N-Doped porous carbon supported palladium nanoparticles as a highly efficient and recyclable catalyst for the Suzuki coupling reaction

Article abstract of DOI:10.1016/j.cclet.2015.08.007

A new catalyst, Pd particles supported on the N-doped porous carbon (PC) derived from Zn-based metal-organic frameworks (zeolitic imidazolate framework: ZIF-8), was successfully prepared for the first time. The as-prepared catalyst was designated as N-doped PC-Pd, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscope, N₂ adsorption and inductively coupled plasma atomic emission spectroscopy. The N-doped PC-Pd composite exhibited high catalytic activity toward the Suzuki-Miyaura cross-coupling reactions. The yields of the products were in the range of 90%-99%. The catalyst could be readily recycled and reused at least 6 consecutive cycles without a significant loss of its catalytic activity.

Full text of DOI:10.1016/j.cclet.2015.08.007

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CCLET 3410 1–6
Chinese Chemical Letters xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
1
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Original article
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N-Doped porous carbon supported palladium nanoparticles as a highly
efficient and recyclable catalyst for the Suzuki coupling reaction
*
*
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Q1 Li Zhang, Wen-Huan Dong, Ning-Zhao Shang, Cheng Feng, Shu-Tao Gao , Chun Wang
College of Science, Agricultural University of Hebei, Baoding 071001, China
A R T I C L E I N F O
A B S T R A C T
Article history:
A new catalyst, Pd particles supported on the N-doped porous carbon (PC) derived from Zn-based metal–
organic frameworks (zeolitic imidazolate framework: ZIF-8), was successfully prepared for the first time.
The as-prepared catalyst was designated as N-doped PC-Pd, and characterized by X-ray diffraction, X-ray
photoelectron spectroscopy, transmission electron microscopy, scanning electron microscope, N2
adsorption and inductively coupled plasma atomic emission spectroscopy. The N-doped PC-Pd
composite exhibited high catalytic activity toward the Suzuki–Miyaura cross-coupling reactions. The
yields of the products were in the range of 90–99%. The catalyst could be readily recycled and reused at
least 6 consecutive cycles without a significant loss of its catalytic activity.
Received 25 May 2015
Received in revised form 16 July 2015
Accepted 21 July 2015
Available online xxx
Keywords:
Suzuki–Miyaura coupling reaction
Pd catalyst
ß 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.
Published by Elsevier B.V. All rights reserved.
N-Doped nanoporous carbon
Metal–organic frameworks
7
8
1. Introduction
Currently, nitrogen-doped porous carbon (N-doped PC), as a 29
kind of novel material, has attracted considerable attention. N- 30
9
Palladium-catalyzed Suzuki–Miyaura cross-coupling reactions
of aryl halides with aryl boronic acids have been accredited as one
of the most powerful and convenient synthetic tools to synthesize
Doped PC promises a wide range of applications in many fields 31
because the incorporation of nitrogen atoms in the carbon 32
architecture can enhance chemical, electrical, and functional 33
properties. Furthermore, thanks to the activation of neighboring 34
carbon atoms caused by the electron affinity of nitrogen, the 35
presence of doped nitrogen heteroatoms on carbon support could 36
stabilize the noble metal (e.g., Pd, Pt) nanoparticles, which is rather 37
beneficial for heterogeneous catalysts [15,16]. In general, N-doped 38
PC has conventionally been synthesized via chemical vapor 39
deposition, arc-discharge/vaporization approach and plasma 40
treatment under an NH3 atmosphere or in the presence of other 41
nitrogen sources such as pyridine and acetonitrile [17]. However, 42
these methods often encounter one or more shortcomings, such as 43
rigorous, tedious and multistep preparative processes, and the 44
resulting N-doped PC materials often have poor control to the 45
loading amount of nitrogen, and tend to have low chemical 46
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unsymmetrical bi-aryl compounds [1]. Recently, as
a new
generation of heterogeneous catalysts for the Suzuki coupling
reaction, immobilization of Pd nanoparticles on solid supports has
received considerable attention because of their superior catalytic
performance, good stability, ease of separation and satisfactory
reusability in comparison to the traditional homogeneous cata-
lysts, such as Pd(OAc)2 and PdCl2 [2–6]. Generally, the solid
supports, especially carbon nanomaterials such as activated
carbon [7], carbon molecular sieve [8], fullerene [9], carbon
nanotube [10], nanofiber and graphene [11], have been used as the
support for heterogeneous palladium catalysts [12,13]. However,
noble metals (e.g., Pt, Pd, and Ru) deposited on these carbon
nanomaterials can easily leach during the catalytic processes
because the interaction between the metal nanoparticles and the
carbon support is weak, and also the chemical or catalytic
properties of the traditional carbon supports do not always satisfy
the sharply increasing demands of catalysis [9,14].
homogeneity and disordered structures [18].
47
Recently, metal–organic frameworks (MOFs) resulting from 48
periodically arranged organometallic complexes have emerged as 49
a new family of solid matrices for use as hard templates for the 50
casting of porous carbons owing to their high specific surface area 51
and porosity, chemical tunability, and well-defined pore structure 52
[14,19–25]. Moreover, since the organic ligands contain various 53
types of atoms (N, O, P or S, etc.) other than carbon, MOFs might be a 54
kindofpromisingcandidateforthe fabricationofheteroatom-doped 55
*
Corresponding author.
E-mail addresses: gst824@163.com (S.-T. Gao), chunwang69@126.com
(C. Wang).
http://dx.doi.org/10.1016/j.cclet.2015.08.007
1001-8417/ß 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: L. Zhang, et al., N-Doped porous carbon supported palladium nanoparticles as a highly efficient and
recyclable catalyst for the Suzuki coupling reaction, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.08.007

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nanoporous carbon materials with uniformly distributed catalytic
centers and a highly active site density. So for, several MOFs
containing nitrogen have been demonstrated as promising self-
sacrificial templates to afford capacitance [17,24,30] and sensing
[28,31]. Zhao et al. synthesized an N-doped PC material by direct
carbonization of an amine to highly N-doped PC materials
[20,26,27]. The N-doped PC materials have found many applications
in gas adsorption [28,29], electrochemical functionalized alumi-
num-based MOF (amino-MIL-53). The obtained material was used
as metal-free, electro-catalysts for oxygen reduction reactions [19].
N-doped PC derived from zeolitic imidazolate framework 8 (ZIF-8)
nanocrystals has also been used as efficient electro-catalysts for
oxygen reduction reactions [18]. However, the application of MOF-
derived N-doped PC in heterogeneous catalysis is still very limited.
In continuation of our interest in exploring efficient catalysts for
organic transformations [2,32,33], in this paper, N-doped PC was
fabricated by a one-step, direct, carbonization of ZIF-8, which
serves as the nitrogen source, the carbon source, as well as the hard
template. After that, Pd nanoparticles were supported on the as-
prepared N-doped PC. In order to evaluate the catalytic activity of
the catalyst, the Suzuki–Miyaura coupling reaction was chosen as
the model reaction.
Scheme 1. The preparation process of the catalyst and the Suzuki coupling reaction.
resultant was dispersed in 10 mL water, then 11 mg sodium
borohyride (NaBH4, 0.027 mmol) was added to the solution. The
pH of the mixture was adjusted to 10 with a 10% sodium hydroxide
solution and the reaction was carried out at 98 8C for 2 h. The
obtained solid, N-doped PC-Pd, was washed with water and dried
in vacuum at 50 8C.
For the preparation of Zn-free N-doped PC-900-Pd, 100 mg of N-
doped PC-900 powder was suspended in 35 mL of 10% HCl solution
and held for 5 h, and then the mixture was filtered and washed
with distilled water. Finally, the N-doped PC-900 without ZnO or
Zn was obtained by vacuum drying at 80 8C overnight.
The Zn-free N-doped PC-900-Pd was fabricated according to the
same procedure mentioned above except that 50 mg N-doped PC
was replaced by 50 mg Zn-free N-doped-900-PC.
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2. Experimental
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2-Methylimidazole (99%, MIm), aryl boronic acids, aryl halides,
and palladium chloride (PdCl2) were purchased from Aladdin
Reagent Limited Company and used as received. Sodium hydrox-
ide, Zn(NO3)2Á6H2O (99%) and sodium borohydride were obtained
from Chengxin Chemical Reagents Company (Baoding, China) and
used without further purification. Methanol and ethanol were
provided by the Boaixin Co., Ltd. (Baoding, China).
The size and morphology of the catalyst was observed by
scanning electron microscopy (SEM) using a FEI Quanta 200F field
emission electron microscope operated at 30 kV. The transmission
electron microscopy (TEM) was acquired using a JEOL model JEM-
2011(HR) at 200 kV. The X-ray diffraction (XRD) patterns of the
To a 25 mL round-bottom flask, aryl halide (0.5 mmol),
phenylboronic acid (0.6 mmol), base (1.5 mmol), solvents (EtOH/
H2O = 1:1, v/v, 4 mL) and a certain amount of the catalyst N-doped
PC-Pd were added and stirred at r.t. After a desired reaction time,
the mixture was diluted with 10 mL of H2O and extracted with
diethyl ether (3Â 10 mL). The organic layers were combined, dried
over anhydrous MgSO4 and filtered. Then the filtrate was
concentrated by vacuum. The pure products were obtained by
flash chromatography using petroleum ether:ethyl acetate (9:1) as
the eluent. The preparation process of the catalyst and the Suzuki
coupling reaction were illustrated in Scheme 1.
samples were recorded with
diffractometer using Cu K radiation (40 kV, 150 mA) in the range
2u = 10–808. The Brunauer–Emmett–Teller (BET) surface area and
a Rigaku D/max 2500 X-ray
a
porous structure were measured using V-Sorb 2800P. After the
samples were degassed in vacuum at 120 8C for 6 h, the nitrogen
adsorption and desorption isotherms were measured at 77 K. X-ray
photoelectron spectroscopy (XPS) was performed with a PHI
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3. Results and discussion
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1600 spectroscope using Mg K
a
X-ray source for excitation. The Pd
In order to explore the pore structure of N-doped PC samples,
the nitrogen adsorption and desorption isotherms were recorded
at 77 K. As detailed in Table 1, with increasing the carbonization
temperature from 700 8C to 900 8C, the experimental multipoint
BET surface area of the N-doped PC increased from 416 to
740 cm3 gÀ1 and the total adsorption average pore width also
increased to 5.0 nm. However, the BET then slightly decreased to
720 cm3 gÀ1 and the total adsorption average pore width increased
to 7.0 nm when the carbonization temperature was 1000 8C. The
reason may probably be due to the cleavage of C-N and escape of
nitrogen as well as the further graphitization of the carbon
framework at high temperature [18,34]. Additionally, it is also
worth noting that the BET surface area of N-doped PC-900
increased from 740 to 850 cm3 gÀ1 after the removal of Zn
impurities by washing with HCl. Since the N-doped PC was
fabricated from the ZIF-8 precursor originating from a carboniza-
tion process, the morphology and pore texture of the parent MOF
may well be inherited and even enhanced [18].
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content of the catalyst was determined by means of inductively
coupled plasma atomic emission spectroscopy (ICP-AES) on
Thermo Elemental IRIS Intrepid II.
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The ZIF-8 nanocrystals were prepared according to the reported
synthesis protocol [18]. Typically, a solution of Zn(NO3)2Á6H2O
(2.348 g, 7.89 mmol) in 160 mL of methanol is rapidly poured into
a solution of 2-methylimidazole (5.192 g, 63.24 mmol) in 160 mL
of methanol under magnetic stirring. The mixture was stirred at
room temperature for 1 h. The solid product was separated from
the milky colloidal dispersion by centrifugation. After washing
with methanol three times, the white ZIF-8 product was dried in a
vacuum at 60 8C for 2 h. For the synthesis of N-doped PC, the
carbonization of the ZIF-8 was performed at 700, 800, 900, 1000 8C
for 8 h with an Ar flow, respectively. The resulting products were
denoted as N-doped PC-700, N-doped PC-800, N-doped PC-900,
and N-doped PC-1000, respectively.
Pd nanoparticles were immobilized on the N-doped PC by an
impregnation method.
A
100 mg N-doped PC sample was
The TEM and SEM images of Zn-free N-doped PC-900 and Zn-
free N-doped PC-900-Pd samples are shown in Fig. 1. Comparing
with Fig. 1A and B, it can be clearly seen that the Pd nanoparticles
were highly dispersed on the surface of Zn-free N-doped PC-900.
dispersed in 10 mL (1 mg/mL) chlorine palladium acid solution,
and then the solution was stirred overnight. After filtration, the
solid was washed with water and dried under vacuum at 70 8C. The
Please cite this article in press as: L. Zhang, et al., N-Doped porous carbon supported palladium nanoparticles as a highly efficient and
recyclable catalyst for the Suzuki coupling reaction, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.08.007

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Table 1
The nitrogen adsorption–desorption isotherm and pore size distributions of the N-doped PC.
Catalyst
Surface area (m2 gÀ1
BET method
)
Total adsorption
SF median pore
width (nm)
Total pore
volume (cm3 gÀ1
)
average pore width (nm)
Langmuir method
N-doped PC-700
416
572
740
722
850
600
560
770
3.8
3.9
5.0
7.0
6.7
3.5
0.74
0.77
0.78
0.75
0.79
0.76
0.7
N-doped PC-800
0.7
N-doped PC-900
1010
970
0.65
1.2
N-doped PC-1000
Zn-free N-doped PC-900
Zn-free N-doped PC-900-Pd
1150
850
0.76
0.6
Fig. 1. TEM images of (A) Zn-free N-doped PC-900, (B) Zn-free N-doped PC-900-Pd and SEM image (C) of Zn-free N-doped PC-900-Pd.
Pd0d
8000
7500
7000
6500
6000
5/ 2
pyridinic-N
graphitic-N
9500
9000
8500
8000
7500
7000
6500
6000
5500
Pd0d3/ 2
Pd2+ d5/2
Pd2+ d3/2
A
B
335
340
345
395
400
405
Binding energy / eV
Binding energy / eV
Fig. 2. The XPS image of Zn-free N-doped PC-900.
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The average size of the Pd nanoparticles is 3.6 nm. The results
indicated that the high BET and the pore volume of Zn-free N-
doped PC-900 promote the dispersion of Pd. Besides, nitrogen in
the composite also plays an important role to improve the
dispersability of Pd nanoparticles. It also can be clearly seen from
the SEM image (Fig. 1C) that some of the Pd NPs were supported on
the surface of the Zn-free N-doped PC-900, and part of them
inserted into the cavities of Zn-free N-doped PC-900. The
palladium content in Zn-free N-doped PC-900-Pd was determined
by means of ICP-AES and amounted to 4.03 wt%.
The XPS spectra (Fig. 2A) demonstrated that the Pd species in
the Zn-free N-doped PC-900-Pd sample are present in the metallic
state with the bond energy about 335.5 and 340.98 eV in the Pd
3d5/2 and 3d3/2 core level, and Pd 3d spectrum can be deconvoluted
to four sub-peaks, containing Pd0 3d3/2 (334.7 eV), Pd0 3d5/2
(340.1 eV), Pd2+ 3d3/2 (341.2 eV) and Pd2+ 3d5/2 (336.1 eV)
[35,36]. Moreover, the high resolution nitrogen (N) 1s spectrum
can be deconvoluted to two sub-peaks due to the spin orbit
coupling, including pyridinic-N (398.51 eV) and graphitic-N
porous carbon [39]. The well-defined peaks around 408, 478, 688 194
and 838 can be assigned to (1 1 1), (2 0 0), (2 2 0) and (3 1 1) crystal 195
planes of Pd0 in the composite.
196
In order to investigate the catalytic activity of different catalysts 197
for the C–C coupling reaction, the coupling of phenylbromide and 198
phenylboronic acid was selected as a model reaction. As shown in 199
Table 2, among the catalysts tested at room temperature, Zn-free 200
N-doped PC-900-Pd was found to be the most effective catalyst 201
since it gave the highest yield of product. Good dispersion of the 202
active species (Pd) on the support is a key factor for the catalytic 203
1000
Pd
800
C
600
400
Pd
Pd
(400.98 eV) [37,38], which is
a common characteristic for
Pd
200
nitrogen-doped carbon materials. In general, nitrogen in a carbon
texture is suitable for stabilizing highly dispersed metal nano-
particles. The nitrogen content in Zn-free N-doped PC-900-Pd was
determined by means of XPS and amounted to 10 wt%.
Fig. 3 displays the XRD pattern of Zn-free N-doped PC-900-Pd
composite. The wide diffraction peak at 2u = 258 can be indexed to
0
20
40
60
80
2 Theta / degree
Fig. 3. XRD patterns of Zn-free N-doped PC-900-Pd. C: porous carbon.
Please cite this article in press as: L. Zhang, et al., N-Doped porous carbon supported palladium nanoparticles as a highly efficient and
recyclable catalyst for the Suzuki coupling reaction, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.08.007

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Table 2
Table 3
Suzuki–Miyaura coupling reactions catalyzed by different catalysts.
Optimization of the reaction conditions for the Suzuki reaction of bromobenzene
with phenylboronic acid.a
Entry
Catalyst
Yield (%)
Entry
Solvents
Base
Pd (mol%)
Yield (%)
1
2
3
4
5
N-doped PC-700-Pd
N-doped PC-800-Pd
N-doped PC-900-Pd
N-doped PC-1000-Pd
Zn-free N-doped PC-900-Pd
54
73
91
77
95
1
EtOH
K2CO3
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
–
63
53
17
81
72
95
55
43
85
68
37
0
2
MeOH
K2CO3
3
H2O
K2CO3
4
EtOH:H2O = (3:1)
EtOH:H2O = (1:3)
EtOH:H2O = (1:1)
EtOH:H2O = (1:1)
EtOH:H2O = (1:1)
EtOH:H2O = (1:1)
EtOH:H2O = (1:1)
EtOH:H2O = (1:1)
EtOH:H2O = (1:1)
EtOH:H2O = (1:1)
EtOH:H2O = (1:1)
K2CO3
5
K2CO3
n
(K2CO3): n (aryl iodide): n (phenylboronic acid) = 4:1:1.3; solvent: 2 mL
6
K2CO3
ethanol + 2 mL H2O; the quantity of catalyst was 0.15 mol%; room temperature.
7
KOH
8
NaOH
9
Na2CO3
NaHCO3
Triethylamine
K2CO3
204
205
206
207
208
209
210
activity of the catalyst. This is mainly due to the high surface area of
Zn-free N-doped PC-900, which leads to high dispersion of Pd on
the surface of support. Additionally, the presence of nitrogen
element in the carbon texture was also helpful to increase the
dispersion of the active species.
10
11
12
13
14
K2CO3
0.10
0.20
68
97
K2CO3
a
To evaluate the catalytic performance of the as-obtained
catalyst and optimize the reaction conditions of the Suzuki
Reaction conditions: bromobenzene (0.5 mmol), phenylboronic acid
(0.75 mmol), base (1.5 mmol), solvents (4 mL), room temperature.
Table 4
Suzuki–Miyaura coupling of aryl boronic acids and aryl halides catalyzed by N-doped PC-900-Pd.a
Entry
1
Aryl halides
Aryl boronic acids
T (h)
Yield (%)b
95
1
B(OH)
Br
2
2
3
1.5
2
91
92
Br
CH3
B(OH)2
CH
3
B(OH)2
Br
4
1
95
99
94
96
90
Br
OH
B(OH)2
B(OH)2
B(OH)2
B(OH)2
5c
6
0.5
1
Br
Br
Br
NO
2
COH
7
1
COCH
3
8
1
F
B(OH)
2
Br
Br
Br
OCH3
9
1
1
92
91
O N
2
B(OH)
2
OCH3
10
CH
3
NO
2
B(OH)
2
11c
1
92
H C
3
Br
NO
2
B(OH)
2
12
13
1
1
94
95
Br
COH
F
B(OH)
2
O2N
B(OH)2
Br
OH
14d
15d
8
8
17
B(OH)
Cl
2
Trace
B(OH)
H C
Cl
2
3
a
Reaction conditions: bromobenzene (0.5 mmol), phenylboronic acid (0.6 mmol), K2CO3 (1.5 mmol), solvent: 2 mL ethanol + 2 mL H2O, catalyst: Zn- free N-doped PC-900-
Pd (0.2 mol%), room temperature.
b
Isolated yield based on column chromatography.
c
The reaction temperature is 50 8C.
The reaction temperature is 75 8C.
d
Please cite this article in press as: L. Zhang, et al., N-Doped porous carbon supported palladium nanoparticles as a highly efficient and
recyclable catalyst for the Suzuki coupling reaction, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.08.007

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coupling reaction, the reaction between phenylbromide and
phenylboronic acid was chosen as model reaction. Initially, single
solvents, such as EtOH, MeOH, and H2O, were studied. As
documented in Table 3, the single solvents gave low yields for
the reaction (Table 3, entries 1–3). However, when we adopted the
organic/aqueous co-solvent, high yields of 72–95% were obtained
(Table 3, entries 4–6). The beneficial effect of the co-solvent may be
attributed to the good solubility of the organic reactants and the
inorganic base, so EtOH:H2O (1:1, v/v) was chosen as the reaction
solvent for the subsequent reactions. As is well known, a base has a
strong influence on Suzuki reactions. When the organic and
inorganic bases, such as Et3N, K2CO3, Na2CO3, NaOH, KOH, NaHCO3,
were taken into consideration for the Suzuki coupling reaction
(Table 3, entries 7–11), the experiments showed that K2CO3, as a
base, afforded the product in the highest yield. It was also
determined that the amount of the catalyst has a great influence on
the transformation (Table 3, entries 6, 12–14), and the best results
were obtained with 0.15 mol% of catalyst. When the amount of the
catalyst was increase to 0.20 mol%, the product was obtained in a
nearly quantitative yield (Table 3, entry 14). However, the yield of
the reaction decreased to 68% (Table 3, entry 13) in 0.10 mol% Pd,
and the coupling reaction does not proceed at all in the absence of
Pd nanoparticles (Table 3, entry 12).
After optimizing the reaction conditions, the catalytic activity of
Zn-free N-doped PC-900-Pd for the Suzuki–Miyaura reaction was
explored with respect to various aryl halides and phenylboronic
acids. It was found that the catalyst showed a high reactivity and
selectivity for aryl bromides with an electron-withdrawing group
and electron-donating group. As shown in Table 4, the coupling
reactions could be proceeded well and the reactions could be
completed in 0.5–2 h at room temperature with good to excellent
yields. Typically, compared with the electron-donating groups on
aryl bromides, such as –CH3, –OCH3 (Table 4, entries 2–3, 8–9), the
electron-withdrawing groups, such as –COCH3, –OH (Table 4,
entries 4–7, 11–13), have higher reaction activity. To test the
feasibility of the aforementioned protocol for challenging sub-
strates, several aryl chlorides with aryl boronic acids were
employed and the reaction time was increased to 8 h. Unfortu-
nately, the catalytic system was less effective for the reaction of
aryl chlorides (Table 4, entries 14 and 15) because of the strong
strength of the C–Cl bond, whose bond dissociation energy was
96 kcal/mol [40].
area and pore volume of Zn-free N-doped PC-900. Additionally, the 260
nitrogen element in carbon texture also plays an important role for 261
stabilizing highly dispersed Pd nanoparticles. Therefore, the Zn- 262
free N-doped PC-900 catalyst exhibits both excellent catalytic 263
activity and good reusability.
264
4. Conclusion
265
In summary, we have demonstrated the fabrication of nitrogen- 266
doped carbon by a facile, low-cost and readily reproducible 267
approach using ZIF-8 as precursor, and the prepared N-doped PC 268
was used as the carrier material for palladium nanoparticle. The 269
resultant Zn-free N-doped PC-900-Pd offers high surface area and 270
exhibits a significant activity toward the Suzuki coupling reaction 271
between aryl halide and aryl boronic acid, even when the reaction 272
was carried out at room temperature for a relatively short time. 273
Moreover, good yields were obtained even after the Zn-free N- 274
doped PC-900-Pd catalyst was reused six times. The present 275
research might highlight the development of high catalytic activity 276
heterogeneous catalysts by using MOF-derived porous carbon as 277
hosts for ultrafine metal nanoparticles.
278
Acknowledgments
279
This work was financially supported by the National Natural Q2280
Science Foundation of China (Nos. 31171698, 31471643), the 281
Innovation Research Program of Department of Education of Hebei 282
for Hebei Provincial Universities (LJRC009), Natural Science 283
Foundation of Hebei Province (B2015204003) and the Natural 284
Science Foundation of Agricultural University of Hebei (LG201404, 285
ZD201506).
286
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Please cite this article in press as: L. Zhang, et al., N-Doped porous carbon supported palladium nanoparticles as a highly efficient and
recyclable catalyst for the Suzuki coupling reaction, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.08.007