ZIF-8-Nanocrystalline Zirconosilicate Integrated Porous Material for the Activation and Utilization of CO2 in Insertion Reactions

Article abstract of DOI:10.1002/asia.202000001

The conversion of CO₂ to useful chemicals, especially to atom economical products, is the best approach to utilize an excess of CO₂ present in the atmosphere. In this study, a metal-organic framework (ZIF-8) is integrated with nanocrystalline zirconosilicate zeolite to develop an integrated porous catalyst for CO₂ insertion reactions. The catalyst exhibits excellent activity for the CO₂ insertion reaction of epoxide to produce cyclic carbonate in neat condition without the addition of any co-catalyst. The catalyst is stable and recyclable during the cyclic carbonate synthesis. Further, the catalyst also exhibits very good activity in another CO₂ insertion reaction to produce quinazoline-2,4(1H, 3H)-dione.

Full text of DOI:10.1002/asia.202000001

CHEMISTRY
AN ASIAN JOURNAL
www.chemasianj.org
Accepted Article
Title: ZIF-8-Nanocrystalline Zirconosilicate Integrated Porous Material
for the Activation and Utilization of CO2 in the Insertion Reactions
Authors: Diksha Srivastava, Poonam Rani, and Rajendra Srivastava
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Asian J. 10.1002/asia.202000001
Link to VoR: http://dx.doi.org/10.1002/asia.202000001
A Journal of
A sister journal of Angewandte Chemie
and Chemistry – A European Journal

10.1002/asia.202000001
Chemistry - An Asian Journal
FULL PAPER
ZIF-8-Nanocrystalline Zirconosilicate Integrated Porous Material for the Activation and
Utilization of CO2 in the Insertion Reactions
Diksha Srivastava,a,b Poonam Rani,a,b and Rajendra Srivastava*b
Dedication ((optional))
[a]
Diksha Srivastava, Poonam Rani
Both authors have an equal contribution
Diksha Srivastava, Poonam Rani, and Rajendra Srivastava
Department of Chemistry
[b]
Indian Institute of Technology Ropar
Rupnagar-140001, India
E-mail: rajendra@iitrpr.ac.in
Supporting information for this article is given via a link at the end of the document.
Abstract: The conversion of CO2 to useful chemicals, especially
process is the insertion of CO2 into epoxides/amines to produce
wide range of organic compounds such as cyclic
to atom economical products, is the best approach to utilize an
excess of CO2 present in the atmosphere. In this study, a metal-
organic framework ZIF-8 is integrated with nanocrystalline
zirconosilicate zeolite to develop an integrated porous catalyst for
the CO2 insertion reactions. The catalyst exhibits excellent activity
for the CO2 insertion reaction of epoxide to produce cyclic carbonate
in neat condition without the addition of any co-catalyst. The catalyst
is stable and recyclable during the cyclic carbonate synthesis.
Further, the catalyst also exhibits very good activity in another CO2
insertion reaction to produce quinazoline-2,4(1H, 3H)-dione.
a
carbonate/carbamate and quinazoline-2,4(1H, 3H)-dione. In
order to develop sustainable catalysts for CO2 insertion
reactions, CO2 should be adsorbed and suitably activated. When
adsorption is considered, zeolites and metal-organic frameworks
(MOFs) are the most preferred materials due to their tunable
porosity.[6, 7, 16-18] Zeolites have microporosity, which makes them
suitable materials for CO2 adsorption. However, zeolites alone
can not be used for CO2 insertion reactions, due to their inability
to activate CO2. MOFs have microporosity and high surface area,
therefore they are good candidates for CO2 capture and storage.
Only, a few MOFs are known in the literature, which has the
ability to activate CO2 [19]. CO2 is an acidic molecule, and it can
only be activated if the basic sites are present in the MOFs.[20]
Thus; functional MOFs having amines groups have been
explored in the CO2 insertion reactions.[21-23] Further, zeolites
based materials have been also explored in cyclic carbonate
synthesis by functionalizing zeolites with amines and basic ionic
liquids.[24-27] Other porous materials such as basic metal oxides
(such as MgO, Mg-Al mixed oxide), metal phosphates, porous
polymers, and g-C3N4 have shown interesting results in CO2
insertion reaction. [28-32] Moreover, it may be noted that most of
the MOFs and zeolite-based catalysts require a high volume of
solvents (such as DMF, NMP, CH2Cl2, etc.), which makes this
Introduction
Gaseous CO2 present in the troposphere region of the earth is
creating harmful effects on all living organisms including human
beings. The anthropogenic CO2 emission (due to the rapid
industrial evolution, high demand for energy, and fossil fuels-
based transportation) is mainly responsible for the increase in
CO2 level to more than 400 ppm in the atmosphere. Due to this
increase in the CO2 level, the average temperature on earth has
risen by more than 1 C (since the pre-industrial era) and is
expected to increase to 1.9 C by 2050.[1] Thus it is very
important to control the CO2 emission rate. Government
agencies are making efforts to reduce the CO2 concentration but
these efforts might give limited results due to the large
population and their energy demand. Thus the role of scientists
has become essential to restrain the level of CO2. There are only
two possibilities by which this problem can be sorted out, (1)
CO2 capture and storage and (2) CO2 conversion to useful
chemicals and fuels. CO2 capture and storage are possible only
when the emission source emits a large concentration of CO2.[2,
3]. Only limited success has been achieved with porous materials
and liquid amine-based scrubbers for CO2 adsorption and
separation.[4-7] The kinetic diameter of CO2 (0.33 nm) is very
similar to O2 (0.35 nm) and N2 (0.36 nm) which makes it very
difficult to design porous materials with high CO2 capture
capacity.[8] Therefore, the development of alternative routes for
the conversion of CO2 to useful chemicals and fuels has become
extremely useful.
process unsustainable. Thus; it is important to develop
a
suitable catalyst which can be operated in neat condition to
produce cyclic carbonate in high selectivity.
Zeolites are stable and recyclable under liquid phase and
gas phase conditions (even under harsh conditions). MOF
based catalysts are relatively unstable under liquid phase
conditions. Therefore, efforts are being made to develop hybrid
and stable porous MOF-zeolite or MOF-silica catalysts for
various catalytic applications.[33-36] Zeolite and MOF based
hybrid porous materials would be suitable for the CO2 insertion
reaction. Zeolites have the capability to adsorb CO2 whereas
certain MOFs have the capability to adsorb and activate CO2.
Therefore, the integration of both these porous materials can
provide a sustainable solution to the CO2 insertion reaction.
Literature reports suggest that ZIF-8 prepared with Zn ions and
2-methyl imidazole is suitable for the CO2 activation reaction.[19,
Only a few industrial processes based on CO2 are known,
such as; the production of urea, organic carbonates, methanol,
salicylic acid, etc.[9-16] This is due to the thermodynamic
inertness of CO2. CO2 can be used as the source of O (a mild
oxidant), CO (in urea synthesis), and C (for the synthesis of
methanol, CH4 and other fuels).[9-15] But the most atom economy
20]
ZIF-8 with sodalite topology has large cages with a diameter
of 11.6 Å and a narrow 6-ring pore opening of 3.4 Å.[37] Such a
pore opening is suitable for the CO2 adsorption.[38] However, for
this reaction, another reactive partner should also be adsorbed
This article is protected by copyright. All rights reserved.

10.1002/asia.202000001
Chemistry - An Asian Journal
FULL PAPER
0.4
0.3
0.2
0.1
0.0
effectively. Thus large surface area zeolite is required. It has
been recently shown that nanocrystalline zirconosilicate has the
capability to activate epoxide and convert it to amino alcohols
via ring-opening reaction.[39] Literature also suggests that
(a)
700
650
600
550
500
450
400
350
300
250
200
150
100
50
(b)
ZIF-8
polyethylene amine supported mesoporous zirconosilicate
3
6
12 15 18 21
Por9e size (nm)
41]
exhibits very good CO2 adsorption characteristics.[40,
The
ZIF-8-Nano-ZrS
introduction of optimum amounts of Zr and amine provides
suitable acid-base characteristics for efficient CO2 adsorption
and activation.
The objective of this study is to develop zeolite-MOF
integrated porous material for CO2 insertion reaction, for the
synthesis of cyclic carbonate under solvent-free conditions in the
absence of any co-catalyst. Considering the effective adsorption
of CO2 in ZIF-8 and amorphous zirconosilicate, and high activity
of nanocrystalline zirconosilicate in the ring-opening of epoxide,
herein, integrated porous material built with nanocrystalline
zirconosilicate (designated as Nano-ZrS) with MFI framework
structure and ZIF-8 is developed and explored in the production
of cyclic carbonates. Further, the developed hybrid porous
material is also successful in the synthesis of quinazoline-2,4(1H,
3H)-dione by the CO2 insertion reaction of 2-amino benzonitrile.
ZIF-8
Nano-ZrS
ZIF-8-Nano-ZrS
Nano-ZrS
0.0
0.2
0.4
0.6
0.8
1.0
5
10 15 20 25 30 35 40 45 50
Relative Pressure (P/P0)
(Degree)
Figure 1. (a) Powder X-ray diffraction patterns and (b) N2-sorption isotherms
of parents and integrated material prepared in this study (Inset shows BJH
pore size distribution).
The textural properties of the parents and their
integrated material were determined by the nitrogen sorption
measurements Figure 1b. Nano-ZrS exhibits type IV isotherm.
Significant adsorption below 0.05 (P/P0) corresponds to the N2
adsorption in the ZSM-5 micropores. With an increase in the
pressure above P/P0>0.15, a steady increase in the adsorption
volume is observed which corresponds to the condensation of
N2 in inter-crystalline mesoporous void space. ZIF-8 exhibits a
type I isotherm corresponding to microporous material (Figure
1b). N2 adsorption in low-pressure range (<0.05 P/P0)
corresponds to the adsorption in the micropores present in ZIF-
8. Almost a flat adsorption feature is observed above 0.1 (P/P0)
which suggests that this material has a very low external surface
on which further N2 adsorption would take place on increasing
the P/P0. ZIF-8-Nano-ZrS shows the adsorption feature very
similar to that of ZIF-8 but with lower adsorption volume. For this
sample, adsorption above 0.9 (P/P0) suggests the presence of
inter-crystalline porosity similar to that of Nano-ZrS.
Results and Discussion
In this study ZIF-8-Nano-ZrS, a zeolite-MOF hybrid porous
material is prepared by following the synthesis strategy depicted
in Scheme 1. First, Nano-ZrS is prepared by following the molar
composition 0.93 TEOS/ 0.07 TPHAC/0.02 ZrIPO/ 0.35
TPAOH/40 H2O under hydrothermal condition using
(C2H5O)3SiC3H6N(CH3)2C16H33]Cl as an additive. Subsequently,
Nano-ZrS
is
functionalized
with
3-(2-imidazolin-1-yl)
propyltriethoxysilane to prepare imidazole-functionalized Nano-
ZrS, represented as Nano-ZrS-Im. The as-prepared Nano-ZrS-
Im is treated with Zn(OAc)2 and 2-methyl imidazole in water
under the ambient condition to prepare ZIF-8-Nano-ZrS. The
synthesis details are provided in the experimental section and
supporting information section. The characterization details
describing the successful formation of the hybrid porous ZIF-8-
Nano-ZrS is provided below.
Table 1. Physico-chemical properties of the different materials investigated in
this study.
Sample
Total surface External surface
Total pore
area
area (m2/g)
volume(cm3/g)
SBET (m2/g)
Nano-ZrS
ZIF-8
565
1290
884
305
93
0.54
0.59
0.52
(Zn(OAc)2.2H2O
ZIF-8-Nano-ZrS
102
Hmim
Nano-ZrS
ZIF-8-Nano-ZrS
Nano-ZrS-Im
Scheme 1. Schematic presentation for the synthesis of the ZIF-8-Nano-ZrS
The pore size distribution suggests that ZIF-8 contains only
micropores. Nano-ZrS exhibits the mesopore size distribution in
the range of 1.4-4.5 nm and 7-12 nm with a peak maximum at
3.6 nm and 8.6 nm. ZIF-8-Nano-ZrS exhibits pore size
distribution somewhat similar to that of ZIF-8. It also shows a
pore size distribution in the range of 5 to 6.5 nm with a peak
maximum of 5.6 nm, suggesting the presence of intercrystalline
pores due to the incorporation of Nano-ZrS in the integrated
porous material. Micropore size analysis confirms that hybrid
porous material contains the micropores corresponding to MFI
and ZIF-8 frameworks. The textural properties of all three
materials synthesized in this study are summarized in Table 1.
composite catalyst.
Powdered XRD patterns of parents and their composite material
are shown in Figure 1a. The XRD patterns of Nano-ZrS and ZIF-
8
are analogous with those reported in the literature for
21]
zirconosilicate and ZIF-8 frameworks, respectively.[39,
The
XRD pattern of ZIF-8-Nano-ZrS exhibits the characteristic peaks
of Nano-ZrS and ZIF-8, which reflects that ZIF-8 framework, is
successfully grown on the Nano-ZrS surface without disturbing
the structural integrity of the zeolite framework.
2
This article is protected by copyright. All rights reserved.

10.1002/asia.202000001
Chemistry - An Asian Journal
FULL PAPER
The highest surface area is obtained for ZIF-8 whereas the
lowest surface area is obtained for Nano-ZrS. However, the
external surface area is the highest for Nano-ZrS whereas it is
the lowest for ZIF-8. The composite material exhibits the surface
area and external surface area in between ZIF-8 and Nano-ZrS.
The surface morphology and microstructure of the
ZIF-8-Nano-ZrS exhibits two distinguished morphologies of
different sizes, which correspond to zeolite Nano-ZrS, and MOF
ZIF-8. Close inspection shows that the large crystals of ZIF-8
are cross-linked with the Nano-ZrS, which confirms that the ZIF-
8 framework is successfully grown on the surface of Nano-ZrS.
The integration of ZIF-8 on the surface of Nano-ZrS
materials were analyzed using SEM (Figure 2). SEM image of
the ZIF-8 exhibits polyhedral like crystal morphology. A spheroid
morphology with irregular crystal sizes is observed for the Nano-
ZrS. The morphology of ZIF-8-Nano-ZrS is found to be very
similar to ZIF-8, which confirms that the imidazole groups on the
surface of Nano-ZrS successfully participate in the crystallization
process of ZIF-8 framework. The energy dispersive X-ray (EDS)
analysis was carried out to investigate the chemical composition
of the parent and composite materials (Figure S1). Zn, O, N, and
C elements are observed in the EDS spectrum of ZIF-8 whereas
Zr, Si, and O elements are observed in the EDS spectrum of
Nano-ZrS. However, the two additional peaks corresponding to
Si and Zr confirm the growth of the ZIF-8 framework on the
surface of zeolite in the ZIF-8-Nano-ZrS (Figure S1).
was also confirmed by the Fourier transform infrared (FTIR)
spectroscopy (Figure 4a). The characteristic peak of Nano-ZrS
at 553 cm-1 corresponds to the pentasil MFI framework of
zirconosilicate zeolite. The absorption peak at 1071 cm-1 and
1223 cm-1 corresponds to the internal and external asymmetric
stretching vibrations of Si-O-Si, respectively while the symmetric
stretching of Si-O-Si is observed at 797 cm-1. The characteristic
peak of imidazole at 1655 cm-1 (C=C stretching) in the Nano-
ZrS-Im confirms the functionalization of imidazole on the surface
of Nano-ZrS. ZIF-8 shows the adsorption at 423 cm-1 which
indicates that Zn2+ chemically interacts with the N atom of the
HMIM linker and forms the imidazolate framework. Furthermore,
the absorption bands in the region of 1285-1490 cm-1
correspond to ring stretching. The C-N and C-H bending
vibrations are observed at 992 and 760 cm-1, respectively
whereas C-N stretching vibration is observed at 1143 cm-1. All
the characteristic peaks of zeolite Nano-ZrS and MOF ZIF-8 are
observed in the FTIR spectrum of ZIF-8-Nano-ZrS, which
indicates that the ZIF-8 framework is successfully grown on the
surface of Nano-ZrS (Figure 4a).
ZIF-8
Nano-ZrS
2 µm
1 µm
(a)
(b)
100
90
80
70
60
50
40
30
20
ZIF-8-Nano-ZrS
ZIF-8
20.0 %
423
1143
992 760
ZIF-8-Nano-ZrS
1 µm
2 µm
1655
Nano-ZrS-Im
Figure 2. SEM images of parents and their integrated material.
ZIF-8
Nano-ZrS
18.5 %
Transmission electron microscopy (TEM) was
recorded to distinguish both the frameworks in the ZIF-8-Nano-
ZrS (Figure 3). Large rhombic crystal structure (with particle
sizes 430 nm) is observed for the ZIF-8. Very small zeolite
nanocrystals are observed for the Nano-ZrS, which shows the
lattice fringes with 1.01 nm lattice spacing.
Nano-ZrS-Im
ZIF-8-Nano-ZrS
797
1071
Nano-ZrS
1223
553
1600 1400 1200 1000 800 600 400
400
600
800 1000
Wavenumber (cm-1)
Temperature (K)
Figure 4. (a) FT-IR spectra, and (b) thermograms of parents and their
integrated material prepared in this study.
Thermogravimetric analysis (TGA) was performed to
investigate the amount of individual frameworks in the ZIF-8-
Nano-ZrS hybrid material (Figure 4b). No significant weight loss
is observed in the Nano-ZrS, which indicates the high stability of
the zeolite framework. The weight loss in Nano-ZrS-Im
corresponds to the removal of functionalized linker on the
surface of zirconosilicate. The difference between the weight
loss of Nano-ZrS-Im and Nano-ZrS is related to the amount of
imidazole linker anchored to the surface of Nano-ZrS (Figure 4b).
However, two weight losses are observed in the ZIF-8. The first
weight loss corresponds to the removal of physisorbed H2O
molecules (up to 500 K). The second weight loss is related to
the degradation of the framework to form ZnO. The difference in
Figure 3. TEM images of parents and their integrated hybrid porous material.
3
This article is protected by copyright. All rights reserved.

10.1002/asia.202000001
Chemistry - An Asian Journal
FULL PAPER
the weight loss between ZIF-8 and ZIF-8-Nano-ZrS (18.5 wt%)
corresponds to the amount of zirconosilicate present in the
composite material (Figure 4b)
ZrS shows weak CO2-desorption above 400 K. However, ZIF-8-
Nano-ZrS shows weak CO2 desorption in 325-425 K, but very
high CO2 desorption is observed in the range of 425-563,
suggesting that the material has stronger basicity than ZIF-8.
Total basicity of ZIF-8-Nano-ZrS (1.3 µmol/g)) is more than that
of their parents materials, ZIF-8 (1.1 µmol/g) and Nano-ZrS (0.7
µmol/g). Thus the higher amount of CO2 adsorption/desorption
and stronger basic sites present in ZIF-8-Nano-ZrS are expected
to provide better activity in the CO2 insertion reactions.
Catalytic Activity
For the CO2 insertion reaction, the CO2 should be adsorbed and
effectively activated on the catalyst surface. Thus it is important
to investigate the CO2 adsorption in all the samples. CO2
adsorption isotherm of parents and their integrated material is
shown in Figure 5. CO2 adsorption experiment was performed at
298 K after evacuating the materials at 423 K before the CO2
adsorption. With an increase in the CO2 pressure in the range of
0 to 1 bar, the CO2 adsorption increased for all the materials.
Nano-ZrS shows the highest adsorption of CO2 in the entire
pressure range (0.0-1.0 bar) which is consistent with the
literature reports with amorphous zirconosilicate.[40] ZIF-8
exhibits the lowest CO2 adsorption among various materials
investigated in this study. The CO2 adsorption with ZIF-8-Nano-
ZrS falls in between Nano-ZrS and ZIF-8. Higher adsorption of
CO2 in Nano-ZrS is due to the presence of Zr in MFI lattice
which is known to enhance the CO2 adsorption.[40] Moreover,
intercrystalline mesopores, micropores with a wider pore window
(0.54 nm), and a larger external surface area of Nano-ZrS than
ZIF-8 are responsible for the higher CO2 adsorption in the
material. The integrated material ZIF-8-Nano-ZrS contains 18.5
% Nano-ZrS, therefore, it exhibits more CO2 adsorption than
ZIF-8. The CO2 adsorption capacities of Nano-ZrS, ZiF-8, and
ZIF-8-Nano-ZrS at 1 bar are determined to be 50.4 cm3g−1, 25.7
cm3g−1, and 36.5 cm3g−1, respectively.
For CO2 insertion reaction in the synthesis of cyclic
carbonate, only high CO2 adsorption/desorption is not sufficient
condition. It is the effective CO2 adsorption on the catalyst surface
(determined from CO2-TPD), and the ring-opening of epoxide by the
adsorption of epoxide on the Lewis acid sites of the catalyst, both are
required. Pyridine adsorbed FT-IR measurement was carried out to
confirm the presence of Lewis acid sites in the material (Figure S3).
Nano-ZrS exhibits a strong peak at 1444 cm-1 which corresponds to
pyridine bonded to the Lewis acid sites of the material. The peak at
1596 cm-1 is due to H-bonded pyridine with surface Si-OH groups
present in this material. In the case of ZIF-8, only weak adsorption at
1439 cm-1 is observed, which suggests that this material has very
weak Lewis acidity. Moreover, no H-bonded pyridine peak is
observed for this material, confirming the absence of any surface –
OH group in this material (Figure S3). In the case of ZIF-8-Nano-ZrS,
weak absorptions at 1439 cm-1 and 1591 cm-1 confirm the presence
of Lewis acid sites and H-bonded pyridine, respectively, which further
confirms the integration of these two porous materials (Figure S3).
The catalytic activity data presented here provide exact
information about the activity of the catalysts under optimized
reaction conditions. Nano-ZrS is found to be almost inactive for this
reaction (Table 2, Entry 2). Based on CO2 adsorption data at 298 K
(discussed above) and effective ring opening of epoxide (cited
previously),[39] this catalyst should have provided the best activity. The
inferior activity of Nano-ZrS in cyclic carbonate synthesis clearly
suggests that CO2 is not effectively adsorbed (as confirmed from
CO2-TPD) on Nano-ZrS under the experimental condition, and
not suitable for the CO2 insertion reaction. The activity of Nano-ZrS-
Im is somewhat better when compared to Nano-ZrS, which
suggests that CO2 is partially adsorbed and present on the
catalyst surface due to the weak interaction between imidazole
50
40
30
20
and CO2 molecules (Table 2, Entry 3). Since only
a low
10
concentration of imidazole is present on the Nano-ZrS-Im,
therefore, the activity is very poor. The activity of ZIF-8 is very
good under the optimized reaction condition (Table 2, Entry 4).
Moreover, excellent activity is achieved using ZIF-8-Nano-ZrS
(Table 2, Entry 5). This is due to the effective adsorption of CO2 in
the material and also due to the effective activation of CO2 by
the imidazole linker present in the material. In our previous
report, we have demonstrated that Zn based MOFs including
ZIF-8 was not good for the ring-opening of the epoxide during
the amination reaction of the epoxide.[42]
ZIF-8
Nano-ZrS
ZIF-8-Nano-ZrS
0
0.2 0.4 0.6 0.8 1.0
Pressure (bar)
Figure 5. CO2 adsorption isotherms of parents and integrated porous material
prepared in this study at 298 K.
The activation of CO2 is related to the chemisorption of
CO2. Thus, temperature-programmed desorption of CO2 (CO2-
TPD) measurements for all catalysts were conducted. The CO2-
TPD profiles of the parents and their composite material are
presented in Figure S2. The CO2 desorptions for ZIF-8 take
place in the range of 325-425
K and 425-563 K, which
correspond to weak and medium basic sites, respectively. Nano-
4
This article is protected by copyright. All rights reserved.

10.1002/asia.202000001
Chemistry - An Asian Journal
FULL PAPER
Table 2. Cycloaddition of CO2 to epoxide using different catalysts prepared in
mg, the activity of catalyst increases. Above 100 mg catalyst, no
significant increase in epoxide conversion is obtained. Finally,
the influence of CO2 pressure is also investigated in the range of
2.5 bar to 12.5 bar. With an increase in the CO2 pressure, the
epichlorohydrin conversion increases up to 10 bar. With a further
increase in the CO2 pressure, no significant increase in the
epichlorohydrin conversion is obtained. Thus, 393 K, 100 mg
catalyst, 10 bar CO2 pressure, and 2 h reaction time are
optimized for CO2 insertion reaction of epichlorohydrin. The
activation energy Ea for this reaction is calculated for ZIF-8 and
ZIF-8-Nano-ZrS using the Arrhenius plot (ln k versus 1/T, Figure
S5) by following the first-order kinetics because the catalyst
amount is constant and the high CO2 concentration is taken
when compared to the epichlorohydrin (which can also be
considered constant). The activation energies for ZIF-8 and ZIF-
8-Nano-ZrS are calculated to be 50.8 kJ/mol and 48.8 kJ/mol,
respectively. Lower activation energy further confirms the higher
activity of ZIF-8-Nano-ZrS when compared to ZIF-8 in the CO2
insertion reaction of epichlorohydrin.
this study.
Catalyst
Reactant
Time
(h)
Conv.
(%)
Produc
t Sel.
(%)
TONa
E.
N
o.
1.
2.
3.
4.
-
ECH
ECH
ECH
ECH
2
2
2
2
0
0
-
-
Nano-ZrS
Nano-ZrS-Im
ZIF-8
<1
-
9.3
80.5
97.3
9.8
60.6
70.2
(65.8)c
96.8
(89.5)c
58.2
87.9
35.4
76.6
(70.5)c
92.5
5.
ZIF-8-Nano-ZrS
ECH
2
94.9
102.5
6.
7.
8.
9.
ZIF-8-Nano-ZrS
ZIF-8-Nano-ZrS
ZIF-8-Nano-ZrS
ZIF-8-Nano-ZrS
PO
PO
SO
SO
2
8
2
8
97.4
93.7
95.6
94.8
61.6
93.0
37.5
81.1
10. ZIF-8-Nano-ZrSb
ECH
2
94.7
97.9
Reaction condition: Epoxide (38 mmol), catalyst (100 mg), reaction
temperature (393 K), reaction time (2 h), CO2 pressure (10 bar). aTON= Turn
over number (moles of product/moles of catalyst), bCatalytic data obtained
after the fifth recycles, and cIsolated yield. ECH= Epichlorohydrin, PO
=
Propylene oxide, and SO = Styrene oxide.
At the same time, Zr based MOF and nanocrystalline
zirconosilicates have been reported to exhibit very good activity
in the ring-opening reaction of the epoxide.[39] If the activity of
nanocrystalline zirconosilicates and Uio-66 is considered, the
activity of nanocrystalline zirconosilicate is more in the ring-
opening reaction of the epoxide.[39,41] Thus, due to the weak
activation of epoxide by ZIF-8, the activity of ZIF-8 in the CO2
insertion reaction to produce chloropropene carbonate is found
to be moderate (Table 2, entry 4). Due to the presence of
integrated framework, simultaneous activation of epoxide by
Nano-ZrS and effective adsorption and activation of CO2 by ZIF-
8, the activity of ZIF-8-Nano-ZrS is found to be excellent (Table
2, entry 5). GC-MS data show that the side product formed
during the CO2 insertion reaction with epichlorohydrin is 1-
chloropropanol/2-chloropropanol. It may be noted that the
reaction is performed in the neat condition and in the absence of
any co-catalyst. The influence of various reaction parameters,
such as reaction time, temperature and catalyst amount is
investigated (Figure S4). With an increase in reaction
temperature, the epoxide conversion increases but the
selectivity of cyclic carbonates marginally decrease. However,
the reaction proceeds well at 393 K. Above 393 K, only a
marginal increase in the epoxide conversion is obtained with a
further decrease in the carbonate selectivity. Thus 393 K is
chosen for further optimization. The influence of the reaction
time suggests that better selectivity and carbonate yield are
obtained after 2 h of the reaction with epichlorohydrin (Figure
S4). With an increase in the catalyst amount from 50 mg to 150
ZIF-8
Nano-ZrS
ZIF-8-Nano-ZrS
Scheme 2. A plausible reaction mechanism for the insertion reaction of CO2
into epoxide.
Having optimized the reaction condition, the
applicability of the composite catalyst is further investigated with
different aliphatic and aromatic epoxides. Lower cyclic carbonate
yield is obtained using propylene oxide and styrene oxide (Table
2, Entries 6, 8). Thus, the reaction duration for these substrates
is increased to obtain a good product yield (Table 2, Entries 7,
9). To investigate the stability of the composite catalyst, ZIF-8-
Nano-ZrS is recycled five times. No significant change in the
activity is observed even after five recycles (Table 2, Entry 1 and
Figure S6). XRD (Figure S7), FT-IR (Figure S7), and SEM
(Figure S7) investigations confirm that the recycled catalyst is
stable after the five recycles.
In this study, ZIF-8 framework is integrated with
nanocrystalline
zirconosilicate
by
functionalization
of
nanocrystalline zirconosilicate with imidazole, that participates in
the growth of ZIF-8 through the imidazole surface-functionalized
nanocrystalline zirconosilicates. Scheme 2 shows the plausible
mechanism for the CO2 insertion reaction of the epoxide. The
presence of bi-functional sites in the ZIF-8-Nano-ZrS attributes
the efficiency of the catalyst. The Lewis acid sites in ZIF-8-Nano-
5
This article is protected by copyright. All rights reserved.

10.1002/asia.202000001
Chemistry - An Asian Journal
FULL PAPER
ZrS (Zn/Zr center, Zr is more effective than Zn) adsorb and
activate the epoxide. Whereas; the basic sites (imidazole linker)
effectively activate the adsorbed CO2 (CO2 is more adsorbed in
Nano-ZrS but effectively adsorbed in ZIF-8). Thus, the
simultaneous adsorption and activation of epoxide and CO2 in
close proximity on ZIF-8-Nano-ZrS facilitate the CO2 insertion
into epoxide to produce cyclic carbonate. The activity of the
present catalyst is compared with other similar catalysts
reported in the literature. The comparative data suggests that
the developed catalyst in this study exhibits better or
comparable activity even in the absence of any co-catalyst
(Table S1).
70
60
50
40
30
20
10
0
(a)
(b)
70
60
50
40
30
20
10
0
Nano-ZrS
ZIF-8 ZIF-8-Nano-ZrS
Catalyst
383 393 403 413 423 433 443
Temperature (K)
(d)
80
(c)
70
70
60
50
40
30
20
10
0
After achieving the excellent activity in the cyclic
60
50
40
30
20
10
0
carbonate synthesis, the applicability of the ZIF-8-Nano-ZrS is
further investigated in the synthesis of quinazoline-2,4(1H, 3H)-
dione. Quinazoline-2,4(1H, 3H)-dione is produced by the
addition of CO2 to 2-aminobenzonitrile. The influence of solvent
demonstrated in our previous studies suggests that DMF is the
best solvent for this reaction not only with respect to the 2-
aminobenzonitrile conversion but also with respect to the
isolation of the product.[26] Thus in this study, the reaction
parameters are evaluated in DMF solvent using 2-amino
benzonitrile as a model substrate. The influence of reaction
parameters such as type of catalyst, reaction temperature,
catalyst amount, and reaction pressure is shown in Figure 6. In
this reaction, only quinazoline-2,4(1H, 3H)-dione is obtained as
the selective product which is confirmed by the 1H-NMR (Figure
S8). Nano-ZrS is found to be inactive for this reaction (Figure
6a). However, low product yield is obtained using ZIF-8 catalyst
(Figure 6a). The highest product yield is obtained using ZIF-8-
Nano-ZrS (Figure 6a). With an increase in the reaction
temperature, pressure, and catalyst amount, the product yield
increases (Figure 6b-d). The excellent yield of 83 % is obtained
when the reaction is conducted at 433 K and 40 bar pressure
using 150 mg of catalyst for 12 h. Comparative catalytic activity
shown in Figure 6a suggests that the synthesis of quinazoline-
2,4(1H, 3H)-dione facilitates by the basic sites of the catalyst.
The low activity of ZIF-8 suggests that the basic sites in the ZIF-
25
30
35
40
50
100
150
Catalyst amount (mg)
CO2 Pressure (Bar)
Figure 6. Influence of reaction parameters, (a) catalyst, (b) temperature, (c)
CO2 pressure, and (d) catalyst amount in the synthesis of quinazoline-2,4(1H,
3H)-dione by the insertion reaction of CO2 to 2-aminobenzonitrile. Reaction
condition: (a) 2-aminobenzonitrile (2 mmol), DMF (10 mL), temperature (423
K), CO2 pressure (35 bar), catalyst (100 mg), and time (12 h); (b) 2-
aminobenzonitrile (2 mmol), DMF (10 mL), CO2 pressure (35 bar), catalyst
(100 mg), and time (12 h); (c) 2-aminobenzonitrile (2 mmol), DMF (10 mL),
temperature (423 K), catalyst (100 mg), and time (12 h); (d) 2-
aminobenzonitrile (2 mmol), DMF (10 mL), temperature (423 K), CO2 pressure
(35 bar), and time (12 h).
Thus, the efficient adsorption and dispersed basic sites
present in the ZIF-8-Nano-ZrS are responsible for the excellent
activity of ZIF-8-Nano-ZrS in quinazoline-2,4(1H, 3H)-dione
synthesis. Scheme S1 shows the plausible reaction mechanism
for the synthesis of quinazoline-2,4(1H, 3H)-dione using ZIF-8-
Nano-ZrS as the catalyst. The acidic proton of the amino group
in 2-aminobenzonitrile is abstracted by the basic site of the
catalyst and generates the intermediate 1a. Furthermore, similar
to cyclic carbonate synthesis, the basic sites in the catalyst
adsorb and activate the CO2 molecules. Then, the intermediate
1a undergoes a nucleophilic attack to active CO2 molecule and
form intermediate 1b, which attacks–CN group and generates
intermediate 1c. Ring-opening (intermediate 1d) followed by
intramolecular cyclization leads to the formation of intermediate
1e, which undergoes the tautomerization and generates stable
cyclic amide quinazoline-2,4(1H, 3H)-dione.
8
frameworks are not easily accessible to the reactant
molecules. ZIF-8 grown on Nano-ZrS provides more isolated
and dispersed sites. Moreover, the adsorption of 2-
aminobenzonitrile is facilitated on the Nano-ZrS sites through
weak coordination between the amino groups of 2-
aminobenzonitrile and Lewis acidic Zr sites.
Conclusion
2-Methyl imidazole based ZIF-8 was integrated with
nanocrystalline zirconosilicate to prepare integrated porous
structure. XRD and FT-IR confirm the formation of integrated
material. Parent ZIF-8 exhibited the large micropore surface
area, whereas; the Nano-ZrS exhibited a large external surface
6
This article is protected by copyright. All rights reserved.

10.1002/asia.202000001
Chemistry - An Asian Journal
FULL PAPER
area. Transmission electron microscopic investigation revealed
that the integrated porous material was built with large ZIF
crystals (400-600 nm) and very small size Nano-ZrS
nanocrystals (10-20 nm). ZIF-8 exhibited moderate activity in the
CO2 insertion reaction in epichlorohydrin to form cyclic
carbonate due to the weak Lewis acidity which facilitates the
ring-opening of the epoxide. The effective CO2 adsorption in ZIF-
8 was due to the 2-methyl imidazole building moiety and large
micropore area. An integrated porous material, ZIF-8-Nano-ZrS,
exhibited excellent activity in the cyclic carbonate synthesis
because Nano-ZrS exhibited excellent ring-opening capability
due to the presence of Lewis acid sites and effective adsorption
of CO2 by ZIF-8 sites present in the material. Simultaneous,
effective adsorption of CO2 and epoxide in the close proximity on
integrated porous material was responsible for the excellent
activity of this material in neat condition. The excellent yield of
the product under mild reaction conditions in the absence of any
co-catalyst and efficient recyclability are other attractive features
of this catalytic process. Moreover, the integrated porous
material exhibited very good activity in the synthesis of
quinazoline-2,4(1H, 3H)-dione, which was much higher than
their parent porous materials, ZIF-8 and Nano-ZrS. We are sure
that such an approach to developing MOF-zeolite integrated
material will attract the signification attention of the materials
chemist and catalysis researchers to develop similar types of
materials for the appointed applications.
to obtain imidazole functionalized Nano-ZrS (designated as
(Nano-ZrS-Im).
For the preparation of ZIF-8-Nano-ZrS composite, the
first 0.2 g of Nano-ZrS-Im was added to a solution containing
0.219 g of Zn(OAc)2 and 10 mL of deionized water. The resultant
mixture was stirred under the ambient condition for 1 h (solution
A). In a separate container, 2.46 g of 2-methyl imidazole (Hmim)
was dissolved in deionized water (30 mL) and stirred at room
temperature for 1 h (solution B). Then, solution B was added to
solution A and the resultant mixture was slowly stirred under the
ambient condition for 24 h. After the reaction, the cloudy
aqueous suspension was centrifuged, washed several times
with methanol and dried in a vacuum oven at 373 K for 12 h to
obtain ZIF-8-Nano-ZrS.
For a comparative study, ZIF-8 was also prepared by
following the same procedure without adding Nano-ZrS-Im.
The details of the instruments and methods used for
materials characterization are provided in the Electronic
Supporting Information Section.
Catalytic activity
The details for the procedure of the catalytic reactions are
provided in the Electronic Supporting Information Section.
Acknowledgments
Experimental Section
The work presented in this manuscript is supported by DST-
SERB, New Delhi (EMR/2016/001408). PR acknowledges the
Director’s Fellowship provided by the IIT Ropar. RS thank IIT
Ropar for providing grants through the Faculty Research
Innovation Award.
Synthesis of ZIF-8-Nano-ZrS nanocomposite
For the synthesis of ZIF-8 integrated nanocrystalline
zirconosilicate
(ZIF-8-Nano-ZrS),
initially
nanocrystalline
zirconosilicate (Nano-ZrS) was synthesized by following the
reported procedure.[39] In a typical synthesis of nanocrystalline
zirconosilicate, zirconium (IV) isopropoxide (ZrIPO, 0.18 g) was
added dropwise to tetraethylorthosilicate (TEOS, 3.94 g) and the
resultant solution was stirred for 15 min under ambient condition
until a clear solution was formed (solution A). In a separate
bottle, [(C2H5O)3SiC3H6N(CH3)2C16H33]Cl (TPHAC, 0.72 g) and
tetrapropylammonium hydroxide (TPAOH, 3.54 g) was added
into the deionized water (4.3 g) (Solution B). Then, solution A
was added to solution B, followed by the addition of 8 mL
deionized water. The resultant mixture was slowly stirred at
ambient conditions for 6 h. The resultant molar composition was
0.93 TEOS/ 0.07 TPHAC/0.02 ZrIPO/ 0.35 TPAOH/40 H2O. Next,
the resultant reaction mixture was transferred to a Teflon-lined
stainless steel autoclave and hydrothermally treated at 443 K
under the stirring condition for 5 days. After the crystallization,
the obtained solid product was filtered, washed with distilled
water, and dried at 373 K. To remove the incorporated
surfactant molecules, the solid material was calcined at 823 K
for 6 h. The final obtained material was designated as Nano-ZrS.
Then, the external surface of Nano-ZrS was
Conflicts of interest
The authors declare no competing financial interest
.
Keywords: CO2 activation • Metal-organic framework • Nanocrystalline
Zeolite • Integrated Porous Framework • Insertion Reactions
[1]
[2]
G. T. Narisma, A. J. Pitman, Earth Interact. 2006, 10, 1-27.
E. S. Sanz-Perez, C. R. Murdock, S. A. Didas, C.W. Jones, Chem. Rev.
2016, 116, 11840-11876.
[3]
[4]
[5]
[6]
[7]
[8]
[9]
S. A. Didas, S. Choi, W. Chaikittisilp, C.W. Jones, Acc. Chem. Res.
2015, 48, 2680-2687.
B. Dutcher, M. Fan, A. G. Russell, ACS Appl. Mater. Interfaces 2015, 7,
2137-2148.
Q. Wang, J. Luo, Z. Zhong, A. Borgna, Energy Environ. Sci. 2011, 4,
42-55.
R. Banerjee, H. Furukawa, D. Britt, C. Knobler, M. O’Keeffe, O.M.
Yaghi, J. Am. Chem. Soc. 2009, 131, 3875-3877.
J. Liu, P. K. Thallapally, B. P. McGrail, D. R. Brown, J. Liu, Chem. Soc.
Rev. 2012, 41, 2308-2322.
functionalized with an imidazole linker. 0.136
g of 3-(2-
V. Presser, J. McDonough, S. H. Yeon, Y. Gogotsi, Energy Environ.
Sci. 2011, 4, 3059-3066.
imidazolin-1-yl) propyltriethoxysilane and 0.5 g Nano-ZrS were
added to 12.5 mL dry toluene and the reaction mixture was
refluxed for 24 h. The resultant mixture was filtered, washed with
dichloromethane and dried in a vacuum oven at 373 K for 12 h
J. Ma, N. Sun, X. Zhang, N. Zhao, F. Xiao, W. Wei, Y. Sun, Catal.
Today, 2009, 148, 221–231.
[10] M. Aresta, Carbon Dioxide as Chemical Feedstock, 1 edition, Wiley-
7
This article is protected by copyright. All rights reserved.

10.1002/asia.202000001
Chemistry - An Asian Journal
FULL PAPER
VCH, 2010.
[11] J. S. Chang, V. P. Vislovskiy, M. S. Park, D. Y. Hong, J. S. Yoo, S. E.
Park, Green Chem. 2003, 5, 587-590.
[12] J. E. Hallgren, Patent US4410464A, 1982.
[13] A. J. Kamphuis, F. Picchioni, P. P. Pescarmona, Green Chem. 2019,
21, 406-448.
[14] W. G. Tu, Y. Zhou, Z. G. Zou, Adv. Mater. 2014, 26, 4607-4626.
[15] K. C. Waugh, Catal. Today. 1992, 15, 51-75.
[16] D. Bonenfant, M. Kharoune, P. Niquette, M. Mimeault, R. Hausler, Sci.
Technol. Adv. Mater. 2008, 9, 013007-013013.
[17] F. Akhtar, Q. Liu, N. Hedin, L. Bergstrom, Energy Environ. Sci. 2012, 5,
7664-7673.
[18] S. Xiang, Y. He, Z. Zhang, H. Wu, W. Zhou, R. Krishna, B. Chen, Nat.
Commun. 2012, 3, 954-962.
[19] A. C. Kathalikkattil, R. Babu, J. Tharun, R. Roshan, D. W. Park, Catal.
Surv Asia 2015, 19, 223–235.
[20] C. M. Miralda, E. E. Macias, M. Zhu, P. Ratnasamy, M. A. Carreon,
ACS Catal. 2012, 12, 180−183.
[21] P. Rani, R. Srivastava, New J. Chem. 2017, 41, 8166-8177.
[22] T. Lescouet, C. Chizallet, D. Farrusseng, ChemCatChem 2012, 4, 1725
– 1728.
[23] P. Patel, B. Parmar, R. I. Kureshy, N. H. Khan, E. Suresh, Dalton
Trans. 2018, 47, 8041–8051.
[24]
R. Srivastava, D. Srinivas, P. Ratnasamy, J. Catal. 2005, 233, 1-15.
[25] R. Srivastava, D. Srinivas, P. Ratnasamy, Catal. Lett. 2003, 91, 133-
139.
[26] B. Sarmah, R. Srivastava, Ind. Eng. Chem. Res. 2017, 56, 8202-8215.
[27] B. Sarmah, B. Satpati, R. Srivastava, J. Colloid Interface Sci. 2017,
493, 307-316.
[28] A. H. Chowdhury, P. Bhanja, N. Salam, A. Bhaumik, S. M. Islam, Mol.
Catal. 2018, 460, 46-54.
[29] A. H. Chowdhury, I. H. Chowdhury, S. M. Islam, Ind. Eng. Chem. Res.
2019, 58, 11779−11786.
[30] S. Bhunia, R. A. Molla, V. Kumari, S. M. Islam, A. Bhaumik, Chem.
Commun. 2015, 51, 15732-15735.
[31] S. Samanta, R. Srivastava, Sustain. Energy Fuels 2011, 1, 1390–1404.
[32] K. Yamaguchi, K. Ebitani, T. Yoshida, H. Yoshida and K. Kaneda, J.
Am. Chem. Soc., 1999, 121, 4526-4527.
[33] P. Rani, R. Srivastava, J.Colloid Interface Sci. 2019, 557, 144-155.
[34] P. Rani, R. Srivastava, Sustain. Energy Fuels 2018, 2, 1287–1298.
[35] D. Suttipat, W. Wannapakdee, T. Yutthalekha, S. Ittisanronnachai, T.
Ungpittagul, K. Phomphrai, S. Bureekaew, C. Wattanakit, ACS Appl.
Mater. Interfaces 2018 10, 16358−16366.
[36] L. Lin, T. Zhang, X. Zhang, H. Liu, K. L. Yeung, J. Qiu, Ind. Eng. Chem.
Res. 2014, 53, 10906−10913.
[37] D. F. Jimenez, S. A. Moggach, M. T. Wharmby, P. A. Wright, S.
Parsons, T. Düren, J. Am. Chem. Soc. 2011, 133, 8900–8902.
[38] A. Phan, C. J. Doonan, F. J. Uribe-Romo, C. B. Knobler, M. O'Keeffe,
O. M. Yaghi, Acc. Chem. Res. 2010, 43, 58–67.
[39] R. Kore, R. Srivastava, B. Satpati, ACS Catal. 2013, 3, 2891-2904.
[40] Y. Kuwahara, D. Y. Kang, J. R. Copeland, N. A. Brunelli, S. A. Didas, P.
Bollini, C. Sievers, T. Kamegawa, H. Yamashita, C. W. Jones, J. Am.
Chem. Soc. 2012, 134, 10757−10760.
[41] B. L. Newalkar, J. Olanrewaju, S. Komarneni, J. Phys. Chem. B 2001,
105, 8356-8360.
[42] P. Rani, R. Srivastava, RSC Adv. 2015, 5, 28270–28280.
8
This article is protected by copyright. All rights reserved.

10.1002/asia.202000001
Chemistry - An Asian Journal
FULL PAPER
Table of Contents
NH2
CN
ZIF-8-Nano-ZrS
H
O
O
N
O
O
NH
O
O
R
R
Efficient ring opening of epoxide by nanocrystalline zirconosilicate and effective adsorption of CO2 by ZIF-8 led to prepare the
integrated porous material, ZIF-8-Nano-ZrS, which exhibited excellent activity in the CO2 insertion of epoxide for cyclic carbonate
synthesis under a neat condition in the absence of any co-catalyst. The catalyst exhibited excellent activity in the CO2 insertion
reaction to prepare quinazoline-2,4(1H,3H)-dione.
This article is protected by copyright. All rights reserved.