Template-free synthesis of porous carbonaceous solid acids with controllable acid sites and their excellent activity for catalyzing the synthesis of biofuels and fine chemicals

Article abstract of DOI:10.1039/c5cy01226k

N rich porous carbon based solid acids (NPC-[C_xN][X]) have been successfully synthesized by treatment of N rich porous carbon (NPC) with various quaternary ammoniation reagents such as iodomethane, 1,3-propane sultone, and 1,4-butanesultone, and ion exchange with various strong acids such as HSO₃CF₃, H₂SO₄, H₃PW₁₂O₄₀, HBF₄etc. The NPC support was synthesized by carbonization of KOH-activated polypyrrole without using additional templates. Various characterizations showed that NPC-[C_xN][X] possesses abundant nanopores, large Brunauer-Emmett-Teller surface areas, good stability, and strong and controllable acid sites with Br?nsted characteristics. The immobilized acidic groups were homogeneously dispersed into NPC-[C_xN][X]. Notably, NPC-[C_xN][X] acted as efficient, reusable and generalized solid acids, which showed excellent activity in various acid-catalyzed reactions such as esterification and transesterification in the synthesis of biodiesel, dehydration of fructose into 5-hydroxymethylfurfural, depolymerization of crystalline cellulose into sugars, and condensation of phenol with acetone in the synthesis of bisphenol A, much higher than that of various solid acids such as Amberlyst 15, H-ZSM-5, H-USY, and sulfonic group functionalized ordered mesoporous silicas. The preparation of NPC-[C_xN][X] leads to the development of porous carbon based solid acids with controllable structural characteristics and excellent catalytic activity.

Full text of DOI:10.1039/c5cy01226k

View Article Online
View Journal
Catalysis
Sc ience &
Technology
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: L. Fujian, B. Li, C.
Liu, K. Weiping, X. Yi, A. Zheng and C. Qi, Catal. Sci. Technol., 2015, DOI: 10.1039/C5CY01226K.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/catalysis

Page 1 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
Template-free synthesis of porous carbonaceous solid acids with controllable acid
sites and excellent activity for catalyzing synthesis of biofules and fine chemicals
a
b
a
a
c
c
Fujian Liu* , Bojie Li , Chen Liu , Weiping Kong , Xianfeng Yi , Anmin Zheng* ,
a
Chenze Qi*
a
Department of Chemistry, Shaoxing University, Shaoxing, 312000, China. E-mail
address: fjliu1982@gmail.com, qichenze@usx.edu.cn
b
College of Chemistry and Materials Science, Hubei Engineering University, Xiaogan
4
32000, China.
c
Wuhan Center for Magnetic Resonance, State Key Laboratory of Magnetic
Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and
Mathematics, Chinese Academy of Sciences, Wuhan 430071, China. Email address:
zhenganm@wipm.ac.cn
1

Catalysis Science & Technology
Page 2 of 48
View Article Online
DOI: 10.1039/C5CY01226K
Abstract
x
N rich porous carbon based solid acids (NPCꢀ[C N][X]) have been successfully
synthesized from treating N rich porous carbon (NPC) with various quaternary
ammonization reagents such as iodomethane, 1,3ꢀpropane sultone, and
1
,4ꢀbutanesultone, and ion exchanging with various strong acids such as HSO
3 3
CF ,
H
2
SO , H 40 and HBF etc. The NPC support was synthesized from
4
3
PW12
O
4
carbonization of polypyrrole activated with KOH without using additional templates.
Various characterizations showed that NPCꢀ[C N][X] possess abundant nanopores,
x
large BrunauerꢀEmmettꢀTeller surface areas, good stability, strong and
controllable acid sites with Brønsted characteristics. The immobilized acidic groups
x x
were homogeneously dispersed into NPCꢀ[C N][X]. Notably, NPCꢀ[C N][X] acted as
efficient, reusable and generalized solid acids, which showed excellent activity in
various acidꢀcatalyzed reactions such as esterification and transesterification to the
synthesis of biodiesel, dehydration of fructose into 5ꢀhydroxymethylfurfural,
depolymerization of crystalline cellulose into sugars, and condensation of phenol with
acetone to the synthesis of bisphenolꢀA, much higher than various solid acids such as
Amberlyst 15, HꢀZSMꢀ5, HꢀUSY, and sulfonic groups functionalized ordered
mesoporous silicas. The preparation of NPCꢀ[C N][X] develops porous carbon based
x
solid acids with controllable structural characteristics and excellent catalytic activity.
Key words: N rich porous carbon; Solid acids; Biomass transformation; Reusability;
Controllable acid sites.
2

Page 3 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
1
. Introduction
Recently, carbonaceous materials with unique nanostructures have received
considerable attention because of their wide applications in the areas of adsorption,
separation, electrochemistry, energy storage/conversion and heterogeneous catalysis
1
-13
.
In the area of heterogeneous catalysis, carbonaceous materials could be used as
1-13
efficient and stable catalysts and catalyst supports
. Up to now, much more
research efforts have been focused on investigating the catalytic applications of
carbonꢀmetal nanocomposites or metalꢀfree carbonaceous catalysts in various
1
2-20
reactions such as oxidation, hydrogenation and electrocatalysis
. On the other
hand, functionalization of carbonaceous materials with acidic groups to give
carbonaceous solid acids have also been paid much attention because of wide
applications of the solid acids in the area of green and sustainable chemistry, which
are the property candidates for the replacement of mineral acids to catalyze
2
1-27
production of various useful chemicals in industry
.
Generally, the solid acids showed versatile compositions such as polymeric,
inorganic and carbonaceous frameworks, carbonaceous material was suitable supports
for grafting with various acidic groups because of their unique thermal, mechanical
and chemical stabilities, and controllable surface wettability, which offers great
2
1
opportunity for synthesizing highly efficient and reusable solid acids in industry .
Recently, Hara and coworkers successfully synthesized novel carbonaceous solid
acids from sulfonation of the carbons derived from biomass such as glucose, sucrose
3

Catalysis Science & Technology
Page 4 of 48
View Article Online
DOI: 10.1039/C5CY01226K
and cellulose, which developed cost effective way to the synthesis of carbonaceous
28, 29
solid acids
. Nearly the same time, they successively synthesized carbonaceous
solid acids with improved concentrations of acid sites from sulfonation of naphthalene
30
at high temperature (250 °C) . The resultant carbonaceous solid acids showed very
good catalytic activity in esterification and condensation. However, the reported
carbonaceous solid acids usually showed poor porosity, which results in the low
exposure degree of catalytically active sites, further resulting in their constrained
2
1
catalytic performances .
Introduction of abundant nanopores to give porous carbon based solid acids
largely enhance the mass transfer and increase exposure degree of nonporous carbon
based solid acids, which largely increases their catalytic performances in various
reactions such as esterifications, condensation, transesterification, isomerization and
22-26, 31, 32
acylation etc
. Nevertheless, the synthesis of porous carbon based solid acids
usually employs various kinds of templates, and the reported templateꢀdirected
synthesis was usually complicated, time consuming and high cost, which largely
23, 24
constrains their widely practical applications in industry
. In the meantime, the
structures of acidic sites in reported carbonaceous solid acids were basically
2
5, 26, 28-30
C–COOH and C–SO
3
H
, and their constrained acid strength was not
favorable for the enhancement of their catalytic activities in various acidꢀcatalyzed
reactions such as biomass transformation, esterifications and condensation.
Up to now, it is still challengeable to synthesize porous carbon based solid strong
acids with controllable structures and acid sites, which will be very important for
4

Page 5 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
improving their catalytic performances. Herein, we report here a template free
method to synthesize novel porous carbon based solid acids (NPCꢀ[C N][X]) with
x
controllable and strong acid sites, which were synthesized from treating N rich
porous carbon (NPC) with various quaternary ammonization reagents such as
iodomethane, 1,3ꢀpropane sultone, and 1,4ꢀbutanesultone, and ion exchanging with
strong acids such as HSO
was synthesized from carbonization of polypyrrole activated with KOH without
using additional templates. The resultant carbonaceous solid acids of NPCꢀ[C N][X]
3 3 2 4 3 4
CF , H SO , H PW12O40, and HBF . The NPC support
x
have large BrunauerꢀEmmettꢀTeller (BET) surface areas, good thermal stability,
controllable and strong acidity, and good dispersion of acid sites. The above
x
characteristics result in NPCꢀ[C N][X] with excellent activity and good reusability
for catalyzing production of biofuels and fine chemicals toward transesterification
and esterification to synthesis of biodiesel, depolymerization of crystalline cellulose
into sugars, dehydration of fructose into 5ꢀhydroxymethylfurfural (HMF), and
condensation to the synthesis of bisphenol A, which were much better than those of
reported solid acids such as Amberlyst 15, sulfonic group functionalized ordered
3 x
mesoporous silicas, Hꢀzeolites and H O40PW12. The preparation of NPCꢀ[C N][X]
will open a facile and cost effective way to the synthesis efficient and highly porous
carbon based solid acids with controllable and strong acid sites, and good catalytic
activity, which will be very important for their wide applications for catalyzing
production of various useful chemicals and biofuels in industry.
5

Catalysis Science & Technology
Page 6 of 48
View Article Online
DOI: 10.1039/C5CY01226K
2
. Experimental section
2
.1 Chemicals and reagents
All reagents were of analytical grade and used as purchased without further
purification. Iodomethane, 1,3ꢀpropane sultone, and 1,4ꢀbutanesultone, HSO CF
, toluene, glucose, tetraethyl orthosilicate (TEOS), NaOH, pyrrole,
O, potassium sodium tartrate, sodium sulfite, methanol, 3,5ꢀdinitrosalicylic
40, phenol, KOH and acetone were obtained from Sinopharm Chemical
3
3
,
H
2
SO
4
2 2
, CH Cl
FeCl
3
·6H
2
3
acid, H PW12O
Reagent, Beijing Co., Ltd. Crystalline cellulose of Avicel (extra pure, average particle
size 50 ꢁm, crystalline degree: 80~90 %), 3ꢀmercaptopropyltrimethoxysilane
(3ꢀMPTS),
nonionic
block
copolymer
surfactant
poly(ethyleneoxide)ꢀpoly(propyleneoxide)ꢀpoly(ethyleneoxide) block copolymer
(P123), Amberlyst 15, tripalmitin, 1ꢀnꢀbutylꢀ3ꢀmethylimidazolium chloride
(
[C mim]Cl ionic liquid), palmitic acid, fructose, 1ꢀvinylimidazole, tripalmitin
4
and HMF were purchased from SigmaꢀAldrich Co.
2
.2 Synthesis of NPC
NPC was synthesized from carbonization of polypyrrole (PPy) in presence of
KOH activated reagent, and PPy precursor was synthesized from polymerization of
pyrrole initiated with FeCl in aqueous media. Typically, 3 g of pyrrole (purified) was
slowly added into a solution containing 0.5 mol of FeCl and 200 mL of water, after
3
3
magnetically stirring of the mixture for 3 h at room temperature, abundant black
6

Page 7 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
precipitate was formed at the bottom of glassware. The PPy could be obtained from
filtration, washing with abundant water to remove all the FeCl initiator, and drying at
0 °C under vacuum conditions. The final yield of polypyrrole was nearly to 100 %.
To get N rich porous carbon, the resultant PPy and KOH with different weight ratios
0.25~1) was mixed together, and carbonization at 600ꢀ850 °C. Typically, 1.0 g of PPy
was well mixed with 2.0 g of anhydrous KOH, then the mixture was carbonized at
3
8
(
ꢀ1
8
2
00 °C for 1 h under flowing N conditions with the heating rate of 3 °C·min . Finally,
the chemically activated samples were thoroughly washed several times with HCl (10
wt%) to remove any inorganic salts, washing with abundant water until neutral, and
drying at 120 °C under vacuum conditions, NPC samples with abundant nanopores
were obtained.
2
.3 Synthesis of carbonaceous solid acids of NPC-[C
3
N][X]
NPCꢀ[C N][X] were synthesized from quaternary ammonization of NPC by using
3
1
,3ꢀpropanesultone, and anion exchanging with strong acids of HSO
40, or HBF . (In the sample of NPCꢀ[C N][X], [X] stands for the treating
acid ions and C stands for quaternary ammonization reagent of 1,3ꢀpropanesultone,
which contains three carbon atoms). In addition, NPCꢀ[C N][X] and NPCꢀ[C N][X]
3 3 2 4
CF , H SO ,
H
3
PW12
O
4
3
3
1
4
could also be successfully prepared by using iodomethane and 1,4ꢀbutanesultone as
quaternary ammonization reagents respectively. As a typical run for synthesizing
3 3 3
NPCꢀ[C N][SO CF ], 1.0 g of NPC was dispersed into a mixture contains 20 mL of
toluene and 0.5 g of 1,3ꢀpropanesultone, after stirring of the reaction mixture at
7

Catalysis Science & Technology
Page 8 of 48
View Article Online
DOI: 10.1039/C5CY01226K
110 °C for 24 h under refluxing, the reaction was finished and the mixture was cooled
+
3
down to room temperature (25 °C). The resultant sample of NPCꢀ[C N] could be
obtained from centrifugation, washing with abundant CH
Cl
2 2
and drying at 60 °C
+
under vacuum conditions. To get NPCꢀ[C N][SO CF ], NPCꢀ[C N] was then
3
3
3
3
dispersed into a solution containing 25 mL of toluene and 3ꢀ5 mL HSO
stirring of the mixture for 48 h at 0 °C, NPCꢀ[C N][SO CF ] could be obtained from
centrifugation, washing with abundant CH Cl to remove the residual HSO CF , and
3 3
CF , after
3
3
3
2
2
3
3
drying at 60 °C for 12 h under vacuum conditions. The ion exchanging procedure was
repeated twice. Except for HSO CF , other strong acids such as H SO , H PW O
3
3
2
4
3
12 40
and HBF
with controllable acid sites. For comparison, SBAꢀ15ꢀSO
for ordered mesoporous silicas) was synthesized according to the literature .
4
could also be used as acidꢀexchanged reagents, which results in the samples
3
H (S/Si=0.2, “SBA” stands
3
3
2
.4 Characterization methods
Nitrogen isotherms were measured by using a Micromeritics ASAP 2020M
system. The samples were outgassed for 10 h at 150 °C before the measurements were
taken. The mesoporeꢀsize distribution was calculated using the
BarrettꢀJoynerꢀHalenda (BJH) model and microporeꢀsize distribution was calculated
using the HorvathꢀKawazoe (HK) model. FTꢀIR spectra were collected by using a
Bruker 66V FTꢀIR spectrometer. Raman spectra were measured by using a LabRam
Aramis Raman Microscope system (HoribaꢀJobin Yvon). Xꢀray powder diffraction
(XRD) of samples was recorded on a Rigaku D/max2550 PC powder diffractometer,
8

Page 9 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
using nickelꢀfiltered CuKα radiation at approximately 10°≤2θ≤80°. Transmission
electron microscopy (TEM) images were taken on a JEMꢀ2100 electron microscope
(JEOL, Japan) with an acceleration voltage of 200 kV. CHNS elemental analysis was
performed on a PerkinꢀElmer series II CHNS analyzer 2400. XPS spectra were
performed on a Thermo ESCALAB 250 with Al Kα radition at y=901 for the Xꢀray
sources. The binding energies were calibrated using the C1s peak at 284.9 eV.
Differential thermal analysis (DTA) and thermogravimetric analysis (TG) were tested
2
by a PerkinꢀElmer TGA7 under both flowing air and N conditions with the heating
rate of 10 °C/min. Scanning electron microscopy (SEM) images, energyꢀdispersive
Xꢀray spectroscopy (EDX) spectra, and elemental maps were performed on an FEI
Strata 400S DualBeam system with an acceleration voltage of 15 kV.
3
1
3 3 3
The solid P NMR spectrum over NPCꢀ[C N][SO CF ] was performed as follows:
prior to the adsorption of probe molecules, the solid acids were placed in glass tubes
and then connected to a vacuum line for dehydration. The temperature was gradually
increased at a rate of 1 °C/min, and the samples were kept at a final temperature of
ꢀ
3
3
93 K at a pressure below 10 Pa, over a period of 12 h. After the samples cooled to
ambient temperature, a sufficient amount of trimethylphosphine (TMP) was
introduced into the acidic samples, with the activated samples frozen by liquid N
2
,
followed by elimination of the physisorbed probe molecules by evacuation at room
temperature for 30 minutes. Finally, the sample tubes were flame sealed. The
preparation of trimethylphosphine oxide (TMPO) adsorbed samples was performed
3
4
according to the method proposed by our previous work . Prior to the NMR
9

Catalysis Science & Technology
Page 10 of 48
View Article Online
DOI: 10.1039/C5CY01226K
experiments, the sealed sample tubes were opened and the samples were transferred
into ZrO rotors with a KelꢀF end cap under a dry nitrogen atmosphere in a glovebox.
All the NMR experiments were performed on a Bruker Ascendꢀ500 spectrometer
2
1
31
13
at resonance frequencies of 500.57, 202.63 and 125.88 MHz for H, P and C,
respectively, with a 4 mm tripleꢀresonance MAS probe at a spinning rate of 10 kHz. A
13
π/2 pulse width of 4.7 ꢁs and a recycle delay of 15 s were used for C NMR
31
experiment. P MAS NMR spectra with high power proton decoupling were recorded
using a π/2 pulse length of 3.2 us and a recycle delay of 30 s. The chemical shift of
1
3
31
C was externally referenced to adamantane, while that of P was referenced to 1 M
aqueous H PO
3
4
.
2
2
.5 Catalytic reactions
.5.1 Transesterification
Transesterification of tripalmitin with methanol was executed as follows: 1.68 g
(2.08 mmol) of tripalmitin was melted into a flask equipped with a condenser and
magnetic stirrer at 65 °C, followed by addition of 0.20 g of catalyst upon vigorous
stirring to form a homogeneous mixture. Then, an additional 7.41 mL (187.2 mmol) of
methanol acts as both reactant and solvent was rapidly added, after further stirring of
the mixture for 14 h at 65 °C under refluxing, the reaction was finished. The catalysts
could be separated from reaction mixture from centrifugation. The molar ratio of
tripalmitin/methanol was 1/90 and the mass ratio of catalyst/tripalmitin was 0.119.
1
0

Page 11 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
2
.5.2 Esterification
Esterification of fatty acid of palmitic acid with methanol was executed as
follows: 1.282 g of palmitic acid (5 mmol) and 2.5 mL of methanol were added into a
flask equipped with a condenser and magnetic stirrer, then 0.05 g of catalyst was
quickly introduced into the mixture under vigorous stirring. The reaction was
performed at 65 °C for 5 h. At different time intervals, samples were withdrawn and
analyzed by using gas chromatography.
The product in both trasesterification and esterification was methyl palmitate with
selectivity near 100 %, which was analyzed by using gas chromatography of Agilent
7
890A equipped with a flame ionization detector (FID). The column was
HPꢀINNOWax capillary column (30 m); the initial temperature was 100 °C, ramping
rate was 20 °C/min, and the final temperature was 280 °C; the temperature of FID
detector was 300 °C. In this reaction, the concentration of methyl palmitate was
calculated through the internal standard (dodecane) method, and established the
corresponding correction factor.
2
.5.3 Catalysts regeneration
In the reaction of transesterification of tripalmitin with methanol: 1.68 g (2.08
mmol) of tripalmitin and 0.20 g of catalyst were mixed into a flask equipped with a
condenser and magnetic stirrer at 65 °C, followed by addition of 7.41 mL (187.2
mmol) of methanol, which acts as both reactant and solvent was rapidly added. After
stirring of the mixture for 14 h at 65 °C under refluxing, the catalysts could be
11

Catalysis Science & Technology
Page 12 of 48
View Article Online
DOI: 10.1039/C5CY01226K
2 2
separated by centrifugation, washing with abundant CH Cl to remove the absorbed
reactants and products and drying it at 60 °C under vacuum condition, which was
used directly for the next run.
2
.5.4 Catalyze depolymerization of crystalline cellulose
Depolymerization of crystalline cellulose (Avicel) was also chosen as the model
reaction for evaluating the activities of various solid acids. Typically, 100 mg of
crystalline cellulose of Avicel was dissolved into 2.0 g of [C mim]Cl ionic liquid at
00 °C for 3ꢀ5 h under vigorous stirring until a clear solution was obtained, followed
by addition of 20 mg of NPCꢀ[C N][SO CF ]. Then, 600 ꢁL of water (reactant) was
slowly introduced into the reaction mixture, and the reaction temperature was kept at
00 °C. At different time intervals, samples were withdrawn, weighed, quenched
4
1
3
3
3
1
immediately with cold water, and centrifuged at 13,500 rpm for 5 min to remove
catalysts and unreacted cellulose, which gives the reaction mixture. For comparison,
various acid catalysts such as Amberlyst 15, HꢀZSMꢀ5, HꢀUSY and SBAꢀ15ꢀSO
were also used for catalyzing depolymerization of Avicel under the same condition.
3
H
Meanwhile, the isolated cellulose was thoroughly washed with water, and
recovered through centrifugation. The amount of cellulose isolated could be
determined by weight.
2
.5.5 Testing Total Reducing Sugars (TRS)
TRS value was used for evaluating the depolymerization degree of crystalline
1
2

Page 13 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
22
cellulose catalyzed by various catalysts, which was tested through DNS method
.
Typically, a mixture containing of 0.1 mL of 3,5ꢀdinitrosalicylicacid (DNS) reagent
and 0.1 mL of performed reaction mixture was heated for 5 min at 100 °C, then
cooled to room temperature, followed by addition of 0.8 mL of deionized water to
dilute the mixture. The color intensity of the mixture was measured in a NanoDrop
2
000 UVꢀspectrophotometer at the wavelength of 540 nm. The concentration of the
total reducing sugars was calculated based on the standard curve method.
2
.5.6 Catalyze transformation of fructose
Catalyze transformation of fructose into HMF and furanꢀ2,5ꢀdicarbaldehyde was
performed with the following procedures: 0.1 g of fructose and 20 mg of catalyst were
added into a mixture containing 3 g of THF and 2 g of DMSO, which was heated at
1
00 °C for 10 h. The major products were HMF and furanꢀ2,5ꢀdicarbaldehyde, and
the major byꢀproducts were LA, FA and some others.
2
.5.7 Catalyze synthesis of bisphenol-A
Catalyze synthesis of bisphenolꢀA was performed through condensation of phenol
with acetone in presence of various solid acids. Typically, 70 mmol phenol and 10
mmol acetone were mixed together, followed by addition of 0.07 g of solid acid
catalysts, the reaction mixture was heated at 85 °C for 24 h in a flask equipped with a
1
3

Catalysis Science & Technology
Page 14 of 48
View Article Online
DOI: 10.1039/C5CY01226K
condenser and magnetic stirrer. The main products were p,p'ꢀbisphenolꢀA and
o,pꢀbisphenolꢀA.
2
.5.8 Analysis of products
In the reaction of depolymerization of crystalline cellulose, the concentrations of
the sugars were measured by Shimadzu LCꢀ20A highꢀperformance liquid
chromatography (HPLC) system equipped with a refractive index detector based on
standard curve method, which was separated with a SCRꢀ101N column using
extraꢀpure water during mobile phase at a flow rate of 0.5 mL/min. The column’s
temperature was set to 50 °C. On the other hand, the yields of p,p'ꢀbisphenolꢀA and
o,pꢀbisphenolꢀA, HMF, furanꢀ2,5ꢀdicarbaldehyde and other byproducts were also
measured by Shimadzu LCꢀ20A HPLC system based on standard curve method. It
was equipped with a CAPCELL PAK C18 column using methanol and water
(methanol/water=80:20) as the mobile phase, with a flow rate of 0.7 mL/min and the
column’s temperature was set to 50 °C. In the meantime, an ultraviolet detector with
the wavelength number at 249 and 254 nm was used to detect these products.
3
. Results and discussion
3 3 3
Figure 1 showed XRD patterns of NPC, NPCꢀ[C N][SO CF ]. For the sample of
NPC, two broad peaks at around 2θ=24.9 and 43.3 ° could be observed, which
1
4

Page 15 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
35
indicates its amorphous characteristics . After functionalization of NPC with
strongly acidic groups, giving the sample of NPCꢀ[C N][SO CF ], which exhibited
3
3
3
similar peaks at around 2θ=24.9 and 43.3 ° with decreased diffraction intensity in
comparison with that of NPC. Consideration of the amorphous network of both NPC
and NPCꢀ[C
attributed to the grafting of strong acidic groups, which results in formation of various
defects sites on the network of NPCꢀ[C N][SO CF ]. In addition, several peaks
associated with H 40 could also observed in NPCꢀ[C N][H 40], which
indicates heteropolyacid of H PW O could also be immobilized into NPC support
3 3 3 3 3 3
N][SO CF ], the decreased intensity in NPCꢀ[C N][SO CF ] may be
3
3
3
3
PW12
O
3
2
PW12O
3
12 40
(
Figure S1). The above results confirm controllable and strong acid sites were formed
in NPCꢀ[C N][X].
3 3
Figure 2 showed Raman spectra of NPC and NPCꢀ[C N][SO CF ], both of them
x
3
showed two broad peaks associated with Dꢀband and Gꢀband, respectively. Notably,
the Dꢀband was attributed to sp3 carbon atoms in the network in these samples; while
Gꢀband was attributed to sp2 carbon atoms in a graphitic 2D hexagonal lattice in these
samples. Compared with Gꢀband peaks, the obviously stronger Dꢀband peaks in NPC
and NPCꢀ[C
addition, broad peaks ranging from 2400 to 3000 cm associated with the signal of
D band could also observed in the secondꢀorder Raman spectra in both samples,
which further confirms amorphous network, the presence of high proportions of edge
3 3 3
N][SO CF ] indicated their typically amorphous carbon network. In
ꢀ1
2
36
planes and structure defects in these samples . Compared with NPC, the decreased
Gꢀband of NPCꢀ[C N][SO CF ] may be attributed to formation of various defects
3
3
3
1
5

Catalysis Science & Technology
Page 16 of 48
View Article Online
DOI: 10.1039/C5CY01226K
sites on its network, which should be resulted from grafting of acidic groups, in good
agreement with XRD results.
+
2 3
Figure 3 showed N isotherms and pore size distribution of NPC, NPCꢀ[C N]
and NPCꢀ[C N][SO CF ]. Notably, a steep increase in the curve at a relative pressure
3
3
3
ꢀ6
of 10 <P/P
0
<0.01 due to the filling of micropores could be clearly observed in these
samples, which confirm abundant micropores (~0.64 nm) was formed in the samples
3
7
+
.
3
After acidification of NPC to give the sample of NPCꢀ[C N] and
+
NPCꢀ[C
3
N][SO
3
3
CF ]. NPCꢀ[C
3
N] gave an additional small hysteresis loop at a
relative pressure 0.5<p/p <0.8 (Figure 3b) in comparison with NPC support, which
0
+
gave the pore size at around 4 nm. Further treating of NPCꢀ[C
HSO CF , giving the sample of NPCꢀ[C N][SO CF
isotherms with an enhanced hysteresis loop at a relative pressure 0.5<p/p
c). The pore size distribution of resultant NPCꢀ[C N][SO CF ] was also centered at
3
N] with strong acid of
3
3
3
3
3
], which showed typicalꢀIV
<0.8 (Figure
0
3
3
3
3
around 4 nm. The above results indicated that acidification of NPC may result in the
broken of bulky NPC monolith into nanoscaled particles, and the metastable
nanoparticles quickly aggregated again, which results in the formation of additional
+
33
mesopores in NPCꢀ[C
3
N] and NPCꢀ[C
3
N][SO
3
3
CF ] . Compared with NPC support,
2
the decreased BET surface area (1600 Vs 525 m /g) and pore volume (0.82 Vs 0.36
3
cm /g) of NPCꢀ[C N][SO CF ] should be attributed to the grafting of acidic groups in
3
3
3
the sample, which largely increases the weight and blocks the nanopores of the
3
2
sample (Table 1), similar results have also been reported previously . Notably, the
BET surface area of NPCꢀ[C N][SO CF ] was higher than those of Amberlyst 15, and
3
3
3
1
6

Page 17 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
ZSMꢀ5, lower than those of USY zeolite and sulfonic group functionalized
mesoporous silica (SBAꢀ15ꢀSO H) (Table 1). The abundant nanoporous structures
could also be observed in the sample of NPCꢀ[C N][H 40] (Figure S2).
Figure 4 showed SEM images of NPCꢀ[C N][SO CF ], which exhibited
3
3
2
PW12O
3
3
3
monolithic morphology with disordered shapes. In the meantime, the enlarged images
of NPCꢀ[C N][SO CF ] gave the rough surface characteristics, which may be
attributed to presence of nanopores in the sample. Moreover, the EDX spectrum and
elemental maps of NPCꢀ[C N][SO CF ] have also been carefully investigated, which
were efficient tools for characterization of the elemental components and dispersion
state. Interestingly, NPCꢀ[C N][SO CF ] showed the signals of C, N, O, and S
elements, which were homogeneously dispersed into NPCꢀ[C N][SO CF ] (As shown
3
3
3
3
3
3
3
3
3
3
3
3
in Figure 5 CꢀF). Notably, the content of S obtained from EDX result (6.21 %) was
similar with the result obtained from elemental analysis (6.7 %, Table 1), which was
higher than that of SBAꢀ15ꢀSO H, lower than that of Amberlyst 15. The above results
3
confirm that acidic groups have been successfully grafted onto the network of NPC.
Figure 6 showed TEM images of NPCꢀ[C
monolithic morphology with abundant nanopores. In addition, the highꢀresolved TEM
images showed that NPCꢀ[C N][SO CF ] has abundant wormꢀhole like micropores,
which exhibited amorphous characteristics, in agreement with XRD, Raman and N2
isotherms results. Except for micropores, NPCꢀ[C N][SO CF ] also showed abundant
mesopores (Figure 6A), which was formed through aggregating of small particles, in
agreement with N isotherms results. In general, the acidification of NPC may result
3 3 3
N][SO CF ], which exhibited
3
3
3
3
3
3
2
1
7

Catalysis Science & Technology
Page 18 of 48
View Article Online
DOI: 10.1039/C5CY01226K
in the broken of bulky monolith into nanoscaled particles, and the metastable
3
nanoparticles aggregated again to form additional mesopores in NPCꢀ[C N][SO CF ]
3
3
in comparison with NPC support. The above results confirm the template free route
exploited by us could be used for preparation of porous carbon based solid acid, and
3 3 3
the abundant nanopores of NPCꢀ[C N][SO CF ] largely enhance the fast diffusion of
reactants and products in various acidꢀcatalyzed reactions.
Figure 7 showed TG and DTA curves of NPC and NPCꢀ[C
3
3 3
N][SO CF ], which
was an efficient way for investigation of thermal stability of various materials.
Notably, NPC showed the weight loss at the temperature stages ranging from 30ꢀ100
and 480ꢀ590 °C, which should be attributed to losing of absorbed water and the
destruction of its carbonaceous network, the higher decomposition temperature of
NPC indicates its very good thermal stability for usage as catalyst support. After
3 3 3
grafting acidic groups onto NPC, giving the sample of NPCꢀ[C N][SO CF ], which
exhibited the weight loss associated with the desorption of water, decomposition of
acidic group, and destruction of carbonaceous network at the temperature stages
ranging from 30ꢀ100, 190ꢀ330, and 450ꢀ550 °C, respectively (Figure 7A). Similar
results could also be observed in DTA curves (Figure 7B). The high decomposition
3 3 3
temperatures of both acidic group and carbonaceous network in NPCꢀ[C N][SO CF ]
indicates its very good thermal stability, which was very important for it used as
stable and reusable solid acid in various acidꢀcatalyzed liquid reactions. Compared
with NPC, the decreased temperature of the destruction of carbonaceous network
should be attributed to presence of oxygen containing groups such as –OH in the
1
8

Page 19 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
sample, which was resulted from the treatment of carbonaceous network with
,3ꢀpropanesultone and ultra strong acids of HSO CF
Figure 8 showed the Xꢀray photoelectron spectroscopy (XPS) spectra of
NPCꢀ[C N][SO CF ], which exhibits the signals of S (168.6 eV), C (285.4 eV),
1
3
3
.
3
3
3
2p
1s
N
1s (400.8 eV), O1s (532.7 eV) and F1s (688.4 eV) because of grafting of
ꢀ
[C N][SO CF ] group onto NPC support. Notably, the broad signal of C1s could be
3
3
3
fitted and deconvoluted into four peaks (284.8, 286.3, 287.8 and 292.3 eV), which
should be assigned to CꢀC and CꢀN bond in NPC network, and CꢀS and CꢀF bond in
32, 38
ꢀ
[C N][SO CF ] group, respectively
. In addition, two broad peaks associated with
3
3
3
N
1s were centered at approximately 399.1 and 401.2 eV, which should be attributed to
3
1, 36
the signals of CꢀN and [C
3
N] group in NPCꢀ[C
H (531.5 eV) and OꢀSCF
. The above results indicate that strong acidic group has been
3
N][SO
3
CF
3
]
. Similarly, the
signals of O1s associated with –SO
3
3
(532.8 eV) could also
32, 38
be clearly observed
successfully grafted onto the network of NPC, in good agreement with elemental
analysis and elemental maps results (Table 1). Correspondingly, FTꢀIR spectrum
further confirms the above results (As shown in Figure 9), the peaks at around 683,
ꢀ1
1
068 and 1179 cm should be assigned to the signals of CꢀS and S=O bond in the
ꢀ1
sample, and the peak at around 1282 cm should be assigned to the signal of CꢀF
bond, which further confirm the successfully grafting of strong acidic group onto NPC
support.
13
Figure 10 showed C solid NMR spectrum of NPCꢀ[C
3
N][SO
3
3
CF ]. The strong
peak at around 16 ppm should be assigned to CH carbon in C
3
3
N group or NPC
1
9

Catalysis Science & Technology
Page 20 of 48
View Article Online
DOI: 10.1039/C5CY01226K
network. The peaks at around 61 and 49 ppm are assigned to methylene carbon linked
3
9
with sulfonic group and nitrogen in C
3
N group , which is indicative that the
[
ꢀCH CH CH SO H] group has been bonded onto NPC network. Notably, the peak at
2
2
2
3
around 68 ppm should be assigned to CꢀOH carbon, which maybe resulted from
partial oxidation of NPC network during acidification processes. Alternatively, the
broad peaks at around 129 and 139 ppm should be assigned to the CꢀC and CꢀN bond
in NPC network. The above results indicated strong acidic group has been
successfully grafted onto the network of NPC, in good agreement with XPS and
FTꢀIR spectra results.
31
Figure 11 showed the P NMR probe spectra of NPCꢀ[C
3 3 3
N][SO CF ], which
involves the adsorbed trimethylphosphine (TMP) and trimethylphosphine oxygen
31
(
TMPO). It is well known that the P NMR probe technique is a sensitive and reliable
3
4,
technique to characterize the acidity (Acid types and strength) of various solid acids
4
0, 41
.
In Figure 11a, TMP was used as a probe molecule, and the peak at around ꢀ3.4
+
ppm was assigned to the protonated adducts of [(CH
3
)
3
PꢀH] , which was resulted
from the reaction between TMP and typically Brønsted acidic protons. On the contrary,
the peaks ranged from ꢀ20 to ꢀ60 ppm associated with the interaction between TMP
34, 40
and Lewis acid sites could not be found
, which indicates that typically Brønsted
31
acid sites was formed in NPCꢀ[C N][SO CF ]. In the meantime, solidꢀstate P MAS
3
3
3
3 3 3
NMR spectrum of adsorbed TMPO by NPCꢀ[C N][SO CF ] was also carefully
investigated, which could accurately determine the acid strength of various solid acids
such as zeolites, sulfonic group functionalized mesoporous silica, sulfated
2
0

Page 21 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
39, 40
mesoporous metal oxides and heteropolyacids
3 3 3
. Interestingly, NPCꢀ[C N][SO CF ]
31
showed multiple P resonance peaks at around 45, 53, 64, and 80 ppm, which
indicates the acid sites with different acid strength were formed in
NPCꢀ[C N][SO CF ] (Figure 11b). The weak acidic sites (45 ppm) may be attributed
3
3
3
3 3 3
to hydroxyl groups in NPCꢀ[C N][SO CF ]; While the relative strongly acidic site at
around 53 ppm may be attributed to protonated nitrogen atom in NPC network by
+
HSO
3
CF
3
, which may form the structure of NPCꢀ[N H][SO
3
3
CF ]. Interestingly, the
strong acidic sites at around 64 and 80 ppm should be attributed to sulfonic group and
acidic ionic liquids group located over NPCꢀ[C N][SO CF ] catalyst surfaces. The
3
3
3
aforementioned results directly confirmed strong and controllable acidic group has
been grafted onto NPC support, which result in the formation of NPCꢀ[C N][SO CF ].
NPCꢀ[C N][SO CF ] showed relatively strong acidity in comparison with those of HY
zeolites (55 and 65 ppm) and bifunctional carbonꢀsilica nano composited solid acid
3
3
3
3
3
3
31
41, 42
(
40ꢀ70 ppm) based on the P chemical shift of adsorbed TMPO probe
. Therefore,
this novel catalyst possibly has a better catalytic role for the acid catalyzed reactions
for its unique structure and controllable acidity.
Figure 12 showed catalytic kinetics curves in transesterification of tripalmitin
with methanol catalyzed by various samples, which was thought to be an efficient
32
way for production of biodiesel . Notably, NPCꢀ[C N][SO CF ] showed much
3
3
3
improved catalytic activity in comparison with conventional solid acids such as
SBAꢀ15ꢀSO H, Amberlyst 15 and Hꢀform ZSMꢀ5 zeolite, which was as comparable
as that of homogeneous heteropolyacid of H 40. For instance, after 6 h of
3
3
PW12O
2
1

Catalysis Science & Technology
Page 22 of 48
View Article Online
DOI: 10.1039/C5CY01226K
3 3 3
incubation, the yield of methyl palmitate catalyzed by NPCꢀ[C N][SO CF ] was
5
3 40
2.5 %. On the contrary, the yields of methyl palmitate catalyzed by H PW12O ,
3
SBAꢀ15ꢀSO H, and Amberlyst 15 were 32.4, 26.0 and 21 %, respectively; Further
prolonging the reaction time up to 14 h, the yield of methyl palmitate catalyzed by
NPCꢀ[C N][SO CF ] was increased up to 82.9 %, much higher that those of
40 (70.1 %), SBAꢀ15ꢀSO H (57.2 %), and Amberlyst 15 (49.6 %).
3
3
3
H
3
PW12
O
3
Nevertheless, the yield of methyl palmitate catalyzed by Hꢀform ZSMꢀ5 (10.8 %) was
very low even the reaction time was increased up to 14 h because of its constrained
micropores, which strongly restrict its catalytic applications for bulky molecules.
Moreover, NPCꢀ[C
being recycled for 5 times, very little decreased yield of methyl palmitate catalyzed by
recycled NPCꢀ[C N][SO CF ] should be resulted from the coverage of acidic sites by
3 3 3
N][SO CF ] also showed good reusability. For instance, even after
3
3
3
reactants and products (Figure 12b). The above results confirmed that
NPCꢀ[C N][SO CF ] act as highly efficient and stable solid acids for catalyzing
3
3
3
biodiesel production.
Furthermore, the catalyze production of biodiesel through esterification of fatty
acid with methanol has also been carefully investigated in this work. Figure 13
showed the catalytic kinetics curves of palmitic acid with methanol catalyzed by
various solid acids. Notably, NPCꢀ[C N][SO CF ] showed much improved activity in
3
3
3
comparison with various solid acids. For instance, only for 1 h, the yield of methyl
palmitate catalyzed by NPCꢀ[C N][SO CF ] was up to 90.8 %, much higher than
those Amberlyst 15 (55.2 %), SBAꢀ15ꢀSO H (55.2 %), and HꢀZSMꢀ5 (3.5 %), which
3
3
3
3
2
2

Page 23 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
was as comparable as that of H
time to 3 h, the yield of methyl palmitate catalyzed by NPCꢀ[C
nearly 100 %, while Amberlyst 15, SBAꢀ15ꢀSO H, HꢀZSMꢀ5, and H
relatively low yields at 73.5, 76.8, 11.6, and 96.9 %, respectively.
On the other hand, NPCꢀ[C N][SO CF ] type of solid acids were also very active
3
PO40W
12 (90.2 %). Further prolonging the reaction
3
N][SO CF ] was
3
3
3
3
PO40W12 gave
3
3
3
in other biomass transformation reactions such as fructose dehydration into HMF and
depolymerization of crystalline cellulose into sugars. Table 2 presents the activities of
various acidic catalysts for catalyzing fructose dehydration, which was an important
22, 43-45
model reaction for transformation sugars into useful chemicals
NPCꢀ[C N][SO CF ] showed excellent catalytic activity and products selectivity in
comparison with those of Amberlyst 15, SBAꢀ15ꢀSO H, and HꢀZSMꢀ5. For instance,
the yields of two main products of HMF and furanꢀ2,5ꢀdicarbaldehyde catalyzed by
NPCꢀ[C N][SO CF ] were 79.5 and 8.1 % after 10 h of reaction, much higher than
those of SBAꢀ15ꢀSO H (53.2 & 4.1 %), HꢀZSMꢀ5 (38.6 & 3.7 %), and Amberlyst 15
. Notably,
3
3
3
3
3
3
3
3
(
50.3 & 4.6 %). Similar superior activity could also be observed in NPCꢀ[C
3 4
N][SO H]
(
80.1 & 7.8 %). More importantly, NPCꢀ[C N][SO CF ] showed very good reusability,
3
3
3
even after being recycled for five times, the yields of HMF and
furanꢀ2,5ꢀdicarbaldehyde catalyzed by recycled NPCꢀ[C N][SO CF ] (77.2 & 7.5 %)
were even as comparable as those of fresh NPCꢀ[C N][SO CF ] (79.5 & 8.1 %, Table
3
3
3
3
3
3
2
, Run 1).
In the meantime, NPCꢀ[C
catalyzing depolymerization of crystalline cellulose into sugars: an important reaction
3
3 3
N][SO CF ] also showed very good activity for
2
3

Catalysis Science & Technology
Page 24 of 48
View Article Online
DOI: 10.1039/C5CY01226K
in the areas of biomass transformation, which showed potentially important
applications in industry because of very large storage and low cost of crystalline
22
cellulose in nature . For instance, after 5 h of incubation, the yields of TRS catalyzed
by NPCꢀ[C N][SO CF ] and NPCꢀ[C N][SO H] were up to 78.5 and 79.2 %
3
3
3
3
4
respectively, much higher than those of conventional solid acids including Amberlyst
5 (60.2 %), SBAꢀ15ꢀSO H (51.8 %), HꢀZSMꢀ5 (26.7 %), and HꢀUSY (42.6 %).
Correspondingly, the yields of main products of glucose, cellobiose and HMF
catalyzed by NPCꢀ[C N][SO CF ] (50.3, 17.3 and 9.8 %) and NPCꢀ[C N][SO H]
47.5, 22.3 and 9.2 %) were much higher than those of Amberlyst 15 (30.3, 18.4 and
.6 %), SBAꢀ15ꢀSO H (25.4, 13.6 and 4.1 %), HꢀZSMꢀ5 (10.4, 7.6 and 2.8 %), and
HꢀUSY (22.5, 11.2 and 3.5 %, Table 3). The catalytic data also indicated relatively
good selectivity for glucose and HMF catalyzed by NPCꢀ[C N][SO CF ] and
NPCꢀ[C N][SO H] (Table 3). The above results confirmed that NPCꢀ[C N][SO CF
1
3
3
3
3
3
4
(
4
3
3
3
3
3
4
3
3
3
]
and NPCꢀ[C N][SO H] act as novel and efficient solid acids for catalyzing biomass
3
4
transformations.
At last, we successively expand the catalytic applications of NPCꢀ[C
in condensation of phenol with acetone, which was an important reaction for synthesis
of bisphenolꢀA. More importantly, NPCꢀ[C N][SO CF ] showed much improved
activity in comparison with above solid acids (Table 4). For instance, after 24 h of
incubation, the conversions of phenol catalyzed by NPCꢀ[C N][SO CF ] and
NPCꢀ[C N][SO H] were 21.4 and 22.5 % respectively, which gave the TOF values at
.8 and 3.75 h respectively (The completed conversion of phenol through
3 3 3
N][SO CF ]
3
3
3
3
3
3
3
4
ꢀ1
3
2
4

Page 25 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
theoretical calculation is 28.6%), similar results could also be observed in
ꢀ1
NPCꢀ[C
SBAꢀ15ꢀSO
3.4, 10.9, 8.7 and 4.8 %, which exhibited the TOF values at 1.2, 3.3, 2.0 and 5.0,
3
N][H
2
PW12O40] (20.6, 4.1 h ). On the contrary, Amberlyst 15,
3
H, HꢀUSY and HꢀZSMꢀ5 gave relatively low conversions of phenol at
1
respectively. It is noteworthy that all the solid acids showed similar selectivity for the
products of p,p'ꢀbisphenolꢀA and o,pꢀbisphenolꢀA.
3 3 3
The above results confirm that NPCꢀ[C N][SO CF ] could be used as highly
efficient and reusable carbon based solid acids in various acidꢀcatalyzed reactions.
The excellent activity and reusability found in NPCꢀ[C N][SO CF ] should be
3
3
3
attributed to their unique characteristics including large BET surfaces, abundant
nanopores, good stability, controllable and strong acidity. The large surface area and
abundant nanopores strongly enhance the fast diffusion of reactants and products in
the samples, further resulting in much improved exposure degree of acidic sites in
NPCꢀ[C N][SO CF ].
Moreover,
] effectively decrease the activation energy in these reactions. The
N][SO CF ] acts as highly efficient and reusable
controllable
and
strong
acidity
of
3
3
3
NPCꢀ[C
3
N][SO
3
CF
3
above advantages make NPCꢀ[C
3
3
3
solid acids in various reactions, further consideration of their facile and costꢀeffective
synthetic processes, which will be very important for their widely practical
applications in the area of heterogeneous acid catalysis.
4
. Conclusions
N rich porous carbon was synthesized from carbonization of polypyrrole in
2
5

Catalysis Science & Technology
Page 26 of 48
View Article Online
DOI: 10.1039/C5CY01226K
presence of KOH without using additional templates, which was used as novel and
stable support for grafting with strong acidic groups, the resultant NPCꢀ[C N][X] type
x
of solid acids showed large BET surface areas, good stability, abundant nanopores,
controllable and strong acidity. The above characteristics result in NPCꢀ[C N][X] with
x
much improved activity and good reusability for catalyzing biomass transformations
x
and fine chemical synthesis. The preparation of NPCꢀ[C N][X] will develop a new
way to synthesize efficient and reusable carbonaceous solid acids with controllable
nanopores and strong acid sites, and good catalytic activities, which will be very
important for the wide applications of carbonaceous solid acids in the area of
heterogeneous acid catalysis.
Acknowledgements: This work was supported by the National Natural Science
Foundation of China (21573150, 21203122, 21473244, 21522310), Natural Science
Foundation of Zhejiang Province (LY15B030002). Foundation of State Key
Laboratory of Magnetic Resonance and Atomic, Molecular Physics, Wuhan Institute
of Physics and Mathematics, Chinese Academy of Sciences (T151303).
2
6

Page 27 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
References
1
2
R. Ryoo, S. H. Joo and S. Jun, J. Phys. Chem. B 1999, 103, 7743.
F. Su, J. Zeng, X. Bao, Y. Yu, J. Y. Lee and X. S. Zhao, Chem. Mater. 2005, 17,
960.
3
3
4
5
Y. P. Zhai, Y. Q. Dou, D. Y. Zhao, P. F. Fulvio, R. T. Mayes and S. Dai, Adv.
Mater. 2011, 23, 4828.
K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V.
Dubonos, I. V. Grigorieva and A. A. Firsov, Science 2004, 306, 666.
K. S. Noveselov, A. K. Geim, S. V. Morozov, D. Jiang, M. I. Katsnelson, I. V.
Grigorieva, S. V. Dubonos and A. A. Firsov, Nature 2005, 438, 197.
D. S. Su, S. Perathoner and G. Centi, Chem. Rev. 2013, 113, 5782.
S. Iijima, Nature 1991, 354, 56.
6
7
8
Y. Meng, D. Gu, F. Q. Zhang, Y. F. Shi, H. F. Yang, Z. Li, C. Z. Yu, B. Tu and
D. Y. Zhao, Angew. Chem., Int. Ed. 2005, 44, 7053.
9
1
C. D. Liang and S. Dai, J. Am. Chem. Soc. 2006, 128, 5316.
X.ꢀH. Li, S. Kurasch, U. Kaiser and M. Antonietti, Angew. Chem. Int. Ed.
0
1
2
2
012, 51, 9689.
P. P. Su, L. Jiang, J. Zhao, J. W. Yan, C. Li and Q. H. Yang, Chem. Commun.
012, 48, 8769.
Y. Wang, J. Yao, H. R. Li, D. S. Su and M. Antonietti, J. Am. Chem. Soc. 2011,
33, 2362.
1
1
2
1
2
7

Catalysis Science & Technology
Page 28 of 48
View Article Online
DOI: 10.1039/C5CY01226K
1
3
P. F. Zhang, Y. T. Gong, H. R. Li, Z. R. Chen and Y. Wang, Nat. Comm. 2012,
, 1593.
4
1
4
5
K. Woan, G. Pyrgiotakis and W. Sigmund, Adv. Mater. 2009, 21, 2233.
A. Thomas, A. Fischer, F. Goettmann, M. Antonietti, J.ꢀO. Müller, R. Schlögl
and J. M. Carlsson, J. Mater. Chem. 2008, 18, 4893.
1
16
17
18
19
J. Zhang, X. Liu, B. Raoul, A. H. Zhang, R. Schlögl and D. S. Su, Science
2
008, 322, 73.
G.ꢀL. Chai, Z. F. Hou, D.ꢀJ. Shu, T. Ikeda and K. Terakura, J. Am. Chem. Soc.
014, 136, 13629.
2
K. Wan, G.ꢀF. Long, M.ꢀY. Liu, L. Du, Z.ꢀX. Liang and P. Tsiakaras, App.
Catal. B: Environ. 2015, 165, 566.
C. H. Choi, H.ꢀK. Lim, M. W. Chung, C. P. Jong, H. Shin, H. Kim and S. Woo,
J. Am. Chem. Soc. 2014, 136, 9070.
2
0
1
P. Serp, M. Corrias and P. Kalck, App. Catal. A-Gen. 2003, 253, 337.
F. J. Liu, J. Sun, L. F. Zhu, X. J. Meng, C. Z. Qi and F.ꢀS. Xiao, J. Mater.
Chem. 2012, 22, 5495.
2
22
23
24
J. S. Luterbacher, D. Martin Alonso and J. A. Dumesic, Green Chem. 2014, 16,
4816.
X. Q. Wang, R. Liu, M. M. Waje, Z. W. Chen, Y. S. Yan, K. N. Bozhilov and P.
Y. Feng, Chem. Mater. 2007, 19, 2395.
R. Xing, Y. M. Liu, Y. Wang, L. Chen, H. H. Wu, Y. W. Jiang, M. Y. He and P.
Wu, Micro. Meso. Mater. 2007, 105, 41.
2
8

Page 29 of 48
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C5CY01226K
2
5
6
X. Z. Liang, M. F. Zeng and C. Z. Qi, Carbon 2010, 48, 1844.
2
J. F. Pang, A. Q. Wang, M. Y. Zheng and T. Zhang, Chem. Comm. 2010, 46,
935.
6
27
28
29
30
31
X. M. Zhang, Y. P. Zhao, S. T. Xu, Y. Yang, J. Liu, Y. X. Wei and Q. H. Yang,
Nat. Comm. 2013, 5, 3170.
S. Suganuma, K. Nakajima, M. Kitano, D. Yamaguchi, H. Kato, S. Hayashi
and M. Hara, J. Am. Chem. Soc. 2008, 130, 12787.
M. Toda, A. Takagaki, M. Okamura, J. N. Kondo, S. Hayashi, K. Domen and
M. Hara, Nature 2005, 438, 7065.
M. Hara, T. Yoshida, A. Takagaki, T. Takata, J. N. Kondo, S. Hayashi and K.
Domen, Angew. Chem. Int. Ed. 2004, 43, 2955.
P. A. Russo, M. M. Antunes, P. Neves, P. V. Wiper, E. Fazio, F. Neri, F. Barreca,
L. Mafra, M. Pillinger, N. Pinna and A. A. Valente, Green Chem. 2014, 16,
4292.
32
33
34
35
F. J. Liu, L. Wang, Q. Sun, L. F. Zhu, X. J. Meng and F.ꢀS. Xiao, J. Am. Chem.
Soc. 2012, 134, 16948.
J. A. Melero, G. D. Stucky, R. van Griekena and G. Morales, J. Mater. Chem.
2
002, 12, 1664.
A. Zheng, S. J. Huang, S. B. Liu and F. Deng, Phys. Chem. Chem. Phys. 2011,
3, 14889.
1
S. PérezꢀRodríguez, N. Rillo, M. J. Lázaro and E. Pastor, App. Catal. B:
Environ. 2015, 163, 83.
2
9