Pd NPs?Fe3O4/chitosan/pumice hybrid beads: A highly active, magnetically retrievable, and reusable nanocatalyst for cyanation of aryl halides

Article abstract of DOI:10.1016/j.carbpol.2020.116105

In this study, Fe₃O₄/chitosan/pumice hybrid beads were developed as a new stabilizer agent, and palladium nanoparticles (Pd NPs) were successfully decorated on the designed stabilizer without adding any toxic reducing resource. Then, the potential use of Pd NPs?Fe₃O₄/chitosan/pumice hybrid beads as a heterogeneous catalyst against different aryl halide cyanations was investigated with K₄[Fe(CN)₆]. In these reactions, Pd NPs? Fe₃O₄/chitosan /pumice hybrid beads showed high catalytic activity by converting aryl halides to the desired benzonitriles with high product yields (80 %–98 %). Due to the magnetically separable nature of Pd NPs?Fe₃O₄/chitosan/pumice hybrid beads, they were reused several times, and 86 % yield was obtained even after six successive runs. This paper reveals that Pd NPs?Fe₃O₄/chitosan/pumice hybrid beads have a high potential to synthesis a broad range of nitriles due to their excellent catalytic and retrievable capability.

Full text of DOI:10.1016/j.carbpol.2020.116105

Journal Pre-proof
Pd NPs@Fe3O4/chitosan/pumice hybrid beads: A highly active,
magnetically retrievable, and reusable nanocatalyst for cyanation of aryl
halides
Talat Baran
PII:
S0144-8617(20)30279-4
DOI:
https://doi.org/10.1016/j.carbpol.2020.116105
CARP 116105
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Carbohydrate Polymers
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Accepted Date:
17 December 2019
28 February 2020
29 February 2020
Please cite this article as: Baran T, Pd NPs@Fe3O4/chitosan/pumice hybrid beads: A highly
active, magnetically retrievable, and reusable nanocatalyst for cyanation of aryl halides,
Carbohydrate Polymers (2020), doi: https://doi.org/10.1016/j.carbpol.2020.116105
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Pd NPs@Fe3O4/chitosan/pumice hybrid beads: A highly active, magnetically retrievable,
and reusable nanocatalyst for cyanation of aryl halides
Talat Baran
Aksaray University, Faculty of Science and Letters, Department of Chemistry, 68100
Aksaray, Turkey
*Corresponding author:
Address: Department of Chemistry, Faculty of Science and Letters, Aksaray University,
Aksaray, Turkey, 68100
Tel.: +90 382 2882132; fax: +90 382 2882299
E-mail address: talatbaran@aksaray.edu.tr
Graphical Abstract
1

Highlights
 Pd NPs@Fe3O4/chitosan/pumice hybrid beads were characterized by different
techniques
 The nanocatalyst showed good activity against synthesis of benzonitriles
 Pd NPs@Fe3O4/chitosan/pumice hybrid beads reused several times
Abstract
In this study, Fe3O4/chitosan/pumice hybrid beads were developed as a new stabilizer
agent, and palladium nanoparticles (Pd NPs) were successfully decorated on the designed
stabilizer without adding any toxic reducing resource. Then, the potential use of Pd
NPs@Fe3O4/chitosan/pumice hybrid beads as a heterogeneous catalyst against different aryl
halide cyanations was investigated with K4[Fe(CN)6]. In these reactions, Pd NPs@
Fe3O4/chitosan /pumice hybrid beads showed high catalytic activity by converting aryl halides
to the desired benzonitriles with high product yields (80%-98%). Due to the magnetically
separable nature of Pd NPs@Fe3O4/chitosan/pumice hybrid beads, they were reused several
times, and 86% yield was obtained even after six successive runs. This paper reveals that Pd
NPs@Fe3O4/chitosan/pumice hybrid beads have a high potential to synthesis a broad range of
nitriles due to their excellent catalytic and retrievable capability.
Keywords: chitosan; pumice; cyanation reaction; hybrid beads.
2

1. Introduction
Cyanation of aryl halides (Ar-X) play an important role in synthetic or industrial
chemistry because aryl nitriles which are obtained after the cyanation reaction form the key
components of agrochemicals, herbicides, pharmaceuticals, and dyes (Anbarasan, Schareina
& Beller, 2011; Najam et al., 2018; Ren et al., 2011). Moreover, these compounds can be
easily changed into various functional groups, and this property makes them valuable for
different reactions (Chobanian, Fors & Lin, 2006; Veisi, 2019). Therefore, synthesis of
nitriles has recently gained importance (Gazdag, Kunfi & London, 2018; Hemmati,
Sedrpoushan, Soudalizadeh, Khosravi & Hekmati, 2019; Kandathil, Dateer, Sasidhar, Patil &
Patil, 2018a). The most general method for this reaction is Rosenmund-von Braun and
Sandmeyer reactions, but they require a high reaction temperature (˃150ºC) and CuCN
(Anbarasan, Schareina & Beller, 2011; Rosenmund & Struck, 1919; Sandmeyer, 1884).
Therefore, various synthesis methods have been developed for the construction of nitriles, and
metal-catalyzed cyanation reactions with cyanation agents are the most effective and modern
protocols among them (Guobing, Jian & Ling, 2012; Veisi, 2019). Recently, different
transition metal catalysts have been designed and used in the cyanation reactions with
varieties of cyanide resources such as CuSCN, Zn(CN)2, KCN, and NaCN (Cohen &
Buchwald, 2015; Sundermeier, Zapf, Beller & Sans, 2001; Ushkov & Grushin, 2011; Zhang,
Yu, Hu & Cheng, 2013). However, many of them are highly toxic and expensive, and their
uses in the industrial scale applications are generally limited (Veisi, Hemmati & Safarimehr,
2018; Veisi, Tamoradi, Karmakar, Mohammadi & Hemmati, 2019). To overcome these
drawbacks, different metal-catalyzed cyanations of aryl halides were carried out with
K4[Fe(CN)6], which is low-cost and nontoxic cyanide resource (Puthiaraj, Yu, Shim & Ahn,
2019; Schareina et al., 2009). Palladium catalysts have gained more attention compared to
3

other transition metal catalysts due to their high tolerance against different functional groups
and high catalytic performance (Zhang, Yu, Hu & Cheng, 2013; Zheng, Yu & Shen, 2012).
Nowadays, preparation of heterogeneous catalysts has attracted more attention than
homogenous catalysts due to their advantages such as high activity and easy work-up.
Therefore, different heterogeneous catalysts have been prepared using various supports by
researchers (Das & Linert, 2016; Gholinejad & Aminianfar, 2015; Modak, Mondal &
Bhaumik, 2012; Puthiaraj, Yu, Shim & Ahn, 2019). Although heterogeneous catalysts can be
recovered from the reaction media via simple filtration, the loss of the catalyst is inevitable
during these separation techniques in many cases (Baran, Sargın, Kaya, Mulerčikas,
Kazlauskaitė & Menteş, 2018). It negatively effects both the reusability and recoverability of
catalysts. Combination of prepared support or catalyst with magnetic components is the most
effective way to solve this problem as catalysts can be easily recovered from reaction media
via an external magnet due to their magnetic nature (Baran & Nasrollahzadeh, 2019; Chen et
al., 2019). Another important issue in heterogeneous catalytic systems is metal leaching from
catalyst support (Veisi, Ghadermazi & Naderi, 2016; Veisi, Pirhayati & Kakanejadifard,
2017). Therefore, the design of heterogeneous catalysts having a strong interaction with active
metal species is required for catalytic reactions as these catalyst systems can supply some
advantages such as high reusability, easy-work up, and separation of final product from
reaction mixture.
Bio-polymers, which are extracted from natural sources, have outstanding properties
such as being nontoxic, biodegradable, environment-friendly and cheap (Baran, 2019; Veisi,
Ghadermazi & Naderi, 2016). Chitosan is one of the most important biopolymers, and it can
easily be chemically modified as well as being water-compatible in reactions and very
abundant in nature (Dhanavel, Manivannan, Mathivanan, Gupta, Narayanan & Stephen, 2018;
Movassagh & Rezaei, 2015; Xiao, Li & Xia, 2005). Moreover, chitosan has free hydroxyl and
4

amine functional groups on the polymer chains which easily anchor on different transition
metals (Doustkhah, Rostamnia, Gholipour, Zeynizadeh, Baghban & Luque, 2017; Lin, Yu &
Yang, 2005; Molvinger, Quignard, Brunel, Boissière & Devoisselle, 2004). Due to these
characteristics, chitosan and its derivatives serve as ideal stabilizers for production of metallic
nanoparticles (Chen, Xu, Zheng, Guan & Liu, 2018; Jia, Liu, Chen, Guan, Zheng & Liu,
2017; Sin, Yi & Lee, 2010). As an alternative to other stabilizers, pumice is a highly porous,
lightweight, and very low cost volcanic stone (Kitis & Kaplan, 2007; Panuccio, Sorgonà,
Rizzo & Cacco, 2009). Moreover, pumice has a large surface area and microporous structure,
and it is also rich in alumina and silica. These properties make it a good support material for
catalytic reactions (Jonasi, Matina & Guyo, 2017). Thanks to their outstanding properties
above-mentioned, chitosan/pumice composites with magnetic property can be prepared as a
support, which can provide strong interaction with metals to prepare metal nanoparticles.
Then, their catalytic and reusable performance can be evaluated in the different catalytic
reactions. Therefore, this study proposes to prepare a highly active, magnetically retrievable,
and reusable nano-catalyst derived from natural sources for the production of benzonitriles.
In light of our interest in the production of nano-catalysts from the natural sources,
magnetic hybrid beads, which contain chitosan/pumice composites, were prepared as support
(Fe3O4/chitosan/pumice), and palladium nanoparticles were successfully immobilized on the
Fe3O4/chitosan/pumice hybrid beads without the use of any reducing source in this study.
Then, Pd NPs@Fe3O4/chitosan/pumice hybrid beads were utilized as heterogeneous nano-
catalyst in the synthesis of benzonitriles with K4[Fe(CN)6]. Pd NPs@Fe3O4/chitosan/pumice
hybrid beads displayed a good catalytic performance by transforming corresponding
benzonitriles smoothly with 80%–98% yields. Moreover, Fe3O4/chitosan/pumice hybrid beads
were easily recollected from the reaction media via external magnet, and they were reused six
times in the cyanation of p-CH3C6H4I.
5

2. Experimental
2.1. Experimental information
Aryl halides, chitosan, FeSO4·7H2O, FeCl3·6H2O, PdCl2, acetic acid, methanol, DMF,
K2CO3, DMSO, NMP, toluene, Na2CO3, KOH, NaOH, Cs2CO3, K4[Fe(CN)6], and diethyl
ether were purchased from Sigma-Aldrich. Pumice was obtained from Turkey. FT-IR spectra
of Fe3O4/chitosan/pumice hybrid beads and Pd NPs@Fe3O4/chitosan/pumice hybrid beads
were obtained on a Perkin Elmer Spectrum100 FT-IR spectrophotometer. TGA analyses of
Fe3O4/chitosan/pumice hybrid beads and Pd NPs@Fe3O4/chitosan/pumice hybrid beads were
studied by EXSTAR S11 7300 (nitrogen atmosphere; heating range: 30–650 °C). FE-SEM
micrograms and EDS spectra of Fe3O4/chitosan/pumice hybrid beads and Pd
NPs@Fe3O4/chitosan/pumice hybrid beads were obtained by QUANTA-FEG 250ESEM.
XRD patterns of Fe3O4/chitosan/pumice hybrid beads and Pd NPs@Fe3O4/chitosan/pumice
hybrid beads were recorded by Rigaku smart lab system (10–80°). TEM images of Pd
NPs@Fe3O4/chitosan/pumice hybrid beads were recorded by TEM JEOL JEM-2100 (UHR).
Benzonitriles were characterized by GC–MS AgilentGC-7890 A- MS 5975. The 1H NMR and
13C NMR spectra of the benzonitriles were recorded on Agilent 600 MHz spectrometer.
2.2. Synthesis of Fe3O4/chitosan/pumice hybrid beads
1 g of chitosan was added in acetic acid solution (100 mL, 2% by volume) and
dissolved at room temperature. Then, 1 g of pumice was added in the chitosan solution and
stirred until a homogeneous mixture was obtained. Afterwards, 1 g of Fe3O4 particles, which
are prepared in a way similar to our previous studies (Baran & Nasrollahzadeh, 2019), were
introduced into the mixture, and this suspension was stirred overnight. Following this process,
the resulting reaction mixture was dropped in alkaline solution containing
water:methanol:NaOH (water-methanol-NaOH: 60 mL-40 mL-12 g) to acquire gelatinous
6

hybrid beads. Then, gelatinous hybrid beads were cross-linked by stirring with glutaraldehyde
solution at 70 °C for 6h in ethanol. Finally, cross-linked Fe3O4/chitosan/pumice hybrid beads
were collected with external magnet, washed with ethanol, and dried at room temperature.
2.3. Preparation of palladium nanoparticles on Fe3O4/chitosan/pumice hybrid beads
The preparation of palladium nanoparticles without use of any reducing agent was
carried out as follow:
1 g of Fe3O4/chitosan/pumice hybrid beads and 0.2 of PdCl2 were introduced into 30
mL of ethanol, and resulting mixture was refluxed for 4h. It was observed that color of
reaction media turned to black after the reduction of Pd(+2) to Pd(0). Finally, Pd
NPs@Fe3O4/chitosan/pumice hybrid beads were easily collected due to their magnetic nature,
rinsed with water, and dried.
……………………………………Scheme 1………………………….
7

2.4. Typical method for aryl halide cyanation in the presence of catalyst
Aryl halide (1.5 mmol), Na2CO3 (1.8 mmol), K4[Fe(CN)6] (0.2 mmol), Pd
NPs@Fe3O4/chitosan/pumice hybrid beads (0.01 mol %), and DMF (5 mL) were put into a
Schlenk tube and heated at 120 °C for 3h. After the cyanation reaction was completed, the
resulting mixture was filtered. The filtrate was extracted with diethyl ether:water at three
times, and the organic phase dried on MgSO4. Finally, the desired nitriles were obtained by
1
13
evaporation of solvent, and they were sent to GC/MS, H NMR and C NMR analyses for
characterization studies.
3. Results and discussion
3.1. Characterization
FTIR spectrum of Fe3O4/chitosan/pumice hybrid beads is shown in Figure 1a, and that
of Pd NPs@Fe3O4/chitosan/pumice hybrid beads is shown in Figure 1b. FT-IR spectrum of
Fe3O4/chitosan/pumice hybrid beads shows characteristic imine peaks at 1642cm-1. This peak
shows that cross-linked procedure was successfully performed. The presence of a broad peak
at 3331cm-1 can be assigned to stretching of –OH groups of chitosan and pumice. The other
important peaks which are seen in the spectrum of Fe3O4/chitosan/pumice hybrid beads are as
follows: CH stretching: 2921 and 2867cm-1; NH2 bending of chitosan: 1559cm-1; and C-O-C
stretching of chitosan and Si–O–Si stretching of pumice: 1024cm-1 (Sepehr, Amrane,
Karimaian, Zarrabi & Ghaffari, 2014; Veisi, Najafi & Hemmati, 2018). On the other hand, it
was noticed that the functional groups of Fe3O4/chitosan/pumice hybrid beads were shifted to
lower wavenumbers following the production of Pd NPs (Fig. 1b). It can be explained by
interactions between Fe3O4/chitosan/pumice hybrid beads and Pd NPs.
8

…………………………………Fig. 1………………………….
micrograms of Fe3O4/chitosan/pumice hybrid beads
FE-SEM
and
Pd
NPs@Fe3O4/chitosan/pumice hybrid beads are shown in Fig. 2. As seen in the micrograms,
both the designed support and the catalyst have spherical forms. These results confirmed that
hybrid beads were successfully fabricated. Additionally, FE-SEM analyses was carried out at
higher magnifications to detect formation of Pd NPs on Fe3O4/chitosan/pumice hybrid beads
(Fig. 2c). It was found that the fabrication of palladium nanoparticles was successfully
achieved. Fig. 3 displays EDS spectrum of Fe3O4/chitosan/pumice hybrid beads and Pd NPs
@Fe3O4/chitosan/pumice hybrid beads. As clearly seen in Fig. 3b, the presence of Pd peaks
confirm the preparation of palladium nanoparticles. Additionally, TEM analyses of Pd NPs
@Fe3O4/chitosan/pumice hybrid beads was performed and it was detected that the majority of
9

palladium nanoparticles, which are stabilized on the support, lie in the size range about 20 nm
(Fig. 4).
……………………………………Fig.2………………………….
……………………………………Fig. 3………………………….
10

……………………………………Fig. 4………………………….
TGA was used to measure thermal durability of Fe3O4/chitosan/pumice hybrid beads
and Pd NPs@Fe3O4/chitosan/pumice hybrid beads (Fig. 5). The thermogram of
Fe3O4/chitosan/pumice hybrid beads showed that the maximum decomposition temperature
(Tmax) was 240.7 °C. As depicted in Fig. 5, this value was recorded as 221.4ꢀ°C for Pd NPs
@Fe3O4/chitosan/pumice hybrid beads. These results showed that the thermal stability of
Fe3O4/chitosan/pumice hybrid beads was found to be higher than those of the catalyst. This
decrease in Tmax of the catalyst can be explained by the fact that the palladium nanoparticles
catalyze the thermal decomposition of the chitosan/pumice matrix (Baran, Sargin, Kaya &
Menteş, 2016; Ziegler-Borowska, Chełminiak & Kaczmarek, 2015).
11

……………………………………Fig. 5………………………….
For further characterization of Fe3O4/chitosan/pumice hybrid beads and Pd NPs
@Fe3O4/chitosan/pumice hybrid beads, powder XRD analyses were performed, and their
diagrams are given in Fig. 6. Both Fe3O4/chitosan/pumice hybrid beads and its catalyst
displayed broad peaks at ~20° which can be associated with characteristic peaks of chitosan
and pumice (Baran & Menteş, 2017; Correcher, Gomez-Ros, Dogan, Garcia-Guinea &
Topaksu, 2017). Fe3O4/chitosan/pumice hybrid beads displayed typical diffraction peaks at
30.16°, 35.44°, 43.29°, 53.61°, 57.28°, and 62.65°, which are assigned to (220), (311), (400),
(422), (511), and (440) crystal planes of Fe3O4, respectively (Lotfi & Veisi, 2019) (Fig. 7a). In
XRD pattern of Pd NPs@Fe3O4/chitosan/pumice hybrid beads, new peaks were observed at
40.16°, 46.75°, and 68.26° in addition to the characteristic peaks of Fe3O4 (Fig. 6b). These
important peaks are indexed to (111), (200), and (220) crystalline planes of face-centered Pd,
12

confirming the fabrication of palladium nanoparticles (Kora & Rastogi, 2018; Sadjadi,
Malmir, Heravi & Ghoreyshi Kahangi, 2019).
……………………………………Fig. 6………………………….
3.2. Investigation of catalytic role of Pd NPs@Fe3O4/chitosan/pumice hybrid beads
Before the catalytic efficacy of Pd NPs@Fe3O4/chitosan/pumice hybrid beads against
synthesis of benzonitriles was investigated, preliminary studies were performed using p-
CH3C6H4I, which is chosen as the test substrate, to detect optimal reaction conditions. The
optimized reaction conditions were determined as follows: 0.01% mol catalyst, Na2CO3 as
base system, DMF as solvent, 120ꢀ°C as reaction temperature, and 3 hours as reaction time
(please refer to Supplementary data). With the optimum reaction parameters at hand, the
catalytic role of Pd NPs@Fe3O4/chitosan/pumice hybrid beads were tested in cyanation of
various aryl iodides with K4[Fe(CN)6] (Table 1). The catalytic tests showed that aryl iodides,
which bear different substituted groups, were transformed to corresponding benzonitriles by
Pd NPs@Fe3O4/chitosan/pumice hybrid beads in excellent yields. For example, Pd
NPs@Fe3O4/chitosan/pumice hybrid beads successfully cyanated m-NO2C6H4I with 97%
13

yield. p-CH3OC6H4I furnished the desired benzonitrile product in 94% yield. Excellent
benzonitriles yields were reached with p-CH3C6H4I, m-CH3C6H4I, and o-CH3C6H4I. To
demonstrate universal adaptability of Pd NPs@Fe3O4/chitosan/pumice hybrid beads, their
catalytic performance was also evaluated against aryl bromide cyanation using K4[Fe(CN)6].
Pd NPs@Fe3O4/chitosan/pumice hybrid beads appeared to be highly efficient for cyanation of
aryl bromides. p-NO2C6H4Br and m-NO2C6H4Br smoothly produced desired cyanides with
good yields. Cyanation yield of p-CNC6H4Br to p-CNC6H4CN in the presence of Pd
NPs@Fe3O4/chitosan/pumice hybrid beads was 97%. Additionally, the catalytic behavior of
Pd NPs@Fe3O4/chitosan/pumice hybrid beads was also evaluated against cyanation of aryl
chlorides, and good product yields were reached. The catalyst successfully cyanated m-
NO2C6H4Cl with 86% yield. These results show that the designed Pd
NPs@Fe3O4/chitosan/pumice hybrid beads are useful as a catalyst for aryl iodide, bromide,
and chloride cyanations. In order to show the catalytic superiority of Pd
NPs@Fe3O4/chitosan/pumice hybrid beads, their catalytic activity on the cyanation of p-
CH3C6H4Br was compared to that of the catalysts reported in literature, and the results are
summarized in Table 2. These results show that Pd NPs@Fe3O4/chitosan/pumice hybrid
beads are more useful than the other catalysts in terms of reaction yield and reaction time.
Long-lasting catalysts provide a significant advantage for industrial applications.
Therefore, the recoverability and reusability of Pd NPs@Fe3O4/chitosan/pumice hybrid beads
were tested in the cyanation of p-CH3C6H4I using K4[Fe(CN)6]. After the typical cyanation
reaction, Pd NPs@Fe3O4/chitosan/pumice hybrid beads were recollected by external magnet,
rinsed with water, and dried for next runs. The same procedure was followed for each cycle.
Pd NPs@Fe3O4/chitosan/pumice hybrid bead confirmed that it was durable catalyst since it
gave a high reaction yield (84%) even after six successive runs. To show the constancy of Pd
NPs@Fe3O4/chitosan/pumice hybrid beads, FE-SEM and XRD analyses were conducted after
14

the recycle test (Fig.7). The results of these analyses were found to be similar to fresh Pd
NPs@Fe3O4/chitosan/pumice hybrid beads. These findings show that the catalytic
performance and constancy of Pd NPs@Fe3O4/chitosan/pumice hybrid beads were retained
for a long time. Moreover, leaching of palladium ions from Pd NPs@Fe3O4/chitosan/pumice
hybrid beads was investigated by ICP analysis after the recycling test, and it was found to be
insignificant (0.2%). This result display that the prepared Fe3O4/chitosan/pumice hybrid beads
had good interaction against palladium nanoparticles. More importantly, this result proves that
Pd NPs@Fe3O4/chitosan/pumice hybrid beads have good catalytic stability.
……………………………………Fig. 7………………………….
4. Conclusion
In conclusion, a highly useful catalyst system was designed by immobilization of
palladium nanoparticles on Fe3O4/chitosan/pumice hybrid beads. Then, Pd
NPs@Fe3O4/chitosan/pumice hybrid beads were evaluated as heterogeneous nanocatalyst
against various aryl halide cyanations with K4[Fe(CN)6]. These tests show that Pd
15

NPs@Fe3O4/chitosan/pumice hybrid beads have good substrate tolerance by catalyzing the
syntheses of various benzonitriles with high yields. Moreover, it was found that Pd
NPs@Fe3O4/chitosan/pumice hybrid beads could be easily collected via external magnet, and
it could be reused at six successive runs without significant palladium leaching. This paper
clearly shows that Pd NPs@Fe3O4/chitosan/pumice hybrid beads are suitable as a catalyst for
cyanation reactions in terms of their sustainability, high catalytic efficiency, easy separation,
and high recyclability.
16

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24

Scheme and Figure Captions
Fig. 1. FT-IR spectra of Fe3O4/chitosan/pumice hybrid beads (a) and Pd NPs
@Fe3O4/chitosan/pumice hybrid beads (b)
Fig. 2. FE-SEM images of Fe3O4/chitosan/pumice hybrid beads (a) and Pd NPs
@Fe3O4/chitosan/pumice hybrid beads (b and c)
Fig. 3. EDS spectra of Fe3O4/chitosan/pumice hybrid beads (a) and Pd NPs
@Fe3O4/chitosan/pumice hybrid beads (b)
Fig. 4. TEM images of Pd NPs @Fe3O4/chitosan/pumice hybrid beads
Fig. 5. TGA spectra of Fe3O4/chitosan/pumice hybrid beads and Pd NPs
@Fe3O4/chitosan/pumice hybrid beads
Fig. 6. XRD patterns of Fe3O4/chitosan/pumice hybrid beads (a) and Pd NPs
@Fe3O4/chitosan/pumice hybrid beads (b)
Fig. 7. FE-SEM images and XRD pattern of Pd NPs @Fe3O4/chitosan/pumice hybrid beads
after the reusability test
Scheme 1. Fabrication of Pd NPs @Fe3O4/chitosan/pumice hybrid beads
25

Table 1. Cyanation reaction of aryl halides with K4[Fe(CN)6] in the presence of Pd
NPs@Fe3O4/chitosan/pumice hybrid beads
Entry
1
Ar-X
Product
Yield (%)b
94
2
97
3
4
95
93
5
91
6
7
92
88
8
9
91
97
98
96
10
11
12
91
26

13
89
14
15
85
82
16
17
83
86
18
80
a
Reaction conditions: Aryl halides (1.5 mmol), K4Fe(CN)6 (0.2 mmol), base (1.8 mmol), 0.01% mol Pd
NPs@Fe3O4/chitosan/pumice hybrid beads, DMF (6.0 mL), 120°C.
b: isolated yield
27

Table 2. Comparison of Pd NPs@Fe3O4/chitosan/pumice hybrid beads with other reported
catalysts in the cyanation of p‐CH3OC6H4Br
Entry
Catalyst
Time Yield (%)
Ref.
1
P–O bidentate chelate palladium complex
16 h
6 h
84
90
(Fu, Li, Zhu,
Chen, Kang &
Guo, 2014)
(Hemmati,
Sedrpoushan,
Soudalizadeh,
Khosravi &
Hekmati, 2019)
(Nasrollahzadeh,
Maryami,
2
3
4
Pd NPs/RGO‐Rosa canina
Fe3O4@SiO2‐BAT‐Pd(II)
Pd NPs
7h
9h
90
85
Sajjadi &
Mehdipour,
2019)
(Kandathil,
Dateer,
Sasidhar, Patil
& Patil, 2018b)
(Nasrollahzadeh,
2016)
(Magdesieva,
Nikitin,
5
6
Pd/CuO NP
15 h
8 h
88
66
Pd/PPycatalyst
Zolotukhina &
Vorotyntsev,
2014)
7
8
PdLHMS-3 catalyst
16 h
75
91
(Modak, Mondal
& Bhaumik,
2012)
Pd NPs@Fe3O4/chitosan/pumice hybrid 3 h
beads
Present study
28