Synthesis of hierarchical ZSM-5 using glucose as a templating precursor

Article abstract of DOI:10.1039/c3ta13904b

Various hierarchical ZSM-5 materials have been synthesized by adopting a novel concept using glucose as a precursor for the structure directing agent through a steam-assisted crystallization (SAC) process. The effect of the glucose/TEOS weight ratio was studied, and materials exhibiting different properties such as surface area, porosity and acidity were obtained by varying the concentration of glucose in the initial synthesis mixture. All the samples were characterized by XRD, SEM, TPD, and N₂ adsorption-desorption and were studied for their performance towards the tertiary butylation of phenol reaction. The activities of all the hierarchical ZSM-5 materials synthesized by the present method were observed to be higher than that of the conventional ZSM-5. The optimal production of 2,4-di-tertiary butyl phenol over hierarchical ZSM-5 occurred at a reaction temperature of 150 °C after 7 h reaction time under solvent free conditions.

Full text of DOI:10.1039/c3ta13904b

Journal of
Materials Chemistry A
View Article Online
View Journal | View Issue
PAPER
Synthesis of hierarchical ZSM-5 using glucose as a
templating precursor†
ab
Cite this: J. Mater. Chem. A, 2014, 2,
054
1
b
ab
Devaki Nandan, Sandeep K. Saxena and Nagabhatla Viswanadham*
Various hierarchical ZSM-5 materials have been synthesized by adopting a novel concept using glucose as a
precursor for the structure directing agent through a steam-assisted crystallization (SAC) process. The
effect of the glucose/TEOS weight ratio was studied, and materials exhibiting different properties such as
surface area, porosity and acidity were obtained by varying the concentration of glucose in the initial
2
synthesis mixture. All the samples were characterized by XRD, SEM, TPD, and N adsorption–desorption
and were studied for their performance towards the tertiary butylation of phenol reaction. The activities
of all the hierarchical ZSM-5 materials synthesized by the present method were observed to be higher
than that of the conventional ZSM-5. The optimal production of 2,4-di-tertiary butyl phenol over
Received 27th September 2013
Accepted 30th October 2013
DOI: 10.1039/c3ta13904b
ꢀ
hierarchical ZSM-5 occurred at a reaction temperature of 150 C after 7 h reaction time under solvent
www.rsc.org/MaterialsA
free conditions.
hierarchical pore zeolite is by adopting special chemicals as
1
. Introduction
templates including hard and supramolecular structured
7
Zeolites, with their inherent porous crystalline acidic nature, compounds. Jacobsen et al. did pioneering work on the hard
possessing uniform pore sizes and large internal surface areas, templating method and successfully synthesized mesopore

nd a wide range of applications in catalysis, separation and zeolites using carbon materials such carbon nano-tubes.
1
–3
ion-exchange. In particular, the medium pore ZSM-5 zeolite Three-dimensionally ordered mesoporous (3DOM) carbon
has attracted much attention due to its shape-selective materials are also used by other researchers for the synthesis
8
features responsible for its excellent performance in selective of mesoporous zeolite materials. Nevertheless, the templates
9
organic transformations. The narrow pores of this zeolite used in these methods are very costly. Carbon aerogels and
1
0,11
exhibiting linear selectivity provide a special feature for the ordered mesoporous carbons
have also been used as
synthesis of para-xylene from ortho- and meta-xylenes, which is templates to prepare hierarchical zeolite, but the preparation
considered as a milestone in zeolite and heterogeneous process of this carbon template itself is complicated and
catalysis research elds. However, an obvious shortcoming of requires high temperature and an inert gas atmosphere during
zeolite materials originates from their intrinsic micropores carbonization. In the supra-molecular templating method, the
that strongly inhibit the diffusion of bulky reactants and templates used are mainly cetyltrimethylammoniumbromide
1
2
products, which prevents their wide use in ne chemical and (CTABr), poly(ethylene oxide)–poly(propylene oxide)–poly-
1
3
petrochemical processing. Al-containing mesoporous molec- (ethylene oxide) triblock copolymer (P123), and organo-
1
4
ular sieves with large and high specic surfaces could be the silane agents, but these are expensive. Recently, through the
4
–6
catalysts for the conversion of bulky reactants. However, combination of conventional so templates such as TEA,
these materials suffer from poor thermal and hydrothermal copolymer Pluronic F127, organosilane and the steam-assisted
stability due to the thin and amorphous nature of their walls. crystallization (SAC) process, hierarchically structured c-TUD-
1
5
Therefore, the preparation of hierarchical pore zeolite molec- 1, TS-1 and ZSM-5 zeolites have been facilely produced, but
ular sieves possessing the positive aspects of both micropores the use of these templates makes the process costly. Very
(
high activity and stability) and mesopores (larger pore size for recently, monosaccharides such as glucose and disaccharides
accommodating bulky molecules) has become a hot point of such as sucrose etc. have been identied as cheaper potential
research recently. The most widely used method to prepare precursors for mesopore structure-directing agents. Kustova
1
6
et al. synthesized zeolite single crystals with controlled
mesoporosity by in situ sugar decomposition for the templat-
ing of hierarchical zeolites which is a three step process in
a
b
AcSIR-Indian Institute of Petroleum, Dehradun, India
Catalyst and Conversion Processes Division, Indian Institute of Petroleum, Council of
Scientic and Industrial Research, Dehradun-248005, India. E-mail: nvish@iip.res.in; which they rst synthesized a silica–carbon composite in an
Fax: +91-135-2525702; Tel: +91-135-2525856
Electronic supplementary information (ESI) available: Low angle XRD of
synthesized samples. See DOI: 10.1039/c3ta13904b
inert atmosphere and used this composite material as a
template upon which crystallization and calcination yields
†
1054 | J. Mater. Chem. A, 2014, 2, 1054–1059
This journal is © The Royal Society of Chemistry 2014

View Article Online
Paper
Journal of Materials Chemistry A
Na–ZSM-5. The material was further treated with ammonium 2.2. Synthesis of hierarchical ZSM-5 materials
nitrate to obtain NH –ZSM-5, and the high temperature
4
As depicted in Scheme 1, a typical synthesis procedure involves the
1
7
decomposition nally yielded H–ZSM-5. Ma et al. synthesized
mesoporous ZSM-5 where a precursor of ZSM-5 is rst
prepared by a sequential reaction between aluminium
sulphate solution, tetrapropylammonium hydroxide and tet-
raethyl orthosilicate in a specic manner. The resultant ZSM-5
precursor was added to an aqueous solution of glucose
followed by heating to the crystallization temperature. The
drop by drop admixing of tetrapropylammonium bromide (TPABr)
solution, tetraethyl orthosilicate (TEOS), aluminium nitrate solu-
tion and glucose solution with a TPABr : TEOS : aluminium
nitrate : glucose : water molar ratio of 1 : 5.2 : 0.215 : 2.4 to
ꢀ
4
.9 : 60. The resultant gel is treated at 170 C in air and the dry gel
obtained from the mixture is used for steam assisted crystalliza-
tion in a specially designed autoclave equipped with a porous
metallic boat for holding the dry gel which is allowed to be in
contact with the steam produced from the bottom of the autoclave
during heat treatment (Scheme 1). In a typical synthesis procedure

nal solid product obtained was calcined to remove the
organic template, followed by ion exchange with NH NO and
4
3
calcination treatment to yield H–ZSM-5. A similar method was
also reported, the difference being the use of starch derived
bread instead of glucose for the synthesis of the hierarchical
1
2.5 g tetrapropylammonium bromide with the required amount
of glucose and water is added to TEOS followed by the addition of
.75 g of aluminium nitrate solution (in 5 g water). To study the
1
9,20
ZSM-5 (ref. 18). Wang et al.
synthesized hierarchical TS-1 by
3
using sucrose as a meso/macro template in the presence of
isopropyl alcohol, using high cost ethylendiamine as a
crystallising agent. Previously, we successfully synthesized
mesoporous silica by using glucose as a template precursor in
effect of the template precursor (glucose) the synthesis was
conducted by varying the glucose to TEOS weight ratio in the initial
gel mixture from 0.40 to 0.64. The resultant solution was dried in a
ꢀ
water bath by treating at 80 C for 2 h, and the resulting viscous gel
2
1
an acidic medium. However, the same method is not
applicable for the synthesis of mesoporous ZSM-5 due to the
fact that the metal to metal (silicon and aluminium) bond
formation is difficult in an acidic medium to yield any
crystalline material.
ꢀ
was further heated at 170 C for 28 h to obtain the dry gel (brown in
colour). Finally, the dry gel (solid phase), along with a mixture of
aqueous ammonia (25%) and deionized water containing the
aqueous phase were transferred into a specially designed auto-
clave, in which the solid phase was separated from the aqueous
Here, we report a novel method for the successful synthesis
of hierarchical ZSM-5 zeolite material using environmentally
benign glucose in a basic medium created by the addition of
low cost aqueous ammonium hydroxide, where the pore size
pattern of the synthesized material is signicantly inuenced
by the concentration of glucose in the synthesis mixture. The
present work has an advantage over the existing methods as it
uses a simple, low cost, non-surfactant common chemical
ꢀ
phase. The crystallization was carried out at 170 C for 6 days, and
the steam obtained from the aqueous phase came in contact with
the upper solid phase to facilitate the crystallization process of the
zeolite. At the end of the treatment, the black coloured solid
product obtained was collected by ltration, washed with deion-
ꢀ
ꢀ
ized water, dried at 100 C and calcined at 650 C for 10 h to
remove the template. The nal materials obtained in the synthesis
are denoted MZ0.40, MZ0.48 and MZ0.64, where the suffix
indicates the weight ratio of glucose to TEOS.
“
glucose” as the template precursor that spontaneously gets
converted to a hard template during partial carbonization by
ꢀ
drying of the synthesis gel at 170 C in air. Furthermore, the
2.3. Characterisation
use of ammonium hydroxide as an alkaline agent instead of
sodium hydroxide makes it simple to obtain the proton form The powder X-ray diffraction patterns of the samples were
of ZSM-5 directly and avoids the additional step of ion- recorded on a Regaku Dmax III B equipped with a rotating
exchange of sodium with ammonium ions. The ammonium anode and CuKa irradiation. SEM images were recorded for
form of ZSM-5 obtained in the synthesis gets transformed into obtaining the particle morphology on a Quanta 200f instru-
acidic ZSM-5 (H–ZSM-5) through the simple decomposition of ment, Netherlands. Nitrogen sorption isotherms were obtained
the ammonium ion during calcination. This is the rst using a Micromeritics ASAP 2010 unit, USA, operated at
ꢀ
ꢀ
method of its kind to synthesize crystalline hierarchical ꢁ196 C, where the samples were degassed at 300 C prior to
aluminosilicate material from a glucose and ammonium measurement to determine the specic BET surface area (SBET)
hydroxide medium to the best of our knowledge. The catalytic and pore volume. The pore size was calculated from the
performance of hierarchical ZSM-5 samples was studied for
the bulky molecular alkylation reaction of phenol with tertiary
butanol.
2. Experimental
2.1. Materials
Tetraethyl ortho silicate (TEOS), ammonia solution, 25%, tet-
rapropylammonium bromide (TPABr), phenol, tertiary butanol
and aluminium nitrate were purchased from Merck while
glucose was purchased from Rankem, The reference ZSM-5
sample was obtained from Sud-Chemie India Ltd.
Scheme 1 Synthesis route of hierarchical ZSM-5 zeolite.
This journal is © The Royal Society of Chemistry 2014
J. Mater. Chem. A, 2014, 2, 1054–1059 | 1055

View Article Online
Journal of Materials Chemistry A
Paper
desorption branch of the adsorption–desorption isotherms by
the Barrett–Joyner–Halenda (BJH) method. The temperature
programmed desorption (TPD) patterns of ammonia on the
samples were recorded on Micromeritics 2010 unit, USA, where
helium was used as the carrier gas and prior to the ammonia
ꢀ
adsorption the samples were degassed at 300 C for one hour.
2.4. Application of materials for the tertiary butylation of
phenol
The catalyst performance studies of the materials were con-
ducted in the present work towards the alkylation of phenol. In
a typical reaction procedure, 1 mol of phenol was added to a
2.5 mol of tertiary butyl alcohol and 5 mol% of catalyst. The
whole mixture was transferred in to a 25 ml volume capacity
Parr reactor autoclave, sealed tightly and pressurised by N up
2
ꢀ
to 2 bar. The reaction was conducted at 150 C for 7 h and the
product obtained at the end of the run was ltered and analysed
by GC equipped with a DB wax column and ame ionisation
detector (FID).
3. Results and discussion
3.1. Crystallinity, porosity and acidic properties of the
synthesised materials
The SEM images of the samples shown in Fig. 1 indicate the
formation of uniform crystals in the case of MZ0.40, when
compared to those of MZ0.48 and MZ0.64. This can be ascribed
to the variation in the concentration of the templating
precursor, glucose, in the synthesis gel. The non-uniform
distribution of the templating precursor resulting in excess
glucose concentration may be the reason for the formation of
non uniform semi-crystalline ZSM-5 materials. The powder
X-ray diffraction (XRD) patterns of the samples are given in
Fig. 2, where a standard ZSM-5 sample of Si/Al ¼ 15 is also
shown for comparison. All three synthesized materials depict
the characteristic diffraction peaks occurring at 2q of 8.0, 8.9,
23.2, 24 and 24.5 representing the ZSM-5 framework structure
without any crystalline impurity phases. The crystallite size of
the materials was estimated from the full width at half maxima
of the respective peaks at 2q values of 7–10, using Scherrer's
equation, and the average of the crystallite size is given in Table
1. The data indicate a comparable crystal size of the materials
synthesized in this study with that of the conventional ZSM-5
zeolite. The small angle X-ray scattering (SAXS) patterns of the
as-synthesized samples (Fig. S1, ESI†) suggest the presence of
22
larger mesopores in the materials, which is indeed conrmed
by N adsorption–desorption isotherm curves of the corre-
2
sponding samples (Fig. 3A). All the samples exhibited the type
IV isotherm with an H1 type hysteresis loop which is usually
observed for larger mesopores. The sharp uptake in nitrogen
Fig. 1 SEM images of the synthesized materials.
0
adsorption at relative pressures of 0.6–0.9 P/P reveals the
capillary condensation of the gas inside the mesopores. A steep
increase at relative pressure P/P0 < 0.02 and signicant
adsorption at high relative pressure P/P 0.9–1.0, indicates the the initial synthetic gel was observed to inuence the porosity of
0
co-existence of intrinsic micro, meso and macropores in all the samples signicantly. At lower glucose concentration, the
three samples. However, the concentration of glucose in isotherm exhibited the formation of more micropores (pressure
1056 | J. Mater. Chem. A, 2014, 2, 1054–1059
This journal is © The Royal Society of Chemistry 2014

View Article Online
Paper
Journal of Materials Chemistry A
Fig. 2 Wide angle XRD patterns of the synthesized materials.
0
range of P/P < 0.02), while at higher glucose concentration the
porosity dramatically shied into meso/macropores (relative
pressure range P/P of 0.6–0.9). This phenomenon of enhanced
0
mesopore/macropore formation at higher glucose concentra-
tions is further reected in the pore size distribution patterns of
the materials (Fig. 3B). All the materials exhibited hierarchical
pore size distribution patterns with signicant contribution of
mesopores as well as macropores (Fig. 3B). However, the pop-
ulation of such hierarchical pores is dramatically increased in
the samples using more glucose and the increase follows the
glucose concentration. Therefore the order of hierarchical
porosity is observed to be as follows: ZSM-5 < MZ0.40 < MZ0.48 <
MZ0.64. The nding of increasing hierarchical pore size
Fig. 3 (A) N
2
adsorption–desorption isotherms of the synthesized
materials, (B) pore size distributions of the samples measured by the
BJH method.
distribution with increasing glucose concentration can be is indeed observed in the samples (Table 1). However, it is
understood from the XRD results, where the increase in glucose important to note that the total pore volume as well as the
concentration is observed to increase the amorphous nature of mesopore/macropore volume is increased in the higher glucose
the material (lower crystallinity). This is to say that the semi based synthesized samples. This results in an overall increase in
crystalline ZSM-5 material containing a larger amount of the average pore diameter of the samples with increasing
amorphous material is forming at a higher glucose concentra- glucose concentration. The BJH adsorption average pore diam-
tion and the presence of such amorphous material is contrib- eters of the corresponding samples are 2.2, 2.3, 6.7 and 7.2 nm,
uting to the formation of meso and macropores. Such a material further suggesting that an increase of glucose concentration
with a lower number of micropores and higher numbers of leads to a shi of the mean pore diameter to a higher value. Here,
meso/macropores is expected to give a lower surface area, which glucose undergoes dehydration and partial carbonization to
Table 1 Textural properties of the synthesized materials
a
2
ꢁ1
b
2
ꢁ1
c
2
ꢁ1
d
3
ꢁ1
e
3
ꢁ1
f
3
ꢁ1
g
h
Sample
SABET /m g
SAmi /m g
SAme /m g
V
tot /cm g
V
mi /cm g
V
me/ma /cm g
D /nm
Crystallite size /nm
ZSM-5
294
305
107
128
207
113
25
87
192
82
0.18
0.18
0.18
0.23
0.08
0.05
0.01
0.01
0.10
0.13
0.17
0.22
2.2
2.3
6.7
7.2
50.3
51.7
57.0
47.4
MZ0.40
MZ0.48
MZ0.64
42
86
a
b
c
d
BET surface area. Micropore surface area calculated from t-plot. Mesopore surface area calculated as SABET ꢁ SAmi
.
Total pore volume taken
e
f
from the volume of N
2
adsorbed at P/P
0
¼ 0.995. Micropore volume calculated from t-plot. Mesopore/macropore volume calculated by Vtot ꢁ Vmi
.
g
h
BJH adsorption average pore diameter. Average crystal size determined using Scherrer's equation for the peaks at 2q values of 7–10.
This journal is © The Royal Society of Chemistry 2014
J. Mater. Chem. A, 2014, 2, 1054–1059 | 1057

View Article Online
Journal of Materials Chemistry A
Paper
a
form templating carbonaceous species during the heat treatment Table 2 tert-Butylation of phenol over hierarchical ZSM-5 samples
ꢀ
of the gel at 170 C, which is responsible for the creation of meso/
Selectivity of product (%)
macropores in the nal material upon steam assisted crystalli-
Conversion of
zation. The formation of such meso/macropores is increased Catalyst
with an increased concentration of glucose. Overall, the
phenol (mol%)
2-TBP
4-TBP
2,4-DTBP
MZ0.40
34
46.6
44
38.2
11.1
10.6
63.5
57.3
81.5
80.9
32.84
4.5
5.4
8.5
Nil
increased formation of meso/macropores with increased glucose
MZ0.48
concentration clearly demonstrates the meso/macropore direct-
MZ0.64
ing role of the glucose precursor.
ZSM-5
13.7
The acidity patterns of the samples measured by TPD (Fig. 4)
a
ꢀ
Catalyst: 0.5 g, reaction temperature 150 C, pressure 2 bar N
reaction time 7 h; phenol : TBA 1 : 2.5 (molar ratio).
2
;
also followed the crystallinity trend of the samples. All the
samples exhibited a two peak pattern with desorption peaks at
ꢀ
ꢀ
ꢂ100 C and ꢂ350 C representing weak and strong acidity,
respectively. The acidity pattern of a reference ZSM-5 sample
(
Si/Al ¼ 15) is also given for comparison, showing that the
environmentally-friendly process, in which the easy separation
of catalysts from the reaction system makes it suitable for
industrial applications. In this regard, hierarchical ZSM-5
acidity of all three samples (Si/Al ¼ 60) in the present study is
lower (lower number of acid sites) compared to the reference
sample, following the aluminium content. Among the three
ZSM-5 samples synthesized in the present study, the acidity is
decreased with increasing glucose concentration. This is in
accordance with the XRD and porosity patterns, as the
increased amorphous nature of the material is expected to give
low acidity (lower number of strong acid sites) to the ZSM-5
samples. The results together summarize the role of glucose as
a meso/macropore directing agent and the partially crystalline
hierarchical ZSM-5 samples obtained at higher glucose loadings
exhibit moderate acidity along with a large number of meso/
macropores. With the higher pore volume and larger space in
the mesopores, the samples are expected to exhibit potential
catalytic applications in molecular reactions involving bulky
species, such as the tertiary butylation of phenol.
23
samples are observed to exhibit excellent catalytic properties,
especially in terms of the di-alkylated product. The hierarchical
mesoporous ZSM-5 samples in the present study, which possess
meso/macroporosity along with zeolitic microporosity, are also
expected to exhibit promising catalytic activity towards this
reaction involving bulky reactants. In the present study we
would like to explore the effect of glucose-dependent meso/
macroporosity created in the ZSM-5 samples on the conversion
and product selectivity towards the tertiary butylation of
phenol. All three hierarchical ZSM-5 samples exhibited higher
conversions (34–46%) when compared to the microporous ZSM-
5
zeolite (Table 2). The lower conversion of microporous ZSM-5
obtained in the reaction in spite of its higher acidity (ESI
Fig. S2†) clearly suggests the importance of meso/macropores
for this reaction and the lack of such porosity in the standard
ZSM-5 sample may be responsible for its lower activity. The
catalytic performance of the three hierarchical mesoporous
ZSM-5 samples also followed the porosity trend, in which the
more meso/macroporous material (MZ0.64) exhibited higher
conversion (44%) and higher 4-TBP (tertiary butyl phenol)
selectivity (81%). This sample also produced the highest
amount of di-alkylated product (2,4-DTBP).
3
.2. Catalytic application of the materials
The tertiary butylation of phenol is catalyzed by conventional
homogeneous acid catalysts in the liquid phase at lower reac-
tion temperatures, but the acid contamination and difficulty
involved in the separation of the product (which also adds to the
cost) limits their use. Recently, solid acid catalysts have been
applied for solvent-free liquid phase reactions for low cost and
4. Conclusions
In summary, hierarchical ZSM-5 zeolite samples have been
successfully synthesized by using the low-cost template
precursor glucose in a basic medium that can be directly con-
verted to a hard template during heat treatment of the gel to
give glucose-dependent porosity patterns in the samples. This
method also provides scope for using other kinds of sugars as
template precursors for the synthesis of hierarchical materials.
The synthesis method provides an economical path for the
production of hierarchical aluminosilicates with tailored meso/
macroporosity (controlled by glucose) for various industrial
applications and could be extended for the synthesis of other
types of zeolites. The materials possessing a well-connected
network of micro/meso/macropores could be a source for a
variety of molecular reactions involving bulk species and better
replacements for conventional ZSM-5. The materials indeed
Fig. 4 TPD spectra of synthesised and reference material.
1058 | J. Mater. Chem. A, 2014, 2, 1054–1059
This journal is © The Royal Society of Chemistry 2014

View Article Online
Paper
Journal of Materials Chemistry A
exhibited improved catalytic performance in the tertiary butyl- 10 Z. Yang, Y. Xia and R. Mokaya, Adv. Mater., 2004, 16, 727.
ation of phenol as a result of overcoming the diffusion limita- 11 Y. M. Fang and H. Q. Hu, J. Am. Chem. Soc., 2006, 128, 10636.
tion of the reactants.
12 M. B. Yue, L. B. Sun, T. T. Zhuang, X. Dong, Y. Chun and
J. H. Zhu, J. Mater. Chem., 2008, 18, 2044.
1
3 D. Trong-On, D. Lutic and S. Kaliaguine, Microporous
Mesoporous Mater., 2001, 44, 435.
Acknowledgements
We acknowledge the CSIR for the research funding of the 14 D. Serrano, R. Sanz, P. Pizarroa and I. Morenoa, Chem.
project under 12th FYP. The authors thank the director, IIP, for
Commun., 2009, 1407.
his encouragement. DN acknowledges CSIR, New Delhi, for 15 J. Zhou, Z. Hua, X. Cui, Z. Ye, F. Cui and J. Shi, Chem.
awarding a fellowship. We are thankful to the XRD, Porosim-
etry, and SEM groups at IIP for analysis.
Commun., 2010, 46, 4994; J. Zhou, Z. Hua, Z. Liu, W. Wu,
Y. Zhu and J. Shi, ACS Catal., 2011, 1, 287; J. Zhou, Z. Hua,
J. Shi, Q. He, L. Guo and M. Ruan, Chem.–Eur. J., 2009, 15,
1
2949.
Notes and references
1
6 M. Kustova, K. Egeblad, K. Zhu and C. H. Christensen, Chem.
1
2
3
M. E. Davis, Nature, 2002, 417, 813.
A. Corma, Chem. Rev., 1997, 97, 2373.
Mater., 2007, 19, 2915.
17 Y. Ma, J. Hu, L. Jia, Z. Li, Q. Kan and S. Wu, Mater. Res. Bull.,
2013, 48, 1881.
18 L. Wang, C. Yin, Z. Shan, S. Liu, Y. Du and F. Xiao, Colloids
Surf., A, 2009, 340, 126.
19 W. Wang, G. Li, L. Liu and Y. Chen, Microporous Mesoporous
Mater., 2013, 179, 165.
20 X. Wang, G. Li, W. Wang, C. Jin and Y. Chen, Microporous
Mesoporous Mater., 2011, 142, 494.
21 D. Nandan, P. Sreenivasulu, S. K. Saxena and
P. Yang, D. Zhao, D. Margolese, B. F. Chmelka and
G. D. Stucky, Nature, 1998, 396, 152.
Z. Xue, T. Zhang, J. Ma, H. Miao, W. Fan, Y. Zhang and R. Li,
Microporous Mesoporous Mater., 2012, 151, 271.
Y. H. Kim, K. H. Lee, C. M. Nam and J. S. Lee, ChemCatChem,
4
5
6
7
8
2
012, 4, 1143.
C. M. A. Parlett, K. Wilson and A. F. Lee, Chem. Soc. Rev.,
013, 42, 3876.
2
A. Boisen, I. Schmidt, A. Carlsson, S. Dahl, M. Brorsona and
C. J. H. Jacobsen, Chem. Commun., 2003, 958.
N.
Viswanadham,
Chem.
Commun.,
2011,
47,
11537.
W. Fan, M. A. Snyder, S. Kumar, P. S. Lee, W. C. Yoo, 22 Z. Niu, S. Kabisatpathy, J. He, L. A. Lee, J. Rong, L. Yang,
A. V. McCormick, R. L. Penn, A. Stein and M. Tsapatsis,
G. Sikha, B. N. Popov, T. S. Emrick, T. P. Russell and
Nat. Mater., 2008, 7, 984.
Q. Wang, Nano Res., 2009, 2, 474.
9
Y. Tao, H. Kanoh and K. Kaneko, J. Am. Chem. Soc., 2003, 125, 23 F. Adam, K. M. Hello and T. H. Ali, Appl. Catal., A, 2011,
044.
399, 42.
6
This journal is © The Royal Society of Chemistry 2014
J. Mater. Chem. A, 2014, 2, 1054–1059 | 1059