Catalytic CO2 Fixation over a Robust Lactam-Functionalized Cu(II) Metal Organic Framework

Article abstract of DOI:10.1021/acs.inorgchem.9b00684

A porous, Cu(II)-metal organic framework (Cu-MOF) constituted of a rigid lactam functionalized ditopic ligand (H₂L) was synthesized at room temperature under slow evaporation conditions {H₂L = (5-(1-oxo-2,3-dihydro-1H-inden-2-yl)isop

Full text of DOI:10.1021/acs.inorgchem.9b00684

Article
pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Catalytic CO2 Fixation over a Robust Lactam-Functionalized Cu(II)
Metal Organic Framework
Shagufi Naz Ansari,†,+ Pawan Kumar,†,+ Anoop K. Gupta,† Pradeep Mathur,*,†
and Shaikh M. Mobin*,†,‡,§
†Discipline of Chemistry, ‡Discipline of Metallurgy Engineering and Materials Science (MEMS), and §Discipline of Biosciences and
Biomedical Engineering (BSBE), Indian Institute of Technology Indore, Simrol, Khandwa Road, Indore 453552, India
S
* Supporting Information
ABSTRACT: A porous, Cu(II)-metal organic framework (Cu-MOF)
constituted of a rigid lactam functionalized ditopic ligand (H2L) was
synthesized at room temperature under slow evaporation conditions {H2L =
(5-(1-oxo-2,3-dihydro-1H-inden-2-yl)isophthalic acid)}. The single crystal X-
ray structure revealed the formation of a 3D framework of Cu-MOF with one-
dimensional (1D) channels decorated with lactam groups and exposed metal
centers in the crystallographic c-axis. Interestingly, Cu(II) coordinated DMF
molecules were eliminated from the Cu(II) metal center on activation of Cu-
MOF at a temperature of 150 °C under high vacuum to generate a solvent
free framework with pores lined with unsaturated Lewis acidic Cu(II) ions,
i.e., Cu-MOF′. The lactam functionalized channels inclined toward the CO2,
which interact with the Cu(II) metal sites lined in the channels of Cu-MOF′
and exhibit fascinating solvent-free heterogeneous catalytic conversion of CO2
to cyclic carbonates at atmospheric pressure of CO2, under mild conditions.
Furthermore, the Cu-MOF′ catalyst was easily recycled and reused for several cycles without a significant loss in catalytic
activity.
MOFs are an architect of nanoporous organic−inorganic
hybrid materials with organic linkers that are connected to
metal ions/clusters.28 The framework when the design is tuned
appropriately shows the following properties: (i) chemical and
thermal stability, (ii) functional pores with a high surface area,
and (iii) permanent porosity which leads to various potential
applications such as energy storage, heterogeneous catalysis,
fluorescence sensing, ferroelectricity, drug delivery, gas storage
and separation, etc.29−34 In particular, MOFs advocate for the
unique opportunity as heterogeneous catalysts on the basis of
the following rationales: (i) the presence of functionalized
pores for the substrate selectivity, (ii) presence of clear and
uniformly distributed metal centers as active catalytic sites, and
(iii) recovery and reusability due to its heterogeneous
nature.24,35,36 MOFs with a large pore volume, nitrogen base
functionalized channels, thermal stability, and exposed
unsaturated metal centers (UMCs) are a good choice for
chemical fixation of CO2 to value added chemicals such as
cyclic carbonates,37 urea derivatives,38 and formic acid.39
Currently, various MOFs exhibited excellent CO2 catalytic
conversion under high temperatures,24,40 and some MOFs
demonstrated moderate CO2 catalytic conversion at room
temperature over a period of 48 h.41,42 In terms of industrial
scale up of CO2 conversion into cyclic carbonates,43 which are
INTRODUCTION
■
The excessive use of fossil fuels as a primary source of energy
releases huge quantities of carbon dioxide (CO2), i.e., a leading
greenhouse gas.1 Thus, capturing and conversion of CO2 into
some nontoxic, abundant, renewable, and economically viable
valuable chemical product is in need.2−6 In this regards, the
catalytic conversion of CO2 into the synthesis of five-
membered cyclic carbonates is consider to be an alternative
and potential CO2 utilization process.7−9 These cyclic
carbonates may be used as (i) solvents, (ii) well-known
intermediates in the synthesis of ethylene glycol and acyclic
carbonates, (iii) precursors for pharmaceutical products, (iv)
electrolyte in batteries, and (v) as a raw material for
cosmetics.9−14 The synthesis of five-membered cyclic carbo-
nates through CO2 fixation with epoxides has been extensively
effective with several homo- and heterogeneous catalysts.15−18
However, in the case of homogeneous catalysts, the real
concerns are that the product separation is generally tedious
and catalyst recycling is expensive. Considerably, these
concerns have been dealt with to a greater extent by utilizing
the heterogeneous catalysts such as coordination complexes,
zeolites, metal oxides, and functional polymers, which
demonstrates lower activity in vast circumstances or
leaching.19−23 Such lower activity has been overcome by
utilizing a new and innovative class of porous materials, i.e.,
metal organic frameworks (MOFs), which might be the
ultimate catalysts in a heterogeneous system.23−27
Received: March 9, 2019
© XXXX American Chemical Society
A
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Scheme 1. Schematic Synthesis of Cu-MOF
microscope. The gas adsorption studies were accomplished with a
Quantachrome Quadrasorb automatic volumetric instrument.
X-ray Crystallography. A suitable single crystal of Cu-MOF was
collected on a RigakuOxford Supernova CCD diffractometer
(graphite monochromated Mo Kα radiation, λα = 0.71073 Å) at
100 K. The data collections were evaluated using the CrysAlisPro
CCD software and collected by the standard φ−ω scan techniques.
Also, data was scaled and reduced by CrysAlisPro RED software. The
direct method was used for solving the crystal structure, followed by
full matrix least-squares refinements against F2 (all data are HKLF 4
format) using SHELXL 2014/753 and difference Fourier synthesis,
and least-squares refinement revealed the positions of the non-
hydrogen atoms. The crystal system, orientation matrix, and cell
dimensions were determined according to the established procedures,
and Lorentz polarization and multiscan absorption correction were
applied. Non-hydrogen atoms were refined with anisotropic displace-
ment parameters. Hydrogen positions were placed geometrically at
calculated positions and refined isotropically. The lattice solvent
molecules of Cu-MOF are highly disordered and cannot be modeled
as discrete atomic sites; therefore, the PLATON-SQUEEZE54
refinement program was used to calculate the solvent contributions.
The solvent composition was estimated on the basis of combined
study of TGA and squeezed electron counts which are included in the
molecular formula. The lattice parameter, the data collection, and
refinement parameter are summarized in Table S1, while selected
bond distances and bond angles are given in Table S2 in the
Supporting Information.
ubiquitous intermediates in the pharmaceutical and electro-
chemical industries7,44,45 produced by extremely toxic
phosgene gas hydrolysis, an unconventional atom economic
and environmentally benign route is anticipated.1,46,47 In this
regards, recently, various MOFs have been efficiently employed
as reusable heterogeneous catalysts for the conversion of CO2
into cyclic carbonates.40,48,49 The development of efficient and
facile synthesized MOFs as catalysts will be an ideal choice for
an easy and economically viable workup procedure.50,51
Pioneering experimental results proved that Lewis acid−base
sites consisting of a binary catalytic system with a leaving
halide anion synergistically supports the CO2 cycloaddition to
epoxide.26 Moreover, the MOF functionalized with nitrogen
bases and other polar functional groups improve the selectivity
as well as the affinity of the CO2 molecule toward the
catalysts.25,52
Keeping all these features in mind, we have facilely
synthesized the lactam functionalized, porous 3D Cu-MOF
which displayed excellent thermal and chemical stability.
Further, on activation of Cu-MOF to Cu-MOF′, the presence
of both the accessible lactam group and exposed Cu sites is
revealed, which makes Cu-MOF′ a potential candidate for
CO2 fixation under milder conditions. This work not only
offers excellent heterogeneous catalytic activity for CO2
fixation but also provides a structural−catalytic relationship
which is an ingenious strategy for building functionalized
MOFs.
Synthesis of the Ligands. The details of the ligand (H2L)
synthesis and its characterization are given in the Supporting
Information.
Synthesis of Cu-MOF. The Cu-MOF was synthesized at room
temperature under slow evaporation conditions. H2L (30 mg, 0.1
mmol) and Cu(NO3)2·3H2O (40 mg, 0.16 mmol) were dissolved in 4
mL of DMF and 1.5 mL of H2O, respectively, in two different conical
flasks. These solutions were heated on the hot plate until the
appearance of a clear solution followed by their mixing at hot
conditions. Then three drops of 1 M HCl were added into the
reaction mixture, which was then stirred and mixed well. The final
mixture was placed carefully for slow evaporation at ambient
conditions. After 4 days, block-shaped and sky blue colored crystals
appeared on the walls and the base of the flask which were further
filtered, washed with DMF and H2O, and collected. Yield = 20 mg,
84% (based on H2L linker). Anal. calcd for C19H19CuN2O7.5
(458.9091): C 49.73, H 4.17, N 6.10%. Found: C 50.12, H 4.11, N
5.78%. FT-IR (KBr, cm−1): 3417 (br), 2978 (m), 1665 (m), 1631 (s),
1568 (s), 1412 (s), 1371 (m), 1300 (m), 1078 (m), 775 (m), 728
(m), 650 (m).
Activation of Cu-MOF. Before starting the catalytic CO2 fixation,
the framework must be activated to create the solvent free sample
containing Lewis acidic Cu(II) centers with unsaturated coordina-
tions.35 To generate the activated framework, first, the solvent
exchange experiment was carried out by keeping as-synthesized
sample in acetone for 7 days and changing the acetone twice a day.
The second step begins with the heating of acetone exchanged sample
at 150 °C, under ultrahigh vacuum pressure for 8 h which results in
the generation of a complete solvent free framework. Upon activation,
EXPERIMENTAL SECTION
■
Materials and Chemicals. All the reagents employed were
commercially available and used as provided without further
purification. Cu(NO3)2·3H2O (98%), 5-aminoisophthalic acid, and
2-(bromomethyl)benzonitrile were obtained from Sigma-Aldrich and
used as received. Other chemicals, i.e., HCl, KOH, K2CO3, SOCl2,
and solvents were procured from Loba Chemie and S. D. Fine
Chemicals (India). All solvents were dried and purified prior to use
following standard methods.
Characterization and Instrumentation. Fourier transform-
infrared (FT-IR) spectra were recorded on a PerkinElmer FT-IR
spectrophotometer with KBr pellets from the 500 to 4000 cm−1
region. 1H and 13C NMR spectra were recorded on a JEOL-ECX 400
FT (400 and 100 MHz, respectively) instrument in DMSO-d6 and
CDCl3 with Me4Si as the internal. ESI-mass spectra were obtained
with the Waters Q-TOF Premier mass spectrometer. Microanalyses
(carbon, hydrogen, and nitrogen) of the samples were performed
using a Flash 2000 elemental analyzer (Thermo Fischer). Single-
crystal X-ray structural studies were conducted on a Rigaku-Oxford
Supernova CCD diffractometer. The powder X-ray diffraction
(PXRD) data were recorded on a Rigaku SmartLab X-ray
diffractometer using monochromatic Cu−Kα radiation (1.54 Å),
and the tube voltage and current were 40 kV and 40 mA, respectively.
The scanning electron microscopy (SEM) images of the samples were
obtained by the Supra55 Zeiss field-emission scanning electron
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Figure 1. SEM images of Cu-MOF at different magnifications: (a) 100 μm, (b) 30 μm, and (c) 20 μm.
Figure 2. (a) Asymmetric unit of Cu-MOF; (b) showing the pseudotetra-carboxylate linker based SBUs containing Cu(II) ion (hydrogen atoms
are omitted for clarity); (c) view showing the lactam decorated cages; and (d) space-filled view of the 1D channels in the framework.
the Cu-MOF′ sample changes its color from blue to black signifying
the loss of metal bound DMF molecules, resulting the generation of
coordinatively unsaturated, i.e., 4-coordinated, Lewis acidic Cu(II)
ions. The PXRD pattern of bulk samples of Cu-MOF confirms the
purity and integrity of the activated framework, which well matches
with the as synthesized Cu-MOF.
epoxides. The reaction was performed in a 20 mL Schlenk tube
furnished with a magnetic stirrer. Reagents viz. epoxide (20 mmol),
catalyst Cu-MOF′ (5 wt %), and cocatalyst Bu4NBr (1 mmol) were
taken in a Schlenk tube and stirred at room temperature and/or 70 °C
(based on the boiling point of epoxides) under CO2 (99.999%)
bubbling at atmospheric pressure. After completion of the reaction, 5
mL of CHCl3 was added followed by filtration of the reaction mixture
for separation of the catalyst from it. The solvent was evaporated at
General Procedure for Catalytic Cycloaddition Reaction of
CO2. The catalytic CO2 fixation was carried out by cycloaddition with
C
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Figure 3. (a) Gas adsorption isotherm of Cu-MOF′: CO2 at 195 and 298 K temperatures, N2 at 77 K temperature and 1 atm pressure. (b)
Selectivity graph of Cu-MOF′: CO2 and N2 at 298 K and 1 atm pressure.
room temperature to get the cyclic carbonates, and the analysis of the
conversion was completed through H NMR spectroscopy.
linkers are further connected to two such windows in a
staggered fashion leading to Cu6(CO2)12 polyhedra based
secondary building blocks (SBBs) (Figure S8). This polyhedral
is present with spherical cages having an internal diameter of
approximately 12.061(1) Å2 (distance denotes Cu-to-Cu
linking and discounting the DMF coordination) that can be
accessed through its square and triangular faces (Figure S9).
Six SBBs are interconnected in the packing structures of Cu-
MOF along the crystallographic c-axis. This results in the
formation of a supramolecular 3D framework (Figure 2c). This
complete framework possesses uniform one-dimensional
channels of 10.956(0) Å, in diameter (Figure 2d), which is
occupied by disordered solvent molecules. These lattice as well
as coordinated solvent molecules was treated by SQUEEZE
refinement of PLATON54 to check the effective solvent
accessible void volume, which was found to be ∼40% (Å3) per
unit cell. In Cu-MOF′, the lactam decorated and metal
exposed channels may offer supplementary pathways for CO2
insertion and are suitable for heterogeneous catalytic CO2
fixation.
Thermal Stability and PXRD. The intense peaks of as-
synthesized sample obtained in the powder X-ray diffraction
(PXRD) method matches well with the simulated pattern
obtained from single crystal X-ray diffraction, confirming the
phase purity of the bulk sample of Cu-MOF (Figure S10).
Also, the PXRD patterns of the as-synthesized, acetone
exchanged, and activated samples are well matched, confirming
the framework integrity toward the process of solvent exchange
and activation (Figure S11). Further, the thermal stability of
the as-synthesized Cu-MOF and acetone exchanged samples
are verified by variable temperature powder X-ray diffraction
(VTPXRD) measurements (Figure S12).
Gas Adsorption and Catalytic CO2 Fixation. First, we
activated the acetone-exchanged Cu-MOF followed by heating
at 150 °C under high vacuum for 8 h to yield the fully activated
Cu-MOF′. The porosity of Cu-MOF′ has been established at
1 bar pressure and 77 K temperature by nitrogen adsorption
(Figure 3a). The N2 adsorption isotherm exhibited a maximum
N2 uptake of 65.37 cm3 g−1. We have further checked the
adsorption studies for the CO2 at 1 bar pressure and 195 K as
well as 298 K. As shown in Figure 3a, the CO2 adsorption
isotherms exhibited a maximum uptake of 34.14 cm3 g−1 at 298
K and 108.22 cm3 g−1 at 195 K. The adsorption studies of CO2
and N2 at 298 K were also investigated, and it was observed
that the CO2 adsorption isotherm presented type 1 behavior
illuminating its microporous assembly with saturation
1
RESULTS AND DISCUSSION
■
The previously reported Cu-MOF55 was synthesized in a facile
manner by employing rigid lactam functionalized ditopic
ligand (H2L) and Cu(NO3)2·3H2O at room temperature
under slow evaporation conditions {H2L = (5-(1-oxo-2,3-
dihydro-1H-inden-2-yl)isophthalic acid)} (Scheme 1). An
earlier report shows it was synthesized through solvothermal
conditions and report only its structural description.
Compared to that, here a cost-effective synthetic protocol
has been applied. The stability of Cu-MOF in common organic
solvents and air was further authenticated by recording unit
cell parameters by employing single-crystal X-ray diffraction
studies, and no changes were observed which was also
validated by elemental analysis. Powder X-ray diffraction
patterns obtained from the bulk samples approves the phase
purity and framework integrity of this Cu-MOF. Lattice water
molecules present can be seen by the broad peak in the range
of 3600−3200 cm−1 in the IR spectra (Figure S7) of Cu-MOF.
The strong peaks observed at 1568 and 1412 cm−1 correspond
to coordinated carboxylate groups,56 whereas the peaks at 1631
and 1665 cm−1 correspond to coordinated DMF molecules
and the presence of a lactam ring, respectively.57,58
Figure 1 shows the SEM images of the Cu-MOF at different
magnifications (100, 30, and 20 μm) and confirming the block
shaped morphology of Cu-MOF.
Structural Analysis. The single-crystal X-ray diffraction
study shows that Cu-MOF is crystallized in the trigonal crystal
system with an R-3 space group (Table S1). One unit each of
H2L, Cu(II) ion, and coordinated DMF molecule (Figure 2a)
are present in the asymmetric unit of Cu-MOF, where
distorted square pyramidal geometry is exhibited by the
Cu(II) ion with four different carboxylate linkers providing
four O atoms [Cu···O, 1.922(4)−2.110(7)Å] and the fifth O
atom originates from the DMF molecule [Cu···O, 1.922(4)Å].
The extension of this asymmetric unit results in the formation
of a framework consisting of {[Cu2(CO2)4]·2DMF} secondary
building units (SBUs) of a paddle-wheel shape (Figure 2b).
Further, a π−π stacking interaction is observed between the
two adjacent linkers and act as tetra-carboxylate moieties, i.e.,
pseudotetra-carboxylate linkers (Figure 2b). A closer view
shows the connection of three isophthalate units of the
pseudotetra-carboxylate linker by three SBUs with the creation
of a triangular shaped window. Three pseudotetracarboxylate
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adsorption of 34.14 cm3 g−1 (6.71 wt %) whereas the N2
adsorption isotherm displays its maximum uptake of 4.64 cm3
g−1 (0.29 wt %) (Figure 3b). The above results confirm the
good selectivity of CO2 over the N2 adsorption for Cu-MOF′.
Further, the pore size distribution analysis demonstrates
(Figure S13) that pores are of an average diameter of 11.32
Å and is in good accordance with the measured pore size.
The selective CO2 adsorption, large pore volume with
lactam functionalized channels, good thermal stability, and the
exposed Cu(II) sites in the activated framework encourage us
to examine its catalytic activity for chemical fixation of CO2 to
cyclic carbonates. The present study was concerned with the
cycloaddition reaction of CO2 with epoxides (20 mmol) by
using activated Cu-MOF′ (5 wt %) as a catalyst along with
tetrabutyl ammonium bromide (TBAB) (1 mmol) as a
cocatalyst at 30 and 70 °C (based on the boiling point of
the epoxides) for 10 h (Scheme 2).
conditions for 15 h and found that maximum conversion was
achieved after 10 h (Figure 4a and Figure S15). Once we got
the reaction time, we examined several reactions at different
catalyst and cocatalyst loadings and found that the optimum
conversion was obtained at 5 wt % of catalyst and 1 mmol of
cocatalyst (Figure 4b, Figure S16 and Figure 4c, Figure S17).
Also, to study the effect of the other halides, we performed the
optimized reaction with tetrabutyl ammonium chloride
(TBAC) (1 mmol) and tetrabutyl ammonium iodide (TBAI)
(1 mmol) (Table 1, entries 17 and 18) and found that TBAB
exhibited good conversion relative to the others (Figure S18).
To extend the synthetic scope of the CO2 fixation for cyclic
carbonates syntheses, a variety of epoxides (Figure 5) viz.
glacidyl phenyl ether (E2), benzyl glycidyl ether (E3), 1,2-
butylene oxide (E4), and 1,2-epoxy hexane (E5) were used
under the same reaction conditions as for the model reaction,
except a slight change in temperatures from 30 °C for E3 and
E4 and 70 °C for E2 and E5. The evaluation of corresponding
1
Scheme 2. Cycloaddition Reaction of CO2 with Epoxides
Catalyzed by Cu-MOF′
product conversions was achieved from the H NMR spectra
by integration of epoxide versus cyclic carbonate peaks
(Figures S19−S22) and found that 79%, 86%, >99%, and
>99% conversion was observed for E2, E3, E4, and E5,
respectively (Table 1, entries 4, 7, 10, and 13). Interestingly, as
the molecular sizes of epoxide substrates increases, a steady
decrease in the conversion of cyclic carbonates was observed,
possibly due to the lower diffusion into the Cu6(CO2)12
polyhedral cages of Cu-MOF′.59,60
The cycloaddition reaction of CO2 with styrene oxide (E1)
as a model substrate was examined in the presence of Cu-
MOF′ and TBAB at 70 °C for 10 h and afforded 92% product
Furthermore, in the absence of catalyst, no conversion was
observed in the model reaction (Table 1, entry 16), while
utilization of Cu-MOF′ catalyst and TBAB cocatalyst
independently resulted in a 23% and 8% conversion (Table
1, entries 2 and 3), respectively (Figure S23). Further, this
controlled experiments was performed with other epoxy
1
conversion (Table 1, entry 1), as confirmed by H NMR
(Figure S14). Further, we optimized the reaction conditions on
the influence of reaction time and catalyst and cocatalyst
amounts. First we carried out the reaction at the above
a
Table 1. Cycloaddition of CO2 and Various Epoxides
b
entry no.
epoxide
catalyst
temperature (°C)
time (h)
10
conversion (%)
1
2
3
Cu-MOF′ + TBAB
Cu-MOF′
92
23
8
E1
70
TBAB
4
5
6
Cu-MOF′ + TBAB
Cu-MOF′
79
15
6
E2
E3
E4
E5
70
30
30
70
10
10
10
10
TBAB
7
8
9
Cu-MOF′ + TBAB
Cu-MOF′
86
21
7
TBAB
10
11
12
Cu-MOF′ + TBAB
Cu-MOF′
>99
36
13
TBAB
13
14
15
Cu-MOF′ + TBAB
Cu-MOF′
>99
26
15
TBAB
16
17
18
E1
E1
E1
−
TBAI
TBAC
70
70
70
10
10
10
0
35
55
a
b
1
Reaction conditions: epoxide (20 mmol), catalyst (5 wt %), TBAB (1 mmol). Conversion was evaluated from the H NMR spectra by
integration of epoxide versus cyclic carbonate peaks.
E
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Figure 4. Showing the optimized (a) reaction time in hours, (b) catalyst loading in wt %, and (c) TBAB loading in millimoles.
Figure 5. Various epoxides used in the CO2 cycloaddition reaction.
compounds (Table 1, entries 5, 6, 8, 9, 11, 12, 14, and 15)
suggested that the presence of both the Cu-MOF′ catalyst and
TBAB cocatalyst are essentially required for the conversion of
epoxide to cyclic carbonate, where TBAB is acting as a
nucleophile and facilitates the opening of the epoxide
rings.61,62 Conversion of epoxides into corresponding cyclic
carbonate in each case were evaluated by H NMR (Figures
S24−S27).
1
Figure 7. Showing the hot-filtration experiment, confirming the
heterogeneous nature of Cu-MOF.
To check the recyclability of Cu-MOF′ catalyst, the model
reaction mixture was filtered after the completion of the
reaction to isolate the catalyst which was further washed with
chloroform and acetone (3 mL and five times by each) and
dried at 150 °C under high vacuum to regain the active
catalyst. Further, the recyclability experiments were checked by
utilizing the regenerated catalyst in the subsequent run and
found that the catalytic activity is similar for each run until four
consecutive cycles (Figure 6a). The PXRD patterns of the
catalyst after each catalytic cycle is shown in Figure 6b, which
displayed that the framework integrity is maintained after four
catalytic cycles. Furthermore, the heterogeneous nature of the
Cu-MOF′ was examined by the hot filtration experiment,
where the model reaction mixture was filtered after 2 h to
separate out the catalyst. Subsequently, only a slight increment
in the conversion of styrene oxide was observed, suggesting the
true heterogeneous nature (Figure 7). Also, ICP-MS analysis
(Table S3) of the filtrate after the fourth cycle (0.45 ppm)
ruled out the possibility of leaching of Cu(II) ions from Cu-
MOF′ into solution, further confirming the heterogeneous
nature of Cu-MOF.
Finally, a circumstantial table has been introduced to
compare the catalytic CO2 fixation of Cu-MOF′ with various
MOFs (Table 2) exhibiting the excellent or comparable
catalytic activity of Cu-MOF′. Here, we are comparing the
catalytic conversion of the styrene oxide (E1) and butylene
oxide (E4) as well as the reaction conditions and times. The
percent conversion value is higher or comparable to these
MOFs, such as MOF-Zn-1 (E1, 54%),25 1Zn (E1, 51.3%),26
Cu-MOF (E1, 69%),40 Ba-MOF (E1, 19.8%),41 WM-MOF
(E1, 99%),48 VPI-100-Ni (E4, 50%),49 [Co(tp)(bpy)] (E1,
95.02%),63 MOF1 (E1, 80.8%),64 InDCPN-Cl (E1, 86%),65
and TMOF-1 (E1, >99%)66 measured at different temper-
Figure 6. Recycling test of Cu-MOF′ (a) for successive cycles of cycloaddition of CO2 with styrene oxide and (b) PXRD of Cu-MOF after each
cycle.
F
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Table 2. Comparison of Catalytic Performance with MOFs as Heterogeneous Catalytic Materials Towards Cycloaddition of
CO2 with Epoxides
entry
no.
time
MOF (M)
[LCu] (Cu)
linker
epoxide temerature (°C)/pressure (bar) (h) conversion (%)/yield (%)
ref
24
1
2′-amino-1,1′:4′,1″-terphenyl-
3,3′′,5,5′′-tetracarbox-ylic acid
E1
120/20
12
50/−
2
3
[MOF-Zn-1] (Zn)
[1] (Zn)
2,5-thiophenedicarboxylic acid
tricarboxytriphenyl amine + 1,3-
bis(imidazol-1-ylmethyl)benzene
E1
E1
80/3
80/1
3
4
−/54
51.3/−
25
26
4
5
6
[Cu-MOF] (Cu)
[Ba-MOF] (Ba)
[WM-MOF] (Zr)
H4DAIA
E1
E1
E1
100/1
30/48
60/30
4
48
30
69/−
19.8/−
99/−
40
41
48
N,N′-bis(isophthalic acid)-oxalamide
nickel-tetrakis(4-carboxyphenyl)-
porphyrin
7
8
[VPI-100-Cu] (Zr)
[VPI-100-Ni] (Zr)
6,13-dicarboxy-1,4,8,11-
tetraazacyclotetradecane)-
copper(II) perchlorate
6,13-dicarboxy-1,4,8,11-
tetraazacyclotetradecane)- nickel(II)
perchlorate
E4
E4
90/10
60/10
6
6
60/−
50/−
49
49
9
10
[Co(tp)(bpy)] (Co) terephthalic acid + 4, 4′-bipyridine
E1
E1
100/1 (MPa)
80/0.1 (MPa)
7
9
95.02/93.12
80.8/−
63
64
[MOF1] (Co)
1,2,4,5-tetrakis(4-carboxyphenyl)
benzene)
11
12
[InDCPN-Cl] (In)
[TMOF-1] (Cu)
5-(3′,5′-dicarboxylphenyl)nicotinic
disodium 1,2-ethanedisulfonate +
4,4′-bipyridine
E1
E4
80/1
RT/1
24
−
86/−
−/>99
65
66
13
14
[Cu-MOF] (Cu)
[Cu-MOF] (Cu)
5-(1-oxo-2,3-dihydro-1H-inden-2-yl)
E1
E4
70/1
70/1
10
10
92/−
this
isophthalic acid
work
5-(1-oxo-2,3-dihydro-1H-inden-2-yl)
isophthalic acid
>99/−
this
work
Scheme 3. Proposed Reaction Mechanism for the Cycloaddition of CO2 with Epoxides Catalyzed by Cu-MOF′
atures and pressures. The excellent catalytic activity of Cu-
MOF′ toward CO2 cycloaddition with epoxides elucidates its
believability as a promising candidate for CO2 fixation under
mild conditions.
Proposed Mechanism for Cycloaddition of CO2 with
Epoxide Catalyzed by Cu-MOF′. Based on the earlier
reports, we found that a binary catalytic system, i.e., Lewis acid
catalyst and a nucleophilic cocatalyst (TBAB) is usually
engaged in an effective cycloaddition reaction of CO2 with
epoxides.62 Here, the Cu-MOF′ with unsaturated Lewis acidic
Cu(II) centers and TBAB act as a binary catalytic system. The
proposed catalytic mechanism of CO2 cycloaddition with
epoxides is shown in Scheme 3, where the epoxidic oxygen are
coordinated with an unsaturated Lewis acid Cu(II) center.
Further, the Br− anion of TBAB attacks as a nucleophile which
leads to the epoxide ring opening to form metal coordinated
bromo-alkoxide, which is a considerable rate-determining
step.41,67 Subsequently, CO2 insertion takes place between
G
DOI: 10.1021/acs.inorgchem.9b00684
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
metal alkoxide and forming a metal carbonate species which
further leads to cyclic carbonate undergoing an intramolecular
ring closure. The metal center eliminates the cyclic carbonate
which regenerates the active catalyst and makes the catalytic
cycle reversible.
facilities. P.M. gratefully acknowledges the J. C. Bose National
Fellowship. S.N.A. expresses thanks to MHRD, the Govern-
ment of India, and IIT Indore for the Ph.D. fellowship. P.K.
thanks IIT Indore for the Master’s Program. A.K.G. expresses
thanks to IIT Indore for a postdoctoral research fellowship. We
further acknowledge Prof. J. N. Moorthy and Ms. Chetna
Yadav, Department of Chemistry, IIT Kanpur, for their help in
the gas adsorption measurement.
CONCLUSION
■
In summary, we report the facile synthesis of a lactam
functionalized Cu(II) ion based porous 3D metal−organic
framework, Cu-MOF. The framework possesses 1D lactam
decorated channels along with exposed Cu(II) metal centers
after activation of Cu-MOF. The synergistic effect of lactam
decorated pores with open metal sites was studied toward the
cycloaddition reaction of CO2 with epoxides. Further, the
activated Cu-MOF′ exhibits fascinating solvent-free heteroge-
neous catalytic conversion of CO2 to cyclic carbonates in at
atmospheric pressure of CO2, under mild conditions with good
recyclability and reusability. This work demonstrates the new
possibilities for designing Lewis acids/bases incorporating
MOFs for efficient conversion of CO2 into cyclic carbonates in
a more economically viable way.
REFERENCES
■
(1) Aresta, M.; Dibenedetto, A.; Angelini, A. Catalysis for the
Valorization of Exhaust Carbon: from CO2 to Chemicals, Materials,
and Fuels. Technological Use of CO2. Chem. Rev. 2014, 114, 1709−
1742.
(2) Yin, H.; Mao, X.; Tang, D.; Xiao, W.; Xing, L.; Zhu, H.; Wang,
D.; Sadoway, D. R. Capture and electrochemical conversion of CO2 to
value-added carbon and oxygen by molten salt electrolysis. Energy
Environ. Sci. 2013, 6, 1538−1545.
(3) Liu, J.; Thallapally, P. K.; McGrail, B. P.; Brown, D. R.; Liu, J.
Progress in adsorption-based CO2 capture by metal−organic
frameworks. Chem. Soc. Rev. 2012, 41, 2308−2322.
(4) Cheng, M.; Lobkovsky, E. B.; Coates, G. W. Catalytic Reactions
Involving C1 Feedstocks: New High-Activity Zn(II)-Based Catalysts
for the Alternating Copolymerization of Carbon Dioxide and
Epoxides. J. Am. Chem. Soc. 1998, 120, 11018−11019.
(5) Sakakura, T.; Choi, J.-C.; Yasuda, H. Transformation of carbon
dioxide. Chem. Rev. 2007, 107, 2365−2387.
(6) Lin, S.; Diercks, C. S.; Zhang, Y. B.; Kornienko, N.; Nichols, E.
M.; Zhao, Y.; Paris, A. R.; Kim, D.; Yang, P.; Yaghi, O. M.; Chang, C.
J. Covalent organic frameworks comprising cobalt porphyrins for
catalytic CO2 reduction in water. Science 2015, 349, 1208−1213.
(7) North, M.; Pasquale, R.; Young, C. Synthesis of cyclic carbonates
from epoxides and CO2. Green Chem. 2010, 12, 1514−1539.
(8) Sumida, K.; Rogow, D. L.; Mason, J. A.; McDonald, T. M.;
Bloch, E. D.; Herm, Z. R.; Bae, T.; Long, J. R. Carbon dioxide capture
in metal−organic frameworks. Chem. Rev. 2012, 112, 724−781.
(9) Verma, S.; Kumar, G.; Ansari, A.; Kureshy, R. I.; Khan, N. H. A
nitrogen rich polymer as an organo-catalyst for cycloaddition of CO 2
to epoxides and its application for the synthesis of polyurethane.
Sustainable Energy Fuels 2017, 1, 1620−1629.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.9b00684.
■
S
Crystallographic table of bond length and angles,
synthetic procedure of the H2L linker and its character-
ization through 1H NMR, 13C NMR and ESI-MS, FT-IR
of Cu-MOF, PXRD and variable temperature PXRD
plots for the Cu-MOF, crystallographic figures, 1H NMR
spectra of cycloaddition reactions of CO2 with different
substrates as well as optimized reaction, ICP-MS data,
and pore size distribution plot (PDF)
Accession Codes
CCDC 1904186 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
(10) Bayardon, J.; Holz, J.; Schaffner, B.; Andrushko, V.; Verevkin,
S.; Preetz, A.; Borner, A. Propylene carbonate as a solvent for
asymmetric hydrogenations. Angew. Chem., Int. Ed. 2007, 46, 5971−
5974; Angew. Chem. 2007, 119, 6075−6078.
(11) Liu, H.; Huang, Z.; Han, Z.; Ding, K.; Liu, H.; Xia, C.; Chen, J.
Efficient production of methanol and diols via the hydrogenation of
cyclic carbonates using copper−silica nanocomposite catalysts. Green
Chem. 2015, 17, 4281−4290.
AUTHOR INFORMATION
Corresponding Authors
*E-mail: xray@iiti.ac.in. Phone: +91 7312438752.
*E-mail: director@iiti.ac.in.
■
(12) Unnikrishnan, P.; Srinivas, D. Highly active and reusable
ternary oxide catalyst for dialkyl carbonates synthesis. J. Mol. Catal. A:
Chem. 2015, 398, 42−49.
(13) Fujita, S.; Bhanage, B. M.; Kanamaru, H.; Arai, M. Synthesis of
1, 3-dialkylurea from ethylene carbonate and amine using calcium
oxide. J. Mol. Catal. A: Chem. 2005, 230, 43−48.
ORCID
Shaikh M. Mobin: 0000-0003-1940-3822
Author Contributions
(14) Kim, S. H.; Hong, S. H. Transfer hydrogenation of organic
formates and cyclic carbonates: an alternative route to methanol from
carbon dioxide. ACS Catal. 2014, 4, 3630−3636.
+Shagufi Naz Ansari and Pawan Kumar contributed equally to
the work.
(15) Wang, X.; Zhou, Y.; Guo, Z.; Chen, G.; Li, J.; Shi, Y.; Liu, Y.;
Wang, J. Heterogeneous conversion of CO2 into cyclic carbonates at
ambient pressure catalyzed by ionothermal-derived meso-macro-
porous hierarchical poly(ionic liquid)s. Chem. Sci. 2015, 6, 6916−
6924.
(16) Roshan, K. R.; Kim, B. M.; Kathalikkattil, A. C.; Tharun, J.;
Won, Y. S.; Park, D. W. The unprecedented catalytic activity of
alkanolamine CO 2 scrubbers in the cycloaddition of CO2 and
oxiranes: a DFT endorsed study. Chem. Commun. 2014, 50, 13664−
13667.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
S.M.M. acknowledges DST-SERB, New Delhi (Project No.
EMR/2016/001113), CSIR, New Delhi (Project No.
01(2935)/18/EMR-II), and Indian Institute of Technology
Indore (IIT Indore) for financial support and Sophisticated
Instrumentation Centre (SIC) for the characterization
H
DOI: 10.1021/acs.inorgchem.9b00684
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(17) Zhang, Z.; Fan, F.; Xing, H.; Yang, Q.; Bao, Z.; Ren, Q.
Efficient Synthesis of Cyclic Carbonates from Atmospheric CO2
Using a Positive Charge Delocalized Ionic Liquid Catalyst. ACS
Sustainable Chem. Eng. 2017, 5, 2841−2846.
(34) Rajak, R.; Saraf, M.; Mohammad, A.; Mobin, S. M. Design and
construction of a ferrocene based inclined polycatenated Co-MOF for
supercapacitor and dye adsorption applications. J. Mater. Chem. A
2017, 5, 17998−18011.
(18) Liu, M.; Lu, X.; Jiang, Y.; Sun, J.; Arai, M. Zwitterionic
Imidazole-Urea Derivative Framework Bridged Mesoporous Hybrid
Silica: A Highly Efficient Heterogeneous Nanocatalyst for Carbon
Dioxide Conversion. ChemCatChem 2018, 10, 1860−1868.
(19) Bousquet, B.; Martinez, A.; Dufaud, V. Zinc−Azatrane
Complexes as Efficient Catalysts for the Conversion of Carbon
Dioxide into Cyclic Carbonates. ChemCatChem 2018, 10, 843−848.
(20) Xue, Z.; Zhao, X.; Wang, J.; Mu, T. Bifunctional Boron
Phosphate as an Efficient Catalyst for Epoxide Activation to
Synthesize Cyclic Carbonates with CO2. Chem. - Asian J. 2017, 12,
2271−2277.
(21) Liu, M.; Gao, K.; Liang, L.; Sun, J.; Sheng, L.; Arai, M.
Experimental and theoretical insights into binary Zn-SBA-15/KI
catalysts for the selective coupling of CO2 and epoxides into cyclic
carbonates under mild conditions. Catal. Sci. Technol. 2016, 6, 6406−
6416.
(22) Wang, S.; Wang, X. Imidazolium Ionic Liquids, Imidazolylidene
Heterocyclic Carbenes, and Zeolitic Imidazolate Frameworks for CO2
Capture and Photochemical Reduction. Angew. Chem., Int. Ed. 2016,
55, 2308−2320.
(23) Patel, P.; Parmar, B.; Kureshy, R. I.; Khan, N.; Suresh, E.
Efficient Solvent-Free Carbon Dioxide Fixation Reactions with
Epoxides Under Mild Conditions by Mixed-Ligand Zinc (II)
Metal−Organic Frameworks. ChemCatChem 2018, 10, 2401−2408.
(24) De, D.; Pal, T. K.; Neogi, S.; Senthilkumar, S.; Das, D.; Gupta,
S. S.; Bharadwaj, P. K. A Versatile CuII Metal−Organic Framework
Exhibiting High Gas Storage Capacity with Selectivity for CO2:
Conversion of CO2 to Cyclic Carbonate and Other Catalytic Abilities.
Chem. - Eur. J. 2016, 22, 3387−3396.
(25) Lan, J.; Liu, M.; Lu, X.; Zhang, X.; Sun, J. Novel 3D Nitrogen-
Rich Metal Organic Framework for Highly Efficient CO2 Adsorption
and Catalytic Conversion to Cyclic Carbonates under Ambient
Temperature. ACS Sustainable Chem. Eng. 2018, 6, 8727−8735.
(26) Yao; Zhou, S.; Kang, X.; Zhao, Y.; Yan, R.; Zhang, Y.; Wen, L.
A Cationic Zinc−Organic Framework with Lewis Acidic and Basic
Bifunctional Sites as an Efficient Solvent-Free Catalyst: CO2 Fixation
and Knoevenagel Condensation Reaction. Inorg. Chem. 2018, 57,
11157−11164.
(27) Kathalikkattil, A. C.; Roshan, R.; Tharun, J.; Babu, R.; Jeong, G.
S.; Kim, D. W.; Cho, S. J.; Park, D. W. A sustainable protocol for the
facile synthesis of zinc-glutamate MOF: an efficient catalyst for room
temperature CO2 fixation reactions under wet conditions. Chem.
Commun. 2016, 52, 280−283.
(28) Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. The
chemistry and applications of metal-organic frameworks. Science 2013,
341, 1230444.
(35) Hall, J. N.; Bollini, P. Structure, characterization, and catalytic
properties of open-metal sites in metal organic frameworks. React.
Chem. Eng. 2019, 4, 207−222.
(36) Gupta, A. K.; De, D.; Tomar, K.; Bharadwaj, P. K. A Cu(II)
metal−organic framework with significant H2 and CO2 storage
capacity and heterogeneous catalysis for the aerobic oxidative
amination of C(sp3)−H bonds and Biginelli reactions. Dalton Trans
2018, 47, 1624−1634.
(37) Martín, C.; Fiorani, G.; Kleij, A. W. Recent Advances in the
Catalytic Preparation of Cyclic Organic Carbonates. ACS Catal. 2015,
5, 1353−1370.
(38) He, H. M.; Perman, J. A.; Zhu, G. S.; Ma, S. Q. Metal-Organic
Frameworks for CO2 Chemical Transformations. Small 2016, 12,
6309−6324.
(39) Klankermayer, J.; Wesselbaum, S.; Beydoun, K.; Leitner, W.
Selective catalytic synthesis using the combination of carbon dioxide
and hydrogen: catalytic chess at the interface of energy and chemistry.
Angew. Chem., Int. Ed. 2016, 55, 7296−7343.
(40) Maity, K.; Karan, C. K.; Biradha, K. Porous Metal-Organic
Polyhedral Framework containing Cuboctahedron Cages as SBUs
with High Affinity for H2 and CO2 Sorption: A Heterogeneous
Catalyst for Chemical Fixation of CO2. Chem. - Eur. J. 2018, 24,
10988−10993.
(41) Li, X. Y.; Ma, L. N.; Liu, Y.; Hou, L.; Wang, Y. Y.; Zhu, Z.
Honeycomb Metal−Organic Framework with Lewis Acidic and Basic
Bifunctional Sites: Selective Adsorption and CO2 Catalytic Fixation.
ACS Appl. Mater. Interfaces 2018, 10, 10965−10973.
(42) Gao, W. Y.; Chen, Y.; Niu, Y.; Williams, K.; Cash, L.; Perez, P.
J.; Wojtas, L.; Cai, J.; Chen, Y. S.; Ma, S. Q. Crystal Engineering of an
nbo Topology Metal−Organic Framework for Chemical Fixation of
CO2 under Ambient Conditions. Angew. Chem. 2014, 126, 2653−
2657.
(43) Li, P. Z.; Wang, X. J.; Liu, J.; Lim, J. S.; Zou, R. Q.; Zhao, Y. L.
A Triazole-Containing Metal−Organic Framework as a Highly
Effective and Substrate Size-Dependent Catalyst for CO2 Conversion.
J. Am. Chem. Soc. 2016, 138, 2142−2145.
(44) Lu, X. B.; Darensbourg, D. J. Cobalt catalysts for the coupling
of CO2 and epoxides to provide polycarbonates and cyclic carbonates.
Chem. Soc. Rev. 2012, 41, 1462−1484.
(45) Sopena, S.; Fiorani, G.; Martin, C.; Kleij, A. W. Highly Efficient
Organocatalyzed Conversion of Oxiranes and CO2 into Organic
Carbonates. ChemSusChem 2015, 8, 3248−3254.
(46) Zhu, M. Q.; Carreon, M. A. Porous crystals as active catalysts
for the synthesis of cyclic carbonates. J. Appl. Polym. Sci. 2014, 131,
39738−39750.
(29) Li, H.; Wang, K.; Sun, Y.; Lollar, C. T.; Li, J.; Zhou, H. C.
Recent advances in gas storage and separation using metal−organic
frameworks. Mater. Today 2018, 21, 108−121.
(47) Markewitz, P.; Kuckshinrichs, W.; Leitner, W.; Linssen, J.;
Zapp, P.; Bongartz, R.; Schreiber, A.; Muller, T. E. Worldwide
̈
innovations in the development of carbon capture technologies and
the utilization of CO2. Energy Environ. Sci. 2012, 5, 7281−7305.
(48) He, T.; Ni, B.; Xu, X.; Li, H.; Lin, H.; Yuan, W.; Luo, J.; Hu,
W.; Wang, X. Competitive Coordination Strategy to Finely Tune Pore
Environment of Zirconium-Based Metal−Organic Frameworks. ACS
Appl. Mater. Interfaces 2017, 9, 22732−22738.
(30) Gupta, A. K.; De, D.; Bharadwaj, P. K. A NbO type Cu (II)
metal−organic framework showing efficient catalytic activity in the
̈
Friedlander and Henry reactions. Dalton Trans 2017, 46, 7782−7790.
(31) Gupta, A. K.; Tomar, K.; Bharadwaj, P. K. Cd(II) coordination
polymers constructed with a flexible carboxylate linker and pyridyl co-
linkers: variation in the network topologies and photoluminescence
properties. CrystEngComm 2017, 19, 2253−2263.
(49) Zhu, J.; Usov, P. M.; Xu, W.; Celis-Salazar, P. J.; Lin, S.;
Kessinger, M. C.; Landaverde-Alvarado, C.; Cai, M.; May, A. M.;
Slebodnick, C.; Zhu, D.; Senanayake, S. D.; Morris, A. J. A New Class
of Metal-Cyclam-Based Zirconium Metal−Organic Frameworks for
CO2 Adsorption and Chemical Fixation. J. Am. Chem. Soc. 2018, 140,
993−1003.
(50) Yuan, S.; Zou, L. F.; Li, H. X.; Chen, Y. P.; Qin, J. S.; Zhang,
Q.; Lu, W. G.; Hall, M. B.; Zhou, H. C. Flexible Zirconium Metal-
Organic Frameworks as Bioinspired Switchable Catalysts. Angew.
Chem., Int. Ed. 2016, 55, 10776−10780.
(32) Gupta, A. K.; De, D.; Katoch, R.; Garg, A.; Bharadwaj, P. K.
Synthesis of a NbO Type Homochiral Cu(II) Metal−Organic
Framework: Ferroelectric Behavior and Heterogeneous Catalysis of
Three-Component Coupling and Pechmann Reactions. Inorg. Chem.
2017, 56, 4697−4705.
(33) Chen, Y.; Li, P.; Modica, J. A.; Drout, R. J.; Farha, O. K. Acid-
Resistant Mesoporous Metal−Organic Framework toward Oral
Insulin Delivery: Protein Encapsulation, Protection, and Release. J.
Am. Chem. Soc. 2018, 140, 5678−5681.
I
DOI: 10.1021/acs.inorgchem.9b00684
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(51) Corma, A.; García, H.; LlabresiXamena, F. X. Engineering
metal organic frameworks for heterogeneous catalysis. Chem. Rev.
2010, 110, 4606−4655.
(52) Lee, H. M.; Youn, S.; Saleh, M.; Lee, J. W.; Kim, K. S.
Interactions of CO2 with various functional molecules. Phys. Chem.
Chem. Phys. 2015, 17, 10925−10933.
(53) Sheldrick, G. M. A short history of SHELX. Acta Crystallogr.,
Sect. A: Found. Crystallogr. 2008, 64, 112−122.
(54) Spek, A. L. Single-crystal structure validation with the program
PLATON. J. Appl. Crystallogr. 2003, 36, 7−13.
(55) Ye, R. P.; Zhang, X.; Zhang, L.; Zhang, J.; Yao, Y. G. Solvent
and pH driven self-assembly of isomeric or isomorphic complexes:
Crystal structure and luminescent change upon desolvation. Cryst.
Growth Des. 2016, 16, 4012−4020.
(56) Gupta, A. K.; Tomar, K.; Bharadwaj, P. K. Structural diversity
of Zn(II) based coordination polymers constructed from a flexible
carboxylate linker and pyridyl co-linkers: fluorescence sensing of
nitroaromatics. New J. Chem. 2017, 41, 14505−14515.
(57) Ahmad, M.; Das, R.; Lama, P.; Poddar, P.; Bharadwaj, P. K.
Synthesis, Characterization, and Magnetic Studies of Coordination
Polymers with Co (II) and Mn (II) Ions. Cryst. Growth Des. 2012, 12,
4624−4632.
(58) Chaturvedi, D.; Chaturvedi, A.; Mishra, N.; Mishra, V. Efficient,
One-Pot, BF3· OEt2-Mediated Synthesis of Substituted N-Aryl
Lactams. Synlett 2012, 23, 2627−2630.
(59) Gao, W. Y.; Chen, Y.; Niu, Y.; Williams, K.; Cash, L.; Perez, P.
J.; Wojtas, L.; Cai, J.; Chen, Y. S.; Ma, S. Crystal Engineering of an
nbo Topology Metal−Organic Framework for Chemical Fixation of
CO2 under Ambient Conditions. Angew. Chem., Int. Ed. 2014, 53,
2615−2619.
(60) Babu, R.; Roshan, R.; Kathalikkattil, A. C.; Kim, D. W.; Park, D.
W. Rapid, Microwave-Assisted Synthesis of Cubic, Three-Dimen-
sional, Highly Porous MOF-205 for Room Temperature CO2 Fixation
via Cyclic Carbonate Synthesis. ACS Appl. Mater. Interfaces 2016, 8,
33723−33731.
(61) Beyzavi, M. H.; Stephenson, C. J.; Liu, Y.; Karagiaridi, O.;
Hupp, J. T.; Farha, O. K. Metal−organic framework-based catalysts:
chemical fixation of CO2 with epoxides leading to cyclic organic
carbonates. Front. Energy Res. 2015, 2, 63−72.
(62) Zhu, M.; Srinivas, D.; Bhogeswararao, S.; Ratnasamy, P.;
Carreon, M. A. Catalytic activity of ZIF-8 in the synthesis of styrene
carbonate from CO2 and styrene oxide. Catal. Commun. 2013, 32,
36−40.
(63) Song, X.; Wu, Y.; Pan, D.; Zhang, J.; Xu, S.; Gao, L.; Wei, R.;
Zhang, J.; Xiao, G. Dual-linker metal-organic frameworks as efficient
carbon dioxide conversion catalysts. Appl. Catal., A 2018, 566, 44−51.
(64) Dhankhar, S. S.; Nagaraja, C. M. Construction of a 3D porous
Co(II) metal-organic framework (MOF) with Lewis acidic metal sites
exhibiting selective CO2 capture and conversion at mild conditions.
New J. Chem. 2019, 43, 2163−2170.
(65) Yuan, Y.; Li, J.; Sun, X.; Li, G.; Liu, Y.; Verma, G.; Ma, S.
Indium−Organic Frameworks Based on Dual Secondary Building
Units Featuring Halogen-Decorated Channels for Highly Effective
CO2 Fixation. Chem. Mater. 2019, 31, 1084−1091.
(66) Zhang, G.; Wei, G.; Liu, Z.; Oliver, S. R. J.; Fei, H. A Robust
Sulfonate-Based Metal−Organic Framework with Permanent Porosity
for Efficient CO2 Capture and Conversion. Chem. Mater. 2016, 28,
6276−6281.
(67) Li, X. Y.; Li, Y. Z.; Yang, Y.; Hou, L.; Wang, Y. Y.; Zhu, Z.
Efficient light hydrocarbon separation and CO2 capture and
conversion in a stable MOF with oxalamide-decorated polar tubes.
Chem. Commun. 2017, 53, 12970−12973.
J
DOI: 10.1021/acs.inorgchem.9b00684
Inorg. Chem. XXXX, XXX, XXX−XXX