Synthesis and characterization of polymer/microporous molecular sieve nanocomposite as a shape-selective basic catalyst

Article abstract of DOI:10.1016/j.crci.2011.05.001

This paper reports the preparation and characterization of poly(4-vinylpyridine)/AlPO₄-11 nanocomposite and its application in Knoevenagel condensation as a novel basic catalyst. The catalyst was characterized by XRD, XRF, FT-IR, TGA, BET, SEM,

Full text of DOI:10.1016/j.crci.2011.05.001

C. R. Chimie 14 (2011) 1002–1013
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Full paper/Memoire
Synthesis and characterization of polymer/microporous molecular sieve
nanocomposite as a shape-selective basic catalyst
*
Roozbeh Javad Kalbasi , Elham Izadi
Department of Chemistry, Shahreza Branch, Islamic Azad University, 311-86145, Shahreza, Isfahan, Iran
A B S T R A C T
A R T I C L E I N F O
This paper reports the preparation and characterization of poly(4-vinylpyridine)/AlPO4-11
nanocomposite and its application in Knoevenagel condensation as a novel basic catalyst.
The catalyst was characterized by XRD, XRF, FT-IR, TGA, BET, SEM, and back titration using
NaOH and TPD techniques. Several AlPO4-11 with different Al/P ratios were prepared, and
the effect of the Al/P ratio on the surface properties and acidity of the support were
studied. The use of AlPO4-11 as a new supporting material for the Poly(4-vinylpyridine)
was tested for the Knoevenagel condensation. Excellent yields at room temperature in
aqueous and solvent-free conditions were obtained by this nanocomposite. Accordingly,
the catalyst showed shape selectivity in the Knoevenagel reaction. It was observed that the
activity of the catalyst just decreased to 90% after five regeneration processes were
performed.
Article history:
Received 22 February 2011
Accepted after revision 3 May 2011
Available online 24 June 2011
Keywords:
Heterogeneous catalysis
Organic-inorganic hybrids
Microporous materials
Polymers
´
ß 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
range of anionic open-frameworks with 3-dimensional (3-
D) framework, 2-D layer, 1-D chain, and 0-D cluster
Recently, heterogenization of homogeneous catalysts
has become an important strategy for the preparation of
supported catalysts, which have the combined advantages
of homogeneous and heterogeneous catalysts such as high
selectivity, reusability and ease of separation [1]. In
heterogeneous catalysts, various support matrices such
as organic polymers and inorganic silica, especially porous
inorganic materials with high surface areas, have been
employed [2,3]. Nowadays, design and preparation of
organic–inorganic hybrid catalysts based on molecular
sieves which are achieved by functionalizing the porous
system [4,5], are of great interest.
Aluminophosphate molecular sieves (AlPO4-n) are a
family of microporous crystalline materials developed in
1982 by Wilson et al. [6]. Amorphous aluminum phosphate
is built of tetrahedral units of AlO4 and PO4, and is
structurally similar to silica. They have many structures
including neutral zeolite-like open-frameworks, and a
structures [7,8]. In recent years, aluminum phosphate is
receiving considerable attention as a support for a variety
of catalytic reactions [9]. High surface area and controlla-
ble pore size distributions are the main reasons for using
amorphous AlPO4 as support. It is anticipated that the
AlPOs molecular sieve will have only weak catalytic and
sorption properties due to inherent lack of active sites,
which are necessary for catalysis. In general, the basicity in
calcined AlPO4 molecular sieve is achieved by functiona-
lizing its microporous, and surfaced with compounds
containing organic bases or basic polymers.
Micropore crystalline AlPO4-11 (AEL framework topol-
ogy) is a member of the aluminophosphate molecular
sieves family, which has a unique three-dimensional
˚
structure with orthorhombic symmetry, a = 13.534 A,
˚
˚
b = 18.482 A, c = 8.370 A, high thermal and hydrothermal
stability [10,11]. AlPO4-11 molecular sieve has 10-mem-
bered ring channels with elliptical pore apertures of
0.63 Â 0.39 nm [12,13].
Organic–inorganic polymer hybrid materials have
received a great deal of attention in recent years [14,15].
In the hybrid materials, the inorganic and organic phases
* Corresponding author.
E-mail address: rkalbasi@iaush.ac.ir (R.J. Kalbasi).
1631-0748/$ – see front matter ß 2011 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.crci.2011.05.001

R.J. Kalbasi, E. Izadi / C. R. Chimie 14 (2011) 1002–1013
1003
are combined by the interactions including hydrogen
bonds and chemical covalent bonds. The hybrids have
organic and inorganic elements that are mixed in a
molecular level, and the intimate mixing provides various
properties that are different from those of traditional
composites. The stability, low density, flexibility and low
manufacturing cost make these hybrid polymers amenable
for industrial applications [16].
Recently, scientists have synthesized a hybrid polymer/
aluminophosphate nanocomposite with layered alumino-
phosphates and different Al/P ratios [17,18]. These
materials are mostly used as gas or liquid separators,
not catalysts. There are many reports on the catalytic
activity of Lewis acid ion-exchanged AlPO4-11 for many
reactions of industrial importance [19]. However, there is
no literature report on synthesis, characterization and
application of polymer/AlPO4 nanocomposite as heteroge-
neous basic catalyst.
In our previous studies, Knoevenagel condensation over
heterogeneous basic catalyst using mesoporous materials
such as SBA-15 was carried out [14,20]. In the present
work, we wish to introduce a novel hybrid material,
poly(4-vinylpyridine) supported over micropore AlPO4-11
by in situ polymerization of 4-vinyl pyridine (4VP) in the
presence of AlPO4-11 (Scheme 1). The main goals of this
catalytic synthesis were to prepare a shape selective basic
catalyst and to compare this novel micropore nanocopm-
posite with other mesoporous composites prepared in the
previous studies [14,20].
copy (Nicolet 400D in KBr matrix in the range of 4000–400/
cm), SEM (Philips XL20) and thermal analyzer TGA
(Setaram Labsys TG [STA] in temperatures 30–700 8C
and heating rate of 10 8C/min in N2 atmosphere),
respectively. The specific surface area was calculated
using the Brunauer–Emmett–Teller (BET) method. N2-BET
surface areas and pore volumes were determined on a
series BEL SORP 18 apparatus, at 77 K. The nitrogen
adsorption isotherms of the AlPO4-11 (Al/P = 1.2) and
P4VP/AlPO4-11 (Al/P = 1.2) were obtained at 120 8C. The
pore size distributions were obtained from the adsorption
and desorption branch of the nitrogen isotherms by the
Barrett–Joyner–Halenda (BJH) method. Mesopore surface
areas and micropore volumes were determined by the t-
plot method. The temperature programmed desorption
(TPD) of NH3 was made using a TPD/TPR 2900 (Micro-
miritics Company). The products were characterized by 1H
and 13C NMR spectra (Bruker DRX-500 Avance spectrome-
ter at 500.13 and 125.47 MHz, respectively). Melting
points were measured on an electrothermal 9100 appara-
tus and reported without correction. All the products were
known compounds and they were characterized by FT-IR,
1H NMR and 13C NMR. All melting points were compared
satisfactorily with those reported in the literature.
2.3. Catalyst synthesis
Several AlPO4-11 with different gel compositions have
been synthesized (Table 1).
The basic catalytic activity and the shape-selectivity of
this organic-inorganic hybrid were tested for Knoevenagel
condensation in water and solvent-free condition.
2.3.1. Synthesis of AlPO4-11
AlPO4-11 was prepared using di-n-propylamine (n-
Pr2NH) as the template [10,11]. The control of the synthesis
condition especially Al/P ratio is a key factor for the
formation of an efficient support. We believe that the Al/P
ratio has a direct effect on acidic-basic property and
activity of the AlPO4 as the support. The catalysts with
varied Al/P atomic ratios were prepared under hydrother-
mal condition for choosing the best support for attachment
of poly(4-vinylpyridine) on the surface of AlPO4-11 (Table
1). The general procedure was as follows: aluminum tri-
isopropoxide (Al [iPrO]3) was dissolved in distilled water
and this mixture was stirred for 75 minutes. The
phosphoric acid (85% H3PO4) was added drop-wise and
the mixture was stirred for 75 minutes. After that, n-Pr2NH
was added drop-wise into the solution and the mixture
was stirred for 75 minutes to form a homogeneous gel. The
2. Experimental
2.1. Materials
All organic reagents were supplied from Sigma-Aldrich,
Merck, and were used as received without further
purification.
2.2. Characterization
The morphological and structural characteristics of the
AlPO4-11 supports and poly(4-vinylpyridine)/AlPO4 nano-
composites were measured by XRD (Bruker D8ADVANCE,
Cu K radiation), XRF (Bruker S4 Pioneer), FT-IR spectros-
a
Scheme 1. Polymerization of 4-vinyl pyridine in the presence of AlPO4-11.

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R.J. Kalbasi, E. Izadi / C. R. Chimie 14 (2011) 1002–1013
Table 1
Experimental conditions and results for the crystallization of AlPO4-11 molecular sieve using conventional heating.
Entry
Molar gel composition
Template
Al/P ratio
1.1:1.3
1.1:1.73
1.1:0.9
1.0:2.5
1.0:1.8
T (8C)
160
200
200
200
180
Time (h)
48
Starting PH
Product phase
AlPO4-11
1
2
3
4
5
1.1Al2O3:1.3P2O5:2DPA:50H2O
1.1Al2O3:1.73P2O5:1.6DPA:70H2O
1.1Al2O3:0.9P2O5:1.6DPA:70H2O
1Al2O3:2.5P2O5:1.6DPA:70H2O
1Al(i-PrO)3:1.8H3PO4:1.5EA:78H2O
Di-n-propylamine
Di-n-propylamine
Di-n-propylamine
Di-n-propylamine
Ethylamine
5.5
5.5
5.5
5.5
5.7
96
AlPO4-11
96
AlPO4-11
96
AlPO4-11
96
AlPO4-11 (90%)
DPA: di-n-propylamine; EA: ethylamine.
pH values of the prepared gels was adjusted to 5.5 by drop-
wise addition of mixture of HCl and H2O with molar ratio of
1:1, and this gel was transferred into a Teflon-lined
stainless steel autoclave and heated under autogenous
pressure at 200 8C for 96 hours. The nanocrystalline
products were obtained after they were filtered, washed
with distilled water and dried at 80 8C for 10 hours. The
sample was calcined under airflow at 405 8C for 5 hours to
remove the organic template material.
by hot ethanol to separate the catalyst. The solvent was
evaporated, and the resulting solids were obtained.
Products were confirmed by means of 1H and 13C NMR
spectroscopy. Another interesting aspect is the use of
catalyst in solvent-free condition. Activity of this nano-
composite significantly increased when the reaction was
carried out without solvent.
3. Results and discussion
The best molar gel composition that is chosen for
synthesis of the AlPO4-11 as an efficient support is Al/
P = 1.2 (Table 1, entry 3).
3.1. Characterization of the catalysts
3.1.1. XRD
2.3.2. Preparation of poly(4-vinylpyridine)/AlPO4-11
nanocomposite
Fig. 1 shows the X-ray powder diffraction patterns of
AlPO4-11 crystal and poly(4-vinylpyridine)/AlPO4-11 with
Al/P = 1.2 (Table 1, entry 3). The powder XRD pattern of
AlPO4-11 (Fig. 1a) indicates that the crystals are of pure
AEL structure [10,11]. The highly crystalline nature and the
phase purity of the AlPO4-11 are evident from the
intensities and absence of any spurious peaks. Fig. 1b
shows the XRD pattern for P4VP/AlPO4-11 which has the
same crystal structure and XRD pattern typical of AEL
topology. It demonstrates that the AEL structure of AlPO4-
11 was well retained after hybridization with P4VP. The
Various nanocomposites with AlPO4-11 containing
different Al/P molar ratios were synthesized and tested
for Knoevenagel condensation. The general procedure was
as follows: poly(4-vinylpyridine)/AlPO4-11 (P4VP/AlPO4-
11) was synthesized as follows (Scheme 2): AlPO4 (0.5 g)
and 4-vinylpyridine (0.5 mL) in THF (7 mL) were placed in a
round bottom flask. Benzoyl peroxide (0.033 g, 3% mol)
was added, and the mixture was heated to 70–75 8C for
5 hours while being stirred. The precipitate was collected
by filtration, washed several times with THF, and finally
dried at 60 8C overnight. Basic content of P4VP/AlPO4-11
nanocomposite was estimated by back-titration using
NaOH. Five millilitre of HCl (0.2 N) was added to 0.05 g of
this nanocomposite and stirred for 30 minutes. The
catalyst was removed and washed successively with
deionized water. The excess amount of HCl was titrated
with NaOH (0.1 N) in the presence of phenolphthalein as an
indicator. Basic sites content of catalyst with Al/P = 1.2 was
7.12 mmol/g.
2.4. General procedure for Knoevenagel condensation
The Knoevenagel condensation between benzaldehyde
and malononitrile at room temperature was chosen as the
standard reaction.
The general procedure was as follows: malononitrile
(1.0 mmol) was dissolved with 5.0 mL water as solvent and
P4VP/AlPO4-11 (0.12 g) was then added. Benzaldehyde
(1.0 mmol) was added to the reaction mixture in a round
bottom flask. The mixture was then stirred vigorously at
room temperature for 10 minutes. After the completion of
the reaction (monitored by TLC), using n-hexane/ethyla-
cetate (18:2) as eluent, the mixture was cooled and filtered
Fig. 1. XRD patterns of (a) AlPO4-11 and (b) P4VP/AlPO4-11 (Al/P = 1.2).

R.J. Kalbasi, E. Izadi / C. R. Chimie 14 (2011) 1002–1013
1005
characteristic peaks of the AlPO4-11 phase (i.e. 2
u
= 13, 15,
methods, respectively. BET surface area, total pore volume,
micropore volume and micropore surface area for AlPO4-
11 and P4VP/AlPO4-11 are presented in Table 2 (micropore
volumes were determined by the t-plot method).
21, 23, 26 and 35) were observed for both patterns.
Furthermore, the prominent peaks of P4VP/AlPO4-11
sample shift to higher angles compared to microporous
AlPO4-11 due to the decrease in pore diameter.
As can be seen from Fig. 3c, the isotherm proved the
presence of varied pores with different sizes between 1–
10 nm [10]. The micropore surface area and micropore
volume of AlPO4-11 is calculated about 50.7 m2/g and
0.28 cm3/g, respectively. We can notice that the polymeri-
zation of 4-VP into the aluminophosphate framework
leads to a decrease in the surface area and micropore
volume, which can be explained by a change in the pore
shape due to the polymerization of 4-VP within the pores
of the AlPO4-11. The isotherm of P4VP/AlPO4-11 (Fig. 3d)
exhibits uniform distribution of pores in comparison to
isotherm of AlPO4-11 (Fig. 3c) and exhibits a smaller pore
volume due to filling the pores with P4VP. It is shown that
the P4VP/AlPO4-11 nanocomposite has been successfully
synthesized with a microporous form, which can act as a
basic catalyst for Knoevenagel condensation.
3.1.2. SEM
SEM images of AlPO4-11 (Al/P = 1.2) and P4VP/AlPO4-11
(Al/P = 1.2) are given in Fig. 2. The surface texture of both
samples show spherical aggregates of small crystals and
wheat sheaf morphology [21]. No change is observed on
morphology of AlPO4-11 after hybridization with P4VP
(Fig. 2c, d), which is attributed to the polymerization of 4-
vinylpyridine in the pores of AlPO4-11, which is also
supported by the abrupt decrease in surface area and in
pore volume as shown in Table 2.
3.1.3. BET
The N2 adsorption-desorption isotherm of the AlPO4-11
(Al/P = 1.2) and P4VP/AlPO4-11 (Al/P = 1.2) at 77 K for
7 hours was also examined (Fig. 3). The isotherm (Fig. 3a, b)
exhibits a type I isotherm typical of microporous materials.
The specific surface area of the samples and the pore size
distributions had been calculated using Brunauer-
Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH)
3.1.4. FT-IR
The FT-IR spectra of AlPO4-11 (Al/P = 1.2) and P4VP/
AlPO4-11 (Al/P = 1.2) are shown in Fig. 4. They have
symmetric stretching bands at around 670/cm and 700/
Fig. 2. Scanning electron micrographs (SEM) of (a, b) AlPO4-11 (Al/P = 1.2) and (c, d) P4VP/AlPO4-11 (Al/P = 1.2).

1006
R.J. Kalbasi, E. Izadi / C. R. Chimie 14 (2011) 1002–1013
Table 2
Porosity data of AlPO4-11 and P4VP/AlPO4-11 samples.
Samples
BET surface
area (m2/g)
Micropore volume
(cm3/g)
Total pore Volume
(cm3/g)
Micropore surface area
(m2/g)
AlPO4-11
132.1
57.7
0.28
0.32
50.7
16.5
P4VP/AlPO4-11
0.154
0.165
ance of the above bands indicates the successful polymeri-
zation of pyridine ring in to the AlPO4-11 pores and the
P4VP/AlPO4-11 nanocomposite is obtained.
3.1.5. NH3–TPD
The TPD curve of AlPO4-11 is shown in Fig. 5. For AlPO4-
11 with Al/P = 1.2 (Table 1, entry 3), one desorption peak at
246.4 8C was assigned to ammonia desorption from weak
acid sites. The result shows that most of the ammonia
adsorbed on AlPO4-11 desorbed below 400 8C. The absence
of any additional peak at higher temperature indicates the
absence of strong acid sites in AlPO4-11. Yang et al. [24]
proposed that the weak acid sites be derived from weak
Lewis acid sites and terminal P–OH groups. The total
number of the acid sites was calculated from the amount of
ammonia desorbed. The amount of weak acid sites of
AlPO4-11 with Al/P = 1.2 is 6.04 mmol/g.
3.1.6. TG–DTA
Fig. 3. The N2 adsorption-desorption isotherm of (a) AlPO4-11 (Al/P = 1.2)
The TGA results of the AlPO4-11 (Al/P = 1.2), P4VP and
P4VP/AlPO4-11 (Al/P = 1.2) under N2 atmosphere are
presented in Fig. 6. The mass loss at 95 8C (around 8%, w/
w) is attributed to desorption of water present in the
pores and channels of the AlPO4-11 (Fig. 6a), and there is
no mass loss after this temperature, which demonstrates
that the structure of AlPO4-11 is stable after 95 8C. The
weight loss of P4VP begins at 210 8C because of
thermodegradation of P4VP polymer chains and the
weight loss at 500 8C is around 62% (Fig. 6b). Thermo
analysis of P4VP/AlPO4-11 shows two steps of mass loss
(Fig. 6c). The first step (around 5%, w/w) that occurs at
90 8C is related to desorption of water. The second step
(around 5%, w/w), which appeared at 350 8C is attributed
to degradation of the polymer. By comparing the P4VP
and P4VP/AlPO4-11 curves, one can find that the weight
loss of P4VP/AlPO4-11 occurs at a higher temperature; it
illustrates that P4VP/AlPO4-11 had higher thermal
stability and slower degradation rate than P4VP. As a
result, thermal stability of catalyst by hybridization is
and (b) P4VP/AlPO4-11 (Al/P = 1.2).
cm, which correspond to the O-P-O and O-Al-O, respec-
tively. The broad absorption band of AlPO4Àn molecular
sieves in the range of 1000–1200/cm is due to the
+
asymmetric stretching vibration of framework AlO4 and
À
PO4 [22]. In addition, bands centered at around 3600,
3460 and 1619/cm can be attributed to the hydrogen-
bonded hydroxyl groups and O–H vibration of H2O [23].
The vibration bands of di-n-propylamine (DPA) in the
region of 1400–1500/cm demonstrate the presence of DPA
in the pores of AlPO4-11, which remains in the pores after
calcination [23]. In the FT-IR spectrum of P4VP/AlPO4-11
(Fig. 4b), the appearance of the new bands at 1603, 1562
and 1417/cm is due to the characteristic absorptions of
pyridine ring [20]. The new band at 1603/cm corresponds
to the stretching vibration absorption of C-N bond and the
bands at around 1562 and 1417/cm are attributed to the
stretching vibration absorption of C=C bond. The appear-
Scheme 2. Schematic representation of P4VP interaction with AlPO4-11 and preparation of P4VP/AlPO4-11.

R.J. Kalbasi, E. Izadi / C. R. Chimie 14 (2011) 1002–1013
1007
Fig. 4. FT-IR spectra of (a) microporous AlPO4-11 (Al/P = 1.2) and (b) P4VP/AlPO4-11 (Al/P = 1.2).
improved and it is a very remarkable point for catalytic
application.
ꢀ
micropore structure of AlPO4 compared to mesopore
structure of SBA-15 could help to increase shape-
selectivity (described in section 3.5) [28]. The active
sites of the catalyst are considered to be the pyridyl
functional groups that confined located on the micro-
pores of the AlPO4-11. Accordingly, P4VP/AlPO-11 could
act as a shape selective catalyst in the Knoevenagel
reaction.
3.2. Catalytic activity
This novel nanocomposite was synthesized and char-
acterized. In order to investigate the possible activity of
P4VP/AlPO4-11 in the Knoevenagel condensation (Scheme
3), we investigated AlPOs prepared with various Al/P molar
ratios for choosing the best support for attachment of
poly(4-vinylpyridine) on the surface of AlPO4-11. We have
chosen AlPO4 to support the P4VP because the structure of
open-framework AlPOs has some specific characteristics
compared to mesoporous SBA-15:
ꢀ
ꢀ
controllable pore size distributions in AlPO4 can be
achieved by using different organic amine templates in
contrast to constant pore size of SBA-15 [25];
adjusting acidic-basic property of AlPO4 surface by using
various Al/P ratios for synthesis of AlPO4 to obtain a high
surface area as well as a high number of surfaces –OH
groups [26,27];
Fig. 6. TGA curves of (a) microporous AlPO4-11 (Al/P = 1.2) (b) P4VP (c)
Fig. 5. NH3–TPD curve of the AlPO4-11.
P4VP/AlPO4-11 (Al/P = 1.2).

1008
R.J. Kalbasi, E. Izadi / C. R. Chimie 14 (2011) 1002–1013
Scheme 3. Knoevenagel condensation catalyzed by P4VP/AlPO4-11.
The effect of various reaction parameters on the
According to the above concepts, it can be concluded
that by increasing the amount of P in the support, the
interaction of pyridine nitrogen atoms with the hydroxyl
protons (Bro¨nsted acid sites) on the surface of AlPO4
increases, and the basic sites of the catalyst decreases. So,
the activity of the catalyst decreases. Accordingly, we can
conclude that the best support is AlPO-11 with Al/
P = 1.2 molar ratio. This support has some P groups, and
so hydroxyl groups that are enough to interact with P4VP
for supporting them and the other free pyridine groups can
act as basic sites. These results are in accordance to the
data presented in Table 3 about basic content of catalysts
prepared with various Al/P molar ratios. On the other hand,
the nanocomposite containing the support with a high
amount of P (Al/P = 1/2.5, entry 1) shows a higher catalytic
activity than the supports with Al/P = 1/1.8 to 1.1/1.3
(entry 2, 3, 4). According to the concept mentioned in
section (a), by further increasing the P content, the sample
is changed to phosphate salt form and it leads to a decrease
in Bro¨nsted acid sites. Therefore, the interaction of pyridine
nitrogen atoms with the hydroxyl protons (Bro¨nsted acid
sites) on the surface of AlPO4 decreases and the basic sites
of the catalyst increases (Table 3, entry 1).
condensation of benzaldehyde with malononitrile were
studied at room temperature using P4VP/AlPO4-11 nano-
composite as catalyst and the results are as follows.
3.2.1. Effect of the Al/P ratio of support on the catalytic
activity
Various AlPO4-11 with different Al/P molar ratios in
molar gel composition have been synthesized (Table 1)
and tested for Knoevenagel condensation (Table 3).
According to the results in Table 3, these supports with
different Al/P ratios and surface acid-base properties lead
to different results in the Knoevenagel condensation. The
best yield was obtained when the Al/P was 1.2 (this ratio is
in accordance with the XRF result). The yield of the
reaction was increased with a decrease in P molar ratio. To
discuss this behavior the following concept should be
mentioned:
a. at first, the Bro¨nsted acid sites strength of AlPO4
increases with increasing P content due to the increase
in surface OH groups (Scheme 2). After that, by further
increasing the P content, the sample is changed to
phosphate salt form, and it leads to a decrease in
Bro¨nsted acid sites;
3.2.2. Effect of solvent
b. a possible adsorption mode for P4VP on the surface of
AlPO4 was a lone pair interaction between the pyridine
nitrogen atom and the hydroxyl protons (Bro¨nsted acid
sites) on the surface of AlPO4 [9]. Other interactions
The sensitivity of a heterogeneously catalyzed reaction
to different solvents can usually be of extreme importance
depending on the nature of the catalyst support material.
The Knoevenagel condensation was carried out at room
temperature using various non polar and polar solvents
such as H2O, Toluene, acetonitrile, tetrahydrofuran, n-
would be an interaction involving the pyridine ring
p-
interaction or a less specific Van Der Waals interaction
between the aliphatic polymer chain backbone and the
AlPO4 surface [29]. Two of these possibilities were
previously illustrated schematically in Scheme 2.
Table 4
Effect of solvent on Knoevenagel condensationa.
Solvent
Time (min)
10
Yield (%)b
98
Water
Table 3
Effect of the composition of the support (Al/P molar ratio) on the catalytic
activity of P4VP/AlPO-11a.
Acetonitrile
10
160c
5
20
Entry
Al/P ratio
Time (min)
Yield (%)b
Basic sites
(mmol/g)
Toluene
10
120c
35
70
1
2
3
4
1.0:2.5
1.0:1.8
1.1:1.73
1.1:1.3
1.1:0.9
10
10
10
10
10
80
60
60
70
98
7.10
6.20
6.80
7.12
7.12
Tetrahydrofuran
n-hexan
10
–
–
120c
10
160c
35
80
Solvent-free
2
98
5
a
Reaction conditions: P4VP/AlPO4-11 (0.12 g), benzaldehyde (1 mmol),
malononitrile (1 mmol), solvent (5 mL), room temperature.
a
Reaction conditions: benzaldehyde (1 mmol), malononitrile (1 mmol),
catalyst (0.12 g), H2O (5 mL), room temperature.
b
Isolated yield.
b
c
Isolated yield.
Time of maximum yield.

R.J. Kalbasi, E. Izadi / C. R. Chimie 14 (2011) 1002–1013
1009
Table 6
hexan and solvent-free conditions (Table 4). Our investi-
Effect of catalyst amount on Knoevenagel condensationa.
gations indicate that polar solvents, such as H2O with
highest polarity, gave high yield in a shorter period of time
at ambient temperature because of the polar nature of
P4VP/AlPO4-11 nanocomposite. Despite the Knoevenagel
condensation being a net dehydration, the reaction was
surprisingly favored in aqueous medium [30]. The simplest
interpretation of these results is due to the influence of the
solvent on the transition state. The intermediate is better
solvated by polar solvents and more stable in H2O as
solvent. In addition, surprising results were obtained when
we examined the same reactions under solvent-free
condition over P4VP/AlPO4-11 catalyst. The reaction
occurred much faster with higher yields at ambient
temperature. This result is attributed to bringing the
activated methylene compound in close proximity to the
basic sites of the catalyst under solvent-free condition.
Amount of catalyst (g)
Time (min)
Yield (%)b
–
240
15
6
–
0.06
0.08
0.1
80
98
98
98
98
5
0.12
0.14
2
2
a
Reaction conditions: benzaldehyde (1 mmol), malononitrile (1 mmol),
solvent-free, room temperature.
b
Isolated yield.
shown in Table 6. When the amount of catalyst increased
from 0.08 to 0.12 g, the reaction was completed in a shorter
time because of the availability of more basic sites, which
favors the dispersion of more active species. With a further
increase in catalyst amount to 0.14 g, it had no remarkable
effect on the percentage of yield and reaction time. It is not
of practical interest to use a large amount of catalyst. So,
the quantity of 0.12 g has been chosen as the optimized
weight of catalyst for Knoevenagel condensation. In order
to test the catalytic performance in the absence of catalyst,
the Knoevenagel condensation was carried out in absence
of catalyst at room temperature. No reaction was observed
in the absence of catalyst at room temperature, which
indicates an importance of the catalytic activity of the
P4VP/AlPO4-11.
3.2.3. Effect of AlPO4-11 amount on catalytic activity of P4VP/
AlPO4-11 nanocomposite
Catalytic activity of P4VP/AlPO4-11 was improved by
optimizing the different amount of AlPO4-11. The results
presented in Table
5 were obtained by Knoevenagel
condensation over P4VP/AlPO4-11 nanocomposite prepared
by different amounts of AlPO4-11 in which the amounts of
the AlPO4-11 were 0.0, 0.25, 0.5 and 1 g. The best yield of
Knoevenagel reaction was obtained when the ratio of AlPO4-
11 (g) to 4VP (mL) was 1:1. The results presented in Table 5
reveal that the higher amount of AlPO4 has no influence on
thecatalyticactivity of theP4VP/AlPO4-11. Itshould be noted
that the unfunctionalized AlPO4-11 is only very weakly
active in the Knoevenagel condensation with less than 10%
yield observed within 15 minutes. This indicated the
necessity of the poly(4-vinylpyridine) coating on the pores
of the AlPO4-11 to create basic sites. Also, a comparative
reaction by usingP4VP and P4VP/AlPO4-11 shows that P4VP/
AlPO4-11 is more active and efficient because of the larger
surface area and existence of micropores of P4VP/AlPO4-11
in comparison to P4VP. On the other hand, P4VP is adhesive,
and this characteristic makes it hard to separate from the
vessel, but after being mixed with AlPO4-11 and making
P4VP/AlPO4-11 nanocomposite, it becomes powdery which
is easy to be used and recycled.
3.3. Application of P4VP/AlPO4-11 in Knoevenagel
condensation of various aldehydes with malononitrile
In order to test the versatility of the catalyst, we
submitted various aromatic aldehydes and hetero-aromat-
ic aldehydes with malononitrile in the presence of P4VP/
AlPO4-11 nanocomposite at room temperature in aqueous
and solvent-free conditions (Scheme 3). Selected results
are shown in Table 7. All reactions investigated were
almost completed in 2–90 minutes in water as solvent and
1–7 minutes in solvent-free condition. Hetero-aromatic
aldehydes such as 2-pyridine carbaldehyde (entry 11, 12)
provided very good yields. Aromatic aldehydes with
electron withdrawing groups (ÀNO2, ÀCl) also offered
good yields and the reactions were completed in short
times. Also, in the case of electron donating groups
(ÀOCH3, ÀCH3), reasonably good yields were observed
but demanded a little more reaction time.
3.2.4. Effect of catalyst amount on Knoevenagel condensation
The effect of catalyst amount on the yield of Knoeve-
nagel condensation was investigated and the values are
3.4. Reusability of the catalyst
Table 5
Effect of AlPO4-11 amount on catalytic activity of P4VP/AlPO4-11
nanocompositea.
In order to know whether the catalyst would lose
catalytic activity during the Knoevenagel condensation,
after completion of the reaction, the catalyst was filtered
and washed thoroughly with acetone and dried in an oven
at 80 8C for 4 hours to be used in the next reaction cycle. It
was observed that the activity of the catalyst just
decreased to 90% after performing five regeneration
processes. Basic content of reused catalyst (after five
cycles) was estimated by back-titration using NaOH. Basic
sites content of reused catalyst (after five cycles) was
6.44 mmol/g. By comparing the amounts of basic sites
Amount of AlPO4-11/
4-VP (g/mL)
Time
Yield (%)b
Basic sites
(mmol/g)
(min)
0/0.5
0.25/0.5
0.5/0
15
6
75
98
10
98
98
9.50
5.20
–
15
2
0.5/0.5
1/0.5
7.12
7.10
5
a
Reaction conditions: benzaldehyde (1 mmol), malononitrile (1 mmol),
catalyst (0.12 g), solvent-free, room temperature.
b
Isolated yield.

1010
R.J. Kalbasi, E. Izadi / C. R. Chimie 14 (2011) 1002–1013
Table 7
Knoevenagel condensation of aromatic aldehydes and malononitrile catalyzed by P4VP/AlPO4-11a.
Entry
Substrate
Product
Time (min)
Yield (%)b
Mp (8C)
Ref.
Found
Reported
82–84
O
CN
C
C
C
CH
CH
1
2
98
98
98
60
98
81–83
[31,32]
[31,32]
[33]
H
CN
CN
O
C
2c
10
7
81–83
82–84
H
CN
O
CN
C
(H3C)2N
(H3C)2N
CH
C
C
(H3C)2N
(H3C)2N
3
182–183
182–183
96–98
180–182
180–182
95–96
CN
CN
H
O
4c
70
1
[33]
C
CH
CN
H
Cl
Cl
O
CN
5
[34]
C
CH
CH
C
C
CN
H
Cl
Cl
O
C
CN
CN
6c
8
1
5
98
98
98
96–98
95–96
[34]
[35]
[35]
H
Cl
Cl
Cl
Cl
CN
O
C
H
7
97–100
97–100
102–103
102–103
CH
C
CN
CN
CN
O
C
H
8c
CH
C
O
CN
C
H3C
H3C
H3C
H3C
CH
CH
C
C
9
3
98
98
98
132–134
132–134
92–94
133–135
133–135
95–96
[36]
[36]
[36]
H
CN
CN
O
C
10c
90
1
H
CN
CN
O
11
C
C
C
CN
N
N
N
N
C
H
H
CN
O
H
12c
10
98
92–94
95–96
[36]
C
CN
C
H

R.J. Kalbasi, E. Izadi / C. R. Chimie 14 (2011) 1002–1013
1011
Table 7 (Continued )
Entry
Substrate
Product
Time (min)
Yield (%)b
Mp (8C)
Ref.
Found
Reported
103–104
O2N
O2N
O2N
CN
CN
O
C
H
13
5
98
102–104
102–104
[37]
CH
CH
C
C
O2N
CN
CN
O
C
H
14c
17
98
103–104
[37]
O
CN
C
H3CO
H3CO
H3CO
H3CO
CH
C
15
2
98
98
112–113
112–113
114–115
114–115
[38]
[38]
H
CN
CN
O
C
16c
27
CH
C
H
CN
a
Reaction conditions: substrate (1 mmol), malononitrile (1 mmol), catalyst (0.12 g, P4VP/AlPO4-11), solvent-free, room temperature.
b
c
Isolated yield.
Solvent: H2O.
Table 8
(6.44 mmol/g) in the reused catalyst with the fresh catalyst
(7.12 mmol/g), it can be found that the basic site content of
the catalyst is reduced around 9% after performing five
regeneration processes. In addition, the yield of the
product is decreased to 90% (the yield was reduced around
8%). These results indicate that the activity of catalyst is
reduced after performing five regeneration processes
because the amount of basic sites of the catalyst is
reduced. It can be related to some polymer leaching.
Comparison of shape selectivity in Knoevenagel condensation over
different catalystsa.
Catalyst
Time
Temperature
Yield
(%)b
Ref.
(min)
(8C)
P4VP/SBA-15
P4VP/AlPO4-11
30
10c
40
RT
95
98
Our previous
study
30
120
10c
40
80
RT
50
90
98
This work
3.5. Investigation on shape selectivity of P4VP/AlPO4-11
a
Reaction conditions: benzaldehyde (1 mmol), ethyl cyanoacetate
(1 mmol), catalyst (0.12 g), H2O (5 mL).
Compared to the Knoevenagel reactions of ethyl
cyanoacetate with aromatic aldehydes, the reactions of
malononitrile with the same aromatic aldehydes were
especially rapid and were completed in 1–2 minutes
because the electron withdrawing ability of CN group is
stronger than that of carbonyl or carboxylic group. In this
section, we want to compare the shape selectivity of P4VP/
AlPO4-11 and P4VP/SBA-15 (prepared in our previous
study). Although, basic sites content of P4VP/AlPO4-11
(7.12 mmol/g) is almost similar to the P4VP/SBA-15
b
Isolated yield.
c
Reaction conditions: benzaldehyde (1 mmol), malononitrile (1 mmol),
catalyst (0.12 g), H2O (5 mL).
(7.24 mmol/g), the yield of Knoevenagel condensation
with ethyl cyanoacetate as an activated methylene
compound as shown in Table 8, on P4VP/SBA-15 was
higher than P4VP/AlPO4-11. It was demonstrated that
microporous AlPO4-11 showed better shape selectivity in
Scheme 4. Shape-selectivity of P4VP/AlPO4-11 in Knoevenagel condensation of benzaldehyde with various active methylene compounds.

1012
R.J. Kalbasi, E. Izadi / C. R. Chimie 14 (2011) 1002–1013
heterogeneous catalyst is a practical alternative for the
application of Knoevenagel reactions in view of the
following advantages such as: high catalytic activity, high
yield and 100% selectivity to the condensation product at
room temperature, shape-selectivity, easy separation of
the catalyst by simple filtration, waste minimization
without any side reactions such as self condensation,
dimerization or rearrangements and reusability of catalyst.
Many scientists recently reported the use of mesoporous
molecular sieves as catalysts in Knoevenagel condensation.
However, to the best of our knowledge, there is no report
on Knoevenagel reaction over microporous polymer/
aluminophosphate nanocomposite. Controllable pore size
distribution, adjusting acidic-basic property of AlPO4
surface and shape-selectivity of AlPO4 compared to SBA-
15 are the main reasons for the application of AlPO4-11 as
support. This new catalyst can be useful for basic
heterogeneous catalysis, particularly for the shape-selec-
tive synthesis under solvent-free condition. Our results
here demonstrate the feasibility of applying microporous
AlPO4-11 as catalyst supports for synthesis the shape-
selective heterogeneous catalysts that are comparable to
SBA-15 mesoporous catalyst supports. We believe that
investigating the structure of microporous aluminopho-
sphates is useful for the catalyst design and future
development of the application of these materials as
support.
Scheme 5. Shape-selectivity of P4VP/AlPO4-11 in Knoevenagel
condensation of bulky aldehydes with malononitrile.
comparison to mesoporous SBA-15 because the pore size
of microporous AlPO4-11 is smaller than SBA-15. The ethyl
cyanoacetate molecules are too large to penetrate the
narrow pores of P4VP/AlPO4-11 but the malononitrile
molecules are smaller than ethyl cyanoacetate molecules
so they can penetrate easily into the pores of P4VP/AlPO4-
11 (Scheme 4). But ethyl cyanoacetate molecules cannot
penetrate the pores of P4VP/AlPO4-11, and so the
condensation reaction between benzaldehyde and ethyl
cyanoacetate occurs on the external surface of the catalyst.
Accordingly, the activity of P4VP/AlPO4-11 for Knoevena-
gel condensation between benzaldehyde and ethyl cya-
noacetate is low. On the other hand, this condensation in
the presence of P4VP/SBA-15 with the same basic sites of
catalyst occurs very easily. These results suggest that
shape selectivity of AlPO4-11 for ethyl cyanoacetate
compared to SBA-15 is due to the pore size of AlPO4-11
and not to the difference in basic sites content.
Also, in order to examine the shape-selectivity of the
catalyst, 2-propylbenzaldehyde, 3-propylbenzaldehyde
and 4-propylbenzaldehyde were allowed to react with
malononitrile in the presence of P4VP/AlPO4-11 as a
catalyst. As shown in Scheme 5, the catalyst was able to
discriminate between the aldehydes with different steric
effects. As we can see from the Scheme 5, alkene produced
major only from 4-propylbenzaldehyde. From these data,
we can conclude that the reaction just occurs in the
micropores of the catalyst and it doesn’t occur on the outer
surface of the catalyst or in the solution.
Acknowledgments
Supported by Islamic Azad University, Shahreza Branch
(IAUSH) Research Council and Center of Excellence in
chemistry, which is gratefully acknowledged.
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