Facile fabrication of γ-Fe2O3-nanoparticle modified N-doped porous carbon materials for the efficient hydrogenation of nitroaromatic compounds

Article abstract of DOI:10.1039/c7nj00636e

Novel γ-Fe₂O₃-nanoparticle (NP) modified N-doped porous carbon materials (γ-Fe₂O₃/mCN) were prepared by one-pot pyrolysis of a mixture of melamine, polyacrylonitrile, and FeCl₃·6H₂O at different temperatures. At a pyrolysis temperature of 900 °C, γ-Fe₂O₃/mCN-900-20 exhibited a high surface area and a N content of 8.47%, caused by the complete pyrolysis of melamine and polyacrylonitrile at 900 °C. The obtained material γ-Fe₂O₃/mCN-900-20 was used as a cost-effective catalyst for the hydrogenation of nitrobenzene using N₂H₄·H₂O as the reductant under mild reaction conditions. As compared to other catalysts (e.g., noble metal catalysts), γ-Fe₂O₃/mCN-900-20 exhibited high catalytic performance (TOF of 311.83 h^-1, selectivity of 100%). During the catalytic hydrogenation of nitroaromatic compounds with reducible groups, e.g., alcoholic hydroxyl, halogen, and amino groups, an excellent selectivity close to 100% was achieved. Moreover, because the active sites of γ-Fe₂O₃ has magnetic performance, the catalyst can be easily recovered using a magnet, and reused at least four runs without an obvious activity decrease. Hence, the easily prepared, cost-effective and reusable γ-Fe₂O₃/mCN catalyst fabricated in this study demonstrates potential for applications in selective reduction of aromatic nitro compounds.

Full text of DOI:10.1039/c7nj00636e

View Article Online
View Journal
NJC
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: X. Cui, Q. Zhang,
M. Tian and Z. Dong, New J. Chem., 2017, DOI: 10.1039/C7NJ00636E.
Volume 40 Number
1
January 2016 Pages 1–846
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
NJC
New Journal of Chemistry
www.rsc.org/njc
A journal for new directions in chemistry
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
rsc.li/njc

Page 1 of 18
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ00636E
1
2
Facile fabrication of γ-Fe O -nanoparticle modified N-doped porous carbon materials for
2
3
the efficient hydrogenation of nitroaromatic compounds
3
Xueliang Cui, Qiaolan Zhang, Meng Tian, Zhengping Dong*
4
5
6
7
College of Chemistry and Chemical Engineering, Laboratory of Special Function Materials and
Structure Design of the Ministry of Education, Zhongwei High Technology Research Institute,
Lanzhou University, Lanzhou 730000, PR China.
8
9
Eꢀmail: dongzhp@lzu.edu.cn (Zhengping Dong) Fax: +86 931 8912582; Tel: +86 931 8912577
1
0
Abstract
11
12
13
14
15
16
17
18
19
20
21
22
23
Novel γꢀFe O ꢀnanoparticle (NP) modified Nꢀdoped porous carbon materials (γꢀFe O /mCN)
2
3
2
3
were prepared by the oneꢀpot pyrolysis of a mixture of melamine, polyacrylonitrile, and
FeCl ·6H O at different temperatures. At a pyrolysis temperature of 900°C, γꢀFe O /mCNꢀ900ꢀ
3
2
2
3
20 exhibited a high surface area and a N content of 8.47%, caused by the complete pyrolysis of
melamine and polyacrylonitrile at 900°C. The obtained material γꢀFe O /mCNꢀ900ꢀ20 was used
2
3
as a costꢀeffective catalyst for the hydrogenation of nitrobenzene using N H ·H O as the
2
4
2
reductant under mild reaction condition. As compared to other catalysts (e.g., noble metal
−
1
catalysts), γꢀFe O /mCNꢀ900ꢀ20 exhibited high catalytic performance (TOF of 311.83 h ,
2
3
selectivity of 100%). During the catalytic hydrogenation of nitroaromatic compounds with
reducible groups, e.g., alcoholic hydroxyl, halogen, and amino groups, excellent selectivity of
near 100% was achieved. Moreover, because the active sites γꢀFe O has magnetic performance,
2
3
the catalyst can be easily recovered by a magnet, and reused at least four runs without obvious
activity decrease. Hence, the easily prepared, costꢀeffective and reusable γꢀFe O /mCN catalyst
2
3
1

New Journal of Chemistry
Page 2 of 18
View Article Online
DOI: 10.1039/C7NJ00636E
1
2
3
in this study demonstrates potential applications in selectivity reduction of aromatic nitro
compounds.
4
1 Introduction
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
The chemoselective hydrogenation of nitroaromatic compounds is an essential chemical process
because the hydrogenation products thus obtained, aromatic amines, are important chemical
feedstocks for the synthesis of pharmaceuticals, pesticides, rubber chemicals, photographic
1
, 2
chemicals, surfactant chemicals, and various industrially valuable products. Because the nitro
group of nitroaromatic compounds is very inert, spontaneous hydrogenation under ambient
conditions using a reductant can barely occur. Thus, the transformation of the nitro group to
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
ꢀ5
amino group always occurs with a catalyst. Nobleꢀmetalꢀbased catalysts, such as those of Rh,
Pt, Pd, and Ag, exhibit excellent catalytic activity for the hydrogenation of nitroaromatic
4
, 6ꢀ10
compounds under mild reaction conditions.
However, their scarce resources and high cost
limit largeꢀscale industrial applications. Furthermore, precious metal catalysts, e.g., Pdꢀbased
catalysts, are typically not chemoselective for the catalytic hydrogenation of nitro compounds
1
1, 12
with reducible groups, e.g., aldehyde, halogen, and keto carbonyl groups.
Hence, it is crucial,
albeit challenging, to design and fabricate a desirable catalyst combining high activity, favorable
selectivity, good recyclability, and costꢀeffectiveness.
In the last few years, some heterogeneous catalysts based on abundant transition metals, such
as Co, Ni, and Fe, have been reported to exhibit high activity for the hydrogenation of nitro
1
3ꢀ16
compounds.
The replacement of noble metals with abundant transition metals is key to a
sustainable future as it helps to preserve noble metal resources. Notably, nonꢀprecious metal NPs
are always supported on certain catalyst supports to prevent metal NPs aggregation, subsequently
1
7, 18
enhancing catalytic activity.
In this respect, some recent studies have been reported. For
0
example, Yong Wang’s group has prepared Co ꢀCo O /Nꢀdoped carbon nanotube hybrids as
3
4
efficient and chemoselective catalysts for the hydrogenation of nitroarenes under a H pressure
2
1
9
of 3 MPa. Jiang et al. have reported a metal organic framework (MOF)ꢀderived CoꢀCoO@Nꢀ
2
0
doped porous carbon catalyst for the hydrogenation of nitro compounds. A Ni NPs based
catalysts has also been reported for the chemoselective transfer hydrogenation of nitroarenes and
1
4, 21
catalytic hydrogenation of nitroarenes under high H pressure.
Most recently, Jiang’s group
2
has reported MOFꢀderived γꢀFe O ꢀsupported porous carbon for the efficient and chemoselective
2
3
2

Page 3 of 18
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ00636E
2
2
1
2
3
4
5
6
7
8
9
hydrogenation of nitro compounds. The nonꢀpreciousꢀmetalꢀbased catalysts reported above
exhibit good performance. However, the fabrication of efficient nonꢀpreciousꢀmetalꢀbased based
catalysts for hydrogenation reactions using a simple preparation procedure, inexpensive reagents
and under mild reaction conditions remains highly challenging.
Herein, we prepared a novel costꢀeffective catalyst (γꢀFe O /mCN) by simple oneꢀpot
2
3
pyrolysis. The γꢀFe O /mCN catalyst was obtained by the pyrolysis of a mixture of melamine,
2
3
polyacrylonitrile (PAN), and FeCl . By investigating pyrolysis at different temperatures,
3
melamine not only served as a N precursor, but also helped in the formation of a porous structure
during carbonization. To investigate catalyst performance, the hydrogenation of nitrobenzene
was investigated as the model reaction using N H ·H O as the reductant, and excellent catalytic
1
1
1
1
1
1
1
0
1
2
3
4
5
6
2
4
2
−
1
activity was observed (turnover frequency, TOF, of 311.83 h ). In addition, the catalyst
exhibited remarkable selectivity to nitro compounds with other reducible functional groups.
Moreover, the γꢀFe O /mCNꢀ900ꢀ20 nanocatalyst could also be easily recycled without obvious
2
3
decrease of catalytic activity during four runs. Hence, this study can serve as a guideline for
future studies for the facile preparation of abundant transitionꢀmetalꢀbased reusable supported
catalysts for several applications in the chemical industry.
1
1
7
8
2 Experimental
2.1 Materials
19
20
21
22
23
24
25
26
27
28
29
30
PAN, FeCl ·6H O, and melamine were purchased from Heowns Biochemical Reagent Co. Ltd.
3
2
(Tianjin, China). Nitroaromatic compounds were purchased from Aladdin Reagents. N,Nꢀ
dimethylformamide (DMF) was obtained from Sinopharm Chemical Reagent Co., Ltd. (China).
Distilled water was prepared in our laboratory, and all other reagents were used without further
purification.
2.2 Fabrication of
γ-Fe O /mCN
2 3
The targeted catalyst was prepared by the pyrolysis of a mixture of FeCl ·6H O, PAN, and
3
2
melamine at high temperature. A typical synthetic procedure was described as follows: First, at
100°C, 650 mg of FeCl ·6H O and 2.12 g PAN were dissolved in 50 mL of DMF and vigorously
3
2
stirred for 1 h, affording a homogeneous solution. Second, 20 g of melamine was slowly added,
and vigorous stirring was continued for 2 h to obtain a thick slurry, which was evaporated on a
rotary evaporator and ground into powder. Next, the obtained powder was subjected to pyrolysis
3

New Journal of Chemistry
Page 4 of 18
View Article Online
DOI: 10.1039/C7NJ00636E
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
at 900°C for 0.5 h via programmed heating at 10°C/min under inert atmosphere, affording the γꢀ
Fe O /mCNꢀ900ꢀ20 catalyst.
2
3
To prepare the catalyst under optimal conditions, γꢀFe O /mCNꢀ600ꢀ20, γꢀFe O /mCNꢀ700ꢀ20,
2
3
2
3
and γꢀFe O /mCNꢀ800ꢀ20 were also prepared at pyrolysis temperatures of 600°C, 700°C, and
2
3
800°C, respectively. In addition, γꢀFe O /mCNꢀ900ꢀ5 and γꢀFe O /mCNꢀ900ꢀ10 were prepared
2
3
2
3
by adding 5 g and 10 g of melamine in the preparation procedure, respectively.
2.3 Catalytic hydrogenation of nitrobenzene
The hydrogenation of nitrobenzene was carried out in a twoꢀnecked glass reactor equipped with a
reflux condenser. Typically, 1 mmol of nitrobenzene (123 mg), 10 mg of the γꢀFe O /mCNꢀ900ꢀ
2
3
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
20 catalyst, and 5 mL of ethanol were refluxed at 80°C, followed by the addition of 4 mmol of
N H ·H O using an injection syringe, and the reaction was started. Reaction samples were
2
4
2
collected every 5 min using an injection syringe and filtered, followed by gas chromatography–
mass spectrometry (GCꢀMS, Agilent 5977E) analysis.
To demonstrate the high efficiency of the prepared catalyst, the chemoselective hydrogenation
of different nitro compound substrates was carried out under the same condition as mentioned
above.
2.4 Characterization
Transmission electron microscopy (TEM, FEI Tecnai G2 F30, 200 kV) images were recorded to
observe the morphology of the prepared samples. BrunauerꢀEmmettꢀTeller (BET, Micromeritics
ASAP 2010) measurements were employed to obtain the pore size distributions, surface areas,
and pore volumes of the catalysts. For analyzing the surface electronic states, Xꢀray
photoelectron spectroscopy (XPS, PerkinꢀElmer PHIꢀ5702) was employed. Fourier transform
(FTIR, VERTEX 70, Bruker) spectroscopy was employed to characterize the functional groups
of the samples. Raman spectra were recorded on a Raman spectrometer (Jobin Yvon LabRam
HR evolution). The content of Fe in the prepared nanocatalysts was evaluated by inductively
coupled plasmaꢀatomic emission spectroscopy (ICPꢀAES). To measure the magnetic properties
of the nanocatalyst, a vibrating sample magnetometer (VSM) was utilized at room temperature
by varying the applied magnetic field from ꢀ20 kOe to 20 kOe. GCꢀMS (Agilent 5977E) was also
employed for monitoring the reaction conversion and selectivity.
3
0
4

Page 5 of 18
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ00636E
1
2
Scheme 1. The preparation procedure and the application of the γꢀFe O /mCNꢀ900ꢀ20 catalyst.
2
3
3
3 Results and Discussions
4
5
6
7
8
9
In this study, novel porous γꢀFe O NPs modified Nꢀdoped carbon materials were directly
2
3
prepared in one pot by the pyrolysis of a mixture of melamine, FeCl ·6H O, and PAN. Here,
3
2
during the pyrolysis procedure, the precursor melamine not only induces the fluffy structure but
also modifies the N content and the distribution of N species in the catalysts. On the other hand,
because of the reduction of the carbon, and FeCl was successfully converted to γꢀFe O NPs. To
3
2
3
further investigate the composition of iron and nitrogen, the surface valence states of the
10
11
12
13
14
15
16
17
18
19
20
21
22
23
prepared catalyst (γꢀFe O /mCNꢀ900ꢀ20, initially prepared by adding 20 g melamine, pyrolyzed
2
3
at 900°C) were measured. Fig. 1 shows the XPS spectra of the sample. From the wideꢀrange XPS
spectrum (Fig. 1a), Fe, O, C, and N were present in the prepared samples. The EDS spectrum in
Fig. 1b also shows the composition of the prepared catalysts, which corresponded to the result in
Fig. 1a. Using the C1s peak at 284.6 eV as the reference, two broad peaks of Fe2p3/2 (710.3 eV)
and Fe2p (723.8 eV) were observed in the Fe2p spectrum (Fig. 1c), respectively. The Fe2p
1
/2
3/2
peak was stronger and narrower than the Fe2p1/2 peak, and its area was greater than that of
Fe2p , caused by the four degenerate states of Fe2p as compared to only two degenerate
1
/2
3/2
states of Fe2p1/2 as a result of spinꢀorbit (j−j) coupling. Two satellite peaks were observed at
23
730.1 eV and 714.7 eV, respectively; this result suggested that iron oxide is γꢀFe O NPs. In
2
3
addition, from ICPꢀAES analysis, the γꢀFe O content was 10.26 wt%. As shown in Fig. 1d, the
2
3
split of N1s peaks clearly demonstrated that N 1s exhibits four peaks corresponding to different
N species, pyriclinic N (398.6 eV), graphitic N (401.1 eV), pyrrolic N (400.1 eV), and oxidic N
(402.8 eV) present in 49.4%, 27%, 18% and 5.6%, respectively. Pyridinic N atom existed in the
5

New Journal of Chemistry
Page 6 of 18
View Article Online
DOI: 10.1039/C7NJ00636E
1
2
edges and vacancies of the graphitic carbon layers. According to a previous study, Nꢀdoped
24, 25
carbon materials can create Lewis basic sites, which connect with carbon atoms.
3
4
5
Figure 1. (a) the wideꢀrange XPS spectrum, (b) EDS spectrum, (c) Fe2p spectrum and (d) N1s spectrum of γꢀ
6
Fe O /mCNꢀ900ꢀ20.
2
3
7
8
9
0
1
2
3
4
5
6
7
8
Fig. 2 shows the morphology of the prepared materials. Fig. 2aꢀd exhibits the TEM images of
the γꢀFe O /mCN catalyst after pyrolysis at 900, 800, 700, and 600°C, respectively. γꢀ
2
3
Fe O /mCNꢀ900ꢀ20 (Fig. 2a) shows evident nanosheets constructed porous structure that
2
3
1
1
1
1
1
1
1
1
1
modified by γꢀFe O NPs. While for γꢀFe O /mCNꢀ800ꢀ20 (Fig. 2b), and γꢀFe O /mCNꢀ700ꢀ20
2
3
2
3
2
3
(Fig. 2c), the porous structure is not obvious, and the γꢀFe O /mCNꢀ600ꢀ20 (Fig. 2d) even did
2
3
not exhibit porous structure because melamine plays an important role in forming a porous
structure during pyrolysis. At high temperature (900°C), melamine can be sufficiently pyrolyzed
not only to form the mCN composite but also promote the formation of γꢀFe O NPs. Hence, γꢀ
2
3
Fe O NPs are clearly observed in γꢀFe O /mCNꢀ900ꢀ20 with an average particle size of about 12
2
3
2
3
nm (Fig. 2a), while in γꢀFe O /mCNꢀ800ꢀ20 (Fig. 2b), γꢀFe O /mCNꢀ700ꢀ20 (Fig. 2c), and γꢀ
2
3
2
3
Fe O /mCNꢀ600ꢀ20 (Fig. 2d), γꢀFe O NPs were not clearly observed. The porous structure was
2
3
2
3
not obvious in γꢀFe O /mCNꢀ900ꢀ10 (Fig. 2e) and γꢀFe O /mCNꢀ900ꢀ5 (Fig. 2f) although γꢀ
2
3
2
3
6

Page 7 of 18
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ00636E
1
2
3
4
5
6
7
8
Fe O NPs were clearly observed; this result confirms the significance of the pyrolysis of
2 3
melamine for producing porous structures. To further verify γꢀFe O NPs in detail, HRTEM
2
3
images were recorded. In Fig. 2g, the lattice fringe of (113) for γꢀFe O NPs were clearly
2
3
observed. According to the JCPDS card (no. 25ꢀ1402) for γꢀFe O the dꢀspacing of the
2
3,
reflections was 4.82 Å, affording a lattice fringe of 4.82Å. This result also indicated that the NPs
2
3
are γꢀFe O . Fig. 2h shows the element maps of γꢀFe O /mCNꢀ900ꢀ20: C, O, N, and Fe were
2
3
2
3
well dispersed; especially, N was successfully doped into the carbon materials.
9
1
0
1
1
1
2
1
1
1
3
4
5
Figure 2. TEM image images of (a) γꢀFe O /mCNꢀ900ꢀ20, (b) γꢀFe O /mCNꢀ800ꢀ20, (c) γꢀFe O /mCNꢀ700ꢀ
2
3
2
3
2
3
20, (d) γꢀFe O /mCNꢀ600ꢀ20, (e) γꢀFe O /mCNꢀ900ꢀ10, and (f) γꢀFe O /mCNꢀ900ꢀ5. (g) The γꢀFe O lattice
2
3
2
3
2
3
2
3
fringe of γꢀFe O /mCNꢀ900ꢀ20. (h) The element mapping images of γꢀFe O /mCNꢀ900ꢀ20.
2
3
2
3
1
6
7

New Journal of Chemistry
Page 8 of 18
View Article Online
DOI: 10.1039/C7NJ00636E
1
2
3
4
5
Figure 3. (a) Nitrogen adsorptionꢀdesorption isotherm plots of the obtained γꢀFe O /mCNꢀXꢀ20 materials
2
3
pyrolyzed at different temperatures. (b) Pore size distributions of γꢀFe O /mCNꢀXꢀ20 materials pyrolyzed at
2
3
different temperatures.
6
7
8
9
Figure 4. (a) Raman spectrum and (b) FTꢀIR spectra of γꢀFe O /mCNꢀ900ꢀ20 samples.
2
3
10
11
12
13
14
15
16
The N adsorptionꢀdesorption isotherms of γꢀFe O /mCN at different pyrolysis temperatures
2
2
3
were also measured. Fig. 3a shows the results. All materials exhibited type IV isotherms,
2
6
indicative of mesoporosity. Fig. 3b shows the pore size distribution for all samples. Table S1
summarizes the BET surface area, pore volume, and average pore size of γꢀFe O /mCNꢀ900ꢀ20,
2
3
γꢀFe O /mCNꢀ800ꢀ20, γꢀFe O /mCNꢀ700ꢀ20, and γꢀFe O /mCNꢀ600ꢀ20. γꢀFe O /mCNꢀ900ꢀ20
2
3
2
3
2
3
2
3
2
−1
3
−1
exhibited the highest BET surface area of 216.18 m g , the largest pore volume of 0.39 cm g ,
8

Page 9 of 18
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ00636E
1
2
3
4
5
6
7
8
9
and a pore size of 7.15 nm. From these results, with increasing temperature, the BET surface area
and pore volume gradually increased probably because of the complete pyrolysis of melamine
and PAN at high temperatures. These results are in good agreement with the TEM images, also
indicating that the pyrolysis temperature of melamine is greater than 700°C. The increased
mesoporous structures can provide more exposed γꢀFe O active sites, thereby increasing
2
3
catalytic activity.
Raman spectroscopy is also a useful tool to evaluate carbon materials. Peaks of the D band
−
1
−1
(1580 cm ) and G band (1360 cm ) were clearly observed, suggesting that γꢀFe O /mCNꢀ900ꢀ
2
3
20 is not clearly shifted (Fig. 4a). The G band corresponded to a crystalline and graphitic
2
7
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
structure, while the D band corresponded to defective and distorted carbon layers. The intensity
ratio (I /I ) clearly explained the defect degree of carbon materials. The I /I οf γꢀFe O /mCNꢀ
D
G
D
G
2
3
900ꢀ20 was 1.22, indicating that more defects are present in γꢀFe O /mCNꢀ900ꢀ20. To our
2
3
knowledge, the incorporation of nitrogen atoms into a graphitic network can produce defects in
the graphitic carbon structure. An I /I of 1.22 also explained that N was successfully doped into
D
G
γꢀFe O /mCNꢀ900ꢀ20. FTIR analysis was further carried out to verify functional groups present
2
3
in the melamine mixture (Fig. S1a) and the fresh and reused γꢀFe O /mCNꢀ900ꢀ20 catalysts (Fig.
2
3
−
1
4b). In Fig. S1a, the melamine mixture exhibited organic functional groups (1700 cm to 1500
−
1
−1
−1
cm ) and amino functional groups (3450 cm to 3100 cm ) before carbonization. In Fig. 4b,
−
1
−1
the peak observed at around 610 cm corresponded to Fe–O vibration bond, peaks at 1120 cm
−
1
corresponded to the C–N stretching bond, and those observed at around 3430 cm corresponded
2
8
to the deformation vibration of the N–H bond in the second amine. FTIR results revealed the
presence of CN heterocycles in the mesoporous carbon framework, and also confirmed that the
functional groups in the reused sample have not been obviously changed.
Fig. 5 shows the magnetic property of the γꢀFe O /mCNꢀ900ꢀ20 nanocatalyst at room
2
3
temperature. γꢀFe O /mCNꢀ900ꢀ20 exhibited a saturation magnetization of approximately 5.33
2
3
−
1
emu g , corresponding to magnetic γꢀFe O NPs; this magnetic property is essential to recover
2
3
2
9, 30
the catalyst from the reaction mixture by an external magnetic for reuse.
In addition, Fig. 5
shows the magnetic property of γꢀFe O /mCNꢀ900ꢀ20 recycled after 4 cycles. The saturation
2
3
magnetization for the recycled catalyst did not clearly increase. The inset of Fig. 5 shows the
9

New Journal of Chemistry
Page 10 of 18
View Article Online
DOI: 10.1039/C7NJ00636E
1
2
magnetic separation of γꢀFe O /mCNꢀ900ꢀ20, it can be easily recovered from the reaction
2
3
mixture using an external magnet.
3
4
Figure 5. Roomꢀtemperature magnetization curves of the γꢀFe O /mCNꢀ900ꢀ20 nanocatalyst and the reused
2
3
5
catalyst. Inset is the magnetic separation process of γꢀFe O /mCNꢀ900ꢀ20.
2
3
a
6
Table 1. The catalytic reduction of nitrobenzene with different conditions.
7
8
h
temperature
Conv.
(%)
Sel.
(%)
TOF
(h )
Entry
Catalyst
o
Time (min)
ꢀ1
(
C)
1
2
3
4
5
6
7
8
9
γꢀFe O /mCNꢀ900ꢀ20
80
80
80
80
80
80
80
80
80
80
80
80
55
25
80
80
80
80
80
80
80
30
60
99.98
99.85
91.76
3.29
99.72
61.60
0.34
52.10
97.90
99.83
99.98
99.66
96.99
47.65
1.17
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
311.83
155.71
35.77
1.28
ꢀꢀ
2
3
γꢀFe O /mCNꢀ800ꢀ20
2
3
γꢀFe O /mCNꢀ700ꢀ20
240
240
180
240
240
240
180
60
30
30
240
240
240
30
2
3
γꢀFe O /mCNꢀ600ꢀ20
2
3
γꢀFe O /mCNꢀ900ꢀ10
2
3
γꢀFe O /mCNꢀ900ꢀ5
ꢀꢀ
2
3
b
γꢀFe O /mCNꢀ900ꢀ20
0.13
20.31
50.89
155.68
ꢀꢀ
2
3
c
γꢀFe O /mCNꢀ900ꢀ20
2
3
d
γꢀFe O /mCNꢀ900ꢀ20
2
3
e
10
11
12
13
14
15
16
17
18
19
20
21
γꢀFe O /mCNꢀ900ꢀ20
2
3
f
γꢀFe O /mCNꢀ900ꢀ20
2
3
g
γꢀFe O /mCNꢀ900ꢀ20
ꢀꢀ
2
3
γꢀFe O /mCNꢀ900ꢀ20
37.82
18.58
0.46
8.48
0.34
10.88
64.5
21.73
22.70
2
3
γꢀFe O /mCNꢀ900ꢀ20
2
3
none
Fe O4
2.72
0.11
3.49
20.69
6.97
3
αꢀFe O3
30
30
30
30
2
γꢀFe O3
2
γꢀFe O /AC
2
3
γꢀFe O /SiO
2
3
2
γꢀFe O /Al O
30
7.28
2
3
2
3
10

Page 11 of 18
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ00636E
a
1
2
3
Reaction conditions: 1 mmol nitrobenzene, 10 mg γꢀFe O ꢀbased catalyst, 4 mmol N H ·H O, and 5 mL
b c d e
2
3
2
4
2
ethanol unless otherwise mentioned; without N H ·H O; 1 mmol N H ·H O; 2 mmol N H ·H O; water as
the reaction solution; pyrolysis for 1 hour; pyrolysis for 2 hours. TurnoverꢀfrequencyꢀꢁTOFꢂ =
2
4
2
2
4
2
2
4
2
f
g
h
ꢃꢄꢅꢆꢇꢀꢄꢈꢀꢉꢄꢊꢋꢆꢌꢍꢆꢎꢀꢇꢏꢐꢇꢍꢌꢑꢍꢆ
4
ꢃꢄꢅꢆꢇꢀꢄꢈꢀꢒꢓꢔꢆ ꢖ ×ꢀꢌꢆꢑꢉꢍꢘꢄꢊꢀꢍꢘꢃꢆꢁꢙꢂ
ꢕ
ꢗ
5
6
7
8
9
The catalytic activity of the prepared γꢀFe O /mCNꢀ900ꢀ20 was investigated for the
2
3
hydrogenation of nitrobenzene as the model reaction using N H ·H O as the reductant and
2
4
2
ethanol as the solvent. Table 1 summarizes the different reaction conditions for the
hydrogenation of nitrobenzene. As shown in entries 1–4 of Table 1, γꢀFe O /mCN catalysts
2
3
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
prepared at different pyrolysis temperatures were investigated to compare the effect of pyrolysis
temperature on the catalytic activity. The catalytic activity remarkably changed with
temperatures. At a pyrolysis temperature of 900°C, γꢀFe O /mCNꢀ900ꢀ20 exhibited the highest
2
3
−
1
catalytic activity (TOF of 311.83 h ). Meanwhile, different melamineꢀdosed derived materials
(γꢀFe O /mCNꢀ900ꢀ10 and γꢀFe O /mCNꢀ900ꢀ5) were also measured (entries 5, 6, respectively).
2
3
2
3
The results showed that the melamine dose significantly affects the catalytic activity of γꢀ
Fe O /mCN because the pyrolysis of melamine produces porous structures and exposes more
2
3
active sites in γꢀFe O Hence, γꢀFe O /mCNꢀ900ꢀ20 exhibits a better catalytic activity than γꢀ
2
3.
2
3
Fe O /mCNꢀ900ꢀ10 and γꢀFe O /mCNꢀ900ꢀ5. From entries 7–9, representing different doses of
2
3
2
3
N H ·H O, with increasing N H ·H O concentration, TOF increased. When 4 equivalents of
2
4
2
2
4
2
−
1
N H ·H O to nitrobenzene was used, the highest TOF of 311.83 h was obtained. With the use
2
4
2
of distilled water as the solution, the catalyst exhibited very good activity with a TOF of 155.68
−
1
h although it was difficult to disperse carbon materials into distilled water (entry 10). As shown
in entries 11–12, different pyrolysis times of the prepared catalysts were also studied (1 and 2 h),
but the results indicated that pyrolysis time is not important for catalytic activity. Lower reaction
temperatures of 55°C and 25°C (entries 13, 14, respectively) also afforded low conversion for
the catalytic reaction; hence, the best temperature for this reaction is 80°C. When a reductant was
used without the catalyst, hydrogenation almost did not occur (entry 15). To further confirm the
catalytic active sites, unsupported Fe O and αꢀFe O were also used as catalysts for the
3
4
2
3
hydrogenation of nitrobenzene (entries 16 and 17), and both reactions afforded very low TOF.
According to the result, γꢀFe O is the catalytic active sites for the hydrogenation of nitrobenzene.
2
3
To demonstrate the superiority of the catalyst support mCN, unsupported γꢀFe O was also used
2
3
11

New Journal of Chemistry
Page 12 of 18
View Article Online
DOI: 10.1039/C7NJ00636E
−
1
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
for the hydrogenation of nitrobenzene, and as shown in entry 18, the TOF was only 10.88 h ,
which is significantly less than that obtained using γꢀFe O /mCNꢀ900ꢀ20; hence, mCN
2
3
considerably improves the catalytic activity of γꢀFe O , caused by the porous structure and N. On
2
3
the other hand, for γꢀFe O /AC, γꢀFe O /SiO , γꢀFe O /Al O catalysts, prepared using different
2
3
2
3
2
2
3
2
3
supports for γꢀFe O , e.g., activated carbon (AC), SiO , and Al O , respectively, were utilized
2
3
2
2
3
under the same conditions (entries 19–21, respectively), mCN materials were superior to those of
AC, SiO , and Al O . Thus, Nꢀdoped carbon supports can promote the catalytic activity of
2
2
3
hydrogenation.
Previous studies reporting the hydrogenation of nitrobenzene using different catalysts have
been summarized and listed in Table 2. Compared with other studies, a significantly high TOF
was obtained using γꢀFe O /mCNꢀ900ꢀ20 as the catalyst in this study. Although Pdꢀbased
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
3
catalysts are well known for hydrogenation, especially for the hydrogenation of nitrobenzene, as
0
0
listed in Table 2 entries 2ꢀ3, for the reported Pd based catalysts such as Pd /γꢀFe O and
2
3
−
1
Pd/HAM@γꢀAlOOH in the hydrogenation of nitrobenzene, the TOF values were only 150 h
−
1
8, 31
and 98.05 h , respectively.
On the other hand, the reported Rh catalyst Rh–Fe O (Table 2,
3 4
entries 4ꢀ5) under the same conditions of N H ·H O as the reductant and reflux at 80°C also
2
4
2
3
2, 33
exhibited lower TOF values.
Furthermore, other recently reported γꢀFe O ꢀbased catalyst
2
3
ꢀ1
was also listed in entry 6 and just has a TOF number of 40 h for hydrogenation of
2
2
19
nitrobenzene. Other abundant transition metals based catalysts, for example CoOx@NCNTs
3
4
and CoꢀSiCN, can also hydrogenate the nitrobenzene to aniline at high H pressure with TOF
2
ꢀ1
numbers of 8.3 and 1.4 h , respectively. However, the reported Ru/CMKꢀ3 catalyst that also can
catalyze hydrogenation the nitroarenes using N H ·H O as reductant exhibits a higher TOF of
2
4
2
ꢀ1 35
1339 h . This is probably due to the noble metal Ru based catalysts should exhibit high
catalytic activity as compared with nonꢀnoble metal based catalysts in hydrogenation reactions.
Even so, the prepared γꢀFe O /mCNꢀ900ꢀ20 catalyst in this work still exhibited excellent
2
3
catalytic activity. On the other hand, it is easy to prepare γꢀFe O /mCNꢀ900ꢀ20 as compared to
2
3
27
28
29
other reported catalysts. The results also indicated that γꢀFe O with active performance is
2
3
optimum for replacing noble catalysts for the hydrogenation of nitrobenzene.
3
0
12

Page 13 of 18
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ00636E
1
Table 2. Comparation of the catalytic activity with other reported catalysts.
Catalytic
active site
ꢀ1 a
Entry
1
Samples
Reaction Conditions TOF (h )
Ref.
o
This
work
31
8
32
33
22
19
34
γꢀFe O /mCNꢀ900ꢀ20
γꢀFe O
N H ·H O, 80 C
2
4
2
311.83
2
3
2
3
0
2
3
4
5
6
7
8
Pd @γꢀFe O
Pd
Pd
Rh
Rh
1 atm H , RT
150
98.05
39.6
99
40
8.3
2
3
2
Pd/HAM@γꢀAlOOH
Rh catalyst
1 atm H , RT
2
o
N H ·H O, 80 C
2
4
2
o
RhꢀF e O4
N H ·H O, 80 C
3
2
4
2
o
Feꢀ500ꢀ1 h
CoOx@NCNTs
CoꢀSiCN
γꢀFe O
N H ·H O, 80 C
2
3
2
4
2
o
CoOx
Co
3 MPa H , 110 C
2
o
5 MPa H , 110 C
1.4
2
o
9
Ru/CMKꢀ3
Ru/CMKꢀ3
N H ·H O, 30 C
1339
35
2
4
2
a
ꢃꢄꢅꢆꢇꢀꢄꢈꢀꢉꢄꢊꢋꢆꢌꢍꢆꢎꢀꢇꢏꢐꢇꢍꢌꢑꢍꢆ
2
TurnoverꢀfrequencyꢀꢁTOFꢂ =
ꢃꢄꢅꢆꢇꢀꢄꢈꢀꢑꢉꢍꢘꢋꢆꢀꢇꢘꢍꢆꢇ×ꢀꢌꢆꢑꢉꢍꢘꢄꢊꢀꢍꢘꢃꢆꢁꢙꢂ
3
4
5
6
7
8
9
Scheme 2 shows the reaction mechanism for the γꢀFe O /mCNꢀ900ꢀ20ꢀcatalyzed
2
3
hydrogenation of nitrobenzene: First, nitrobenzene and N H ·H O were absorbed on the porous
2
4
2
structure of mCN. Second, N H ·H O was attached to the surface of γꢀFe O NPs and dissociated
2
4
2
2
3
into two hydrogen ions and electrons. The hydrogen ions and electrons were captured by
nitrobenzene, forming nitrosobenzene. Nitrosobenzene might rapidly convert to
phenylhydroxylamine via hydrogenation. During the reaction, a trace amount of
phenylhydroxylamine was detected. Because of the poor stability of phenylhydroxylamine, under
22, 36
10
11
12
hydrogen ion conditions, phenylhydroxylamine can be easily decomposed to aniline.
N H ·H O finally dissociates to N and H O without other byꢀproducts, thus the catalytic process
2
4
2
2
2
is environmentally friendly.
1
3
4
1
Scheme 2. The possible reaction mechanism for hydrogenation of nitrobenzene to aniline.
1
1
1
5
6
7
13

New Journal of Chemistry
Page 14 of 18
View Article Online
DOI: 10.1039/C7NJ00636E
a
1
2
Table 3. The catalytic hydrogenation of aromatic nitrocompounds to their amines with γꢀFe O /mCNꢀ900ꢀ20 .
2
3
Time
ꢀ1 b
Entry
Substrate
Product
Conv. (%)
99.7
Sel. (%)
100
TOF (h )
(min)
1
2
3
I
NO
NO
NO
2
I
NH
2
40
233.22
311.27
467.38
Br
2
Br
NH
30
20
10
99.8
99.9
99.9
100
100
100
2
Cl
Cl
2
Cl
Cl
NH
2
4
5
6
934.76
465.04
934.76
NO
2
NH2
Br
Br
20
10
99.5
99.9
100
100
NO
2
NH
2
Cl
Br
Cl
NO
2
NH
2
Br
7
8
9
20
50
60
99.6
99.8
99.9
100
100
100
465.98
186.77
154.39
NO
2
NH2
HO
HO
NO
2
HO
HO
NH
2
NO
2
NH2
OH
OH
1
1
1
0
1
2
50
20
10
99.6
99.9
99.9
100
100
96.2
186.39
476.38
900.14
NO2
NH2
HOOC
NO
2
HOOC
COOH
NH
2
COOH
NO2
NH
COC
HO
2
1
1
1
3
4
5
H
3
COC
HO
H2N
NO
NO
NO2
2
H
3
NH
NH
NO
2
40
10
60
99.7
99.9
99.0
99.6
100
100
232.29
934.76
154.39
S
3
S
2
3
2
H
2
N
2
NH
2
NH2
NH
1
1
6
7
50
30
99.1
99.8
100
100
195.46
311.28
NO
2
2
H
3
C
NO
2
H
3
C
NH
2
a
3
4
Reaction conditions: 1 mmol substrate, 10 mg γꢀFe O /mCNꢀ900ꢀ20 catalyst, 4 mmol N H ·H O, and 5
2
3
2
4
2
o
mL ethanol, reflux at 80 C unless otherwise mentioned.
b
ꢃꢄꢅꢆꢇꢀꢄꢈꢀꢉꢄꢊꢋꢆꢌꢍꢆꢎꢀꢇꢏꢐꢇꢍꢌꢑꢍꢆ
TurnoverꢀfrequencyꢀꢁTOFꢂ =
ꢃꢄꢅꢆꢇꢀꢄꢈꢀꢒꢓꢔꢆ ꢖ ×ꢀꢌꢆꢑꢉꢍꢘꢄꢊꢀꢍꢘꢃꢆꢁꢙꢂ
5
6
ꢕ
ꢗ
7
8
9
0
1
2
In this study, to investigate the general applicability of γꢀFe O /mCNꢀ900ꢀ20, various
2
3
nitroaromatic compounds were hydrogenated under the optimized conditions (1 mmol nitro
compounds, 10 mg of γꢀFe O /mCNꢀ900ꢀ20, 4 mmol of N H ·H O, and refluxed at 80°C). Table
2
3
2
4
2
1
1
1
3 summarizes the results obtained from the hydrogenation of nitroaromatic compounds,
indicating that most nitro compounds are converted to the corresponding substituted anilines
with high conversion and almost 100% selectivity. The hydrogenation of different halogenꢀ
14

Page 15 of 18
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ00636E
1
2
3
4
5
6
7
8
9
substituted nitro compounds was carried out, with almost 100% selectivity and very high TOF
(entries 1–3). The hydrogenation of nitro compounds with halogen at different substituent
position (entries 4–7) was also carried out, with high TOF numbers and approximately 100%
selectivity. Thus, irrespective of the halogen and substituent position, for the hydrogenation of
halogenꢀsubstituted nitro compounds, γꢀFe O /mCNꢀ900ꢀ20 effectively and selectivity converted
2
3
nitro to the corresponding halogenꢀsubstituted anilines without obvious dehalogenation.
However, most of the nobleꢀmetalꢀbased catalysts in the catalyzed hydrogenation of halogenꢀ
3
7ꢀ39
substituted nitro compounds always accompanies with dehalogenation.
Thus, the catalytic
activity of γꢀFe O /mCNꢀ900ꢀ20 was found to be superior to those of some nobleꢀmetalꢀbased
2
3
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
catalysts. Furthermore, high conversion and selectivity were also observed in the hydrogenation
of nitro compounds with other reducible groups, e.g., alcohol hydroxyl (entries 8ꢀ10), carboxyl
(entries 11, 12), ketone (entry 13), sulfur (entry 14), and amino (entries 15, 16). Different
−
1
−1
−1
position of hydroxyl substituents afforded TOF values of 186.77 h , 154.39 h , and 186.39 h ,
with a selectivity of greater than 99.9% (entries 8ꢀ10). pꢀNitrobenzoic acid was subjected to
hydrogenation, affording pꢀaminobenzoic acid with a selectivity of greater than 99.9% and very
high TOF (entry 11). oꢀNitrobenzoic acid (entry 12) also underwent hydrogenation; however,
because of the condensation of carboxyl and ortho amino group, a lower selectivity of
approximately 96.2% was observed for the hydrogenation of oꢀnitrobenzonic acid to oꢀ
aminobenzoic acid. The hydrogenation of ketone and sulfur (entries 13 and 14, respectively)
exhibited almost 100% selectivity without the reduction of other functional groups. The
hydrogenation of amino (entries 15 and 16) at the paraꢀ and orthoꢀ position afforded TOF values
−
1
of 154.39 and 195.46 h , respectively. γꢀFe O /mCNꢀ900ꢀ20 also exhibited high catalytic
2
3
activity in the hydrogenation of methylꢀsubstituted nitrobenzene with a conversion of 99.8% and
selectivity of 99.9% (entry 17). γꢀFe O /mCNꢀ900ꢀ20 for the hydrogenation of nitro compounds
2
3
further led to the excellent chemoselectivity of γꢀFe O ꢀbased catalyst, again manifesting that γꢀ
2
3
Fe O /mCNꢀ900ꢀ20 is effective for the hydrogenation of nitro compounds.
2
3
Finally, the recyclability and reusability of γꢀFe O /mCNꢀ900ꢀ20 were investigated for the
2
3
hydrogenation of nitrobenzene. Fig. 6 shows the results obtained from the recycling experiments.
After four recycle runs, the conversion for the hydrogenation of nitrobenzene slightly decreased.
From ICPꢀAES analysis, the γꢀFe O content slightly decreased from the original 10.26 wt% to
2
3
10.07 wt%, which possibly leads to the slight decrease of the catalytic activity. On the other
15

New Journal of Chemistry
Page 16 of 18
View Article Online
DOI: 10.1039/C7NJ00636E
1
2
3
hand, from the FTIR (Fig. 4b), TEM (Fig. S2) and BET (Fig. S3) measurements of the recycled
catalyst, the reused γꢀFe O /mCNꢀ900ꢀ20 catalyst almost retains its morphology and porous
2
3
structure, indicative of its stability.
4
5
6
Figure 6. Recycle of the catalyst. Reaction conditions: 1 mmol substrate, 10 mg γꢀFe O /mCNꢀ900ꢀ20
catalyst, 4 mmol N H ·H O, and 5 mL ethanol, reflux at 80 C.
2 4 2
2
3
o
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
4 Conclusions
In this study, γꢀFe O /mCN catalysts were prepared using melamine and polyacrylonitrile as
2
3
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
the Nꢀdoped carbon source and FeCl as the metal oxide source. At high temperature (900 °C)
3
and inert atmosphere, the pyrolysis of melamine and polyacrylonitrile formed a porous mCN
structure. Meanwhile, FeCl formed γꢀFe O NPs, which were supported on mCN and played an
3
2
3
important role in the catalytic hydrogenation of nitro compounds. Using nitrobenzene as a model
compound, the γꢀFe O /mCNꢀ900ꢀ20 catalyst exhibited excellent hydrogenation activity. The
2
3
yield and selectivity of the product aniline were almost 100% at 80 °C for 30 min using
N H ·H O as the reductant. The reaction process is mild and only has N and H O as the byꢀ
2
4
2
2
2
products, thus the catalytic process is environmentally friendly. The catalytic activity of γꢀ
Fe O /mCNꢀ900ꢀ20 was superior to that of other nobleꢀmetalꢀbased catalysts. Moreover, the γꢀ
2
3
Fe O /mCNꢀ900ꢀ20 catalyst exhibited high hydrogenation activity for nitroaromatic compounds,
2
3
especially for nitroaromatic compounds with reducible groups: the selectivity of the
corresponding functional aniline was almost 100%. Furthermore, the γꢀFe O /mCNꢀ900ꢀ20
2
3
catalyst can also be easily recycled and reused with good stability. So in this work, we not only
prepared a costꢀeffective Nꢀdoped catalyst by a simple method, but also provided an effective
way to selectivity reduction of aromatic nitro compounds.
16

Page 17 of 18
New Journal of Chemistry
View Article Online
DOI: 10.1039/C7NJ00636E
1
2
Acknowledgement
3
4
5
This work is supported by the Fundamental Research Funds for the Central Universities
(lzujbkyꢀ2017ꢀ112 and lzujbkyꢀ2014ꢀ177) and the Science and Technology Plan Projects of
Lanzhou City (2015ꢀ3ꢀ61).
6
7
Supporting Information
Supplementary data associated with this article can be found, in the online version.
8
9
References
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
1.
2.
O. Beswick, D. Lamey, F. Muriset, T. LaGrange, L. Oberson, S. Yoon, E. Sulman, P. J.
Dyson and L. KiwiꢀMinsker, Catal. Today, 2016, 273, 244ꢀ251.
S. Zhang, C.ꢀR. Chang, Z.ꢀQ. Huang, J. Li, Z. Wu, Y. Ma, Z. Zhang, Y. Wang and Y. Qu,
J. Am. Chem. Soc., 2016, 138, 2629ꢀ2637.
H. Fang, M. Wen, H. Chen, Q. Wu and W. Li, Nanoscale, 2016, 8, 536ꢀ542.
M. Turáková, M. Králik, P. Lehocký, Ľ. Pikna, M. Smrčová, D. Remeteiová and A.
Hudák, Appl. Catal. A: General, 2014, 476, 103ꢀ112.
N. M. Patil, T. Sasaki and B. M. Bhanage, Acs Sustain. Chem. Eng., 2016, 4, 429ꢀ436.
S. Cai, H. Duan, H. Rong, D. Wang, L. Li, W. He and Y. Li, ACS Catal., 2013, 3, 608ꢀ
612.
W. Du, G. Chen, R. Nie, Y. Li and Z. Hou, Catal. Commun., 2013, 41, 56ꢀ59.
M. Tian, X. Cui, C. Dong and Z. Dong, Appl. Surf. Sci., 2016, 390, 100ꢀ106.
A. Shukla, R. K. Singha, T. Sasaki and R. Bal, Green Chem., 2015, 17, 785ꢀ790.
T. Ji, L. Chen, L. Mu, R. Yuan, M. Knoblauch, F. S. Bao and J. Zhu, Appl. Catal. B:
Environ., 2016, 182, 306ꢀ315.
A. H. Pizarro, C. B. Molina, J. A. Casas and J. J. Rodriguez, Appl. Catal. B: Environ.,
2014, 158–159, 175ꢀ181.
H. Liu, K. Tao, C. Xiong and S. Zhou, Catal. Sci. Technol., 2015, 5, 405ꢀ414.
T. Wang, Z. Dong, T. Fu, Y. Zhao, T. Wang, Y. Wang, Y. Chen, B. Han and W. Ding,
Chem. Commun., 2015, 51, 17712ꢀ17715.
C. J. Jiang, Z. Y. Shang and X. H. Liang, ACS Catal., 2015, 5, 4814ꢀ4818.
B. Yang, Q. Zhang, X. Ma, J. Kang, J. Shi and B. Tang, Nano Research, 2016, 9, 1879ꢀ
1890.
R. V. Jagadeesh, A.ꢀE. Surkus, H. Junge, M.ꢀM. Pohl, J. Radnik, J. Rabeah, H. Huan, V.
Schuenemann, A. Brueckner and M. Beller, Science, 2013, 342, 1073ꢀ1076.
M. N. Pahalagedara, L. R. Pahalagedara, J. He, R. Miao, B. Gottlieb, D. Rathnayake and
S. L. Suib, J. Catal., 2016, 336, 41ꢀ48.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
17

New Journal of Chemistry
Page 18 of 18
View Article Online
DOI: 10.1039/C7NJ00636E
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
18.
19.
V. Iablokov, Y. Xiang, A. Meffre, P.ꢀF. Fazzini, B. Chaudret and N. Kruse, ACS Catal.,
2016, 6, 2496ꢀ2500.
Z. Wei, J. Wang, S. Mao, D. Su, H. Jin, Y. Wang, F. Xu, H. Li and Y. Wang, ACS Catal.,
2015, 5, 4783ꢀ4789.
X. Ma, Y.ꢀX. Zhou, H. Liu, Y. Li and H.ꢀL. Jiang, Chem. Commun., 2016, 52, 7719ꢀ7722.
Y. Zheng, K. Ma, H. Wang, X. Sun, J. Jiang, C. Wang, R. Li and J. Ma, Catal. Lett.,
2008, 124, 268ꢀ276.
Y. Li, Y.ꢀX. Zhou, X. Ma and H.ꢀL. Jiang, Chem. Commun., 2016, 52, 4199ꢀ4202.
Q. Peng, J. Gan, S. Wang, L. Kong, G. Chen, Y. Yang and G. Huang, Ind. Eng. Chem.
Res., 2013, 52, 7713ꢀ7717.
D. Guo, R. Shibuya, C. Akiba, S. Saji, T. Kondo and J. Nakamura, Science, 2016, 351,
361ꢀ365.
S.ꢀi. Fujita, A. Katagiri, H. Watanabe, S. Asano, H. Yoshida and M. Arai, Chemcatchem,
2015, 7, 2965ꢀ2970.
L. Liang, Q. Zhu, T. Wang, F. Wang, J. Ma, L. Jing and J. Sun, Micropor. Mesopor.
Mater., 2014, 197, 221ꢀ228.
R. Wu, S. Chen, Y. Zhang, Y. Wang, Y. Nie, W. Ding, X. Qi and Z. Wei, J. Mater. Chem.
A, 2016, 4, 2433ꢀ2437.
J. Zhang, T. Yao, H. Zhang, X. Zhang and J. Wu, Nanoscale, 2016, 8, 18693ꢀ18702.
R. Xiong, Y. Wang, X. Zhang, C. Lu and L. Lan, Rsc Adv., 2014, 4, 6454ꢀ6462.
G. K. Larsen, W. Farr and S. E. Hunyadi Murph, J. Phys. Chem. C, 2016, 120, 15162ꢀ
15172.
C.ꢀH. Pélisson, A. DenicourtꢀNowicki, C. Meriadec, J.ꢀM. Greneche and A. Roucoux,
Chemcatchem, 2015, 7, 309ꢀ315.
M. Shokouhimehr, J. E. Lee, S. I. Han and T. Hyeon, Chem. Commun., 2013, 49, 4779ꢀ
4781.
Y. Jang, S. Kim, S. W. Jun, B. H. Kim, S. Hwang, I. K. Song, B. M. Kim and T. Hyeon,
Chem. Commun., 2011, 47, 3601ꢀ3603.
T. Schwob and R. Kempe, Angew. Chem. Int. Edit., 2016, 55, 15175ꢀ15179.
J. Hu, Y. Ding, H. Zhang, P. Wu and X. Li, Rsc Adv., 2016, 6, 3235ꢀ3242.
R. V. Jagadeesh, T. Stemmler, A.ꢀE. Surkus, H. Junge, K. Junge and M. Beller, Nat.
Protocols, 2015, 10, 548ꢀ557.
F. Leng, I. C. Gerber, P. Lecante, S. Moldovan, M. Girleanu, M. R. Axet and P. Serp,
ACS Catal., 2016, 6, 6018ꢀ6024.
O. Verho, K. P. J. Gustafson, A. Nagendiran, C.ꢀW. Tai and J.ꢀE. Bäckvall,
Chemcatchem, 2014, 6, 3153ꢀ3159.
G. Fan and Y. Wang, Synth React Inorg M, 2014, 44, 967ꢀ973.
20.
21.
22.
23.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
3
8
18