Controllable Sulfur, Nitrogen Co-doped Porous Carbon for Ethylbenzene Oxidation: The Role of Nano-CaCO3

Article abstract of DOI:10.1002/asia.201900086

Heteroatom-doped porous carbon materials have exhibited promising applications in various fields. In this work, sulfur, nitrogen co-doped carbon materials (SNCs) with abundant pore structure were prepared by pyrolysis of sulfur, nitrogen-containing porous organic polymers (POPs) mixed with nano-CaCO₃ at high temperature. Among the resultant materials, SNC-Ca-850 possesses a relatively high level of doped heteroatoms and exhibits an excellent catalytic performance for the selective oxidation of benzylic C?H bonds. It is noteworthy that nano-CaCO₃ increases the doped sulfur content in the synthesized carbon materials to a large extent and impacts the existence modes of sulfur. In addition, it enhances the porous structure and specific surface area of the resultant SNCs significantly. This work provides a viable strategy to promote the doping of sulfur into carbon materials during the pyrolysis process.

Full text of DOI:10.1002/asia.201900086

CHEMISTRY
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Accepted Article
Title: Controllable sulfur, nitrogen co-doped porous carbon for
ethylbenzene oxidation: the role of nano-CaCO₃
Authors: Yutian Qin, Haotian Guo, Bowei Wang, Jiayi Li, Ruixiao Gao,
Pengzhi Qiu, Mingming Sun, and Ligong Chen
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Controllable sulfur, nitrogen co-doped porous carbon for
ethylbenzene oxidation: the role of nano-CaCO
3
Yutian Qin,#[a] Haotian Guo,#[a] Bowei Wang,*[a,b,c] Jiayi Li, Ruixiao Gao, Pengzhi Qiu, Mingming
[a]
[a]
[a]
[a]
[a,b,c]
Sun, and Ligong Chen*
Abstract: Heteroatom doped porous carbon materials have
exhibited promising applications in various fields. In this work, sulfur,
nitrogen co-doped carbon materials (SNCs) with abundant pore
structure were prepared by pyrolysis of sulfur, nitrogen-containing
these materials with enhanced specific surface area and active
sites, hence, promoting their efficiency in catalysis.[6]
Pyrolysis of S-containing precursors under thermal conditions is
a practical strategy to produce S-doped carbon materials.
Various sulfur sources, like thiourea, elemental sulfur,[8] and
potassium thiocyanate,[9] as well as resins assembled with S-rich
monomers,[10] have been employed to the synthesis of S-doped
carbon materials. Generally, these S-containing components
decompose and release volatile sulfur species (e.g. hydrogen
sulfide, sulfur dioxide and elemental sulfur) during pyrolysis, and
the generated volatile molecules then interact with carbon at
high temperature to form C-S bond, thus realizing the doping of
sulfur.[11] Nonetheless, only a small fraction of sulfur from
precursors could be incorporated to the resultant materials. On
the one hand, the low atom utilization ratio of sulfur leads to
unnecessary waste; on the other hand, it may cause severe
atmospheric contamination.[12] Additionally, the formation of C-S
bond usually needs high temperature, however, such high
temperature may lead to the removal of nitrogen.[5,13] Thus, it is
particularly important to promote the exploitation of sulfur in the
preparation of S, N co-doped materials, making it feasible to
achieve a reasonable doping level of sulfur at a relative low
temperature, hence, keeping the deprivation of nitrogen within
an acceptable degree.
[7]
3
porous organic polymers (POPs) mixed with nano-CaCO at high
temperature. Among the resultant materials, SNC-Ca-850
possesses a relatively high level of doped heteroatoms and exhibits
an excellent catalytic performance for the selective oxidation of
3
benzylic C-H bonds. It is noteworthy that nano-CaCO elevates the
doped sulfur content in the synthesized carbon materials to a large
extent, and has impact on the existence modes of sulfur. Besides, it
enhances the porous structure and specific surface area of resultant
SNCs significantly. This work provides a viable strategy to promote
the doping of sulfur into carbon materials during pyrolysis process.
Introduction
Owing to the large surface area, abundant pore structure, rich
functional sites, as well as excellent thermal and chemical
stability, hetero-doped mesoporous carbon materials exhibit
promising value as gas adsorbents, supercapacitors and
catalysts.[ Among the common hetero elements, N-doped
carbons have received extensive study since nitrogen atom has
a similar radius with carbon and is easy to be embedded into
graphitic lattice. As prior studies reported, the doping of nitrogen
is conducive to modifying the electrochemical properties of
carbon materials, thus improving their capability in catalysis.[2]
Recent studies showed the performance of N-doped carbons
could be further elevated with secondary doping elements (e.g.
boron,[3] sulfur,[4] or phosphorus ). For example, the doping of
sulfur presents a marked impact on the distribution of charge
density and spin density of local carbon atoms, which are highly
related to the catalytic activity. Apart from the electronic nature,
sulfur atoms are apt to protrude out from the plane of adjacent
1]
Overall, further research is still in demand on developing a
convenient and effective strategy to promote sulfur utilization
during pyrolysis. Apart from compounds giving off volatile sulfur
at high temperature, thermostable S-containing substitutes, like
metal sulfide and sulfate, are also competent as sulfur sources,
which provide the opportunity to suppress the loss of volatile
sulfur components during pyrolysis.[13a, 14] Limestone, of which
[5]
the major component is CaCO
3
, has been extensively applied in
gas desulfurization.[15] As it is capable of capturing acidic sulfur
species (H S, SO ) to form corresponding sulfide and sulfate
CaS, CaSO ), the in situ generated S-containing salts are
expected to react with carbon materials at high temperature to
achieve the doping of sulfur. Furthermore, nano-CaCO has
2
2
(
4
2
sp carbon and induce more defects into the skeleton, endowing
3
been employed in preparing mesoporous materials to promote
their surface area and pore volume, which are salutary for the
performance in catalysis.[ Compared with other conventional
templates, like mesoporous zeolites and nano-silica,[17] whose
removal require harsh conditions (i.e. toxic hydrofluoric acid or
Y. Qin,# H. Guo,# Dr. B. Wang, J. Li, R. Gao, P. Qiu, M. Sun, Prof. L.
Chen
School of Chemical Engineering and Technology
Tianjin University
Tianjin 300350 (P. R. China)
E-mail: bwwang@tju.edu.cn
[
a]
16]
heated sodium hydroxide solution), nano-CaCO
3
,
or its
decomposition product CaO, are liable to be etched with diluted
acid, thus making it a feasible accessory ingredient to enhance
the porous structure of resultant materials. In our previous work,
S, N-containing porous organic polymers (POPs) were prepared
lgchen@tju.edu.cn
Dr. B. Wang, Prof. L. Chen
Collaborative Innovation Center of Chemical Science and
Engineering (Tianjin)
Tianjin 300072 (P.R. China)
Dr. B. Wang, Prof. L. Chen
Tianjin Engineering Research Center of Functional Fine Chemicals
Tianjin 300072 (P.R. China)
[
b]
c]
via
condensation
polymerization
of
melamine
and
[
[
18]
terephthalaldehyde in dimethyl sulfoxide (DMSO). During the
condensation process, some decomposition products of DMSO
[
#] These authors contributed equally to this work.
(
e.g. dimethyl sulfide) interact with POPs to achieve the
[19]
Supporting information for this article is given via a link at the end of
the document.
introduction of sulfur. Since sulfur atoms in POPs are bonded
to carbon skeleton directly, they are able to in situ dope into
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Chemistry - An Asian Journal
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FULL PAPER
carbon composites at high temperature with less involvement of
volatile sulfur intermediates. Herein, S, N co-doped porous
carbons (SNCs) were prepared by pyrolyzing the mixture of
POPs and nano-CaCO . The synthesized materials exhibited
3
superb catalytic performance for the selective oxidation of
benzylic C-H bonds.
The doping content and existence state of sulfur and nitrogen
were examined by X-ray photoelectron spectroscopy (XPS) and
elemental analysis (EA) (Table 2, S1). As XPS global spectrum
presents, the peaks of C 1s, O 1s, N 1s and S 2p are detected,
demonstrating the successful doping of nitrogen and sulfur into
carbon materials (Figure S3). Four types of nitrogen, pyridinic N
(
397.8 eV), pyrrolic N (399.0 eV), graphitic N (400.6 eV) and N-
O (402.3 eV) are observed in N 1s high resolution spectra
Figure 2, S4-S11).[22] With carbonizing temperature elevating,
(
Results and Discussion
the content of doped nitrogen decreases considerably. As for
graphitic N, which is reported to conduce to the catalytic
capability for oxidation reactions via radical mechanism,[ its
relative fraction (compared with total nitrogen) increases with
process temperature rising.
The morphology and structure of SNCs were characterized by
scanning electron microscopy (SEM), transmission electron
microscopy (TEM) and nitrogen adsorption-desorption
measurements. According to the microscope images, SNC-850
presents irregular non-porous particles (Figure S1), while SNC-
Ca-850 and SNC-Si-850 possess unconsolidated structures with
abundant meso- and macropores (Figure 1). The approximate
pore size in SNC-Si-850 is smaller than SNC-Ca-850, which is
consistent with the dimensions of applied SiO
nanoparticles. In order to further explore the effects of nano-
templates on porosity, nitrogen adsorption-desorption
measurements were performed (Figure S2) and the specific
surface areas of SNCs were obtained by Brunauer-Emmertt-
Teller (BET) method (Table 1). Both SNC-Ca-850 and SNC-Si-
23]
Table 1. Porous properties of SNC materials.
2
3
Sample
Surface area (m /g)
Pore volume (cm /g)
2 3
and CaCO
SNC-Ca-850
SNC-Si-850
SNC-850
704
942
257
402
472
639
783
0.88
1.09
0.27
0.58
0.61
0.83
0.94
850 exhibit representative Type IV isotherms with H3 hysteresis
SNC-Ca-650
SNC-Ca-750
SNC-Ca-950
NC-Ca-850
loops, corresponding to the presence of meso- and
macropores.[20] Compared with SNC-850, the specific surface
area and pore volume are enhanced greatly by the employment
of nano-CaCO
50 is slightly smaller than that of SNC-Si-850, which is probably
attributed to the coarser particle size of nano-CaCO
3 2
or SiO . The specific surface area of SNC-Ca-
8
3
.
Furthermore, among the materials pyrolyzed at different
temperature, SNC-Ca-850 and SNC-Ca-950 possess relatively
large surface area. The CO released by CaCO decomposition
2 3
may activate carbon material at higher temperature, thus leading
to more abundant porous structure.[21]
In the case of sulfur, it is remarkable that the total doped content
in SNC-Ca-850 (2.7 wt% by XPS) is more than 3 times of that in
SNC-Si-850 (0.8 wt% by XPS) and SNC-850 (0.6 wt% by XPS).
Besides, there are three peaks observed in the high resolution S
2p spectra (Figure 2, S4-S8). The dual peaks at 163.2 and 164.4
eV are attributed to 2p1/2 and 2p3/2 orbits of aromatic S (typically
thiophenic S and aryl S), while the broad peak ranging from
1
66.0 eV to 169.5 eV indicates the presence of oxidized S.[24]
Compared with SNC-Si-850 and SNC-850, SNC-Ca-850
possesses a higher ratio of aromatic S species. These results
illustrate that nano-CaCO
doping level of sulfur, especially aromatic S. It has been
proposed that CO , generated from thermal decomposition of
CaCO , may react with carbon at high temperature, thus
3
, to a great extent, enhances the
2
3
reducing the content of carbon and increasing the relative
percentage of sulfur.[25] As SNC-Ca-850 was obtained with a
moderate yield (0.24 g derived from 1.00 g POPs), just a bit
lower than SNC-Si-850 (0.29 g derived from 1.00 g POPs) and
SNC-850 (0.30 g derived from 1.00 g POPs), the reaction
between carbon and CO
the enhancement of sulfur content. In this case, it is intriguing
how CaCO benefits the doping of sulfur into carbon structure.
Generally, organic sulfur may exist in four types: aliphatic S
2
may be not the predominant cause for
3
Figure 1. SEM images of (a) SNC-Ca-850, (b) SNC-Si-850 and TEM images
of (c) SNC-Ca-850, (d) SNC-Si-850.
(
(
mercaptan, thioether, and disulfide), thiophenic S, aryl S
thiophenol and diaryl sulfide) and oxidized S (sulfone and
sulfoxide).[ Among these types, aliphatic and oxidized S are
26]
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less stable under heat treatment. Aliphatic S may undergo two
competitive transformations, either transforming to more stable
Table 2. Composition of nitrogen and sulfur of SNC materials.
Composition (wt%)
aromatic S (thiophenic and aryl S) or degrading to H
Otherwise, oxidized S is liable to decompose and escape as
SO , is
.[27] Since CaO derived from the decomposition of CaCO
of strong Brønsted basicity, it may prevent the efflux of H S and
SO via following reactions:
2
S.
Sample
2
3
N by XPS
17.1
14.1
9.7
N by EA
S by XPS
1.3
S by EA
0.8
1.1
1.6
1.3
0.6
0.5
-
2
2
SNC-Ca-650
SNC-Ca-750
SNC-Ca-850
SNC-Ca-950
SNC-Si-850
SNC-850
12.6
9.0
6.2
1.6
6.8
6.0
6.4
6.1
5.3
1.6
2.7
1.9
2.4
Because CaSO
3
is of poor thermal stability, the products of
are CaS and CaSO instead of
The in situ formed sulfide and sulfate may react
reaction between CaO and SO
CaSO .
3
2
4
10.7
9.8
0.8
[
28]
smoothly with the carbon materials, thereby elevating the
0.6
content of doped sulfur.[13a,29] According to the X-ray diffraction
NC-Ca-850
SNC-Ca-850c
SNC-Ca-850
10.3
9.3
-
(
(
XRD) pattern of as-pyrolyzed material before acid etching
Figure S12), the presence of CaS is confirmed.[ However, no
30]
1.8
1.0
1.3
peaks attributed to CaSO
4
is found, which is probably due to its
complete reaction with carbon or other reductive components
8.4
2.5
(
e.g. carbon monoxide and hydrogen) generated during
(recycled)
[29b]
pyrolysis.
Besides, the surface sulfur content (determined by
XPS) is higher than that in bulk (determined by EA), which
implies the promoted sulfur doping by the interaction between
Figure 3a shows the XRD patterns of SNC materials. Two broad
mainly occurs at the interfaces.[
24a]
carbon and CaS/CaSO
4
o
o
peaks at 2θ = 24 and 43 are assigned to the (002) and (100)
Moreover, in such a process, a portion of sulfur in oxidized state
+4) is transformed into lower valence state (-2 in sulfide), which
lattice planes of carbon, respectively.[ It is conspicuous that
32]
(
o
the peak near 24 is asymmetric, which could be deemed to be
may be contributive to the larger proportion of aromatic S in
SNC-Ca-850. The sulfur content rises as pyrolysis temperature
the combination of disordered (22ο) and graphitic carbon
o
o
ο [21]
elevates from 650 C to 850 C, indicating the doping of sulfur
via carbon-CaS/CaSO solid reaction is relatively hard to
(26.5 ).
Compared with SNC-Si-850 and SNC-850, the
4
diffraction angle corresponding to maximum intensity of SNC-
proceed and requires high temperature. Whereas, a slight
decrease of sulfur content occurs when the pyrolysis
o
Ca-850 is closer to 22 , indicating it possesses a lower degree of
graphitization. Besides, Raman spectra were depicted in order
to further probe the defective nature of materials (Figure 3b).
The bands at 1352 and 1533 cm-1 are ascribed to disordered
carbon (D band) and graphitic carbon (G band), respectively.[
The intensity ratio between D band and G band of SNC-Ca-850
o
temperature further increases to 950 C, which may be attributed
o
to the loss of aryl S, as it is unstable over 900 C and tends to
[
31]
decompose to H
pyrolysis temperature, the ratio of aromatic S elevates from
9.3 (SNC-Ca-650) to 91.5 (SNC-Ca-950), which
2
S and CS
2
.
Furthermore, with an increasing
33]
6
%
%
corresponds to the higher thermal stability of aromatic S
compared with oxidized S.[27,31] In addition, no distinct diffraction
peaks assigning to inorganic sulfide or sulfate are observed in
the S 2p spectra, indicating the residual calcium species are
minuscule. Inductively coupled plasma optical emission
spectrometry (ICP-OES) test was performed to further determine
the residue of calcium. The content of remnant calcium in SNC-
Ca-850 is only 0.12 wt%, confirming a nearly complete removal
of calcium species via acid etching.
(
1
I
D
/I
.02) and SNC-850 (I
defective structure, which is consistent with the results of XRD. It
has been proposed that the existence of nano-CaCO may be
G
= 1.09) is slightly larger than that of SNC-Si-850 (I
D G
/I =
D G
/I = 1.01), revealing SNC-Ca-850 a more
3
liable to create edge sites and crystal boundaries, thus
preventing the formation of highly-ordered carbon.[21] Besides,
the more disordered structure in SNC-Ca-850 is also probably
related to its higher content of doped sulfur. Since the size of
sulfur atom is much bigger than carbon, it tends to form a bulge
at the layer of local sp2 carbon, thus breaking the regular
graphitic structure and generating defects.[
34]
Figure 2. High resolution (a) N 1s and (b) S 2p XPS spectra of SNC-Ca-850.
Figure 3. (a) XRD patterns and (b) Raman spectra of SNC materials.
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Selective oxidation of aromatic alkanes with benzylic C-H bonds
is one primary approach to producing corresponding ketones.[33b]
Generally, this reaction can be accelerated by catalysts based
on transition metal (e.g. cobalt,[35] iron,[36] manganese,[37] and
nickel[38]). Nevertheless, these catalysts are at risk of metal
leaching, which limits their application in food and
pharmaceutical industries. The development of metal-free
catalysts, typically based on carbon, makes it possible to avoid
this problem from the origin. Herein, SNC materials were applied
as heterogeneous catalysts for the selective oxidation of C-H
bonds. Using tert-butyl hydrogen peroxide (TBHP) as oxidant,
ethylbenzene was transformed to acetophenone with
Compared with SNC-850, the considerably high catalytic
capabilities of SNC-Ca-850 and SNC-Si-850 may be due to their
larger surface area and higher pore volume, which are
preferable to the mass transfer of reactants and products.
According to prior studies, the presence of graphitic N is
conducive to enhance the catalytic activity.[23,39] Although both
surface area and graphitic N content of SNC-Ca-850 are slightly
lower than that of SNC-Si-850, the former material shows better
catalytic performance, which is probably related to its higher
content of sulfur. In addition, the S, N co-doped carbon material
exhibits higher effect than the N single doped one (Table 3,
entry 10). Because of the mismatch of outermost orbitals of
carbon and sulfur atoms, the sulfur atom possesses a higher
density of positive charge, thus being feasible to adsorb reactive
benzaldehyde
and
1-phenylethanol
as
byproducts.
Ethylbenzene was barely converted without catalyst or simply
adding activated carbon (AC) to the reaction system (Table 3,
entry 1-2). An excellent catalytic capacity was presented by
SNC-Ca-850. Under the optimized reaction conditions, high
ethylbenzene conversion (92.4 %) and acetophenone selectivity
oxygen species (ROS).[24b,40] Furthermore, there exists
a
synergetic effect between co-doped sulfur and nitrogen, which
endows the adjacent carbon atoms with elevated spin density,
hence further promoting the capability of adsorbing ROS.[40b] The
relatively high sulfur content provides SNC-Ca-850 with
enhanced ability to enrich ROS. Besides, the hydrophobic
surface of SNC-Ca-850 renders it affinitive to low-polarity
substrates (i.e. aromatic alkanes). The condensed ROS and
substrates near the surface of catalyst, thereby, accelerate
oxidation reactions effectively. In this case, the superior catalytic
performance of SNC-Ca-850 could be attributed to its higher
content of doped hetero elements, especially sulfur. Moreover,
(
97.4 %) were achieved in 4 h (Table 3, entry 3). Otherwise,
moderate conversion and selectivity were acquired over SNC-Si-
50, while only a modicum of acetophenone was afforded over
8
SNC-850 (Table 3, entry 4-5). Besides, SNC-Ca-850 exhibited
the best catalytic performance among all SNC-Ca materials
pyrolyzed at different temperatures (Table 3, entry 6-8).
Furthermore, SNC-Ca-850 showed good reusability since a
satisfactory activity was retained after 4 cycles (Table 3, entry 9;
Figure S14).
o
after being calcinated at 250 C under aerobic conditions (SNC-
Ca-850c), the content of aromatic S decreases from 2.3 wt% to
1.0 wt%, while oxidized S increases from 0.4 wt% to 0.8 wt%.
Table 3. Catalytic evaluation for ethylbenzene oxidation.[a]
The calcinated material shows relatively poor catalytic
performance (Table 3, entry 11). Similar change of sulfur
existing modes and catalytic effect are observed in the recycled
catalyst (Table 3, entry 10), implying aromatic S may be the
contributive species to the selective oxidation of benzyl C-H.
Entry
Catalyst
Conv. (%)
Sel. (%)
Table 4. Selective oxidation of substituted aromatic alkanes.[a]
1
2
Blank
6.7
51.8
60.5
97.4
92.5
68.0
59.2
80.2
75.1
87.9
94.0
92.3
AC
24.5
92.4
86.3
31.6
51.3
73.9
60.4
80.1
75.2
72.8
Entry
1
Substrate
Conv. (%)
99.4
Sel. (%)
97.1
3
SNC-Ca-850
SNC-Si-850
SNC-850
4
2
3
4
93.0
85.3
89.5
96.7
87.7
79.0
5
6
SNC-Ca-650
SNC-Ca-750
SNC-Ca-950
SNC-Ca-850
NC-Ca-850
SNC-Ca-850c
7
8
5
6
91.5
97.4
89.2
98.7
9 [b]
1
0
1
[
a] Reaction conditions: SNC-Ca-850 (10 mg), substrate (0.5 mmol),
1
o
TBHP (2 mmol, 70 wt% solution in water), water (2 mL), 80 C, 6 h.
[
a] Reaction conditions: catalyst (10 mg), ethylbenzene (0.5 mmol),
o
TBHP (2 mmol, 70 wt% solution in water), water (2 mL), 80 C, 4 h. [b]
reused for 4 times.
In addition, a number of substrates were tested under the
modified conditions with SNC-Ca-850. Aromatic ketones with
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strong electron donating (methoxyl) or withdrawing (nitro) groups
were afforded with satisfactory yields (Table 4, entry 2-3).
Besides, alkyl and halide substituted substrates were converted
with high efficiency (Table 4, entry 4-5). Furthermore, the
catalytic system was also effective to the substrate with bulky
group (Table 4, entry 6).
(average particle size 20 nm) as template, which was removed
by hydrofluoric acid (3 mol/L) in the following etching procedure.
SNC-t was prepared by direct pyrolysis of POPs with no
additional ingredients. SNC-Ca-850c was obtained by
calcinating as-prepared SNC-Ca-850 under air atmosphere at
250 oC for 30 min. Besides, sulfur-free nitrogen-doped porous
carbon (NC-Ca-t) was prepared by employing SFPOPs in place
of POPs as precursor.
Catalytic tests: The selective oxidation of aromatic alkanes with
TBHP was adopted as a model reaction to evaluate the catalytic
performance of synthesized SNCs. In a typical procedure,
substrate (0.5 mmol), TBHP (2 mmol) and water (2 mL) were
introduced into a 15 mL sealed tube containing catalyst (10 mg).
The mixture was placed in an 80 oC oil bath with magnetic
stirring and kept for 4 h. After reaction, 10 mL ethanol was
added and the suspension was stirred for a while to ensure the
system homogeneous. Finally, the mixture was analyzed by
EWAI GC-4000A gas chromatograph with a PEG-20M column.
Conclusions
In summary, S, N co-doped porous carbon materials were
developed by pyrolyzing the homogeneous mixture of S, N-
containing polymers and nano-CaCO
3
under inert atmosphere.
The adscititious nano-CaCO not only enhances the formation of
3
porous structure, but also has a remarkably enhancive impact
on the content of doped sulfur. The modified porosity and doping
effect endow the materials with superior catalytic performance
for the selective oxidation of aryl alkanes with TBHP as oxidant.
Hence, this strategy is feasible to improve the utilization of sulfur
in pyrolysis process, thus promoting the sulfur doping content of
carbon materials.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (Grant No. 21808161 and No. 21576194).
Experimental Section
Characterization: XRD patterns were measured with Bruker D8
Focus equipped with a Cu Kα X-ray source. Raman spectra
were recorded by Thermo Scientific DXR Microscope. ICP-OES
measurements were performed on Varian VISTA-MPX. SEM
images were obtained using Hitachi S-4800 microscope. TEM
images were obtained using JEOL JEM-2100F field emission
electron microscope. Nitrogen sorption isotherms were obtained
using Quantachrome Autosorb iQ analyzer at 77 K. EA were
performed on Vario EL Cube. XPS measurements were carried
out with Thermo Fisher Scientific X-ray ESCALAB 250Xi.
Keywords: Carbon • Doping • Heterogeneous catalysis •
Mesoporous materials
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Entry for the Table of Contents
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#
#
Sulfur, nitrogen co-doped porous
carbon materials were synthesized by
pyrolyzing porous organic polymers
Yutian Qin, Haotian Guo, Bowei
Wang,* Jiayi Li, Ruixiao Gao, Pengzhi
Qiu, Mingming Sun, and Ligong Chen*
mixed
with
nano-CaCO
3
.
The
employment of nano-CaCO
3
not only
Page No. – Page No.
enhances the forming of porous
structure, but also promotes the
doping of sulfur into carbon skeleton.
Controllable sulfur, nitrogen co-
doped porous carbon for
ethylbenzene oxidation: the role of
The
resultant
materials
exhibit
nano-CaCO
3
excellent catalytic performance for the
selective oxidation of benzylic C-H
bonds.
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