Synthesis and characterization of an acidic nanostructure based on magnetic polyvinyl alcohol as an efficient heterogeneous nanocatalyst for the synthesis of α-aminonitriles

Article abstract of DOI:10.1016/j.jorganchem.2018.12.002

The present study described design, preparation and characterization of a new magnetic nanocomposite based on polyvinyl alcohol (PVA) as a non-toxic, water-soluble, high mechanical stable and low-cost polymer. Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM) image, transmission electron microscope (TEM) image, X-ray diffraction (XRD) pattern, energy-dispersive X-ray (EDX) analysis and thermogravimetric (TG) analysis were used to describe the morphological, chemical and physical properties of the prepared nanocatalyst. All these results confirmed the successful synthesis of Fe₃O₄@PVA-SO₃H. This heterogeneous nanocatalyst was then successfully used for the synthesis of α-aminonitrile derivatives by starting from an aldehyde, an aniline and trimethylsilyl cyanide (TMSCN). High efficiency, green chemistry properties, simple and easy separation are the specific properties of this nanocomposite. Fe₃O₄@PVA-SO₃H can be derived out by an external magnet and reused ten times without any changes in its structure.

Full text of DOI:10.1016/j.jorganchem.2018.12.002

Accepted Manuscript
Synthesis and characterization of an acidic nanostructure based on magnetic
polyvinyl alcohol as an efficient heterogeneous nanocatalyst for the synthesis of α-
aminonitriles
Ali Maleki, Jamal Rahimi, Zoleikha Hajizadeh, Maryam Niksefat
PII:
S0022-328X(18)30948-3
DOI:
https://doi.org/10.1016/j.jorganchem.2018.12.002
JOM 20659
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 29 October 2018
Revised Date: 27 November 2018
Accepted Date: 3 December 2018
Please cite this article as: A. Maleki, J. Rahimi, Z. Hajizadeh, M. Niksefat, Synthesis and
characterization of an acidic nanostructure based on magnetic polyvinyl alcohol as an efficient
heterogeneous nanocatalyst for the synthesis of α-aminonitriles, Journal of Organometallic Chemistry
(2019), doi: https://doi.org/10.1016/j.jorganchem.2018.12.002.
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ACCEPTED MANUSCRIPT
Graphical Abstract
OSO3H
O
OSO3H
OSO3H
O
O
O
FeCl3.6H2O
FeCl2.4H2O
ClSO3H
Fe3O4
O
Fe3O4
Fe3O4
Fe3O4
O
O
O
PVA
OSO3H
H2N
OSO3H
OSO3H
Fe3O4@PVA-SO3H
Fe3O4@PVA
Fe3O4
R2
R
PVA
N
SO3H
NH
N
HN
R
O
H
R
NH
TMSCN
R
N

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Synthesis and characterization of an acidic nanostructure based on magnetic
polyvinyl alcohol as an efficient heterogeneous nanocatalyst for the synthesis
of α-aminonitriles
Ali Maleki*, Jamal Rahimi, Zoleikha Hajizadeh, Maryam Niksefat
Catalysts and Organic Synthesis Research Laboratory, Department of Chemistry, Iran
University of Science and Technology, Tehran 16846-13114, Iran
*Corresponding author E-mail: maleki@iust.ac.ir; Fax: +98-21-73021584; Tel: +98-21-
77240540-50
Abstract
The present study described design, preparation and characterization of a new magnetic
nanocomposite based on polyvinyl alcohol (PVA) as a non-toxic, water-soluble, high mechanical
stable and low-cost polymer. Fourier transform infrared (FT-IR) spectroscopy, field-emission
scanning electron microscopy (FE-SEM) image, transmission electron microscope (TEM) image,
X-ray diffraction (XRD) pattern, energy-dispersive X-ray (EDX) analysis and thermogravimetric
(TG) analysis were used to describe the morphological, chemical and physical properties of the
prepared nanocatalyst. All these results confirmed the successful synthesis of Fe3O4@PVA-
SO3H. This heterogeneous nanocatalyst was then successfully used for the synthesis of α-
aminonitrile derivatives by starting from an aldehyde, an aniline and trimethylsilyl cyanide
(TMSCN). High efficiency, green chemistry properties, simple and easy separation are the
specific properties of this nanocomposite. Fe3O4@PVA-SO3H can be derived out by an external
magnet and reused ten times without any changes in its structure.
Keywords: Polyvinyl alcohol; Nanocomposite; Magnetic nanocatalyst; Sulfonic acid; ꢀ-
Aminonitrile; Green chemistry.
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1. Introduction
By looking more closely at the needs of industry, developing new catalysts based on green
chemistry principals is urgently needed. Nowadays, nanomaterials have been exhibited
significant advantages and features due to their large surface-to-volume ratio [1-15]. The
difficulty of separating nanocatalyst from reaction media extremely limits their applications in
industry. To conquer this drawback in the last decade's magnetic nanoparticles (MNPs) gained
considerable attention [16]. Among the magnetic nanoparticles, Fe3O4 nanoparticles have been
recognized the most widely used due to its properties such as low cost, relative high magnetic
saturation, and easy preparation [17]. To prevent agglomeration and oxidation of Fe3O4 NPs
coating with organic and inorganic materials including small molecules, silica, polymers, carbon,
metal or metal oxide NPs is urgently needed [18, 19]. Also, the coating procedures provide
reaction sites or active groups for covalently or no covalently grafting the active catalytic units
onto the coated MNPs to construct magnetically recoverable catalysts.
PVA can be used as a high performance polymer because of the unique combination of
beneficial properties such as non-toxicity, water-solubility, biocompatibility, biodegradability,
low cost and high mechanical efficiency [20]. Its high hydrophilicity and high surface –OH
groups lead to easy modification by different nanoparticles and can decrease the aggregation
process [21]. The effective immobilization of the Fe3O4 inside the PVA was achieved by their
bonding with the exposed hydroxyl groups in PVA.
There are several protocols reported in the literature for synthesizing Fe3O4/PVA
nanocomposites such as in situ [22], ex-situ methods [23], and sonochemical method [24]. The
reported methods have their own advantages and disadvantages but, the in situ method gives
more homogenate composite in relatively short time. The application of this nanocomposite has
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been investigated in many different fields such as in drug delivery [25], as membranes for bone
regeneration [26], as magneto-thermal for hyperthermia in cancer [25], an enzyme carrier [27]
and biomedical application [28].
Recently, due to high reactivity, operational simplicity, low toxicity, non-corrosive nature and
recoverable properties heterogeneous acid catalysts are found as an effective catalyst for the
organic reactions [29-30]. The three-component synthesis of α-aminonitriles via Strecker
reaction was carried out by the combination of aldehydes, amines and TMSCN. Aminonitriles
are versatile intermediates for the synthesis of amino acids via hydrolysis of the nitrile moiety
[31]. Many methods have been developed for the synthesis of aminonitriles by use of acid
catalysts such as InCl3 [32], BiCl3 [33] and CoCl2 [34].
In continuation of last research on green nanocatalyst and organic synthesis [35, 36], herein, the
synthesis and characterization of Fe3O4@PVA-SO3H nanocomposite were investigated for the
first time and its application as a nanocatalyst was examined in the synthesis of aminonitriles via
Strecker reaction (Scheme1).
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Scheme 1. Preparation of Fe3O4@PVA-SO3H and catalytic application in the α-aminonitrile
derivatives.
2. Experimental
2.1. General
All the solvents, reagents, and chemicals were purchased from Merck, Fluka and Aldrich. FT-IR
spectra were recorded on a Shimadzu IR-470 spectrometer by the method of KBr pellets.
Melting points were measured on an Electrothermal 9100 apparatus and are uncorrected. Field-
emission scanning electron microscopy (FE-SEM) images were taken with KYKY-
EM3200. Transmission electron microscope (TEM) image was obtained by Philips CM120. X-
ray (EDX) analysis was recorded with a Numerix DXP–X10P. Thermal analysis was taken by
Bahr-STA 504 instrument in the air atmosphere. XRD patterns of the solid powders were carried
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out using a JEOL JDX–8030 (30 kV, 20 mA). The products were identified by comparison of
their spectroscopic and analytical data with those of authentic samples.
2.2. Preparation of Fe3O4@PVA nanocomposite
Fe3O4@PVA nanoparticles were synthesized by co-precipitation method. At first, 2.0 g of PVA
72000 Mw was dissolved in 40 mL water at 80 ºC for 6 h to achieve homogenous mixture. The
homogenous PVA was mixed with 12 mL of NH3.H2O in a three-necked flask under nitrogen
(N2) atmosphere. Then, 2.5 g of FeCl3.6H2O and 1.0 g of FeCl2.4H2O were dissolved in 10 mL
of deionized water. The mixture of FeCl3.6H2O and FeCl2.4H2O was added slowly to the NH3-
PVA solution and the mixture heated at 60 °C for 120 min. The obtained Fe3O4@PVA
precipitate was washed with deionized water until pH was reached to 7. Finally, it was dried at
80 ºC in an oven.
2.3. Preparation of Fe3O4@PVA-SO3H nanoparticles
Functionalizing of prepared Fe3O4@PVA nanocomposite with SO3H, was done by using a
suction flask equipped with a constant-pressure dropping funnel and a gas inlet tube for
conducting HCl gas over an absorbing solution (i.e., water), charged with the Fe3O4@PVA (0.5
g) in CH2Cl2 (20 mL) and dispersed by an ultrasonic bath for 30 min. Then, a solution of
chlorosulfonic acid (0.25 mL) in CH2Cl2 (5 mL) was added dropwise at -10 ºC during 30 min.
After the addition was completed, the mixture was stirred for 90 min until HCl was fetched up
completely. A powder of nano-Fe3O4@PVA-SO3H was obtained. The nanocomposite was
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filtered and washed several times with dry CH2Cl2, methanol and distilled water. The precipitate
was dried under vacuum at 70 °C.
2.4. General procedure for the synthesis of 2-(N-anilino)-2-phenyl acetonitrile 4a-z
The Mixture of benzaldehyde (0.107 g, 1 mmol), aniline (0.093 g, 1 mmol) and TMSCN (0.120
g, 1.2 mmol) in 3 mL of EtOH was stirred for 10 min at ambient temperature in the presence of
Fe3O4@PVA-SO3H nanocomposite (0.050 g). The completion of the reaction was monitored by
TLC (ethyl acetate–n-hexane, 1:3). Catalyst was separated easily by an external magnet. The
pure crystalline products were achieved from the reaction mixture by recrystallization in hot
EtOH.
3. Results and discussion
In this work, Fe3O4@PVA-SO3H heterogeneous acidic nanocatalyst was synthesized for the first
time under mild conditions and short reaction times. As can be seen in Scheme 1, Fe3O4@PVA-
SO3H nanocatalyst was prepared after two steps. At first, Fe3O4@PVA nanoparticles were
synthesized by co-precipitation method in presence of PVA and solution of FeCl3.6H2O and
FeCl2.4H2O under N2. After that, Fe3O4@PVA was treated by chlorosulfonic acid to synthesize
Fe3O4@PVA-SO3H nanocatalyst. Various methods have been used to confirm synthesis the
nanocomposite. FT-IR spectra for confirming the incorporation of SO3H onto Fe3O4@PVA,
Energy-dispersive X-ray (EDX) for the elemental analysis, The field emission scanning electron
microscopy (FE-SEM) for morphology and the size details of synthesized nanocomposite, X-ray
diffraction (XRD) for crystalline phases of Fe3O4@PVA-SO3H and The thermogravimetric
analysis (TGA) for thermal stability, which are discussed as follow.
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3.1. Characterization of the nanocomposite
3.1.1. FT-IR Analysis
FT-IR spectroscopy, Fig. 1, confirmed the formation of the nanocomposite. The bending
vibration band of Fe–O appeared at 584 cm-1. The O–H stretch of Fe3O4 and PVA appeared
around 3400, and confirm the presence of a great number of PVA hydroxyl functional groups
that can be easy modified by SO3H groups. Stretching vibration band at 2923 is regarding to C–
H of PVA [37]. The S-O stretching vibrations of SO3H groups in Fe3O4-PVA-SO3H
nanocomposite on Fe3O4@PVA surface appeared at 1124 cm−1 that indicated the synthesis of
Fe3O4@PVA-SO3H [38]. Finally, as can be seen, we have characterized the recycled
nanocatalyst by FT-IR spectroscopy which showed suitable retention of its structure and there
was no considerable deformation or leaching after ten times reusing.
Fig. 1. The FT-IR spectra of Fe3O4@PVA, Fe3O4
Fe3O4 PVA-SO3H
@PVA-SO3H and the recycled
@
.
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3.1.2. Energy-dispersive X-ray (EDX)
The EDX elemental analysis of the Fe3O4@PVA-SO3H MNPs was shown in Fig. 2. This
analysis strongly clarifies that the SO3H groups were successfully incorporated onto the
magnetic PVA. It approved the presence of carbon, oxygen and sulfur elements in the
nanocomposite and confirmed the purity of the nanocomposite.
Fig. 2. The EDX analysis of the Fe3O4@PVA-SO3H nanocomposite.
3.1.3. Field-emission scanning electron microscopy (FE-SEM)
The FE-SEM images of the outer surface of the Fe3O4@PVA-SO3H nanocomposite is illustrated
in Fig. 3. A close examination of the figure revealed that the iron oxide impregnated in the
polymer matrix and embedded in a sponge-like PVA matrix also, The Fe3O4 nanoparticles
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exhibit cubic structure. Furthermore, iron oxide particles show the uniform size of nanometer
dimensions with the range of average diameter 40.27± 6 nm.
Fig. 3. The FE-SEM image of Fe3O4@PVA-SO3H nanocomposite.
3.1.4. Transmission electron microscope (TEM)
TEM image micrograph of Fe3O4@PVA-SO3H nanocomposite was illustrated in Fig. 4. It
clearly shows considerable exfoliation of PVA after functionalized by Fe3O4 and SO3H by nearly
monodisperse in gray colour. This analysis completely can confirm the successful synthesis of
the nanocomposite.
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Fig. 4. The TEM image of Fe3O4@PVA-SO3H nanocomposite.
3.1.5. Thermogravimetric analysis (TGA)
The thermogravimetric analysis (TGA) curve, display the relation between temperature and
weight loss of the nanocatalysts (Fig. 5). Decomposition of the nanocomposite was achieved
while heating at a rate of 10 °C/min in the air between 20 °C and 800 °C. As can be seen, the
weight loss in the temperature range from 50 to 150 °C is related to the removal of the surface
adsorbed water and weakly absorbed impurities. For the Fe3O4@PVA-SO3H, the new weight
loss about 40% in the temperature range of 200–550 °C assigned to the decomposition of PVA
and SO3H groups. Moreover, can be seen that the nanocomposite has a higher thermal stability
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compared to PVA alone that is decomposition at about 250 °C [39]. This result shows the strong
interaction in the nanocomposite.
Fig. 5. The TGA curve of Fe3O4/PVA-SO3H nanocomposite.
3.1.6. X-ray diffraction (XRD)
XRD measurement is used to determine crystalline nature of nanocomposite. Fig. 6 shows the X-
ray diffraction patterns of Fe3O4@PVA-SO3H and confirm the presence of Fe3O4 NPs on PVA.
The broad diffraction peak around 2θ = 20 corresponds to PVA [40]. All of the observed peaks
for the Fe3O4 are in perfect match with the characteristic data of magnetite iron oxide (JCPDS
card No. 01-075-0449). The crystalline peaks of magnetite iron oxide with cubic structure
observed at the diffraction angles (2θ) of 18.59, 30.53, 35.86, 37.53, 43.54, 54.13, 57.55, and
63.31. Peak broadening and peak high lowering of Fe3O4 are due to the grafting of nanoparticles
on the surface of the PVA with amorphous nature. Furthermore, the particle size of Fe3O4/PVA-
SO3H nanocomposite was calculated by Debye–Scherrer equation. As
the average crystallite size was around 28 nm.
a
result,
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Fig. 6. The XRD pattern of: (a) Fe3O4@PVA-SO3H nanocomposite, (b) the reference Fe3O4.
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3.1.7. Vibrating sample magnetometer (VSM)
VSM analysis was applied at room temperature to measure magnetic properties (Fig. 7). The
saturation magnetization values of Fe3O4@PVA and Fe3O4@PVA-SO3H nanocomposite were
around 32.95 and 24.15 emu g-1. The decrease of the saturation magnetization of Fe3O4@PVA
after loading to the SO3H groups confirmed the successful synthesis of the nanocomposite.
Moreover, the both of Fe3O4@PVA and Fe3O4@PVA-SO3H show an acceptable magnetic
property.
Fig. 7. The VSM curves of Fe3O4@PVA and Fe3O4@PVA-SO3H nanocomposite.
3.1.8. Back titration of Fe3O4@PVA-SO3H in aqueous media
Acidity ([H+]) of the synthesized Fe3O4@PVA-SO3H nanocatalyst was achieved by the back
titration method. At first, 0.5 g of Fe3O4@PVA-SO3H, 0.5 g of NaCl, and 10 mL of NaOH 0.1 M
were added to 35 mL of distilled water and stirred with a magnet for 24 h. After that, a few drops
of phenolphthalein were supplemented into the mixture and the colour changed to pink. Finally,
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the mixture was titrated by the solution of HCl 0.1 M to reach the neutral pH. Accordingly, the
pH of the nanocatalyst was calculated 1.61.
3.2. Application of the nanocatalyst in organic synthetic reaction
In this work, α-aminonitrile derivatives were synthesized by the reaction of different aromatic
aldehydes with aniline and TMSCN in the presence of Fe3O4@PVA-SO3H as a recoverable
magnetic nanocatalyst in ethanol at room temperature. The work-up procedure of the product
was easy as the nanocatalyst can be separated simply by an external magnet. To optimize the
reaction conditions, a series of experiments were performed with the variation of different
reaction parameters such as solvent and amount of catalyst for a representative condensation of
4-chlorobenzaldehyde (1 mmol), aniline (1 mmol) and TMSCN (1.2 mmol) as the model
reaction. The results are summarized in Table 1. Fe3O4 NPs and Fe3O4@PVA are able to produce
relatively low yields in EtOH, but, in the presence of Fe3O4@PVA-SO3H nanocomposite, the
yield of the product increased to 99 % (Table 1, entry 5). The model reaction was also studied in
various solvents such as H2O, EtOH, EtOAc, and CHCl3. The best result was achieved in EtOH.
Also, different amount of the catalyst was investigated. As can be seen in Table 1, entry 5, in the
presence of 50 mg of the catalyst, a significant yield was obtained. While the yield of the desired
product 4b was not significantly improved in presence of excess amount of the catalyst (Table 1,
entries 11 and 12). The best result was obtained by carrying out the reaction at ambient
conditions in ethanol for 10 min using 50 mg of Fe3O4@PVA-SO3H.
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Table 1. Optimization of reaction conditions by reaction of 4-chlorobenzaldehyde, aniline and
TMSCN at room temperature.
Amount of
Temperature
(°C)
Yielda
(%)
Entry
Solvent
Catalyst
catalyst (mg)
1
2
EtOH
EtOH
Fe3O4
50
50
50
50
50
50
50
50
20
32
70
100
50
50
r.t.
r.t.
50
trace
35
47
96
55
56
45
53
60
96
96
35
40
PVA
3
EtOH
Fe3O4@ PVA
r.t.
4
H2O
Fe3O4@PVA-SO3H
Fe3O4@PVA-SO3H
Fe3O4@PVA-SO3H
Fe3O4@PVA-SO3H
Fe3O4@PVA-SO3H
Fe3O4@PVA-SO3H
Fe3O4@PVA-SO3H
Fe3O4@PVA-SO3H
Fe3O4@PVA-SO3H
Fe3O4@PVA-SO3H
Fe3O4@PVA-SO3H
r.t.
5
EtOH
r.t.
6
EtOAc
CHCl3
Solvent-free
EtOH
r.t.
7
r.t.
8
r.t.
9
r.t.
10
11
12
13
14
EtOH
r.t.
EtOH
r.t.
EtOH
r.t.
EtOH
60
EtOH
Reflux
a Isolated yield.
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In order to demonstrate the repeatability of this strategy, a broad variety of aromatic aldehydes
possessing electron-withdrawing and electron-releasing substitutions, were employed and a
variety of products were synthesized under the optimized conditions at room temperature. The
desirable results of study are shown in Table 2. All the utilized aldehydes supplied the desired
products in high yields and short reaction times.
Table 2. Synthesis of α-aminonitrile derivatives 4a-z in optimal conditions.a
Mp (°C)
Time Yieldb
Entry
1
R1
Phenyl
R2
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Product (min)
(%)
96
97
98
90
90
98
89
91
96
85
89
90
98
96
Obs.
70-83
91-93
Lit.
5
5
73-75 [41]
92-94 [42]
4a
4b
4c
4d
4e
4f
2
4-Chlorophenyl
4-Bromophenyl
3-Nitrophenyl
3
5
102-104 100-101 [41]
4
5
88-90
91-92
86-88
89-90 [41]
91-92 [41]
86-88 [41]
5
4-Methoxylphenyl
4-Nitrophenyl
10
5
6
7
4-Hydroxyphenyl
4-Methylphenyl
4-Fluorophenyl
2-Thienyl–
15
15
5
124-126 124-125 [41]
71-73 70-71 [41]
101-102 99-101 [43]
4g
4h
4i
8
9
10
11
12
13
14
10
10
15
5
97-99
73-75
97–99 [44]
72–74 [44]
4j
2-Furanyl
4k
4l
4-(Dimethylamino)phenyl
4-Cyanophenyl
3,4,5-Trimethoxyphenyl
107-109 107–110 [44]
112-114 113–115 [45]
146-148 147–149[43]
4m
4n
10
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15
H
20
88
114-116 113–115 [45]
135-137 135-137 [41]
4o
4-Hydroxy-3-methoxyphenyl
16
17
18
19
20
21
22
23
24
2-Nitrophenyl
2,6-Dichlorophenyl
Cinnamaldehyde
2-Chlorophenyl
3-Fluorophenyl
Phenyl
H
H
15
15
10
20
5
89
85
95
84
90
97
97
96
92
4p
4q
4r
4s
74-76
75–78 [44]
H
118-120 117-118 [46]
H
69-71
91-93
69-70 [45]
91-92 [47]
H
4t
4-Me
4-Me
4-Me
4-Me
5
106-108 105–107 [45]
87-89 85-87 [43]
4u
4v
4w
4x
4-Chlorophenyl
Cinnamaldehyde
4-Methylphenyl
5
10
10
104-106 103-106 [45]
116-118 116-118 [45]
25
26
4-Nitrophenyl
Phenyl
4-Me
5
97
68
84-86
83-85 [44]
4y
4z
4-NO2
30
128-129 128-129 [48]
a
Reaction conditions: benzaldehyde (1 mmol), aniline (1 mmol) and TMSCN (1.2 mmol) and
Fe3O4@PVA-SO3H composite (0.05 g) at room temperature in 5 mL of ethanol.
b Isolated yield.
3.3. Comparison the efficiency of synthesized nanocatalyst
To investigate the efficiency of Fe3O4@PVA-SO3H catalyst with some other reported works for
the synthesis of α-aminonitrile derivatives, the model reaction of benzaldehyde, aniline and
TMSCN was compared with other previous reports. Most of last reports have disadvantages such
as long time reaction, toxic solvent and low efficiency can be seen in Table 3, the results of the
present work is more reliable than previous ones.
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Table 3. Comparison the efficiency of the synthesized nanocatalyst with other reported works.
Entry
Catalyst
InCl3
Condition
THF/r.t.
Time
6 h
Yield (%)
Ref
[49]
[50]
1
2
75
89
(Bromodimethyl)sulfonium
bromide
CH3CN/r.t.
1 h
3
4
5
6
RuCl3 (20 mol %)
PVP-SO2
CH3CN/r.t.
CH2Cl2/50 οC
CH3CN/r.t.
EtOH/r.t.
20 h
6h
74
86
95
98
[51]
[52]
Fe(ClO4)3
3h
[53]
Fe3O4@PVA-SO3H
5min
This work
3.4. Mechanistic evaluation
A proposed mechanism for the formation of α-aminonitrile derivatives is shown in Scheme 2. In
the first step, carbonyl of aldehyde was activated by Fe3O4@PVA-SO3H catalyst, intermediate I
was formed. Iminium intermediate II was formed by the condensation reaction between
intermediate I and different amines 2 in the presence of the catalyst. according to the literature
[44], the nucleophilic attack of TMSCN into imine yielded the products 4a-z.
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Scheme 2. Proposed mechanism for the synthesis of 4a-z by using Fe3O4@PVA-SO3H
.
3.5. Catalyst recycling
A valuable property for a catalyst is its easy recovery and reusability. Therefore, in order to
further evaluation of the nanocatalyst, after completion of the reaction, the catalyst was separated
with an external magnet, washed with ethanol and water and dried after each run, and then
reused in the next runs under the same ratio of catalyst and other reaction conditions to the model
reaction. The results shows that the catalyst show no considerable reduction in activity within 10
cycles (Fig. 8). Also, recoverability and reusability of the catalyst without any decrease in
catalytic activity after several times show catalyst stability.
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Fig. 8. Recycling diagram of Fe3O4@PVA-SO3H nanocatalyst in the synthesis of 4b.
4. Conclusions
In this research, Fe3O4@PVA-SO3H with particular properties such as eco-friendly, high
efficiency, green chemistry properties, non-expensive and easy separation was prepared in two
steps. PVA with hydroxyl functional groups can be modified by MNPs and SO3H groups. The
nanocomposite was characterized by FT-IR, EDX, FE-SEM, XRD, TEM and TGA analyses. The
FT-IR spectra demonstrated that SO3H groups were successfully grafted onto the Fe3O4@PVA
nanocomposite. The two major stages of degradation, corresponding to physical absorption and
the organic phase of PVA and SO3H were clearly displayed in TGA analysis. Also, XRD pattern
and FE-SEM images supported the FT-IR and TGA results and confirmed the preparation of the
nanocomposite. This efficient nanocomposite was also applied as a novel nanocatalyst for the
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synthesis of an important α-aminonitrile derivatives in high yields. The nanocatalyst was derived
out by an external magnet and reused ten times with high efficiency. This is the first report on
design, synthesis and characterization of the present nanocomposite and its application as an
efficient catalyst with high reusability and stability.
Acknowledgements
The authors gratefully acknowledge the partial support from the Research Council of the Iran
University of Science and Technology.
Competing interests
None of the authors have any competing or conflict of interests in the manuscript.
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Highlights
• PVA as a high performance polymer was used as non-toxic, water-soluble, high mechanical
and low cost.
• Fe3O4@PVA-SO3H polymer nanocomposite was synthesized successfully under mild
conditions for the first time.
• The new nanocatalyst was employed as an efficient green magnetic nanocomposite catalyst
for the synthesis of α-aminonitriles.
• It was easily separated from the reaction mixture by an external magnet.
• It was recovered and reused without considerable decrease in catalytic activity after ten times.