Metal-free nitrogen -doped carbon nanosheets: A catalyst for the direct synthesis of imines under mild conditions

Article abstract of DOI:10.1039/c9gc00908f

Herein, a highly stable, porous, multifunctional and metal-free catalyst was developed, which exhibited significant catalytic performance in the oxidation of amines and transfer hydrogenation of nitriles under mild conditions; this could be attributed to the presence of numerous active sites and their outstanding BET surface area. The obtained results showed that most of the yields of imines exceeded 90%, and the cycling performance of the catalyst could be at least seven runs without any decay in the reaction activity, which could be comparable to those of metal catalysts. Subsequently, a kinetic study has demonstrated that the apparent activation energy for the direct synthesis of imines from amines is 67.39 kJ mol^-1, which has been performed to testify that the catalytic performances are rational. Via catalyst characterizations and experimental data, graphitic-N has been proven to be the active site of the catalyst. Hence, this study is beneficial to comprehend the mechanism of action of a metal-free N-doped carbon catalyst in the formation of imines.

Full text of DOI:10.1039/c9gc00908f

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The metal-free nitrogen-doped carbon nanosheets: a catalyst for directly
synthesis imines under mild conditions
Received 00th
January 20xx,
Accepted 00th
January 20xx
Kaizhi Wang , Pengbo Jiang , Ming Yang , Ping Ma , Jiaheng Qin a,b, Xiaokang
a,b
a,b
a,b
a,b
a,b
a,b
a,b
Huang , Lei Ma , and Rong Li*
A highly stable, porous multifunctional and metal-free catalyst was explored to exhibit a
remarkable catalytic performance in the oxidation of amines and transfer hydrogenation of
nitriles reaction under the mild conditions, which was owing to the plenty of active sites and
outstanding BET surface area. The results showed that most of the yields of imines were over
DOI:
1
x
0.1039/x0xx00000
9
0 %, and the cycling performance of the catalyst could be at least seven runs without reaction
www.rsc.org/
activity decay, which could be comparable with those metal catalysts. Subsequently, the
kinetic study was demonstrated that the apparent activation for the direct synthesis of imine
from amine is 67.39 kJ/mol, which also performed to testify the catalytic performances were
rational. Through the catalyst characterizations and experimental data, graphitic-N has been
proven to be the active sites of the catalyst. Hence, the work is beneficial to comprehend the
mechanism of the metal-free N-doped carbon catalyst for resultant imines.
doped heteroatoms (e.g., B , N , O , P17, 18, and
S15, 19) into carbon. In particular, the doping of N
heteroatoms in carbon materials has attracted
extensive research. It is recognized that the atomic
radii, bond length, and coordination ability of
carbon atoms and heteroatoms are different, which
leads to the generation of plentiful defect sites,
changes in electron delocalization, and transforms
in electronic properties.20-22 Meanwhile, carbon
materials own greatly stable and eco-friendly
performance, and thereby it is the good choice for
industry as heterogeneous catalysts. Therefore,
highly efficient green metal-free carbon-based
7
, 8
9-15
16
1
. Introduction
So far, a great diversity of carbon materials are
being developed for the applications, i.e., applying
to industrial catalysis, super-capacitor, electro-
1
catalysis and so on. As is well known, whether a
carbon material owns outstanding performance
depends on the framework construction, such as
activated carbon2, carbon nanotubes (CNTs)3, 4,
5
6
graphene oxide (GO) , microporous carbon , and
a
State Key Laboratory of Applied Organic Chemistry (SKLAOC).b College of
Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, PR
China. E-mail: liyirong@lzu.edu.cn; Fax: +86-931-891-2582; Tel: +86-18919803060
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catalysts should be widely used in industrial chemisterilants, polymers, medicines, a
V
n
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n
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a
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n
li
ne
DOI: 10.1039/C9GC00908F
processes. For example, the replacement of today's products.28-30 Therefore, applications and synthetic
noble metal (Pd-C23 or Ru-C ) heterogeneous routes of imines are fundamentally demanding
catalysts with metal-free catalysts can significantly research subjects in the chemistry field.31-33
eliminate the environmental pollution problems Generally speaking, imines are formed by the
caused by metal leaching in the pharmaceutical and oxidation of alcohols and amines29, 34, the self-
petroleum industry. Importantly, the significantly oxidation of primary amines16, 35, and the self-
24
3
6
catalytic characteristics of formerly reported N- oxidation of second amines , these are the
doped carbon materials could guarantee that their economical, efficient, green and sustainable
catalytic effect were comparable to the metal doped synthesis methods. In addition, the self-oxidation of
catalysts.25-27 Recently, the metal-free mesoporous primary amines are usually catalyzed by the doped-
3
5
36
carbon synthesized from macrocyclic compounds metal catalysts, such as Pd/Al O , Ru , Au
2
3
2
8
37
38
39
40
41
provided by Chen has undergone a cumbersome NPs , Ce/SiO , Cu , Fe/MOF , Co , and so on.
2
4
2
and toxic preparation process using silica colloid as However, for example, J. Yang et al. had reported
a template. And the disadvantage of the oxygen- Au/TiO2 nanospheres for oxidative coupling
rich carbon quantum dots reported by Ye16 as a reactions of amines by visible-light, but the cycling
catalyst was that the synthetic process was not in test of the catalyst and the conversion to the
line with the theme of green chemistry. In a word, product were not very good. Besides, the metal ion
although these reported catalysts have good results leaching of the catalyst in the reaction system has a
for the conversion of benzylamine to imine, it is great influence on the activity of the catalyst and
necessary to explore a more economical and the separation of the product. Furthermore, nitrile
environmentally friendly catalytic reaction system. compounds also play a significant role in the field
Hence, two-dimensional mesoporous N-doped of pharmacological, functional organic chemistry
carbon (NC) has been designed to direct synthesis and biological.43 Typically, based on the earlier
of imines from amines and transfer hydrogenation literature, synthesis amides, aldehydes and amines
of nitriles, respectively.
by controlling additives types for transfer
hydrogenation of nitriles are considered an
As mentioned above, the NC materials could be effective and green method.43-47 However, though
applied to synthesize more significant chemical many excellent reaction systems regarding with
compounds that contained C=N bonds, which were transfer hydrogenation of nitriles have been
called imines. Imines are a crucial classification of reported, these processes mentioned above still
nitrogen sources, since it can be farther employed required the metal species as activity sites to induce
as functional organic products, liking dyestuffs, the reaction. Similarly, these metal supported
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catalysts also had poor circulation and 2. Experimental
View Article Online
DOI: 10.1039/C9GC00908F
recyclability. Thus, it is highly desirable to develop
2
.1. Reagents and chemicals
a facile, green, efficient and sustainable method for
the formation of imines and other chemical
All reagents and chemicals were of analytical grade
and used as received without any further
purification. 3-Aminophenol (C H NO, 98%) was
products.
Herein,
the
highly
efficient
multifunctional NC nanosheets catalyst system for
the synthesis of imines and transfer hydrogenation
of nitriles under mild and controllable conditions
was reported. The results confirmed that the
catalyst for heterogeneous catalysis was
synthesized successfully with a remarkably
catalytic effect. Based on the application and
characterization of the NC catalyst, graphitic-N
was proved as the active sites which formed under
its designated prepared temperature. The data
obtained after repeated experiment showed that
most of the yields of imines were more than 90 %.
Cycling performance can be remained at least
seven runs without reaction activity decay, which
was comparable to the activity of those metal
catalysts. Subsequently, the kinetic study was also
carried out to testify the catalytic performances
were rational. In a word, a green, highly-efficient
and sustainable catalyst for resultant imines and
transfer hydrogenation nitriles reaction were
investigated, and it is beneficial to comprehend the
mechanism of the metal-free N-doped carbon
catalyst for resultant imines in this work.
6
7
purchased from Shanghai McLean biochemical
technology co., Ltd. Formaldehyde Solution
(
HCHO, 37%) was purchased from Tianjin Da Mao
chemical reagents factory. Melamine
C N (NH ) ), Graphite powder and Potassium
(
3
3
2 3
carbonate (K CO ) were purchased from
2
3
Sinopharm Chemical Reagents Co., Ltd.
.2. Synthesis of the catalyst of porous N-doped
2
carbon (NC)
For the synthesis of the porous N-doped carbon
nanosheets, 3-Aminophenol, ethanol and deionized
water were thoroughly dissolved in a 50 mL round-
bottomed flask by ultrasound. Then, NH ·H O was
3
2
dropwise added to the mixture, and it was
dramatically stirred at 30 °C for 0.5 h.
Subsequently, formalin (10 mL) was drop by drop
added to the mixture, and the colloid was aged at
°
3
0 C for 4 h. Sequentially, melamine and K CO
2
3
were added into the flask. After stirring for a
further 0.5 h, a homogeneous precursor solution
was obtained. The obtained solution was collected
into a 50 mL stainless steel teflon autoclave and
kept in an electric oven at 110 °C for 24 h. After
cooling down naturally, the yellow precipitates
were collected by filtration and followed by drying
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in a vacuum oven at 60 °C for 12 h, and it was Ar (8% H ) atmosphere at a heating Vi
r
ewat
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o
O
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nline
2
2
DOI: 10.1039/C9GC00908F
°
–1
named as NC-110. Later, the dried precursor C·min . The carbonized particles were washed
particles carbonized at a series of temperatures i.e. several times using deionized water in the
°
5
00, 600, 700, 800, 900 C for 120 min each, under
Scheme 1 The schematic caption of the synthesis of catalyst.
°
oven at 60 C overnight for reserved. Then, it was
ultrasonic irradiation to promote the dissolve of K
ions. Finally, the nanosheets particles were dried in
°
carbonized at 800 C for 120 min under N mixed
2
°
–
with NH atmosphere at a heating rate of 2 C·min
3
°
a vacuum oven at 60 C overnight. The materials
1.
It was called GP-N-800.
were grinded to powder to get NC, named by NC-
2
.4. Synthesis of the catalyst of g-C N
3 4
5
00, NC-600, NC-700, NC-800 and NC-900,
severally. And all procedures remain unchanged,
except for the amount of HCHO added only 5 mL,
the catalysts were called NC-5-800 and NC-5-900.
The schematic caption of the synthesis of catalyst
was shown in Scheme 1.
°
Melamine (1.2 g) was carbonized at 550 C for 180
min under Ar atmosphere at a heating rate of 5
°
–1
C·min . It was named for g-C N .
3
4
2
.5. Catalytic conversion of imines
2
.3. Synthesis of the catalyst of N-doped
The reaction was tested in a 5 mL reaction tube
with an air intake needle, oil bath, and
thermocouple at atmospheric pressure. Typically,
the NC-800 catalyst (15 mg), benzylamine (1
mmol), 1 mL dimethylsulfoxide (DMSO) and 0.5
graphite powder (GP-N)
Graphite powder (GP, 1.2 g) was washed several
times by deionized water and dried in a vacuum
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mL deionized water (D: W=1:0.5) were mixed UV-Vis absorption spectra, and thermog
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DOI: 10.1039/C9GC00908F
°
together and then magnetic stirring at 60 C. The analysis (TGA). The detail description of catalyst
reaction time was 40 h and air was constantly taken characterization instrument was in supporting
-1
into the tube by the air pump (10 mL·min ). The information.
samples were extracted with deionized water and
3
3
. Result and discussion
.1. Characterizations catalyst
ethyl acetate after separation catalyst by
centrifugation. The sample was analyzed by GC-
MS (Agilent 6,890N/5,937N). Furthermore, the
catalyst after reaction can be recycled and then it
was washed with ethanol and deionized water
To investigate the morphology and microstructures
of a series of NC catalysts, the images were carried
out by SEM and TEM. The SEM images of NC-
°
several times, followed by a heat treatment (60 C)
1
9
10, NC-500, NC-600, NC-700, NC-800 and NC-
00 were presented in Fig. 1 and Fig. S1. Fig. 1a
before the next utilization.
2
.6. Catalytic transfer hydrogenation of nitriles
indicated that the nanospheres could be uniformly
°
formed at 110 C. In Fig. S1, as the thermal
Benzonitrile (1 mmol), NC-800 (20 mg) and
additives were added into the 4 mL closed the high
pressure reaction tube containing 1.5 mL mixed
solvent (D: W=1:0.5) and then the reaction system
decomposition
temperature
increased,
the
nanospheres were damaged and transformed into
mesoporous nanosheets. And as shown in Fig. 1, it
can be easily seen that more well-aligned in size
distribution of mesoporous nanosheets were
°
stirred at 60 C. After separated the catalyst and
organic phase, the reaction resulting was analyzed
by GC-MS.
°
carbonized at 800 C.
Meanwhile, two-dimensional mesoporous structure
of NC-800 catalyst was proved by TEM image.
From the TEM image of NC-800 in Fig. 2a, it can
be seen that a mesoporous structure was
successfully formed in the catalyst. The HRTEM
image of NC-800 was shown in Fig. 2b. Besides,
the HRTEM selected-area diffraction image (Fig.
S2a) of NC-800 further revealed an amorphous
carbon
2
.7. Catalyst Characterization
In this study, these catalysts were in detail
characterization to know its properties of physical
and chemical, such as X-ray diffraction (XRD), the
scanning electron microscopy (SEM) and
transmission electron microscopy (TEM), nitrogen
physisorption isotherms, X-ray photoelectron
spectroscopy (XPS), fourier transform infrared
spectroscopy (FT-IR), elemental analysis (EA),
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intensity of NC became more and more stronger.
At the same time,
Fig. 1 SEM images of NC-110 (a), NC-500 (b), NC-600
Fig. 2 TEM images of NC-800 (a), the HRTEM image
showed amorphous carbon structure (b), and HAADF
image (c) of C and N elements mapping images.
(c), NC-700 (d), NC-800 (e) and NC-900 (f).
structure. In Fig. 2c, the high-angel annular dark
field (HAADF) image of C and N element the XRD pattern of GP-CN-800 was exhibited in
mappings demonstrated nitrogen was evenly doped Fig. S3. Fig. 3b presented the Raman spectrum of
in the carbon layer. In addition, the EDX of NC- NC, two distinct peaks around at 1380 and 1598
-1
8
00 was exhibited in Fig. S2.
cm indexed to D- and the G-bands, respectively.
And the intensities of the D and the G bands
demonstrated that a significant number of lattice
defects existed in carbon framework due to N-
doped. Moreover, with the temperature increased
The XRD pattern showed that NC was undefined
°
structure, there were broad peak at around 25 (Fig.
3
a), which corresponded to the (002) plane.
Besides, for NC-700, NC-800 and NC-900, the
°
°
from 500 C to 800 C, the values of I /I increased
D
G
°
other broad peak appeared at around 45 , which
from 0.958 to 1.015. In particular, when the
indexed to the (100) plane. Meanwhile, with the
carbonization temperature increases, the peaks
°
temperature increased at 900 C, the values dropped
to 0.975. It could be concluded that the highest
I /I value was attributed to NC-800, displaying its
D
G
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structure owned the maximum concentration of
defects.
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DOI: 10.1039/C9GC00908F
Fig. 3 XRD patterns (a) and Raman spectra (b) of the as-prepared NC catalysts.
The results of nitrogen adsorption-desorption catalyst showed type IV isotherms with a medium-
isotherms for NC-500 to NC-900 were also shown pressure (P/P =0.47) and the high-pressure
0
in Table 1. Typically, the surface area of the (P/P =1.0) region hysteresis loops, indicating that
0
catalyst obtained at higher carbonized temperature the catalyst mainly contains mesoporous structures
was larger than that at low temperature. In Table 1, with an average pore size of 0.28 nm in Fig. S4a.48-
5
1
it could be easily observed that the surface area of
However, for NC-900 catalyst, it mainly
NC-800 catalyst is 594 m g , which slightly lower contained microporous structures with its nitrogen
2
-1
2
-1
than NC-900 catalyst (638 m g ) but farther adsorption-desorption isotherms showed type I
higher than other catalyst. What’s more, NC-800 isotherms
in
Fig.
S4b.
Table 1 Texture parameters of the series of prepared catalysts.
Surface area
Average pore
Pore volume
Samples
2
-1
3
- 1
(
m g )
size (nm)
(cm g )
NC-500
NC-600
NC-700
NC-800
NC-900
6
57.8
56.8
11.0
3.3
0.01
0.02
0.04
0.28
0.34
40
91
594
638
3.2
FT-IR spectrogram was executed to farther from NC-110 to NC-900. In Fig. 4a, the peaks at
-1
elucidate the existed functional groups in catalysts 1200-500 cm were assigned to C-C, C-N, C-O.
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−
1
12, 25, 62
Especially, vibrational mode of 810-800 cm was catalyst.
Furthermore, compare
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DOI: 10.1039/C9GC00908F
shown C-N heterocycles of triazine ring units.52-54 aminophenol and melamine in Fig. S5, the FT-IR
The characteristic bands of 1700-1200 cm-1 are spectrum of prepared catalysts indicated that these
assigned to aromatic carbon and nitrogen functional groups indeed existed. In addition, on
heterocycles.55, 56 Especially, the peaks at 1650- account of the pyrolytic temperature increased, the
-1
2
−1
1
550 cm for the sp -hybridized C=C and C=N characteristic bands of 850-750 cm
was
stretching region. 57-59 The primary bands in 3300- disappeared. It may be due to the nanospheres
-1
60,
3
500 cm referred to the N-H stretching region.
consisted of triazine units cracked and derive the
6
1
In addition, the band around 2934 cm-1 was nanosheets. Fig. 4b illustrated the TG analysis
contributed to C-H stretching vibrations, indicating (TGA) of NC-800, it could be obtained in the
both piperazine and triazine units existed in NC heated process with the N2 atmosphere.
Fig. 4 FT-IR spectrogram of the as-prepared catalysts (a), TG+DSC curves measured in N for NC-800 from 25 to 800
2
°
°
-1
C with a heating rate of 2 C min (b).
°
In the first stage of 25 to 150 C, the catalyst concluded that the material completed the
showed the thermostability, and the 7.6% mass loss conversions of nanospheres to two-dimension
was due to the desorption of water in the polymer. nanosheets. In third stage, the weight loss achieved
°
There was a large weight fraction decreased about to 33.2% when it was heated to 800 C. In
°
4
0.5% in the region of 150 - 350 C, which was combination with the SEM image, the mass loss is
ascribed to the pyrolysis of NC, and it could be mainly caused by the thermal decomposition of
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57,
le Online
DOI: 10.1039/C9GC00908F
K CO to form mesoporous, and further thermal C-N (285.1 ± 0.2 eV) and C=N (286.1 ±
V
0
iew.2Art
e
ic
V
)
.
2
3
decomposition of the nanosheets with some carbon
and nitrogen functional groups lose in its structure.
In addition, Fig. 4b also displayed the DSC curve
6
5-68
The existence of C-N and C=N in the C 1s
spectra was a strong evidence that N atoms
for the thermal decomposition of the NC-800 successfully doped in the lattice of carbon. In Fig.
°
catalyst from room temperature to 800 C. The
5
a, besides NC-110, NC-800 and NC-900, the N 1s
curve exhibited a rapid decomposition of the NC-
spectrum could be designated into three peaks,
°
8
00 with obvious endothermic peak at 217.7 C and
°
the exothermic peak at 43.7 C. They were in good which were pyridinic-N (398.0 ± 0.2 eV), pyrrolic
agreement with the data of NC material reported in
or pyridonic-N (399.00 ± 0.2 eV) and graphitic-N
the literature.63, 64
6
9
(
400.3 ± 0.2 eV). Especially, the N 1s spectrum
XPS was conducted to discuss the chemical
elements binding states of C and N on the surface
of NC and to investigate the probable reason of
defect formation. The full-scan XPS spectrum of
each NC catalyst contained C, N, and O elements
was also exhibited in Fig. 5b and the contents of
the elements was also listed in Table 2. The high-
resolution spectrum of the C 1s in Fig. S6a could
be divided into three peaks C-C (284.4 ± 0.2 eV),
of NC-110 catalyst only contained pyridinic-N and
pyrrolic or pyridonic-N, and the N 1s spectrum of
NC-800 catalyst only contained pyridinic-N and
graphitic-N.67, 68 As was said above, with the
°
°
temperature increased from 500 C to 800 C (Table
and Fig. 5c), the tendency of contained graphitic-
2
N was increased in matrix carbon, but pyridinic-N
and
Table 2 The XPS analysis and element contents chemical analysis in the prepared catalysts.
XPS analysis
EA
Graphitic-N (at. N (wt.
Sample
Pyridinic-N
Pyrrolic or pyrid-
-onic-N (at. %)
13.41
N (at. %)
(
at. %)
6.50
5.54
0.85
%)
0
%)
NC-110
19.91
21.73
17.08
10.55
1
0.44
.31
3.05
1.85
1.35
NC-500
NC-600
4
2.11
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4
2
.11
.51
0.58
0.47
0.61
-
0.89
2.64
2.04
0.34
-
8.31
NC-700
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DOI: 10.1039/C9GC00908F
0
5.71
NC-800
NC-900
1.44
0.49
0.86
6.57
1.85
-
-
-
-
NC-5-800
NC-5-900
-
-
pyrrolic or pyridonic-N decreased. It was hydrogen atmosphere under the high temperature
accounted that graphitic-N could give rise to carbonization conditions. Meanwhile, all of the NC
inhomogenous distribution of electrons in the π- catalysts tested by XPS wide-scan spectra exhibited
system, enhanced the electron transfer throughout the N contents had a declining trend when the
carbon plane, thus improved the activity and calcination temperature increased. Similarly, the N
stability of catalyst.49 However, when pyrolytic contents of prepared NC catalysts detected by
°
temperature reached to 900 C, the contained element contents chemical analysis showed the
graphitic-N in NC-900 catalyst was sharply same trend. As for NC-5-800 and NC-5-900, the N
dropped to 0.36 at. %, the contained pyrrolic or contents were higher than the NC-800 and NC-900,
pyridonic-N increased. One reason was that the respectively, which were determined by EA.
graphitic-N may be pyrolyzed at the high Furthermore, the wide-scan XPS spectrum of GP-
temperature, the other was that the pyridonic-N N-800 presented in Fig. S6b.
transformed into pyrrolic or pyridonic-N due to the
Fig. 5 High-resolution N 1s spectra (a), XPS wide-scan spectra (b), and the percentages of pyridinic-N, pyrrolic or
pyridonic-N and graphitic-N of the NC catalysts (c).
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DOI: 10.1039/C9GC00908F
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ARTICLE
obtain an effective conversion rate in a short time
for substrate expansion and kinetic study. And
there is no doubt that the reaction could also indeed
occur at low temperatures though it needed long
3
.2. Catalyst performance
In order to present the catalytic activity and
application, Table 3 showed comparison of the
different catalysts. Obviously, the NC-800 was
quite different with other catalysts in the self-
oxidation of primary amines reaction under
environmentally friendly condition. It could be
easily seen from Table 3 when the temperature
°
reaction time, such as at 50 and 70 C. The entries 4
and 13-16 explained that the effect of catalyst
amount to the reaction, which were demonstrated
the optimal amount was 15 mg and the minimum
catalyst amount was 5 mg. Because the turnover
frequency (TOF) values of entry 4 surpassed the
any other reaction conditions. But for entry 13,
when the catalyst amount was 5 mg, it was shown
the conversion of the reaction was only 13%.
Selecting entries 17, 18, 20 and 23 for comparison,
it was found that only graphene with a large BET
surface area could catalyze the reaction, but the
conversion was very low. Based on the results
discussed above, it suggested that carbon atoms
were not mainly active sites, and the catalyst
should need a large BET surface area that the
substrate would be absorbed on it. Notably,
compared entry 18 with 19, it was undisputed that
the conversion rate of the reaction increased due to
the N-doped, which may illustrate nitrogen atoms
were mainly active sites for this reaction. In short,
with Table 3, it can be concluded that the yields of
the reaction had greatly changed with the increased
of graphite-N content. It was the strong evidence
that nitrogen atoms, especially graphite-N, were
°
were at 60 and 120 C (entries 1 and 4), the yields
could reach to 99.9 % after reaction 40 and 8 h,
respectively. For entries 1 and 4, when the reaction
temperature at 60 °C, it is inconvenient to
investigate the kinetic study of this reaction that the
reaction took a long time to fully convert amine to
imine. Therefore, by increasing the reaction
temperature to calculate the activation energy of
the reaction is needed. Meanwhile, compared
entries 1-7 with entries 8-12 and 17-23, it could be
explicitly observed that the NC-800 was superior to
other catalysts, which was unquestionable in yield
at the same reaction condition. According to the
yields of entries 1-7, with the temperature increased
°
from 50 to 130 C, the NC-800 could effectually
enhance the conversion rate of the reaction.
Therefore, although the reaction temperature at 60
°
C was considered to be a mild condition, it is a
good choice to control the reaction conditions at
20 °C, which was advantageous for the reaction to
1
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mainly active sites. In addition, it was unexpected reaction time prolonged, the sub-p
V
r
i
o
ew
d
A
u
rti
c
cl
t
e Online
o
f
DOI: 10.1039/C9GC00908F
that the NC-800 catalyst could be applied in oxidative coupling of benzylamine gradually
transfer hydrogenation reaction of benzonitrile. For changed from benzonitrile to benzaldehyde.
entries 8-11, it was initially discovered that as the
Table 3 The catalytic activities of the different catalysts.a
°
-1 -1 b
Entry
Catalyst/ (mg)
NC-800/ 15
NC-800/ 15
NC-800/ 15
NC-800/ 15
NC-800/ 15
NC-800/ 15
NC-800/ 15
NC-900/ 15
NC-700/ 15
NC-600/ 15
NC-500/ 15
NC-110/ 15
NC-800/ 5
Temp. ( C)
Time (h)
Conv./ Sel. (%)
99.9/99.9
73/99.9
99.9/99.9
99.9/99.9
99.9/65
89/99.9
82/99.9
40/79
TOF (mol·g h )
1
2
3
4
5
6
7
8
9
60
40
40
40
8
1.67×10-3
1.22×10-3
1.67×10-3
8.34×10-3
1.67×10-3
7.42×10-3
6.83×10-3
3.34×10-3
7.50×10-3
6.92×10-3
4.00×10-3
-
50
70
120
130
110
100
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
8
8
8
8
8
90/85
1
1
1
1
1
1
1
1
1
1
2
2
2
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
8
83/78
8
48/80
10
8
-
13/99.9
63/99.9
99.9/99.9
99.9/99.9
20/99.9
-
3.25×10-3
7.89×10-3
7.07×10-3
6.09×10-3
6.25×10-3
-
NC-800/ 10
NC-800/ 20
NC-800/ 25
Graphene/ 4
GP-800/ 15
GP-N-800/ 15
8
7
6.5
8
8
8
17/99.9
25/85
1.42×10-3
2.08×10-3
8.34×10-3
3.92×10-3
-
g-C
3
N
4
/ 15
8
NC-5-800/ 15
NC-5-900/ 15
CNTs/ 15
8
99.9/97
47/80
8
8
-
1
2 | J. Name., 2012, 00, 1-3
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2
4
none
120
8
-
-View Article Online
DOI: 10.1039/C9GC00908F
a
Reaction conditions: 1 mmol benzylamine, 15 mg catalyst, 1.5 mL solvent (D:W=1:0.5) and air was brought in reaction system by pump
b
with 10 mL/min. The conversion and selectivity were detected by GC-MS. Turnover frequency (TOF) = mol of benzylamine converted per
gram of catalyst per hour.
As is well known, the solvent with higher polarity which metal ions (such as KCl and NaCl) that may
is more beneficial to the conversion of remain in the nitrogen-doped carbon catalyst were
benzylamine. Therefore, it was found that D:W= added under the same reaction conditions. It is easy
1
:0.5 was the best one among the solvents tested to find that the conversion of the product is trace.
(Table 4, entries 7, 15) as compare to common Then, we simultaneously added NC-800 catalyst
solvents, such as N, N-dimethyl-formamide and KCl (or NaCl) and tested under the same
DMF), CH CN, toluene, DMSO and so on.70 reaction conditions. The results showed a slight
(
3
Especially, for entry 10, though the TOF value of decrease in the selectivity of the product.
the reaction surpassed any other reaction Therefore, we can draw a rough conclusion that the
conditions, its yield of the reaction was not higher mainly catalytic activity is due to the doping of
than entries 7 and 15. However, the catalytic nitrogen on carbon, and the more impurity metal
activity of the catalysts is due to doped carbon ions contained in the target catalyst, the weaker the
itself and not due to potential contamination with catalytic activity. Detailed data of the comparative
traces of metal ions is not absolutely clear. In view experiment was shown in supporting information
of this, we designed a comparative experiment in (Table
S1).
Table 4 The catalytic activities of NC-800 in the different solvents.a
Temp.
(°
C)
60
60
Time
(h)
Solvent/
1.5 mL
Conv. Yield
TOF
Entry
-1
-1
(%)
80
(%)
80
(mol·g h )
1.34×10-3
1.44×10-3
1
2
40
CH CN
3
40
Toluene
86
86
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3
4
5
6
7
8
9
60
60
40
40
40
40
40
8
Water
-
-
20
94
72
99.9
70
63
80
68
75
82
94
99.9
60
52
5
-
View Article Online
DOI: 10.1039/C9GC00908F
Ethanol
DMSO
20
94
0.34×10-3
60
1.57×10-3
1.20×10-3
1.65×10-3
8.34×10-3
8.00×10-3
13.86×10-3
8.34×10-3
8.34×10-3
8.34×10-3
8.34×10-3
8.34×10-3
5.00×10-3
4.34×10-3
0.42×10-3
60
1, 4-dioxane
D:W =1:0.5
DMSO
72
60
99.9
99.9
96
120
120
120
120
120
120
120
120
120
120
120
8
DMF
1
0b
24
8
Solvent-free
D:W =1.4:0.1
D:W =1.3:0.2
D:W =1.2:0.3
D:W =1.1:0.4
D:W =1:0.5
D:W=0.9:0.6
Water
99.9
99.9
99.9
99.9
99.9
99.9
60
1
1
2
3
4
5
6
1
1
1
1
1
8
8
8
8
8
1
7c
8d
8
52
1
8
Water
5
a
Reaction conditions: 1 mmol benzylamine, 15 mg NC-800 catalyst and air was brought in reaction system by pump with 10 mL/min. The
b
c
conversion and selectivity were detected by GC-MS. 5 mmol benzylamine. 1 mmol benzylamine, 15 mg NC-800 catalyst and the filled
d
with O
2
reacted at the closed the high pressure reaction tube. 1 mmol benzylamine, 15 mg NC-800 catalyst and the filled with N
2
reacted in
the closed the high pressure reaction tube.
Moreover, to explore the wide applicability of the coupling reaction of benzylamine derivatives
NC-800 catalyst, other types of amines, cyanides having an electron withdrawing group. As for
and nitriles were all used for the substrate extension entries 17-24 in Table 5, when two amines with a
reaction under the optimal reaction condition, molar ratio of 1:1 were added to the reaction
severally. Each type substrate was converted to system, the highest yields could reach 64 %. In
relevant product with high yield shown in Table 5 addition, for the reaction of the oxidation of
and Table 6. In Table 5, the reactions of converted amines, when we performed NC-600, NC-700 or
imines by various amines had high yields. NC-900 to react, it was found that the presence of
Meanwhile, for entries 1-16, it could be induced benzaldehyde and benzonitrile was present in the
that as the ability of the electron donating group detection of the product. And the concentration of
was weakened, the yield of the imine was improved benzaldehyde present in the sub-product is higher
under the optimum reaction conditions. That is to than that of benzonitrile with the reaction time
say, NC-800 is more suitable for the oxidative increasing. Therefore, in Table 6, the high yields
1
4 | J. Name., 2012, 00, 1-3
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for catalytic transfer hydrogenation of nitriles were almost 30% without the addition of NCVie
-
w
8
A
0
rti
0
cle O
a
n
n
line
d
DOI: 10.1039/C9GC00908F
also confirmed the outstanding catalytic only adding KOH. When NC-800 and KOH are
performance of NC-800 at the low temperature. added at the same time in the reaction, the yield of
Adding different additives, the final products of the product reaches the maximum under the same
these reactions were totally different, we could reaction conditions. In view of this, we believe that
obtain aldehydes, amides, and amines by adding the hydrolysis reaction occurs due to the
K CO , KOH, and NaBH , respectively. Finally, in simultaneous presence of KOH and NC-800 in the
2
3
4
Table S2, when only adding additives, the reaction, which play a synergistic role. And for the
comparative experiments also exhibited that the reduction of nitrile to amine, the reducing agent is
effect of the transfer hydrogenation of nitriles NaBH . Its mechanism of action is the nucleophilic
4
reaction system was extremely declined without addition of H to the positive charge center by the
NC-800 catalyst. By consulting a large amount of dissociation of NaBH . And NC-800 catalyst
4
literature, for the reaction of nitrile to aldehyde, the makes the process of nucleophilic addition easier.
reducing agent is H O. In addition, we add K CO All in all, for the transfer hydrogenation of nitriles
2
2
3
into the reaction of nitrile to aldehyde to provide a reaction, the reaction scope was most aromatic
weak alkaline environment and the mechanism of nitriles and some fatty cyanides. Meanwhile, from
the reaction were also shown in Scheme 2. Table S3, it was found that the catalytic
Furthermore, as is well known, the transformation performance of the metal-free nitrogen-doped
of nitrile to carboxamide is hydrolysis reaction. carbon catalyst can be comparable to that of the
From the comparative experiment in Table S2, the metal-supported catalysts through experimental
results demonstrated that the reaction yield is tests.
Table 5 The imines reaction of various amines by NC-800.
a
c
a
a
(
1) Y : 99.9 % (8 h)
(2) Y: 99.9 % (8 h)
(3) Y: 80.5 % (8 h)
a
a
a
(
4) Y: 96.0 % (9 h)
(5) Y: 97.0 % (9 h)
(6) Y: 80.9 % (9 h)
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DOI: 10.1039/C9GC00908F
a
a
a
(
7) Y: 91.0 % (10 h)
(8) Y: 99.9 % (10 h)
(
9) Y: 99.9 % (8 h)
a
a
a
(12) Y: 92.0 % (8 h)
(
10) Y: 93.0 % (8 h)
(11) Y: 65 % (10 h)
a
a
(
13) Y: 81.0 % (8 h)
(14) Y: 29.0 % (10 h)
a
(
15) Y: 45.5 % (8 h)
b
a
a
(
16) Y: 56.0 % (12 h)
(17) Y: 99.9% (10 h)
(18) Y: 49.0 % (10 h)
b,
a
b
(
19) Y: 56.8% (12 h)
(20) Y: 64.0 % (10 h)
(
21) Y: 30.0 % (12 h)
a
a
a
(
22) Y: 45.0 % (10 h)
(23) Y: 20.0 % (10 h)
(24) Y: 27.0 % (10 h)
a
Reaction conditions: 1 mmol amines, 15 mg NC-800 catalyst 1.5 mL solvent (D:W=1:0.5) and air was brought in reaction system by pump
b
with 10 mL/min. The conversion and selectivity were detected by GC-MS. 1 mmol amines, 15 mg NC-800 catalyst, 1.5 mL solvent
(
D:W=1:0.5) and the filled with O
2
reacted in the closed the high pressure reaction tube. c Y= yield (%).
Table 6 The transfer hydrogenation of nitriles.
1
2
3
1
6 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C9GC00908F
a
b
c
1
.(1) Y: 99.9 % (8 h)
2.(1) Y: 99.9 % (8 h)
3.(1) Y: 99.9 % (6 h)
a
b
1
.(2) Y: 60.0 % (10 h)
2.(2) Y: 87.0 % (8 h)
c
3
3
.(2) Y: 99.9 % (6 h)
c
.(3) Y: 99.9 % (6 h)
a
1
.(3) Y: 99.9 % (8 h)
b
2
2
2
2
.(3) Y: 99.9 % (8 h)
a
c
1
.(4) Y: 99.9 % (8 h)
b
3.(4) Y: 99.9 % (6 h)
.(4) Y: 99.9 % (8 h)
c
a
3.(5) Y: 99.9 % (6 h)
1
.(5) Y: 99.9 % (8 h)
b
.(5) Y: 99.9 % (8 h)
a
c
1
1
1
.(6) Y: 99.9 % (6 h)
b
3.(6) Y: 99.9 % (6 h)
.(6) Y: 99.9 % (8 h)
c
b
3
.(7) Y: 99.9 % (4.5 h)
a
.(7) Y: 99.9 % (8 h)
2.(7) Y: 99.9 % (8 h)
c
a
b
3.(8) Y: 99.9 % (4.5 h)
.(8) Y: 99.9 % (8 h)
2.(8) Y: 99.9 % (8 h)
a, b, c
Reaction conditions: 1 mmol nitriles, 20 mg NC-800 catalyst and 1.5 mL solvent (D:W=1:0.5) reacted in the closed the high pressure
reaction tube at 60℃. The conversion and selectivity were detected by GC-MS.
a
b
c
2 3 4
Extra adding 2 mmol K CO , extra adding 2 mmol KOH, and extra adding 5 mmol NaBH .
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was the activation energy, R was ideal gas constant
3
.3. Kinetic study
−
1
−1
(
8.314 J·mol ·K ) and the T was the reaction
To realize the mechanism and the order of the
reaction of the imines reaction, the kinetic study of
the reaction was explored. The overall kinetics
equation of the reaction could be defined as:
temperature. In Fig. 6, in order to compute the n
and E of the reaction, the specific concentration of
a
°
benzylamine was calculated from 90 to 120 C for
different reaction time with the Eq. (2-5). It could
K
[
Amine] + [O2]
[ Imine] + NH3 + H2O (1)
be obviously calculated the total order was n =
0
.314, and E was 67.39 kJ/mol. The apparent
a
The formulation of the reaction rate was given by
activation value is 67.39 kJ/mol (Fig. 6c), which is
very similar to the reported value of 62.8 kJ/mol.71
And the reported responses are assumed to be
pseudo first-order reaction, but after we
investigated, it was found that the order of the
reaction is 0.314 in the work. Simultaneously, UV-
Vis was also performed to analysis the reaction rate
of the reaction in Fig. S7.
Eq. (2). Where the [C ] represented the
A
benzylamine, k represented the rate constant and
the n , n and n were the series of the [Cat.], [O ]
1
2
2
and [C ], severally. Where the [C ], [O ] and
A
A
2
[Cat.] were the concentration of substrate, oxygen
and catalyst. Meanwhile, as previous assumed [O2]
as a constant and combined the reported
mechanism, the kinetic rate equation was derived
1
2
n
n
1
n2
with the constant K defined as: K = k [Cat.] [O ] .
n
n
2
r = k[Cat.] O2 CA
[ ] [ ]
(2)
(3)
Therefore, the Eq. (2) could be predigested to Eq.
[
CA]n
r = K
(3), and the equation of the reaction rate was given
E
a
by Eq. (4-5). The K was the apparent rate constant
of reaction, A was the pre-exponential factor, Ea
-
RT
K = Ae
(4)
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퐸푎
binding energy between the bonds on th
V
e
iew
m
Art
a
icl
t
e
e
O
rial
n
li
ne
푙푛퐾 = 푙푛퐴 ― 푅푇
(5)
DOI: 10.1039/C9GC00908F
is slightly reduced. However, from the N 1s
spectrum, the active sites was not destroyed and
remained graphite-N.
3
.4 Catalyst recycled
Furthermore, the number of cycles of the catalyst
was an important indicator of whether it could be
industrialized. In view of this, the NC-800 catalyst
could be easily separated from reaction system by
centrifugation and then washed with ethanol and
deionized water for three times, respectively. Then,
3
.5 Mechanism study
Distinctly, in order to investigate the mechanism of
resultant imines reaction, the defect of two-
dimensional NC nanosheets should be firstly
studied. In Fig. 3b, as the calcination temperature
increased, the values of I /I became larger, and it
°
the catalyst was dried in a vacuum oven at 60 C
D
G
for 12 h to farther assess the repeatability of the
catalyst for the oxidation amines reaction. In Fig. 7,
it was found that the yield of imine exceeded
can be deduced that the defect carbon concentration
in NC-500, NC-600, NC-700 and NC-800
increased in turn, which proved the high
concentration of defective carbon could be ascribed
to N-doped in the lattice of carbon. However, for
NC-900, combined the EA (the content of N)
values with the decreased value of ID/IG also
demonstrated the formation of defect carbon due to
the N doping. In addition, based on the analysis of
XPS spectra of N 1s (Table 2 and Fig. 5), the N
contents of NC catalysts also displayed the
decreased tendency as the carbonized temperature
9
9.9% after seven cycles experiment, indicating
that the reusability and activity of the catalyst were
very brilliant. The FT-IR and XPS of reused
catalyst were shown in Fig. S8 and S10. The FT-IR
spectrum demonstrated that the spectrum of reused
catalyst was the same as the fresh, it proved that the
catalyst was not damaged after cyclic test. And in
Fig. S10, we can easily obtain that the binding
energy of C 1s and N 1s have slight deviation in
XPS spectrum. The possible factors are: the error
of the experimental instrument or the electron
transfer between the nitrogen-doped carbon
material and the reaction substrate, so that the
°
°
increased from 500 C to 900 C, the EA showed
the same trend as well. Moreover, the high-
resolution
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Fig. 6 The kinetic curve of the catalytic oxidation benzylamine (inset: the total order of the reaction) (a), the different
View Article Online
DOI: 10.1039/C9GC00908F
reaction time at the different reaction temperature (b), and the reaction of activation energy (c).
compared NC-800 adsorbed benzylamine with NC-
00, the binding energy had a significant shift
8
toward the low binding energy, which was
attributed to the interaction of lone pair electrons of
N atom in NC-800 and the π electrons of
benzylamine. It could be deduced that the transfer
of electrons from benzylamine to NC-800 increased
the charge density of NC-800, which leaded the
reaction rapidly proceeding. In addition, the
Fig. 7 The recyclability of the catalyst. (Reaction conditions: 15 mg
NC-800 catalyst, 1 mmol benzylamine, 1.5 mL solvent (D: W=1:0.5)
and air was brought in reaction system by pump with 10 mL/min at
°
1
20 C for 8 h. The conversion and selectivity were detected by GC- experimental
MS.)
N 1s spectra could exhibited the content of
graphitic-N in the NC material, which presented an
increased trend in Fig. 5c. It might be given a clue
that graphitic-N was the main cause of defects
formation and the graphitic-N was the mainly
active sites. Furthermore, in Fig. S8, FT-IR spectra
proved that benzylamine was firstly absorbed in the
catalyst, then to occur oxidation reaction. And it
-1
could be easily observed that at around 1425 cm a
new peak occurred. Meanwhile, the catalyst for the
adsorption of benzylamine were also performed
XPS full-scan spectra (Fig. S9) and the high-
resolution spectrum of C 1s and N 1s (Fig. 8)
analysis. Compared with the high resolution
spectrum of N 1 s (Fig. 8b) of NC-800, it could be
found that two new peaks occurred due to the
adsorption of the substrate, one was attributed to
the bond -NH of benzylamine and the other was
2
assigned to the new bond of graphitic-N and -NH2
7
2
group. From Fig. 8, it could conclude that when
2
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DOI: 10.1039/C9GC00908F
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Fig. 8 Comparison of high resolution C 1s spectra (a), and N 1s spectra (b) between NC-800 and NC-800 adsorbed
benzylamin.
results of this work (Table 3) also demonstrated the existence through the analysis method such as GC-
graphitic-N was the mainly active sites, and the MS. For example, Jones et al. proposed the same
high yields of imines could obtain when the mechanism but the intermediate still did not have
7
5
graphitic-N existed. And when the reaction was not experimental proof to demonstrate. Zhang et al.
occurred at the optimal condition, a certain amount attempted to detect the intermediate by in situ
of benzaldehyde and benznitrile was detected in the NMR technique, but they also did not directly
7
1
product by GC-MS. It maybe present the path of detect it at the end. However, they thought that
oxidative dehydrogenation of primary amines.And dibenzylamine and N-methyl-1-
it was also proved that the oxygen played a vitally phenylmethanamine majorly generated the
crucial role in the reaction (entries 17 and 18). corresponding benzaldimines as detected by GC
Meanwhile, butylated hydroxytoluene (BHT) was was indirectly proved the benzaldimine was
added to the reaction system to quench the intermediate in the reaction.71
synthesis of imines.37, 73 The result was that large
Hence, based upon the above study and the
quantities benzaldehyde and imine were produced
previous reported literature (Table S3), the
in the reaction. Moreover, other related carbon
mechanism of the reaction should be legitimately
catalysts for this reaction play a key role in
proposed in Scheme 2. Generally, the primary
understanding this working mechanism. Previous
amines reacted into imines involved two different
research conjectured benzaldimine as an
oxidative dehydrogenation routes (Scheme 2, paths
intermediate in the reaction of benzylamine to
1
and 2).16, 35-38, 76, 77 Therefore, the reaction
7
4
benzylimine. However, it is difficult to prove the
mechanism of the catalytic system was also no
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J. Name., 2013, 00, 1-3 | 21
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ARTICLE
Journal Name
exception. Nevertheless, the formation of economically feasible reaction conditionVie
s
w A
s
r
u
tic
c
le
h
Online
a
s
DOI: 10.1039/C9GC00908F
°
RCH=NH as an intermediate from primary amines air atmosphere, low temperature (60 C) and low
by NC-800 was common in the both steps. Firstly, catalyst
amine and O were activated by the catalyst to form
2
active species, respectively, under the optimized
reaction conditions. Then, in path 1, the formed
imine intermediate was hydrolyzed imine to obtain
aldehyde. After that, the aldehyde reacted with
another amine molecule to form the targeted
product. However, for path 2, the formed RCH=NH
intermediate directly reacted with another amine
molecule to obtain an aminal. Finally, the aminal
missed a molecule of NH to form the targeted
3
compound. Meanwhile, as is well known, when the
catalyst is added to the reaction, the reaction
Scheme 2 Proposed mechanism of the reaction.
pathway will change. And when investigating the
amount (15 mg), the NC-800 owned reputably
effect of the presence of the catalyst on the
catalytic performance, and a wide substrate scope
reaction, it was found that the reaction did not
for amines and nitriles transformed to the
occur without the addition of the catalyst.
corresponding products. And the results showed
Therefore, through the kinetic study of the reaction,
that most of the yields of these four reactions were
we calculated the apparent activation value is 67.39
all over 90 %. According to excellently
kJ/mol, which is very similar to the reported value
7
1
experimental results and the characterizations of
the catalyst, we can conclude the nitrogen-doped
carbon was formed defects in the catalysts are very
important to the catalytic activity. In particular,
graphite-N is considered to be the main active site
in the catalyst. Moreover, the reaction of amine to
imine on NC-800 does not follow the reported
pseudo-first-order kinetics, which order is 0.314
and the apparent activation value is 67.39 kJ/mol.
Particularly, the NC-800 had highly-stable catalytic
performance and could be reused at least 7 times,
of 62.8 kJ/mol. Combined the reported literature
with the above experimental results, the self-
oxidative coupling of amines was mainly carried
out through the path 1 in this work.
4
. Conclusion
In this work, an environmentally friendly and
multifunctional catalyst of two-dimensional
mesoporous N-doped carbon for the oxidative
resultant imines and transfer hydrogenation of
nitriles had been investigated. Under an
2
2 | J. Name., 2012, 00, 1-3
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Journal Name
ARTICLE
Pino-González, E. Rodríguez-Castellón, J. VMiew.ArtLicláezOanrlione-
Martínez, J. J. Guerrero-González, J. DCO.IG: 1.0E.10s3te9v/Ce9sGdCa00S9i0lv8aF
which show greatly potential performance in large-
scale production. In summary, the simple
preparation and outstanding activity of the catalyst
would offer a valid way to the sustainable green
chemistry.
and J. Jiménez-Jiménez, Talanta, 2019, 194, 150-157.
8.Y. Wen, B. Wang, C. Huang, L. Wang and D. Hulicova-
Jurcakova, Chem.-Eur. J., 2015, 21, 80-85.
9.J. R. Maluta, S. A. S. Machado, U. Chaudhary, J. S.
Manzano, L. T. Kubota and I. I. Slowing, Sens. Actuators B
Chem., 2018, 257, 347-353.
1
1
2
2
0.W. Wu, Q. Zhang, X. Wang, C. Han, X. Shao, Y. Wang, J.
Liu, Z. Li, X. Lu and M. Wu, ACS Catal., 2017, 7, 7267-
7
273.
Conflicts of interest
There are no conflicts to declare.
References
1.L. Miao, D. Zhu, M. Liu, H. Duan, Z. Wang, Y. Lv, W.
Xiong, Q. Zhu, L. Li, X. Chai and L. Gan, Chem. Eng. J.,
2
018, 347, 233-242.
2
2
2
2.M. Latorre-Sánchez, A. Primo and H. García, Angew.
Chem. Int. Ed., 2013, 52, 11813-11816.
3.C. Schäfer, C. J. Ellstrom, H. Cho and B. Török, Green
Chem., 2017, 19, 1230-1234.
4.Y. Yang, C.-J. Sun, D. E. Brown, L. Zhang, F. Yang, H.
Zhao, Y. Wang, X. Ma, X. Zhang and Y. Ren, Green
Chem., 2016, 18, 3558-3566.
1
.D. Pech, M. Brunet, H. Durou, P. Huang, V. Mochalin, Y.
Gogotsi, P.-L. Taberna and P. Simon, Nat. Nanotechnol.,
2
010, 5, 651.
25.N. D. Shcherban, P. Mäki-Arvela, A. Aho, S. A.
Sergiienko, P. S. Yaremov, K. Eränen and D. Y. Murzin,
Catal. Sci. Technol., 2018, 8, 2928-2937.
2
3
4
5
6
.C. Peng, X.-b. Yan, R.-t. Wang, J.-w. Lang, Y.-j. Ou and
Q.-j. Xue, Electrochim. Acta, 2013, 87, 401-408.
.J. Ma, Y. Ma and F. Yu, ACS Sustain. Chem. Eng., 2018, 6, 26.X.-k. Kong, Z.-y. Sun, M. Chen, C.-l. Chen and Q.-w.
178-8191.
Chen, Energy Environ. Sci., 2013, 6, 3260-3266.
.S. Zhao, C. Zhao, X. Li, F. Li, L. Jiao, W. Gao and R. Li, 27.M. Li, F. Xu, H. Li and Y. Wang, Catal. Sci. Technol.,
RSC Adv., 2016, 6, 76582-76589.
2016, 6, 3670-3693.
.Z. Daşdelen, Y. Yıldız, S. Eriş and F. Şen, Appl. Catal. B- 28.B. Chen, L. Wang, W. Dai, S. Shang, Y. Lv and S. Gao,
Environ., 2017, 219, 511-516.
ACS Catal., 2015, 5, 2788-2794.
.Q. Wang, H. Liu, R. Li, M. Yang, Z.-B. Wang, L. Zhang, C. 29.S. Furukawa, R. Suzuki and T. Komatsu, ACS Catal.,
8
Li and D.-M. Gu, ACS Appl. Mater. Inter., 2017, 9, 44512-
4518.
.D.-W. Wang, F. Li, Z.-G. Chen, G. Q. Lu and H.-M. Cheng,
Chem. Mater., 2008, 20, 7195-7200.
2016, 6, 5946-5953.
30.V. V. Patil, E. M. Gayakwad and G. S. Shankarling, J.
Org. Chem., 2016, 81, 781-786.
31.D. P. Narayanan, S. K. Cherikallinmel, S. Sankaran and B.
N. Narayanan, J. Colloid Interf. Sci., 2018, 520, 70-80.
4
7
8
.Y. Lin, S. Wu, W. Shi, B. Zhang, J. Wang, Y. A. Kim, M.
Endo and D. S. Su, Chem. Commun., 2015, 51, 13086- 32.B. Majumdar, D. Sarma, S. Jain and T. K. Sarma, ACS
3089.
Omega, 2018, 3, 13711-13719.
.J. Tong, Q. Li, W. Li, W. Wang, W. Ma, B. Su and L. Bo, 33.R. Ramesh, G. Sankar, J. G. Malecki and A. Lalitha, J.
ACS Sustain. Chem. Eng., 2017, 5, 10240-10247.
Iran. Chem. Soc., 2018, 15, 1-9.
0.Y. Song, W. Chen, C. Zhao, S. Li, W. Wei and Y. Sun, 34.A. Fernandes and B. Royo, ChemCatChem, 2017, 9, 3912-
Angew. Chem. Int. Ed., 2017, 56, 10840-10844.
3917.
1.C. Ruiz-García, F. Heras, L. Calvo, N. Alonso-Morales, J. 35.V. S. Marakatti, S. C. Sarma, B. Joseph, D. Banerjee and
1
9
1
1
J. Rodriguez and M. A. Gilarranz, Appl. Catal. B-Environ.,
018, 238, 609-617.
2.Y. Leng, J. Li, C. Zhang, P. Jiang, Y. Li, Y. Jiang and S.
Du, J. Mater. Chem. A, 2017, 5, 17580-17588.
S. C. Peter, ACS Appl. Mater. Inter., 2017, 9, 3602-3615.
36.S. Kostera, B. Wyrzykiewicz, P. Pawluć and B. Marciniec,
Dalton Trans., 2017, 46, 11552-11555.
37.P. Liu, C. Li and E. J. M. Hensen, Chem.-Eur. J., 2012, 18,
12122-12129.
2
1
1
3.Y. Sun, I. Sinev, W. Ju, A. Bergmann, S. Dresp, S. Kühl,
C. Spöri, H. Schmies, H. Wang, D. Bernsmeier, B. Paul, R. 38.P. Sudarsanam, A. Rangaswamy and B. M. Reddy, RSC
Schmack, R. Kraehnert, B. Roldan Cuenya and P. Strasser,
ACS Catal., 2018, 8, 2844-2856.
Adv., 2014, 4, 46378-46382.
39.R. D. Patil and S. Adimurthy, RSC Adv., 2012, 2, 5119-
1
4.J.-Y. Park, D.-H. Kwak, K.-B. Ma, S.-B. Han, G. S. Chai,
5122.
S.-K. Kim, D.-H. Peck, C.-S. Kim, A. Kucernak and K.-W. 40.A. Dhakshinamoorthy, M. Alvaro and H. Garcia,
Park, J. Catal., 2018, 359, 46-54.
ChemCatChem, 2010, 2, 1438-1443.
5.W. Chen, J. Shi, T. Zhu, Q. Wang, J. Qiao and J. Zhang, 41.J. Jin, C. Yang, B. Zhang and K. Deng, J. Catal., 2018,
Electrochim. Acta, 2015, 177, 327-334.
361, 33-39.
6.J. Ye, K. Ni, J. Liu, G. Chen, M. Ikram and Y. Zhu, 42.J. Yang and C.-Y. Mou, Appl. Catal. B-Environ., 2018,
ChemCatChem, 2018, 10, 259-265.
231, 283-291.
7.M. Algarra, D. Bartolić, K. Radotić, D. Mutavdžić, M. S. 43.A. Goto, H. Naka, R. Noyori and S. Saito, Chem.-Asian J.,
1
1
1
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 23
Please do not adjust margins

Please Gd roe en no tC ha ed mj u iss tt r my argins
Page 24 of 24
ARTICLE
Journal Name
2
011, 6, 1740-1743.
69.K. Wang, W. Gao, P. Jiang, K. Lan, M. YangVi,ewXA.rtiHcleuOannligne,
4
4.K. Singh, A. Sarbajna, I. Dutta, P. Pandey and J. K. Bera,
Chem.-Eur. J., 2017, 23, 7761-7771.
5.J. Long, K. Shen and Y. Li, ACS Catal., 2017, 7, 275-284.
L. Ma, F. Niu and R. Li, Mol. Catal.,D2O0I1: 910,.1406359,/C493G-C5030.908F
70.A. Grirrane, A. Corma and H. Garcia, J. Catal., 2009, 264,
138-144.
4
4
6.M. K. Rong, K. van Duin, T. van Dijk, J. J. M. de Pater, 71.Z. Zhang, F. Wang, M. Wang, S. Xu, H. Chen, C. Zhang
B.-J. Deelman, M. Nieger, A. W. Ehlers, J. C. Slootweg and J. Xu, Green Chem., 2014, 16, 2523-2527.
and K. Lammertsma, Organometallics, 2017, 36, 1079- 72.Y. Wang, J. Zhou, X. Hao, Y. Wang and Z. Zou, Appl.
090. Surf. Sci., 2018, 456, 861-870.
7.N. Salam, S. K. Kundu, R. A. Molla, P. Mondal, A. 73.L. Jiang, L. Jin, H. Tian, X. Yuan, X. Yu and Q. Xu,
1
4
Bhaumik and S. M. Islam, RSC Adv., 2014, 4, 47593-
7604.
8.J. Zhang, J. Yang, J. Wang, H. Ding, Q. Liu, U. Schubert,
Y. Rui and J. Xu, Mol. Catal., 2017, 443, 131-138.
9.X. Cui, Y. Long, X. Zhou, G. Yu, J. Yang, M. Yuan, J. Ma
and Z. Dong, Green Chem., 2018, 20, 1121-1130.
Chem. Commun., 2011, 47, 10833-10835.
74.B. Zhu, M. Lazar, B. G. Trewyn and R. J. Angelici, J.
Catal., 2008, 260, 1-6.
75.N. Kang, J. H. Park, K. C. Ko, J. Chun, E. Kim, H.-W.
Shin, S. M. Lee, H. J. Kim, T. K. Ahn, J. Y. Lee and S. U.
Son, Angew. Chem. Int. Ed., 2013, 52, 6228-6232.
4
4
4
5
5
0.J. Liang, X. Zhang, L. Jing and H. Yang, Chin. J. Catal., 76.G. Yuan, M. Gopiraman, H. J. Cha, H. D. Soo, I.-M.
2
017, 38, 1252-1260.
Chung and I. S. Kim, J. Ind. Eng. Chem., 2017, 46, 279-
1.X. Wang, X. Huang, W. Gao, Y. Tang, P. Jiang, K. Lan,
288.
R. Yang, B. Wang and R. Li, J. Mater. Chem. A, 2018, 6, 77.M. Gopiraman and I. M. Chung, J. Taiwan Inst. Chem. E.,
684-3691.
2017, 81, 455-464.
2.I. S. Pieta, A. Rathi, P. Pieta, R. Nowakowski, M.
Hołdynski, M. Pisarek, A. Kaminska, M. B. Gawande and
R. Zboril, Appl. Catal. B-Environ., 2019, 244, 272-283.
3.M. J. Lima, A. M. T. Silva, C. G. Silva and J. L. Faria, J.
Catal., 2017, 353, 44-53.
4.X. Hu, Y. Long, M. Fan, M. Yuan, H. Zhao, J. Ma and Z.
Dong, Appl. Catal. B-Environ., 2019, 244, 25-35.
5.Y. Zheng, L. Lin, X. Ye, F. Guo and X. Wang, Angew.
Chem. Int. Ed., 2014, 53, 11926-11930.
6.T. S. Miller, A. B. Jorge, T. M. Suter, A. Sella, F. Cora
and P. F. McMillan, Phys. Chem. Chem. Phys., 2017, 19,
3
5
5
5
5
5
1
5613-15638.
5
5
5
7.L. Xu, J. Xia, H. Xu, S. Yin, K. Wang, L. Huang, L. Wang
and H. Li, J. Power Sources, 2014, 245, 866-874.
8.S. Ren, C. Chen, Y. Zhou, Q. Dong and H. Ding, Res.
Chem. Intermediat., 2016, 43, 3307-3323.
9.X. Fu, S. Wu, Z. Li, X. Yang, X. Wang, L. Peng, J. Hu, Q.
Huo, J. Guan and Q. Kan, RSC Adv., 2016, 6, 57507-
5
7513.
6
6
6
6
6
6
6
0.H.-C. Ma, J.-L. Kan, G.-J. Chen, C.-X. Chen and Y.-B.
Dong, Chem. Mater., 2017, 29, 6518-6524.
1.K. Umemura, A. Takahashi and S. Kawai, J. Wood Sci.,
1
998, 44, 204-210.
2.T. Sun, H.-Y. Jiang, C.-C. Ma, F. Mao and B. Xue, Catal.
Commun., 2016, 79, 45-48.
3.D. Roşu, F. Mustaă and C. N. Caşcaval, Thermochim.
Acta, 2001, 370, 105-110.
4.K. S. Anseth, C. M. Wang and C. N. Bowman,
Macromolecules, 1994, 27, 650-655.
5.P. Jiang, X. Li, W. Gao, X. Wang, Y. Tang, K. Lan, B.
Wang and R. Li, Catal. Commun., 2018, 111, 6-9.
6.S. Frindy, A. Primo, H. Ennajih, A. El Kacem Qaiss, R.
Bouhfid, M. Lahcini, E. M. Essassi, H. Garcia and A. El
Kadib, Carbohydr. Polym., 2017, 167, 297-305.
7.F. Sun, H. Wu, X. Liu, F. Liu, H. Zhou, J. Gao and Y. Lu,
Nano Res., 2016, 9, 3209-3221.
6
6
8.Z. Liu, F. Sun, L. Gu, G. Chen, T. Shang, J. Liu, Z. Le, X.
Li, H. B. Wu and Y. Lu, Adv. Energy Mater., 2017, 7,
1
701154.
2
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