, S.E. Dapurkar, J. Catal. 229 (2005) 64–71.
[13] Z. Luan, J. Xu, H. He, J. Klinowski, L. Kevan, J. Phys. Chem. 100 (1996)
19595–19602.
[14] V. Ramaswamy, P. Shah, K. Lazar, A.V. Ramaswamy, Catal. Surv. Asia 12 (2008)
283–309.
[15] A. Bhaumik, M.P. Kapoor, S. Inagaki, Chem. Commun. (2003) 470–471.
[16] M.P. Kapoor, A.K. Sinha, S. Seelan, S. Inagaki, S. Tsubota, H. Yoshida, M. Haruta,
Chem. Commun. (2002) 2902–2903.
[17] S. Shylesh, A.P. Singh, Micropor. Mesopor. Mater. 94 (2006) 127–138.
[18] S. Shylesh, Ch. Srilakshmi, A.P. Singh, B.G. Anderson, Micropor. Mesopor. Mater. 99
(2007) 334–344.
[19] P.P. Samuel, S. Shylesh, A.P. Singh, J. Mol. Catal. A: Chem. 266 (2007) 11–20.
[20] S. Hamoudi, Y. Yang, I.L. Moudrakovski, S. Lang, A. Sayari, J. Phys. Chem. B 105
(2001) 9118–9123.
Acknowledgments
[21] M. Kruk, M. Jaroniec, A. Sayari, J. Phys. Chem. B 101 (1997) 583–589.
[22] X. Wang, H. Xu, X. Fu, P. Liu, F. Lefebvre, J.-M. Basset, J. Mol. Catal. A: Chem. 238
(2005) 185–191.
[23] K. Chaudhari, T.K. Das, P.R. Rajmohnana, K. Lazer, S. Sivasanker, A.J. Chandwadkar,
J. Catal. 183 (1999) 281–291.
The authors are grateful to Dr. Ajithkumar, Dr. K.R. Patil, and
Mr. R.K. Jha for their assistance in useful discussion with NMR, XPS, and
surface area analysis, respectively.
[24] G. Luo, S. Yan, M. Riao, K. Fan, Appl. Catal. A: Gen. 332 (2007) 79–88.
[25] A. Patel, G. Koudurier, N. Essayem, J.C. Vedrine, J. Chem. Soc. Faraday Trans. 93
(1997) 347–353.
Appendix A. Supplementary data
[26] O. Muth, C. Schellbach, M. Froba, Chem. Commun. (2001) 2032–2033.
[27] S. Shylesh, P.P. Samuel, A.P. Singh, Catal. Commun. 8 (2007) 894–898.
[28] S.C. Laha, R. Kumar, J. Catal. 204 (2001) 64–70.
Supplementary data to this article can be found online at
doi:10.1016/j.catcom.2010.11.025.
[29] V. Parvulescu, C. Anastasescu, B.L. Su, J. Mol. Catal. A: Chem. 198 (2003) 249–261.
[30] M.P. Kapoor, A. Bhaumik, S. Inagaki, K. Kuraoka, T. Yazawa, J. Mater. Chem. 12
(2002) 3078–3083.
References
[1] C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vartuli, J.S. Beck, Nature 359 (1992)
710–712.