Effect of anion type of imidazolium based polymer supported ionic liquids on the solvent free synthesis of cycloaddition of CO2 into epoxide

Article abstract of DOI:10.1016/j.cattod.2015.09.048

Catalytic CO₂ fixation into value added products have attracted ample devotion due to the rapid increasing greenhouse gas effect. Especially, by using heterogeneous catalysts, particularly, the designer nature of organic functionality immobiliz

Full text of DOI:10.1016/j.cattod.2015.09.048

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Effect of anion type of imidazolium based polymer supported
ionic liquids on the solvent free synthesis of cycloaddition
of CO2 into epoxide
Arvind H. Jadhava, Gaurav M. Thorata, Kyuyoung Leea, Alan Christian Lima, Hyo Kangb,
Jeong Gil Seoa,∗
a Department of Energy Science and Technology, Myongji University, Myongji-ro 116, Cheoin-gu, Yongin-si, Gyeonggi-do 449-728, South Korea
b Department of Chemical Engineering, Dong-A University, Nakdong-Daero-550, beon-gil, Saha-gu, Busan, South Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 26 June 2015
Received in revised form 1 September 2015
Accepted 22 September 2015
Available online xxx
Catalytic CO2 fixation into value added products have attracted ample devotion due to the rapid increasing
greenhouse gas effect. Especially, by using heterogeneous catalysts, particularly, the designer nature of
organic functionality immobilized on polymer supports has driven significant attention. In this work,
various tailor made imidazolium based ionic liquids (ILs) covalently immobilized on polymeric support
were synthesized successfully (denoted as PSIL) and applied in the cycloaddition of CO2 into epoxides.
Imidazolium (C3H5N2+) and various counter anions such as Cl−, Br−, BF4−, PF6−, and NTf2−, were selected
to construct less coordinated cations with anions in PSILs. In the fixation of CO2 into epoxide, all the
Keywords:
Fixation of CO2
Solvent free reaction
Cyclic carbonate
Ionic liquids
−
prepared PSILs showed efficient catalytic activity, among them 0.1 equiv. of PSIL-NTf2 composed of
−
imidazolium cations and NTf2 anions was the most efficient, showing 100% conversion and 91% yield
of the respective cyclic carbonate under 100 ◦C reaction temperature using 8 bar pressure in 8 h reaction
−
time. This might be due to the least co-ordinated NTf2 anions with imidazolium cations played a vital
role in the ring-opening of epoxide, enhancing the reaction rate and favourable for the worthy yield.
In addition, the effects of various reaction parameters including amount of catalyst, temperature, and
pressure were studied and numbers of substituted cyclic carbonates were prepared. It was found that
PSILs were easily separated from the reaction mixture and reused several times without any significant
loss of catalytic activity. The present solvent free catalytic system was found mild, kinetically fast, and
naturally benign for the coupling of CO2 into epoxide.
© 2015 Elsevier B.V. All rights reserved.
1. Introduction
carbonate or polycarbonates has attracted much attention. The pro-
duction of five-membered cyclic carbonates through the 100% atom
The current existing transportations, power generations, and
manufacturing industries are heavily dependent on fossil-based
carbon sources including petroleum oils and natural gases and
are responsible for the generation of anthropogenic carbon diox-
ide (CO2) during its combustion and their consequences [1,2].
Therefore, many attempts have been considered to minimize the
excessive CO2 by Carbon Capture and Sequestration technologies
[1–5]. In this regard, in last few decades many processes consid-
ered to minimize the additional CO2 in the air [4]. Activation and
consumption of CO2 are still challenging due to its most thermo-
chemically stable nature [5]. However, the catalytic installation of
CO2 into energy-rich substrates, such as epoxides to form cyclic
efficiency coupling of epoxides with CO2 is one of the most promis-
ing way [6]. Cyclic carbonate products and derivatives are widely
used as high-boiling polar and aprotic solvents, main precursors for
synthesis of polymer materials as well as for the synthesis of fine
chemicals intermediates [7–10].
Several homogeneous and heterogeneous catalysts including,
metal oxides [11], metal organic frameworks (MOFs) [12], metal
salts [13,14], transition metal complexes [15], ionic liquids (ILs)
[16], and organic functionalized polymers [17] have been devel-
oped so far for this process. Among these catalysts, heterogeneous
and homogenous ILs have shown predominant catalytic activity
[16–24]. Considering the industrial applications of the coupling
reaction of CO2 with epoxide, efforts should be paid to develop het-
erogeneous ILs, which can be easily separable from the reaction and
reuse in subsequent cycles [25,26]. In last decades, heterogeneous
catalysts such as immobilized ILs on silica, MCM-41, cross-linked
∗
Corresponding author.
E-mail address: jgseo@mju.ac.kr (J.G. Seo).
http://dx.doi.org/10.1016/j.cattod.2015.09.048
0920-5861/© 2015 Elsevier B.V. All rights reserved.
Please cite this article in press as: A.H. Jadhav, et al., Effect of anion type of imidazolium based polymer supported ionic liquids on the
solvent free synthesis of cycloaddition of CO2 into epoxide, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.09.048

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IL polymers, and polymer supported ILs with various functional
groups have been evaluated [8–12].
2.2. Catalyst characterization
Polymer supported ionic liquids (PSILs) are of growing interest
as they combine the unique properties of ILs, such as good ther-
mal stability, low volatility, and non-flammability, with enhanced
mechanical stability, improved process ability. In last decades many
attempts were carried out by utilizing PSILs as catalysts for the
organic transformations [7,9,10,26]. In these cases, only selected
halide anions such as Cl−, Br−, and I−, which are strongly inter-
connected to bulky imidazolium cations have been utilized for the
carbonate formation. It reports that, such kind of ILs fails to pro-
duce good leaving group in carbonate formation reaction. However,
due to the strong interactions of cations and anions of PSILs in
these reported methods need harsh reaction conditions to activate
the leaving group [27–33]. Especially, the acidic proton of imidaz-
olium ILs suffers from overcrowding and not available for opening
of epoxide at the time of formation of carbonate [26,33]. There-
fore, the activities of PSILs for the synthesis of cyclic carbonate are
required to be enhanced in mild reaction condition [30]. Indeed,
it is expected that selection of another anions, which can easily
produce good leaving group to perform the reaction kinetically
fast. To produce such kind of effect in this reaction various anions
with increasing order of molecular size have to study. Therefore,
FT-IR spectra of prepared catalyst were recorded on a Varian
2000 IR spectrometer (Scimitar series) by using the potassium bro-
mide (KBr) disc method. Thermogravimetric analyses (TGA) were
accomplished on Scinco TGA N-100 instrument with heating rate
5 ◦C/min in a nitrogen atmosphere. Elemental analysis and deter-
mination of elements (C, H, and N) was carried out using a Flash
EA 1112 Elemental Analyser manufactured by Thermo Electron
machine. The morphology and surface structure of Merrifield resin
were monitored using the Sigma field emission scanning electron
microscope (FE-SEM) (Carl Zeiss Sigma VP FE-SEM). The stability
of polymeric backbone chain of Merrifield resin was confirmed by
using X-ray diffraction patterns (XRD) obtained using an powder
XRD patterns were recorded on a Rigaku Miniflex (Rigaku Corpora-
tion, Japan) X-ray diffractometer using Ni filtered Cu K␣ radiation
(ꢀ = 1.5406 A) with a 2 min−1 scan speed and a scan range of 5–80◦
at 30 kV and 15 mA. All prepared derivatives of cyclic carbonate
reactions were characterized by 1H NMR and 13C NMR spectroscopy
on Bruker spectrometer 400 and 100 MHz, respectively using CDCl3
as a solvent. The described chemical shifts were in contrast to TMS
as reference for 1H and 13C NMR. All carbonate were also charac-
terized by the FT-IR and GC–MS analysis.
◦
˚
in the present work Cl−, Br−, BF4−, PF6−, and NTf2 anions were
−
selected. In the selected anions electrostatic interaction of anions
with imidazolium cations varies with their molecular structures
and atomic size. It is reported that the electrostatic interactions
between cations and anions are important factor in determining
catalytic performance of the cycloaddition of CO2 into epoxide over
PSILs [33–37].
2.3. Preparation of polymer supported ionic liquids (PSILs)
In 100 mL round bottom flask Merrifield resin (3.5–4.5 mmol/g
Cl− loading % cross linked, 3.2 mmol Cl/g, Aldrich) 3 g, N-methyl
imidazole (10 mmol) in dimethylformamide (DMF) (50 mL) was
added and refluxed for 24 h. On completion, the reaction mix-
ture was cooled to room temperature. It was then filtered and the
obtained residue was washed with DMF, 0.1 mol/L HCl, water and
methanol sequentially followed by drying under reduced pressure
to afford imidazolium-loaded polymer supported IL which des-
ignated as PSIL-Cl−. Further, to obtain various anions containing
PSILs, metathesis reactions were carried out with metal salts such
as KBr, Li (NTf2), NaBF4, and NaPF6 and designated as PSIL-Br−, PSIL-
NTf2−, PSIL-BF4−, and PSIL-PF6−, in acetonitrile respectively. The
samples were dried at 70 ◦C in a dry oven for 12 h. The resulting
PSILs were obtained with good to efficient yield. These prepared
catalysts were further characterized by solid NMR, FTIR and other
modern analysis techniques to determine the anchored ILs with
polymer support.
In this work, we report effect of different anions of tailor made
imidazolium based PSILs for the cycloaddition of CO2 in epoxides
to prepare cyclic carbonates. According to the cations and anions
interactions of ILs, numbers of PSILs with different anions (Cl−,
Br−, BF4−, PF6−, and NTf2−) were synthesized by exchanging the
anions using metathesis reactions. The prime aim of this study is
to develop the least interaction among cations and anions which
help to conduct reaction in mild condition. Therefore, the grow-
ing orders of molecular structures were nominated in anions with
imidazolium cations and established different PSILs to determine
the effect of type of anion on coupling reaction of CO2. The effects
of catalyst amount, reaction temperature, CO2 pressure were also
determined. In addition, several cyclic carbonate were prepared
in optimized reaction condition and recyclability of PSILs were
determined.
2.4. Procedure for cyclic carbonate preparation using PSILs
All cyclic carbonate preparation reactions were performed in
a 50 mL batch reactor, equipped with pressure gauge, mechanical
stirrer and temperature controllable heating mental. A stainless
steel tubular reaction cell with an internal diameter 5.5 cm and
height 7.5 cm was used to carry out the reaction. For a typical cat-
alytic reaction procedure, the epoxide 5 mL, and PSIL (0.1 equiv.)
were loaded into the autoclave without addition of any co-catalyst
or solvent. After sealing the autoclave and purging it with nitrogen
gas, autoclave was placed under constant pressure of carbon diox-
ide and then the reactor was heated to an appropriate temperature
(12 ◦C/min). After completion of the reaction, reactor was cooled
naturally and depressurized. When the reactor showed room tem-
perature, seals have been removed and the reaction mixture was
filtered using Whatman filter paper and liquid product was ana-
lyzed for further study. The product yields were determined by
GC–MS, 1H NMR, 13C NMR, and FT-IR.
2. Experimental
2.1. Materials
Merrifield resin (100–200 mesh), extent of labelling:
3.5–4.5 mmol/g Cl− loading, 1.0% cross-linked (Aldrich), N-
methyl imidazole (99.0%), potassium bromide (KBr) (IR grade)
Potassium bromide (KBr) (99.0%), bis (trifluoromethane) sulfon-
imide lithium salt (99.0%) (Li (NTf2)), sodium tetra fluoroborate
salt (NaBF4) (99.0%), sodium hexafluorophosphate salt (NaPF6)
(99.0%), acetonitrile (99.0%), ethyl acetate (HPLC grade), ethanol
(reagent grade), carbon dioxide gas (99.999%) and all substrate
for the synthesis of carbonate derivatives were purchased from
Sigma Aldrich. Reagents were used as received without further
purification. All solvents were purchased from commercial sources
and were distilled from relevant agents prior to use. Whatman
filter papers were used to separate PSILs catalyst from the reaction
mixture. Ethanol and double distilled water was used throughout
the experiments for washing the catalyst.
2.4.1. 4-(Chloromethyl)-1,3-dioxolan-2-one (Table 3, Entry 1)
Yield 91%; Thick oily liquid; 1H NMR (400 MHz, CDCl3): ı 3.75
(m, 2H), 4.42 (m, H), 4.60 (t, H), 4.96 (m, H) ppm, 13C NMR (100 MHz,
Please cite this article in press as: A.H. Jadhav, et al., Effect of anion type of imidazolium based polymer supported ionic liquids on the
solvent free synthesis of cycloaddition of CO2 into epoxide, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.09.048

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CDCl3): ı: 43.7, 68.1, 73.9, 155.4 ppm. IR range of C O of carbonate:
1788 cm−1
yield of synthesized PSILs. After successfully synthesis of PSILs were
characterized by using fancy modern analytical and spectroscopic
methods.
.
2.4.2. 4-Butyl-1,3-dioxolan-2-one (Table 3, Entry 2)
Yield 82%; oily liquid; 1H NMR (400 MHz, CDCl3): ı 4.19 (d, 2H),
4.21 (m, H), 1.59 (q, 2H), 1.31 (m, 2H), 1.39 (m, 2H), 0.96 (d, 2H) ppm,
13C NMR (100 MHz, CDCl3): ı: 14.6, 17.2, 22.3, 28.2, 35.9, 66.9, 71.2,
3.2. Characterization of PSILs
3.2.1. Fourier transform infrared spectroscopy (FT-IR) analysis of
PSILs
156.8 ppm. IR range of C O of carbonate: 1796 cm−1
.
To approve the immobilization of ILs on polymer support, FT-IR
analysis of pure resin and prepared PSILs catalysts were performed
and results are revealed in Fig. 1. All the prepared catalysts exhib-
2.4.3. 4-(Hydroxymethyl)-1,3-dioxolan-2-one (Table 3, Entry 3)
Yield 91%; colourless liquid; 1H NMR (400 MHz, CDCl3): ı 4.23
(d, 2H), 4.36 (m, H), 3.72 (d, 2H), 3.61 (s, H) ppm; 13C NMR (100 MHz,
CDCl3): ı: 66.2, 68.1, 74.3, 157.3 ppm. IR range of C O of carbonate:
ited four typical infrared bands at 1606, 1566, 1154, and 1085 cm−1
,
which correspond to the band adsorption of the heterocyclic imid-
azolium ring covalently anchored on polymer support [36,37]. On
the other hand, in case of parent pure resin, these peaks were
absent. A typical peak at 1265 cm−1 analogous to the stretching
frequency of CH2Cl functional group disappeared in all obtained
PSILs, indicating complete modification of active sites present on
polymer support by the anchoring of ILs. In addition, all peaks cor-
responding to the styrene backbone chains were present which
means that polymeric backbone chain is stable throughout the
synthesis process. In PSIL-−NTf2−, PSIL-BF4−, and PSIL-PF6−, peaks
1800 cm−1
.
2.4.4. 4-Phenyl-1,3-dioxolan-2-one (Table 3, Entry 4)
Yield 88%; White solid; 1H NMR (400 MHz, CDCl3): ı 4.39 (t, H),
4.78 (t, H), 5.63 (t, H), 7.37 (m, 2H); 7.45 (m, 3H) ppm; 13C NMR
(100 MHz, CDCl3): ı: 77.2, 78.2, 126.3, 128.9, 129.2, 129.7, 136.1,
154.3 ppm. IR range of C O of carbonate: 1804 cm−1
.
2.4.5. 4-(p-tolyl)-1,3-dioxolan-2-one (Table 3, Entry 5)
Yield 91%; White solid; 1H NMR (400 MHz, CDCl3): ı 4.41 (d,
2H), 5.59 (t, H), 7.28 (m, 2H); 7.92 (m, 2H) ppm; 13C NMR (100 MHz,
CDCl3): ı: 64.8, 93.2, 122.6, 128.1, 129.2, 132.2, 154.7 ppm. IR range
corresponding to the N−Tf2 at 1054, 1139 and 1197 cm−1, BF4 at
−
850, 750 cm−1, and PF6 at 750, 740 cm−1 were observed [36–38].
The above results clearly revealed that, magnificently covalent
immobilization of imidazolium based ILs on polymer support with
preservation of parental backbone polymeric structure were suc-
cessfully done.
of C O of carbonate: 1804 cm−1
.
2.4.6. 4,5-Dimethyl-1,3-dioxolan-2-one (Table 3, Entry 6)
Yield 90%; Thick oily liquid; 1H NMR (400 MHz, CDCl3): ı 4.38
(m, 2H), 1.38 (m, 2H) ppm; 13C NMR (100 MHz, CDCl3): ı: 21.7, 74.8,
3.2.2. 13C NMR spectroscopy analysis of PSILs
154.7 ppm. IR range of C O of carbonate: 1791 cm−1
.
The structures of synthesized PSILs were also confirmed by
solid-state 13C NMR spectroscopy and results are summarized in
Fig. 2. As shown in the 13C NMR spectra of all PSILs, a sharp peak
around 25–35 ppm is observed due to the terminal CH3 protons
of substituted imidazolium ring. The sharp peak at around 50 ppm
corresponds to the CH2 bridging moiety between imidazolium and
benzene group present in the polymer support. The representa-
tive peaks of the carbon atoms of imidazolium rings are detected
at range of 122–128, 137, and 142 ppm [39]. In case peaks which
belong to the benzene ring of the backbone chain of polymer sup-
port (aromatic polystyrene skeleton) are probably overlapped with
imidazolium peaks at around 120–140 ppm.
2.4.7. Hexahydrobenzo-1,3 dioxol-2-one (Table 3, Entry 7)
Yield 86%; white solid; 1H NMR (400 MHz, CDCl3): ı 1.41 (m,
2H), 1.59 (m, 2H), 1.92 (t, 4H), 4.68 (t, 2H) ppm; 13C NMR (100 MHz,
CDCl3): ı: 19.0, 26.6, 74.9, 155.6 ppm. IR range of C O of carbonate:
1804 cm−1
.
2.4.8. Tetrahydro-3aH-cyclopenta-1,3-dioxol-2-one (Table 3,
Entry 8)
Yield 78%; white solid; 1H NMR (400 MHz, CDCl3): ı 1.52 (m, 2H),
1.77 (m, 4H), 4.59 (t, 2H) ppm; 13C NMR (100 MHz, CDCl3): ı: 24.3,
34.6, 76.4, 154.7 ppm. IR range of C O of carbonate: 1798 cm−1
.
3.2.3. Thermogravimetric analysis (TGA) of synthesized PSILs
Thermal steadiness would also be significant character for the
practical application of heterogeneous PSILs in various applications,
since different reaction condition, vigorous shaking, drastic acid
base treatment, and filtration may come across in different applica-
tion processes. In this regard, the determination of thermal stability
of synthesized PSILs is prime valuable [25]. In the present study,
thermal stability of various PSILs including pure resin was deter-
mined by TGA and obtained results are accumulated in Fig. 3. In the
TGA curves, especially in pure resin, it can clearly see that decompo-
sition process occurred in single step. The main step of polystyrene
degradation is from 350 to 450 ◦C, which is attributed to the main
chain pyrolysis at about 400 ◦C with the evolution of aromatics from
the degradation of the polystyrene.
2.5. Catalyst (PSILs) separation and regeneration process
After completion of reaction, reaction mixture and catalyst was
separated out by filtration method. The residue containing catalyst
PSILs was washed three times by water and ethanol, correspond-
ingly and dried at 70 ◦C in vacuum oven for 12 h. Consequently,
dried catalyst was reutilized for next attempt of cyclic carbonate
formation reaction of epoxide and CO2.
3. Results and discussion
3.1. Synthesis of polymer supported ionic liquids (PSILs)
Scheme 1 demonstrates the synthetic route for the prepara-
tion of PSILs synthesized and characterized in this study. In brief,
a known amount of polymer support (Merrifield resin) reacted
with N-methyl imidazolium to produce PSIL-Cl−, later on by using
All synthesized PSILs showed two step degradation patterns,
however thermal stability varies depending on the molecular
weight composition of grafted ILs on it. The first decomposition step
is attributed to the grafted ILs and second major decomposition step
is responsible for the polymer backbone chain. The PSIL-Cl− and
PSIL-Br− are less stable compared to pure resin and other synthe-
sized PSILs. In addition, due to its moisture sensitivity slight weight
loss was observed at above 100 ◦C in PSIL-Cl− and PSIL-Br−. How-
ever, since they started to decompose at 195 ◦C and this weight
ion exchange metathesis reaction various other anions (Br−, BF4
,
−
PF6−, and NTf2−) were installed by reacting with various respective
metal salts to prepare PSIL-Br−, PSIL-BF4−, PSIL-PF6−, and PSIL-
NTf2−, respectively. All reactions were takes places smoothly in
mild and eco-friendly reaction conditions which produced high
Please cite this article in press as: A.H. Jadhav, et al., Effect of anion type of imidazolium based polymer supported ionic liquids on the
solvent free synthesis of cycloaddition of CO2 into epoxide, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.09.048

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Scheme 1. Synthesis of various polymer supported ionic liquids containing different anions for the cyclic carbonate synthesis.
Please cite this article in press as: A.H. Jadhav, et al., Effect of anion type of imidazolium based polymer supported ionic liquids on the
solvent free synthesis of cycloaddition of CO2 into epoxide, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.09.048

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5
−
−
degradation of polymer support. These PSIL-BF4 and PSIL-PF6
are moisture stable and could not show any weight loss due to the
moisture. Among all the synthesized supported ILs, PSIL-NTf2− was
found to be the most thermally stable PSILs. The initial decomposi-
tion phase obtained at 381 ◦C. Whereas, decomposition belongs to
the polymer backbone chain obtained at above 430 ◦C. This decom-
position pattern of PSIL-NT−f2− is good agreement with TGA pattern
of pure ILs which has NTf2 moiety as anions [8,25]. It is reported
−
that ILs having NTf2 moiety as anions are thermally stable above
400 ◦C [25]. However, the obtained thermograms of PISLs mani-
fested that synthesized PSILs have sufficient thermal stability for
the various catalytic applications.
3.2.4. FE-SEM analysis of PSILs
An effort was made to examine the morphology of synthesized
PSILs catalyst using FE-SEM. The covalent grafting of ILs bulky unit
on polymeric resin had a noticeable effect on its morphology. Fig. 4
shows that pure resin (a, b) is sphere with highly smooth surface,
whereas the PSIL-Cl− catalyst (c, d) has coarse surface in nature.
However,−the polymeric resin in the other PSILs [PSIL-Br− (e, f),
Fig. 1. FT-IR analysis of synthesized PSILs catalyst for the formation cyclic carbonate.
−
−
PSIL-NTf2 (g, h) PSIL-BF4 (i, j) PSIL-PF6 (k, l)] did not appear
spherical in shape because of some degradation. These kinds of
degradations were already experienced in previous study [36], and
this might be due to large amount of covalently anchored IL unit
make surface tension beyond the critical limit, leading to a fragmen-
tation of spherical particles. However, the fragmented polymeric
beads might enhance catalytic activity because reactants are acces-
sible to surface active sites. It is expected that fragmentation of
polymeric beads can improve the catalytic activity in the fixation
of CO2.
3.2.5. Elemental and XRD analysis of PSILs
To determine the elemental composition of prepared PSILs, ele-
mental analysis was carried out and results are listed in Table 1.
The amount of attached IL was calculated from elemental analy-
sis and it found in the range of catalytic amount and the amount
was ILs 2.0–2.5 mmol/g. In addition to that the amount of nitro-
gen in synthesized PSILs is drastically increased compared to pure
resin, indicating that the imidazole was effectively immobilized
through the covalent bonding. The amount of the attached IL varies
according to the composition of cation and anions present in the
ILs.
Fig. S1 in supporting information shows the X-ray diffraction
patterns of synthesized PSILs in the present study. The XRD patterns
of PSILs have strong diffraction peaks in the range of 2ꢁ = 15–25◦,
rather than this there is no any another peaks which give some
information regarding the supported ILs. The present broad peak
at 2ꢁ = 19 indicates that there is no any harm to the parental
polystyrene backbone chain throughout the ILs covalent grafting
process and preserved crystalline nature [40].
Fig. 2. 13C NMR investigation of PSILs produced for the cycloaddition of CO2 into
epoxide.
100
80
60
40
PSIL-NTf -
PSIL-Cl-
20
0
Pure Resin
PSIL-Br-
3.3. Catalytic activity in fixation of CO2 into epoxide
PSIL-PF -
PSIL-BF -
The catalytic activity of prepared PSILs in the fixation of CO2
into epoxides was initially investigated using styrene oxide (1)
as prototypical substrate in order to prepare final cyclic carbon-
ate product (2), and results are summarized in Table 2. First, we
have conducted the reaction in the presence of 0.5 equiv. of pure
resin which is used as support in this study, and it fails to give
desired product even after prolonged reaction period (48 h) at
100 ◦C (Entries 1, 2). Later on successively, we determined effect
of catalyst by conducting the several reactions in the presence of
synthesized different PSILs as catalysts at 100 ◦C and results are dis-
played in Fig. 5 as well as accumulated in Table 2. PSIL-Cl− which
has combination of imidazolium cations and Cl− anions was able
to obtained 100% conversion but fails to give desired yield of cyclic
0
100
200
300
400
500
600
700
Temperature (oC)
Fig. 3. TGA analysis of prepared various PSILs for the fixation of CO2 into epoxide.
loss is attributed to the weight gained by ILs anchored on poly-
mer support. The second largest weight loss was initiated at 350 ◦C
where the decomposition of polyme−r backbone chain occurred.
−
Furthermore, PSIL-BF4 and PSIL-PF6 showed decomposition in
two steps. The first loss (340 ◦C and 352 ◦C) is attributed to the
loss of grafted ILs and second loss appeared at 430 ◦C is due to the
Please cite this article in press as: A.H. Jadhav, et al., Effect of anion type of imidazolium based polymer supported ionic liquids on the
solvent free synthesis of cycloaddition of CO2 into epoxide, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.09.048

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Fig. 4. Morphology and surface analysis of PSILs.
Table 1
reactions showed 72% and 79% yield of respective carbonate with
88% and 91% conversion of reactants, respectively (Entries 5, 6).
The obtained results of these PSILs also proved that the least co-
ordinated cations and anions are highly beneficial for the protocol.
In case of 0.5 equiv. of PSIL-NTf2−, 100% conversion with 91% yield
for cyclic carbonate was obtained (Entry 7). This outstanding result
Elemental analysis data of prepared various PSILs for the cycloaddition of CO2 into
epoxide.
Sr. No
Components
N (wt.%)
C (wt.%)
H (wt.%)
ILs grafted
(mmol/g)
1
2
3
4
5
6
7a
Pure resin
PSIL-Cl−
PSIL-Br−
0.0582
7.09
7.00
6.69
7.01
6.51
6.32
80.61
71.12
51.35
65.01
66.42
59.87
64.56
6.31
6.70
3.88
5.02
5.34
4.68
4.89
–
−
2.54
2.50
2.19
2.22
2.06
1.92
of PSIL-NTf2 was obtained in a 6 h reaction time under 8 bar
CO2 pressure at 100 ◦C. According to the reported literature, ILs
or PSILs, which consist of Cl− and Br− anions have smaller molec-
ular size and strong interactions with the imidazolium cations,
which needs harsh reaction condition and longer reaction time
for high catalytic activ−ity [17,31,33,40,41]. It is also reveals that,
−
−
PSIL-NTf2
PSIL-BF4−
PSIL-PF6
−
PSIL-NTf2
a
Elemental analysis performed after 8th reuse.
−
anions BF4 and PF6 are also strongly intermingled with the
imidazolium cations, which showed restricted−yield of respective
carbonate in a short reaction period at 100 ◦C (Entry 3). There is
some report which showed the efficient yield of cyclic carbonate
with Cl− anion containing ILs [7,9,10,26]. These reported reactions
are conducted at high temperature (>150 ◦C) and high pressure. Its
specifies that, strong interaction of cations and anions are present
between Cl− anion and imidazolium cations which cannot easily
produced nucleophile at the time of epoxide ring opening and need
harsh reaction condition [17,31,33,40,41]. However, PSIL-Br− was
showed only 61% yield with 100% conversion of reactant, here the
effect of anion (Br−) showed major effect on the yield of cyclic
carbonate (Entry 4).
carbonated product compared with PSIL-NTf2 [33,40,41,43] On
−
the other hand, It is also stated that, NTf2 anions have the least
interaction with imidazolium cations, which enhanced the cat-
alytic activity under mild reaction condition via developing the
nucleophile easily in mild condition [17,33,41]. The obtained activ-
ity results of these PSILs are in good agreement with reported
literature interaction energies between cations and anions, exhib-
ited in the decreasing order of NTf2− > PF6− > BF4− > Br− > Cl−. From
these activity results, it is revealed that least coordinated PSIL-
−
NTf2 is highly suitable for the cycloaddition of CO2 in to epoxide
which showed heights yield in mild condition in this report (Fig. 6)
[17,41–43].
The obtained results of PSIL-Cl− and PSIL-Br− showed major
variations in yield of cyclic carbonate because of atomic radius and
bond dissociation energy of imidazolium cations with respective
anions which plays a crucial role while performing the CO2 coupling
reaction with epoxide [17,26,33]. It is reported that, the atomic
size increases, the interactions of anions and cations decreases.
We believed that, due to this reason, the high molecular size con-
taining anion Br− anion with imidazolium cation obtained high
yield compared with Cl− anions. Furthermore, to dec−rease inter-
From the obtained catalytic activity trend, it exposed that, nucle-
ophile leaving ability of ILs plays a crucial role in the yield of
cyclic carbonate. It can be seen, from the above series of anions
−
used in the present study, NTf2 anion has best leaving ability and
less interaction with cations in PSILs [17]. In addition, it is also
−
reported that NTf2 anions are basic in nature which can strongly
interact with the acidic CO2 molecules which can help for fast colli-
sion of reactants and obtained respective product in mild reaction
condition [17,41]. From these obtained results and collected infor-
mation of reported literature methods, we can say that, instead of
−
actions of cations and anions we have selected BF4 and PF6
PSILs and conducted reactions with PSIL-BF4− and PSIL-PF6−. These
Please cite this article in press as: A.H. Jadhav, et al., Effect of anion type of imidazolium based polymer supported ionic liquids on the
solvent free synthesis of cycloaddition of CO2 into epoxide, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.09.048

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Table 2
Optimization of reaction condition for fixation of CO2 into epoxide to produce cyclic carbonate over PSILsa.
Sr. No.
Catalyst
Catalyst amount (equiv.)
Solvent
Time (h)
Temp. (◦C)
Conv. (%)b
Yieldc (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
DCM
48
48
20
12
12
14
6
6
8
8
8
8
8
8
8
8
8
8
8
100
100
100
100
100
100
100
100
100
100
80
120
140
100
100
100
100
100
100
0
0
100
82
91
88
100
100
100
100
48
100
100
100
100
100
62
0
0
Pure Resin
PSIL-Cl−
PSIL-Br−
0.5
0.5
0.5
0.5
0.5
0.5
0.4
0.2
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
52
61
72
79
91
94
92
88
21
87
68
78
58
76
41
36
81
−
PSIL-BF4−
PSIL-PF6
−
PSIL-NTf2−
PSIL-NTf2−
PSIL-NTf2−
PSIL-NTf2−
PSIL-NTf2−
PSIL-NTf2−
PSIL-NTf2
(bmIm)(NTf2)
−
PSIL-NTf2−
PSIL-NTf2−
PSIL-NTf2−
PSIL-NTf2−
PSIL-NTf2
Acetonitrile
1,4 Dioxane
DMF
76
85
2-Propanol
a
All reactions were carried out on 5 g of styrene oxide with catalyst and 8 bar CO2 pressure.
Conversion were determined by GC.
b
c
Yield refers to the isolated product, characterized by GC–MS, 1H and 13C NMR, and FT-IR.
carbonate synthesis support the above hypothesis. From all these
−
results of catalytic fixation of CO2 in epoxide, PSILs-NTf2 catalyst
has the outstanding catalytic ability due to the strong nucleophilic
nature of anion for the preparation of cyclic carbonate among the
rest of PSILs. Thus, for further study, PSIL-NTf2− catalyst was elected
to determine the effect of mole economy, temperature, solvent, and
CO2 pressure effect.
To determine the effect of catalyst amount, numbers of reac-
tions were conducted with gradual reduction of amount of catalyst.
When 0.4 equiv. amount of catalyst was used for same reaction
at uniform condition, catalyst does not showed any noticeable
effect on yield and conversion (Entry 8). Furthermore, again
reduced the amount of catalyst from 0.4 to 0.2 equiv., catalyst
did not produced efficient yield in same reaction time and this
reaction need slight more reaction time (8 h) for the 100% conver-
sion which display steady effect in the yield of cyclic carbonate
(Entry 9). 0.1 equiv. of catalyst (PSIL-NTf2−) showed 100% conver-
sion and obtained 88% yield in 8 h reaction time in the same reaction
condition (Entry 10). From these obtained outcomes, it can con-
clude that, according to the lowering of amount of catalyst reaction
need longer reaction time. However, it did not showed any nega-
tive impact of the yield of cyclic carbonate and epoxide conversion.
Therefore, considering the mole economy of catalyst 0.1 equiv. of
catalyst amount was nominated for further study.
Fig. 5. Determination of catalytic activity of prepared various PSILs for the cyclic
carbonate formation.
modifying the cations by substitution of bulky groups, if we used
strong nucleophile as anion with methyl imidazolium cation, then
there is no any additional functional group substation required on
cation for the opining of epoxide. Sterically less hindered acidic
proton of imidazolium ring can form interaction with epoxide
which can help to open the epoxide ring by strong nucleophile
[26,33]. Therefore, in the present study obtained reaction results of
Fig. 6. Effect of interaction in between cation and anion in synthesized PSILs on yield of cyclic carbonate formation.
Please cite this article in press as: A.H. Jadhav, et al., Effect of anion type of imidazolium based polymer supported ionic liquids on the
solvent free synthesis of cycloaddition of CO2 into epoxide, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.09.048

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On the other side, we have determined effect of reaction temper-
ature with this protocol for the same reaction. Temperature showed
major effect on the yield and conversion, when we reduced reac-
tion temperature from 100 ◦C to 80 ◦C reaction could not complete
within same reaction time, and reaction showed only 48% con-
version and 21% yield of respective carbonate (Entry 11). In this
case, only small amount of side products together with cyclic car-
bonate were found. They are the isomers of styrene oxide, such
as respective ketone and aldehyde. Isomerization of styrene oxide
is very communal phenomenon while performing the reaction in
pressurized condition, in good agreement with reported litera-
tures [8,9,24]. Higher than 100 ◦C reaction temperature showed
negative effect on selectivity, at 120 ◦C and 140 ◦C, 100% conver-
sion was obtained but the yield of cyclic carbonate was reduced.
Results showed 87% and 68% cyclic carbonate was obtained at
higher temperature respectively with this catalyst (Entries 12, 13).
The obtained lower yield of cyclic carbonate with 100% conversion
at higher temperature was responsible for the partial decomposi-
tion of the cyclic carbonate and negligible side products are found
such as polymerized product of cyclic carbonate [24]. From the lit-
erature, it is found that, the selectivity of the reaction decreases
as the reaction temperature was raised beyond 100–110 ◦C
[24,34].
−
Fig. 7. Determination of effect of pressure on catalytic activity of PSIL-NTf2 for the
formation of cyclic carbonate.
carbonate [32–35], whereas 8 bar reaction pressure showed
tremendous results in which 100% conversion and 88% yield was
obtained. However, higher t−han 8 bar CO2 pressure did not showed
any impact with PSIL-NTf2 on the yield and selectivity of main
cyclic carbonate product at 100 ◦C reaction temperature.
In addition, in order to study the effect of supported phase of ILs
and pure ILs, we have conducted reactions at 100 ◦C using 8 bar CO2
pressure in 8 h reaction time, where 0.1 equiv. of pure IL (without
polymer support) in homogenous phase was used as catalyst. This
reaction was very sluggish and did not give efficient yield of carbon-
ate even if it needs tedious work-up procedure for separation (Entry
14). We believed that active sites in the covalently immobilized ILs
on polymer support are highly responsible for high yield of car-
bonate with supported ILs phase as catalyst which makes process
easier and greener.
Moreover, to determine the effect of solvent on the present reac-
tion using PSIL-NTf2− as catalyst, numbers of reactions were carried
out for fixation of CO2 in to epoxide in various solvents such as
aprotic polar solvents and protic polar solvents in optimized reac-
tion condition. Initially, we performed reactions in aprotic polar
solvents which have low boiling points such as dichloromethane
(DCM) and acetonitrile as well as later on performed reactions in
aprotic solvents with high boiling points such as 1,4-dioxane and
dimethylformamide (DMF). Solvents DCM and acetonitrile were
observed slight active for this protocol and obtained 58% and 76%
yield of cyclic carbonate (Entries 15, 16) due to the high mass
flow addition of CO2 at optimized reaction condition. Whereas sol-
vents 1,4-dioxane and dimethylformamide (DMF) were found very
sluggish and provide only 41 and 36% yield of respective carbon-
ate product (Entries 17, 18). The reaction in polar protic solvent
such as 2-propenol resulted highly effective for this protocol and
obtained highest yield of cyclic carbonate in solvent mediated reac-
tions (81%) (Entry 19). These results suggested that, the protic polar
solvents are quite favourable for the cyclic carbonate formation
by fixation of CO2 in to epoxide, because protic solvents can acti-
vate the epoxide ring via hydrogen bond formation between the
hydroxyl and epoxy groups, this hypothesis suggested by many
researchers in their reports [9,24,34].
Finally to understand the specific role of tailor-made combina-
tion of imidazolium cations with NTf2 anionic moiety, the plausible
reaction mechanism was proposed and shown in Scheme 2. Ini-
tially, the acidic proton of imidazolium ring which is placed in
between two nitrogen atom is less sterically hindered due to
the substation of methyl group is interact towards the oxygen
atom of the epoxide ring [24,29,44,45]. However, based on the
obtained results of PSIL-NTf2−, the cations and anions showed
major influence on the cycloaddition of epoxide with CO2. In case of
imidazolium cations ILs maximum chances is to produce hydrogen
bonding interaction of the IL with epoxide [17,42–45]. In order to
evaluate and determine the presence of hydrogen bonding between
−
an acidic proton of PSIL-NTf2 and epoxide (styrene oxide), a
FTIR analysis were performed (Fig. 8). The FT-IR spectrum of pure
PSIL-NTf2−, demonstrate a vibration band at 3035 and 2966 cm−1
,
which alters broader and less instance and shifted to 3015 and
2922 cm−1 respectively, upon accumulation of an excess of epoxide
at room temperature. These strong bands are assigned to the C
H
(acidic proton and carbon) stretching modes of the imidazolium
ring [17,42–45]. These exhibited frequency shifts of imidazolium
ring can be ascribed to the intermolecular interaction of acidic pro-
ton of imidazolium present in PSIL-NTf2− and epoxide by hydrogen
bonding. Furthermore, some out-of-plane deformation bands in the
finger print region also shift as a significance of the interaction with
epoxide. However, the strongest interaction and large shifting of
peak was observed between the acidic protons of imidazolium ring
with oxygen atom of epoxide.
The coordination of the acidic proton with the oxygen atom
of epoxide resulted in the polarization of C O bond, which mak−e
opening of epoxide easy [29,44,45], while the nucleophilic NTf2
attack from the less hindered ␤-carbon atom of the epoxide fol-
lowed at the same time and opening of epoxide occurred [44,45].
This is the rate-determining step for this coupling reaction. How-
ever, the results acquired in this study designate that both cation
and anion play a significant role. Later on, the oxygen anion inter-
mingled with carbon atom of the CO2 molecule to form the new
intermediate acyclic carbonate. Lastly, the intermediate would b−e
converted into a cyclic carbonate by the elimination of PSIL-NTf2
in the original form. The imidazolium cation with least coordinated
with NTf2 anion plays a vital role in the ring-opening of epoxide.
Furthermore it fascinates the strong interaction of acidic proton
with oxygen which produced rapid opening of epoxide and attach
of the NTf2 nucleophile. These obtained results with this protocol
Subsequently, the effect of CO2 pressure on the yield of carbon-
−
ate by using prepared PSIL-NTf2 catalyst was also determined on
optimized reaction condition. As shown in Fig. 7, the pressure had
very noteworthy effect on the yield and conversion upon the devia-
tion of CO2 pressure. At 100 ◦C reaction temperature, slight change
in CO2 pressure showed major effect. This could be described by
the pressure effect on the concentration of CO2 and epoxide, since
epoxides are in liquid state under the given reaction condition,
and when the reaction was carried out at lower pressure (4 and
6 bar) the lower concentration of CO2 showed the less yield of
Please cite this article in press as: A.H. Jadhav, et al., Effect of anion type of imidazolium based polymer supported ionic liquids on the
solvent free synthesis of cycloaddition of CO2 into epoxide, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.09.048

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Scheme 2. Proposed reaction mechanism of fixation of CO2 in to epoxide over heterogeneous PSILs catalyst for cyclic carbonate formation.
Moreover, cyclic carbonates from cyclohexane and cyclopentene
oxide was also showed restricted yield compared with terminal
epoxides (Table 3, Entries 7, 8).
PSIL- NTf - + StyreneOxide
Pure PSIL-NTf -
3.4. Recyclability of PSILs catalyst
−
To conclude the reusability of the catalyst, PSIL-NTf2 catalyst
was separated and regenerated by −using process as mentioned in
Section 2. Reusability of PSIL-NTf2 catalyst was considered up-
to eight cycles for the synthesis of 2 (Fig. 9(a)). There is no major
damage in the yield and conversion of 2 was determined up-to
six successive cycles and the yield of 2 was maintained almost
consistence during these recycling tests. After six cycles there is
negligible loss in yield a−nd conversion was observed in 7th and
8th cycle with PSIL-NTf2 (Fig. 9(b)). Furthermore, after comple-
tion of recyclability, we also performed FE-SEM and FT-IR analysis
2800
2900
3000
Wavelength (cm
3100
3200
3300
-1
)
−
−
of recovered PSIL-NTf2 catalyst after eight cycles (Fig. 9(c)) and
Fig. 8. Determination of hydrogen boding in catalyst PSIL-NTf2 with epoxide by
FT-IR spectroscopy.
compared physicochemical property with fresh PSIL-NTf2− catalyst
(Fig. 9(d)). FE-SEM results reveals that, there is no any morpho-
−
logical damage was observed in PSIL-NTf2 catalyst even after
designate a synergistic effect on assistant with the cycloaddition
reactions of epoxides into cyclic carbonate [42–45].
eight successive cycles. In addition to that, catalyst could not show
any chemical alteration in covalent immobilized ILs on Merrifield
−
Later on, to determine the adoptability of synthesized PSIL-
NTf2− catalyst tested for the preparation of various cyclic carbonate
by using number of different substituted epoxides and obtained
results are summarized in Table 3. Both types of epoxide sub-
strates (internal and terminal) were reacted respectively in the
presence of PSIL-NTf2−. The selectivity and conversion towards
the cyclic carbonate products were admirable with all substrates
in the optimized reaction condition. In comparison with internal
epoxide, terminal epoxide such as aliphatic and aromatic epoxide
showed higher carbonate yields (Table 3, Entries 1–5). Whereas,
internal epoxide are usually difficult to transform to cyclic car-
bonates due to the higher steric overcrowding nearby the epoxide
ring, which can hinder the nucleophilic attack by the anion. There-
fore, in case butane oxide obtained lowest yield (Table 3, Entry 6).
resin. A FT-IR spectrum of recycled PSIL-NTf2 was almost identi-
−
cal with the FT-IR spectra obtained from fresh PSIL-NTf2 catalyst
(Fig. 9(e)).
Furthermore, to investigate the reason of activity loss, we have
determined the amount of ILs remaining on the recovered catalyst
after 8 cycles by TGA and elemental analysis experiments as shown
in Fig. 10. The TGA curve of recycled catalyst showed almost similar
decomposition pattern with that of fresh catalyst. The fresh catalyst
showed 27.4 wt.% loss in the first step attributed to decomposi-
tion of grafted ILs, whereas the recycled catalyst showed 22.6 wt.%
loss of catalyst after 8 cycles. Accordingly, the amount of grafted
IL decreases from 2.19 mmol to 1.92 after 8 cycles (Table 1). This
means that decrease of catalytic activity from 6th cycle in recy-
−
clability tests of PSIL-NTf2 might be due to the petite leaching of
Please cite this article in press as: A.H. Jadhav, et al., Effect of anion type of imidazolium based polymer supported ionic liquids on the
solvent free synthesis of cycloaddition of CO2 into epoxide, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.09.048

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Table 3
Synthesis of various cyclic carbonate using CO2 and epoxide over PSILsa.
Sr. No
1
Epoxide substrate
Time (h)
6.0
Product
Yieldb (%)
91
Conv. (%)
100
IR range (cm−1
1788
)
2
3
4
6.0
7.0
8
82
91
88
100
100
100
1796
1800
1804
5
6
8
85
78
100
100
1804
1791
8.0
7
8
10.0
12.0
82
78
100
100
1798
1798
a
−
All reactions were carried out on 5 g of substrate with PSIL-NTf2 catalyst without any solvent.
b
Yield refers to the isolated product. Products were characterized by 1H, 13C NMR, IR spectroscopy and GC–MS.
ILs from support material. However the amount of leaching is very
immobilized ILs structural alteration. Currently, progressive future
modifications are going on in ILs structures as well as support mate-
rial in our laboratory to improve selective adsorption of CO2 and
conversion into subsequent catalytic organic transformations.
negligible even after eight successive cycles. Therefore, from above
results, it can be conclude that, synthesized PSILs could be recycled
up to several cycles without losing texture property and covalently
Please cite this article in press as: A.H. Jadhav, et al., Effect of anion type of imidazolium based polymer supported ionic liquids on the
solvent free synthesis of cycloaddition of CO2 into epoxide, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.09.048

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11
−
Fig. 9. Recyclability test of PSIL-NTf2 in coupling reaction of CO2 and epoxide.
cyclic carbonate in solvent free condition. Various PSILs were devel-
oped by keeping constant imidazolium ring and exchanging the
anions with metal salts and determined their anion effect with
imidazolium cation on cycloaddition of CO2 in to epoxide. From
the obtained results, and reported data of interactions energies
between these cations and anions studied in this study showed a
trend NTf2− > PF6− > BF4− > Br− > Cl−, which is also replicated from
100
27.4 Wt. % loss
80
60
40
20
0
Fresh PSIL- NTf2-
100 200
−
their catalytic activity. Especially, least coordinated PSIL-NTf2
0
300
400
500
600
700
Temperature (oC)
(imidazolium cation and NTf2 anion) was found the highly efficient
catalyst for this protocol. The selected catalyst converted various
substituted alkyl and aromatic epoxide in to corresponding cyclic
carbonate in efficient yields with good conversion than the free
IL in mild reaction condition. As a fruitful result, 100% conversion
and 88% cyclic carbonate was obtained using 8 bar CO2 pressure
at 100 ◦C reaction temperature in 8 h reaction time. These synthe-
sized PSILs have many practical advantages such as easy product
separation and purification by simple procedure catalyst recovery
and number of time reuse. In addition, no noticeable changes in cat-
alytic performance were found after being used in 8th cycles. These
aspects are technically striking for considering the use of these cat-
alysts for the eco-friendly fixation of CO2 into epoxide to obtained
cyclic carbonate in high yield.
100
80
60
40
20
0
22.6 Wt. % loss
8th recycled PSIL-NTf2-
100 200
0
300
400
500
600
700
Temperature (oC)
Fig. 10. TGA Analysis of fresh catalyst and 8th recycled catalyst from carbonate
formation reaction.
4. Conclusions
Acknowledgements
In summary, we have constructed tailor-made polymer sup-
ported imidazolium based ILs that acts as highly efficient catalysts
for the cycloaddition of CO2 into epoxide to produce selective
This work was supported by KCRC through the NRF
funded by Ministry of Science, ICT and Future Planning (NRF-
2015M1A8A1048902) and Basic Science Research Program through
Please cite this article in press as: A.H. Jadhav, et al., Effect of anion type of imidazolium based polymer supported ionic liquids on the
solvent free synthesis of cycloaddition of CO2 into epoxide, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.09.048

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the National Research Foundation of Korea (NRF) funded by the
Ministry of Education (Grant number: NRF-2013R1A1A2060638).
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92–98.
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Please cite this article in press as: A.H. Jadhav, et al., Effect of anion type of imidazolium based polymer supported ionic liquids on the
solvent free synthesis of cycloaddition of CO2 into epoxide, Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.09.048