Double-shelled hollow mesoporous silica nanospheres as an acid-base bifunctional catalyst for cascade reactions

Article abstract of DOI:10.1039/c7nj04670g

Double-shelled hollow mesoporous silica nanospheres (HMS-Al@MS-NH₂) have been successfully obtained using the shell-by-shell strategy, by which the isolated acidic (-Al) and basic (-NH₂) sites were spatially incorporated in different shells. The characterization results indicate that HMS-Al@MS-NH₂ possesses a hollow void and mesopores in both shells, and this favors the mass transfer of the reactants and products. As a spatially isolated acid-base bifunctional catalyst, HMS-Al@MS-NH₂ proved to exhibit high catalytic performances in the one-pot deacetalization-Knoevenagel cascade reaction. Under the optimized conditions, the conversion of benzaldehyde dimethyl acetal approached ca. 100% for 2 h at 110 °C, mainly attributed to the isolated acidic and basic sites and to the hollow architecture and mesopores in the shells. Notably, the catalyst could be reused up to 4 times without obvious loss of activity and selectivity, indicating the high stability of the active acidic and basic sites in the framework. Moreover, the double-shelled hollow mesoporous silica spheres are also active and selective for the other cascade sequence of the deacetalization-Henry reaction.

Full text of DOI:10.1039/c7nj04670g

View Article Online
View Journal
NJC
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: C. You, C. Yu, X.
yang, Y. Li, H. Huo, Z. Wang, Y. Jiang, X. Xu and K. Lin, New J. Chem., 2018, DOI: 10.1039/C7NJ04670G.
Volume 40 Number
1
January 2016 Pages 1–846
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
NJC
New Journal of Chemistry
www.rsc.org/njc
A journal for new directions in chemistry
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
rsc.li/njc

Please do not adjust margins
New Journal of Chemistry
Page 1 of 8
View Article Online
DOI: 10.1039/C7NJ04670G
NJC
ARTICLE
Double-shelled hollow mesoporous silica nanosphere as acid-base
bifunctional catalyst for cascade reactions
Received 00th January 20xx,
Accepted 00th January 20xx
a,1
a,1
a
a
a
a
a,
Chunzi You , Chunqi Yu , Xiaohui Yang , Yudong Li , Hang Huo , Zhe Wang , Yanqiu Jiang, *
a,
a,b
Xianzhu Xu, * and Kaifeng Lin
DOI: 10.1039/x0xx00000x
Double-shelled hollow mesoporous silica nanosphere (HMS-Al@MS-NH
shell strategy, by which the isolated acidic (-Al) and basic (-NH ) sites were spatially incorporated in different shells. The
characterization results indicate that HMS-Al@MS-NH possesses hollow void and mesopores in both shells, which favor
the mass transfer of the reactants and products. As a spatially isolated acid-base bifunctional catalyst, HMS-Al@MS-NH
2
) has been successfully obtained using shell-by-
www.rsc.org/
2
2
2
proved to exhibit high catalytic performances in one-pot deacetalization-Knoevenagel cascade reaction. Under the
o
optimized conditions, the conversion of benzaldehyde dimethyl acetal approached ca.100% for 2 h at 110 C, mainly
attributed to the isolated acidic and basic sites and to the hollow architecture and mesopores in the shells. Notably, the
catalyst could be reused up to 4 times without obvious loss of activity and selectivity, pointing to the high stability of the
active acidic and basic sites in the framework. Moreover, the double-shelled hollow mesoporous silica spheres are also
active and selective for the other cascade sequence of deacetalization-Henry reaction.
3
5-43
nicely addressed to some extent.
Moreover, either the core or
Introduction
the shell precisely contains the different active sites. For instance,
2
8
2 3
Yang et al. reported a base core (-NH ) and an acidic shell (-SO H)
Cascade reaction is a one-pot procedure that allows at least two
reactions to proceed consecutively without any isolation of
intermediates. This process can not only shorten the synthetic route
but also decrease the content of gratuitous waste with high atom
were located in yolk-shell nanoreactor by organosilane-assisted
selective etching method, which showed high catalytic activity in a
6
one-pot deacetalization-Henry cascade reaction. Also, Song et al.
1
, 2
reported another yolk-shell nanosphere with the acid sites and the
basic groups in the inner core and the outer shell, respectively,
which led to further activity and selectivity due to the reasonable
spatial order of acid-base sites for cascade reaction sequences.
However, up to now, the acid sites in the acid-base bifunational
catalyst are mostly provided by acidic organic compounds in the
acid-base cascade reactions. One drawback of these materials is
that the strength of acid is relatively weak with the certain alkalinity,
i.e. the interaction of acid-base pairs is not perfectly matched, on
economy. Therefore, the subject of cascade reaction has received
considerable attention and elicited wide spread interest in the field
3
-5
of chemical synthesis. For efficiently catalyzing a cascade reaction,
the key is designing suitably multifunctional catalysts (in particular,
the heterogeneous catalyst) that should contain at least two types
of active sites. High yield of the target products synthesized by
multiple synthesis steps can be prepared in one pot under a suitable
6
-18
multifunctional catalyst.
Some multifunctional groups have been
successfully incorporated into heterogeneous catalysts through
direct co-condensation and/or post grafting procedure. However,
the acid-base bifunctional catalyst is less reported because of
mutual destruction of active sites in the one-pot synthetic process.
In order to overcome the neutralization effect of incompatible
groups, a good idea is that the antagonist functions should be
4
4, 45
one catalyst.
Therefore, it is always a challenge that how to tune
the interaction and ensure the spatial isolation of acid-base pairs for
developing a highly active catalyst in the acid-base cascade
reactions.
The diffusion blockage and direction of mass transportation in
catalysts is another important factor to effect the catalytic
performances of a heterogeneous catalyst. The hollow void within
the mesoporous materials could dramatically shorted the pore
channels, thus the diffusion blockage become less significant and
the active sites in the inner surface of the mesoporous can be
1
9
spatially isolated to coexist on one catalyst. There are several ways
2
0-33
to achieve these.
As yolk-shell formation is successfully
3
4
fabricated, the issue of the acid-base mutual neutralization is
3
5, 46-49
utilized more effectively.
Meanwhile, multiple shelled
a.
MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion
mesoporous materials make it easier that the different active sites
can be located in the catalyst and the reactants can be dispersed
evenly and fast to each other.
and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of
Technology, Harbin, China. Email: jiangyanqiu@hit.edu.cn (Y. Jiang) and
xuxianzhu@hit.edu.cn (X. Xu).
Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education),
Nankai University, Tianjin 300071, China
b.
Herein, a double-shelled hollow mesoporous silica nanosphere
1
C. You and C. Yu contributed equally to this work.
Electronic Supplementary Information (ESI) available: Fig. S1-S5.
This journal is © The Royal Society of Chemistry 20xx
(
HMS-Al@MS-NH
2
) as acid-base bifunctional catalyst with an acidic
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 2 of 8
View Article Online
DOI: 10.1039/C7NJ04670G
ARTICLE
NJC
inner shell (-Al) and a basic outer shell (-NH
2
) was fabricated. By
using the sol-gel chemistry, thus, the shells formed step-by-step, the
different active sites can be spatially isolated and the
functionalization of different shells of the catalyst can be accurately
controlled. The combination of hollow architecture and mesoporous
structure successfully offered a shortened diffusion pathway for the
reactants and products. The catalytic efficiency of the double-
shelled hollow mesoporous nanosphere for catalyzing
deacetalization-Knoevenagel and deacetalization-Henry cascade
reactions was demonstrated.
Scheme 1 Scheme for the preparation of double-shelled mesoporous HMS-
Experimental Section
2
Al@MS-NH .
Materials
deionized water and 50 mL of ethanol, then 4 mL deionized water
2
with 0.063g HMS-Al (ultrasonic treatment) and 8.5 mL NH ·H O
No further purification of chemicals before experiments.
3
Preparation of polystyrene (PS) template
were added into the mixture at room temperature. Then, 100 μL of
TEOS and 21 μL of aminopropyltriethoxysilane (APTES) were added
to react for 24 h. The mixture was centrifuged, washed with
deionized water and ethanol solution, dried in oven at 60 °C. To
remove the surfactant CTAB, the obtained samples were refluxed
with 4 mL of concentrated HCl aqueous solution and 60 mL of
ethanol solution at 80 °C for 24 h. Finally, a double-shelled HMS-
Based on the emulsion polymerization method, the synthetic
procedure of polystyrene template was illustrated as follows. Under
N
2
atmosphere, 1.5 g of polyvinyl pyrrolidone (PVP) was dissolved in
72 mL of deionized water in a three-necked flask. Then, 8 g of
styrene (extracted by 10% NaOH solution for three times) was
added slowly to the above solution, and the mixture was stirred at
the speed of 170 rpm to obtain a uniformly distributed solution. For
polymerization, 8 mL of deionized water with 0.26 g of 2,2-
azobisisobutyronitrile (AIBN) was added into the mixture, and then
the reaction was proceeded for 24 h in oil bath at 70 °C. After being
kept statically, the suspension was centrifuged, and the white
polystyrene was washed with deionized water for twice and dried in
oven at 60 °C. Then, the polystyrene microspheres were dispersed
in 15 mL of deionized water with ultrasonic to get a uniformly
distributed suspension. Finally, PS template was obtained.
Al@MS-NH
2
catalyst was obtained (Scheme 1).
The final product was designated as HMS-Al@MS-NH
2
-x, where x
refers to the molar ratio of Si to Al in the original mixture. For a
control experiment, mono-functional catalyst with comparable
concentration of amino groups and the same double-shelled
2
structure (HMS@MS-NH ) was prepared by similar methods.
Catalytic tests
The deacetalization-Knoevenagel reaction of all substrates was
carried out in a glass flask under magnetic stirring. In a typical run, 3
Preparation of single-shelled HMS-Al
2
mL of methylbenzene and 40 mg of HMS-Al@MS-NH were stirred
in the flask for 5 min. Then, 0.5 mmol of benzaldehyde dimethyl
acetal, 1 mmol of ethyl cyanoacetate, 0.1 mL of ethylbenzene and
In a typical run, 18 mL of deionized water and 50 mL of ethanol with
2
g of cetyltrimethyl ammonium bromide (CTAB), 2 mL of
0
.05 mL of deionized water were added and the reaction proceeded
polystyrene suspension, and 8.5 mL of NH ·H O were stirred
3
2
o
at 110 C for a certain time. The yield of benzyl cyanide ethyl
acetate (target product) was evaluated as the activity of reaction.
Using a gas chromatograph (GC Agilent-7890A) equipped with an
FID analysed reaction products. Ethylbenzene was used as the
internal standard.
together at room temperature for 15 min. Then, 0.0731 g of
aluminum isopropoxide solution (AIP, dissolved in 4 mL ethanol) was
added and 2 mL of tetraethyl orthosilicate (TEOS) was slowly added
into above solution. The mixture was reacted for 24 h. then the
solution was centrifuged, washed and dried at 60 °C. After all,
PS@Al-SiO was calcined for 8 h at 550 °C to obtain a single-shelled
2
Characterizations
hollow mesoporous silica nanosphere containing aluminium (HMS-
Al).
X-ray diffraction (XRD) was measured on a Bruker D8 Advance
instrument using Cu Kα radiation (wavelength λ = 0.15418) in the
According to the above-mentioned preparation procedure, a
single-shelled HMS-Al with tunable molar ratios of silicon to
aluminium at 100: 1, 25: 1 and 10: 1 can be obtained by altering the
using amount of AIP. For a comparison, hollow mesoporous silica
nanosphere without containing aluminium has been prepared via
the similar method.
o
o
range of 5-8 (2θ) at a rate of 0.01 /min. Content of nitrogen was
measured by elemental analysis on an Elementar Vario MICRO cube
system. The isotherms of nitrogen adsorption-desorption was
obtained by a Micromeritics ASAP 2020 system at liquid nitrogen
o
temperature. The samples were outgassed under 200 C for 240
o
min with a heating rate of 10 C/min before measurements. Molar
Preparation of double-shelled HMS-Al@MS-NH
The preparation route of double-shelled hollow mesoporous silica
nanosphere (HMS-Al@MS-NH ) was on the basis of single-shelled
HMS-Al. 2 g CTAB was dissolved into a mixed solution with 18 mL of
2
ratios of Si/Al were measured by elemental analysis on an Agilent
ICP-MS 7500c inductively coupled plasma mass spectrometer.
Scanning electron microscopy (SEM) images were taken on a Hitachi
S-4300 apparatus running at 0.5~30 kV. Transmission electron
2
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 3 of 8
View Article Online
DOI: 10.1039/C7NJ04670G
NJC
ARTICLE
microscopy (TEM) images were carried out on Hitachi H-7650
electron microscope running at 200 kV. Nuclear magnetic
29
resonance ( Si solid-state NMR) was conducted by Bruker AVANCE
III spectrometer operating to judge the coordination environment
of atoms and to analyse the content of elements. Gas
chromatograph (GC Agilent-7890A) equipped analysed reaction
products. X-ray photoelectron spectra (XPS) was used to
characterize the chemical state of elements in the as-prepared
samples with PHI 5700 ESCA system equipped with an A1 Kα
radiation as a source (hυ = 1486.6 eV). CO
ChemBET Pulsar TPD equipment (Quantachrome, USA) to analyse
the uptake of CO . The typical process as follows: 100 mg of HMS-
Al@MS-NH -25 sample was pretreated at 100 C for 20 min under
0 mL/min helium flow. After the temperature was decreased to 75
2
-TPD was measured with
2
o
2
3
o
C under helium flow, CO
2
sorption was started under 10 mL/min
o
CO flow for 30 min. Then the temperature was reduced to 30 C.
2
Finally, the desorption test was performed under 50 mL/min helium
o
flow through the temperature at a rate of 5 C/min from 30 to 150
o
o
C and kept 150 C for 30min. By calculating the amount of
desorbed CO from the calibrated desorption curve, then the
capacity of CO uptake or sorption in millimole of CO per gram of
2
2
2
2
7
sorbent (mmol/g-S) was obtained. AL MAS NMR spectrum was
analysed by Bruker-DRX-400 spectrometer.
Results and Discussion
Characteristics of the catalysts
Fig. 1 SEM images of (a) HMS-Al-25 and (b) HMS-Al@MS-NH
2
-25 and
SEM and TEM images were applied to determine the morphology
and structure of the synthesized samples. Clearly, the HMS-Al
spheres possessed uniform size (Fig. 1a, Fig. S1A and S1C) at ca.
TEM images of (c) HMS-Al-25 and (d), (e), (f) HMS-Al@MS-NH -25.
2
4
95-500 nm, which was regardless of ratios of Si/Al. It could be seen strongly related with the covered second shell formed after the
from the broken sample that it was indeed a hollow structure when condensation of TEOS and APTES. Notably, it was apparent from the
the polystyrene template was removed. When the second layer was high magnification TEM image (Fig. 1e) that HMS-Al@MS-NH -25
2
covered, the samples still possessed the spherical structure (Fig. 1b, was composed with two different shell layers (the red circle is the
Fig. S1B and S1D). Compared with the single-shelled ones, the boundary between two shells). In addition, both shells of HMS-
diameters of the double-shell samples were increased by ca. 30 nm, Al@MS-NH -25 contained abundant worm-like mesopores, which
2
which indicated that they were composed of double shells. was in good agreement with the XRD results (Fig. S2). Based on the
According to the view of the broken sample, the double-shelled preparation scheme, it was reasonable to consider that the acid Al
mesoporous spheres retained the hollow structure, showing that sites and basic amino sites were isolated and located in different
the condensation of TEOS and APTES only occurred on the outer shells.
shell of the HMS-Al sphere.
TEM images (Fig. 1c) indicated that the polystyrene template was HMS-Al@MS-NH
To get a more defined mesoporous architecture, a series of
-x with various ratios of silicon to aluminium
2
completely removed after calcination at high temperature. The were recorded by the nitrogen adsorption/ desorption
double-shelled structure was confirmed by comparing the shell measurement. All the samples were typical type-IV isotherms
5
Fig. 2A), pointing to the presence of mesoporous template
0
thickness of HMS-Al-25 and HMS-Al@MS-NH
2
-25, giving at 96 and
(
1
18 nm, respectively. Such increase for the shell thickness should be from CTAB micelles. Based on the pore size distribution curves,
2
Table 1 Texture properties of HMS-Al@MS-NH -x
Si/Al
S
BET
Pore vol.
(cm /g)
Pore size
(nm)
N content
(mmol/g)
catalyst
2
3
(
m /g)
(molar ratio)
HMS-Al@MS-NH
2
-10
1100
1302
1350
0.46
0.60
0.61
2.1
2.4
2.4
0.82
0.62
0.67
39
82
HMS-Al@MS-NH -25
2
HMS-Al@MS-NH
2
-100
477
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 4 of 8
View Article Online
DOI: 10.1039/C7NJ04670G
ARTICLE
NJC
Deacetalization-Knoevenagel reaction
With the co-existence of acid-base bifunctional active species, all of
the three materials were applied as catalyst in deacetalization-
Knoevenagel cascade reaction (Table 2). It was obvious that only
trace conversion could be monitored in blank and with pure SiO2
sphere. When the materials containing Al sites and amino groups in
the shells were applied as efficient catalysts, both of the conversion
and selectivity could be as high as ca. 100%. Besides, it could be
seen that only intermediate (B) was generated over HMS-Al and
trace yield of the product (C) was achieved. One can conclude that
the first step (deacetalization reaction) was mainly catalyzed by the
acid Al species and the second step (Knoevenagel reaction) by
amino groups. (entries 3, 5 and 6). It was worth nothing that the
conversion of A was 50.8% when the reaction was carried out in
absolute toluene, but it could be increased to almost 100% by
adding trace water in the reaction solution. This indicated that the
existence of water could accelerate the deacetalization process (as
displayed in entries 3 and 4) and had no influence on the
Knoevenagel reaction. Based on the observation that the materials
with molar ratio of Si/Al ranging from 10 to 100 all gave almost
1
00% conversion and selectivity when the reaction time was set as
long as 2 h, it was reasonable to believe that Al sites were highly
active for the deacetalization. For better understanding the
advantages of the structural design of HMS-Al@MS-NH sample, the
2
catalytic performance of the physical mixture composed of HMS-Al
and HMS@MS-NH2 had also been checked. The activity on the
physical mixture of HMS-Al and HMS@MS-NH was relatively lower
2
than HMS-Al@MS-NH -25 (entries 9 and 11), which confirmed the
2
Fig. 2 (A) Nitrogen adsorption-desorption isotherm and (B) BJH pore
advantages of the structural design of HMS-Al@MS-NH sample.
2
size distribution curves of (a) HMS-Al@MS-NH
NH -25 and (c) HMS-Al@MS-NH -100. For sake of clarity, spectra b
2
-10, (b) HMS-Al@MS-
For all the catalysts tested, the catalytic activity increased
2
2
3
gradually along with time, and HMS-Al@MS-NH -25 arrived a
and c are offset along the vertical axis by 50 and 150 cm /g,
respectively.
2
plateau emerged after 60 min. Note here that the yield of the final
product reached 100% during the reaction process. At the beginning
of the reaction time, a big difference in activity of HMS-Al@MS-NH2-
the mesopores were centered at 2.4 nm (Fig. 2B). It was clear 25, HMS-Al@MS-NH -100 and HMS-Al@MS-NH -10 was observed
2
2
that the molar ratio of Si/Al had no influence on the mesopore (Fig. 4A). HMS-Al@MS-NH -25 showed the higher reaction rate than
2
size. The other texture properties were listed in Table 1
2
.
H M S - A l @ M S - N H - 1 0 0 a n d H M S - A l @ M S - N H - 1 0 .
2
2
9
2
Si solid-state NMR spectrum of HMS-Al@MS-NH -25 was
performed to confirm that the ammonia propyl organosilane
was condensed into the hollow mesoporous framework (Fig.
3
2
). In addition to Q [Si(OR')
3
2
(OSi)
2 3
, -92 ppm], Q [Si(OR')(OSi) ,
4
100 ppm] and Q [Si(OSi)
-
4
, -110 ppm] signals, two types of
silicon species (-56 ppm and -67 ppm) were observed, which
2
2 2 3 3
corresponded to T [RSi(OSi) OH] (R represents-(CH ) -NH )
3
28
2
3
3
and T [RSi(OSi) ], respectively. The presence of T and T
signals confirmed that the organic groups and the silica surface
formed the strong covalent linkage. Meanwhile, XPS also
confirmed the presence of amino groups (402.7 eV) in the
5
1, 52
catalyst (Fig. S3).
2
The CO uptake was measured at 81.78
5
3, 54
mmol/g by the sorption (Fig. S5).
7
Al MAS NMR spectroscopy was applied for determining
2
the coordination of the acidic Al sites in the double-shelled
mesoporous silicas. The peak of 55 ppm and 0 ppm
corresponded to tetrahedral (AlO
4 6
) and octahedral (AlO )
55
coordination, respectively Fig. S4). Such NMR result
(
indicated that the Al sites in HMS-Al@MS-NH
tetrahedral.
2
-25 were mainly
29
Fig. 3 Si solid-state NMR spectrum of HMS-Al@MS-NH
2
-25 (T : -56
2
3
ppm; T : -67 ppm; Q : -92 ppm; Q : -100 ppm; Q : -110 ppm).
2
3
4
4
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 5 of 8
View Article Online
DOI: 10.1039/C7NJ04670G
NJC
ARTICLE
Table 2 Deacetalization-Knoevenagel cascade reaction sequence catalysed by different catalysts
Entry
Catalyst
Conv. of A (%)
Yield of B (%)
Yield of C (%)
Sel. of C (%)
a
1
2
No catalyst
1.3
2.7
1.3
2.7
0
0
0
0
a
Pure SiO2
a
3
4
5
6
7
8
9
HMS-Al
50.8
~100
12
50.8
~100
0
0
0
b
HMS-Al
0
0
a
HMS@MS-NH
HMS-Al@MS-NH
HMS-Al@MS-NH -25
2
12
~100
78
a
2
-25
76
16.7
41.6
0
59.3
58.4
97.6
~100
~100
85.7
b
~100
97.6
~100
~100
~100
58.4
~100
~100
~100
85.7
2
c
c
HMS-Al@MS-NH
HMS-Al@MS-NH
2
2
-10
-25
0
c
1
1
0
1
HMS-Al@MS-NH
2
-100
0
c
HMS-Al and HMS@MS-NH2
14.3
a
Reaction conditions: benzaldehyde dimethyl acetal (0.5 mmol), ethyl cyanoacetate (1.0 mmol), toluene (3 mL), catalyst (40 mg), reaction temperature is
o
b
c
1
2 2
10 C，reaction time is 20 min. Conversion and yield were determined by GC analysis using hexane as internal standard. 50 μL H O. 50 μL H O,
Reaction time is 2 h.
2
By considering that octahedral Al sites in a porous silica possessed active acidic and basic sites leached from HMS-Al@MS-NH -25
weaker acid strength than tetrahedral ones, the relatively lower during the reaction process under the given reaction conditions (Fig.
conversion of the benzaldehyde dimethyl acetal over HMS-Al@MS- 4B).
NH
2
-10 was possibly attributed to the different coordination
A catalyst is necessarily evaluated by recyclability which is an
environment (octahedral) compared with that (tetrahedra) in HMS- important parameter. The catalyst was recycled via calcination
o
Al@MS-NH
Leaching test was performed to evaluate if the active acidic and be regenerated. It was clear that catalytic activity was no significant
basic species leached in the reaction mixture during the catalysis loss when reusing HMS-Al@MS-NH -25 in four successive catalytic
procedure. HMS-Al@MS-NH -25 was separated from the reaction runs, indicating the high stability of the active sites. This is in good
mixture at 110 C after 20 min. The filtrate was divided into two agreement with the result from leaching test (Fig. 5).
2
-25 and HMS-Al@MS-NH
2
-100.
2
under N for 2 h at 200 C after each run and the active sites could
2
2
o
o
sections: one was further heated for 100 min at 110 C and the
2
The assets of HMS-Al@MS-NH -x are constituted by its
other was analyzed by GC. Notably, no further reaction was mesoporosity and isolate acidic and basic sites located in different
observed after the catalyst had been removed, indicating that no shells, which enable the cascade reaction. To show that this effect
Fig. 4 (A) Conversions of the deacetalization-Knoevenagel of benzaldehyde dimethyl acetal with (a) HMS-Al@MS-NH
00 and (c) HMS-Al@MS-NH -10 versus reaction time; (B) leaching test for HMS-Al@MS-NH -25 during the reaction: (a) yields of product with
HMS-Al@MS-NH -25 and (b) yields of product after the catalyst of HMS-Al@MS-NH -25 was filtered from the reaction media after 20 min.
2 2
-25, (b) HMS-Al@MS-NH -
1
2
2
2
2
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 6 of 8
View Article Online
DOI: 10.1039/C7NJ04670G
ARTICLE
NJC
Table 3 Deacetalization-Henry reaction catalyzed by different catalysts.
Yield of D
%)
Entry
Catalyst
Conv. of A (%) Yield of B (%)
Sel. of D (%)
(
a
a
1
2
3
4
HMS-Al@MS-NH
HMS-Al@MS-NH
2
2
-10
-25
98
0.3
0
97.7
~100
79.1
>99
99.6
~100
99.4
This work
This work
This work
~100
79.6
100
a
HMS-Al@MS-NH
2
-100
0.5
b
28
YS-NH
2
@SOH
3
trace
－
Ref.
a
o
Reaction conditions: benzaldehyde dimethyl acetal (0.5 mmol), nitromethane (5 mL), catalyst (40 mg), reaction temperature is 90 C,
reaction time is 14 h.
b
o
Reaction conditions: benzaldehyde dimethyl acetal (0.5 mmol), nitromethane (5 mL), catalyst (100 mg), reaction temperature is 90 C,
reaction time is 22 h.
Fig. 6 Schematic reaction flow of the two-step cascade reaction sequences
2
on the double–shelled structured bifunctional catalyst HMS-Al@MS-NH .
2
Fig. 5 Catalytic activity with repeated use of HMS-Al@MS-NH -25 in the
deacetalization-Knoevenagel of benzaldehyde dimethyl acetal via
calcination approach.
In summary, double-shelled hollow mesoporous silicas have been
designed via a two-step condensation approach, by which acidic
was not limited to the deacetalization-Knoevenagel reaction, HMS- frame worked Al species were incorporated in the inner shell and
Al@MS-NH -x was tested for the other cascade reaction, i.e. one- amino groups were tethered on the outer shell. The double-shelled
2
pot deacetalization-Henry reaction and HMS-Al@MS-NH -x proved construction realized spatial separation of acidic and basic sites and
2
to exhibit good performances (Table 3). The conversion and the mesopores in the shells favored the mass transfer in and out of
selectivity of the double-shelled catalysts of HMS-Al@MS-NH -10 the hollow interior. Such double-shelled hollow materials proved to
2
and HMS-Al@MS-NH -25 in the deacetalization-Henry cascade be highly active and selective for the deacetalization-Knoevenagel
2
reaction were very promising when compared with the catalytic cascade reaction, giving ca. 100% conversion of benzaldehyde
performance obtained with other acid-base bifunctional yolk-shell dimethyl acetal and ca. 100% selectivity towards the target product
nanoreactor of YS-NH @SOH , even though more catalyst was used of ethyl benzyl cyanoacetate. Importantly, HMS-Al@MS-NH -25 was
2
3
2
and longer reaction time was set in the case of YS-NH @SOH (see a stable catalyst without leaching of active sites and could be
2
3
2
8
reaction conditions in Table 3).
successfully reused in catalytic cycles without obvious loss of activity.
As shown in Fig. 6, the reactants (benzaldehyde dimethyl acetal) Moreover, the double-shelled hollow materials with mesopores
could pass through the hollow space to reach the inner shell during were also active and selective for the deacetalization-Henry cascade
the catalytic process, where they were converted into the reaction.
intermediate species (benzaldehyde) via the reaction of
deacetalization. In the outer shell, the intermediate (B) diffused
Conflicts of interest
from the inner shell could be further catalyzed to the target product
6
(ethyl benzyl cyanoacetate).
There are no conflicts to declare.
Conclusions
6
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
New Journal of Chemistry
Page 7 of 8
View Article Online
DOI: 10.1039/C7NJ04670G
NJC
ARTICLE
2
2
7. B. Helms, S. J. Guillaudeu, Y. Xie, M. McMurdo, C. J. Hawker and
J. M. Fréchet, Angew. Chem. Int. Ed., 2005, 44, 6384-6387.
8. Y. Yang, X. Liu, X. Li, J. Zhao, S. Bai, J. Liu and Q. Yang, Angew.
Chem. Int. Ed., 2012, 124, 9298-9302.
Acknowledgements
We thank the financial support from National Natural Science
Foundation of China (51472062) and the Opening Project of Key
Laboratory of Polyoxometalate Science of Ministry of Education.
29. M. Sasidharan, S. Fujita, M. Ohashi, Y. Goto, K. Nakashima and
S. Inagaki, Chem. Commun., 2011, 47, 10422-10424.
3
3
3
3
3
3
3
0. N. R. Shiju, A. H. Alberts, S. Khalid, D. R. Brown and G.
Rothenberg, Angew. Chem. Int. Ed., 2011, 123, 9789-9793.
1. Y. Huang, S. Xu and V. S. Y. Lin, Angew. Chem. Int. Ed., 2011, 50,
Notes and references
1
.
M. J. Nasab and A. R. Kiasat, Micropor. Mesopor. Mat., 2016,
23, 10-17.
L. C. Lee, J. Lu, M. Weck and C. W. Jones, ACS Catal., 2016, 6,
84-787.
6
61-664.
2
2. K. Motokura, N. Fujita, K. Mori, T. Mizugaki, K. Ebitani and K.
Kaneda, J. Am. Chem. Soc., 2005, 127, 9674-9675.
3. R. Abu-Reziq, D. Wang, M. Post and H. Alper, Chem. Mater.,
2.
7
3
4
.
.
X. Du and J. He, Nanoscale, 2011, 3, 3984-4002.
Y. Chen, H. R. Chen and J. L. Shi, Accounts Chem. Res., 2013, 47,
2
008, 20, 2544-2550.
4. H. Liu, T. Liu, M. Takafuji, H. Qiu and H. Ihara, New J. Chem.,
017, 41, 11517-11520.
5. X. W. D. Lou, L. A. Archer and Z. Yang, Adv. Mater., 2008, 20,
987-4019.
1
25-137.
J. Dou and H. C. Zeng, J. Am. Chem. Soc., 2012, 134, 16235-
6246.
P. Li, C. Y. Cao, Z. Chen, H. Liu, Y. Yu and W. G. Song, Chem.
Commun., 2012, 48, 10541-10543.
2
5.
6.
7.
8.
9.
1
1
3
6. J. Liu, S. Z. Qiao, J. S. Chen, X. W. D. Lou, X. Xing and G. Q. M. Lu,
Chem. Commun., 2011, 47, 12578-12591.
7. J. Liu, S. Z. Qiao and Q. H. Hu, Small, 2011, 7, 425-443.
8. R. Ghosh Chaudhuri and S. Paria, Chem. Rev., 2011, 112, 2373-
K. Motokura, M. Tada and Y. Iwasawa, J. Am. Chem. Soc., 2007,
3
3
129, 9540-9541.
S. Shylesh, A. Wagner, A. Seifert, S. Ernst and W. R. Thiel, Chem-
Eur. J., 2009, 15, 7052-7062.
A. El Kadib, K. Molvinger, M. Bousmina and D. Brunel, J. Catal.,
2
433.
3
4
4
9. F. Tang, L. Li and D. Chen, Adv. Mater., 2012, 24, 1504-1534.
0. F. Caruso, Adv. Mater., 2001, 13, 11-22.
1. Q. Sun, C. Z. Guo, G. H. Wang, W. C. Li, H. J. Bongard and A. H.
Lu, Chem-Eur. J., 2013, 19, 6217-6220.
2
010, 273, 147-155.
0. A. Corma, T. Ródenas and M. J. Sabater, Chem-Eur. J., 2010, 16,
54-260.
2
4
4
2. W. Chen, Z. Fan, X. Pan and X. Bao, J. Am. Chem. Soc., 2008,
11. S. Shylesh and W. R. Thiel, ChemCatChem, 2011, 3, 278-287.
12. D. Susam and C. Tanyeli, New J. Chem., 2017, 41, 3555-3561.
13. G. Guerrero, P. H. Mutin, E. Framery and A. Vioux, New J.
Chem., 2008, 32, 1519-1525.
1
30, 9414-9419.
3. L. M. Rossi, N. J. Costa, F. P. Silva and R. Wojcieszak, Green
Chem., 2014, 16, 2906-2933.
4. S. L. Hruby and B. H. Shanks, J. Catal., 2009, 263, 181-188.
5. S. Shylesh, A. Wagner, A. Seifert, S. Ernst and W. R. Thiel, Chem-
Eur. J., 2009, 15, 7052-7062.
4
4
1
1
1
1
1
4. S. Sobhani, F. Zarifi and J. Skibsted, New J. Chem., 2017, 41,
6
219-6225.
5. P. Li, H. Liu, Y. Yu, C. Y. Cao and W. G. Song, Chem-Asian J.,
013, 8, 2459-2465.
4
4
4
4
5
5
5
5
5
5
6. C. Zhao and J. A. Lercher, Angew. Chem. Int. Ed., 2012, 124,
2
6
037-6042.
6. P. Li, Y. Yu, P. P. Huang, H. Liu, C. Y. Cao and W. G. Song, J.
Mater. Chem. A, 2014, 2, 339-344.
7. P. Li, Y. Yu, H. Liu, C. Y. Cao and W. G. Song, Nanoscale, 2014, 6,
7. W. Cheng, Y. Jiang, X. Xu, Y. Wang, K. Lin and P. P. Pescarmona,
J. Catal., 2016, 333, 139-148.
8. Y. Li, Y. Jiang, Z. Ruan, K. Lin, Z. Yu, Z. Zheng, X. Xu and Y. Yuan, J.
Mater. Chem. A, 2017, 5, 21300-21312.
9. Y. He, P. Xu, B. Zhang, Y. Du, B. Song, X. Han and H. Peng, ACS
Appl. Mater. Inter., 2017, 9, 38401-38408.
0. R. Khatun, P. Bhanja, P. Mondal, A. Bhaumik, D. Das and S. M.
Islam, New J. Chem., 2017, 41, 12937-12946.
1. S. S. Park, S. W. Chu, C. Xue, D. Zhao and C. S. Ha, J. Mater.
Chem., 2011, 21, 10801-10807.
2. H. Zhao, X. Chen, C. Jia, T. Zhou, X. Qu, J. Jian, Y. Xu and T. Zhou,
Mater. Sci. Eng. B, 2005, 122, 90-93.
3. B. Yang, F. Zhou, S. Liu, P. Wang, A. S. Alshammari and Y. Deng,
Rsc Adv., 2015, 5, 48908-48915.
4. P. Wang, X. Ma, Q. Li, B. Yang, J. Shang and Y. Deng, Rsc Adv.,
4
42-448.
8. P. Li, C. Y. Cao, H. Liu, Y. Yu and W. G. Song, J. Mater. Chem. A,
013, 1, 12804-12810.
2
19. B. Voit, Angew. Chem. Int. Ed., 2006, 45, 4238-4240.
20. B. Cohen, M. Kraus and A. Patchornik, J. Am. Chem. Soc., 1981,
1
03, 7620-7629.
1. F. Gelman, J. Blum and D. Avnir, Angew. Chem. Int. Ed., 2001,
13, 3759-3761.
2. N. T. Phan, C. S. Gill, J. V. Nguyen, Z. J. Zhang and C. W. Jones,
Angew. Chem. Int. Ed., 2006, 45, 2209-2212.
3. S. Shylesh, A. Wagener, A. Seifert, S. Ernst and W. R. Thiel,
Angew. Chem. Int. Ed., 2010, 49, 184-187.
4. Y. Huang, B. G. Trewyn, H. T. Chen and V. S. Y. Lin, New J. Chem.,
2
2
2
2
2
2
1
2
016, 6, 54013-54019.
2008, 32, 1311-1313.
5. G. A. Rosales-Sosa, A. Masuno, Y. Higo, H. Inoue, Y. Yanaba, T.
Mizoguchi, T. Umada, K. Okamura, K. Kato and Y. Watanabe, Sci.
Rep., 2015, 5, 15233.
5. A. Takagaki, M. Ohara, S. Nishimura and K. Ebitani, Chem.
Commun., 2009, 6276-6278.
6. F. Gelman, J. Blum and D. Avnir, J. Am. Chem. Soc., 2000, 122,
11999-12000.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

New Journal of Chemistry
Page 8 of 8
View Article Online
DOI: 10.1039/C7NJ04670G
Graphical abstract
Table of content
Double-shelled hollow mesoporous silica nanosphere as acid-base bifunctional
catalyst for cascade reactions.