Amine-functionalized ionic liquid-based mesoporous organosilica as a highly efficient nanocatalyst for the Knoevenagel condensation

Article abstract of DOI:10.1039/c5cy01666e

A novel amine-functionalized ionic liquid-based periodic mesoporous organosilica (PMO-IL-NH₂) was prepared and characterized and its catalytic performance was investigated in the Knoevenagel reaction. PMO-IL-NH₂ was prepared by simul

Full text of DOI:10.1039/c5cy01666e

Catalysis
Science &
Technology
View Article Online
View Journal
PAPER
Amine-functionalized ionic liquid-based
mesoporous organosilica as a highly efficient
Cite this: DOI: 10.1039/c5cy01666e
nanocatalyst for the Knoevenagel condensation†
a
a
b
Dawood Elhamifar,* Somayeh Kazempoor and Babak Karimi
A novel amine-functionalized ionic liquid-based periodic mesoporous organosilica (PMO-IL-NH
pared and characterized and its catalytic performance was investigated in the Knoevenagel reaction. PMO-
IL-NH was prepared by simultaneous co-condensation of 3-aminopropyltrimethoxysilane, an ionic liquid
2
) was pre-
2
and tetramethoxysilane in the presence of a surfactant template under acidic conditions. The material was
characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, thermal gravimetric
analysis (TGA), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and transmission
2
electron microscopy (TEM). The catalytic application of PMO-IL-NH was then successfully carried out in
Received 2nd October 2015,
Accepted 26th January 2016
the Knoevenagel condensation of a variety of different aldehydes with ethyl cyanoacetate under solvent-
free conditions at room temperature, giving high to excellent yields of the corresponding products. The
catalyst was also recovered and reused several times without a significant decrease in either activity or
product selectivity. The TEM image and nitrogen sorption analysis of the recovered catalyst after the fifth
reaction cycle confirmed its high stability and durability under the applied reaction conditions.
DOI: 10.1039/c5cy01666e
www.rsc.org/catalysis
line, several heterogeneous catalysts based on resins, zeolites,
hydrotalcites, heteropolyacids, metal–organic frameworks and
Introduction
The Knoevenagel reaction is an important process for the for-
mation of carbon–carbon double bonds involving the one-pot
condensation of active methylenes with carbonyl compounds
organo-functionalized silicas have been introduced for cata-
lyzing the Knoevenagel condensation under heterogeneous
7
–15
conditions.
In this context, amine-functionalized ordered
1
,2
followed by a dehydration reaction. This has been widely
applied for the preparation of a wide range of substituted al-
kenes and biologically active compounds that are important
mesoporous silicas are more attractive due to their high sur-
face area, uniform pore structure, good recoverability and re-
usability as well as isolated catalytic-amine sites in their chan-
1
–3
14,15
in natural product synthesis. The Knoevenagel reaction has
traditionally been performed under homogeneous conditions
in the presence of either organic or inorganic base catalysts
such as pyridine, piperidine, pyrrolidine, morpholine, triethyl-
nels.
While these achievements have removed restrictions
related to catalyst recovery and product separation, however,
in most cases disadvantages such as high catalyst loading,
the use of volatile organic solvents and low yield of products
are still observed. Therefore, the preparation and develop-
ment of effective heterogeneous catalyst systems with high ef-
ficiency and low loading, while demonstrating excellent reus-
ability features, is still an important challenge in this area.
On the other hand, ordered mesoporous organosilicas
(OMOs) with uniform pore sizes larger than 2 nm, large pore
volumes, high surface areas and unique surface chemistry
1
,2,4
amine, KF, K CO , NaHCO , K HPO and so on.
Moreover,
, TiCl
, etc. have also been successfully
employed as catalysts for this important condensation reac-
2
3
3
2
4
many Lewis acids such as ZnCl
CuCl , Al , LaCl , NbCl
2
, LiCl, MgIJClO
)
4 2
4
,
2
O
2 3
3
5
5,6
tion.
However, the aforementioned systems have restric-
tions including catalyst recovery, product separation, environ-
mental pollution and high reaction temperatures. Therefore,
heterogenization of the corresponding catalysts has become a
play a significant role in the areas of adsorption, catalysis,
7–11
16–18
significant tool in order to solve these concerns.
Along this
gas storage, solid phase extraction and so forth.
Among
the different kinds of OMOs, periodic mesoporous
organosilicas (PMOs) built from bridged organosilane precur-
sors, [(RO) SiR′SiIJOR) ], have attracted tremendous attention
3 3
a
Department of Chemistry, Yasouj University, Yasouj, 75918-74831, Iran.
E-mail: d.elhamifar@yu.ac.ir
because they offer unique properties such as uniform distri-
bution and high loading of organic functional groups in the
framework as well as improved thermal and mechanical sta-
b
Department of Chemistry, Institute for Advanced Studies in Basic Sciences
(IASBS), Gava Zang, 45137-6731, Zanjan, Iran
†
Electronic supplementary information (ESI) available. See DOI: 10.1039/
1
9
c5cy01666e
bility. To date, many PMOs have been prepared using
This journal is © The Royal Society of Chemistry 2016
Catal. Sci. Technol.

View Article Online
Paper
Catalysis Science & Technology
different precursors based on alkyl, alkenyl, aryl and hetero-
aryl groups; however, many of the incorporated organic
functional groups are not suitable to be used for catalytic
1
9,20
applications.
A valuable achievement to overcome the
aforementioned problem is the creation of bifunctionalized
periodic mesoporous organosilicas (BPMOs) combining the
2
0,21
unique framework properties with specific active sites.
In the past few years, several BPMO materials have been pre-
pared and their catalytic applications have been successfully
2
0–22
carried out in some important chemical processes.
More
recently, we have also introduced a new class of supported
ionic liquid systems based on periodic mesoporous
organosilicas composed of an alkylimidazolium ionic liquid
23
framework (PMO-IL). This material has thus far been suc-
cessfully employed as an efficient support for immobilization
and stabilization of Pd nanoparticles in the Suzuki coupling
reaction, aerobic oxidation of alcohols and the Heck reaction,
for Ru catalysts in aerobic alcohol oxidation, for Au nano-
particles in the synthesis of propargylamines via the A3 cou-
pling reaction, as well as for immobilization of tungstate in
the oxidation of sulfides and alcohols. As part of our con-
tinuing investigation in this area, more recently we prepared
and characterized a novel sulfonic acid and ionic liquid-
based bifunctional periodic mesoporous organosilica (BPMO-
2
Scheme 1 Preparation of the PMO-IL-NH nanocatalyst.
2
3
diffraction (PXRD) pattern of the catalyst demonstrated typi-
cal d100 and d110 reflections in the low-angle diffraction re-
gion of 2θ < 2°, which can be assigned to the two-
dimensional hexagonal symmetry (P6mm) lattice (Fig. 1). The
presence of a d100 peak with high intensity excellently con-
firms the good structural regularity of the material.
IL-SO H) material and studied its catalytic application in the
3
2
2
esterification of carboxylic acids and Biginelli reaction. This
catalyst exhibited improved catalytic performance compared
to the corresponding simple supported sulfonic acids in the
described reactions, a feature that was attributed to the pres-
ence of imidazolium moieties in the framework of the mate-
rial. Moreover, the catalyst was recovered and reused several
times without a significant decrease in activity and selectivity.
In continuation of these studies, herein we wish to disclose
the synthesis and characterization of a novel propylamine-
functionalized periodic mesoporous organosilica with an
The TEM image also showed that PMO-IL-NH features a
2
highly ordered mesoporous structure, which is parallel to the
long axis of the uniform rods (Fig. 2). This observation is in
good agreement with the results of PXRD analysis and also
fits well with the two-dimensional hexagonal mesostructures.
Scanning electron microscopy (SEM) analysis was also
performed to study the morphology of the material (Fig. 3).
This image clearly showed the presence of uniform and
2
ionic liquid framework (PMO-IL-NH ) and studied its cata-
lytic application in the Knoevenagel condensation of alde-
hydes with ethyl cyanoacetate (Scheme 1).
Results and discussion
An amine-functionalized ionic liquid-based periodic meso-
porous organosilica (PMO-IL-NH ) was prepared by the simul-
2
taneous hydrolysis and condensation of tetramethoxysilane
(TMOS), 1,3-bisIJtrimethoxysilylpropyl)imidazolium chloride
and 3-aminopropyltrimethoxysilane in the presence of
Pluronic P123 under acidic conditions (Scheme 1). The PMO-
IL-NH nanomaterial was then characterized using several
2
techniques such as thermal gravimetric analysis (TGA), dif-
fuse reflectance infrared Fourier transform (DRIFT) spectro-
scopy, transmission electron microscopy (TEM), scanning
electron microscopy (SEM) and powder X-ray diffraction
(PXRD).
Transmission electron microscopy (TEM) and PXRD analy-
ses of PMO-IL-NH2 were performed to get insight into the
structural features of the material. The powder X-ray
Fig. 1 Powder X-ray diffraction (PXRD) pattern of the PMO-IL-NH2
nanocatalyst.
Catal. Sci. Technol.
This journal is © The Royal Society of Chemistry 2016

View Article Online
Catalysis Science & Technology
Paper
thermogravimetric (TG) and derivative thermogravimetric
(
DTG) diagrams exhibited a weight loss of about 4.6% at tem-
peratures below 100 °C corresponding to the removal of phys-
ically adsorbed water and alcoholic solvents. The second
weight loss of 2.75% at 100–270 °C corresponding to the
elimination of the Pluronic P123 surfactant residue which
remained after the surfactant extraction stage. The final and
main weight loss of 21.94% at 270–800 °C corresponding to
the decomposition and elimination of the ionic liquid and
propylamine functional groups from the material framework.
These data strongly verify the high thermal stability of the
material.
The PMO-IL-NH2 catalyst was next analyzed by DRIFT
spectroscopy in order to get detailed information about the
chemical functional moieties of the material (ESI† Fig. S1).
−
1
The absorption peaks at 700–800 cm are attributed to C–Si
stretching vibrations. The bands observed at 1095 and 930
2
Fig. 2 TEM image of the PMO-IL-NH nanocatalyst.
−
1
cm
are assigned to the symmetric and asymmetric
2
2,23
stretching vibrations of Si–O–Si bonds. The absorption
peaks at 1558 cm and 1622 cm can be assigned, respec-
tively, to CC and CN bonds of the imidazolium ring.
−
1
−1
2
2,23
The C–H deformation vibrations, C–H stretching vibrations
of propyl groups and unsaturated C–H stretching vibrations
−
1 22,23
are observed, respectively, at 1445, 2927 and 3105 cm .
−
1
In addition, the broad signals around 3300 cm are assigned
to N–H and O–H bonds. N–H bending vibration is also ob-
−
1
served at 689 cm . The stretching vibration band of C–N is
−
1
usually observed around 1000–1220 cm . However, this peak
cannot be resolved due to its overlap with the stretching
−
1
band of Si–O–Si in the range of 1000–1130 cm and that of
−
1 14b
Si–CH –R stretching in the range of 1200–1250 cm .
2
These data are in good agreement with those obtained in TG
analysis and strongly confirm the successful incorporation
and immobilization of organic groups (ionic liquid and
propylamine) in the material network.
2
Fig. 3 SEM image of the PMO-IL-NH nanocatalyst.
After characterization, the catalytic application of PMO-IL-
NH2 was studied in the Knoevenagel condensation of alde-
hydes with ethyl cyanoacetate under different conditions. In
the first step, the effect of solvent and catalyst loading was in-
vestigated (Table 1). At the beginning, all reactions were
performed at room temperature. The study showed that the
reaction was strongly affected by the amount of the catalyst.
As can be seen from the data summarized in Table 1, by in-
creasing the catalyst loading, the conversion was significantly
increased (entries 1–3) and the best result was obtained in
the presence of 0.5 mol% catalyst. The efficiency of the cata-
lyst was also considerably affected by the solvent. While
regular spherical particles with a diameter of 1 micrometer.
Thermal gravimetric analysis (TGA) was carried out to investi-
gate the thermal stability of the material (Fig. 4). The
3 2
EtOH, CH CN, toluene and H O resulted in low to moderate
yields of products at room temperature, an excellent yield
was obtained without employing a solvent under otherwise
the same reaction conditions (Table 1, entries 3–7). To show
the impact of amine functional groups on the catalytic pro-
cess, in the next step, the catalytic performance of amine-free
PMO-IL was also checked under the same reaction conditions
(Table 1, entry 3 vs. entry 8). This nanomaterial gave only a low
Fig. 4 TG and DTG diagrams of the PMO-IL-NH
2
nanocatalyst.
yield (<5%) of the desired product, indicating that the catalytic
This journal is © The Royal Society of Chemistry 2016
Catal. Sci. Technol.

View Article Online
Paper
Catalysis Science & Technology
Table 1 The effect of solvent and catalyst loading in the Knoevenagel condensation of ethyl cyanoacetate with benzaldehydea
b
Entry
Catalyst
Catalyst (mol%)
Solvent
Yield (%)
1
2
3
4
5
6
7
8
9
PMO-IL-NH
PMO-IL-NH
PMO-IL-NH
PMO-IL-NH
PMO-IL-NH
PMO-IL-NH
PMO-IL-NH
PMO-IL
2
2
2
2
2
2
2
0.12
0.25
0.5
0.5
0.5
0.5
c0.5
—
—
—
H O
2
EtOH
CH CN
18
48
96
40
37
35
18
<5
37
33
3
Toluene
—
—
—
SBA-15-Pr-NH
SiO -Pr-NH
2
0.5
0.5
10
2
2
a
b
c
Reaction conditions: benzaldehyde (1 mmol), ethyl cyanoacetate (1 mmol), r.t., 90 min. Isolated yields. The amount of PMO-IL (mg) was
2
the same as that used for PMO-IL-NH .
activity mainly originates from the amine functional groups.
The efficiency of the catalyst was also compared with those of
ionic liquid-free SBA-15-Pr-NH and SiO -Pr-NH materials un-
2 2 2
to proceed smoothly and the desired products were produced
in high to excellent yields without generation of any detect-
able side products. It is important to mention that according
to the NMR results (see the ESI†), only one peak for the al-
kene proton was observed at a chemical shift of about 8.3
ppm (singlet, 1 H, CC–H). This is in good agreement with
der essentially identical reaction conditions (Table 1, entry 3 vs.
entries 9 and 10). Interestingly, the results showed that both cat-
alysts had inferior activity as compared with that observed over
PMO-IL-NH comprising the same –NH loading. These observa-
5
b,24
previous studies
and corresponds to the alkene group of
2
2
tions strongly confirm the concomitant key role of ionic liquid
moieties in the catalytic process. The effect of ILs may be attrib-
uted to their lipophilicity leading to better diffusion of sub-
strates into mesochannels during the reaction. Another advanta-
geous role of ILs is attributed to the effect of the acidic
hydrogen of the imidazolium ring (–NCHN–) on the activation
of aldehydes during the catalytic process.
With the optimized conditions in hand, the scope and
limitations of this novel nanocatalyst were next investigated
in the Knoevenagel condensation of various aldehydes with
ethyl cyanoacetate (Table 2). Notably, all reactions were found
E-products that are more stable isomers successfully
confirming the high product selectivity of the catalyst. As
presented in Table 2, benzaldehyde was successfully reacted
with ethyl cyanoacetate in the presence of 0.5 mol% catalyst
to furnish the corresponding coupling product in excellent
yield (Table 2, entry 1). Moreover, this novel catalytic system
was equally effective with aromatic aldehydes bearing either
electron-withdrawing or electron-donating groups and
furnished the Knoevenagel products in good to excellent
yields (Table 2, entries 2–11). It is important to note that
even ortho-substituted benzaldehydes, which are known to
Table 2 The Knoevenagel condensation of aldehydes with ethyl cyanoacetate in the presence of the PMO-IL-NH
2
nanocatalysta
b
Entry
Aldehyde
Time (min)
Yield (%) [TON]
M. p.
1
2
3
4
5
6
7
8
9
PhCHO
90
120
110
100
110
90
96 [192]
90 [180]
93 [186]
95 [190]
93 [186]
95 [190]
97 [194]
88 [176]
93 [186]
93 [186]
88 [176]
50–51
52–54
160–161
89–90
105
160–162
173–174
65–66
95–96
80–83
2-Cl-PhCHO
3-Cl-PhCHO
4-Cl-PhCHO
3-Br-PhCHO
3-NO
4-NO
2
-PhCHO
-PhCHO
2
90
2-Me-PhCHO
4-Me-PhCHO
4-MeO-PhCHO
3-EtO, 4-OH-PhCHO
120
110
110
130
1
1
0
1
134–136
a
b
Reaction conditions: aldehyde (1 mmol), ethyl cyanoacetate (1 mmol), catalyst (0.5 mol%), r.t. Isolated yields.
Catal. Sci. Technol.
This journal is © The Royal Society of Chemistry 2016

View Article Online
Catalysis Science & Technology
Paper
show lower reactivity in organic transformations due to their
steric hindrance, also afforded the respective coupling prod-
ucts in high yield at room temperature (Table 2, entries 2
and 8). These observations strongly confirm the outstanding
capability of the PMO-IL-NH2 nanocatalyst in catalyzing the
Knoevenagel condensation of a broad range of aldehydes
with active methylene substrates. The advantages of this cata-
lyst may be attributed to the ionic liquid moieties and iso-
lated aminopropyl sites incorporated in the material frame-
work as well as the high surface area of the ordered
nanostructured PMO-IL material.
The recoverability and reusability of the catalyst were also
investigated in the reaction of benzaldehyde with ethyl cyano-
acetate under standard reaction conditions (Fig. 5). To do
this, after the reaction was completed, the obtained mixture
was filtered and the catalyst was washed thoroughly with eth-
anol and dried under vacuum at 70 °C. It was then used in
the aforementioned reaction under the same conditions as
before. Interestingly, the results illustrated that the catalyst
could be recovered and reused at least 8 times proving its
good durability and recoverability under the applied condi-
tions. It is important to note that the yield and turnover
number (TON) decreased by 14 and 28%, respectively, for the
regenerated catalyst after 9 cycles (ESI† Table S1). The lower
efficiency observed for the recovered mesoporous catalyst can
be primarily due to the partial saturation of mesochannels
containing catalytic active sites during the reaction process.
Nitrogen adsorption–desorption analysis of the recovered
PMO-IL-NH
NH ) showed an isotherm with a typical type IV shape and a
distinctive H1-type hysteresis loop at a relative pressure
about P/P = 0.5–0.72, which is commonly observed for mate-
2
catalyst after the fifth reaction cycle (RPMO-IL-
2
0
Fig. 6 Nitrogen adsorption–desorption (a) and pore size distribution
rials with ordered mesoporous structures (Fig. 6a). It is also
important to note that the BET surface area and pore volume
(b) isotherms of the recovered PMO-IL-NH
cycle.
2
after the fifth reaction
2
−1
of the fresh catalyst decreased from 596 m
g
and 1.12
3
−1
2
−1
3
−1
cm g to 438 m g and 0.90 cm g , respectively, for the
recovered catalyst. The BJH calculations also illustrated the
presence of a sharp peak with uniform pore size distribution
indicating that the recovered catalyst has very regular meso-
channels (Fig. 6b and ESI† Table S2). The highly ordered hex-
agonally symmetric structure of the recovered aminopropyl-
containing PMO-IL was also fully confirmed by the TEM im-
age (Fig. 7 and ESI† Fig. S2). These data are in agreement
with each other and strongly confirm the excellent mechani-
cal and structural stability of the desired catalyst under the
applied conditions.
2
and a mean pore diameter of 7.1 nm for RPMO-IL-NH ,
In another study, a filtration test was performed in order
to investigate whether the catalyst operates in a homoge-
neous or heterogeneous manner. For this reason, the reac-
tion of benzaldehyde with ethyl cyanoacetate was selected as
a model reaction. After 45 minutes, before complete con-
sumption of all substrates, warm EtOH was added into the
reaction flask and the obtained mixture was filtered. It was
found that a 40% conversion was attained at this stage. The
excess EtOH was then removed under reduced pressure from
the filtrate and the reaction was allowed to continue at room
temperature for another 3 h. In this regard, no considerable
reaction progress was observed, indicating that no leaching
Fig.
5
Reusability of the PMO-IL-NH
2
nanocatalyst in the
Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate.
This journal is © The Royal Society of Chemistry 2016
Catal. Sci. Technol.

View Article Online
Paper
Catalysis Science & Technology
Experimental section
Preparation of the PMO-IL-NH
The preparation of aminopropyl-containing ionic liquid-
based PMO (PMO-IL-NH ) was achieved by the simultaneous
hydrolysis and co-condensation of tetramethoxysilane
TMOS), 1,3-bisIJtrimethoxysilylpropyl)imidazolium chloride
and 3-aminopropyltrimethoxysilane in the presence of
2
nanocatalyst
2
(
2
2b
Pluronic P123 under acidic conditions.
In a typical proce-
dure, Pluronic P123 (2 g) was added to a solution containing
deionised water (11.7 g), HCl (2 M, 50 g) and potassium chlo-
ride (12.2 g) while stirring at 40 °C. After complete dissolu-
tion of the surfactant, a mixture of tetramethoxysilane (19
mmol), 1,3-bisIJtrimethoxysilylpropyl)imidazolium chloride
(
1.8 mmol) and 3-aminopropyltrimethoxysilane (1.5 mmol)
was added into the reaction vessel and stirred at the same
temperature for 24 h. The mixture was then heated at 100 °C
under static conditions for 72 h. After that, the obtained ma-
terial was filtered, washed with deionised water and dried at
room temperature. The removal of the surfactant was
achieved by means of a Soxhlet apparatus using ethanol for
Fig.
2
7 TEM image of the recovered PMO-IL-NH after the fifth
reaction cycle.
4
8 h. The final material was dried at 70 °C for 12 h and de-
of amine functional groups occurred during the reaction and
the catalyst most likely worked in a heterogeneous manner.
In the final study, the catalytic efficiency of the PMO-IL-
noted as PMO-IL-NH2.
General procedure for the Knoevenagel condensation
using the PMO-IL-NH
ethyl cyanoacetate (1 mmol) and the catalyst (0.5 mol%)
2
nanocatalyst. An aldehyde (1 mmol),
NH nanocatalyst was compared with those of a number of
2
2
6
previously reported amine-containing heterogeneous catalysts
in the Knoevenagel condensation (Table 3). The results
showed that the previously reported catalytic systems have
nice activity for the Knoevenagel condensation of a set of dif-
ferent carbonyl compounds with active methylenes; however,
in most cases the reaction was performed in organic solvents
at temperatures higher than that employed for the present
catalyst. Moreover, the recycling properties of the present
were added into a flask and stirred vigorously at room tem-
perature. The progress of the reaction was monitored via
TLC. After completion of the reaction, 5 mL of warm ethanol
was added to the reaction vessel and the obtained mixture
was filtered and completely washed with ethanol. Pure prod-
ucts were obtained after recrystallization in a mixture of hex-
ane/ethanol solvents; otherwise, the residue was isolated by
column chromatography on silica.
PMO-IL-NH nanocatalyst were shown to be more or less su-
2
General procedure for the recovery of the PMO-IL-NH2
nanocatalyst in the Knoevenagel reaction. For this purpose,
in a flask containing benzaldehyde (1 mmol) and ethyl cyano-
perior to those of most of the described catalytic systems.
These findings significantly confirm the high efficiency of
the present catalyst in the base-catalyzed Knoevenagel
reaction.
acetate (1 mmol), 0.5 mol% PMO-IL-NH catalyst was added
2
2
Table 3 Comparative study of the efficiency of the PMO-IL-NH nanocatalyst with that of previously reported catalytic systems in the Knoevenagel
a
condensation
Catalyst
Conditions
Recycling times
Ref.
b
CsNaX-NH
2
zeolite
Solvent-free, 180 min, 90 °C
—
8c
Am-IL-SBA-15
AP-MCM-41
AP-SBA-1
H
2
O, 1 h, RT
9
3
—
11c
13c
13c
Toluene, 2 h, RT
Toluene, 6 h, RT
b
ZrO
NH
SBA-15-Pr-NH
APS-MIL-101IJCr)
ED-MIL-101IJCr)
2
-Pr-NH
-MSNS
2
Solvent-free, RT, time (no reported)
3
8
—
—
3
14c
14f
2
2
H O, decane (100 : 1), 15 min, MW, 100 °C
b
2
Cyclohexane, 1 h, 82 °C
Cyclohexane, 80 °C, 19 h
Cyclohexane, 19 h, 80 °C
Toluene, 2 h, 60 °C
Toluene, 4 h, 40 °C
Solvent-free, 90 min, RT
25a
25b
25b
25c
25d
This work
b
b
NH
NH
2
-MIL-101IJCr)
-MIL-101IJAl)
—
b
2
Several times
8
PMO-IL-NH
2
a
2 2 3
Abbreviations: AM: aminopropyl; APS: aminopropyl silica; ZrO -Pr-NH : propylamine-functionalized mesoporous zirconia; MIL-101IJCr): [Cr IJF,
OH)IJH
2
O) OIJbdc) ]; ED: ethylenediamine; NH -MSNS: amine-functionalized mesoporous silica nanospheres; Am-IL-SBA-15: aminopropyl-ionic
2
3
2
b
liquid-SBA-15. The recycling times were not reported.
Catal. Sci. Technol.
This journal is © The Royal Society of Chemistry 2016

View Article Online
Catalysis Science & Technology
Paper
2
Scheme 2 Proposed mechanism for the Knoevenagel condensation using the PMO-IL-NH nanocatalyst.
and the mixture was magnetically stirred at room tempera-
ture. The reaction progress was monitored by TLC. After com-
pletion of the reaction, warm ethanol (5 mL) was added and
the obtained solution was filtered and washed with ethanol.
The recovered catalyst was then reused under the same con-
ditions as those in the first run at least 8 times and gave the
corresponding Knoevenagel product in high yield and
selectivity.
Although the exact reaction pathway for the present base-
catalyzed Knoevenagel condensation is not clear to us, a pro-
posed plausible mechanism for the reaction of different alde-
hydes with ethyl cyanoacetate is presented in Scheme 2. In
two-dimensional symmetry for the material. The IR and TG
analyses also confirmed the excellent stability of the incorpo-
rated ionic liquid and aminopropyl groups in the material
2
network. The PMO-IL-NH nanocatalyst was successfully ap-
plied to CC bond formation through the Knoevenagel reac-
tion of aldehydes with ethyl cyanoacetate and gave the corre-
sponding products in high to excellent yields and
selectivities. The catalyst was easily recovered and reused sev-
eral times without a significant decrease in efficiency. Some
other advantages of the present study are solvent-free media,
short reaction times, mild reaction conditions, high yield of
products as well as high activity, stability and durability of
the catalyst under the applied reaction conditions. Due to the
remarkable properties of this catalytic system, some of its ap-
plications in other chemical processes are under way in our
laboratories.
2
this context, the amine group of PMO-IL-NH is thought to
pick up one acidic proton from the active methylene group of
ethyl cyanoacetate to produce the corresponding enolate.
Then, the nucleophilic attack of this anion at the carbonyl
carbon followed by re-capture of the proton from the proton-
ated catalyst would result in the formation of the correspond-
ing β-hydroxyl compound and regenerated catalyst. Finally,
the Knoevenagel products can be obtained via the dehydra-
tion of β-hydroxyl compounds.
Acknowledgements
The authors thank Yasouj University and the Iran National
Science Foundation (INSF) for supporting this work.
Conclusions
Notes and references
In conclusion, a new amine-containing ionic liquid-based or-
1 (a) G. Jones, Org. React., 1967, 15, 204–599; (b) L. F. Tietze,
Chem. Rev., 1996, 96, 115–136; (c) Y. Ono, J. Catal.,
2003, 216, 406–415.
2 (a) D. S. Acker and W. R. Hertler, J. Am. Chem. Soc., 1962, 84,
3370–3374; (b) L. Rand, J. V. Swisher and C. J. Cronin,
J. Organomet. Chem., 1962, 27, 3505–3507; (c) S. Sebti, A.
dered mesoporous organosilica (PMO-IL-NH ) nanocatalyst
2
was prepared and characterized and its application was suc-
cessfully developed in the Knoevenagel condensation. The
PXRD analysis and TEM image of the PMO-IL-NH2 nano-
catalyst demonstrated a highly uniform mesostructure with
This journal is © The Royal Society of Chemistry 2016
Catal. Sci. Technol.

View Article Online
Paper
Catalysis Science & Technology
Smahi and A. Solhy, Tetrahedron Lett., 2002, 43, 1813–1815;
d) F. Santamarta, P. Verdia and E. Tojo, Catal. Commun.,
008, 9, 1779–1781.
(a) G. A. Kraus and M. E. Krolski, J. Organomet. Chem.,
Aguado, J. Canivet and D. Farrusseng, J. Mater. Chem.,
2011, 21, 7582–7588; (d) S. Aguado, J. Canivet, Y. Schuurman
and D. Farrusseng, J. Catal., 2011, 284, 207–214; (e)
F. X. Llabrés i Xamena, F. G. Cirujano and A. Corma,
Microporous Mesoporous Mater., 2012, 157, 112–117.
(
2
3
1
2
986, 51, 3347–3350; (b) L. F. Tietze, Pure Appl. Chem.,
004, 76, 1967–1983; (c) M. Zahouily, M. Salah, B.
11 (a) A. Ramani, B. M. Chanda, S. Velu and S. Sivasankar,
Green Chem., 1999, 163–165; (b) R. Xing, H. Wu, X. Li, Z.
Zhao, Y. Liu, L. Chen and P. Wu, J. Mater. Chem., 2009, 19,
4004–4011; (c) H. Zhao, N. Yu, Y. Ding, R. Tan, C. Liu, D.
Yin, H. Qiu and D. Yin, Microporous Mesoporous Mater.,
2010, 136, 10–17; (d) J. Mondal, A. Modak and A. Bhaumik,
J. Mol. Catal. A: Chem., 2011, 335, 236–241; (e) M. B.
Gawnde, R. K. Pandey and R. V. Jayaram, Catal. Sci. Technol.,
2012, 2, 1113–1125.
12 (a) P. Makowski, J. Weber, A. Thomas and F. Goettmann,
Catal. Commun., 2008, 10, 243–247; (b) Y. Peng, J. Wang, J.
Long and G. Liu, Catal. Commun., 2011, 15, 10–14; (c) W. Li,
J. Xiao and W. Q. Zhang, Green Chem., 2012, 14, 2234–2242;
(d) A. Modak, J. Mondal and A. Bhaumik, Appl. Catal., A,
2013, 459, 41–51.
13 (a) T. I. Reddy and R. S. Verma, Tetrahedron Lett., 1997, 38,
1721–1724; (b) J. Bennazha, M. Zahouilly, A. Boukhari and
E. A. Hol, J. Mol. Catal. A: Chem., 2003, 202, 247–252; (c) Y.
Kubota, Y. Nishizaki, H. Ikeya, M. Saeki, T. Hida, S. Kawazu,
M. Yoshida, H. Fujii and Y. Sugi, Microporous Mesoporous
Mater., 2004, 70, 135–149; (d) Y. Liu, J. Peng, S. Zhai, J. Li, J.
Mao, M. Li, H. Qiu and G. Lai, Eur. J. Inorg. Chem.,
2006, 2947–2949; (e) M. D. Gracia, M. J. Jurado, R. Luque,
J. M. Campelo, D. Luna, J. M. Marinas and A. A. Romero,
Microporous Mesoporous Mater., 2009, 118, 87–92.
14 (a) D. B. Jackson, Chem. Commun., 1997, 1781–1782; (b) F.
Shang, J. Sun, S. Wu, Y. Yang, Q. Kan and J. Guan,
Microporous Mesoporous Mater., 2010, 134, 44–50; (c) K. M.
Parida, S. Mallick, P. C. Sahoo and S. K. Rana, Appl. Catal.,
A, 2010, 381, 226–232; (d) R. Zhu, J. Shen, Y. Wei and F.
Zhang, New J. Chem., 2011, 35, 1861–1866; (e) T. Yokoi, Y.
Kubota and T. Tatsumi, Appl. Catal., A, 2012, 421–422,
14–37; ( f ) F. Zhu, X. Sun, F. Lou, L. An and P. Zhao, Catal.
Lett., 2015, 145, 1072–1079.
Bahlaouane, A. Rayadh, A. Houmam, E. A. Hamed and S.
Sebti, Tetrahedron, 2004, 60, 1631–1635; (d) S. M. Lai, C. P.
Ng, R. Martin-Aranda and K. L. Yeung, Microporous
Mesoporous Mater., 2003, 66, 239–252; (e) S. M. Lai, R. M.
Martín-Aranda and K. L. Yeung, Chem. Commun.,
2
003, 218–219.
4
5
G. Gowravaram, B. V. S. Reddy, R. S. Babu and J. S. Yadav,
Chem. Lett., 1998, 773–774.
(a) D. Prajapati, K. Lekhok, C. J. S. Sandhu and A. C. Ghosh,
J. Chem. Soc., Perkin Trans. 1, 1996, 959–960; (b) P. S. Rao
and R. V. Venkataratnam, Tetrahedron Lett., 1991, 32,
5
821–5822; (c) P. Leelavathi and S. Ramesh Kumar, J. Mol.
Catal. A: Chem., 2005, 240, 99–102; (d) L.-M. Wang, J. Sheng,
L. Zhang, J.-W. Han, Z.-Y. Fan and H. Tian, Chin. J. Org.
Chem., 2005, 25, 964–968; (e) G. Bartoli, M. Bosco, A.
Carlone, R. Dalpozzo, P. Galzerano, P. Melchiorre and L.
Sambri, Tetrahedron Lett., 2008, 49, 2555–2557; ( f ) B. Franca
and Q. Carla, Curr. Org. Synth., 2012, 9, 31–39.
6
7
(a) M. Gawande and R. Jayaram, Catal. Commun., 2006, 7,
9
31–935; (b) D. Fildes, D. Villemin, P.-A. Jaffres and V.
Caignaert, Green Chem., 2001, 3, 52–56.
(a) P. W. Lednor, Catal. Today, 1992, 15, 243–261; (b) S.
Tsunetake and O. Makoto, Catal. Surv. Asia, 2006, 10,
1
2
38–150; (c) J. M. Notestein and A. Katz, Chem. – Eur. J.,
006, 12, 3954–3965; (d) W. Chang and B. J. Ahn, Int. J.
Nanotechnol., 2006, 3, 181–193; (e) S. Thangaraj, M. Albert
and S. Wilhelm, Appl. Catal., A, 2012, 445, 92–101; ( f ) N.
Aider, N. A. Smuszkiewicz, E. Pérez-Mayoral, E. Soriano,
R. M. Martín-Aranda, D. Halliche and S. Menad, Catal.
Today, 2014, 227, 215–222.
8
9
(a) A. Corma and R. M. Martin-Aranda, Appl. Catal., A,
1
993, 105, 271–279; (b) A. Corma, V. Fornes, R. M. Martin-
Aranda, H. Garcia and J. Primo, Appl. Catal., 1990, 59,
37–248; (c) X. Zhang, E. S. M. Lai, R. M. Martín-Aranda and
2
15 (a) X. H. Lin, G. K. Chuah and S. Jaenicke, J. Mol. Catal. A:
Chem., 1999, 150, 287–294; (b) A. Wahab, I. Kim and C.-S. He,
J. Solid State Chem., 2004, 177, 3439–3447; (c) R. Srivastava,
J. Mol. Catal. A: Chem., 2007, 264, 146–152; (d) P. Han, H. M.
Zhang, X. P. Qiu, X. L. Ji and L. X. Gao, J. Mol. Catal. A:
Chem., 2008, 295, 57–67; (e) F. Domínguez-Fernández, J.
López-Sanz, E. Pérez-Mayoral, D. Bek, R. M. Martín-Aranda,
A. J. López-Peinado and J. Čejka, ChemCatChem, 2009, 1,
241–243; ( f ) L. Martins, W. Hőderich, P. Hammer and D.
Cardoso, J. Catal., 2010, 271, 220–227.
K. L. Yeung, Appl. Catal., A, 2004, 261, 109–118; (d) B.
Samiran, M. S. Jang and H. J. Kwon, Catal. Surv. Asia,
2
014, 18, 101–127.
(a) M. Hartmann and M. Fischer, Microporous Mesoporous
Mater., 2012, 164, 38–43; (b) A. Dhakshinamoorthy, M.
Opanasenko, J. Čejka and H. Garcia, Adv. Synth. Catal.,
2
013,
355,
247–268;
(c)
M.
Opanasenko,
A.
Dhakshinamoorthy, M. Shamzhy, P. Nachtigall, M. Horacek,
H. Garcia and J. Cejka, Catal. Sci. Technol., 2013, 3, 500–507;
(
d) M. Položij, M. Rubeš, J. Čejka and P. Nachtigall,
ChemCatChem, 2014, 6, 2821–2824; (e) A.
Dhakshinamoorthy, A. M. Asiri and H. Garica, Chim. Oggi,
015, 33, 40–45.
0 (a) Y. Tan, Z. Fu and J. Zhang, Inorg. Chem. Commun.,
011, 14, 1966–1970; (b) J. Canivet, S. Aguado, C. Daniel and
D. Farrusseng, ChemCatChem, 2011, 3, 675–678; (c) S.
16 (a) A. P. Wight and M. E. Davis, Chem. Rev., 2002, 102,
3589–3614; (b) A. Stein, Adv. Mater., 2003, 15, 763–775.
17 (a) K. K. Sharma and T. Asefa, Angew. Chem. Int. Ed.,
2007, 46, 2879–2882; (b) K. K. Sharma, R. P. Buckley and T.
Asefa, Langmuir, 2008, 24, 14306–14320; (c) K. K. Sharma, A.
Anan, R. P. Buckley, W. Ouellette and T. Asefa, J. Am. Chem.
Soc., 2008, 130, 218–228.
2
1
2
Catal. Sci. Technol.
This journal is © The Royal Society of Chemistry 2016

View Article Online
Catalysis Science & Technology
Paper
1
8 (a) A. Corma, Chem. Rev., 1997, 97, 2373–2419; (b) A. Sayari
and S. Hamoudi, Chem. Mater., 2001, 13, 3151–3168; (c) C.
Li, Catal. Rev.: Sci. Eng., 2004, 46, 419–492; (d) R. Corriu, A.
Mehdi and C. Reye, J. Organomet. Chem., 2004, 689,
Khorasani, H. Vali, J. H. Clark and A. J. Hunt, Chem. – Eur.
J., 2012, 18, 13520–13530; (d) B. Karimi, M. Gholinejad and
M. Khorasani, Chem. Commun., 2012, 48, 8961–8963; (e) D.
Elhamifar, B. Karimi, J. Rastegar and M. H. Banakar,
ChemCatChem, 2013, 5, 2218–2224; ( f ) D. Elhamifar and A.
Shábani, Chem. – Eur. J., 2014, 20, 3212–3217; (g) B. Karimi,
F. Bakhshandeh Rostami, M. Khorasani, D. Elhamifar and
H. Vali, Tetrahedron, 2014, 70, 6114–6119; (h) B. Karimi, F.
Bakhshandeh Rostami, M. Khorasani, D. Elhamifar and H.
Vali, ChemPlusChem, 2015, 80, 990–999.
4
437–4450.
1
9 (a) B. Hatton, K. Landskron, W. Whitnall, D. Perovic and
G. A. Ozin, Acc. Chem. Res., 2005, 58, 305–312; (b) F.
Hoffmann, M. Cornelius, J. Morell and M. Fröba, Angew.
Chem. Int. Ed., 2006, 45, 3216–3251; (c) S. Fujita and S.
Inagaki, Chem. Mater., 2008, 20, 891–908; (d) S. El Hankari,
B. Motos-Pérez, P. Hesemann, A. Bouhaouss and J. J. E.
Moreau, Chem. Commun., 2011, 47, 6704–6706.
24 (a) G. R. Krishnan, J. Thomas and K. Sreekumar, ARKIVOC,
2009, 106–120; (b) Y. An-guo, L. Luo, W. Guo-feng, C. Xin-
Zhi, Y. Wei-dong, C. Jian-hui and Z. Kai-yuan, Chem. Res.
Chin. Univ., 2009, 25, 876–881; (c) S. Mallouk, K. Bougrin, A.
Laghzizil and R. Benhida, Molecules, 2010, 15, 813–823; (d)
R. J. Kalbasi, M. Kolahdoozan, A. Massah and K. Shahabian,
Bull. Korean Chem. Soc., 2010, 31, 2618–2626; (e) S. M.
Ribeiro, A. C. Serra and A. M. d'A. R. Gonsalves, Appl. Catal.,
A, 2011, 399, 126–133; ( f ) F. Zamani and E. Izadi, Chin. J.
Catal., 2014, 35, 21–27.
2
2
0 (a) Q. Yang, J. Liu, L. Zhang and C. Li, J. Mater. Chem.,
2
009, 19, 1945–1955; (b) F. Hoffmann and M. Fröba, Chem.
Soc. Rev., 2011, 40, 608–620; (c) M. S. Moorthy, S.-S. Park, D.
Fuping, S.-H. Hong, M. Selvaraj and C.-S. Ha, J. Mater.
Chem., 2012, 22, 9100–9108; (d) U. Díaz, D. Brunel and A.
Corma, Chem. Soc. Rev., 2013, 42, 4083–4097.
1 (a) O. Olkhovyk, S. Pikus and M. Jaroniec, J. Mater. Chem.,
2
005, 15, 1517–1519; (b) J. Alauzun, A. Mehdi, C. Reyé and
R. J. P. Corriu, J. Mater. Chem., 2007, 17, 349–356; (c) L. Y.
Xia, M. Q. Zhang, M. Z. Rong and W. M. Xu, Phys. Chem.
Chem. Phys., 2010, 12, 10569–10576; (d) M. Sasidharan and
A. Bhaumik, ACS Appl. Mater. Interfaces, 2013, 5, 2618–2625.
2 (a) D. Elhamifar, B. Karimi, A. Moradi and J. Rastegar,
ChemPlusChem, 2014, 79, 1147–1152; (b) D. Elhamifar, M.
Nasr-Esfahani, B. Karimi, R. Moshkelgosha and A. Shábani,
ChemCatChem, 2014, 6, 2593–2599.
25 (a) X. Wang, K. S. K. Lin, J. C. C. Chan and S. Cheng, Chem.
Commun., 2004, 2762–2763; (b) Y. K. Hwang, D.-Y. Hong,
J.-S. Chang, S. H. Jhung, Y.-K. Seo, J. Kim, A. Vimont, M.
Daturi, C. Serre and G. Ferey, Angew. Chem., 2008, 120,
4212–4216 (Angew. Chem. Int. Ed., 2008, 47, 4144–4148); (c)
P. Kasinathan, Y.-K. Seo, K.-E. Shim, Y. K. Hwang, U.-H. Lee,
D. W. Hwang, D.-Y. Hong, S. B. Halligudi and J.-S. Chang,
Bull. Korean Chem. Soc., 2011, 32, 2073–2075; (d) P. Serra-
Crespo, E. V. Ramos-Fernandez, J. Gascon and F. Kapteijn,
Chem. Mater., 2011, 23, 2565–2572.
2
2
3 (a) B. Karimi, D. Elhamifar, J. H. Clark and A. J. Hunt, Chem.
–
Eur. J., 2010, 16, 8047–8053; (b) B. Karimi, D. Elhamifar,
J. H. Clark and A. J. Hunt, Org. Biomol. Chem., 2011, 9,
420–7426; (c) B. Karimi, D. Elhamifar, O. Yari, M.
26 S. van Dommele, K. P. de Jong and J. H. Bitter, Chem.
Commun., 2006, 4859–4861.
7
This journal is © The Royal Society of Chemistry 2016
Catal. Sci. Technol.