Magnetically separable carbon nanocomposite catalysts for efficient nitroarene reduction and Suzuki reactions

Article abstract of DOI:10.1016/j.apcata.2014.02.029

Novel magnetically recyclable carbon nanocomposites were synthesized to support various nanocatalysts using a simple, economical and scalable method. The designed nanocomposites, which are composed of porous carbon and Fe ₃O₄ nanocrystals, can be used as an expandable platform to load versatile nanoparticle catalysts such as Pd and Pt. These nanocomposites with high surface area and permeable porous structure can contain abundant and accessible small-sized catalyst nanoparticles. These characteristics led to efficient catalytic reactions and enhanced catalytic activity, which were verified in selective reduction of nitroarenes and Suzuki cross-coupling reactions. The nanocomposite catalysts provided excellent catalytic activities to yield the desired products in short reaction time and mild reaction conditions. The catalysts could be easily separated from the reaction mixture by a magnet, and recycled five consecutive cycles in reduction of nitrobenzene and Suzuki cross-coupling of bromobenzene without losing significant activities.

Full text of DOI:10.1016/j.apcata.2014.02.029

Applied Catalysis A: General 476 (2014) 133–139
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Magnetically separable carbon nanocomposite catalysts for efficient
nitroarene reduction and Suzuki reactions
Mohammadreza Shokouhimehra,b,1, Taeho Kima,b,1, Samuel Woojoo Juna,b
,
Kwangsoo Shina,b, Youngjin Janga,b, Byung Hyo Kima,b
Jaeyun Kimc, Taeghwan Hyeona,b,∗
,
a Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul 151-742, Korea
b School of Chemical and Biological Engineering, College of Engineering, Seoul National University, Seoul 151-742, Korea
c School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel magnetically recyclable carbon nanocomposites were synthesized to support various nanocatalysts
using a simple, economical and scalable method. The designed nanocomposites, which are composed of
porous carbon and Fe3O4 nanocrystals, can be used as an expandable platform to load versatile nanopar-
ticle catalysts such as Pd and Pt. These nanocomposites with high surface area and permeable porous
structure can contain abundant and accessible small-sized catalyst nanoparticles. These characteristics
led to efficient catalytic reactions and enhanced catalytic activity, which were verified in selective reduc-
tion of nitroarenes and Suzuki cross-coupling reactions. The nanocomposite catalysts provided excellent
catalytic activities to yield the desired products in short reaction time and mild reaction conditions. The
catalysts could be easily separated from the reaction mixture by a magnet, and recycled five consec-
utive cycles in reduction of nitrobenzene and Suzuki cross-coupling of bromobenzene without losing
significant activities.
Received 11 November 2013
Received in revised form 27 January 2014
Accepted 19 February 2014
Available online 28 February 2014
Keywords:
Palladium nanoparticles
Heterogeneous catalysis
Magnetic separation
Suzuki cross-coupling
Reduction
Nanocomposite
Carbon materials
© 2014 Elsevier B.V. All rights reserved.
1. Introduction
reusability of the catalyst becomes complicated [12–14]. Conse-
quently, typical industrial heterogeneous catalysts are composed
Catalysts play important roles in various fields such as oil refin-
ing, fine chemicals and pharmaceutical productions, and energy
conversions [1,2]. Catalysts are generally classified into two types:
homogeneous and heterogeneous catalysts. Homogeneous cata-
lysts have the advantages of being dissolved in reaction medium,
thus providing mild reaction conditions, and higher activities and
selectivities compared to their heterogeneous counterparts [3]. For
example, homogeneous palladium catalysts have been widely used
in various catalytic transformations such as Buchwald–Hartwig
amination, hydrogenation, Heck, Sonogashira, and Suzuki reac-
tions [4–9]. These catalysts, however, are of somewhat limited use
in the industry due to the difficulties in separating the products
contaminated with residual unstable complexes and recycling the
expensive catalysts [10,11]. These catalytic reactions need typical
work-up steps to isolate the product from the mixture, and the
of supported metal nanoparticles (NPs) owing to their advan-
tages of recovering and reusing of the catalysts [15–17]. However
traditional micrometer-sized heterogeneous catalysts generally
suffer from low catalytic activities due to the slow diffusion of
reactants [18,19]. Accordingly, heterogeneous catalytic reactions
generally require more severe conditions than those of homo-
geneous catalysts [20,21]. Recent advancements in the synthesis
of uniformly sized NPs offer numerous opportunities to improve
the catalytic performance [22–24]. Although nanoparticle-based
catalysts (nanocatalysts), which are often considered as a bridge
between homogeneous and heterogeneous catalysts, have high cat-
alytic activities because of their high surface-to-volume ratio, they
suffer from several drawbacks such as recovery and instability
at high reaction temperatures. Furthermore nanocatalysts with-
out any support are usually unstable, and coagulation is inevitable
[25,26]. These facts have motivated continuous research efforts for
the developments of highly active and sustainable nanocomposite
catalysts [27,28].
∗
Corresponding author at: Center for Nanoparticle Research, Institute for Basic
Science (IBS), Seoul 151-742, Korea. Fax: +82 2 886 8457.
Of the wide range of catalyst supports, porous carbon mate-
rials have been extensively employed in heterogeneous catalysis
because of their desirable properties including permeable pores,
E-mail address: thyeon@snu.ac.kr (T. Hyeon).
Both authors contributed equally to this work.
1
http://dx.doi.org/10.1016/j.apcata.2014.02.029
0926-860X/© 2014 Elsevier B.V. All rights reserved.

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M. Shokouhimehr et al. / Applied Catalysis A: General 476 (2014) 133–139
chemical inertness, and good mechanical stability [29–32]. Because
the supports strongly affect the activity of catalyst NPs, numerous
studies have been performed to modify the properties of carbon
supports [33–36]. Nitrogen doping of carbon materials improves
chemical/physical properties. In particular, the nitrogenated sites
are known to enhance the interaction between nanocatalysts
and support [37–40]. Furthermore, it is an important issue to
develop economical and scalable approaches for preparing recy-
clable porous carbon nanocomposites.
Magnetic separation, among the various procedures for remov-
ing catalysts, obviates the requirement of catalyst filtration after
the completion of reactions and provides an easy technique for
recycling nanocatalysts by using a magnet [41–44]. This method
minimizes the possibility of nanocatalyst aggregation during recov-
ery and improves the durability of the catalysts [45–48]. The
efficiency of the heterogeneous nanocatalysts also depends on
the size, shape, composition and their interaction with sup-
ports [49–51]. Recently various NPs were immobilized in porous
nanocomposite supports for fabrication easily recoverable and
highly active catalysts [52–54]. Herein we report an economical
scalable procedure to synthesize magnetically retrievable carbon
nanocomposite catalysts by combining magnetic NPs, nitrogen-
doped porous carbon support and ∼ 3 nm-sized catalyst NPs of
Pd or Pt. The designed carbon nanocomposite catalysts provide
excellent catalytic activities for reduction of nitroarenes and Suzuki
cross-coupling reactions.
oleate (120 mmol) were dissolved in a mixture solvent composed of
80 ml ethanol, 60 ml distilled water and 140 ml hexane. The result-
ing solution was heated to 70 ◦C and kept at that temperature for
4 h. Then, the upper organic layer containing the iron-oleate com-
plex was washed three times with distilled water in a separatory
funnel. After washing, hexane was evaporated off resulting in iron-
oleate complex in a waxy solid form. The synthesized iron-oleate
complex (36 g, 40 mmol) and 5.7 g of oleic acid (20 mmol) were
dissolved in 200 g of 1-octadecene at room temperature. The reac-
tion mixture was heated to 300 ◦C with a constant heating rate of
3.3 ◦C min−1 and then kept at that temperature for 1 h. The result-
ing solution containing the nanocrystals was then cooled to room
temperature and 500 ml of ethanol was added to the solution to
precipitate the nanocrystals. The nanocrystals were separated by
centrifugation and dispersed in chloroform.
2.3. Synthesis of magnetically recyclable polymer and carbon
nanocomposite catalysts
In a typical synthesis, 0.5 g of Fe3O4 NPs was dispersed in 400 ml
of chloroform and stirred at room temperature for 15 min. To this
solution 15 ml pyrrole was directly added. While stirring vigorously
400 mg of palladium(II) acetate dissolved in 30 ml of CHCl3 was
added dropwise and the mixture was stirred for 8 h at room temper-
ature to yield the magnetically recyclable polymer nanocomposite
catalyst. The product was isolated by centrifugation and washed
several times with chloroform. Finally the product was carbonized
at 400 ◦C for 4 h under hydrogen gas flow to produce the magneti-
cally recyclable carbon nanocomposite catalyst.
2. Experimental
2.1. Characterization
2.4. Heterogeneous Suzuki cross-coupling reactions catalyzed by
nanocomposite Pd catalyst
The loading amount of palladium and platinum in the mag-
netically recyclable nanocomposite catalysts was measured
by inductively coupled plasma-atomic emission spectrometry
(ICP-AES). The intermediates and final nanocomposite catalyst
materials were characterized by transmission electron microscopy
(TEM), X-ray photoelectron spectroscopy (XPS), High resolution
powder X-ray diffraction (HRXRD), X-ray fluorescence (XRF)
spectrometry, attenuated total reflection infrared spectroscopy
(ATR-IR) and CHN elemental analysis. TEM images were obtained
using a JEOL JEM-2010 microscope. High resolution TEM (HRTEM)
images were obtained using a JEOL JEM-3010 microscope equipped
with energy-dispersive X-ray spectroscopy (EDX) detector at an
acceleration voltage of 200 kV. Scanning transmission electron
microscopy (STEM) and High resolution STEM (HRSTEM) images
were acquired using a JEOL JEM-2100F. The mi-micromeritics 3
Flex-surface characterization analyzer was used to measure the
physisorption isotherms and surface area of the magnetically
recyclable nanocomposite catalysts. ICP-AES was used for the
elemental analysis using a Shimadzu ICPS-7500 Japan instrument.
XPS was performed to collect core level spectra of Pd (3d) and
Pt (4f) scans using Al K␣ source (Sigma probe, VG Scientifics).
HRXRD was obtained by a Bruker D8 Advance instrument. XRF
spectrometry was recorded by a Bruker AXS S4 pioneer. The IR
spectra were recorded with an ATR-IR Perkin Elmer spectrometer
frontier. The products of the catalytic reactions were analyzed
by gas chromatography mass spectrometers (GC-MS) using an
Agilent Technologies 5975C VL MSD with triple-axis detector and
a Hewlett Packard 5973 mass selective detector GC-MS.
Nanocomposite Pd catalyst (1 mol%) was added to a round-
bottom flask (25 ml) and dispersed in dimethylformamide
(DMF)/H2O (2:1) mixture. Then, aryl halide (0.5 mmol), aryl boronic
acid (0.6 mmol), K2CO3 (1.5 mmol), and a small stirring bar were
added to the round-bottom flask. The flask containing reaction
mixture was placed in an oil bath (100 ◦C) and stirred under air
atmosphere. After completion of reaction, the mixture was cooled
to room temperature and the nanocomposite Pd catalyst was sepa-
rated using a magnet. The separated catalysts were washed several
times with DMF. Finally the products were analyzed by a GC-MS.
2.5. Heterogeneous reduction of nitroarenes catalyzed by
nanocomposite Pt catalyst
The reduction of nitroarenes was carried out in a 25 round-
bottom flask. In a typical procedure, 1 mol% of nanocomposite Pt
catalyst was dispersed in EtOH. Then, nitrobenzene (0.5 mmol),
hydrazine (2 equiv.), and a small stirring bar were added to the
flask. The flask containing reaction mixture was placed in an oil
bath (80 ◦C) and stirred under air atmosphere. After completion
of reaction, the mixture was cooled to room temperature and the
nanocomposite Pt catalyst was separated using a magnet. The sepa-
rated catalysts were washed several times with EtOH. The products
were analyzed by a GC-MS.
3. Results and discussion
The overall synthetic procedure to prepare magnetically recy-
clable carbon nanocomposite catalysts is illustrated in Fig. 1.
Polymer nanocomposite was first prepared via a redox reaction
between pyrrole and Pd(OAc)2 in the presence of iron oxide NPs.
Pyrrole monomers can be chemically polymerized using palla-
dium(II) acetate as an oxidizing agent. Subsequently the magnetic
2.2. Synthesis of iron oxide NPs
Iron oxide NPs were synthesized using the previously reported
methods [55,56]. In a typical synthesis of iron-oleate complex,
10.8 g of iron chloride (FeCl3·6H2O, 40 mmol) and 36.5 g of sodium

M. Shokouhimehr et al. / Applied Catalysis A: General 476 (2014) 133–139
135
Fig. 1. Synthetic procedure of the magnetically recyclable carbon nanocomposite Pd catalyst.
carbon nanocomposite Pd catalyst was prepared via carbonization
of the synthesized polymer nanocomposite. This procedure pro-
vides direct chemical reduction of palladium ions during pyrrole
oxidation so that it incorporates the Pd NPs inside the polymer
matrix and subsequently the carbon nanocomposite. Consequently
relatively uniform 3 nm-sized Pd nanocatalysts are embedded and
stabilized in an N-doped carbon framework.
Developing a simple method to produce a large amount of
hybrid nanocomposites is very challenging because each con-
stituent material has different physicochemical properties and
requires different reaction conditions. We conducted several con-
trol experiments to optimize the synthetic conditions. The iron
oxide NPs for magnetic separation are generally dispersible in
organic solvents such as CHCl3. After performing several control
reactions, we found that among various palladium(II) precursors,
only Pd(OAc)2 is soluble in chloroform, enabling a one-phase reac-
tion without agglomeration.
TEM images (Fig. 2a) of the magnetic iron oxide NPs showed
that they were relatively uniform and spherical with an average
diameter of 18 nm. TEM images of the polymer (Fig. 2b) and car-
bon (Fig. 2c) nanocomposite Pd catalysts revealed that Pd NPs
were crystallized with an average distribution size of 3 nm. STEM
images of the carbon nanocomposite Pd catalyst (Fig. 2d) indi-
cated a distinct contrast of Pd and Fe3O4 NPs incorporated in the
carbon matrix. HRTEM images clearly showed the porous carbon
matrix which is an important parameter for accessibility of reac-
tants to the nanocatalysts (Fig. S1). The ATR-IR spectrum of the
polypyrrole nanocomposite catalyst exhibited strong characteris-
tic vibration peaks of ring, C N, and C H stretching at 1557, 1417,
and 930 cm−1, respectively (Fig. S2). The EDX (Fig. 3a) and XRF (Fig.
S3) spectra revealed that the nanocomposite Pd catalyst is com-
posed of carbon, iron and palladium. The presence of palladium
NPs in the carbon nanocomposite catalyst was verified by XPS anal-
ysis (Fig. 3c). The magnetic property of the carbon nanocomposite
Pd catalyst was investigated using a superconducting quantum
interference device (SQUID) magnetometer. The field-dependent
magnetization curve at 300 K revealed superparamagnetic behav-
ior (Fig. 3b). The HRXRD pattern revealed that the nanocomposite
Pd catalyst is composed of Fe3O4 and Pd NPs (Fig. 3d). In addition,
CHN elemental analysis showed the composition of C (38.4%) and
N (7.5%).
various bases, and the best performance was obtained with K2CO3
(Table S2).
To extend the scope of this magnetically recyclable carbon
nanocomposite Pd catalyst, we carried out the coupling of several
aryl iodides with phenylboronic acid under the optimized reac-
tion conditions. In all presented aryl iodide substrates (Table 1,
entries 1–6) almost quantitative yields of products were obtained
in 1.5 h. Furthermore, in an attempt to extend the application of
the designed catalyst, we screened the Suzuki cross-coupling reac-
tions of representative aryl bromides with phenylboronic acid. The
reaction of these aryl bromides gave excellent yields in 3 h (Table 1,
entries 7–12). More interestingly, Suzuki coupling of arylchlorides
with phenylboronic acid, which are known to be very difficult to be
catalyzed by heterogeneous catalytic systems were also converted
to the coupled products in 15 h with high yields using 1.5 mol% of
the Pd catalyst (Table 1, entries 13 and 14).
The hydrolysis of arylboronic acids generally occurs in Suzuki
cross-coupling reactions and causes decrease in the product yields
[57,58]. Therefore we investigated the reaction of various aryl-
boronic acids with iodobenzene in DMF/H2O (2:1). As shown in
Table 2, the Suzuki cross-coupling reactions of the arylboronic
acids with iodobenzene using the magnetically recyclable carbon
nanocomposite Pd catalyst (1 mol%) were achieved successfully in
DMF/H2O. The reactions were accomplished to produce the respec-
tive biaryls with high yields within 1.5 h.
To compare the catalytic activity differences between the poly-
mer nanocomposite Pd catalyst and the carbon nanocomposite Pd
catalyst, we performed the Suzuki coupling reaction of iodoben-
zene with phenyl boronic acid using both kinds of catalysts. The
carbon nanocomposite catalyst gave much higher conversion (97%)
than the polymer nanocomposite catalyst (31%) under the same
reaction conditions in 1.5 h. We ran the catalytic reactions using the
polymer and carbon nanocomposite Pd catalysts (1 mol%) under
identical reaction conditions, and aliquots were drawn from the
reaction mixtures at 15 min intervals. The yield of products in each
reaction was measured and the results are shown in Fig. 4. The
reaction was completed within 1.5 h with the carbon nanocom-
posite Pd catalyst while the reaction catalyzed by the polymer
nanocomposite took more than 7 h for the completion. The out-
standing increase of reaction rate for the carbon nanocomposite
catalyst can be explained by pore diffusion [59–61].
The catalytic performance of the magnetically recyclable carbon
nanocomposite Pd catalyst was investigated in Suzuki cross-
coupling reactions. To make the reaction conditions greener
we screened various organic/water mixtures as the solvent in
the cross-coupling of iodobenzene with phenylboronic acid with
1 mol% of the catalyst. The yield of this heterogeneous catalytic
reactions was found to be solvent-dependent with 2:1 volume ratio
of DMF/H2O giving the highest yield (Table S1). We next tested the
coupling of iodobenzene with phenylboronic acid in the presence of
These results demonstrate the porous carbon nanocompos-
ite catalyst with a high surface area of 74 m2 g−1 (Fig. 5) is
a more efficient catalyst than polymer nanocomposite with a
low surface area of 6 m2 g−1 (Fig. S7). The Pd NPs in polymer
nanocomposites cannot be reactive because they are thoroughly
coated and immersed in the polymer matrix. Unlike the polymer
matrix, the porous carbon nanocomposite support is permeable to
organic reagents and improves the accessibility of the nanocat-
alysts and diffusion of reactants and products. The well-defined

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M. Shokouhimehr et al. / Applied Catalysis A: General 476 (2014) 133–139
Fig. 2. (a) TEM image of Fe3O4 NPs. (b) TEM image of polymer nanocomposite Pd catalyst. (c) TEM image of carbon nanocomposite Pd catalyst. (d) STEM image of carbon
nanocomposite Pd catalyst.
nitrogen-containing carbon increases the interaction between the
nanocatalysts and carbon matrix, enabling to maintain their activ-
ities in harsh reaction conditions such as temperature alteration,
stirring and shaking. The designed carbon nanocomposite pro-
vides a high surface area and accommodates a large amount of
small sized nanocatalysts, leading to the high catalytic activity. In
addition, magnetic separation of the carbon nanocomposite cata-
lyst is much more convenient for the catalyst recycling than that
required by the polymer nanocomposite (Fig. S8). These attractive
features exhibited by the designed magnetically recyclable carbon
nanocomposite enabled to have high catalytic activity for Suzuki
reactions in milder reaction conditions and shorter reaction time
compared to those required by our previously reported hetero-
geneous catalysts [24,62,63]. The magnetically recyclable carbon
nanocomposite Pd catalyst also presented higher catalytic activ-
ity than the commercially available Pd/C catalyst. TEM images of
the commercial Pd/C catalyst shows Pd NPs are polydisperse with
a size distribution of 5 to 25 nm (Fig. S9). When 1 mol% of com-
mercial Pd/C catalyst was used in the Suzuki coupling reaction of
iodobenzene with phenyl boronic acid under the identical reac-
tion conditions, it provided a much lower yield (39%) in 1.5 h.
These advantages, including excellent product yield and sustain-
able catalytic activity, make this nanocomposite catalyst a potential
candidate for industrial considerations.
reduction of nitro aromatics is an important chemical reaction
because organic amines are intermediate materials for the pro-
duction of agrochemicals, pharmaceuticals, polymers and pigments
[64–67]. Magnetically recyclable nanocomposite Pt catalyst can be
prepared using a similar procedure for the nanocomposite Pd cat-
alyst. We first prepared the polymer nanocomposite Pt catalyst
via a direct redox reaction between pyrrole and a Pt precursor
(PtCl2) as an oxidizing agent in the presence of iron oxide NPs.
Then the magnetically retrievable carbon nanocomposite Pt cat-
alyst was prepared via carbonization of the synthesized polymer
nanocomposite.
TEM images of this nanocomposite showed the Pt NPs were
uniform with an average size of 3 nm (Fig. S4). EDX of the nanocom-
posite Pt catalyst showed that the Pt species were successfully
immobilized in the nanocomposite (Fig. S5). The existence of Pt
NPs on the nanocomposite was also confirmed by XPS analysis
(Fig. S6). In a continuation of our research toward the development
of sustainable organic transformations, we investigated the cat-
alytic activity of the nanocomposite Pt catalyst for the reduction of
structurally diverse nitro compounds. When we tested the catalytic
performance of the nanocomposite Pt catalyst for the reduction
of nitrobenzene using hydrazine, the reaction was completed in
3 h yielding quantitative aniline (Table 3, entry 1). In an attempt
to extend the application of this catalyst, we studied the reduc-
tion of structurally diverse nitro compounds. Table 3 confirmed
that the nanocomposite Pt catalyst exhibited excellent activities
for the reduction of nitrobenzenes. The selective reduction of nitro
group in organic compounds containing other reducible functional
The designed magnetically recyclable carbon nanocomposite
can be readily used as general framework supports for loading
other noble metal NPs, such as platinum, which can be uti-
lized for catalytic reduction of nitro compounds to amines. The

M. Shokouhimehr et al. / Applied Catalysis A: General 476 (2014) 133–139
137
Fig. 3. (a) EDX spectrum of the carbon nanocomposite Pd catalyst. (b) Field-dependent magnetization of the carbon nanocomposite Pd catalyst. (c) XPS analysis of Pd 3d
scan. (d) HRXRD pattern of magnetically recyclable carbon nanocomposite Pd catalyst.
80
60
40
20
0
100
90
80
70
60
50
40
30
20
10
0
0.2
0.1
0.0
0
50
100
150
200
Pore diameter (nm)
Adsorption
Desorption
0
15
30
45
60
75
90 105 120
Time (min)
0.0
0.2
0.4
0.6
0.8
1.0
Fig. 4. Time-dependent product yields of the Suzuki cross-coupling reactions using
polymer (red line) and carbon (green line) nanocomposite Pd catalysts. Reaction
conditions: aryl iodide (0.5 mmol), phenylboronic acid (0.6 mmol), catalyst (1 mol%),
K2CO3 (1.5 mmol), DMF/H2O (2:1), 100 ◦C.
Relative pressure (P/Po)
Fig. 5. N2 adsorption/desorption isotherms of the magnetically recyclable carbon
nanocomposite catalyst. The inset shows the corresponding pore size distribution.
groups is a very challenging issue in organic synthesis [68–70].
However, the nitro group of nitroarenes with different functional
groups using the magnetically recyclable nanocomposite catalyst
was selectively reduced to the amino moiety (Table 3, entries 2–4).
The halogen functional groups remained intact under the reaction
conditions. In all cases examined in Table 3, the excellent yields of
amine products were obtained as exclusive products.
Reusability and durability of the catalysts are important factors
for practical applications. To verify these issues, we investigated
magnetic separation and recycling of the magnetically recyclable
nanocomposite Pt catalyst (Fig. 6), which was successfully recycled
and reused for five consecutive cycles of the reduction of nitroben-
zene with no significant loss of activity (Table 4). Upon completion
Fig. 6. Magnetic separation and recycling of the carbon nanocomposite Pt catalyst.
of the reaction the catalyst was easily separated using a magnet,
washed with EtOH and reused in the next reaction.
When we examined the magnetic separation and durability of
the nanocomposite Pd catalyst in the Suzuki coupling reaction

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M. Shokouhimehr et al. / Applied Catalysis A: General 476 (2014) 133–139
Table 1
Table 2
Heterogeneous Suzuki cross-coupling reaction of aryl halides with phenylboronic
Heterogeneous Suzuki cross-coupling reaction of aryl iodide with arylboronic acidsa.
acida.
B(OH)2
I
Catalyst
X
B(OH)2
+
Catalyst
+
R
R
Yield (%)b
97
X = I, Br, Cl
Entry
1
Arylboronic acid
Product
Entry
Aryl halide
Product
Time (h)
Yield (%)b
(HO)2B
I
1
2
1.5
1.5
97
94
(HO)2B
I
2
95
(HO)2B
(HO)2B
I
I
3
4
94
93
3
4
1.5
1.5
93
95
(HO)2B
5
95
I
a
Aryl iodide (0.5 mmol), aryl boronic acid (0.6 mmol), carbon nanocomposite Pd
catalyst (1 mol%), K2CO3 (1.5 mmol), DMF/H2O (2:1), 100 ◦C, 1.5 h.
Yields (average of at least two runs) were determined by GC-MS analysis using
internal standard (decane).
5
6
1.5
1.5
91
92
b
I
H3CO
H3CO
Br
Table 3
Heterogeneous reduction of substituted nitrobenzene with hydrazinea.
7
8
3
3
95
93
Br
NO2
NH 2
Catalyst
R
R
Br
Br
Entry
Substrate
Product
Yield (%)b
9
3
91
NH2
NO2
1
2
3
99
98
95
10
11
3
3
92
94
NH2
NH2
Br
NO2
NO2
NC
NC
Cl
Br
I
Cl
Br
I
Br
12
13
3
91
Cl
NO2
NH2
15
91c
81c
4
5
97
95
Cl
NH2
NO2
14
15
a
Aryl halide (0.5 mmol), phenylboronic acid (0.6 mmol), carbon nanocomposite
Pd catalyst (1 mol%), K2CO3 (1.5 mmol), DMF/H2O (2:1), 100 ◦C.
NO2
NH2
b
Yields (average of at least two runs) were determined by gas chromatography
6
94
mass spectrometry (GC-MS) analysis using internal standard (decane).
c
1.5 mol% Pd catalyst was used. Isolated yield was confirmed by GC-MS.
a
Substituted nitrobenzene (0.5 mmol), hydrazine (2 equiv.), carbon nanocom-
posite Pt catalyst (1 mol%), EtOH, 80 ◦C, 3 h.
b
Yields (average of at least two runs) were determined by GC-MS with respect to
an internal standard (decane).
of bromobenzene with phenylboronic acid (Table S3), there was
a small decrease of the activity after each recycling of the cata-
lyst. The amount of palladium in the nanocomposite catalyst was
analyzed after recovering the catalyst after the five cycles of the
Suzuki coupling reactions of bromobenzene. The ICP-AES analysis
indicated 1.4% of the palladium species remained in the reaction
solution. TEM images of the recycled carbon nanocomposite Pd cat-
alyst showed that the nanocomposite catalyst was stable after the
recycling (Fig. S10). Therefore, the small decline of catalytic activity
seems to result from incomplete magnetic separation of the cata-
lyst during consecutive recycling because the viscosity of DMF is
lower than EtOH.
Table 4
Magnetic separation and recycling of the nanocomposite Pt catalyst in heteroge-
neous reduction of nitrobenzene with hydrazinea.
Cycle
1st
99
2nd
99
3rd
98
4th
97
5th
96
Yield of productb
a
Nitrobenzene (0.5 mmol), hydrazine (2 equiv.), carbon nanocomposite Pt cata-
lyst (1 mol%), EtOH, 80 ◦C, 3 h.
b
Yields were determined by GC-MS with respect to an internal standard (decane).

M. Shokouhimehr et al. / Applied Catalysis A: General 476 (2014) 133–139
139
Magnetically recyclable carbon nanocomposite catalyst can be
readily synthesized in large scale using a simple and economical
process. For example, when we used 10 times more reagents, ∼5.6 g
ofthemagneticallyrecyclablecarbonnanocompositecatalystcould
be obtained in one batch synthesis (Fig. S11).
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Acknowledgments
We acknowledge financial support by the Research Center Pro-
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