Catalytic performance of functionalized IRMOF-3 for the synthesis of glycerol carbonate from glycerol and urea

Article abstract of DOI:10.1166/jnn.2014.8255

A functionalized isoreticular metal organic framework material, F-IRMOF-3, having a quaternary ammonium group was prepared by fast precipitation and solvothermal method. The synthesized MOFs exhibited good catalytic performance in the synthesis of glycerol carbonate (GC) from glycerol and urea. F-IRMOF-3 having a larger alkyl chain structure and a more nucleophilic counter anion than the synthesized congeners, exhibited better reactivity in the synthesis of GC. The introduction of a ZnO defect into the F-IRMOF-3 structure by fast precipitation was more advantageous for the glycerolysis of urea than the conventional solvothermal method because of the incorporation of acid-base bifunctional active sites by the former method. The effects of reaction parameters such as temperature, reaction time, catalyst loading, and degree of vacuum on the reactivity were also investigated. The F-IRMOF-3 catalyst can be easily recovered and reused without considerable loss of its initial activity. Copyright

Full text of DOI:10.1166/jnn.2014.8255

Article
Journal of
Nanoscience and Nanotechnology
Vol. 14, 4551–4556, 2014
Copyright © 2014 American Scientific Publishers
All rights reserved
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Printed in the United States of America
Catalytic Performance of Functionalized IRMOF-3 for the
Synthesis of Glycerol Carbonate from Glycerol and Urea
Sun-Do Lee, Gyung-Ah Park, Dong-Woo Kim, and Dae-Won Park∗
School of Chemical and Biomolecular Engineering, Pusan National University, Busan 609-735, Republic of Korea
A functionalized isoreticular metal organic framework material, F-IRMOF-3, having a quaternary
ammonium group was prepared by fast precipitation and solvothermal method. The synthesized
MOFs exhibited good catalytic performance in the synthesis of glycerol carbonate (GC) from glycerol
and urea. F-IRMOF-3 having a larger alkyl chain structure and a more nucleophilic counter anion
than the synthesized congeners, exhibited better reactivity in the synthesis of GC. The introduction
of a ZnO defect into the F-IRMOF-3 structure by fast precipitation was more advantageous for the
glycerolysis of urea than the conventional solvothermal method because of the incorporation of
acid-base bifunctional active sites by the former method. The effects of reaction parameters such
as temperature, reaction time, catalyst loading, and degree of vacuum on the reactivity were also
investigated. The F-IRMOF-3 catalyst can be easily recovered and reused without considerable loss
of its initial activity.
Delivered by Publishing Technology to: York University
Keywords: Metal Organic Framework, F-IRMOF-3, Fast Precipitation, Glycerol Carbonate,
IP: 130.63.180.147 On: Wed, 13 Aug 2014 12:31:30
Glycerol, Urea.
Copyright: American Scientific Publishers
1. INTRODUCTION
types of materials. Thus, GC may serve as an inexpensive
source of new polymeric materials for the production of
Utilization of biomass and biodiesels is now well estab-
lished as a green alternative to fossil fuels and for
reducing carbon dioxide emission.1–3 An increase in the
production of biodiesel has resulted in a surplus of glyc-
erol, owing to a sharp decrease in its price. The utilization
of glycerol as a platform chemical represents an opportu-
nity to obtain value-added products from a highly func-
tionalized and cheap raw material, and in recent years,
much research has been dedicated to finding new chem-
ical pathways for transforming glycerol to value-added
products.4–6 In particular, selective oxidation,7ꢀ8 reduction
to 1,3-propanediol,9 and etherification to enable the use of
glycerol as an additive for fuels have been the subject of
extensive research.
Glycerol carbonate (GC), a derivative of glycerol, is a
relatively new and interesting material.10 GC is char-
acterized by low toxicity, good biodegradability, and a
high boiling point; consequently, it has been investi-
gated as a novel component of gas-separation membranes,
polyurethane foams,11 surfactants,12 coatings, paints, and
detergents, and as a nonvolatile reactive solvent for several
polycarbonates and polyurethanes.13
GC is conventionally synthesized via typical protocols
used for other low-molecular-weight organic carbonates.
Transesterification of glycerol can be readily performed
using dimethyl carbonate,14 ethylene carbonate,15 or
propylene carbonate.16 The carbonates utilized during
the transesterification process are typically generated via
phosgene utilization or energy-intensive routes employing
epoxides. However, the reaction of glycerol with phosgene
is limited by the dangerous and environment-unfriendly
nature of phosgene as a reactant. Although there are some
reports addressing the direct carbonylation of glycerol with
carbon dioxide using tin complexes, the applicability of
such processes suffers from serious limitations such as
unfavorable thermodynamic equilibrium and low yields.17
Glycerolysis of urea is an alternative technique that
has been recently described in the literature.18–20 A main
advantage of this method is that the reactant, urea, is read-
ily available and inexpensive. In addition, the generated
ammonia can be easily converted to urea in the presence
of carbon dioxide.
Much effort has been devoted to search for effective cat-
alysts for the glycerolysis of urea. Homogeneous catalysis
∗Author to whom correspondence should be addressed.
J. Nanosci. Nanotechnol. 2014, Vol. 14, No. 6
1533-4880/2014/14/4551/006
doi:10.1166/jnn.2014.8255
4551

Catalytic Performance of Functionalized IRMOF-3 for the Synthesis of Glycerol Carbonate from Glycerol and Urea
employing inorganic salts such as ZnSO4,21 MgSO4,22
Lee et al.
OH
and ZnO23 has been described, and recently, certain het-
HO
erogeneous systems based on these oxides have been
NH2
reported.10ꢀ24 To the best of our knowledge, the use of
metal-organic framework (MOF) materials as catalysts for
the glycerolysis of urea has not yet been published.
H2N
O
H
O
In recent years, MOFs, which are formed by copolymer-
ization of organic molecules with metal ions or metal ion
clusters, have received much attention25–28 owing to their
zeolite-like properties such as high internal surface area
and microporosity, well-ordered porous structures, and
high absorption capacity. Various applications of porous
MOFs, including gas storage,29 separation,30 magnetism,31
and catalysis,32ꢀ33 have been explored. Among these appli-
cations, the use of MOFs as catalysts is particularly
attractive. Zinc aminoterephthalate metal organic frame-
work, IRMOF-3, has recently been found to be an active
heterogeneous catalyst for the Knoevenagel condensation
reaction between benzaldehyde and various activated
methylene compounds.32 An adequate combination of a
Lewis acid and a Lewis base is reportedly favorable for
the synthesis of cyclic carbonates from urea and diols.18
In our previous studies, immobilized ionic liquid cata-
lysts were utilized for the synthesis of GC from glycerol
and ethylene carbonate34 or urea.35 Herein, a functional-
ized MOF (F-IRMOF-3) possessing an electrophilic center
(Zn4O) as well as a nucleophilic center (X−), was devel-
INBu3-BDC
Zn4O
Scheme 1. Activation of urea and glycerol by Zn4O and quaternized
benzene dicarboxylic acid linker of F-IRMOF-3.
IRMOF-1 was also prepared by the same method as used
for IRMOF-3 with the exception that benzene dicarboxylic
acid (BDC) was used in place of 2-aminoterephthalic acid.
Alternatively, IRMOF-1 [Solvo] with high crystallinity was
prepared by the conventional solvothermal crystallization
method. For the synthesis of IRMOF-1 [Solvo], zinc nitrate
hexahydrate (1.5 mmol) and BDC (0.5 mmol) were dis-
solved in DMF (50 mL) and placed inside an autoclave.
The mixture was heated at 373 K for 24 h; the resulting
solid was recovered by filtration, washed twice with DMF,
and finally immersed twice in CH2Cl2 for 12 h to dis-
place DMF from the pores. Tetrabutylammonium iodide
(TBAB) was supplied from Aldrich and used without fur-
ther treatment.
X-ray diffraction patterns were collected on an XPERT
Delivered by Publishing Technology to: York University
oped as a novel one-component heterogeneous catalyst for
PRO X-ray diffractometer using a Cu Kꢂ radiation source
the solvent-free synthesis of GC. TheCodpevyerilgohpet:dAcmatearlyicsat n Scientific Publishers
IP: 130.63.180.147 On: Wed, 13 Aug 2014 12:31:30
(ꢃ = 1ꢄ54056 Å), operating at 40 kV and 45 mA. The
exhibits much higher activity than other heterogeneous cat-
alysts reported in prior publications.
continuous mode wꢀas used for collecting data at a scan-
ning speed of 0.03 /S. FT-IR spectra were acquired with
a Nicolet 560 instrument using KBr pellets. The mor-
phology of F-IRMOF-3 was identified using SEM. The
surface area was calculated from nitrogen adsorption mea-
surements acquired using a BET apparatus (Micromeritics
ASAP 2020). The amount of N+ in F-IRMOF-3 was deter-
mined by ion chromatography (Dionex, ICS-5000).
2. MATERIALS AND METHODS
IRMOF-3 was prepared from triethylamine via fast pre-
cipitation by following a synthesis procedure described
by Huang et al.36 In this method, 6.4 g (64 mmol)
of triethylamine was gradually added to
a N,N-
The synthesis of GC from the reaction of glycerol
with urea, as shown in Scheme 1, was carried out in a
50-mL autoclave reactor equipped with a magnetic stirrer.
For a typical reaction, the F-IRMOF-3 catalyst, glycerol
(50 mmol), and urea (50 mmol) were charged into the
reactor. When the desired temperature was attained, the
reaction was initiated by stirring under vacuum or nitro-
gen. Analysis of the products and reactants was performed
using a gas chromatograph (HP 6890N) equipped with
an FID and a capillary column (HP-5, 5% phenyl methyl
siloxane). Tetraethylene glycol (TEG) was used as an inter-
nal standard. The selectivity toward GC production was
calculated using glycerol as a limiting reactant.
dimethylformamide (DMF) solution (160 mL) containing
4.8 g (16 mmol) of Zn(NO3ꢁ2 ·6H2O and 1.32 g (8 mmol)
of 2-aminoterephthalic acid with stirring at room tempera-
ture for 1.5 h. Next, the solid was filtered and thoroughly
washed with CH2Cl2.
A sample of IRMOF-3 (2.4 g) was activated by guest
exchange with CH2Cl2 (80 mL) for 20 h and was then
ꢀ
filtered and dried under vacuum at 130 C. Next, the acti-
vated sample was suspended in dry DMF (80 mL) and
treated with three equivalents of methyl iodide (CH3I)
at room temperature for 4 d. The resulting powder
was collected by filtration, which was then thorougꢀhly
washed with CH2Cl2 and dried under vacuum at 130 C.
This sample was denoted as F-IRMOF-3(MeI). Various
alkyl halides such as BuCl, BuBr, EtI, and BuI were
also used for the preparation of other F-IRMOF-3 sam-
ples of different alkyl chain lengths with various halide
anions.
3. RESULTS AND DISCUSSION
3.1. Characterization of Catalysts
WXRD results for IRMOF-1, IRMOF-1 [Solvo],
IRMOF-3, and F-IRMOF-3 are presented in Figure 1.
4552
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Lee et al.
Catalytic Performance of Functionalized IRMOF-3 for the Synthesis of Glycerol Carbonate from Glycerol and Urea
110
100
90
(200)
(220)
(400)
80
(600)
70
(a)
60
50
(b)
(c)
(b)
(a)
40
30
100
200
300
400
500
Temperature (ºC)
10
20
30
40
50
2Θ
Figure 3. TGA curves of (a) IRMOF-1 [Solvo], (b) IRMOF-1.
Figure 1. XRD analyses of (a) IRMOF-1, (b) IRMOF-3,
(C) F-IRMOF-3(BuI).
(Fig. 3). The thermograms of IRMOF-1 and IRMOF-1
[Solvo] show two typical weight losses between 25 and
600 ꢀC. The first weight loss to up to 160–180 ꢀC
is attributed to the loss of water (free water molecules
within the pores as well as those coordinated to the
zinc framework) and DMF solvent in the pores. The sec-
The results demonstrate the crystalline nature of all of the
IRMOF samples; the structure of F-IRMOF-3 was well
retained even after functionalization of IRMOF-3 with
an alkyl halide for 4 days. The initial BET surface area
of IRMOF-3 was 248 m2/g, which decreased to 53 m2/g
after functionalization with CH3I.
ꢀ
ond weight loss between 350 and 520 C corresponds to
Figure 2 shows the FT-IR spectra of IRMOF-1, IRMOF-1
[Solvo], IRMOF-3, and F-IRMOF-3. Compared to
the combustion of the organic moiety of the IRMOF-1
structure.38 IRMOF-1, which was prepared by fast pre-
cipitation, exhibited significantly higher weight loss than
IRMOF-1 [Solvo]. Based on the mathematical analysis of
the TGA curves, the ZnO defects were quantified to be
4.7 wt.% for IRMOF-1 and 0.8 wt.% for IRMOF-1 [Solvo].
TGA analyses of F-IRMOF-3(BuI) and F-IRMOF-3(BuI)
[Solvo] are also shown in Figure 4, and the ZnO defects
were estimated to be 19.8 wt.% and 8.1 wt.%, respectively.
Table I shows the quantification of the immobilized qua-
ternary ammonium salt in the various F-IRMOF-3 species
evaluated based on ion chromatography. These catalysts
contained 1.0–4.3 mg of N+/g-cat.
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IRMOF-3, three new peaks were observed at 3010, 1480,
and 945 cm−1 in the case of F-IRMOF-3, which indi-
IP: 130.63.180.147 On: Wed, 13 Aug 2014 12:31:30
Copyright: American Scientific Publishers
cate that CH3I was successfully introduced into the frame-
work of IRMOF-3 resulting in the conversion of –NH2
to a quaternary ammonium salt species. The peaks near
1480 cm−1 in the FT-IR spectrum of F-IRMOF-3 were
assigned to C N stretching vibrations.37 The FT-IR spec-
tra indicate the presence of a quaternary ammonium salt in
F-IRMOF-3.
The thermal stability of the IRMOF-1 catalysts pre-
pared by various methods was evaluated via TGA analysis
110
100
90
(a)
(b)
80
(c)
(d)
70
60
50
Vas(CH)
Vas(C3N+)
(b)
(a)
Vas(COO–)
40
4000
3000
2000
1000
100
200
300
400
500
Wavenumber (cm–1
)
Temperature (ºC)
Figure 2. FT-IR spectra of (a) IRMOF-1 [Solvo], (b) IRMOF-1,
Figure 4. TGA
curves
of (a) F-IRMOF-3(BuI)
[Solvo],
(c) IRMOF-3, (d) F-IRMOF-3(BuI).
(b) F-IRMOF-3(BuI).
J. Nanosci. Nanotechnol. 14, 4551–4556, 2014
4553

Catalytic Performance of Functionalized IRMOF-3 for the Synthesis of Glycerol Carbonate from Glycerol and Urea
Lee et al.
Table I. Amount of N+ on the F-IRMOF-3 catalysts.
Very recently, Xamena et al.33 also reported similar
phenomena with IRMOF-3 samples prepared by various
methods in relation to Knoevenagel condensation reac-
tions. They concluded that in the case of IRMOF-3, and
more specifically IRMOF-3 prepared by fast precipitation,
the presence of Zn–OH and/or ZnO in conjunction with
amino groups may contribute to the final observed activity.
This contribution may occur through an independent cat-
alytic route and/or a synergistic effect in which the amino
groups act as basic sites, while the Zn–OH or ZnO defects
function as acid sites.
In the present case of F-IRMOF-3(BuI), a similar
synergistic process may also occur, accounting for the
good catalytic activity of this catalyst. The acid sites in
F-IRMOF-3(BuI) may arise because of a defective origin
by the inclusion of ZnO particles during the synthesis.
Changing the alkyl chain linker from methyl in
F-IRMOF-3(MeI) to butyl in F-IRMOF-3(BuI) resulted
in an increase in the conversion of glycerol, primarily
because the electron-donating ability of the butyl group
is stronger than that of the methyl group, and hence, the
electron density is concentrated around the center of the
active site in the butyl group. Increasing the bulkiness of
the alkyl chain forces the I− ion away from the cation to a
greater extent, thereby resulting in less electrostatic inter-
action between the anion and the cation.35ꢀ36 These results
F-IRMOF-3
(BuCl)
F-IRMOF-3
(BuBr)
F-IRMOF-3
(BuI)
Catalyst
N+ concentration
(mg N+/g cat.)
4.26
1.93
1.04
3.2. Evaluation of Reactivity of F-IRMOF-3 Catalysts
Table II shows the selectivity, yield, and conversion of
glycerol to GC using the IRMOF-1 and F-IRMOF-3
catalysts having various alkyl chain linkers and counteran-
ions under a vaꢀcuum pressure of 14.7 kPa after 3 h of
reaction at 140 C. A glycerol conversion of 62.9% was
achieved using ZnO only. Compared to IRMOF-1 that does
not possess a functional group in the BDC linker, all of
the F-IRMOF-3 catalysts having a quaternary ammonium
group exhibited higher catalytic activity for the glycerol-
ysis of urea. The quaternary ammonium salt is a typical
ionic liquid, and 51.2% glycerol conversion was achieved
with TBAB itself.
The F-IRMOF-1 catalyst prepared by fast precipitation
exhibited higher GC yield than IRMOF-1 [Solvo] prepared
by the solvothermal method. The difference in the catalytic
activity of the two F-IRMOF-3(BuI) catalysts prepared
via different methods can be related to the difference in
the concentration of defects in both the catalysts. The
amount of excess ZnO residue in the F-IRMOF-3(BuI)
are in good agreement with previous parallel reports on
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39–42
catalysts prepared by fast precipitation is consistent with
IP: 130.63.180.147 On: Wedt,h1e3efAfeucgts2o0f1t4he12al:k3y1l:3ch0ain length.
more defects (19.8 wt.%) than those present in the sample
prepared by the solvothermal method (8.1 wt.%). Note that
the fast precipitation process should lead to less crystalline
samples containing more defects. As shown in Table II,
the ZnO nanoparticles alone showed a GC yield of 43.5%.
The F-IRMOF-3(BuI) catalyst prepared by fast precip-
itation produced 71.0% glycerol conversion and 67.8%
yield of GC, which is also higher than that achieved with
F-IRMOF-3(BuI) [Solvo].
Copyright: American Scientific Publishers
Comparison of the catalytic activities of the MOFs
based on the counter anions revealed that the conversion of
glycerol in the presence of F-IRMOF-3 containing I− was
higher than when Cl− and Br− were present. The effect of
the counteranion on the reactivity is attributed to the nucle-
ophilicity of the anion, where the I− counterion has the
highest nucleophilicity among the three halide anions.43ꢀ44
The effect of reaction time on the synthesis of GC was
studied at 140 ꢀC under a reduced pressure of 14.7 kPa. As
Table II. Reactivity of different catalysts for the synthesis of GC from
glycerol and urea.
100
80
Catalyst
XG (%)
SGC (%)
YGC (%)
ZnO
62.9
64.4
51.0
51.2
58.8
63.7
69.7
71.0
66.6
65.8
65.2
69.2
64.8
60.4
64.4
64.2
78.1
84.8
95.5
95.3
94.8
85.9
43.5
41.7
30.8
33.0
37.7
49.7
59.1
67.8
63.5
62.4
56.1
IRMOF-1
TBABra
60
TBAIb
IRMOF-1 [Solvo]c
F-IRMOF-3(MeI)
F-IRMOF-3(EtI)
F-IRMOF-3(BuI)
F-IRMOF-3(BuBr)
F-IRMOF-3(BuCl)
F-IRMOF-3(BuI) [Solvo]c
40
Conversion
Selectivity
Yield
20
0
0
1
2
3
4
5
6
7
Time (h)
Notes: Reaction conditions: Urea = 50 mmol, Glycerol = 50 mmol, Cat. = 0ꢄ23 g
(5 wt.%), Temp. = 140 ꢀC, Degree of vacuum = 14ꢄ7 kPa, Reaction time = 3 h;
aTetrabutyl ammonium bromide (1 mol% was used); bTetrabutyl ammonium iodide
(0.5 mol% was used); cCatalysts were prepared by the solvothermal method. All
the other IRMOF catalysts were prepared by the fast precipitation method.
Figure 5. Effect of reaction time on the reactivity of F-IRMOF-3(BuI).
Reaction conditions: Urea = 50 mmol, Glycerol = 50 mmol, Cat. = 0ꢄ23 g
(5 wt.%), Temp. = 140 ꢀC, Degree of vacuum = 14ꢄ7 kPa.
4554
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Lee et al.
Catalytic Performance of Functionalized IRMOF-3 for the Synthesis of Glycerol Carbonate from Glycerol and Urea
Table III. Effects of reaction temperature on the synthesis of GC from
Table V. Recycle test of F-IRMOF-3(BuI).
glycerol and urea.
Run
XG (%)
SGC (%)
YGC (%)
Temp. (ꢀC)
XG (%)
SGC (%)
YGC (%)
Fresh
1st
2nd
3rd
71.0
70.0
68.2
66.1
94.5
91.0
87.6
83.7
67.1
63.7
59.7
55.3
100
110
120
130
140
150
160
7.2
10.4
31.8
45.8
71.0
84.2
87.0
20.2
39.3
47.3
66.0
94.5
79.2
27.7
1.5
4.1
15.1
30.2
67.1
66.7
24.1
Notes: Reaction conditions: Urea = 50 mmol, Glycerol = 50 mmol Cat. = 0ꢄ23 g
(5 wt.%), Temp. = 140 ꢀC, Degree of vacuum = 14ꢄ7 kPa, Reaction time = 3 h.
101.3 to 11.3 kPa, given that a high degree of vacuum may
inhibit the reverse reaction whereby GC converts to glyc-
erol and the polymerization of GC and/or glycerol occurs.
Interestingly, removal of ammonia by nitrogen purging at
a flow rate of 150 mL/min was as effective as operation
under a high degree of vacuum.
Notes: Reaction conditions: Urea = 50 mmol, Glycerol = 50 mmol, Cat. = 0ꢄ23 g
(5 wt.%) F-IRMOF-3(BuI), Degree of vacuum = 14ꢄ7 kPa, Reaction time = 3 h.
revealed in Figure 5, the conversion of glycerol increased
as the reaction progressed. At the early stage of the reac-
tion at 0.5 h, the GC selectivity was < 65%, imply-
ing that substantial amounts of the reaction intermediate,
HPC (2,3-dihydroxypropyl carbamate), remained in the
reaction mixture. As the reaction progressed, HPC was
further converted to GC and the selectivity toward GC
production continuously increased up to 91%. The main
by-product (other than HPC) was (2-oxo-1,3-dioxolan-4-
yl)methyl carbamate (ODMC).
Previous studies45 in conjunction with the above find-
ings suggest that the catalysts should possess both Lewis
acidity and basicity to be active for the reaction between
glycerol and urea, and there is a subtle balance between
the acidity and basicity: the Lewis acid group is required
for the activation of the carbonyl group of urea and the
Lewis base functions for the activation of the hydroxyl
groups of glycerol.15ꢀ18ꢀ46 In this regard, for the reaction
of glycerol and urea in the presence of the catalytic sys-
tem F-IRMOF-3(AX), ZnO and the quaternized functional
group could respectively be considered as a Lewis acid
Table III shows the effects of reaction temperature on
the synthesis of GC in the presence of F-IRMOF-3(BuI).
The conversion of glycerol continuouslꢀy increased as the
temperature increased from 100 to 160 C. The selectivity
toward GC production increased with temperature, reach-
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and a Lewis base, as shown in Scheme 1.
IP: 130.63.180.147 On: Wed, 13 Aug 2014 12:31:30
ꢀ
ing a maximum of 94.5% at 140 C; however, the selec-
The role of the quaternized functional group as a Lewis
base in the activation of glycerol was substantiated by
Park et al.45 in which, based on FT-IR and 1H NMR
analysis, strong hydrogen bonding interactions between
the hydroxyl group of glycerol and the chloride anion of
NH4Cl were reported. Fujita et al.23 also suggested the
interaction of ZnO and urea. They reported homogeneous
catalysis of ZnO by forming a complex with urea through
the dissolution of zinc oxide into the mixture of glycerol
and urea.
Copyright: American Scientific Publishers
ꢀ
tivity decreased when the temperature became >150 C,
plausibly because of the transformation of GC to ODMC
or the polymerization of GC and/or glycerol. The for-
mation of polymers from GC or glycerol is reported as
one of the main factors responsible for the low selectivity
toward GC.15
Table IV shows the effects of the degree of vacuum on
the reactivity of the F-IRMOF-3 catalyst. The conversion
of glycerol increased as the degree of vacuum increased
from 101.3 to 11.3 kPa. Application of a high degree
of vacuum could enhance the removal of the generated
ammonia gas, thereby accelerating the forward reaction
of glycerol and urea. The selectivity to GC continuously
increased as the degree of vacuum applied increased from
The stability of the immobilized IL catalyst was evalu-
ated using recycling experiments. In each cycle, the used
catalyst was separated by filtration, washed with methanol
to remove the products adhering to its surface, dried at
room temperature, and then directly reused for the next
run without regeneration. Table V shows the activity of
the reused F-IRMOF-3 catalyst. Upon reusing the conver-
sion of glycerol and the selectivity toward GC decreased
slightly indicating that the catalyst can be reused for up to
three consecutive cycles without significant loss of activity.
Table IV. Effects of degree of vacuum on the synthesis of GC from
glycerol and urea.
Pressure (kPa)a
XG (%)
SGC (%)
YGC (%)
11.3
14.7
28.0
54.6
101.3
N2 purgeb
73.2
71.0
68.7
43.2
35.5
81.3
94.6
94.5
86.1
61.2
58.4
87.8
69.2
67.1
59.2
26.4
20.7
71.4
4. CONCLUSIONS
Glycerolysis of urea using IRMOF-1 and functionalized
F-IRMOF-3 was evaluated herein, illustrating the impor-
tance of the structure and preparation method of the
MOF catalysts on their efficacy. The incorporation of ZnO
defects into the F-IRMOF-3 structure by fast precipitation
Notes: Reaction conditions: Urea = 50 mmol, Glycerol = 50 mmol, Cat. = 0ꢄ23 g
(5 wt.%) F-IRMOF-3(BuI), Temp. = 140 ꢀC, Reaction time = 3 h; aAbsolute pres-
b
sure; N2 purge with a flow rate of 150 mL/min.
J. Nanosci. Nanotechnol. 14, 4551–4556, 2014
4555

Catalytic Performance of Functionalized IRMOF-3 for the Synthesis of Glycerol Carbonate from Glycerol and Urea
Lee et al.
is advantageous for the glycerolysis of urea because of
the introduction of acid-base bifunctional active sites.
F-IRMOF-3 exhibited good catalytic activity even in the
absence of a solvent. ILs with longer alkyl chains and
more nucleophilic counteranions exhibited better reactivity
for the synthesis of GC. High temperature, long reaction
time, and a high degree of vacuum were favorable for the
high conversion of glycerol. The F-IRMOF-3 catalyst can
be easily recovered and reused without considerable loss
of its initial activity.
18. Q. Li, W. Zhang, N. Zhao, W. Wei, and Y. Sun, Catal. Today
115, 111 (2006).
19. M. Okutsu and T. Kitsuki, Method for producing glycerol carbonate,
JP 039347, February (2007).
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Acknowledgments: This study was supported by the
Korean Ministry of Education through National Research
Foundation (2012-001507) and LINC program.
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Received: 22 March 2013. Accepted: 10 June 2013.
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