Production and Application of Highly Efficient and Reusable Palladium Nanocatalyst Decorated on the Magnetically Retrievable Chitosan/Activated Carbon Composite Microcapsules

Article abstract of DOI:10.1007/s10562-019-02739-1

Abstract: This study reports (i) the production of magnetically retrievable microcapsules as immobilizing agents, which are composed of chitosan/activated carbon composite (CS-AC/Fe₃O₄), (ii) the green synthesis of highly stable palladium nanoparticles on CS-AC/Fe₃O₄ without using any toxic reducing agents (Pd NPs@CS-AC/Fe₃O₄), (iii) the investigation of catalytic behavior of Pd NPs@CS-AC/Fe₃O₄ in Suzuki–Miyaura reactions of different aryl iodides, bromides, and chlorides, and (iv) the examination of recoverability and reusability of Pd NPs@CS-AC/Fe₃O₄. The characterization of Pd NPs@CS-AC/Fe₃O₄ was performed by FT-IR, TG/DTG, XRD, SEM, and EDS analyses. It was found that the average sizes of palladium nanoparticles were changed in the range of 31–48?nm. The catalytic tests revealed that Pd NPs@CS-AC/Fe₃O₄ was a very effective catalyst against synthesis of various biaryl compounds via Suzuki–Miyaura reactions, by giving high reaction yields under mild reaction conditions. Furthermore, it was found that Pd NPs@CS-AC/Fe₃O₄ was a highly retrievable and practical nanocatalyst due to its reusable nature. Pd NPs@CS-AC/Fe₃O₄ gave 95% of yield after ten successive cycles. These results show that Pd NPs@CS-AC/Fe₃O₄ is a superb catalyst and it can be applied in different catalytic systems or industrial applications due to the fact that it offers notable advantages such as high catalytic performance, reusability, stability, excellent functional group tolerance, wide substrate scope, and simple separation. Graphical Abstract: [Figure not available: see fulltext.].

Full text of DOI:10.1007/s10562-019-02739-1

Catalysis Letters
https://doi.org/10.1007/s10562-019-02739-1
Production and Application of Highly Efficient and Reusable Palladium
Nanocatalyst Decorated on the Magnetically Retrievable Chitosan/
Activated Carbon Composite Microcapsules
Talat Baran1
Received: 1 February 2019 / Accepted: 3 March 2019
© Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract
This study reports (i) the production of magnetically retrievable microcapsules as immobilizing agents, which are composed
of chitosan/activated carbon composite (CS-AC/Fe3O4), (ii) the green synthesis of highly stable palladium nanoparticles on
CS-AC/Fe3O4 without using any toxic reducing agents (Pd NPs@CS-AC/Fe3O4), (iii) the investigation of catalytic behav-
ior of Pd NPs@CS-AC/Fe3O4 in Suzuki–Miyaura reactions of different aryl iodides, bromides, and chlorides, and (iv) the
examination of recoverability and reusability of Pd NPs@CS-AC/Fe3O4. The characterization of Pd NPs@CS-AC/Fe3O4 was
performed by FT-IR, TG/DTG, XRD, SEM, and EDS analyses. It was found that the average sizes of palladium nanoparticles
were changed in the range of 31–48 nm. The catalytic tests revealed that Pd NPs@CS-AC/Fe3O4 was a very effective catalyst
against synthesis of various biaryl compounds via Suzuki–Miyaura reactions, by giving high reaction yields under mild reac-
tion conditions. Furthermore, it was found that Pd NPs@CS-AC/Fe3O4 was a highly retrievable and practical nanocatalyst
due to its reusable nature. Pd NPs@CS-AC/Fe3O4 gave 95% of yield after ten successive cycles. These results show that Pd
NPs@CS-AC/Fe3O4 is a superb catalyst and it can be applied in different catalytic systems or industrial applications due to
the fact that it offers notable advantages such as high catalytic performance, reusability, stability, excellent functional group
tolerance, wide substrate scope, and simple separation.
Graphical Abstract
Keywords Chitosan · Activated carbon · Palladium nanocatalyst · Suzuki reaction
1 Introduction
Biaryls have been successfully used in many areas from
fabrication of important natural products to pharmacol-
ogy, cosmetics and medicine industries, and thus they are
* Talat Baran
valuable and versatile organic compounds [1–4]. Metal cata-
lyzed Suzuki–Miyaura cross-coupling reaction is one of the
most significant synthetic approaches used to synthesize
talatbaran_66@hotmail.com
1
Department of Chemistry, Faculty of Science and Letters,
Aksaray University, 68100 Aksaray, Turkey
Vol.:(0123456789)
1 3

T. Baran
biaryls, and it has great importance in both industrial and
academic researches [5–10]. In addition, Suzuki–Miyaura
cross-coupling reaction has many advantages such as high
tolerance against substrate, high selectivity, and easy acces-
sibility compared to other cross coupling reactions [11, 12].
Considering all these important advantages, there are tre-
mendous efforts to develop highly efficient homogenous or
heterogeneous catalysts systems for Suzuki cross coupling
reactions in literature [13–16]. It was reported that hetero-
geneous catalysts are preferred by researchers compared to
homogeneous catalysts which have some problems such as
separation of catalyst in the reaction media, purification
of the final product, and reusability of catalyst [17, 18].
Although heterogeneous catalysts have high catalytic per-
formance, catalyst is not facilely and efficiently separated
from the reaction media via conventional techniques such as
filtration and centrifugation separations. These methods are
not preferred in the industry applications due to inefficiency,
high cost, and time-consummation [19]. Therefore, recovery
and recyclability problems of catalysts can be overcome by
the preparation of catalyst with magnetic property [20–22].
These catalysts can be easily separable with external magnet
from the reaction media, and this property makes it worth-
while for the commercialization of the catalyst.
magnet from the reaction media and successfully reused ten
times in the coupling reaction of phenyl boronic acid with
p-iodoanisole. These results show that Pd NPs@CS-AC/
Fe3O4 is a suitable nanocatalyst for conversion of aryl bro-
mides, iodides, and chlorides to desired coupling products.
2 Materials and Methods
2.1 Materials
Chitosan, activated carbon, FeSO4·7H2O, FeCl3·6H2O,
PdCl2, NH4OH, Na2CO3, KOH, Cs2CO3, NaOH, glutaral-
dehyde, aryl halides and phenyl boronic acid, and methanol
were obtained from Sigma-Aldrich.
2.2 Instrumentation
FT-IR spectra of CS-AC/Fe3O4 and Pd NPs@CS-AC/Fe3O4
were recorded by a Perkin Elmer Spectrum 100 FT-IR spec-
trophotometer. X-ray pattern of Pd NPs@CS-AC/Fe3O4 was
recorded by Rigaku smart lab system (at 40 kV, 30 mA,
and 2θ with a scan angle: 10°–75°). The surface images of
CS-AC/Fe3O4 and Pd NPs@CS-AC/Fe3O4 and EDS map-
ping of Pd NPs@CS-AC/Fe3O4 were obtained using Zeiss
Supra 55VP. Thermal stabilities of CS-AC/Fe3O4 and Pd
NPs@CS-AC/Fe3O4 were investigated by EXSTAR S11
7300 (nitrogen atmosphere; heating range: 30–650 °C).
Among the transition metals, palladium is one of the most
important and most used metals in the catalytic reactions,
and researchers therefore have designed various heteroge-
neous palladium complexes or palladium nanoparticles as
catalysts using different support materials such as silica, pol-
ymer, and diatomite for Suzuki–Miyaura reactions [23–26].
Among the supports, natural biopolymers and carbon-based
materials have been widely used due to their biodegradabil-
ity, chemically stability, large surface area, cheapness, and
abundance [7, 27]. Among the biopolymers, chitosan is a
non-toxic, biodegradable, environmentally friendly, and
multi-functional natural biopolymer [28, 29]. On the other
hand, activated carbon is a special material due to its large
surface area, low-cost, ease of preparation, and microporous
structure [30, 31]. Additionally, both chitosan and activated
carbon readily allow chemical modifications to provide coor-
dination sites for metal ions [32]. Considering these superior
physical and chemical properties of chitosan and activated
carbon, these materials are important candidates as supports
for transition metal ions in catalytic reactions.
2.3 Fabrication of Fe3O4 Particles
4.2 g of FeSO4·7H2O and 6.1 g of FeCl3·6H2O were trans-
ferred into 100 mL of water and stirred at 90 °C for 30 min.
Subsequently, 10 mL of NH4OH was added into the reaction
mixture and stirred at 80 °C for 30 min. Finally, Fe3O4 pow-
der particles were recovered with filtration and extensively
rinsed with water and dried in an oven at 80 °C.
2.4 Preparation of Fe3O4‑Loaded Chitosan/
Activated Carbon Microcapsules (CS‑AC/Fe3O4)
Magnetic microcapsules were prepared as follows: chitosan
(2 g) was dissolved in 100 mL of 2% acetic acid solution
(v/v). Then, 1 g of activated carbon was added to the chi-
tosan solution, and the mixture was stirred at room tempera-
ture for 3 h to ensure homogeneity. Afterwards, previously
prepared Fe3O4 powder particles (1 g) was transferred into
the reaction media, and the mixture was stirred for another
3 h until becoming homogeneous. Subsequently, chitosan-
activated carbon/Fe3O4 mixture was dropped in to the solu-
tion consisting 60 mL of ethanol, 40 mL of water, and 12 g
of NaOH to obtain gelatinous microcapsules. The micro-
capsules were collected by filtration and washed with water
In this study, magnetic microcapsules, which consist
of chitosan-activated carbon composites (CS-AC), were
designed as catalyst support, and then palladium nanoparti-
cles were successfully decorated on the support and charac-
terized (Pd NPs@CS-AC/Fe3O4). Then, the catalytic activity
of Pd NPs@CS-AC/Fe3O4 was investigated in Suzuki cross-
coupling reactions, and excellent biphenyl conversions were
reached in very short reaction time. More significantly, Pd
NPs@CS-AC/Fe3O4 was readily collected with an external
1 3

Production and Application of Highly Efficient and Reusable Palladium Nanocatalyst Decorated…
until neutral pH. Then gelatinous microcapsules were intro-
duced into cross-linking solution (2 mL of glutaraldehyde
solution in 50 mL of methanol) and refluxed at 70 °C for
6 h. Finally, magnetic microcapsules were filtrated out and
washed with methanol, and then they were allowed to dry
at room temperature.
2.5 Green Synthesis of Palladium Nanoparticles
on Designed Magnetic Microcapsules (Pd NPs@
CS‑AC/Fe3O4)
1 g of CS-AC/Fe3O4 was suspended in 50 mL of water at
room temperature. Then 0.3 g of PdCl2 was added to reac-
tion media and stirred at 100 °C for 3 h to provide trans-
formation of Pd(II) to Pd(0), and it was observed that the
color of the reaction solution gradually changed to dark gray.
Finally, palladium nanoparticles were collected by using a
magnet, washed with distilled water, and dried at room tem-
perature (Fig. 1).
2.6 General method For Suzuki–Miyaura Coupling
Reactions
Fig. 2 FT-IR spectrum of a CS-AC/Fe3O4 and b Pd NPs@CS-AC/
A mixture of Pd NPs@CS-AC/Fe3O4 (1.5 × 10−3 mmol),
phenyl boronic acid (1.8 mmol), aryl halides (1.0 mmol),
K2CO3 (3.5 mmol) were added to a Schlenk tube, and it
was heated under microwave irradiation at 400 W for 6 min.
After the completion of coupling reaction, the mixture was
cooled at room temperature, and it was extracted with
water:toluene (1:2 v/v). Finally, desire biaryls were collected
by evaporation of organic phase under reduced pressure and
characterized by GC/MS analyses.
Fe3O4
of free carbonyl groups of glutaraldehyde (1730 cm−1) were
not observed in the spectrum. On the other hand, a new peak
was observed at 1653 cm−1 which was attributed to the imine
vibration. This band showed that cross-linking of CS-AC/
Fe3O4 was achieved. In case of Pd NPs@CS-AC/Fe3O4, it
was observed that the stretching of imine band shifted to
1641 cm−1. This shift can be explained by the strong interac-
tion of Pd ions with functional groups of CS-AC/Fe3O4 [33].
The size and shape of CS-AC/Fe3O4 and Pd NPs@
CS-AC/Fe3O4 were examined by SEM, and their images
are given in Fig. 3. SEM micrographs demonstrated
that CS-AC/Fe3O4 (Fig. 3a) and Pd NPs@CS-AC/Fe3O4
microcapsules (Fig. 3b) have nearly spherical formations.
This result showed that cross-linking procedure was suc-
cessfully achieved. When the surface morphology of the
catalyst was examined at higher magnifications (Fig. 3c,
3 Results and Discussion
3.1 Characterization of Pd NPs@CS‑AC/Fe3O4
FT-IR spectra of CS-AC/Fe3O4 and Pd NPs@CS-AC/Fe3O4
are given in Fig. 2. When CS-AC/Fe3O4 spectrum was exam-
ined, NH2 bending of chitosan (1586 cm−1) and stretching
Fig. 1 Image of Pd NPs@
CS-AC/Fe3O4
1 3

T. Baran
Fig. 3 SEM micrograms of a CS-AC/Fe3O4 and b, c, d Pd NPs@CS-AC/Fe3O4
d), it was seen that the palladium nanoparticles were
immobilized on the surface of CS-AC/Fe3O4. Addition-
ally, it was determined that palladium nanoparticles had
spherical morphology and their average sizes were in
the range of 31–48 nm. On the other hand, EDS analy-
sis was performed to determine the chemical composition
of Pd NPs@CS-AC/Fe3O4. This analysis showed that Pd
NPs@CS-AC/Fe3O4 was composed of O, C, N, Fe and Pd
elements. This result revealed that palladium nanoparticles
were successfully stabilized on CS-AC/Fe3O4.
Structural characterization of Pd NPs@CS-AC/Fe3O4 was
also performed using powder XRD analysis, and the pattern
is given in Fig. 4. XRD analysis of Pd NPs@CS-AC/Fe3O4
showed strong peaks at 30.37°, 35.68°, 43.33°, 54.03°,
57.51°, and 63.02°. These diffraction peaks are indexed
to (220), (311), (400), (422), (511), and (440) planes of
Fe3O4, confirming the formation of magnetite particles [34].
Fig. 4 XRD pattern of Pd
NPs@CS-AC/Fe3O4
1 3

Production and Application of Highly Efficient and Reusable Palladium Nanocatalyst Decorated…
Besides these peaks, Pd NPs@CS-AC/Fe3O4 also exhibited
characteristic peaks at 40.62°, 46.42°, and 67.73° which cor-
responded to (111), (200), and (220) crystalline planes of Pd,
respectively [35, 36]. These results confirmed the production
of palladium nanoparticles on the CS-AC/Fe3O4.
ranging from 1 min to 7 min, and 6 min was determined as
the optimized reaction time for further studies. On the other
hand, the model reaction was carried out in the absence of
Pd NPs@CS-AC/Fe3O4, and no product was obtained. This
result revealed that Pd NPs@CS-AC/Fe3O4 has a specific
role as the catalyst for Suzuki–Miyaura reactions. With
these optimal reaction conditions in hand, the catalytic
performance of Pd NPs@CS-AC/Fe3O4 was evaluated in
the synthesis of various biaryls, and the results are sum-
marized in Table 1. Aryl iodides gave the desired coupled
products with excellent yields in the presence of the catalyst
(entries 1–6). For example, p-OCH3 substituted aryl iodide
produced 99% reaction yield (entry 1). After the coupling
reaction of m-NO2 substituted aryl iodide, corresponding
coupled product was obtained with 92% yield (entry 2). The
catalytic performance studies were extended using aryl bro-
mides as substrates. The tests indicated that aryl bromides
with electron-donating or electron withdrawing groups dis-
played excellent activities by producing the desired biaryls
with good yields in the presence of Pd NPs@CS-AC/Fe3O4
(entries 7–16). For instance, para, metha, and ortho-OCH3
substituted aryl iodides were converted to the desired biphe-
nyls with yields of 91%, 84%, and 76%, respectively (entries
7–9). Following the coupling reactions between 1-bromo-
4-nitrobenzene and 1-bromo-3-nitrobenzene with phenyl
boronic acid, the desired target products were obtained with
96% and 90% of yields, respectively (entries 11 and 12).
When aryl bromides containing electron-donating groups
such as –para and -metha substituted-CH3 were used, the
product yields were determined as 70% and 66%, respec-
tively (entries 15 and 16). Then substrate scope of Pd NPs@
CS-AC/Fe3O4 was also investigated by using aryl chlorides
less reactive than aryl iodides and aryl bromides, and it was
recorded that Pd NPs@CS-AC/Fe3O4 exhibited good cata-
lytic activity (entries 17–23). As evident from Table 1, 73%
Thermal behavior of CS-AC/Fe3O4 and Pd NPs@CS-AC/
Fe3O4 were explored by TG/DTG analysis at heating rate of
10 °C min−1 in the nitrogen atmosphere at the temperature
range of 30–650 °C (Fig. 5). While maximum thermal degra-
dation temperature (Tmax) of CS-AC/Fe3O4 was determined
as 239.3 °C, Tmax of Pd NPs@CS-AC/Fe3O4 was recorded
as 262.6 °C (Fig. 5). These results showed that Pd NPs@
CS-AC/Fe3O4 was thermally more stable than CS-AC/Fe3O4.
3.2 Catalytic Performance of Pd NPs@CS‑AC/Fe3O4
in Suzuki Reactions
To determine optimum reaction conditions, the cross cou-
pling reaction between p-iodide anisole and phenyl boronic
acid was preferred as the model reaction due to its simplic-
ity. Then, it was carried out under variable parameters such
as different amounts of Pd NPs@CS-AC/Fe3O4, different
reaction times, and base systems. Afterwards, the reaction
conditions were optimized. Additionally, coupling reactions
were performed under microwave irradiation because this
technique produces high reaction yields within short reac-
tion time and requires mild reaction conditions. The effec-
tiveness of the catalyst loading on the reaction yield was
studied by using different quantities of Pd NPs@CS-AC/
Fe3O4, and the highest reaction yield (99%) was reached
with 1.5×10−3 mmol Pd NPs@CS-AC/Fe3O4. Among dif-
ferent bases (Na2CO3, KOH, Cs2CO3, NaOH), K2CO3 gave
the highest reaction yield (99%) and was chosen as the suita-
ble base system for Suzuki–Miyaura reactions. Additionally,
model coupling reaction was performed under reaction times
Fig. 5 TG/DTG spectra of a CS-AC/Fe3O4 and b Pd NPs@CS-AC/Fe3O4
1 3

T. Baran
Table 1 Catalytic activity of
Pd NPs@CS-AC/Fe3O4 in
the Suzuki–Miyaura coupling
reaction
product yield was reached with p- substituted-CN aryl chlo-
ride (entry 21). These findings indicated that the designed
Pd NPs@CS-AC/Fe3O4 has high tolerance against aryl bro-
mides, iodides, and chlorides. To show the catalytic effi-
ciency of Pd NPs@CS-AC/Fe3O4 and the advantages of the
developed method, the findings of this study was compared
with other previously reported catalysts, and the results are
listed in Table 2. These data show that Pd NPs@CS-AC/
Fe3O4 is more efficient than other catalysts, producing high
reaction yields with very shorter reaction time. Addition-
ally, the developed method offers some advantages such as
avoiding (i) use of toxic organic solvents, (ii) consumption
of excessive energy, (iii) intensive work force, and (iv) envi-
ronmental damage.
Entry
X
R
Yield
1
2
3
4
5
6
7
8
I
I
I
I
I
I
4-OCH3 99
3-NO2
4-NH2
2-CH3
3-CH3
4-CH3
92
80
69
72
79
Br 2-OCH3 76
Br 3-OCH3 84
Br 4-OCH3 91
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Br 4-CN
Br 3-NO2
Br 4-NO2
Br 3-NH2
Br 4-NH2
Br 3-CH3
Br 4-CH3
Cl 2-OCH3 45
Cl 3-OCH3 51
Cl 4-OCH3 67
Cl 3-NO2
Cl 4-CN
Cl 3-CH3
Cl 4-CH3
98
90
96
70
76
66
70
3.3 Reusability of Pd NPs@CS‑AC/Fe3O4
Easily recoverable and highly reusable catalysts are highly
desirable in both academic and industrial applications as
they reduce production costs. In this study, the reusability of
Pd NPs@CS-AC/Fe3O4 was investigated on model reactions.
At the end of model coupling reaction, Pd NPs@CS-AC/
Fe3O4 that was collected from reaction media with exter-
nal magnet was regenerated by washing with hot water and
methanol, and then the refreshed catalyst was used for next
runs. Additionally, this regeneration method was repeated
for each cycle. Reproducibility tests indicated that Pd NPs@
CS-AC/Fe3O4 provided 95% product yield even after recy-
cling ten-times. In order to evaluate the recycling ability
of Pd NPs@CS-AC/Fe3O4, Table 3 lists the comparison
of reaction yields of the last cycles of different catalysts in
literature with those of the designed catalyst. As seen in
Table 3, it was revealed that Pd NPs@CS-AC/Fe3O4 was a
70
73
40
52
Reaction conditions 1.0 mmol
aryl halides, 1.8 mmol phenyl
boronic acid, 3.5 mmol K2CO3
and 1.5×10−3 mmol Pd NPs@
CS-AC/Fe3O4, 6 min, 400 W
Table 2 Comparison of
catalytic performances of
various catalysts with Pd NPs@
CS-AC/Fe3O4
Entry
Catalyst
Solvent
Time
Yield (%)
Refs.
1
2
3
4
5
6
7
8
Pd NPs
H2O
EtOH
H2O/EtOH
H2O
H2O
DMF/H2O
H2O/EtOH
H2O
EtOH/H2O
MeOH
EtOH/H2O
DMF
EtOH/H2O
H2O/EtOH
DMF
12 h
8 h
3 h
3 h
3 h
10 min
5 h
2.5
97
98
92
95
97
93
99
98
96
91
98
90
96
96
92
99
[2]
[3]
[5]
PdL2
Pd(0/II)/CS-bigua@Fe3O4
CS-g-mPEG350 Pd (0) catalyst
CA/Pd(0)
Fe3O4/SiO2/HPG–OPPh2–PNP
Pd-Ni/TiO2 IV
Fe3O4@SiO2-4-AMTT-Pd(II)
Fe3O4@SiO2/isoniazide/Pd
Pd/Fe3O4 NPs
chitosan–biguanidine/Pd
Pd-BIP-γ-Fe2O3@SiO2
SBA-15-supported Pd-catalyst 2
MNPs-NHC-Pd(ΙΙ)
Pd catalyst
[27]
[37]
[38]
[39]
[40]
[41]
[42]
[43]
[44]
[45]
[46]
[47]
Present study
9
0.5
10
11
12
13
14
15
16
12 h
0.5 h
2 h
6 h
0.5
1 h
6 min
Pd NPs@CS-AC/Fe3O4
Solvent-free
1 3

Production and Application of Highly Efficient and Reusable Palladium Nanocatalyst Decorated…
Table 3 Comparison of
Entry
Catalyst
Recycle no
Yield (%)
Refs.
reusability capabilities of
various catalysts with Pd NPs@
CS-AC/Fe3O4
1
2
3
4
5
6
7
8
PdNP/rGO
PdeSMU-MNPs
Pd@PANI
PCIL-1
Fe3O4@SiO2-NHC-Pd(II)
Cell-NHC-Pd
Pd(0) nanocatalyst
Pd-γ-Fe2O3
MNPs@SB-Pd nanomagnetic catalyst
Pd@NH2-MIL-125
Pd NPs@CS-AC/Fe3O4
10
8
6
5
8
5
8
6
6
57
94.5
85
91
86
58
83
89
85
78
95
[50]
[51]
[52]
[53]
[54]
[55]
[56]
[57]
9
10
11
[58]
[59]
Present study
4
10
highly retrievable and reusable catalyst, by producing 95%
yield even after ten consecutive runs. Additionally, hot fil-
tration test was performed according to previous studies to
show the heterogeneity of Pd NPs@CS-AC/Fe3O4 [48, 49].
This test indicated that Pd NPs@CS-AC/Fe3O4 had het-
erogeneous nature. On the other hand, palladium leaching
test was performed after recycling ten-times, and very low
palladium leach was observed (˂0.5%). This test indicated
that the developed Pd NPs@CS-AC/Fe3O4 was a highly sta-
ble catalyst. Additionally, SEM analysis of used Pd NPs@
CS-AC/Fe3O4 was performed to determine any changes in
the shape and size of nanoparticles, and it was observed that
the surface morphology of catalyst did not change (Fig. 6).
were characterized with different analytical techniques.
Then, the catalytic performance of Pd NPs@CS-AC/Fe3O4
was tested against conversion of various aryl iodides, bro-
mides, and chlorides to corresponding coupled products
via Suzuki–Miyaura reactions. These tests showed that Pd
NPs@CS-AC/Fe3O4 had high tolerance against different
aryl halides containing electron withdrawing and electron-
donating groups, by displaying excellent catalytic activi-
ties under solvent-free media and very short reaction time.
Additionally, the reusability tests indicated that Pd NPs@
CS-AC/Fe3O4 is highly retrievable and reusable for ten
successive cycles due to its easy recovery with its mag-
netic property. Consequently, this study showed that Pd
NPs@CS-AC/Fe3O4 was a superior catalyst compared to
other reported catalysts in terms of price, stability, cata-
lytic activity, retrievability, and reusability.
4 Conclusions
Highly stable and eco-friendly palladium nanoparticles
were successfully embedded on the magnetically separable
microcapsules, which consist of chitosan/activated carbon
composite, without using any reducing agents and they
Fig. 6 SEM micrograms of Pd NPs@CS-AC/Fe3O4 after the 10th runs
1 3

T. Baran
33. Baran T, Sargin I, Kaya M, Menteş A, Ceter T (2017) J Colloid
Interf Sci 486:194–203
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