Selective Semihydrogenation of Alkynes Catalyzed by Pd Nanoparticles Immobilized on Heteroatom-Doped Hierarchical Porous Carbon Derived from Bamboo Shoots

Article abstract of DOI:10.1002/cssc.201701127

Highly dispersed palladium nanoparticles (Pd NPs) immobilized on heteroatom-doped hierarchical porous carbon supports (N,O-carbon) with large specific surface areas are synthesized by a wet chemical reduction method. The N,O-carbon derived from naturally abundant bamboo shoots is fabricated by a tandem hydrothermal–carbonization process without assistance of any templates, chemical activation reagents, or exogenous N or O sources in a simple and ecofriendly manner. The prepared Pd/N,O-carbon catalyst shows extremely high activity and excellent chemoselectivity for semihydrogenation of a broad range of alkynes to versatile and valuable alkenes under ambient conditions. The catalyst can be readily recovered for successive reuse with negligible loss in activity and selectivity, and is also applicable for practical gram-scale reactions.

Full text of DOI:10.1002/cssc.201701127

Accepted Article
Title: Efficient and Chemoselective Semihydrogenation of Alkynes
Catalyzed by Pd Nanoparticles Immobilized on Heteroatom-
Doped Hierarchical Porous Carbon Derived from Bamboo Shoots
Authors: yong yang, Guijie Ji, Yanan Duan, Shaochun Zhang, Benhua
Fei, and Xiufang Chen
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To be cited as: ChemSusChem 10.1002/cssc.201701127
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ChemSusChem
10.1002/cssc.201701127
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Efficient and Chemoselective Semihydrogenation of Alkynes
Catalyzed by Pd Nanoparticles Immobilized on Heteroatom-
Doped Hierarchical Porous Carbon Derived from Bamboo Shoots
Guijie Ji,‡ Yanan Duan,‡ Shaochun Zhang, [a] Benhua Fei, [b] Xiufang Chen * and Yong Yang* ,
[
a]
[a]
[a]
[a]
Dedication ((optional))
Abstract: Highly dispersed palladium nanoparticles (Pd NPs)
immobilized by a heteroatom-doped hierarchical porous carbon
support (N,O-Carbon) with large specific surface areas are
synthesized by a wet chemical reduction method, wherein the N,O-
Carbon derived from naturally available and reusable bamboo shoots
is fabricated by a tandem hydrothermal-carbonization process
without assistance of any templates or chemical activation reagents
or exogenous N and O source in a simple and eco-friendly manner.
The prepared Pd@N,O-Carbon catalyst shows extremely high activity
and excellent chemoselectivity for semihydrogeantion of a broad
range of alkynes to versatile and valuable alkenes under ambient
conditions. The catalyst can be readily recovered for successive
reuse with negligible loss in activity and selectivity and is also
applicable for gram-scale transformation, which highlights its highly
practical potential.
its powerful dissociation capability for
H
2
,
in particular
heterogeneous Pd nanoparticles (NPs) catalysts have been
extensively exploited for the selective partial hydrogenation due
to their potential reusability and recyclability for practical
[
10]
3
applications. In this context, Lindlar catalyst (Pd/CaCO treated
with Pb salts and quinoline) has been widely used industrially but
suffers from serious drawbacks including the requirement of a
toxic lead salt, the addition of large amount of quinoline to
suppress the over-hydrogenation of the product alkenes, limited
substrate scope, and low alkene selectivity for terminal alkynes
as well, which significantly restricts it from wider and new
applications.[
1a,1b,1e]
To address these issues, a variety of heterogeneous Pd NPs
catalysts with different preparation strategies have been
developed. For example, Donkervoort[11] in BASF developed a
novel supported ligand-modified Pd catalysts (0.5 wt% Pd
supported on activated carbons or titanium silicate;
NanoSelectTM), which is now commercialized. Kaneda[
reported several core-shell nanocomposite Pd catalysts for the
12]
Introduction
selective semihydrogenation of alkynes, e.g. Pd@MPSO/SiO
catalyst consisting of Pd nanoparticles (NPs) in the core and a
DMSO-like matrix in the shell, core-Pd/shell-Ag nanocomposite
catalyst. Lipshutz and co-workers[13] developed an elegant Pd
nanoparticle-nanomicelle combination systems for the
stereoselective hydrogenation in water. Bäckvall[14] reported
2
Semihydrogenation of alkynes to alkenes is one of the most
important and fundamental reactions in manufacturing processes
of bulk and fine chemicals.[1] To date, the chemoselective
semihydrogenation of alkynes still remains a grand challenging
due to the easy overreduction of alkenes to undesired alkanes.
Both catalytic hydrogenation in the presence of molecular
hydrogen and catalytic transfer hydrogenation using water[2a-c] or
supported Pd NPs on amino-functionalized mesoporous hallow
silica nanospheres for Z-selective semihydrogenation of alkynes.
organic hydrogen donors, such as alcohols,[2d] carboxylic acids,[2e-
[15]
Sajiki and co-workers developed Pd on boron nitride catalyst.
g]
amines,[2h-i] and silanes[2j-l] have been frequently employed to
[16]
In addition, Yan, Lu and their co-workers recently reported the
realize this transformation. Nonetheless, the semihydrogenation
of alkynes using hydrogen is the most preferable choice because
of its high atom-economic and environmental benefits.
Pd-Pb alloy octahedral nanocrystals with tailored shapes and
compositions for the selective semihydrogenation of alkynes.
Obviously, all these efforts were considerably dedicated to
elaborately tuning Pd NPs compositions and modulating the
interactions between metal and support, which have been widely
accepted as two of the most important methods for maximizing
catalytic selectivity in semihydrogenation.
With respect to the modulation of metal-and-support
interactions, incorporation of heteroatom into support lattices was
considered to be the most effective and straightforward method,
which allows to precisely tune chemical and electronic properties
of supports and in turn significantly affects the metal-and-support
interactions to eventually boost the activity and selectivity.[17] Most
recently, we developed heterogeneous Ir and Pt NPs supported
on different porous carbons in hydrogenation and oxidation
catalysis.[18] In the continuation of our interest in the fabrication of
porous carbon materials and their application in catalysis, herein,
A number of metal-based catalysts (e.g. Pd,[ Au,[4] Ru,[5] Cu,[6]
3]
Ni,[7] Fe,[8] Co ) have been developed for the catalytic
[9]
semihydrogenation of alkynes with H
Among these catalysts investigated,
predominantly chosen as the catalytically active species owing to
2
over the last decade.
palladium was
[
[
a]
b]
G.J. Ji; Y. N. Duan, S. C. Zhang, X. F. Chen, Y. Yang
CAS Key Laboratory of Bio-Based Materials, Qingdao Institute of
Bioenergy and Bioprocess Technology, Chinese Academy of
Sciences, Qingdao 266101, China.
E-mail: chenxf@qibebt.ac.cn; yangyong@qibebt.ac.cn
B. H. Fei
International Center for Bamboo and Rattan, Beijing 100102, China
‡These authors contributed equally.
Supporting information for this article is given via a link at the end of
the document.
we present
a
highly efficient and chemoselective
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ChemSusChem
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semihydrogenation of alkynes catalyzed by Pd NPs immobilized
on heteroatom-doped hierarchical porous carbon derived from
naturally renewable bamboo shoots.
Heteroatom-doped porous carbon materials derived from
biomass have recently attracted considerable attention because
of their unique properties such as high electrical conductivity,
large specific surface area, high porosity, and easy availability,
which are increasingly employed as appealing materials for
versatile applications in water purification, gas separation and
storage, catalysis and catalytic supports, and electrochemistry as
well.[ Up to now, the most frequently used methods to fabricate
heteroatom-doped porous carbons with high surface area are
post-treatment with heteroatom-containing sources and in-situ
doping by carbonization of heteroatom-rich precursors.[20] Both
methods generally require tedious and multi-step processes with
the assistance of hard/soft templates or the activation with
19]
considerable amounts of chemical reagents like KOH, ZnCl
2
,
H
3
PO , in which the processes are time, energy, and cost-
4
consuming along with massive waste production, thereby raising
the economic and environmental concerns. Bamboo shoots, as a
readily available and renewable biomass feedstock in nature,
have high content of carbon and oxygen and also enrich in
nitrogen-containing organics including proteins and amino
acids,[21] which make it to be a promising candidate to produce
heteroatom of oxygen (O) and nitrogen (N) dual-doped porous
carbon materials without using exogenous N/O sources after the
hydrothermal carbonization (HTC) process. Considering
sustainability and environmental concerns, it is a highly desirable
to develop a facile, green and eco-friendly synthetic method to
fabricate heteroatom-doped porous carbon materials using
bamboo shoots as naturally available and renewable source.
Figure 2. Characterization results of N,O-Carbon for SEM images
with different magnification (A & B), HR-TEM images (C & D),
Raman spectrum (E), and N
2
adsorption/desorption isotherms (F).
The inset shows the pore size distribution by NLDFT modeling.
The obtained carbon material showed
a
loose and
interconnected structure with interstitial porosity, which comprises
of numerous uniformly-distributed spherical nanoparticles with
size of around 40-70 nm as demonstrated by SEM and TEM
images (Figure 2(A)-(D)). X-ray diffraction (XRD) revealed a
graphitic carbon structure characteristic peaks at 23ºand 43º,
corresponding to (002) and (100) reflection planes (Figure 4(A)-
a). The formation of graphitic order was further proved by the
Results and Discussion
The novel N,O-dual-doped porous carbon materials were
synthesized by
a facile tandem hydrothermal-carbonization
processes in a simple, direct and environmentally-benign manner
without using any templates or chemical agents for activation for
the first time, to the best of our knowledge. Briefly, the fresh
bamboo shoots were firstly cut into slices, dried and ground into
powder followed by the hydrothermal process in a Teflon-inner
-1
Raman spectrum (Figure 2(E)), in which the G band at 1590 cm
2
indicates the in-plane vibration of the sp carbon atoms, while the
D band at 1350 cm-1 is a defect-induced nonperfect crystalline
o
structure of the material.[22] The I
stainless-steel autoclave with deionized water at 180 C. The
D G D G
/I (I and I signify the intensity
resulting brown solids were filtered, washed thoroughly with water
of D and G band) ratio of the porous carbon were determined to
be 1.19, indicative of a more disordered graphitic network
structure due to a relatively higher nitrogen percentage in the
to remove any residual of soluble metal ions such as Ca2 or K ,
+
+
and dried under vacuum and subsequently followed with
o
material.[23]
calcination at 850 C in N
2
flow to produce the porous carbons,
resulting
carbon
N
2
adsorption-desorption
denoted as N,O-Carbon (Figure 1).
characterizations (Figure 2(F)) indicated that the obtained
2
-1
material with large specific surface area (up to 1037 m g ), high
3
-1
pore volume (0.836 cm g ) and hierarchical micro-meso-
macroporous structure, which sufficiently allows it to be an ideal
support in catalysis. Elemental analysis (Table S1) showed that
up to 3.32% N content with considerable content of O (5.00%)
present in the carbon texture, which are suitable as basic
coordination sites for stabilizing highly dispersed Pd NPs and
Figure 1. Schematic illustration of the typical procedure for the
synthesis of N,O-Carbon.
0
preventing the reoxidation of Pd . XPS spectrum of N 1s core level
disclosed that nitrogen is embedded into
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ChemSusChem
10.1002/cssc.201701127
FULL PAPER
0.30
0.25
0.20
0.15
0.10
0.05
0.00
Figure 3. XPS spectra for N,O-Carbon. (A) survey spectrum, (B)
C 1s, (C) N 1S, and (D) O 1s.
9
10
11
Size
12
13
14
/
nm
the graphitic structure mainly in three forms, attributable to
pyridinic (398.6 eV), pyrrolic (399.8 eV), and quaternary nitrogen
[
24]
(
401.5 eV), respectively (Figure 3C). In addition, XPS spectra
of O 1s and C 1s showed various O and C functionalities such as
C=O, O-C-O, O=C-O, C-N, C=N in the lattice of carbon material
(
Figure 3 B & D).
Figure 4. (A) XRD patterns for (a) N,O-Carbon and (b) Pd@N,O-
Carbon, (B) Pd 3d XPS spectra for the catalyst Pd@N,O-doped
Carbon, (C & D) HR-TEM images of Pd@N,O-Carbon, and (E)
HAADF STEM image and elemental mapping of C, N, O and Pd.
The inset shows the Pd particle size distribution.
The supported Pd NPs on N,O-Carbon catalysts (denoted as
Pd@N,O-Carbon) were prepared by a typical wet chemical
impregnation and reduction method using hydrazine hydrate.
Upon immobilization of Pd NPs on N,O-Carbon, a doublet peak
corresponding to the Pd 3d5/2 and Pd 3d3/2 appeared in the XPS
Pd 3d spectra, in which the Pd 3d5/2 peak with a binding energy
of 335.9 eV is attributed to Pd0 (metallic palladium) with 81%
percentage, while the 3d5/2 peak at 337.5 eV is attributed to Pd2+
efficiently in alcohol as solvent (e.g. methanol, ethanol,
isopropanol) under atmospheric pressure of molecular hydrogen
at room temperature, affording complete conversion in excellent
selectivity to styrene within relatively short times (entries 1-3).
Under otherwise identical conditions, ethanol was the best choice
to outperform superior catalytic performance in terms of both
activity and chemoselectivity among all solvents investigated. For
comparison, commonly used activated carbon (AC with surface
(
Figure 4(B)). The presence of Pd2+ in Pd@N,O-Carbon can be
attributed to the oxidation of surface Pd NPs in air, because of its
high activity and strong interactions between the Pd precursors
2
+ [25]
and the N,O functionalities, making it difficult to reduce the Pd .
The formation of highly dispersed Pd NPs was proven by XRD
and high resolution transmission electron microscopy (HR-TEM).
It is notable that two diffraction peaks at 40.0º and 46.6º in the
XRD pattern show the characteristic (111) and (200) planes of Pd
NPs, respectively (Figure 4(A)-b). From the (111) diffraction peak
and Scherrer’s formula, the average size of the crystallites was
calculated to be 11.5 nm, in good agreement with the value
detected by HR-TEM (11.9 nm). The images of HR-TEM and
high-angle annular dark-field scanning TEM (HAADF-STEM)
2
-1
2 3 2 2
area of 1580 m g ) and other supports such as Al O , TiO , CeO
were also employed to prepare their corresponding supported Pd
NPs catalysts with roughly equal Pd loading (Table S2 in the
Supporting Information) and same preparation procedure. All
these obtained catalysts gave either low activity or poor selectivity
(
entries 11-14). In sharp contrast, the reaction rate and
chemoselectivity to styrene of the Pd@AC catalyst without any
heteroatom-doping was significantly slower than that of Pd@N,O-
Carbon under identical conditions after full conversion, indicating
the intrinsic nature of N,O-dual-doped hierarchical porous carbon
(
Figure 4 (E)) revealed that Pd NPs are homogeneously
distributed throughout the N,O-Carbon support, giving a relatively
narrow size distribution with a mean diameter size of 11.9 nm.
The lattice fingers of 0.223 and 0.190 nm were corresponding to
the (111) and (200) planes of Pd as shown in Figure 4 (D). The
loading of Pd supported on N,O-Carbon was determined to be
[26]
played a crucial role in catalysis. The catalyst loading can be
lowered to 0.03 mo% (1 mg of Pd@N,O-Carbon), in which the
reaction also took place smoothly to selectively produce styrene
while considerably longer times are needed (entry 15). However,
the reaction didn’t proceed at all with either the bare support N,O-
Carbon as catalyst or no catalyst (entries 15 and 16),
demonstrating the essential role of the catalyst in this
semihydrogenation reaction. Of note, the careful monitor of the
reaction progress to prevent over-reduction to ethylbenzene is
1
.64 wt% by ICP analysis.
The Pd@N,O-Carbon catalyst was employed in the batchwise
semihydrogenation of phenylacetylene as a model reaction to
optimize the reaction conditions (Table 1). The reaction
proceeded
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FULL PAPER
Table 1. Optimization of reaction conditionsa
Table 2. Semihydrogenation of various alkynes
a
Reaction conditions: 0.5 mmol phenylacetylene (1a), 5 mg (0.15 mol%
Pd) Pd@N,O-Carbon, 5 mL solvent, room temperature, 1 atm H
2
b
balloon. Determined by GC using dodecane as an internal standard
technique and compared with the corresponding authentic sample.
c
d
1
5
0 mg (0.30 mol%) catalyst. 1 mg (0.03 mol% Pd) Pd@N,O-Carbon.
e
f
mg support. without catalyst.
required to maximize the selectivity when the reaction is
approaching full conversion in the present system. To avoid such
tedious procedure, the addition of one equivalent of green
poisoning agents such as DMSO, or diethylenetriamine (DETA)
into the reaction mixture, which is frequently adapted to address
the trade-off between activity and selectivity for Pd NPs in
semihydrogenation, can indeed effectively suppress the
occurrence of over-reduction even when the reaction time was
prolonged reaction after full conversion (Figure S4), which is in
good line with the previous reports.14, 15
Pd@N,O-Carbon was also applicable to the semihydrogenation
of a wide range of terminal and internal alkynes, the results are
compiled in Table 2. Overall, the reactions proceeded in high
yields (>90%) with excellent selectivity to the desired alkenes for
a diverse array of alkynes under ambient conditions. Electron-
donating and electron-withdrawing substituents at the m-, o-, p-
positions on the phenyl ring of aromatic alkynes all gave high
yields to their corresponding alkenes. Reactions of m-, o-, p-
ethynyltoluenes (1b-d) or ethynylanisole (1e-g) proceeded well to
yield almost equal yields, suggesting that the steric effect of
substituents on aromatic rings is negligible. Gratifyingly,
phenylacetylenes bearing amine, hydroxyl, cyano, chloro, fluoro,
or ester substituents were all tolerated by this protocol, giving the
corresponding styrenes in >90% yield without any signs of side
products arising from reduction of these vulnerable functional
Reaction conditions: 0.5 mmol alkyne, 5 mg (0.15 mol% Pd)
Pd@N,O-Carbon, 5 mL EtOH, room temperature, 1 atm H
2
balloon. aDetermined by GC using internal standard technique
and compared with it corresponding authentic sample.
b
1
c
o
Determined by H NMR spectroscopy. 50 C, 15 mg (0.45 mol%)
Pd@N,O-Carbon. d40 C. 50 C, 10 mg (0.30 mol%) Pd@N,O-
o
e
o
Carbon.
groups (entries 8-12). However, in the case of 3-ethynylaniline
(1k), the reduction was found to proceed sluggishly and only 59%
yield with up to 99% selectivity to the corresponding alkene was
o
obtained under elevated temperature (50 C) and appreciably
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longer time (23 h). The nitrogen- containing alkyne, 3-
ethynylpyridine (1m), was hydrogenated in full conversion with 98%
selectivity within relatively shorter time, while the presence of
thiophene moiety in the alkyne (1n), remarkably decreased the
reaction rate and full conversion could be achieved after 12 h
under otherwise identical conditions, indicative of the possible
coordination between substrate and Pd NPs. Terminal aliphatic
alkynes even those containing functional groups, e.g. hydroxyl,
cyano, or ester, could be efficiently reduced into the
corresponding alkenes in high yields with excellent selectivity
1
00
100
80
60
40
20
0
80
6
4
2
0
0
0
0
1
2
3
4
5
6
(
entries 15-18). Notably, the conjugated terminal enyne, 1-
Recycling number
ethynylcyclohexene (1o), was hydrogenated to 2o in 95% yield;
the conjugated C=C double bond remained intact during the
reaction. In addition, the internal alkynes, such as 3-hexyne (1t),
Figure 5. Recyclability of the catalyst Pd@N,O-Carbon. Reaction
conditions: 0.5 mmol phenylacetylene (1a), 5 mg (0.15 mol% Pd)
4
-octyne (1u), diphenylacetylene (1v), 1-phenyl-1-butyne (1w), 3-
Pd@N,O-Carbon, 5 mL ethanol, room temperature, 1 atm H
balloon.
2
phenyl-2-propyn-1-ol (1x), the Pd@N,O-Carbon catalyst was
found to favor the formation of the cis alkene products, while
maintaining
a
low degree of over-reduction (<5%). All
disubstituted alkynes employed were smoothly converted to the
corresponding alkenes in high yields (>95%) (entries 19-24).
Durability/recyclability of a catalyst is critical for practical
applications. To test the durability of Pd@N,O-Carbon, the
catalyst was recollected, washed, and dried after completion of a
semihydrogenation experiment for subsequent cycles. As shown
in Figure 5, the activity and selectivity remained with negligible
changes after five recycling experiments, demonstrating the high
durability of this catalyst. The heterogeneity of Pd@N,O-Carbon
was further confirmed by several experiments. We carried out the
semihydrogenation of phenylacetylene and removed the catalyst
from the reaction mixture by filtration at approximately 55%
conversion of phenylacetylene. After removal of the Pd@N,O-
Carbon catalyst, the filtrate was again held under an atmosphere
Figure 6. Effect of removal of the Pd@N,O-Carbon catalyst
during the semihydrogenation of phenylacetylene (○) after
removal of Pd@N,O-Carbon and (●) without removal of Pd@N,O-
Carbon. The arrow indicates the time when the Pd@N,O-
of H . In this case, no additional semihydrogenation was observed, Carboncatalyst was removed from the reaction mixture. Reaction
2
indicating that leached Pd nanoparticles or other Pd-speices from
the catalyst (if any) are not responsible for the observed activity
conditions: 0.5 mmol phenylacetylene (1a), 5 mg (0.15 mol% Pd)
Pd@N,O-Carbon, 5 mL ethanol, room temperature, 1 atm H2
balloon.
(
Figure 6). It was confirmed by ICP-AES analyses that the
amounts of Pd that leached into the supernatant after the first run
were not detectable (below the detection limit). These tests rule
out the role of any leached Pd nanoparticles or other Pd-species
in catalysing semihydrogenation reaction. However, the Pd@AC
catalyst without any heteroatom-doping, which exhibited
considerably slower reaction rate and lower chemoselectivity as
discussed above, displayed a drastic decrease in activity in the
second successive recycle uses (Table S3), indicating the vital
roles of N,O-dual-doped hierarchical porous carbon for the strong
stability in catalysis.
Scheme 1. Gram-scale synthesis of styrene.
In addition, we also examined the practical utility of Pd@N,O-
Carbon for gram-scale synthesis. When phenylacetylene (10
mmol, 1.0 g) in ethanol (0.20 M) at room temperature under
atmospheric pressure of H
2
, styrene was obtained in 96% yield
(
1.0 g) after 7 h, as shown in Scheme 1. Worthy of notice, in this
case the TON was as high as 130,000 after 7 h. More importantly,
in the presence of an excess of styrene, phenylacetylene still can
be semi-reduced to styrene in full conversion with excellent
selectivity (Scheme 2). All these results highlight its highly
practical potential.
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ChemSusChem
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2
-1
Scheme 2. Demonstration of alkene purification using Pd@N,O-
Carbon. Reaction conditions: 0.5 mmol phenylacetylene (1a), 1.0
mmol styrene (2a), 5 mg (0.15 mol% Pd) Pd@N,O-Carbon, 5 mL
surface area of 1580 m g ) and other supports were prepared with the
same procedure.
2
ethanol, room temperature, 1 atm H balloon.
Typical Procedure for Semihydrogenation of alkynes
In a typical procedure, to a sealable Schlenk reaction tube equipped with
a magnetic stir bar was charged with 5 mg of Pd@N,O-Carbon catalyst.
The tube was then sealed with a rubber septum and was evacuated for a
while to remove air. Solvent and alkyne were injected via syringe into the
Conclusions
In conclusion, highly dispersed Pd nanoparticles have been
immobilized onto a new heteroatom-doped hierarchical porous
carbon with large specific surface area derived from naturally
available and renewable bamboo shoots, which was synthesized
by a tandem HTC process in a facile and eco-friendly manner
without assistance of templates or chemical activation reagents
or exogenous N sources. The supported Pd NPs catalyst is highly
active and chemoselective for semihydrogeantion of alkynes to
2
tube and the reaction was stirred under H balloon at room temperature.
The reaction was monitored by extracting an aliquot of the reaction mixture
for GC analysis during the reaction period. After completion of the reaction,
the reaction mixture was centrifuged. Finally, the products were identified
by gas chromatograph coupled with a mass spectrometer (GC-MS,
Shimadzu, 2010 plus).
Characterization
2
the desired alkenes using H as hydrogen source under ambient
conditions, is widely applicable to various alkynes including
aliphatic, aromatic, and terminal ones with good tolerance of a set
of functional groups, is capable of facile recycling, and allows for
large-scale transformation as well. Further studies regarding the
applications of metal NPs supported on such porous carbon
material are currently underway in our laboratory.
The X-ray diffraction (XRD) patterns of all the catalysts were obtained on
a Bruker D8 Advance X-ray diffraction diffractometer equipped with Cu Ka
radiation (λ= 1.5147 Å). The morphology of catalysts was examined by a
H-7600 transmission electron microscopy (TEM), a Tecnai G2 F30 high-
resolution TEM (HRTEM) and a FEI Tecnai G2 F20 scanning transmission
electron microscopy (STEM). Nitrogen adsorption–desorption data were
obtained on a Micromeritics ASAP 2020 static volumetric sorption analyzer.
The specific surface area of the samples was calculated by the Brunauer-
Emmet-Teller (BET) method. The micropore volume was calculated by t-
plot method. The pore size distributions were determined by non-local
density functional theory (NLDFT). The X-ray photoelectron spectroscopy
Experimental Section
(XPS) data was collected on an ESCALAB 250Xi (Thermo Scientific, UK)
Preparation of N,O-doped carbon (N,O-Carbon)
instrument equipped with a monochromatized Al Ka line source. All the
binding energies obtained were calibrated based on the C 1s peak at 284.8
eV. The elemental composition analysis of the catalysts was conducted on
Vario El elemental analyzer. Ion Chromatography was conducted on a
Thermo Scientific Dionex ICS-5000 equipped with CS-12 column with
methanesulfonic acid (20 mM) as an eluent. Raman spectra were obtained
on a Horiba Jobin Yvon LabRAM HR800 Raman spectrometer system
using a 532 nm wavelength laser at room temperature. Inductively coupled
plasma atomic emission spectroscopy (ICP-AES) was conducted on a
PerkinElmer Optima 5300 DV instrument.
The porous heteroatom doped carbon materials were prepared in two-
steps including hydrothermal treatment and carbonization process. The
fresh bamboo shoots were obtained from Anhui Taiping Test Centre,
International Centre for Bamboo and Rattan, Anhui Province, China. The
Bamboo shoots were firstly cut into slices and dried at 70 °C for 24 h. The
dried bamboo shoots (2 g) were then ground into powders and transferred
in a 100 mL Teflon-inner stainless-steel autoclave coupled with 20 ml of
deionized water. The autoclave was then heated to 180 °C and maintained
for 6 h. The resulting brown solids were filtered, washed by distilled water
thoroughly to remove any residual of soluble metal ions such as Ca2+ or
K+ (detected by ion chromatography), dried at room temperature under
o
vacuum for 24 h. After that, the hydrochars were calcined at 850 C for 4
Acknowledgements
-
1
2
h in N flow with a heating rate of 5 °C min . The black powder heteroatom
doped porous carbons were obtained and denoted as N.O-Carbon.
We gratefully acknowledge the start-up financial support from
Qingdao Institute of Bioenergy and Bioprocess Technology,
Chinese Academy of Sciences (NO. Y6710619KL). X. Chen also
acknowledges the financial support from 13th Five-Year the
National key R&D projects (2017YFD0600805).
Preparation of Pd nanoparticles supported on N,O-Carbon (Pd@N,O-
Carbon)
The porous heteroatom doped carbon supported Pd materials with metal
loading of 2.0 wt % were prepared by ultrasound-assisted reduction
method. 0.15
dispersed in 100 mL deionized water under ultrasonic condition for 30 min.
Then 3 g of 0.268 wt% of Pd(NO aqueous solution was added dropwise
g
porous heteroatom doped carbon materials were
Keywords: Supported Pd nanoparticles • semihydrogenation •
alkyne• carbon material • biomass
3 2
)
into the mixture and stirred vigorously for 1 h. After that, the pH value of
solution was adjusted to 11 using ammonia solution. The resulting solution
was put into 80 C oil bath with subsequent addition of 0.2 mL of hydrazine
solution (85%), which was further stirred vigorously for another 4 h. Finally,
the product was filtered and washed with deionized water and dried at
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10.1002/cssc.201701127
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Semihydrogenation
Guijie Ji, Yanan Duan, Shaochun
Direct fabrication of Heteroatom-doped HierarchicalPorous Carbon via a Simple
and Eco-friendlyProcess
Zhang, Benhua Fei, Xiufang Chen*, and
Yong Yang*
Pd@N,O-Carbon
1
atm H2 balloon
RT to 50oC
Pd NPs
Hydrothermal
process
Carbonization
immobilization
Page No. – Page No.
2
>
4 examples
90%selectivity
Efficient and Chemoselective
Semihydrogenation of Alkynes
Catalyzed by Pd Nanoparticles
Immobilized on Heteroatom-Doped
Hierarchical Porous Carbon Derived
from Bamboo Shoots
TONs up to 130,000
Broad functional groups tolerance
A
reusable supported Pd NPs for highly efficient and chemoselective
semihydrogenation of alkynes was developed. The Pd NPs was immobilized on
heteroatom-doped hierarchical porous carbon derived from naturally renewable
bamboo shoots, which allows for the conversion of a broad range of alkynes to the
corresponding alkenes under ambient conditions (1 atm H
good tolerance of diverse functional groups.
2
, room temperature) with
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