A Copper Metal–Organic Hydrogel as a Catalyst for SO2 and CO2 Fixation under Ambient Conditions

Article abstract of DOI:10.1002/ejic.201900594

A copper metal–organic hydrogel (MOG) has been synthesized using an amino acid-based ligand, Na₂HL {H₃L = 2-{(3,5-di-tert-butyl-2-hydroxybenzyl)amino succinic acid} as a gelator. The metallohydrogel exhibits pH-responsive nature as well as chemical responsiveness. Besides, it shows rapid thixotropic behavior when external mechanical forces are applied. The metal–organic hydrogel can be used as a heterogeneous catalyst for the reaction of SO₂ and CO₂ with epoxides to produce cyclic 1,3,2-dioxathiolane-2-oxides and carbonates, respectively. The conversions were found to be dependent on the size and type of the side chain of the epoxides.

Full text of DOI:10.1002/ejic.201900594

A Journal of
Accepted Article
Title: A copper metal-organic hydrogel as a catalyst for SO2 and CO2
fixation under ambient condition
Authors: Chandan Kumar Karan and Manish Bhattacharjee
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Link to VoR: http://dx.doi.org/10.1002/ejic.201900594

10.1002/ejic.201900594
European Journal of Inorganic Chemistry
FULL PAPER
A copper metal-organic hydrogel as a catalyst for SO2 and CO2
fixation under ambient condition
Chandan Kumar Karan,[a] and Manish Bhattacharjee*[a]
Abstract:
A
copper metal-organic hydrogel (MOG) has been
the SO2 is the most atom-economical and efficient method for
the synthesis of 1,3,2-dioxathiolane-2-oxides. There are only a
few report23 on such cycloaddition. There is only one report on
the diastereoselective synthesis of cyclic sulfites using SO2 and
epoxides under comparatively milder condition.23 Till date, there
synthesised using an amino acid-based ligand, Na2HL {H3L = 2-
{(3,5-di-tert-butyl-2-hydroxybenzyl)amino succinic acid} as a gelator.
The metallohydrogel exhibits pH-responsive nature as well as
chemical responsiveness. Besides, it shows rapid thixotropic
behavior when external mechanical forces are applied. The metal –
organic hydrogel can be used as a heterogeneous catalyst for the
reaction of SO2 and CO2 with epoxides to produce cyclic 1,3,2-
.
is no report on the MOG or MOF catalyzed fixation of SO2
Carbon dioxide, one of the major greenhouse gases in the
atmosphere, is the most abundant and cheapest source of C1
building unit.24-26 Therefore, the capture and chemical conversion
of the CO2 as a renewable C1 building unit is essential. But the
selection of the suitable catalyst is crucial for the activation and
the successful fixation of carbon dioxide. The transition metal
containing MOFs27-33 and MOGs34,35 have the potential as
heterogeneous catalysts for the fixation of CO2. MOGs have
more advantages over the MOFs, as syntheses of MOGs are
much more straightforward. However, very few MOGs are
reported for the CO2 fixation reaction.
Moreover, the heterogeneous nature of these catalysts makes
them suitable for the easy recovery and reusability for the next
catalytic cycle. Depending upon the reaction conditions and the
Lewis acidity of the metal center, the linear carbonates transform
into either cyclic carbonates36 or polycarbonates.37 It has been
shown that MOFs27,28,38,39 exhibit substrate size dependent
selectivity for the chemical conversion of CO2. Recently we have
reported the synthesis of a metal-organic hydrogel using a low
molecular weight gelator, which was found to be an efficient
catalyst for the fixation of CO2.35
dioxathiolane-2-oxides
and
carbonates,
respectively.
The
conversions were found to be dependent on the size and type of the
side chain of the epoxides.
Introduction
In recent years, metal-organic gels (MOGs) have attracted a
great deal of attention due to their potential application in
sensing,1-4 molecular recognition,5 catalysis,6 drug delivery,7-9
and dye adsorption.10,11 Low molecular weight MOGs are
formed12 due to various non-covalent interactions13 which are
responsible for the rapid self-assembly process of the discrete
metal complexes and formation of the microstructures where a
significant amount of solvent molecules are entrapped inside the
network. These weak non-covalent interactions, as well as the
microstructure, can be easily deformed through the external
stimuli14,15 and material can undergo the gel to sol transition or
vice-versa. The easy synthetic procedure and heterogenous
nature16,17 of the MOGs attracted the researchers’ attention in
the field of catalysis. With the appropriate choice of the transition
metals, the desired catalytic properties of the MOGs can be
achieved successfully.
Herein, we report the synthesis of copper(II) containing
multiresponsive metallohydrogel using Na2HL {H3L = 2-{(3,5-di-
tert-butyl-2-hydroxybenzyl)amino succinic acid},40 and its
catalytic activity towards fixation of SO2 and CO2 with epoxides.
Sulfur dioxide is a major environmental pollutant and causes
acid rain. Thus, the conversion of SO2 to value-added products
is desirable. 1,3,2-Dioxathiolane-2-oxides18 are important
electrophilic synthons in the field of organic chemistry due to
their high reactivity towards nucleophiles and are more reactive
than epoxides. The sulfites are used as an additive in the
electrolyte of the lithium-ion batteries.19 Although the chemistry
of the 1,3,2-dioxathiolane-2-oxides is known since 1932, an
efficient method for the synthesis of 1,3,2-dioxathiolane-2-oxides
remains a challenge. The cycloaddition of epoxides and the SO2
is one of the best routes to the cyclic sulfite.20 Conventionally
1,3,2-dioxathiolane-2-oxides are synthesized using thionyl
chloride and 1,2-diols, where chloride containing by-products are
generated.21,22 Metal-catalyzed cycloaddition of epoxides and
Results and Discussion
The ligand, Na2HL was prepared following the procedure
reported from this laboratory.40 The aqueous solution of the
ligand (0.03 mmol in 0.5 mL) and copper chloride (0.03 mmol in
0.5 mL) were mixed in a glass vial at room temperature, and
instantly a dark green MOG was formed (Figure 1).
[a]
Dr. C. K. Karan, Prof. Dr. M. Bhattacharjee, Department of
Chemistry, Indian Institute of Technology Kharagpur, 721302, India
E-mail: mxb@iitkgp.ac,in
Homepage: http://www.iitkgp.ac.in/department/CY/faculty/cy-mxb
Figure 1 Formation of the metal-organic hydrogel
Supporting information for this article is given via a link at the end of
the document.
1
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10.1002/ejic.201900594
European Journal of Inorganic Chemistry
FULL PAPER
The formation of the hydrogel was confirmed by an inverted vial
test. The minimum gelation concentration (MGC) for MOG was
found to be 2.28% (w/v) in water having effective gelation ratio
for metal and gelator 1:1 (Figure S1, Supplementary
Information). No gel formation was observed in common
organic solvents. In the earlier report from this laboratory,40 it
was shown that the ligand, H3L on reaction with FeCl3 affords
the complex anion [Fe(HL)2]-, where one of the carboxylic
groups in each ligand is not bonded with the metal center, and
they are involved in intramolecular hydrogen bonding. Based on
the observation, we theorized that reaction of copper chloride
with the disodium salt of the ligand in water would afford a
copper complex with free carboxylate groups and the hydrogen
bonding interactions of these carboxylate groups with solvent
water will afford the hydrogel. Thus we propose that the ligand
forms a 1:1 complex with Cu2+ ion and due to the extensive
hydrogen-bonding interactions with the solvent water the
hydrogel is formed.
microscopy (OM) (Figure 3). The FESEM image shows the
entangled network with foam like structures. The OM image of
the MOG reveals the dendritic growth of the metallogel. The
TEM image reveals the formation of a highly entangled network
sponge-like structure containing cavities inside it. This entangled
structure entrapped solvent molecules and is responsible for the
gel formation. The AFM image confirms that the MOG consists
of a spongy structure with a rough surface.
The hydrogel is stable at room temperature and does not show
any deformation or gel-sol transformation in a sealed vial for
months. Due to multiple cooperative non-covalent interactions,
the MOG shows a quick thixotropic behavior when the external
mechanical force is applied. On shaking, the MOG transforms
into a viscous solution, and on standing for a few minutes at
room temperature, the sol converts into to gel due to the shear
thinning property of the MOG (Figure 2).
Figure 3 Different type of microscopic images of Cu-MOG; (a) FESEM, (b)
TEM, (c) AFM and (d) OM image
Figure 2 Multi-stimuli responsive and pH responsive nature of the MOG
The MOG was also found to be pH sensitive in nature and stable
between the pH 4 to 9. The MOG is chemoresponsive (Figure 2)
in nature. When a few drops of dilute aqueous NH3 is added to
the MOG the gel brakes immediately, and a dark green solution
is formed due to the formation of a metal-amine complex. The
addition of dilute trifluoroacetic acid dropwise to this solution, the
gel is formed.
Figure 4 Plot of storage modulus (G') and loss modulus (G'') with (a) shear
stress at 1 rad sec-1; with (b) frequency at 0.5% strain and with (c) time for
step strain experiment for Cu-MOG
The MOG turns into
a hazy pale green solution when
The mechanical strength of the metallohydrogel was measured
by amplitude sweep (Figure 4a). The yield stress of the MOG at
the crossover point was found to be 1.3 Pa. In the frequency
sweep experiment, the G' and G'' were plotted against angular
frequency (ω) over a region 1 to 100 rad sec-1 (Figure 4b). The
G' was found to be larger than G'' over the entire region of
frequency, and the frequency-invariant characteristic confirms
the viscoelastic nature of the metallogel. The shear strain during
frequency sweep was found to be 0.5%. To confirm the
thixotropic behavior, we performed the step strain experiment9
(Figure 4c) at 25℃. At first, a constant strain of 0.5% was
applied to the gel, and then the strain was increased to 50% and
hydrochloric acid (pH below 4) is added dropwise, and upon
addition of an equivalent amount of dilute aqueous NaOH
solution to the hazy solution, the gel is reformed. However,
above pH 9, the gel brakes again and it turns into a dark green
solution. The reversible sol-gel transformation takes place due to
the breaking and reformation of the bonds as well as weak non-
covalent interactions between the metal and the gelator
molecules.
The morphology of the MOG was investigated by field emission
scanning electron microscopy (FESEM), transmission electron
microscopy (TEM), atomic force microscopy (AFM), and optical
2
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10.1002/ejic.201900594
European Journal of Inorganic Chemistry
FULL PAPER
was kept for a few minutes. Then the strain was decreased to
0.5% and kept for few minutes. It was observed that when the
applied strain was 50%, the loss modulus (G') was higher than
the storage modulus (G'') indicating the sol-like nature of MOG.
Immediately after decreasing the strain from 50% to 0.5%, the
MOG recovered to the initial state. After every cycle of gel-to-sol
transformation and vice versa during the experiment, the
recovery of the MOG was almost 100%.
From the MALDI-TOF spectrum of the MOG, we found a peak at
m/z 414 which corresponds to the 1:1 complex of copper and
the ligand (Figure S2 and S3, Supplementary Information).
The xerogel was further characterized by IR spectroscopy and
Thermogravimetric analysis (TGA). The IR spectrum (Figure S4,
Supplementary Information) Cu-MOG shows metal coordinated
carboxylate stretching as (COO–) stretch at 1558 and s (COO–)
1406 cm-1.
more straightforward as compared to the synthesis of MOFs.
Usually, MOFs are synthesized under the solvothermal condition,
which requires long reaction time and high temperature and
pressure. In most of the cases, the MOGs can be synthesized
just by mixing the geletor with the metal ions at room
temperature, and the gel can be obtained within a few minutes.
Reports on MOG catalyzed fixation of CO2 are not numerous.
Here we have used the MOG xerogel for the chemical fixation of
CO2 into value-added products.
Various Lewis bases, as well as alkali metals, have been used
as homogeneous catalysts for the reaction of SO2 with
epoxides.19 There is only one report on the amine functionalized
silica as a heterogeneous catalyst for the reaction of SO2 with
epoxides.19 However, the reactions were carried out at 100 C,
and the diastereoselectivity was found to be very poor. To the
best of our knowledge, there is no report on the fixation of SO2
using MOGs or MOFs. The reaction of SO2 and epoxides using
the xerogel as a catalyst produced a mixture of cyclic sulfites
and poly sulfites.
From the thermogravimetric analysis (TGA), it was found that
the Cu-MOG is stable up to 190 C (Figure S5, Supplementary
Information). After 190 C the material starts degrading and near
to 800 C only metal oxide exists.
For the optimization of the reaction, 1,2-epoxybutane was
chosen as a substrate. In a typical solvent-free condition, 1,2-
epoxybutane (10 mmol) was carried out with sulfur dioxide
purged through bladder in the presence of 0.02 mmol of the
MOG xerogel as a catalyst along with 5 mol% TBAB as a co-
catalyst at room temperature. After 8 hours, the conversion of
the starting epoxides was found to be good. But the yield of the
From the observed morphology we expected that the xerogel
might exhibit some porosity and we conducted reversible N2
sorption measurements at 77K (Figure 5). The BET surface area
for Cu-MOG was measured to be 50.64 m2 g-1 and it exhibits a
saturated sorption amount of N2 of 27 cm3 g-1. The desorption
curve is lower than the adsorption curve. This may be due to the
weak interaction between the surface of the Cu-MOG and the N2
molecules which lead to the faster desorption. After the N2
sorption experiment, we have carried out CO2 sorption
measurement at 273 K (Figure 6) and we can see that Cu-MOG
can uptake 6.5 cm3 g-1 amount of CO2 gas.
1
cyclic sulfite was low. The H NMR spectrum of the product is
the same as that of the mixture of the products. The yield of the
cyclic sulfite was found to be 21% (Table 1, entry 2). The
conversions in the cases of propylene oxide (30%), 1,2-epoxy-3-
phenoxy propane (16%) were found to be low. Interestingly the
diastereomeric ratios (dr) were found to be excellent, from 70:30
to 90:10. It may be noted that there are very few reports on the
diastereoselective synthesis of 1,3,2-dioxathiolane-2-oxides.20
a
Table 1 Cycloaddition of various epoxides with SO2
Entry
Substrate
Conversionb, c (%)
drd
Figure 5 N2 adsorption isotherm for Cu-MOG
1
2
3
4
30
80:20
70:30
70:30
60:40
21
20
21
5
16
90:10
Figure 6 CO2 adsorption isotherm for Cu-MOG
6e
57
90:10
We then proceeded to test the efficacy of the xerogel as a
catalyst for the reaction of SO2 and CO2 with epoxides for their
chemical fixation. In recent years, copper-containing MOFs have
been shown to catalyze the chemical fixation of CO2.41,42
However, it is worth mentioning that the synthesis of MOGs is
aReaction conditions: epoxide (10 mmol), catalyst (0.02 mmol), TBAB (0.16 g,
5 mol%) under SO2 (1 bar), 300 K and 8 h. bFrom 1H NMR. cAverage of three
reactions. dDiastereomeric ratio from 1H NMR of the isolated products.
eMixture of the products stirred at 60 C in the presence of the MOG for 8 hrs.
3
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10.1002/ejic.201900594
European Journal of Inorganic Chemistry
FULL PAPER
Takenaka et al. reported that in the reaction of propylene oxide
in the initial stage poly(propylene sulfite) was formed in more
amount and cyclic sulfite was formed in low amount and with
time the yield of the cyclic sulfite increased.19 Accordingly, after
8 hours we removed the SO2 source, and stirred the mixture of
the products of the reaction of SO2 with 1,2- epoxybutane in the
presence of the MOG for 60 hours at room temperature, and the
yield of 4-ethyl-dioxathiolane-2-oxide increased from 21% to
51%. We then proceeded to examine the conversion of the
polymeric product to the cyclic sulfite under the heating condition.
The mixture of the products obtained from the reaction of 1,2-
epoxybutane with SO2 was stirred at 60 C in the presence of
the MOG for 8 hours, and the yield of the cyclic product was
found to be 57% (Table 1, entry 6). However, in the absence of
the MOG, we could not detect any increase in the conversion of
the polymeric sulfite to the cyclic product. It may be noted that a
reaction of 1,2-epoxybutane with SO2 carried out only in the
presence of TBAB afforded only 1% of the mixture of products.
We could not detect any product formation in the absence of the
MOG as well as TBAB.
coordination of the epoxide oxygen to the copper center is more
difficult, and thus the conversion to cyclic carbonate decreases
with the increase in the size of the epoxide side chain. The
control reaction of 1,2-epoxybutane with CO2 in the presence of
TBAB and in the absence of MOG afforded the cyclic carbonate
in 3% yield. The control experiment in the absence of the MOG
as well as TBAB was carried out and we could not detect any
product formation.
a
Table 2 Cycloaddition of various epoxides with CO2
Entry
1
Substrate
Conversionb, c (%)
78
TON
390
2
3
4
5
6
70
63
23
24
26
350
315
115
120
130
1
All the products have been characterized by H and 13C NMR
spectroscopy. Also, one of the major diastereomers of 4-
phenoxy-1,3,2-dioxathiolane-2-oxide has been structurally
characterized by single crystal X-ray crystallography (Figure 7).
aReaction conditions: epoxide (10 mmol), catalyst (0.02 mmol), TBAB (0.16 g,
5 mol%) under CO2 (1 bar), 300 K and 48 h. bFrom 1H NMR cAverage of three
reactions
Figure 7 ORTEP view of 4-phenoxy dioxathiolane-2-oxide. Hydrogen atoms
In the cases of the reaction of SO2 and CO2, the xerogel was
recollected by centrifugation and washed with acetone (2 × 3
mL). After drying the material in an oven at 60 C for 1 hour, we
have tested the recyclability of the xerogel using propylene oxide
as a model substrate for CO2 and 1,2-epoxybutane for SO2
fixation.
omitted for clarity
The cycloaddition of the propylene oxide (10 mmol) was carried
out with carbon dioxide purged at 1 atm pressure using 0.02
mmol of the MOG xerogel as a catalyst along with 5 mol%
tetrabutylammonium bromide (TBAB) as a co-catalyst at room
temperature. After 48 hours, the yield of the product was found
to be 78% (Table 2, entry 1). After the optimization of the
reaction condition, we have carried the reaction using various
types of epoxides containing short to long side chain aliphatic
and aromatic group. For the straight chain substrate, we found a
good to moderate conversion. With increasing bulk of the
substituent, the conversion of the epoxide to the carbonate
decreases sharply as the approach of the epoxy oxygen to the
metal center becomes unfavorable. Due to this, low conversions
to carbonate were observed in the cases of tert-butyl glycidyl
ether and styrene oxide. Since the reactions were carried out
under a solvent-free condition, the lipophilicity or solubility of the
epoxide does not play an essential role in the observed trend in
the conversion. Thus the decrease in the conversion with the
increase in bulk of the side chain may be explained by the steric
effect of the epoxide side chain. The critical step in the reaction
of epoxide with CO2 is the activation of the epoxide ring by the
metal center.32 With the increase in the bulk of the epoxide, the
Figure 8 Recyclability study of the Cu-MOG
In the case of the reaction of SO2, after the first cycle, the activity
drops (Figure 8) because of the decomposition of the xerogel by
the acid generated from the reaction of SO2 with moister. So in
4
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10.1002/ejic.201900594
European Journal of Inorganic Chemistry
FULL PAPER
The MALDI-TOF spectrum of the MOG was recorded using 2,5-
dihydroxybenzoic acid as the matrix in the Bruker Daltonics, model:
Ultraflextreme instrument.
the reaction of SO2, the catalyst is not recyclable. However, in
the case of CO2 fixation, up to five cycles the efficiency of the
material was found to be very good (Figure 8). The powder X-
ray diffraction analysis of the used xerogel shows that the
integrity of the material remains intact (Figure S6, Supplimentary
Information).
X-ray crystallography
Single-crystal X-ray data of the 4-phenoxy dioxathiolane-2-oxide were
collected on Bruker Smart APEX II CCD system that uses graphite
monochromated Mo Kα radiation (λ = 0.71073 Å). The structure was
solved by the direct method and refined by the least square method on
F2 employing WinGX43 package, and the relevant programs {SHELX-9744
and ORTEP-345} implemented therein. Non-hydrogen atoms were refined
anisotropically, and hydrogen atoms on C-atoms were fixed at calculated
positions and refined using a riding model. The details of crystal data
collection and refinement of complexes are summarized in Table S1.
CCDC 1860491 contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cambridge
Crystallography Data Center via www.ccdc.cam.ac.uk/data_request/cif.
Conclusions
In conclusion, a new copper containing metal-organic hydrogel
has been synthesised using the disodium salt of the ligand, 2-
{(3,5-di-tert-butyl-2-hydroxybenzyl)amino succinic acid}, Na2HL.
The xerogel of the Cu-MOG can be used as a catalyst for the
chemical conversion of SO2 to cyclic 1,3,2-dioxathiolane-2-
oxides with high diastereoselectivity and the conversion of CO2
to carbonates on reaction with the epoxides at room temperature
and under one atmospheric pressure.
Synthesis of the Metal – Organic Gel
Experimental Section
Ten different glass vials were taken and in each of the vials the disodium
salt of the ligand, Na2HL (0.012 g. 0.03 mmol) dissolved in water (0.5 mL)
was placed. To the vials aqueous solution (0.5 mL) of CuCl2·2H2O (0.1 to
1.0 equivalent) was added and on standing at room temperature for five
minutes the gel formation was tested by inverted vial technique.
All the chemicals, L-aspartic acid was bought from SRL chemicals, 2,4-
di-tert-butyl phenol was bought from Sigma-Aldrich and zinc acetate,
sodium hydroxide was commercially available. Analytical reagent grade
solvents were used without further distillation. Propylene oxide, 1,2-
epoxybutane, 1,2-epoxyhexane, tert-butyl glycidyl ether, 1,2-epoxy-3-
phenoxypropane were bought from Sigma-Aldrich and styrene oxide was
bought from Merck. The CO2 gas used for the catalysis was 99.9% pure.
The SO2 gas used for the catalysis was prepared in the laboratory. The
ligand, Na2HL was synthesized by the procedure reported from our
laboratory.36
General Procedure for the cycloaddition of SO2 to epoxides
The epoxide (10 mmol) was taken in a Schlenk tube to this was added
the MOG (0.116 g; 0.2 mol% based on the MOG complex) and
tetrabutylammonium bromide (TBAB, 5 mol%). Sulfur dioxide was purged
through a bladder for 8 hours at room temperature. The conversion of the
epoxide was calculated using the 1H NMR spectra of the crude product
using calculated amount of mesitylene as an internal standard.
The morphology of the xerogel was characterised using a field emission
scanning electron microscope (Zeiss EVO 60 with Oxford EDS detector)
operating at 5−10 KV. The sample was prepared by dropping the diluted
solution of MOG on the thin aluminium sheets and then dried in air. To
minimise the sample charging a thin layer of Au was coated on the
sample before the experiment.
General Procedure for the cycloaddition of CO2 to epoxides
The reaction of the epoxide with CO2 was carried out in an analogues
manner as described above for the reaction of SO2, only difference being
instead of 8 hours of stirring, the reaction was carried out for 48 hours.
The conversion of epoxide into cyclic carbonate was calculated from the
1H NMR spectra of the crude product using calculated amount of
mesitylene as an internal standard.
The gel sample was characterised by an analytical TEM (FEI.
TECNAIG220S-TWIN) instrument operated at 120 kV. The sample was
prepared by dropping the much-diluted solution of gels on the carbon-
coated copper grids, and the samples were allowed to dry for overnight.
The reaction mixture was centrifuged to recover the catalyst for reusing
the catalyst. Then the clear solution was decanted, and the xerogel
material was washed thoroughly with acetone and dried in an oven. Then
the reaction was done under the same condition as previously described
using propylene oxide as a substrate.
The morphology of the MOG was analysed by atomic force microscope
(Agilent 5500). AFM sample was prepared by dropping the very dilute
solution of MOG on a small piece of the glass slide and allowed to dry
overnight before imaging.
The gel sample was characterised by an optical image analyser (Leica
DMLM) instrument. The sample was prepared by dropping the very dilute
solution of the MOG on the glass slide.
Acknowledgments
We thank Department of Science & Technology, Government of
India for X-ray facility, FESEM facility and NMR facility (Grant
Number SR/FST/CSII-026/2013) and SERB for financial support
(Grant Number CRG/208/000026).
For the MOG, rheological measurements were carried out on an MCR
102 (Anton Paar) modular compact rheometer using a 25 mm diameter
parallel plate with a constant tool gap of 1 mm. The MOG was placed on
the lower plate, and a stress amplitude sweep experiment was carried
out at a constant angular frequency of 1 rad sec-1 at 298K to obtain
storage or elastic modulus, G′, and loss or viscous modulus, G″. The
frequency sweep measurement was carried out in the linear viscoelastic
range at constant stress.
Keywords: Metal-organic gel • Sulphur dioxide • Carbon dioxide
• Heterogeneous catalyst • Copper(II) hydrogel
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This article is protected by copyright. All rights reserved.

10.1002/ejic.201900594
European Journal of Inorganic Chemistry
FULL PAPER
Entry for the Table of Contents
FULL PAPER
A copper(II) hydrogel has been
synthesized and characterized. The
xerogel can be used as
Copper Hydrogel Catalysis
C. K. Karan, M. Bhattacharjee*
heterogeneous and recyclable catalyst
for the conversion of SO2 1,3,2-
dioxathiolane-2-oxides with high
diastereoselectivity. The xerogel can
also be used for the chemical fixation
of CO2.
Page No. – Page No.
A Copper(II) Metal-Organic Hydrogel
as a Catalyst for a Chemical Fixation
of SO2 and CO2
7
This article is protected by copyright. All rights reserved.