Platinum deposited on cerium coordination polymer for catalytic oxidation of hydroxymethylfurfural producing 2,5-furandicarboxylic acid

Article abstract of DOI:10.1039/c7ra05427k

2,5-Furandicarboxylic acid (FDCA) is a value added chemical that can be used as a polymer building block for the synthesis of biobased polymers. Developing efficient catalysts is fundamentally important for the selective oxidation of 5-hydroxymethylfurfural (HMF) into FDCA. In this work, a novel catalyst was prepared at mild conditions by forming platinum nanoparticles on a cerium coordination polymer (CeCP), which was synthesized using 1,3,5-benzenetricarboxylic acid as the ligand. The CeCP@Pt catalyst was utilized for the selective oxidation of highly concentrated HMF into FDCA. The yield of FDCA could reach 96.2% after 12 h of reaction at 70 °C in water at atmospheric conditions. Furthermore, this catalyst can be reused at least five times without significant activity loss. After five recycling cycles, the leaching of Pt from CeCP@Pt was negligible. This work demonstrated the advantages of the CeCP@Pt catalyst, including its easy preparation in mild conditions, application at relatively low temperatures and in atmospheric conditions, catalyzing the oxidation of HMF with a high concentration, and its reuse with a high stability.

Full text of DOI:10.1039/c7ra05427k

RSC Advances
View Article Online
View Journal | View Issue
PAPER
Platinum deposited on cerium coordination
polymer for catalytic oxidation of
hydroxymethylfurfural producing 2,5-
furandicarboxylic acid
Cite this: RSC Adv., 2017, 7, 34776
Wei Gong, Kunkun Zheng and Peijun Ji
*
2,5-Furandicarboxylic acid (FDCA) is a value added chemical that can be used as a polymer building block
for the synthesis of biobased polymers. Developing efficient catalysts is fundamentally important for the
selective oxidation of 5-hydroxymethylfurfural (HMF) into FDCA. In this work, a novel catalyst was
prepared at mild conditions by forming platinum nanoparticles on a cerium coordination polymer
(CeCP), which was synthesized using 1,3,5-benzenetricarboxylic acid as the ligand. The CeCP@Pt catalyst
was utilized for the selective oxidation of highly concentrated HMF into FDCA. The yield of FDCA could
ꢀ
reach 96.2% after 12 h of reaction at 70 C in water at atmospheric conditions. Furthermore, this catalyst
can be reused at least five times without significant activity loss. After five recycling cycles, the leaching
of Pt from CeCP@Pt was negligible. This work demonstrated the advantages of the CeCP@Pt catalyst,
including its easy preparation in mild conditions, application at relatively low temperatures and in
atmospheric conditions, catalyzing the oxidation of HMF with a high concentration, and its reuse with
a high stability.
Received 13th May 2017
Accepted 30th June 2017
DOI: 10.1039/c7ra05427k
rsc.li/rsc-advances
oxidant, the aerobic oxidation was catalyzed mostly by hetero-
1
. Introduction
7–11
geneous catalysts. Noble-metal catalysts, including inorganic
12–15
The development of platform chemicals from biomass material-supported Pt, Pd, Ru and Au nanoparticles,
have
resources is of signicant importance from an environmental been extensively studied, as the catalysts can have long-term
point of view. Among the biobased chemicals, 5-hydrox- catalytic performance, high selectivity, and good recyclability.
ymethylfurfural (HMF) is a versatile platform chemical and can A magnetical catalyst based on Pd nanoparticles can achieve
1,2
16
be used to synthesize valuable chemicals.
Chemicals 86.7% yield of FDCA with reaction time 10 h. The Pd/C cata-
including 2,5-diformylfuran (DFF), 2,5-formylfurancarboxylic lysts reported by Davis et al. converted 100% HMF with a FDCA
17
2
acid (FFCA), 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), yield of 71% with 2 equivalent NaOH at 69 bar. CeO -Sup-
and 2,5-furandicarboxylic acid (FDCA) can be produced by the ported Au nanoparticles exhibited the oxidation of HMF into
ꢀ
oxidation of HMF (Scheme 1). Among these chemicals, FDCA is FDCA with a yield of 99% at 130 C with 4 equivalents of
18
a value added chemical. It can be used as a polymer building NaOH. However, the catalyst lost its activity aer one cycle.
3
4
block for the synthesis of polyamides, polyesters, and bio- Supported Pt catalysts have shown high activity for the oxida-
5
based epoxy resins. The promising biobased polymer poly- tion of HMF into FDCA. Carbon-supported Pt catalysts
19
ethylene furanoate (PEF) can be produced from the esterica- produced FDCA with yields of 81% by Verdeguer et al. and
6
17
tion of ethane-1,2-diol and FDCA. By account of the growing 79% by Davis et al. PVP-Stabilized Pt (Pt–PVP–GLY) achieved
demand for sustainable packaging materials, PEF has the
potential to replace polyethylene terephthalate (PET), which has
been used for the production of bottles for the packaging of
water, so drinks, and fruit juices.
Selective oxidation of HMF generating FDCA has been
extensively investigated. The aerobic oxidation of HMF into
FDCA is generally carried out at alkaline conditions and at high
temperatures and high pressures. With oxygen used as the
Scheme
1 Oxidation of HMF producing various chemicals 5-
hydroxymethylfurfural (HMF); 2,5-diformylfuran (DFF); HMFCA: 5-
hydroxymethyl-2-furancarboxylic acid; 2,5-formylfurancarboxylic
acid (FFCA); 2,5-furandicarboxylic acid (FDCA).
Department of Chemical Engineering, Beijing University of Chemical Technology,
Beijing, China. E-mail: jipj@mail.buct.edu.cn; Tel: +86 10 64423254
34776 | RSC Adv., 2017, 7, 34776–34782
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
ꢀ
20
a FDCA yield of 95% at 80 C aer 24 h. The oxidation of HMF HCl (3 ml), and HF (50 wt%, 2 ml). 1 g sample was digested in
catalyzed by reduced graphene oxide-supported metal nano- the solution. Aer digestion, the sample was diluted 10 fold
21
particles produced FDCA with a yield of 40.6%. g-A1 O -Sup- with deionized water. The solution was subjected to ICP atomic
2
3
ported Pt (Pt/g-A1 O ) and ZrO -supported Pt (Pt/ZrO ) emission spectrometric analysis.
2
3
2
2
22,23
produced FDCA with yields of 96% and 94%, respectively.
contrast, TiO -supported Pt (Pt/TiO ) and CeO
Pt/CeO ) catalysts produced FDCA with low yields of 2% and
%, respectively. Addition of Bi to the supports can improve
the catalytic performance. The Pt–Bi/C catalyst achieved a FDCA
In
2
2
2
-supported Pt
2
.4. Aerobic oxidation of HMF
(
8
2
0.5 mmol of HMF and different amounts of sodium hydroxide
23
ꢀ
(NaOH) were dissolved in water (10 ml) at 70 C. Then a certain
amount of CeCP@Pt catalyst was introduced to the mixture to
initiate the reaction. During the reaction, oxygen was permitted
to ow at the bottom of the reactor continuously with a ow rate
of 30 ml min . Aer the reaction, the catalyst was collected
aer washing and centrifugation, and dried under vacuum
ꢀ
24
yield of 98% under 40 bar air at 100 C. Pt–Bi/TiO catalyst also
2
2
5
showed high catalytic activity and stability. Pt–Bi/CeO catalyst
2
26
could also signicantly improve the catalytic efficiency.
ꢁ1
In this work, cerium coordination polymer (CeCP) was
synthesized using 1,3,5-benzenetricarboxylic acid as the ligand.
Platinum nanoparticles were formed and deposited on the
surface of CeCP. The composite CeCP@Pt was utilized for the
oxidation of the oxidation of 5-hydroxymethylfurfural producing
ꢀ
(45 C) for the next recycling reaction.
The substrate and intermediate and nal products were
analyzed by HPLC (Shimadzu 15 LC-10A) with a Zorbax Eclipse
XDB-C8 column (Agilent). The mobile phase consisted of
phosphate buffer (12 mM, pH 7.0) and acetonitrile at a ow rate
2,5-furandicarboxylic acid.
ꢁ1
of 1.3 ml min . Aer 1.5 min of phosphate buffer, acetonitrile
2
. Experiment
was increased to 5% in 4.0 min and subsequently to 40% in
3
min. Aer 0.5 min of acetonitrile, the eluent was returned to
2.1. Materials
phosphate buffer in 0.5 min and this level was maintained for
5
1
3 3 2
-Hydroxymethylfurfural ($99%), Ce(NO ) $6H O (99.999%),
,3,5-benzenetricarboxylic acid ($99%), chloroplatinic acid
2
min. Detection was carried out at 268 nm.
(
99.995%), and NaBH4 ($98%) were purchased from Sigma-
2.5. Characterization
Aldrich (Shanghai, China).
The morphology of CeCP@Pt was observed by transmission
electron microscopy (TEM) images, which were recorded on
a FEI Tecnai G2 F20 S-TWIN instrument. XPS spectra were
measured using an X-ray photoelectron spectrometer (Thermo
VG ESCALAB250, Beijing, China). The measurement was carried
out at the pressure of 2 ꢂ 10 Pa. Mg KX-ray was used as the
excitation source. The weight percentage of Pt in the CeCP@Pt
composite was analyzed by energy dispersive X-ray spectroscopy
2
.2. Preparation of CeCP@Pt
2.17 g Ce(NO $6H O was dissolved in 45 ml H O, the solution
3
)
3
2
2
was designated as solution A. 1.05 g 1,3,5-benzenetricarboxylic
acid was dissolved in 15 ml ethanol/water (v/v ¼ 1 : 1), the
ꢁ9
ꢀ
solution was designated as solution B. At 60 C under stirring,
solution A was added dropwise to solution B, and stirring was
carried out for 2 h. Then the mixture was cooled to room
temperature. The mixture was then ltered, washed rst with
water and then with ethanol until the ltrate being neutral. The
synthesized CeCP was nally dried at 60 C under vacuum for
1
(EDS) using a JEOL JSM-6700F microscope.
ꢀ
2.6. Catalysis comparison
2
The calcination of CeCP at 650 C resulted in CeO . Pt was
ꢀ
cal
2 h.
CeCP@Pt composites were prepared using CeCP and chlor- supported on the CeO
oplatinic acid hydrate (H PtCl ). Different CeCP to H PtCl
the same preparation procedure as that for CeCP@Pt (5.4%).
cal
2
com
2
and on commercial CeO
2
(CeO
) with
2
6
2
6
cal
2
com
2
mass ratios were used. 5 mg CeCP was dispersed in 40 ml 5 mg CeO
or CeO
was dispersed in 40 ml ethanol and
ethanol and sonicated for 10 min. Then 0.23, 0.27, 0.54, 0.81, sonicated for 10 min. Then 0.23 ml of the chloroplatinic acid
ꢁ
1
and 1.35 ml of the solutions of chloroplatinic acid (15.8 mg solution (15.8 mg ml ) was added dropwise and sonicated for
ꢁ1
ml ) were separately added dropwise and sonicated for 10 min. 10 min. Then the freshly prepared sodium borohydride solution
Then the freshly prepared sodium borohydride solution (NaBH , 30 mM, 1 ml) was added and sonicated for 5 min. The
NaBH
, 30 mM, 1 ml) was added and sonicated for 5 min. The resulting product was centrifuged (7000 rpm for 20 min) and
4
(
4
resulting products were centrifuged (7000 rpm for 20 min) and washed with ultrapure water by ltration through a membrane
washed with ultrapure water by ltration through 450 nm pore (450 nm). The centrifugation and washing steps were repeated
size membrane. The centrifugation and washing steps were three times.
repeated 3 times.
2.7. CO chemisorption
2.3. Determination of Pt loading
CO chemisorption on the CeCP@Pt catalysts was measured to
The platinum content in CeCP@Pt was determined by induc- determine the Pt dispersion on CeCP (Auto Chem 2910 instru-
tively coupled plasma (ICP) atomic emission spectrometric ment). The catalysts were pretreated by reduction at 573 K in
analysis (PerkinElmer OPTIMA 3300DV). The solution for He-balanced H (11.0%). At room temperature, CO pulses (He
2
digestion consisted of concentrated HNO
3
(10 ml), concentrated mixture with 10.0% of CO) were injected over the reduced
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 34776–34782 | 34777

View Article Online
RSC Advances
Paper
catalyst. The CO adsorption was assumed to be completed aer
three successive peaks showing the same peak areas. A CO/Pt
stoichiometry of 1 was used for the calculation of the disper-
sion of Pt.
3. Results and discussion
3.1. Characterization of Pt deposited Ce coordination
polymer
2 6
Different CeCP to H PtCl mass ratios were used for the prep-
aration of CeCP@Pt. The Pt content of the obtained CeCP@Pt
was 5.4%, 10%, 19.9%, 32.6%, and 52.7%, respectively, exam-
ined using inductively coupled plasma atomic emission spec-
trometric analysis. TEM images for the samples of CeCP and
CeCP@Pt are shown in Fig. 1. CeCP itself exhibited a rod-like
morphology (Fig. 1a). The Pt nanoparticles were in situ formed
on CeCP. Aer loading Pt, CeCP has kept its original
morphology. The Pt nanoparticles have been well distributed on
the surface of CeCP. The size of Pt nanoparticles was affected by
the amounts loaded. With more Pt deposited on CeCP, larger Pt
nanoparticles were formed. The size-distribution of Pt nano-
particles are shown in Fig. 2, and the averaged sizes of the Pt
nanoparticles are listed in Table 1.
Fig. 2 Pt particle size distribution of various samples (a) CeCP@Pt
Energy dispersive X-ray spectroscopy (EDS) has been used to
analyze the elements. The obtained EDS spectra are shown in
Fig. 3. Fig. 3a is the control for CeCP with peaks for C at 0.235
(
(
5.4%); (b) CeCP@Pt (10%); (c) CeCP@Pt (19.9%); (d) CeCP@Pt (32.6%);
e) CeCP@Pt (52.7%). The numbers in brackets indicate the weight
percentage of Pt.
10
keV, O at 0.52 keV, and Ce at 4.85 and 5.28 keV. The spectra in
Fig. 3b–f are the results of the CeCP@Pt samples with different
loading of Pt. The peaks for Pt appeared in the spectra at 2.66,
Table 1 Average size of Pt particles
Percentage of Pt loaded
5.4% 10% 19.9% 32.6% 52.7%
Average size of Pt particle (nm) 4.5
5.2
8.5
11.0
14.5
10
9
.44, and 11.13 keV, conrming the deposition of Pt on CeCP.
With loading more Pt, the peak intensity of Pt is relatively
increased as shown in Fig. 3b–f. The percentage of Pt is indi-
cated in the brackets of the subtitle, which was determined by
inductively coupled plasma (ICP) atomic emission spectro-
metric analysis.
X-ray photoelectron spectroscopy (XPS) spectra were also
measured for the samples as shown in Fig. 4. For the CeCP@Pt
samples, the Pt peaks appeared. With more Pt deposited on
CeCP, the peak intensity for Pt was increased. The oxidation
states of the Pt nanoparticles were analyzed by Pt 4f core-level
XPS, which were tted by spin–orbit split 4f
and 4f5/2
/2
7
0
components (Fig. 5). The fractions of Pt (71.4 eV and 74.8 eV),
2
+
4+
Pt (72.4 eV and 76.8 eV), and Pt (75.2 eV and 78.6 eV) were
determined by measuring the areas of the respective peaks and
0
are listed in Table 2. Pt is the predominant species on the
surface of CeCP@Pt, the oxidized Pt species was slightly
decreased with the increase of Pt loading. The oxygen in the
high-valence Pt species might come from the ambient air.
Fig. 1 TEM images for CeCP and CeCP@Pt with different loading of Pt
The N adsorption and desorption isotherms of CeCP are
2
(
(
a) CeCP; (b) CeCP@Pt (5.4%); (c) CeCP@Pt (10%); (d) CeCP@Pt
19.9%); (e) CeCP@Pt (32.6%); (f) CeCP@Pt (52.7%). The numbers in
shown in Fig. 6a. The BET specic surface area of CeCP is 28.0
2
ꢁ1
3
ꢁ1
brackets indicate the weight percentage of Pt.
m
g
with pore volumes of 0.10 cm g . The crystalline
34778 | RSC Adv., 2017, 7, 34776–34782
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
Fig. 5 The Pt 4f regions of the XPS spectrum of the series CeCP/Pt
catalysts. The numbers in brackets indicate the weight percentage
of Pt.
a
Table 2 Oxidation state fractions of the Pt nanoparticles
0
0
Pt fractions Pt /
0
2+
4+
Samples
(Pt + Pt + Pt )
CeCP@Pt (5.4%)
CeCP@Pt (10.0%)
CeCP@Pt (19.9%)
CeCP@Pt (32.6%)
CeCP@Pt (52.7%)
70.1%
70.1%
72.3%
73.4%
73.2%
a
The numbers in brackets indicate the weight percentage of Pt.
Fig. 3 EDS spectra for CeCP@Pt with different percentage of Pt (a)
CeCP; (b) CeCP@Pt (5.4%); (c) CeCP@Pt (10%); (d) CeCP@Pt (19.9%);
(
e) CeCP@Pt (32.6%); (f) CeCP@Pt (52.7%). The numbers in brackets
3.2. Catalyzing the oxidation of HMF
indicate the weight percentage of Pt.
ꢀ
The catalytic oxidation of HMF into FDCA in water at 70 C was
carried out with 2 equivalents NaOH at atmospheric pressure.
The substrate conversion and intermediate and nal products
are shown in Fig. 7. During the reaction, the intermediate
products of HMFCA, DFF, and FFCA were monitored by HPLC.
It was found that only HMFCA was detected without any trace of
DFF. It is indicated that the oxidation of HMF was accom-
plished through the pathway with HMFCA as the intermediate
ꢀ
(
Scheme 1). At temperatures lower than 70 C, the FDCA yield
could not be higher than 90%. A high reaction temperature
facilitates the oxidation of HMF into FDCA, for example the
ꢀ
30
ꢀ
FDCA yield 94% was obtained at 100 C for 12 h, 88% at 120 C
31
ꢀ
32
ꢀ
for 10 h, 98% 90 C for 14 h, 95% at 80 C for 24 h, and 100%
at 90 C for 4 h. In this work, the yield of FDCA was 96.2% at
ꢀ
33
ꢀ
7
0 C aer 12 h reaction.
Fig. 4 XPS spectra for CeCP@Pt with different percentage of Pt. The
numbers in brackets indicate the weight percentage of Pt.
To investigate the effect of NaOH amount on the yield of
ꢀ
FDCA, the oxidation of HMF into FDCA was carried out at 70 C
ꢁ1
with a constant ow rate of 30 ml min
for oxygen, and
structures of the prepared CeCP were analyzed using a powder different amounts of anhydrous NaOH were used (Fig. 8). The
XRD technique (Fig. 6b). The sharp peak at 2q ¼ 17.4 indicates optimal amount of NaOH is 2 equivalents. When NaOH was
that the prepared CeCP was crystalline, which was coincident decreased from 2 equivalents to 1 equivalent, the FDCA yield
2
7,28
with previously reports in the literature.
FTIR spectrum for CeCP. The characteristic peaks at 1612–1557 from 2 equivalents to 3 and 4 equivalents, the FDCA yields were
Fig. 6c shows the was reduced from 96.2% to 59.45%. When NaOH was increased
ꢁ
1
and 1435–1373 cm are ascribed to the stretching vibrations reduced from 96.2% to 80.59% and 68.5%, respectively. These
n
assy(–COO–) and nsym(–COO–) of the carboxylate ions, and 531 results demonstrated that the amount of NaOH has a signi-
ꢁ
1
29
cm is due to the Ce–O stretching vibration.
cant effect on the yield of FDCA, an appropriate amount of base
RSC Adv., 2017, 7, 34776–34782 | 34779
This journal is © The Royal Society of Chemistry 2017

View Article Online
RSC Advances
Paper
Fig. 8 Effect of NaOH concentration on the conversion of HMF and
ꢁ1
yield of FDCA. Reaction conditions: 1.0 mg ml CeCP@Pt, oxygen
ꢁ1
ꢀ
flow rate 30 ml min , HMF 50 mM, at 70 C for 12 h.
has the highest catalysis efficiency in water than in other
solvents, in terms of HMF conversion and FDCA yield (Fig. 9).
NaOH can be better dissolved in water than in other solvents.
The acidic chemicals HMFCA, FFCA, and FDCA can be better
neutralized by NaOH in water than in other solvents.
Different amounts of catalysts were used for the oxidation of
ꢁ
1
ꢁ1
HMF, from 1.0 mg ml to 4.0 mg ml . HMF was almost
completely converted for the four samples (Fig. 10). The yield of
FDCA was dependent on the amount of catalyst used. With
ꢁ1
1
.0 mg ml CeCP@Pt, the yield of FDCA was 80.2%. This yield
was increased to 96.2% by using 4.0 mg ml
ꢁ1
CeCP@Pt.
However, the difference in FDCA yield was not so signicant
ꢁ1
ꢁ1
between the catalyst amounts of 1.0 mg ml and 4.0 mg ml
.
2
Fig. 6 (a) N adsorption and desorption isotherms measured at 77 K
for CeCP; (b) XRD pattern of CeCP; (c) FTIR spectrum of CeCP.
The results in Fig. 10 indicate that with relatively low amount of
catalyst, the yield of FDCA is also acceptable.
The effect of the size of Pt particle of CeCP@Pt on the HMF
conversion and product yields is shown in Fig. 11. Both the
HMF conversion and FDCA yield under the catalysis of
CeCP@Pt (4.45 nm) are higher than that catalyzed by CeCP@Pt
with Pt particle size larger than 4.45 nm. The results indicate
that the deposited Pt with a smaller particle size is favorable to
have a higher catalysis efficiency in terms of HMF conversion
ꢁ
1
Fig. 7 Results of HMF oxidation in the water. Reactions: 4 mg ml
ꢁ1
CeMOF@Pt, 50 mM HMF, O
2
flow rate 30 ml min , 2 equivalent
ꢀ
NaOH, reaction temperature 70 C and time 12 h.
(NaOH) is required to obtain the highest yield of FDCA. The
intermediates HMFCA and FFCA and the target product FDCA
are acids. The molecules of these acidic chemicals have a strong
tendency to associate each other and form precipitates. The
added NaOH can neutralize the acidic chemicals, increasing
their solubility in water once generated. Thus, addition of
NaOH can effectively prevent the formation of precipitates on
the surface of CeCP@Pt. The function of NaOH can also explain
that water is better than other solvents, including toluene,
DMSO, DMF, and ethanol, for the oxidation of HMF. CeCP@Pt
Fig. 9 HMF oxidation in various solvents. Reaction conditions: 4.0 mg
ꢁ1
ꢁ1
ꢀ
ml CeCP@Pt, oxygen flow rate 30 ml min , HMF 50 mM, at 70 C for
2 h, 2 equivalents of NaOH.
1
34780 | RSC Adv., 2017, 7, 34776–34782
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
Fig. 10 Oxidation of HMF using different amounts of catalyst. Reac- Fig. 12 Consecutive use of CeCP@Pt for the oxidation of HMF.
ꢁ1
ꢀ
tion conditions: oxygen flow rate 30 ml min , HMF 50 mM, at 70 C
for 12 h, 2 equivalents of NaOH.
water and subsequently ethanol, the catalyst was dried and
reutilized in a new catalysis cycle. Each reuse of CeCP@Pt was
ꢀ
carried out at 70 C for 12 h with 2 equivalents of NaOH. Fig. 12
shows the results of reuse of CeCP@Pt for ve times. The
conversion of HMF was 98.2% aer ve cycles, and the yields of
FDCA were from initial 96.2% to 95.3% of the h cycle. The
results in Fig. 12 demonstrated that the CeCP@Pt catalyst can
be reused at least ve times without signicant loss of activity.
The leaching of Pt from CeCP@Pt was also detected by ICP
atomic emission spectrometric analysis. It was demonstrated
Fig. 11 Effect of the size of Pt particle of CeCP@Pt on the HMF
conversion and product yields.
and FDCA yield. It is possibly because that with smaller Pt
particles, there are more unsaturated active sites on the surface
32
of the catalyst, conferring the catalyst a better activity.
Turnover frequency (TOF) has been commonly used to
compare different catalysts. Herein TOF is dened as the
number of HMF molecules converted per atom of exposed
platinum on the surface per unit time. TOF for the CeCP@Pt
catalysts is listed in Table 3. Obviously, the TOF number is
decreased with the Pt particle size. It is because that with
smaller Pt particles, there are more active sites on the surface of
the catalyst, conferring the catalyst a better activity.
To investigate the reusability of CeCP@Pt, the catalyst was
reused for catalyzing the HMF oxidation. Aer washing with
Table 3 Turnover frequency and Pt dispersion
ꢁ1
Catalysts
TOF (s
)
HMF conversion (%) Pt dispersion
Fig. 13 HMF oxidation in water catalyzed two catalysts. (a) Pt sup-
CeCP@Pt (4.5 nm)
CeCP@Pt (5.2 nm)
CeCP@Pt (8.5 nm)
CeCP@Pt (11.0 nm) 0.075
CeCP@Pt (14.5 nm) 0.071
0.177
0.166
0.153
59.3
43.8
36.0
18.2
15.1
0.168
0.143
0.128
0.118
0.109
ported on CeO
2
that was derived from the CeCP calcination
Pt deposited on commercial CeO
). Reaction conditions: 4 mg ml CeMOF@Pt, 50 mM
cal
(
(
Pt@CeO
Pt@CeO
2
)
(b)
2
com
ꢁ1
2
ꢁ1
HMF, O
2
flow rate 30 ml min , 2 equivalent NaOH, reaction
ꢀ
temperature 70 C and time 12 h.
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 34776–34782 | 34781

View Article Online
RSC Advances
Paper
that Pt leaching was negligible aer ve cycles of reuse of 10 Y. Zhang, Z. Xue, J. Wang, X. Zhao, Y. Deng, W. Zhao and
CeCP@Pt, indicating a good stability of the catalyst. T. Mu, RSC Adv., 2016, 6, 51229–51237.
Fig. 13 shows the results of HMF oxidation in water catalyzed 11 X. Han, L. Geng, Y. Guo, R. Jia, X. Liu, Y. Zhang and Y. Wang,
by other two catalysts: Pt supported on CeO that was derived
Green Chem., 2016, 18, 1597–1604.
2
cal
from the CeCP calcination (Pt@CeO
2
), Pt deposited on 12 L. Prati, A. Villa, M. Schiavoni, S. Campisi and G. M. Veith,
ChemSusChem, 2013, 6, 609–612.
respectively. 13 N. K. Gupta, S. Nishimura, A. Takagaki and K. Ebitani, Green
However, these yields are lower than 96.2% that was achieved by Chem., 2011, 4, 824–827.
CeCP@Pt (Fig. 7). Comparison of the results in Fig. 13 and 7 14 S. E. Davis, B. N. Zope and R. J. Davis, Green Chem., 2012, 1,
com
commercial CeO
and 77.9% for Pt@CeO
2
(Pt@CeO
2
). The FDCA yields were 49.4%
cal
com
2
and Pt@CeO
2
,
demonstrated the advantage of the catalyst CeCP@Pt over the
143–147.
cal
com
catalysts Pt@CeO2 and Pt@CeO2
.
15 D. J. Chadderdon, L. Xin, J. Qi, Y. Qiu, P. Krishna, K. L. More
and W. Z. Li, Green Chem., 2014, 16, 3778–3786.
1
1
1
1
2
6 B. Liu, Y. Ren and Z. Zhang, Green Chem., 2015, 17, 1610–
4
. Conclusions
1617.
7 S. E. Davis, L. R. Houk, E. C. Tamargo, A. K. Datye and
R. J. Davis, Catal. Today, 2011, 160, 55–60.
8 O. Casanova and A. Corma, ChemSusChem, 2009, 2, 1138–
Cerium coordination polymer (CeCP) was synthesized with
,3,5-benzenetricarboxylic acid as the ligand, and platinum
1
nanoparticles were formed in situ on CeCP. The CeCP@Pt
catalysts were utilized for selective oxidation of high concen-
tration HMF into FDCA. The yield of FDCA could reach 96.2%
1144.
9 P. Verdeguer, N. Merat and A. Gaset, J. Mol. Catal., 1993, 85,
327–344.
0 S. Siankevich, G. Savoglidis, Z. Fei, G. Laurenczy,
D. T. L. Alexander, N. Yan and P. J. Dyson, J. Catal., 2014,
ꢀ
aer 12 h of reaction at 70 C in water at atmospheric pressure.
Furthermore, this catalyst can be reused at least ve times
without signicant activity loss. Aer ve recycles, the leaching
of Pt from CeCP@Pt was negligible. This work demonstrated
the advantages of the CeCP@Pt catalyst, including easy prepa-
ration at mild condition, application at relative low temperature
and at atmospheric pressure, catalyzing the oxidation of HMF
with a high concentration, and reuse with a high stability.
315, 67–74.
2
1 W. Q. Niu, D. Wang, G. H. Yang, J. Sun, M. B. Wu,
Y. Yoneyama and N. Tsubaki, Bull. Chem. Soc. Jpn., 2014,
87, 1124–1129.
2
2 P. Vinke, W. V. Poel and V. BikkumH, Studies in Surface
Science and Catalysis, Elsevier, Amsterdam, 1991, vol. 59,
pp. 385–394.
Acknowledgements
2
2
2
2
2
3 R. Sahu and P. L. Dhepe, React. Kinet., Mech. Catal., 2014,
1
12, 173–187.
4 H. A. Ait Rass, N. Essayem and M. Besson, Green Chem.,
013, 15, 2240–2251.
This work was supported by The National Science Foundation of
China (21476023).
2
5 H. A. Ait Rass, N. Essayem and M. Besson, ChemSusChem,
2015, 8, 1206–1217.
6 Z. Z. Miao, T. X. Wu, J. W. Li, T. Yi, Y. B. Zhang and
X. G. Yang, RSC Adv., 2015, 5, 19823–19829.
7 K. Liu, H. You, G. Jia, Y. Zheng, Y. Huang, Y. Song, M. Yang,
L. Zhang and H. Zhang, Cryst. Growth Des., 2010, 10, 790–
References
1
2
S. Alipour, Green Chem., 2016, 18, 4990–4998.
Y. Wang, S. De and N. Yan, Chem. Commun., 2016, 52, 6210–
6
224.
K. Luo, Y. Wang, J. Yu, J. Zhu and Z. Hu, RSC Adv., 2016, 6,
7013–87020.
3
4
797.
8
2
2
3
3
3
3
8 Y. Xiong, S. Chen, F. Ye, L. Su, C. Zhang, S. Shen and S. Zhao,
Y. Jiang, A. J. J. Woortman, G. O. R. A. van Ekenstein,
Chem. Commun., 2015, 51, 4635–4638.
D. M. Petrovi ´c and K. Loos, Biomacromolecules, 2014, 15,
9 S. Maiti, A. Pramanik and S. Mahanty, Chem. Commun., 2014,
2
482–2493.
J. Deng, X. Liu, C. Li, Y. Jiang and J. Zhu, RSC Adv., 2015, 5,
5930–15939.
50, 11717–11720.
5
0 X. Wan, C. Zhou, J. Chen, W. Deng, Q. Zhang, Y. Yang and
Y. Wang, ACS Catal., 2014, 4, 2175–2185.
1 G. Yi, S. P. Teong and Y. Zhang, Green Chem., 2015, 18, 979–
1
6
7
M. E. Davis, Top. Catal., 2015, 58, 405–409.
N. K. Gupta, S. Nishimura, A. Takagaki and K. Ebitani, Green
Chem., 2011, 13, 824–827.
983.
2 C. Zhou, W. Deng, X. Wan, Q. Zhang, Y. Yang and Y. Wang,
ChemCatChem, 2015, 7, 2853–2863.
3 H. Chen, J. Zhou and J. Deng, Polym. Chem., 2016, 7, 125–
8
9
Z. Zhang, J. Zhen, B. Liu, K. Lv and K. Deng, Green Chem.,
2
015, 17, 1308–1317.
S. E. Davis, B. N. Zope and R. J. Davis, Green Chem., 2012, 14,
43–147.
134.
1
34782 | RSC Adv., 2017, 7, 34776–34782
This journal is © The Royal Society of Chemistry 2017