Synthesis and characterization of functionalized NaP Zeolite@CoFe2O4 hybrid materials: a micro–meso-structure catalyst for aldol condensation

Article abstract of DOI:10.1007/s11164-020-04085-z

In this work, magnetic nanocomposite of NaP Zeolite and CoFe₂O₄ as magnetic nanoparticles (MNP’s) with different ratios were prepared and in the second step functionalized with 2-aminopyridine as a basic group. All samples were characterized by FT-IR, XRD, VSM, FESEM, EDX, TEM, and BET and thermal analyses. The results show that CoFe₂O₄ MNP’s was dispersed on NaP Zeolite without any significant aggregation with particle size about 30–50?nm. The BET and TEM confirmed the presence of mesoporous phase in the surface of NaP Zeolite/CoFe₂O₄ and preparation a micro–meso-structure. The NaP Zeolite/CoFe₂O₄ and NaP Zeolite/CoFe₂O₄/Am-Py were used as acid–base catalysts for aldol condensation of cyclohexanone with benzaldehyde, and furfural with acetone which produce curcumin and biofuel intermediates, respectively, in solvent-free condition. The effect of different factors such as the percent of CoFe₂O₄ MNP’s, catalyst amount, solvent, time and temperature was investigated. The catalyst was easily separated with an external magnet and reused four times without significant change in the yield. These catalysts have various advantages including high loading capacity, low leaching for CoFe₂O₄ MNP’s and simple and efficient recovery procedure which can be used under mild and ecofriendly condition.

Full text of DOI:10.1007/s11164-020-04085-z

Research on Chemical Intermediates
https://doi.org/10.1007/s11164-020-04085-z
Synthesis and characterization of functionalized NaP
Zeolite@CoFe O hybrid materials: a micro–meso‑structure
2
4
catalyst for aldol condensation
Zohreh Mortezaei · Mojgan Zendehdel1,2 · Mohammad Ali Bodaghifard1,2
1
Received: 16 October 2019 / Accepted: 9 January 2020
©
Springer Nature B.V. 2020
Abstract
In this work, magnetic nanocomposite of NaP Zeolite and CoFe O as magnetic
2
4
nanoparticles (MNP’s) with diꢀerent ratios were prepared and in the second step
functionalized with 2-aminopyridine as a basic group. All samples were character-
ized by FT-IR, XRD, VSM, FESEM, EDX, TEM, and BET and thermal analyses.
The results show that CoFe O MNP’s was dispersed on NaP Zeolite without any
2
4
signiꢁcant aggregation with particle size about 30–50 nm. The BET and TEM con-
ꢁ
rmed the presence of mesoporous phase in the surface of NaP Zeolite/CoFe O
2 4
and preparation a micro–meso-structure. The NaP Zeolite/CoFe O and NaP Zeo-
2
4
lite/CoFe O /Am-Py were used as acid–base catalysts for aldol condensation of
2
4
cyclohexanone with benzaldehyde, and furfural with acetone which produce cur-
cumin and biofuel intermediates, respectively, in solvent-free condition. The eꢀect
of diꢀerent factors such as the percent of CoFe O MNP’s, catalyst amount, solvent,
2
4
time and temperature was investigated. The catalyst was easily separated with an
external magnet and reused four times without signiꢁcant change in the yield. These
catalysts have various advantages including high loading capacity, low leaching for
CoFe O MNP’s and simple and eꢂcient recovery procedure which can be used
2
4
under mild and ecofriendly condition.
Keywords Zeolite/CoFe O · Functionalization · Aminopyridine · Micro–meso-
2
4
structure · Aldol condensation
*
Mojgan Zendehdel
m-zendehdel@araku.ac.ir; mojganzendehdel@yahoo.com
1
2
Department of Chemistry, Faculty of Science, Arak University, Arak 38156-8-8349, Iran
Institute of Nanosciences and Nanotechnology, Arak University, Arak, Iran
Vol.:(012
1
3456789)
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Z. Mortezaei et al.
Introduction
Organic transformations are very important, and their products are used in many
areas such as biology, pharmacology and industry [1–3]. Based on the principles
of green chemistry, designing novel and high eꢂcient catalysts is important for
organic synthesis. Then, the preparation of recoverable heterogeneous catalysts
has been a long goal in catalyst research. Recent studies have shown that hybrid
materials such as inorganic–inorganic [4, 5] or inorganic–organic [5, 6] material
were widely used as some heterogeneous catalysts for organic reactions. Also,
during the last decade signiꢁcant eꢀorts have been devoted to the development
of catalysts with both acid and base sites guaranteeing a large number of highly
active and fully accessible catalytic sites for organic reaction [7].
Increasing attention has recently been paid to the use of magnetic nanopar-
ticles (MNPs) as support [8, 9]. One of the important magnetic materials with
spinel structure is cobalt ferrite (CoFe O ) which is due to high eꢂciency, low
2
4
leaching of cobalt and ferromagnetic nature, and easy separation from aqueous
solution usually is promising as a catalyst for organic synthesis [10, 11]. It is
well known that magnetic particles synthesized by diꢀerent methods are usually
agglomerated and their speciꢁc area and catalytic eꢂciency decreased [12, 13].
An eꢀective method to prevent the agglomeration is dispersing of particles on
a stable support. The porous materials, such as zeolites with good acidity, high
surface areas and well-deꢁned structures, can be used as a support for diꢀerent
materials. However, introducing CoFe O MNP’s to zeolite may decrease the cat-
2
4
alytic activity due to diꢀusion limitation of microporous materials, but increase
the acidity. There are many reports which show the surface of MNP’s function-
alized by diꢀerent materials such as organic, organometallic and acidic groups
which are useful for many organic reactions [14, 15].
Although the surface of the MNP’s and zeolite with free silanol groups
(
Si–OH) are suitable agents for functionalization [16, 17], immobilizing of amine
groups to Zeolite/CoFe O has not yet been reported.
2
4
Aldol condensation is one of well-known organic syntheses to form the C–C
bond which was done in the presence of either basic or acidic catalysts such as
zeolite [18], MgO–ZrO [19], MFI [20], MnFe O /g–C N [21]. The aldol prod-
2
2
4
3
4
ucts are found in many natural compounds such as antibiotics, bioactive and bio-
mass-derived materials. For example, some works proposed a method to obtaining
high length of carbon chain diesel fuels; the key step of it is the aldol condensa-
tion between furfural and acetone [22–24]. Although many of these recyclable
catalysts are environmentally friendly, acidic sites can be catalyzed side reactions
and produce coke and deactivate the catalyst [25]. Also, in the basic media the
product of aldol condensation depends on the condition of preparation [26].
The goal of the present study is to design and develop a new hybrid catalyst
which can be used as heterogeneous acid–base catalyst for aldol condensation
reaction. For that purpose, the NaP Zeolite/CoFe O nanocomposites were pre-
2
4
pared and functionalized with 2-aminopyridine; then the prepared catalysts (NaP
Zeolite/CoFe O /Am-Py) were used for two sets of aldol condensation reaction.
2
4
1
3

Synthesis and characterization of functionalized NaP…
In this approach, the structure of catalyst and its eꢂciency in organic reactions
were considered.
Experimental
Materials and methods
All materials and solvents were purchased from Aldrich and Merck. Fourier Trans-
form Infrared analysis was recorded by a Galaxy series FT-IR 5000 spectrometer.
The patterns of X-ray diꢀraction were recorded by an X-Ray diꢀractometer (Philips
1
840) with Cr-Kα radiation. The chemical compositions of the samples were deter-
mined by elemental analysis (Vario E1III)) and energy-dispersive X-ray spectros-
copy (Oxford X-max). The thermogravimetric analysis (TGA) and diꢀerential ther-
mal analysis (DTA) were performed using a Diamond Pyris TM, TG/DT 6300 from
3
0 to 600 °C at a heating rate of 10 °C/min under argon ꢃow. Scanning electron
microscope (SEM) images of the samples were obtained using a Zeiss Sigma-VP
FESEM instrument. Brunauer-Emmett-Teller apparatus (SIBATA, App, 1100-SA
with adsorption of nitrogen at 76.34 K) was used. VSM analysis was carried out by
AGFM operation and EM900/ZISS. A Bruker Avance 300 MHz spectrometer was
1
used for HNMR spectra to characterization of organic compound. The high-resolu-
tion transmission electron microscopy (HRTEM) images of samples were obtained
using a Zeiss Libra (200 kV). The products were analyzed by an Agilent 7890A GC
unit equipped with a ꢃame ionization (FID) detector using a HP-5 capillary column
(
30 m/0.32 ID/0.25 m) and the gas chromatography–mass spectrometry (GC–MS)
analysis.
Synthesis of CoFe O nanoparticles
2
4
The CoFe O nanoparticle was synthesized according to a previously reported pro-
2
4
cedure [27]. 1.19 g of CoCl ·6H O and 2.70 g of FeCl ·6H O were added in 50 mL
2
2
3
2
deionized water. Then, a solution of NaOH (3 mol/L) was added to it and stirred
at 80 °C for 1 h under N atmosphere. The mixture of reaction was cooled to room
2
temperature, and the solid product was separated by an external magnet and washed
with ethanol and then dried under vacuum at 50 °C for 24 h.
Preparation of NaP Zeolite/CoFe O nanocomposites
2
4
Diꢀerent amounts of CoFe O (0.125, 0.250, 0.375, 0.500 g) were added to a fresh
2
4
gel of zeolite with the molar composition of 320 H O:16 NaOH:1 Al(OH) :15 SiO
2
3
2
which agitated for 5 days and stirred for 5 h and ꢁnally placed in an autoclave at
00 °C for 24 h. After cooling the reaction mixture to room temperature, the solid
material (NaP Zeolite/CoFe O nanocomposite) was ꢁltered and washed with water
1
2
4
until pH=9 and dried in air [28].
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Z. Mortezaei et al.
Preparation of NaP Zeolite/CoFe O /Am‑Py nanocomposites
2
4
In the ꢁrst step, 1 mmol of 3-chloropropyltrimethoxysilane (3-ClPTMS) was reacted
with 1.2 mmol 2-aminopyridine in 5 mL dry toluene at 90 °C under nitrogen atmos-
phere for 30 h. The resulting material (3-APPTMS) was added to 0.5 g of NaP
Zeolite/CoFe O composite in 10 mL dry toluene reꢃuxing for 24 h under nitrogen
2
4
atmosphere. Finally, the solid material, NaP Zeolite/CoFe O /Am-Py, was ꢁltered,
2
4
◦
washed by chloroform, ethanol and water, respectively, and dried at 100 C for 24 h
and then was characterized by FT-IR, XRD, TEM, SEM, EDS, TGA, BET and VSM
techniques [29].
Consideration of the catalytic activity (aldol condensation)
To consider the catalytic activity of prepared hybrid material, two reactions were
selected which are explained as follow: (a) at a 10 ml ꢃask, 1 mmol cyclohexanone
was added to 2 mmol of 4-X-benzaldehyde derivatives and then diꢀerent amounts
of catalysts (NaP Zeolite/CoFe O and NaP Zeolite/CoFe O /Am-Py) were added
2
4
2
4
to the mixture. The reaction mixtures were magnetically stirred at room temperature
and under nitrogen atmosphere. The reactions were monitored by TLC. After com-
pletion, the catalyst was separated with a magnet and the solid residue, recrystal-
lized with ethanol to give the pure product.
(b) Aldol condensation reaction was carried out in 10-mL ꢃask. Diꢀerent
amounts of catalyst were added to a mixture of 0.43 ml of furfural and a certain
amount of acetone (the mole ratios of furfural/acetone are 1:10, 1:5, 1:2). Thereaf-
ter, the mixture was reꢃuxed at 100 °C under stirring for diꢀerent times. After reac-
tion completion as monitored by TLC, the ꢃask was quickly cooled down to room
temperature using an ice bath. Then, the resulting solid product was ꢁltered and
recrystallized with ethanol for several times to remove the remained organics and
was identiꢁed based on the standard reference compounds and GC–MS analyses.
Results and discussion
The alkylaminopyridine-decorated NaP Zeolite/CoFe O nanocomposite (NaP Zeo-
2
4
lite/CoFe O /Am-Py) as a hybrid acid–base heterogeneous catalyst was prepared
2
4
sequentially depicted in Scheme1. CoFe O nanoparticles were prepared by co-pre-
2
4
cipitation method (Fe+ and Co ions in basic solution). The diꢀerent amounts of
3
+2
Scheme1 The sequential synthesis of NaP Zeolite/CoFe O /Am-Py hybrid material
2
4
1
3

Synthesis and characterization of functionalized NaP…
CoFe O (0.125, 0.250, 0.375, 0.500 g) were added to a fresh gel of zeolite to obtain
2
4
the NaP Zeolite/CoFe O nanocomposites. The obtained nanocomposite was func-
2
4
tionalized by (3-Aminopyridinopropyl) triethoxysilane (3-APPTS) to produce ami-
nopyridine-decorated magnetic hybrid nanomaterial (NaP Zeolite/CoFe O /Am-Py).
2
4
FT‑IR spectra
The FT-IR spectroscopic data for pure CoFe O nanoparticles and NaP Zeolite/
2
4
CoFe O nanocomposite with diꢀerent amounts of CoFe O , before and after func-
2
4
2
4
tionalization by alkylaminopyridine, are summarized in Table 1.
−1
−1
Literature reviews show the bands at 417 cm and 592 cm that involves the
+3
−2
stretching vibration of Fe–O (Fe –O ) on the octahedral and tetrahedral sites, [30]
after creating NaP Zeolite/CoFe O nanocomposite has been hidden due to the broad
2
4
−
1
bands related to zeolite structure. The appearance a peak at 1012 cm attribute to
−
1
the asymmetric stretching of Al–O–Si chain and two bonds about 745 and 437 cm
related to symmetric stretching and bending frequency of Al–O–Si, respectively was
conꢁrmed the presence of NaP zeolite in the nanocomposite structure [31]. Several
−1
−1
bonds about 1422, 2958 cm and 1731, 3450 cm relating to C–N, C–H and N–H
groups, related to alkylaminopyridine moiety can be observed. The peaks at 3434
and 1625 cm− are assigned to O–H stretching.
1
XRD analysis
The XRD patterns for CoFe O , NaP Zeolite/CoFe O and NaP Zeolite/CoFe O /
2
4
2
4
2
4
Am-Py are shown in Fig. 1A and B. It can be observed seven characteristic peaks
at the 2θ values of 18.6, 31.6, 36.0, 45.6, 54.1, 56.9 and 66.5, which corresponded
to (1 1 1), (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1) and (4 4 0) reꢃections, respec-
tively [Fig. 1A (a)] and conꢁrm the cubic reverse spinel phase of CoFe O (JCPDS
2
4
2
21086) [32].
After introducing diꢀerent amounts of CoFe O to zeolite structure, all the com-
2
4
posites show similar characteristic peaks (2θ=12.48°, 17.92°, 21.79°, 28.1° and
3
3.4°) Fig. 1A (b–e) [33] related to NaP Zeolite beside the CoFe O reꢃections.
2
4
Also, the results show that after functionalization of NaP Zeolite/CoFe O nano-
2
4
composite by alkylaminopyridine [Fig. 1B (f–i)], due to interaction of 3-ClPTMS
with zeolite, small amounts of amorphous phase were observed [12]. It seems the
modiꢁcation of NaP Zeolite/CoFe O nanocomposite surface did not signiꢁcantly
2
4
aꢀect the crystallinity of CoFe O phase but decreasing the intensity suggests that
2
4
some of these MNPs are incorporated to the zeolite pores which is in agreement to
other reports [34, 35].
The crystallite size of these as-synthesized CoFe O in the composite with dif-
2
4
ferent percent was estimated from the full width at half maximum (FWHM) of
strongest diꢀraction peak 2θ = 54.1 using the Scherrer’s equation [29], D = 0.9
λ/(β Cos 2θ) where D is the crystallite size, λ is the wavelength of Cr-Kα radia-
tion, β is FWHM, and θ is the diꢀraction angle of the strongest characteristic
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Z. Mortezaei et al.
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3

Synthesis and characterization of functionalized NaP…
Fig. 1 The XRD pattern, Part A: for CoFe O (a), NaP Zeolite/CoFe O (1:1) (b), NaP Zeolite/
2
4
2
4
CoFe O (1:2) (c), NaP Zeolite/CoFe O (1:3) (d), NaP Zeolite/CoFe O (1:4) (e), Part B: for NaP Zeolite/
2
4
2
4
2
4
CoFe O /Am-Py (1:1) (f), NaP Zeolite/CoFe O /Am-Py (1:2) (g), NaP Zeolite/CoFe O /Am-Py (1:3)
2
4
2
4
2
4
(
h), NaP Zeolite/CoFe O /Am-Py (1:4) (i)
2 4
peak. The data show that the crystallite size of MNPs was increased from 50 nm
to the range of 60–100 nm when introduced to composite which may be due to
agglomeration.
Figure 2A and B shows the low-angle XRD region for NaP Zeolite/CoFe O
2
4
and NaP Zeolite/CoFe O /Am-Py nanocomposite, respectively. The results show
2
4
the low intensity of Bragg X-ray reꢃections about 2θ = 1.8°, 3.9° and 4.4° related
to the lines (100), (110) and (200) that can be indexed as a hexagonal mesoporous
material [36], indicating that the obtained mesoporous are not completely
ordered. Also the intensity of reꢃections was decreased after functionalization by
amine group which may be due to the lack of structural order in mesoscale mate-
rial [37] and creating amorphous phase.
The nitrogen adsorption/desorption
The nitrogen adsorption/desorption isotherm and the pore size distribution of
NaP Zeolite/CoFe O with 1:2 and 1:4 percent before and after functionali-
2
4
zation are described in Fig. 3A and B. A sudden increase in the N isotherm
2
[
Fig. 3A (a, b)] at the low-pressure region about P/P0 < 0.1 conꢁrms the exist-
ence of microporous phase [38]. Also, the presence of hysteresis loop at pres-
sure P/P0 of 0.5–1, that is the type-IV isotherm, indicates the mesoporous phase
[
39]. The results show that after functionalization of NaP Zeolite/CoFe O with
2 4
amine [Fig. 3B (a, b)] the microporous phase decreased and also a rapid increase
at high-pressure region about P/P0 > 0.9 suggests the existence of macroporous
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Z. Mortezaei et al.
Fig. 2 The XRD in low angle range, Part A: NaP Zeolite (a), NaP Zeolite/CoFe O (1:1) (b), NaP Zeo-
2
4
lite/CoFe O (1:2) (c), NaP Zeolite/CoFe O (1:3) (d), NaP Zeolite/CoFe O (1:4) (e) Part B: for Nap
2
4
2
4
2
4
(
a) and NaP Zeolite/CoFe O /Am-Py (1:1) (b), NaP Zeolite/CoFe O /Am-Py (1:2) (c), NaP Zeolite/
2
4
2
4
CoFe O /Am-Py (1:3) (d), NaP Zeolite/CoFe O /Am-Py (1:4) (e)
2
4
2
4
Fig. 3 Nitrogen adsorption/desorption isotherms and BJH Plot of part A: NaP Zeolite/CoFe O (1:2) (a),
2
4
NaP Zeolite/CoFe O (1:4) (b) and part B: NaP Zeolite/CoFe O /Am-Py (1:2) (a), NaP Zeolite/CoFe O /
2
4
2
4
2
4
Am-Py (1:4) (b)
1
3

Synthesis and characterization of functionalized NaP…
phase [40]. The decrease in the pore volume and pore area after functionaliza-
tion of zeolite by alkylaminopyridine can be attributed to the introducing some
of amine groups into the NaP Zeolite/CoFe O nanocomposite and also creating
2
4
new mesophase on the surface of zeolite.
Also the results in Table 2 (calculated using BET, BJH, and t-Plot methods)
show that after introducing CoFe O in the zeolite framework, the surface area
2
4
2
for NaP Zeolite (45 m /g) increased due to increasing the mesophase which con-
ꢁ
rms the presence of hierarchical structure for zeolite. The pore size distribution
in Fig. 3A and B for all cases shows two ranges of particle size 1–8 nm cor-
responding to mesoporous phase and greater than 8 nm related to microporous
phase and conꢁrms this conclusion [12, 41].
SEM, TEM, EDX and elemental analysis
The SEM images of the CoFe O nanoparticles and NaP Zeolite/CoFe O nano-
2
4
2
4
composite with 1:2 and 1:4 ratios before and after functionalization are shown
in Fig. 4a–h. Figure 4a and b shows quasi-spherical morphology for CoFe O
2
4
nanoparticles and exhibits a rough surface and average diameter of about 40 nm.
After introducing magnetic nanoparticles into zeolite, wool ball-like [42] mor-
phology was observed for 1:2 (c, d) and 1:4 (e, f) ratios and also the presence
of spherical MNPs which have been shown by yellow circles. For NaP Zeolite/
CoFe O with higher percent of MNPs, small agglomeration can be observed
2
4
(
Fig. 4f) which conꢁrms the particle size increasing in Scherrer’s equation.
The images for functionalized NaP Zeolite/CoFe O with 1:2 and 1:4 ratios in
2
4
Fig. 4g and h, respectively, show that the morphology of NaP Zeolite is not
changed, but the percent of amorphous phase increased. Figure 5a–d shows that
the Co and Fe uniformly were dispersed over the zeolite support (NaP Zeolite/
CoFe O ) with 1:2 ratios.
2
4
The size and shape of NaP Zeolite/CoFe O nanocomposite (1:2 and 1:4)
2
4
are observed in Fig. 6a–d using high-resolution TEM. The images show that
the quasi-spherical CoFe O with average diameter about 38 nm completely
2
4
dispersed on zeolite in the 1:2 ratios without any agglomeration, but with
increasing the percent of CoFe O , in some parts agglomeration can be seen.
2
4
Also closer images of TEM (Fig. 6b, d) show the intracrystalline worm-like
mesoporous phase without any order in the surface of samples which these
results are in agreement with other literature reports [43]. Also, after function-
alization of NaP Zeolite/CoFe O nanocomposite with aminopyridine moiety
2
4
in two diꢀerent ratios (NaP Zeolite/CoFe O /Am-Py), mesoporous phase was
2
4
decreased (Fig. 6e, f) which conꢁrms the small amounts of amorphous phase
which observed in XRD and decreasing S
in BET.
meso
The chemical composition of materials was considered by EDX and elemental
analysis (C, H, N) (Table 3). The results for the C/N (about 2.8) and Si/Al~2.3) and
Fe/Co (about 2) in all samples are very close to real ratios and conꢁrm the presence
of NaP Zeolite, CoFe O and alkylaminopyridine in the nanocomposite.
2
4
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Z. Mortezaei et al.
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3

Synthesis and characterization of functionalized NaP…
Fig. 4 The SEM images of the CoFe O (a, b) nanoparticles and NaP Zeolite/CoFe O with 1:2 and 1:4
2
4
2
4
ratios before (c, d) (e, f) and after functionalize with amine (g, h)
Thermogravimetric analysis
The TGA and DTG curves of NaP/CoFe O samples before and after functionaliza-
2
4
tion at diꢀerent ratios (1:2 and 1:4) are shown in Fig. 7A and B, respectively. The
TGA curve as shown in Fig. 7A is divided into three steps. The ꢁrst weight loss
in 30–200 °C is attributed to the removal of physisorbed and chemisorbed water.
The second step, for NaP Zeolite/CoFe O accompanied with endothermic peaks
2
4
in DTG, can be corresponded to the dehydration of the hydroxyl groups inside the
micro- and meso-phases [44, 45] and also changing the structure of CoFe O . In the
2
4
case of NaP Zeolite/CoFe O /Am-Py hybrid material, the percent of weight loss in
2
4
the second step increased about 4% due to thermal decomposition of the organic
moiety and also in the DTA curves two endothermic peaks can be seen; the ꢁrst
peak about 200–320 °C conꢁrmed the presence of alkylaminopyridine in the struc-
ture [45, 46]. The last steps might be related to some transformations of phase of
gismondine-like structures and CoFe O , respectively [31].
2
4
The measurement of magnetic properties (VSM)
The magnetic properties of CoFe O , NaP Zeolite/CoFe O , and NaP Zeolite/
2
4
2
4
CoFe O /Am-Py samples were examined using a vibrating sample magnetometer
2
4
(
VSM) from −20 000 to 20 000 Oe at room temperature (Fig. 8 and Table 4). The
results in Table 4 show that the saturation magnetizations of the CoFe O MNPs are
2
4
about 67.58% of the CoFe O bulk materials value. CoFe O is well-known hard
2
4
2
4
magnetic material due to its high saturation magnetization about 80 emu/g and high
coercivity 5400 Oe; these values depended on particle size and synthesis methods
[
47].
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Z. Mortezaei et al.
Fig. 5 Elemental mapping of NaP Zeolite/CoFe O nanocomposite with 1:2 ratios (a–c) and 1:4 ratio (d)
2
4
MNPs are introduced to NaP Zeolite with diꢀerent ratio and also after functionalize
amine decreased. These results may be due to (1) increasing size of MNps after intro-
ducing zeolite (2) high interaction between CoFe O nanoparticles and zeolite (3) and
2
4
covering of nanoparticles by zeolite and alkylaminopyridine [48, 49]. Also, the shape
of slope in the magnetic hysteresis loops conꢁrmed that all materials exhibit non-neg-
ligible coercivity (Hc) and very low remanence (Mr) at room temperature, indicating
superparamagnetic behavior for all samples [50, 51]. Also, same as other works with
introducing CoFe O to NaP Zeolite and functionalization by alkylaminopyridine, the
2
4
both saturation magnetization and coercivity of the composites are lower than its bulk
values.
1
3

Synthesis and characterization of functionalized NaP…
Fig. 6 The TEM images for NaP Zeolite/CoFe O (1:2) (a, b), NaP Zeolite/CoFe O (1:4) (c, d), NaP
2
4
2
4
Zeolite/CoFe O /Am-Py (1:2) (e) and NaP Zeolite/CoFe O /Am-Py (1:4) (f)
2
4
2
4
Table 3 The elemental analysis
Sample
% O
C/N Si/Al Fe/Co
of NaP Zeolite/CoFe O
2
4
nanocomposite and NaP
CoFe O
48.97
40.32
41.89
–
–
–
–
1.94
2
4
Zeolite/CoFe O /Am-Py hybrid
2
4
NaP Zeolite/CoFe O (1:2)
NaP Zeolite/CoFe O (1:4)
2.26 1.97
2.36 2.00
material
2
4
2
4
NaP Zeolite/CoFe O /Am-Py (1:2) 41.03 2.79 2.27 1.84
2
4
NaP Zeolite/CoFe O /Am-Py (1:4) 40.30 2.74 2.31 1.93
2
4
Catalytic activity
We know the aldol condensation as one of the most important reactions to forming
C–C bonds, and the condensation of cycloalkanones with aldehydes and ketones has
been widely used for preparation of many compounds such as antibiotics and bioac-
tive materials [52–54]. The preparation of these compounds such as curcumin which
have excellent anti angiogenic eꢀects is important for future animal model studies.
Then, this work focused on the preparation of these compounds by easy, economical
and mild conditions.
The aldol condensation results of cyclohexanone with benzaldehyde derivatives
with diꢀerent ratio of catalysts (NaP Zeolite/CoFe O and NaP Zeolite/CoFe O /
2
4
2
4
Am-Py) are shown in Table 5. The results indicate that the pure CoFe O and NaP
2
4
1
3

Z. Mortezaei et al.
Fig. 7 TGA curves (part A) and DTG curves (part B) of NaP Zeolite/CoFe O /Am-Py (1:1) (a), NaP
2
4
Zeolite/CoFe O /Am-Py (1:2) (b), NaP Zeolite/CoFe O /Am-Py (1:3) (c), NaP Zeolite/CoFe O /Am-Py
2
4
2
4
2
4
(
1:4) (d)
Fig. 8 Magnetic hysteresis curves of CoFe O (a), NaP Zeolite/CoFe O4 (1:4) (b) and NaP Zeolite/
2
4
2
CoFe O /Am-Py (1:4) powders (c)
2
4
1
3

Synthesis and characterization of functionalized NaP…
Table 4 The magnetic properties of CoFe O nanoparticles, NaP Zeolite/CoFe O nanocomposite, and
2
4
2
4
NaP Zeolite/CoFe O /Am-Py hybrid nanomaterial
2
4
Sample
Ms (emu/g)
Mr (emu/g)
Hc (Oe)
CoFe O
NaP Zeolite/CoFe O (1:2)
NaP Zeolite/CoFe O (1:4)
NaP Zeolite/CoFe O /Am-Py (1:2)
46.40
24.72
31.36
12.97
16.81
26.30
15.30
18.92
7.05
2500
2500
2500
2500
2500
2
4
2
4
2
4
2
4
NaP Zeolite/CoFe O /Am-Py (1:4)
9.49
2
4
Table 5 Aldol condensation of cyclohexanone with benzaldehyde derivatives over catalysts. Reaction
conditions: cyclohexanone (1 mmol), 4-X-benzaldehyde (X=H, Cl) (2 mmol), reaction temperature
(
room temperature) and reaction time (16 h), Catalyst amount (20 mg)
Entry
Catalyst
Solvent
Aldehyde
Yield (%)
1
2
3
4
5
6
7
8
9
NaP Zeolite
NaP Zeolite
CoFe O
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
CH Cl
Benzaldehyde
4-Chlorobenzaldehyde
Benzaldehyde
4-Chlorobenzaldehyde
Benzaldehyde
4-Chlorobenzaldehyde
Benzaldehyde
4-Chlorobenzaldehyde
Benzaldehyde
4-Chlorobenzaldehyde
Benzaldehyde
4-Chlorobenzaldehyde
Benzaldehyde
4-Chlorobenzaldehyde
Benzaldehyde
4-Chlorobenzaldehyde
Benzaldehyde
4-Chlorobenzaldehyde
Benzaldehyde
4-Chlorobenzaldehyde
Benzaldehyde
4-Chlorobenzaldehyde
Benzaldehyde
38
39
42
43
45
43
49
55
60
68
73
79
70
76
68
69
62
64
78
77
85
87
92
96
2
4
4
CoFe O
2
NaP Zeolite/CoFe O (1:1)
NaP Zeolite/CoFe O (1:1)
NaP Zeolite/CoFe O (1:2)
NaP Zeolite/CoFe O (1:2)
NaP Zeolite/CoFe O (1:3)
NaP Zeolite/CoFe O (1:3)
NaP Zeolite/CoFe O (1:4)
NaP Zeolite/CoFe O (1:4)
NaP Zeolite/CoFe O (1:4)
NaP Zeolite/CoFe O (1:4)
NaP Zeolite/CoFe O (1:4)
NaP Zeolite/CoFe O (1:4)
NaP Zeolite/CoFe O /Am-Py (1:1)
NaP Zeolite/CoFe O /Am-Py (1:1)
NaP Zeolite/CoFe O /Am-Py (1:2)
NaP Zeolite/CoFe O /Am-Py (1:2)
2
4
2
4
2
4
2
4
2
4
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
2
4
2
4
2
4
2
4
2
2
2
CH Cl
2
4
2
EtOH
EtOH
2
4
2
4
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
2
4
2
4
2
4
2
4
NaP Zeolite/CoFe O /Am-Py (1:3)
NaP Zeolite/CoFe O /Am-Py (1:3)
NaP Zeolite/CoFe O /Am-Py (1:4)
NaP Zeolite/CoFe O /Am-Py (1:4)
2
4
2
4
2
4
4-Chlorobenzaldehyde
2
4
1
3

Z. Mortezaei et al.
4
-Chlorobenzaldehyde
Benzaldehyde
100
90
80
70
60
50
40
30
20
10
0
5
10
20
30
5
10
20
30
NaP Zeolite/CoFe O
NaP Zeolite/CoFe O /Am-Py
2
4
2
4
Catalyst (mg)
Fig. 9 The eꢀect of amounts for NaP Zeolite/CoFe O and NaP Zeolite/CoFe O /Am-Py catalyst (ratio
2
4
2
4
1
:4) in aldol condensation reaction at room temperature and 16 h
Zeolite produced relatively low yields (entries 1–4) and with decreasing the ratio of
NaP Zeolite/CoFe O , the yield was increased (entries 5–12 and 17–24). The pres-
2
4
ence of aminopyridine moieties has a good eꢀect on the yield (entries 17–24). It
seems, with introducing the basic amine groups on NaP Zeolite/CoFe O nanocom-
2
4
posite, an acid–base catalyst was created which is useful for aldol condensation. One
of the eꢀective factors in the progress of reaction is the amount of catalyst (Fig. 9)
because the result shows that for lower catalyst amount, the lower yield was obtained
which conꢁrms the higher amounts of acid and base site in the cavities and surface
of catalyst is useful for the reaction. Furthermore, the reaction had no signiꢁcant
change in the yield of reactions for nonpolar solvent (entries 13 and 14), but with
using of polar solvents such as ethanol, the yield of reaction was reduced (entries
1
5 and 16) which may be due to strong interaction between solvent (through oxygen
atoms) and acid–base sites of the catalyst [55]. So, the prepared hybrid catalysts
show high eꢂciency at room temperature and easy work-up in which the separation
techniques are not necessary to get the pure compounds. To consider the eꢀect of
temperature and time on the yield of the reaction, aldol condensation was studied
at 50 °C and 12 h time. The result showed that the yield of the reaction for NaP
Zeolite/CoFe O and NaP Zeolite/CoFe O /Am-Py had small increase (about 2–3%)
2
4
2
4
with temperature rising and also the yield was decreased about 10% with reduction
in reaction time, which conꢁrm that the reaction follows from Arrhenius equation
[
55]. The proposed mechanism is shown in Scheme 2.
Selected spectroscopic data
−
1
1
2
(
,6‑Di(benzylidene)cyclohexan‑1‑one m.p. 117 °C; FT-IR (KBr, cm ): 1583
C=C), 1677 (C=O), 2982 (C–H Aliphatic), 3055 (C–H Aromatic); H-NMR
1
3

Synthesis and characterization of functionalized NaP…
Scheme 2 The plausible mechanism for the Crossed-Aldol condensation in the presence of NaP Zeolite/
CoFe O /Am-Py (1:4) as a heterogeneous catalyst
2
4
(
400 MHz, CDCl , δppm): 1.79 (m, 2H, HAliph.), 2.93 (m, 4H, HAliph.), 7.33-7.46 (m,
3
1
0H, H
), 7.80 (s, 2H, H
).
Arom.
Oleꢁn.
2
,6‑Bis(4‑chlorobenzylidene)cyclohexan‑1‑one m.p. 147–148 °C; FT-IR (KBr,
−1
cm ): 1600 (C=C), 1660 (C=O), 2914 (C–H Aliphatic), 2938 (C–H Aromatic);
1
H-NMR (400 MHz, CDCl , δppm): 1.80 (m, 2H, H
), 2.88 (m, 4H, H
),
Aliph.
3
Aliph.
7
.38 (m, 8H, H
), 7.72 (s, 2H, H
).
Arom.
Oleꢁn.
Biomass is a new organic source for energy industry. Some aldol condensation reac-
tions such as condensation of furfural and acetone produce an intermediate which
can be used for preparation of short chain biomass derivatives [25]. Literature
survey revealed that aldol condensation between furfural and acetone was formed
FAcOH (4-(2-furyl)-4-hydroxy-butan-2-one) as a primary condensation product;
this intermediate compound subsequently dehydrated into the aldol product FAc
(
Table 6) and then it can be reacted with another furfural molecule to produce the
aldol dimer product F Ac. Firstly, NaP Zeolite and CoFe O nanoparticles were
2
2
4
used as catalysts for aldol reaction (entries 1–2), but small conversion was found at
1
3

Z. Mortezaei et al.
Table 6 Aldol condensation of furfural with acetone over catalysts. Reaction conditions: 20 mg catalyst,
Furfural (0.01 mol), Acetone (0.1 mol), temperature (100 °C) and reaction time (2 h)
Selectivity (%)
Furfural conversion (%)
Catalyst
Entry
FAc
Selectivity (%)
F2Ac
1
2
3
4
5
6
7
8
9
NaP Zeolite
CoFe O
NaP Zeolite/CoFe O (1:1)
NaP Zeolite/CoFe O (1:2)
NaP Zeolite/CoFe O (1:3)
NaP Zeolite/CoFe O (1:4)
NaP Zeolite/CoFe O /Am-Py (1:1)
NaP Zeolite/CoFe O /Am-Py (1:2)
NaP Zeolite/CoFe O /Am-Py (1:3)
36.5
55.9
67.9
80.4
89.8
96.1
69.2
83.4
92.3
97.9
71.1
78.3
81.7
84.3
87.8
89.8
83.9
85.7
88.6
92.3
15.3
12.3
11.1
9.7
7.7
6.1
11.6
10.0
8.2
2
4
2
4
2
4
2
4
2
4
2
4
2
4
2
4
1
0
NaP Zeolite/CoFe O /Am-Py (1:4)
6.7
2
4
reaction conditions. The furfural conversion was increased with decreasing the ratio
of NaP Zeolite/CoFe O for pure and functionalized catalyst (entries 3–6 and 7–10).
2
4
During the reaction, F Ac as a product was detected, but the maximum selectiv-
2
ity in preparation of F Ac (11.61%) was achieved at maximum furfural conversion
2
(
Table 6, entry 7). It seems the size of cavities in the micro-/meso-catalyst (NaP
Zeolite/CoFe O and NaP Zeolite/CoFe O /Am-Py) is suitable for the production of
2
4
2
4
FAc, because previous studies showed that the size of aldol adduct, F Ac, is up to
2
1
.4 nm and highly non-spherical [24]. According to the BJH, micropores distribu-
tions for NaP Zeolite/CoFe O and NaP Zeolite/CoFe O /Am-Py (Fig. 3) are less
2
4
2
4
than 1.4 nm; therefore, the catalyst can be prevented from the second condensa-
tion steps between furfural and FAc to form F Ac [19]. Although, with introducing
2
amino pyridine to the NaP Zeolite/CoFe O , the selectivity for preparation of F Ac
2
4
2
was increased which conꢁrms the eꢀect of basic sites for construction of F Ac,
2
2
functional groups may also prevent the formation of the large sized molecule F AC,
so small yield increase in F Ac was observed [25, 56].
2
To consider the eꢀect of molar ratio between furfural and acetone, three ratios
(
1:10, 1:5 and 1:2) were used (Fig. 10). The results show that the conversion
of furfural increased about 7% and the selectivity of F Ac decreased 2% with
2
decreasing the ratio of furfural/acetone. L. Faba and co-workers reported that the
separation of proton from acetone and forming the carbon anion intermediate is
the rate determining step for the aldol condensation of furfural and acetone, then
with decreasing the acetone in the reaction mixture, the interaction between the
catalyst and acetone reduced, and the furfural conversion was decreased [57]. The
1
3

Synthesis and characterization of functionalized NaP…
Furfural conversion
Selectivity to FAc
Selectivity to F2Ac
100
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
0
1
. 10
1 . 5
1 . 2
1 . 10
1 . 5
1 . 2
NaP Zeolite/CoFe O4
NaP Zeolite/CoFe O /Am-Py
2
2
4
Molar ration (F. Ac)
Fig. 10 The eꢀect of molar ratio between furfural and acetone (1:10, 1:5 and 1:2) in aldol condensation
with 20 mg catalyst, 2 h reaction time at 100 °C
Furfural conversion
Selectivity to FAc
Selectivity to F2Ac
100
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
0
6
0 °C 80 °C 100 °C 120 °C
60 °C 80 °C 100 °C 120 °C
NaP Zeolite/CoFe O
NaP Zeolite/CoFe O /Am-Py
2
4
2
4
Temperature
Fig. 11 The eꢀect of temperature on catalytic activity in aldol condensation of furfural and acetone with
h and 20 mg catalyst
2
eꢀect of temperature was investigated on reaction time on (2 h) at T= 60, 80, 100
and 120 °C (Fig. 11) which results show that the furfural conversion increased
with increasing temperature and selectivity remains at very low changing. These
results are in agreement with previous studies that show high furfural conversion,
and the selectivity to aldol products in aldol condensation can be achieved by
high reaction temperature [18, 58]. Also, the result of GC analysis indicated the
1
3

Z. Mortezaei et al.
Scheme 3 The proposed mechanism for production of FAc as a biomass derivative in the presence of
NaP Zeolite/CoFe O /Am-Py as a shape selective catalyst
2
4
presence of FAcOH during the reaction, which conꢁrms the proposed mechanism
in Scheme 3.
Also, the catalytic activity comparison of NaP Zeolite/CoFe O /Am-Py(1:4) with
2
4
other reported heterogeneous catalysts for aldol condensation of furfural and acetone
which produce FAc and F Ac shows in this work the condition of reaction (amount
2
of catalyst, yields, time and temperature of reaction) is very mild and ecofriendly
due to solvent-free condition (Table 7) [18, 25, 59–64].
Recycling ability of the catalyst
The catalytic recycling experiments were also conducted on NaP Zeolite/CoFe O
2
4
and NaP Zeolite/CoFe O /Am-Py, and the results are shown in Fig. 12. After ꢁrst run
2
4
the catalysts separated with a magnet and solid powder was washed thoroughly with
dichloromethane and ethanol and then dried in vacuum condition and used for the
next 4 runs. The results show that the yields reduced about 5–7% in each run. It seems
this eꢀect is due to lower decreasing in saturation magnetization and coercivity factor
1
3

Synthesis and characterization of functionalized NaP…
Table 7 Comparison of catalytic activity of NaP Zeolite/CoFe O /Am-Py (1:4) with other reported het-
2
4
erogeneous catalysts
Catalyst (amount of cat. g)
Temp. (°C)
Time (min)
Furfural Con- Selectivity (%)
version (%)
Ref.
FAC
F2AC
MgO-ZrO (0.5)
100
100
85
50
50
100
100
100
100
100
100
100
180
120
480
1440
1440
120
240
240
120
44.1
120
120
70.0
95.0
99.6
96.5
98.4
38.5
26.2
29.0
8.3
45.0
90.0
42.2
90.0
14.7
79.5
71.0
83.0
96.4
35.0
90.3
92.3
10.0
–
57.1
–
61.5
3.7
20.0
5.5
[59]
[60]
[61]
[62]
[62]
[18]
[63]
[63]
[25]
[25]
[64]
–
2
HTC (Mg/Al:3) (2)
MgO/NaY (1.06)
Mg-Zr/HSAG (0.5)
Mg-Zr Oxide (0.5)
HBEA-25 (2)
Fe-BTC (1)
BEA (1)
K-IE-Y-2.5 (2)
1.5
17.0
4.0
K-IMP-Y-15 (2)
K-PVA-10% (0.25)
NaP Zeolite/CoFe O /
35.0
96.4
97.9
6.75
2
4
Am-Py(1:4) (0.02)
Furfural conversion
Selectivity to FAc
Selectivity to F2Ac
100
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
0
Run 1 Run 2 Run 3 Run 4
Run 1 Run 2 Run 3 Run 4
NaP Zeolite/CoFe O /Am-Py
NaP Zeolite/CoFe O4
2
2
4
Fig. 12 The catalytic recycling results of NaP Zeolite/CoFe O and NaP Zeolite/CoFe O /Am-Py (ratio
2
4
2
4
1
:4)
1
3

Z. Mortezaei et al.
Fig. 13 The XRD patterns of NaP Zeolite/CoFe O (1:4) as a fresh catalyst (a) and after 4 runs using as
2
4
a catalyst for aldol condensation reactions for (b) cyclohexanone with benzaldehyde, (c) cyclohexanone
with 4-Cl-benzaldehyde and (d) furfural and acetone
respect to other works which is an important parameter for reuse during the organic
reaction [65, 66].
The result shows that the yield of the reactions reduces about 5–7% in each run
(
Fig. 13). Figure 13a–d shows the XRD patterns of fresh and reused catalyst [NaP Zeo-
lite/CoFe O (1:4)] in aldol condensation reactions. Figure 13b, c is related to the reac-
2
4
tion of cyclohexanone with benzaldehyde and with 4-Cl-benzaldehyde, respectively.
Also, Fig. 13d shows the XRD pattern of reused catalyst [NaP Zeolite/CoFe O (1:4)]
2
4
in aldol condensation of furfural and acetone. The obtained XRD patterns show that the
structure of catalyst after ꢁnal runs has not changed and is the same as fresh catalyst.
1
3

Synthesis and characterization of functionalized NaP…
Conclusion
The CoFe O nanoparticles, with uniformly distributed 40 nm size, with diꢀerent
2
4
ratios introduced to gel of zeolite and under hydrothermal condition a micro–meso-
structures of zeolite, were prepared. Then, the NaP Zeolite/CoFe O nanostructure
2
4
functionalized with 2-aminopyridine tags as a basic organic moiety. The structure
of hybrid nanostructure (NaP Zeolite/CoFe O /Am-Py) was conꢁrmed by FT-IR,
2
4
XRD, BET, VSM, TG, SEM and TEM techniques. In the second step, the catalytic
properties of prepared materials were investigated by two sets of aldol condensation
reaction as follow:
1
. In crossed-aldol condensation of cyclohexanone with aromatic aldehydes, the
products yields were higher than pure zeolite and CoFe O and also with intro-
2
4
ducing aminopyridine to inorganic support; the yield of reaction was increased.
2
. The condensation of furfural with acetone in the presence of prepared micro–
meso-nanomaterial produced FAc in high yield while F Ac was a side product.
2
These results conꢁrm that the size of micro–meso-structure cavities is appropriate
for small molecules. Besides, the conversion and shape selectivity is aꢀected with
the change in the molar ratio of furfural: acetone and reaction temperature.
So, it seems both acidic and basic sites are eꢀective on aldol condensation
reactions. The prepared hybrid catalyst was easily separated and reused several
times without signiꢁcant loss of its activity. The presented catalysts can be used
at mild conditions and have potential for industrial application as heterogeneous
catalysts.
Acknowledgements Thanks to the Iranian Nanotechnology Innovation Council and the Research Council
of Arak University and Center of Excellence in the Chemistry Department of Arak University for sup-
porting of this work.
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