Preparation of magnetically separable Cu6/7Co1/7Fe2O4-graphene catalyst and its application in selective reduction of nitroarenes

Article abstract of DOI:10.1016/j.catcom.2014.10.016

A magnetically separable and highly active Co-Cu mixed spinel catalyst, Cu_6/7Co_1/7Fe₂O₄-graphene (Cu_6/7Co_1/7Fe₂O₄-G), was fabricated by a hydrothermal method. The resu

Full text of DOI:10.1016/j.catcom.2014.10.016

Catalysis Communications 59 (2015) 161–165
Contents lists available at ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
Preparation of magnetically separable Cu Co Fe O –graphene
6
/7
1/7 2 4
catalyst and its application in selective reduction of nitroarenes
Haiyan Zhang, Ying Zhao, Weihua Liu, Shutao Gao, Ningzhao Shang, Chun Wang ⁎, Zhi Wang
College of Sciences, Agricultural University of Hebei, Baoding 071001, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 August 2014
Received in revised form 4 October 2014
Accepted 17 October 2014
Available online 28 October 2014
A magnetically separable and highly active Co–Cu mixed spinel catalyst, Cu6/7Co1/7Fe O –graphene (Cu6/7Co1/7
2
4
Fe
sessed excellent catalytic activity for the reduction of a broad range of nitroarenes in the presence of NaBH
composite catalyst was efficient, stable, low-cost and could be easily recovered due to its magnetic separability.
2014 Elsevier B.V. All rights reserved.
2 4
O
–G), was fabricated by a hydrothermal method. The results demonstrated that the Cu6/7Co1/7Fe
2 4
O –G pos-
4
. The
©
Keywords:
Nitroarenes
Reduction
2 4
Cu6/7Co1/7Fe O –graphene
Sodium borohydride
1
. Introduction
more economical, easily available, and environmentally benign alterna-
tives for the catalytic reduction of nitroarenes.
Aromatic amines are important starting materials and intermediates
Carbon-based nanomaterials, such as carbon nanotubes, graphene
and mesoporous carbon, are important supports for the metal and
metal oxide nanoparticles in heterogeneous catalysis [11]. In particular,
graphene, a novel one-atom-thick two-dimensional graphitic carbon
system, has attracted particular research interest due to its high surface
area, excellent electronic, thermal, optical, and mechanical proper-
for the manufacture of a great variety of chemicals such as dyes, pesti-
cides, herbicides, and agrochemicals [1–3]. At present, they are general-
ly synthesized from the corresponding aromatic nitro compounds by a
catalytic reduction or a non-catalytic process. The conventional non-
catalytic method mainly uses metal/acid [2], such as Fe/HCl, that
requires a stoichiometric excess of reagents, which presents difficulties
in product isolation and eventually produces a large amount of second-
ary waste. Therefore, it is not considered an environmentally benign
process. In contrast, catalytic reduction method has the merits of better
product quality and less pollution, so an increasing number of re-
searchers have shifted their attention to catalytic reduction in recent
years. The catalytic reduction systems include catalytic hydrogenation
2 2
ties [12,13]. To date, various kinds of catalysts, such as TiO [14], SnO
[15], ZnO [16], Pt [17,18], Pt–Ru [19], Pt–Pd [20], Pd [21] and so on,
have been supported on graphene-based templates for catalyzing dif-
ferent chemical transformations, energy conversion and photocatalytic
reactions. Graphene-based nanomaterials have also been explored as
an efficient catalyst for the catalytic reduction of nitroarenes. For in-
3 4 3 4
stance, superparamagnetic graphene–Fe O nanocomposite (G–Fe O )
[
4], iron-based compound catalysts [5], nano-metal catalysts [6–8],
was fabricated and used as an efficient catalyst for the reduction of
noble metal catalysts [9,10] and so on. However, most of these methods
have one or more shortcomings that need to be overcome. For example,
nitroarenes with hydrazine hydrate as a reductant [22].
Spinel ferrites MFe
packed arrangement of the oxygen ions with M ions at
2 4
two different crystallographic sites [23]. In recent years, MFe O has
2 4
O (M_Cu, Co, Mn, etc.), has a cubic close-
2
+
3+
catalytic hydrogenation needs high temperature and high H
2
pressure,
and Fe
moreover the selectivity is a major issue. Iron-based catalysts are mainly
explored for the reduction of aromatic nitro compounds in the presence
of hydrazine hydrate. Hydrazine hydrate reduction delivers selectivity
but the scale-up production of amines needs to be addressed due to hy-
drazine hydrate's explosive nature and toxicity. Most of the nano-metal
catalysts contain Pd, Ag or other precious metals, which is expensive.
The precious noble metal catalysts are expensive and usually sensitive
to both air and moisture. All these problems led researchers to find
been widely applied in sensors, electronics and catalysis because it
exhibits several advantages, such as relatively cheap, environmentally
compatible, moisture insensitive, high dispersive, and easily separative
[24]. Li et al. [25] explored mesoporous silica KIT-6 supported
superparamagnetic CuFe
hydrosilylation of ketones in air. Parella et al. [26] developed the catalyt-
ic application of CuFe nanoparticles for the Friedel–Crafts acylation.
Binary spinel ferrites MFe have also been explored as efficient
catalyst for the catalytic reduction of nitroarenes. Feng et al. [27] inves-
tigated the catalytic activity of CuFe nanoparticles for the reduction
2 4
O nanoparticles for catalytic asymmetric
2 4
O
2 4
O
⁎
Corresponding author. Tel.: +86 312 7528291.
E-mail address: chunwang69@126.com (C. Wang).
2 4
O
http://dx.doi.org/10.1016/j.catcom.2014.10.016
566-7367/© 2014 Elsevier B.V. All rights reserved.
1

162
H. Zhang et al. / Catalysis Communications 59 (2015) 161–165
GO
CuFe O -G
2
4
G-CuFe O4
2
Cu6/7Co1/7Fe O -G
2
4
G-Cu6/7Co1/7Fe O4
2
3
600 3200 2800 2400 2000 1600 1200 800
400
10
20
30
40
50
60
70
80
-
1
Wavenumbers / (cm )
2 Theta / (degree)
2 4 2 4
Fig. 1. FT-IR spectra of the GO, CuFe O –G(0.25) and Cu6/7Co1/7Fe O –G(0.25).
2 4 2 4
Fig. 3. XRD pattern of as-prepared CuFe O –G(0.25) and Cu6/7Co1/7Fe O –G(0.25).
of 4-nitrophenol to 4-aminophenol with excess amount of NaBH
CuFe supported on graphene has been prepared and used as an effi-
cient catalyst for the reduction of nitroarenes by our group [28]. The re-
sults demonstrate that the combination of CuFe with graphene can
lead to a dramatic enhancement of the catalytic activity of CuFe
which can be attributed to the remarkable synergistic effect between
the CuFe and the graphene sheets. Recently, Cu1− xCo Fe system
4
.
and ethanol were all obtained from Chengxin Chemical Reagents Com-
pany (Baoding, China). Nitroaromatics were purchased from Aladdin
Reagent Limited Company. The water used throughout the work was
double-distilled on a SZ-93 automatic double-distiller from Shanghai
Yarong Biochemistry Instrumental Factory (Shanghai, China).
The infrared (IR) spectra (cm ) were measured with a WQF-510
spectrometer. The size and morphology of the magnetic nanoparticles
were observed by scanning electron microscopy (SEM) using a Hitachi
S4800 field emission electron microscope operated at 30 kV and trans-
mission electron microscopy (TEM) using a JEOL model JEM-2011(HR)
at 200 kV. The X-ray diffraction (XRD) patterns of the samples were
recorded with a Rigaku D/max 2500 X-ray diffractometer using Cu Kα
radiation (40 kV, 150 mA). The stoichiometry of Cu and Co was deter-
mined by means of inductively coupled plasma atomic emission spec-
troscopy (ICP-AES) on Thermo Elemental IRIS Intrepid II. The energy
dispersive X-ray spectroscopy (EDS) spectra were taken on TEAM
energy spectrometer (EDAX USA). The Brunauer–Emmett–Teller
2 4
O
2 4
O
2 4
O ,
−
1
O
2 4
x
2 4
O
was found to be highly active for phenol alkylation with different
alkylating agents [29]. Cu–Co combination in terms of synergism and
3
d energy band overlap was suggested to be responsible for this
efficient process [30]. The application of Cu1− xCo Fe system in the
catalytic reduction of nitroarenes has not been reported yet.
Considering that the introduction of Co into CuFe system might
be an effective catalyst for the reduction of nitroarenes, in this paper, a
series of magnetically separable Cu1− xCo Fe –G composites were
prepared through a hydrothermal method and the effect of Co on the
catalytic activity of Cu1− xCo Fe –G composites was investigated. It
x
2 4
O
2 4
O
x
2 4
O
x
2 4
O
is believed that this method is an important addition to known proce-
dures for reduction of aromatic nitro compounds either on a lab as
well as on a larger scale.
(BET) surface areas were determined from the N
using V-Sorb 2800P.
2
adsorption at 300 K
2 4
2.2. Synthesis of Cu6/7Co1/7Fe O –graphene heteroarchitecture
2
. Experimental
Graphite oxide (GO) was prepared according to the procedure re-
ported by us [31]. Cu1− xCo Fe –G heteroarchitectures with graphene
content (25 wt.%) were synthesized by a modified hydrothermal
2
.1. Materials and apparatus
Ferric trichloride hexahydrate (FeCl
x
2 4
O
3
·6H
2
O, 99%), copper sulfate
method reported in the literature [24].
pentahydrate (CuSO
4
·5H
O, 98%), sodium borohydride (NaBH
30%), polyvinyl pyrrolidone, glycol, sodium hydroxide (NaOH, 98%),
2
O, 99%), Cobalt(II) nitrate hexahydrate
2 4
A typical experiment procedure for the synthesis of Cu6/7Co1/7Fe O –
graphene heteroarchitecture with 25 wt.% graphene content is as follows:
40 mg of GO was dispersed into 30 mL of ethylene glycol with sonication
(
(
Co(NO
3
)
2
·6H
2
4
, 97%), NH ·H
3
2
O
a
b
2 4
Fig. 2. SEM (a) and TEM (b) images of the Cu6/7Co1/7Fe O –G (0.25) sample.

H. Zhang et al. / Catalysis Communications 59 (2015) 161–165
163
Table 1
Screening and control experiments for hydrogenation of p-nitrophenol.
2.3. Reduction reactions of nitroarenes
In a 25 mL round bottom flask, nitroarenes (1.0 mmol, 1 eq.) were
dissolved in a mixture of 10 mL H O–EtOH (1:1, v/v). Then, sodium bo-
rohydride (5.0 mmol, 5 eq.) and Cu6/7Co1/7Fe –G (0.25) (20 mg)
2
2 4
O
were added. The mixture was stirred at 323–343 K for an appropriate
time depending upon the nature of the substrate. Upon completion of
the reaction (monitored by TLC), the mixture was cooled to room tem-
perature and the catalyst was separated by a magnet for recycling tests.
The reaction mixture was extracted with ether (3 × 10 mL). The organic
Entry
Catalyst
Catalyst
mg)
Temperture
(K)
Time
(min)
Yield
(%)
(
1
2
3
4
5
6
7
8
9
–
20
20
20
20
20
20
20
20
20
20
20
20
20
10
20
20
20
20
343
343
343
343
343
343
343
343
343
343
333
323
313
343
343
343
343
343
500
500
60
60
500
500
60
9
3
3
9
13
60
7
–
G
Trace
26
39
Trace
Trace
33
99
39
99
99
99
99
99
99
99
88
99
4
phase were combined together and dried over anhydrous MgSO .
Fe
Fe
NiFe
MnFe
CoFe
3
O
O
4
4
3
–G(0.25)
–G(0.25)
–G(0.25)
–G(0.25)
The solvent was evaporated under vacuum. The pure products were ob-
tained by silica-gel column chromatography using petroleum ether:
ethylacetate (4:1) as the eluent.
2
O
O
2 4
O
2 4
4
CuFe
CuFe
2
O
O
4
–G(0.25)
–G(0.25)
3. Results and discussion
2
4
10
11
12
13
14
15
16
17
18
Cu6/7Co1/7Fe
Cu6/7Co1/7Fe
Cu6/7Co1/7Fe
Cu6/7Co1/7Fe
Cu6/7Co1/7Fe
Cu3/4Co1/4Fe
Cu1/2Co1/2Fe
Cu6/7Co1/7Fe
Cu6/7Co1/7Fe
2
2
2
2
2
2
2
2
2
O
4
O
4
O
4
O
4
O
4
O
4
O
4
O
4
O
4
–G(0.25)
–G(0.25)
–G(0.25)
–G(0.25)
–G(0.25)
–G(0.25)
–G(0.25)
/NP–G(0.25)
/N–G(0.25)
2 4
3.1. Characterization of Cu6/7Co1/7Fe O –graphene
The FTIR spectra were recorded to testify the hybrid material. As
shown in Fig. 1, the spectrum of GO is in good agreement with previous
9
−
1
14
60
12
work [32]. The broad, intense band at 3250 cm
is assigned to the
−1
stretching of O–H. The peak at 1616 cm (aromatic C_C) can be as-
cribed to the skeletal vibrations of unoxidized graphene domains. The
Reaction condition: p-nitrophenol (1 mmol), solvent (10 ml, EtOH: water = 1:1), NaBH
5 mmol).
4
_
−1
C O bond is associated with the band at 1047 cm . From the FTIR
spectrum of GO, it can be clearly seen that the graphene oxide exhibits
(
−
1
an obvious characteristic absorption peak at about 1728 cm corre-
_
_
sponding to the stretching of the C_O and COOH groups. However,
it cannot be seen from the FTIR spectrum of CuFe –G (0.25) and
Cu6/7Co1/7Fe –G (0.25). It turned out that graphene oxide was
2 4
O
for 12 h. 0.144 g (0.576 mmol) of CuSO
Co(NO ·6H O and 0.3618 g (1.34 mmol) of FeCl
of ethylene glycol and sonicated for 1 h. The above two solutions were
then mixed together and stirred for 30 min. After that, the mixture was
·5H
4 2
O, 0.028 g (0.096 mmol) of
2 4
O
3
)
2
2
3
were added to 10 mL
reduced to graphene due to the strong reducing capability of ethylene
glycol during the preparation process. From the FTIR spectrum of
CuFe O –G (0.25) and Cu6/7Co Fe O –G (0.25) samples, the spectra
2 4 1/7 2 4
−
1
adjusted to pH of 8 with 6 mol L NaOH aqueous solution and stirred
for 30 min, yielding a stable homogeneous emulsion. The resulting mix-
ture was transferred into a 70 mL Teflon-lined stainless steel autoclave
and heated to 180 °C for 24 h under autogenous pressure. After the reac-
tion mixture was cooled down to room temperature, the precipitate was
filtered, washed with distilled water and ethanol, and dried in a vacuum
oven at 30 °C for 12 h. The product was labeled as Cu6/7Co1/7Fe
0.25). CuFe –graphene (CuFe –G) (0.25) was synthesized with
the same method without adding Co(NO ·6H O. For comparison, the
same method was also used to synthesize Cu6/7Co1/7Fe /NP–graphene
0.25) and Cu6/7Co1/7Fe /N–graphene (0.25) by adjusting to pH of 8
with NH ·H O (30%), while Cu6/7Co1/7Fe
adding 0.32 g polyvinyl pyrrolidone.
show a strong absorption corresponding to the stretching vibration of
−
1
the tetrahedral and octahedral sites around 586 and 400 cm , respec-
tively. The observed values illustrate that the frequency bands
−
1
appearing at 586 and 400 cm
metal oxide (CuFe and Cu6/7Co1/7Fe
596 cm on spectrum referred to the vibration of remainder H
are responsible for the formation of
). The absorption band at
O in
2
O
4
2 4
O
−
1
1
2
2 4
O –G
the sample [4,27].
Fig. 2 shows the SEM and TEM images of Cu6/7Co1/7Fe O –G (0.25)
2 4
2 4
sample. It can be seen that Cu6/7Co1/7Fe O –G were composed of
quasi-sphere particle with particle sizes of about 20 nm. It clearly
demonstrated that a crystal structure with spherical shape was formed.
X-ray powder diffraction analysis was used to identify the crystal
(
O
2 4
2 4
O
3
)
2
2
2 4
O
(
2 4
O
3
2
2
O
4
/NP–graphene (0.25) with
structure of the CuFe
shown in Fig. 3, except some Cu impurity peaks at 43.5° and 50.6°, all
peaks were indexed to be CuFe (JCPDS 77–0010), in detail, the
2 4 2 4
O –G (0.25) and Cu6/7Co1/7Fe O –G (0.25). As
2 4
O
peaks at 18.3° 30.0°, 35.5°, 53.5°, 57.1°, 62.6° and 74.1° are attributed
to (111), (220), (311), (422), (511), (440) and (533) crystal planes of
0
3
5
min
min
min
CuFe
was observed. It is speculated that the graphene in the CuFe
0.25) and Cu6/7Co1/7Fe –G (0.25) heteroarchitecture was fully
2 4
exfoliated due to the crystal growth of CuFe and Cu6/7Co1/7Fe O
2
O
4
while no typical diffraction peak of reduced graphene oxide
2 4
O
–G
(
2 4
O
2
O
4
nanoparticles between the interlayer of graphene sheets, which result
in the low diffraction intensity of graphene. Furthermore, no visible
peak corresponding to Co can be detected, which is ascribed to the
7
9
min
min
fine dispersion of Co or the insertion into the CuFe
formation of copper was identified based on the reported data (JCPDS
5–1326) at 43.5° and 50.6°. The reason of existence of metallic copper
2 4
O matrix. The
8
2
+
may be that some of Cu were reduced to copper metal in the forma-
tion process of CuFe and Cu6/7Co1/7Fe due to the strong reducing
3
00
350
400
450
O
2 4
2 4
O
Wavelength / (nm)
capability of ethylene glycol [27,28]. The result is consistent with that
reported in the documents [33].
The energy dispersive X-ray spectroscopy was shown in Fig. S1
(see Supporting information). Obviously, Co, Fe, Cu, C and O in the
Fig. 4. Successive UV–vis absorption spectra of the reduction of p-nitroaniline with NaBH
in the presence of Cu6/7Co1/7Fe –G (0.25) under 323 K.
4
2 4
O

164
H. Zhang et al. / Catalysis Communications 59 (2015) 161–165
Table 2
Chemoselective reduction of nitro compounds into amines by sodium borohydride catalyzed by Cu6/7Co1/7Fe
2 4
O –G (0.25).
Entry
Carbonyl Compound
Product
Temperature
K)
Time
(min)
Yield
(%)
TOF
(
(min−1)
1
2
323
13
99
1.22
323
8
99
1.98
3
4
5
323
333
343
9
10
35
99
96
95
1.76
1.54
0.43
6
7
323
333
40
15
99
91
0.40
0.97
8
9
343
343
323
30
25
12
96
95
99
0.51
0.61
1.32
1
0
1
1
343
25
91
0.58
4
Reaction condition: nitro compounds (1 mmol), NaBH (5 mmol), solvent (10 ml, EtOH: water = 1:1), catalyst (20 mg).
Cu6/7Co1/7Fe
2
O
4
–G (0.25) could be directly visualized from EDS. This
(Table 1, entry 1), indicating that the catalyst was necessary for the
reaction. Only low yields of the product were obtained with either
also proved the presence of cobalt and carbon. EDS elemental map-
ping showed the atomic distribution of Co, Fe, Cu, C and O (Fig. S2).
To further verify the existence of Co and the ratio of Cu and Co, the
composition of the catalyst was determined by ICP-AES. The ratio of
Cu to Co is 5.92:1, close to the stoichiometric ratio of Cu and Co is 6:1.
The concentration of Co in the catalyst was 2.99 wt.%.
graphene, Fe
MnFe –graphene (0.25) or CoFe
(Table 1, entries 2–7). 99% yield was obtained when the reaction was
performed at 343 K for 9 min with CuFe –G (0.25) as the catalyst
(Table 1, entry 8). However, the yield of the product is only 39% at
343 K for 3 min (Table 1, entry 9). The combination of CuFe –G
(0.25) with small amount of cobalt results in a dramatic enhance-
ment of the catalytic activity of CuFe –G (0.25). The reaction
time required to complete the reaction decreased from 9 min to 3 min
with Cu6/7Co1/7Fe –G (0.25) as the catalyst (Table 1, entry 10). The
3
O
4
, Fe
3
O
4
–graphene (0.25), NiFe
2 4
O –graphene (0.25),
2
O
4
2 4
O
–graphene (0.25) as catalyst
2 4
O
The BET adsorption isotherm obtained for Cu6/7Co1/7Fe
was shown in Fig. S3. The experimental multipoint BET surface area of
2 4
O –G (0.25)
2 4
O
2
−1
Cu6/7Co1/7Fe
.2. Catalytic activity Cu6/7Co1/7Fe
In the initial experiment, the p-nitrophenol was chosen as the model
2
O
4
–G (0.25) was found to be 119 m g
.
2 4
O
3
2 4
O –graphene
2 4
O
reaction still could be completed within a relatively short time
(13 min) when the reaction temperature lowered down to 323 K
(Table 1, entries 11, 12). But a longer reaction time (60 min) was re-
quired to complete the reaction with the reaction temperature at
reactant in order to examine the efficiency of different catalysts, the
effect of reaction temperature and the amounts of catalyst. As shown
in Table 1, no product was obtained in the absence of the catalyst
313 K (Table 1, entry 13). When the dosage of Cu6/7Co1/7Fe
0.25) decreased from 20 mg to 10 mg, the reaction can be completed
within 7 min (Table 1, entry 14). Compared with CuFe –G (0.25),
the excellent catalytic activity of Cu6/7Co1/7Fe –G (0.25) can be attrib-
uted to its unique heteroarchitechture, which provides the remarkable
synergistic effect between the Cu6/7Co1/7Fe and the graphene sheets.
The presence of graphene could enhance the adsorption of reactant
molecules onto the catalytic sites of the Cu6/7Co1/7Fe –G(0.25)
2 4
O –G
(
2 4
O
Table 3
The reduction of 4-nitrophenol catalyzed by different catalysts.
2 4
O
Entry Catalyst
Temperature Time Yield Ref.
K) (min) (%)
2 4
O
(
1
2
3
4
5
6
Cu6/7Co1/7Fe
PdCu/G (2 mol% Pd)
RHPrNH @Ag
Fe–phenanthroline/C (1 mol% Fe) 373
Co–Mo
2
O
4
–G (0.25)
323
323
373
13
90
65
99
98
98
This work
[6]
[34]
2 4
O
through the π–π stacking and/or electrostatic interaction. For compari-
son, Pd@C, a conventional noble metal catalyst, was employed as the
catalyst for the reduction of p-nitrophenol at 343 K for 4 min, the
yield was 99%. However, the Pd@C catalyst needs to use noble metal
2
600
180
20
97
100
82
[5]
[10]
[35]
2
C/AC
353
313
Resin-AuNPs

H. Zhang et al. / Catalysis Communications 59 (2015) 161–165
165
Pd and which is not so easy to separate by a magnet as the as-obtained
catalyst.
The effect of the loading amount of cobalt in CuFe
the catalytic activity of Cu1− xCo Fe –G was also investigated. The
results indicated that the large amount of Co has a negative effect on
the activity of Cu1− xCo Fe –G (Table 1, entries 15, 16). Meanwhile,
the catalytic activity of Cu6/7Co1/7Fe /NP–graphene (0.25) and
Cu6/7Co1/7Fe /N–graphene (0.25) were lower than that of Cu6/7
Co1/7Fe –G(0.25) (Table 1, entries 17, 18). Maybe the coordination
effect of NH
was unfavorable for the formation of the crystal structure of CuCoFe
Acknowledgments
2
O
4
–G (0.25) on
This work was financially supported by the National Natural Science
Foundation of China (nos. 31171698, 31471643), the Innovation
Research Program of Department of Education of Hebei for Hebei
Provincial Universities (LJRC009) and the Natural Science Foundation
of Hebei Province (No. B2011204051).
x
2 4
O
x
2 4
O
2
O
4
2
O
4
2 4
O
O and PVP with metal ions (Fe3 , Cu
+
2+
and Co
2+
)
3
·H
2
Appendix A. Supplementary data
2 4
O .
Fig. 4 showed the UV–vis absorption spectra of the reduction of p-
nitroaniline by NaBH4 at various reaction times in the presence of
Cu6/7Co1/7Fe O –G (0.25). The observed peak at 385 nm for the p-
2 4
nitroaniline shows a gradual decrease in intensity with time and a
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.catcom.2014.10.016. These data include MOL files
and InChiKeys of the most important compounds described in this
article.
new peak appeared indicating the formation of p-phenylene di-
2 4
amine. The results indicated that Cu6/7Co1/7Fe O –G (0.25) exhibited
a considerably high activity for the reduction of nitroarenes with
sodium borohydride as the hydrogen donor.
References
[
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Using these newly developed conditions, we explored the scope and
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shown in Table 2, aromatic nitro compounds containing various elec-
trons donating (Table 2, entries 1–6, 10) or electron-withdrawing
groups (Table 2, entries 8, 11) were converted to the corresponding
amino aromatics in good yields and all the reactions could proceed
smoothly. Moreover, the reduction was also successfully carried
out on bulkier molecule such as 1-nitronaphthalene with high yield
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2 4
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2 4
reduction reaction with comparable or higher yield, and relative short
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Cu6/7Co1/7Fe
for the first time. Cu6/7Co1/7Fe
catalyst for the reduction of nitroarenes. The results demonstrate that
the catalytic activity of CuFe –G was enhanced by the combination
of CuFe –G with small amount of cobalt, which can be attributed to
the remarkable synergistic effect between the Cu6/7Co1/7Fe and the
graphene sheets. The Cu6/7Co1/7Fe –G (0.25) catalyst can be readily
2 4
O –G (0.25), was synthesized by a hydrothermal method
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recovered and reused at least five consecutive cycles without significant
loss of its catalytic activity. We believe that this method might be an
important addition to known procedures for reduction of aromatic
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[