A new porous Zr-containing catalyst with a phenate group: An efficient catalyst for the catalytic transfer hydrogenation of ethyl levulinate to γ-valerolactone

Article abstract of DOI:10.1039/c4gc02104e

Catalytic transfer hydrogenation (CTH) of ethyl levulinate (EL) to γ-valerolactone (GVL) is a very attractive reaction in the field of biomass transformation. In this work, a new porous Zr-containing catalyst with a phenate group in its structure was prepared by the coprecipitation of 4-hydroxybenzoic acid dipotassium salt and ZrOCl₂ (Zr-HBA) in water and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption, and Fourier transform infrared spectroscopy. The Zr-HBA was used as the catalyst for CTH of EL to GVL in the presence of isopropanol, and the effects of temperature, time, and the amount of the catalyst on the reaction were studied. It was found that Zr-HBA was very active for the reaction and a GVL yield of 94.4% could be achieved. Meanwhile, the Zr-HBA could be reused at least five times without a notable decrease in activity and selectivity. The main reason for the high catalytic activity of the Zr-HBA was that the existence of a phenate in the structure of Zr-HBA increased the basicity of the catalyst, which is favourable for the CTH of EL. This journal is

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New porous Zr-containing catalyst with phenate
group: efficient catalyst for catalytic transfer
hydrogenation of ethyl levulinate to γ-
valerolactone
Cite this: DOI:
10.1039/x0xx00000x
Received 00th January 2012,
Accepted 00th January 2012
Jinliang Song*, Lingqiao Wu, Baowen Zhou, Huacong Zhou, Honglei Fan, Yingying Yang,
Qinglei Meng and Buxing Han*
DOI: 10.1039/x0xx00000x
Catalytic transfer hydrogenation (CTH) of ethyl levulinate (EL) to γ-valerolactone (GVL) is a
very attractive reaction in the field of biomass transformation. In this work, a new porous Zr-
containing catalyst with phenate group in its structure was prepared by the coprecipitation of 4-
hydroxybenzoic acid dipotassium salt and ZrOCl2 (Zr-HBA) in water and characterized by
powder X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron
microscopy (TEM), N2 adsorption-desorption, and Fourier transform infrared spectroscopy. The
Zr-HBA was used as the catalyst for CTH of EL to GVL in the presence of isopropanol, and the
effects of temperature, time, and amount of the catalyst on the reaction were studied. It was
found that Zr-HBA was very active for the reaction and a GVL yield of 94.4% could be achieved.
Meanwhile, the Zr-HBA could be reused at least five times without notable decrease in activity
and selectivity. The main reason for the high catalytic activity of the Zr-HBA was that the
existence of phenate in the structure of Zr-HBA increased the basicity of the catalyst, which is
favourable to the CTH of EL.
www.rsc.org/
an alternative to H2 for the GVL production from LA over
supported Au catalysts11 or immobilized Ru catalysts.12
Introduction
With the gradual depletion of fossil resources and the growing
concerns on global climate change, development of efficient
technologies for transformation of biomass into liquid fuels and
valuable chemicals has received much attention.1 Up to now,
various value-added chemicals could be obtained from biomass,
Although good yields of GVL were achieved, the need of noble
metals and/or harsh conditions and the corrodibility of formic
acid still limited the application of this method. Therefore,
development of new efficient methods for the production of
GVL is highly desired.
including
different
alcohols,2
gluconic
acid,3
5-
It is well-known that catalytic transfer hydrogenation
(CTH) reactions offer an attractive alternative to H2 for the
reduction of carbonyl compounds.13 The reduction of carbonyl
group is an important step in the production of GVL from LA
and its esters. Some catalysts have been developed for the CTH
of LA and its esters to produce GVL. For example, Chia and
Dumesic reported that CTH of LA and its esters could be
carried out via Meerwein-Ponndorf-Verley (MPV) reduction
catalyzed by ZrO2 in the presence of secondary alcohols.14 Lin
and co-workers found that CTH of ethyl levulinate (EL) could
proceed over ZrO2 in supercritical ethanol15 or metal
hydroxides in alcohols.16 In addition, Zr-Beta zeolite could be
used as efficient catalysts for CTH of LA and its esters via
MPV reduction for the production of GVL.17 Recently, an
efficient CTH route to convert EL to GVL has been reported by
hydroxymethylfurfural,4 lactic acid,5 2,5-dimethylfuran,6
levulinic acid,7 γ-valerolactone (GVL),8 etc. Among these
chemicals, GVL has been considered as a versatile platform
chemical, which can be used as a fuel additive, solvent for
biomass processing, and a precursor for the production of
alkanes and valuable chemicals.9
Many methods have been reported for the production of
GVL. Generally, GVL is currently produced by hydrogenation
of levulinic acid (LA) and its esters in the presence of various
metal catalysts, such as Pd, Ru, Rh, Pt, Re, Ni, Co, Mo, and
Cu.10 However, these hydrogenation strategies suffer from high
H2 pressure, the use of precious metals, and low catalyst
stability or reactivity, which limit their large-scale application
to a certain degree. Furthermore, formic acid has been used as
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using Raney Ni as the catalyst.18 Although these catalysts were
efficient for the CTH of LA and its esters, there existed some
limitations, including long reaction time,14 high reaction
temperature,15,16 low catalyst stability or reactivity,18 etc.
Therefore, it is very attractive to develop more efficient and
stable catalysts for CTH reaction of LA and its esters to
produce GVL.
It has been reported that the carboxylate and phenate on
benzene ring could be coordinated with metal ions.19 It was also
proved that the existence of phenate could increase the basicity
of the synthesized catalyst.19c Meanwhile, increasing the
basicity of the catalyst could enhance the activity of CTH
reaction.14 Herein, we synthesized a new porous Zr-containing
catalyst (Zr-HBA hereafter) using 4-hydroxybenzoic acid
dipotassium salt (HBADPS, Scheme 1) and ZrOCl2 in water for
the CTH reaction of EL to produce GVL using isopropanol as
the hydrogen source and solvent. The reason for using EL as
reactant instead of LA was that the catalyst prepared was
sensitive to acid. At the same time, the production of ester
levulinate from lignocellulose has higher yield and the product
separation is easier.20 The as-prepared catalyst contained both
carboxylates and phenates, leading to high active, selective and
stable of the Zr-HBA for the reaction. To the best of our
knowledge, this is the first report for the synthesis of the novel
porous Zr-containing catalyst (Zr-HBA) and its application to
catalyze the CTH reaction of EL to produce GVL.
Fig. 1. Powder XRD pattern (a), SEM image (b) and TEM
image (c) of the as-prepared Zr-HBA.
Fourier transform-infrared (FT-IR) technique was also
used to characterize the as-prepared catalyst (Fig. 2). The FT-
IR spectrum of the as-prepared catalyst displayed the
characteristic asymmetric (1624cm-1, 1556 cm-1) and symmetric
vibration (1445 cm-1, 1379 cm-1) of carboxylate anions. In
comparison with the FT-IR spectrum of HBADPS, the
wavenumber difference of asymmetric and symmetric vibration
of carboxylate anions is narrowed.21 This indicated that
carboxylate groups were coordinated to Zr4+ ions. The observed
strong peaks at about 3450 cm-1 should be assigned to the
adsorbed water.
Scheme 1. The structure of HBADPS and Zr-HBA.
Results and discussion
Catalyst characterization
The synthetic procedure for Zr-HBA was presented in detail in
the Experimental section. The powder XRD pattern of the
synthesized catalyst is shown in Fig. 1a. It could be seen that
the catalyst had no X-ray crystal structure. In the structure of
HBADPS, there are only one strong coordination group
(carboxylate) and one weak coordination group (phenate). Less
strong coordination groups resulted in the lower degree of
crystallinity for the as-prepared catalyst. Meanwhile, the XRD
pattern showed one broad diffraction peak, indicating that the
obtained catalyst was amorphous. The scanning electron
microscopy (SEM) and transmission electron microscopy
(TEM) demonstrated that the catalyst had no uniform shape
(Fig. 1b, 1c and Fig. S4).
Fig. 2. FT-IR spectra of Zr-HBA and HBADPS.
2
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The textural parameters of the synthesized Zr-HBA were Table S1). Thus, we can deduce that the phenate could increase
investigated by N2 adsorption-desorption method after the the reaction activity. Furthermore, it has also been reported that
o
sample was degassed at 100 C for 24 hours. It can be seen that Sn-containing compounds could catalyze the CTH reaction. In
the N2 adsorption-desorption isotherm of the catalyst exhibited this work, we also synthesized Sn-HBA for comparison and
a type IV mode, showing pore condensation with pronounced found that Zr-HBA had better catalytic activity than Sn-HBA
adsorption-desorption hysteresis (Fig. 3). The result in Fig. 3 (entry 7, Table 1), which was consistent with the results
indicates that the Zr-HBA prepared was porous. The porosity of obtained from the catalytic systems of zeolites.17 Furthermore,
the catalyst could result from the gaps between the aggregated it was also demonstrated that the Zr-HBA prepared in our work
particles (shown in Fig. 1c). The average pore diameter, had better performance than other Zr-based catalysts reported in
Brunauer-Emmett-Teller (BET) surface area, and pore volume the literature when the reaction was conducted under
calculated from the N2 adsorption-desorption were 8.0 nm, 87.3 comparable reaction conditions (entries 8-13, Table 1).
m2g-1, and 0.21 cm3g-1, respectively. The low BET of the as-
prepared catalyst was due to use of water as the solvent.22 The
amount of micropores in the Zr-HBA was very limited, which
can be known from the fact that the Zr-HBA had a very low N2
adsorption capacity when the relative pressure (P/P0) was as
low as 0.01 in the N2 adsorption-desorption isotherm (Fig. 3).23
Table 1. CTH reaction of EL in isopropanol catalyzed by
different catalysts.a
GVL
Tem.
(oC)b
Time
(h)
Con.
(%)c
Entry
Catalyst
yield
(%)c
0
Sel.d
1
2
3
None
HBADPS
ZrOCl2
ZrO2
150
150
150
150
150
150
150
150
150
200
200
120
120
4
4
4
4
4
4
4
4
6
1
1
4
4
0
---
2.9
62.1
84.7
24.7
62.9
100
43.1
100
100
100
93.6
82.1
36.6
1.8
43.7
21.3
15.9
94.4
30.7
95.9
92
96.8
88.5
50.1
12.2
51.6
86.2
25.3
94.4
71.2
95.9
92
96.8
94.5
61.0
33.3
4
5
6
7
8f
9f,g
10
11h
12
13i
Zr-BDCe
Zr-HBA
Sn-HBA
Zr-HBA
Zr-Beta
Zr-HBA
Zr(OH)4
Zr-HBA
ZrO2
Fig.3. N2 adsorption-desorption isotherm for Zr-HBA.
aReaction conditions: a stainless reactor of 22 mL; catalyst 0.2
g; EL 1 mmol; isopropanol 100 mmol. bTem.=Temperature.
cConversion (Con.) and GVL yield were determined by GC.
dSel.=Selectivity and the other products were mainly isopropyl
levulinate produced by transesterification of EL with
Catalytic performance of different catalysts
The activity and selectivity of various catalysts were tested for
the CTH reaction of EL to produce GVL using isopropanol as
the hydrogen source and solvent, and the results are given in
Table 1. The reaction did not occur in the absence of the
catalyst (entry 1, Table 1). When HBADPS was used as the
catalyst, the main product was isopropyl levulinate generated
from transesterification of EL with isopropanol (entry 2, Table
1). Although GVL could be produced with moderate yields
when Zr-containing compounds, such as ZrOCl2, ZrO2 and Zr-
BDC, were used as the catalysts, the selectivity for GVL was
not satisfactory because large amounts of isopropyl levulinate
were produced as by-products in the reaction process (entries 3-
5, Table 1). Surprisingly, the reaction proceeded with much
higher conversion and selectivity when the as-prepared Zr-
HBA was used as the catalyst (entry 6, Table 1). Less
transesterification product was formed over Zr-HBA, which
may result mainly from the high activity of Zr-HBA for CTH
reaction of EL and isopropyl levulinate. The main reason for
the excellent performance was probably that the existence of
carboxylate and phenate in the structure of Zr-HBA increased
the basicity of the catalyst,19c which has been proved by that
increasing the basicity could increase the yield and selectivity
of the CTH reaction.14 In order to prove the effect of phenate,
we synthesized a Zr-containing metal-organic framework (Zr-
BDC), which was formed by the coordination between Zr4+ and
benzene-1,4-dicarboxylic acid (BDC) in the absence of phenate.
The result showed that the Zr-BDC had lower activity than the
Zr-HBA (entry 5, Table 1) although Zr-BDC had similar pore
volume and higher surface area than the Zr-HBA (Fig. S1 and
e
isopropanol. Zr-BDC was obtained from ZrCl4 and BDC in
f
N,N-dimethylformamide. The hydrogen donor was 2-butanol.
gThe data was obtained from reference 17b. hThe data was
i
obtained from reference 16. The data was obtained from
reference 14.
Effect of catalyst amount
Effect of the amount of Zr-HBA on the CTH reaction of EL
o
was studied in isopropanol at 150 C with a reaction time of 4 h,
and the results are shown in Fig. 4. It can be known from the
figure that the conversion of EL and the yield and selectivity of
GVL increased with the amount of the catalyst at the beginning.
100% conversion of EL and 94.4% yield and selectivity of
GVL were obtained as the catalyst amount was 200 mg. Our
experiments indicated that the by-products were mainly
isopropyl levulinate produced from transesterification of EL
with isopropanol in the reaction process, which could also be
converted into GVL with a lower reaction rate under a similar
process with EL. Therefore, 200 mg of the catalyst would be an
appropriate amount at the reaction conditions.
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Fig. 4. Effect of Zr-HBA amount. Reaction conditions: EL 1 Fig. 6. Influence of reaction time. Reaction conditions: EL 1
mmol; isopropanol 100 mmol; reaction temperature 150 oC; mmol; isopropanol 100 mmol; Zr-HBA 200 mg; reaction
reaction time 4 h.
temperature 150 oC.
Influence of reaction temperature
The leaching and heterogeneity of the catalyst
Fig. 5 demonstrates the influence of reaction temperature on the To study the leaching of the catalytic species and heterogeneity
o
CTH reaction of EL in the range of 120-160 C with a reaction of the catalysis, the effect of reaction time on the CTH reaction
time of 4 h. It can be seen that the reaction temperature affected of EL in the presence of isopropanol catalyzed by Zr-HBA at
o
the reaction significantly. The conversion of EL and the yield 150 C was compared with that of another reaction where the
and selectivity of GVL increased with increasing temperature, reaction was stopped after 2 h, and then continued after filtering
and was nearly independent of temperature after 150 oC.
out the solid catalyst. The results are shown in Fig.7. It is
obvious that there was no further increase in the product yield
after the solid catalyst was removed, confirming that the active
site in Zr-HBA was not soluble in the reaction mixture and the
reaction was proceeded with heterogeneous catalysis. The
thermogravimetric analysis in this work indicated that the
decomposition temperature of the as-prepared catalyst was350
oC, which was much higher than the reaction temperature.
Fig. 5. Influence of reaction temperature. Reaction conditions:
EL 1 mmol; isopropanol100 mmol; Zr-HBA 200 mg; reaction
time 4 h.
Influence of reaction time
The influence of reaction time was investigated at the reaction
temperature of 150 C in the presence of 200 mg Zr-HBA (Fig.
o
Fig. 7. (a) Time-yield plots for the CTH reaction of EL
catalysed by Zr-HBA. Reaction conditions: EL 1 mmol;
isopropanol 100 mmol; Zr-HBA 200 mg; reaction time 4 h;
reaction temperature, 150 oC. (b) The line shows the GVL
yields upon removing the solid catalyst after 2 h and continued
up to 10 h.
6). In a relatively short reaction time, the conversion of EL was
incomplete and the selectivity was low with isopropyl
levulinate produced. It is shown in Fig. 6 that the conversion of
EL and the yield and selectivity of GVL increased with
increasing reaction time from 0 to 4 h. Full conversion of EL
and 94.4% yield of GVL could be achieved with a reaction time
of 4 h. No obvious increase in the yield and selectivity of GVL
was observed with prolonged reaction time because nearly all
of the EL could be converted in 4 h.
Reusability of the catalyst
Experiments were also carried out to examine the reusability of
the Zr-HBA. In each cycle, Zr-HBA was recovered by
centrifugation. Then, the catalyst was reused directly after
washed by ethyl ether and dried for the next run. The
conversion of EL and the yield and selectivity of GVL for the
4
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five repeated runs are shown in Fig. 8. There was no notable
decrease in the conversion, yield and selectivity after five
cycles, indicating that the catalyst was very stable. The Zr-HBA
recovered after reused five times was characterized by FT-IR
(Fig. 9a), XRD (Fig. 9b) and SEM (Fig. 9c). It can be known
that the properties of the Zr-HBA were not changed after being
used. These results provided further evidences that the catalyst
was stable in our reaction system.
Mechanism
Acidic and basic sites in the catalyst are crucial for CTH
reaction.13 Through the characterizations of NH3-TPD (Fig. S2)
and CO2-TPD (Fig. S3) techniques, we can conclude that there
were both acid sites and basic sites on the Zr-HBA. The acid
sites were mainly originated from the Zr4+ and the basic sites
resulted mainly from O2- in the carboxylate and phenate
groups.15,19c Based on the results above and some related
knowledge in the literatures,13a,15 we proposed a possible
mechanism of CTH reaction of EL to GVL catalyzed by Zr-
HBA (Scheme 2). Firstly, the interaction of isopropanol with
the acid-base sites (Zr4+-O2-) on Zr-HBA leads to its
dissociation to the corresponding alkoxide. At the same time,
the carbonyl group in EL can be adsorbed and activated by
Zr4+-O2- on Zr-HBA. Then, hydrogen transfer takes place
between the dissociated alcohol and the activated EL via a
concerted process involving a six-link intermediate to form
ethyl 4-hydroxypentanoate (4-HPE). Finally, the 4-HPE is
converted
into
GVL
through
an
intramolecular
transesterification. Meanwhile, isopropanol is converted into
acetone after losing two hydrogen atoms. In the reaction
process, the by-product isopropyl levulinate can be formed by
transesterification of EL with isopropanol. Similarly, the
isopropyl levulinate can be transformed into GVL by CTH
reaction with the similar way like EL.
Fig. 8. Reusability of the catalyst. Reaction conditions: EL 1
mmol; isopropanol 100 mmol; Zr-HBA 200 mg; reaction
temperature 150 oC; reaction time 4 h.
Scheme 2. Possible mechanism for the transformation of EL to
produce GVL catalyzed by Zr-HBA via CTH reaction.
Conclusions
In summary, a new porous Zr-containing catalyst (Zr-HBA)
with the existence of phenate group has been synthesized and
used as the heterogeneous catalyst for the CTH reaction of EL
to produce GVL in the presence of isopropanol. Full conversion
of EL and GVL yield of 94.4% can be obtained under the
optimal conditions. Catalytic activity of the Zr-HBA is very
high for the reaction, mainly because the existence of phenate
in the Zr-HBA structure increases the basicity of the catalyst,
which was beneficial for the CTH reaction of EL. The catalyst
can be reused at least five times without reducing the activity
and selectivity. We believe that the catalyst has potential
applications in the synthesis of GVL from CTH reaction of EL.
Fig. 9. The characterization of the catalyst Zr-HBA after reused
five times. FT-IR spectrum (a), XRD pattern (b), and SEM
image (c).
Experimental section
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The authors thank the National Natural Science Foundation of
China (21173234, 21133009, U1232203, 21021003), and the
Chinese Academy of Sciences (KJCX2.YW.H30).
Ethyl levulinate (98%), γ-valerolactone (98%), terephthalic acid
(99%) and isopropanol (99.5%) were provided by J&K
Scientific Ltd. ZrOCl2·8H2O (AR), ZrO2 (AR) and SnCl4·5H2O
(AR) were purchased from Beijing Chemical Reagent
Company. 4-Hydroxybenzoic acid dipotassium salt (99.9%)
was obtained from Beijing Institute of Chemical Reagent.
Notes and references
Beijing National Laboratory for Molecular Sciences, CAS Key
Laboratory of Colloid and Interface and Chemical Thermodynamics,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190,
Preparation and characterization of Zr-HBA
China.
Tel/fax:
86-10-62562821.
E-mail:
songjl@iccas.ac.cn,
In a typical procedure, ZrOCl2·8H2O (0.1 mol) and 4-
hydroxybenzoic acid dipotassium salt (0.2 mol) were dissolved
in water (250 mL), respectively. Then, the solution of 4-
hydroxybenzoic acid dipotassium salt was dropwise added into
the solution of ZrOCl2·8H2O with a time of 2 h. After that, the
mixture was continued stirred for 6 h. The white precipitate was
separated by filtration, thoroughly washed with H2O and
ethanol, and dried at 80 oC under vacuum for 12 h.
hanbx@iccas.ac.cn.
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See DOI:
10.1039/b000000x/
1
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The scanning electron microscopy (SEM) measurements
were performed on a Hitachi S-4800 Scanning Electron
Microscope operated at 15 kV. The samples were spray-coated
with a thin layer of platinum before observation. The
transmission electron microscopy (TEM) images were obtained
using a TEM JeoL-1011 with an accelerating voltage of 120 kV.
The sample was dispersed in ethanol with the aid of sonication
and dropped on an amorphous carbon film, supported on a
copper grid, for the TEM analysis. Powder XRD patterns were
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Catalytic reaction
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In a typical experiment, EL (1 mmol), isopropanol (100 mmol)
and catalyst (200 mg) were charged into a stainless reactor of
22 mL equipped with a magnetic stirrer, which was similar to
that used previously.24 After sealed, the reaction mixture was
stirred at a known temperature for the desired time. After the
reaction, the products were analyzed quantitatively by a gas
chromatography (GC, Agilent 6820) using ethylbenzene as the
internal standard, and identification of the products was done
by GC-MS (Shimadzu QP2010).The yield of GVL was
calculated by the following equation:
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o es of formed
ie d (mo %)=
100%
o es of used
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, 3308.
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catalyst was recovered by centrifugation, washed using ethyl
ether. After drying under vacuum at 80 C for 12 h, the catalyst
o
was reused for the next run.
Acknowledgements
6
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

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DOI: 10.1039/C4GC02104E
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Journal Name
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This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 7

Green Chemistry
Page 8 of 13
View Article Online
DOI: 10.1039/C4GC02104E
Graphical abstract
New porous Zrꢀcontaining catalyst (ZrꢀHBA) could be used as heterogeneous catalyst
for efficient catalytic transfer hydrogenation of ethyl levulinate to γꢀvalerolactone.

Page 9 of 13
Green Chemistry
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DOI: 10.1039/C4GC02104E
Supplementary Information for
New porous Zrꢀcontaining catalyst with phenate group: efficient catalyst
for catalytic transfer hydrogenation of ethyl levulinate to γꢀvalerolactone
Jinliang Song*, Lingqiao Wu, Baowen Zhou, Huacong Zhou, Honglei Fan, Yingying
Yang, Qinglei Meng and Buxing Han*
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Colloid and
Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of
Sciences, Beijing 100190, China. Tel/fax: 86-10-62562821. E-mail: songjl@iccas.ac.cn,
hanbx@iccas.ac.cn.
Table of Contents
1. Table S1. Physical properties of ZrꢀBDC and ZrꢀHBA..…………….S2
2. Fig. S1. N2 adsorptionꢀdesorption isotherm for ZrꢀBDC…………….S2
3. Fig. S2. NH3ꢀTPD spectra of ZrꢀHBA…………………………………S3
4. Fig. S3. CO2ꢀTPD spectra of ZrꢀHBA…………………………………S4
5. Fig. S4. TEM image of the asꢀprepared ZrꢀHBA……………………..S5
S1

Green Chemistry
Page 10 of 13
View Article Online
DOI: 10.1039/C4GC02104E
1. Table S1. Physical properties of Zr-BDC and Zr-HBA.
Samplea BET surface area (m2g-1)b
Pore volume
(cm3g-1)c
0.20
Pore diameter
(nm)d
4.5
Zr-BDC
Zr-HBA
257.9
87.3
0.21
8.0
aThe sample was degassed at 100 °C for 24 h. bSurface Area based on multipoint
BET method. cPore volume and pore diameter based on BJH method.
2. Fig. S1
150
100
50
Adsorption
Desorption
0
0.0
0.2
0.4
0.6
0.8
1.0
Relative pressure (P/P )
0
Fig. S1. N2 adsorption-desorption isotherm for Zr-BDC.
S2

Page 11 of 13
Green Chemistry
View Article Online
DOI: 10.1039/C4GC02104E
3. Fig. S2
1.35
1.30
1.25
1.20
1.15
100 150 200 250 300 350
o
Temperature ( C)
Fig. S2. NH3-TPD spectra of Zr-HBA. Temperature-programmed
desorption of ammonia (NH3-TPD) was performed on Micromeritics’
AutoChem 2950 HP Chemisorption Analyzer. The catalysts were charged
into the quartz reactor, and the temperature was increased from room
o
o
temperature to 150 C over 1 h at a rate of 10 C min-1 under a flow of He
(50 cm3min-1), and then the temperature was decreased to 50 C. NH3/He
o
(10/90, 50 cm3min-1) was pulsed into the reactor at 50 oC under a flow of He
(10 cm3min-1) until the acid sites were saturated with NH3. The adsorbed
NH3 was removed by a flow of He (50 cm3min-1). When the baseline was
stable, the temperature was increased from 50 oC to 350 oC at a rate of 10 oC
min-1. The NH3-TPD curve of the Zr-HBA was shown in Fig. S2. Due to the
o
decomposition temperature of the as-prepared catalyst was about 350 C,
the test could conduct under the temperature lower than 350 oC. It could be
found that there existed large amounts of acid sites, which were mainly
resulted from Zr4+ (RSC Adv., 2013, 3, 10277).
S3

Green Chemistry
Page 12 of 13
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DOI: 10.1039/C4GC02104E
4. Fig. S3
1.35
1.30
1.25
1.20
1.15
1.10
100 150 200 250 300 350
o
Temperature ( C)
Fig. S3. CO2-TPD spectra of Zr-HBA. Temperature-programmed
desorption of carbon dioxide (CO2-TPD) was performed on Micromeritics’
AutoChem 2950 HP Chemisorption Analyzer. The catalysts were charged
into the quartz reactor, and the temperature was increased from room
o
o
temperature to 150 C over 1 h at a rate of 10 C min-1 under a flow of He
(50 cm3min-1), and then the temperature was decreased to 50 C. CO2 (50
cm3min-1) was pulsed into the reactor at 50 C under a flow of He (10
o
o
cm3min-1) until the acid sites were saturated with CO2. The adsorbed CO2
was removed by a flow of He (50 cm3min-1). When the baseline was stable,
the temperature was increased from 50 oC to 350 oC at a rate of 10 oC min-1.
The CO2-TPD curve of the Zr-HBA was shown in Fig. S3. Due to the
o
decomposition temperature of the as-prepared catalyst was about 350 C,
the test could conduct under the temperature lower than 350 oC. It could be
found that there existed large amounts of basic sites, which were mainly
resulted from O2- in the carboxylate and phenate groups (RSC Adv., 2013, 3,
10277).
S4

Page 13 of 13
Green Chemistry
View Article Online
DOI: 10.1039/C4GC02104E
5. Fig. S4
Fig. S4. TEM image of the as-prepared Zr-HBA.
S5