Metal-Organic Frameworks of Cu(II) Constructed from Functionalized Ligands for High Capacity H2 and CO2 Gas Adsorption and Catalytic Studies

Article abstract of DOI:10.1021/acs.inorgchem.9b03012

Two Cu(II)-based metal-organic frameworks (MOFs) having paddle-wheel secondary building units (SBUs), namely, 1_Me and 1_ipr, were synthesized solvothermally using two new bent di-isophthalate ligands incorporating different substituents. The MOFs showed high porosity (BET surface area, 2191 m²/g for 1_Me and 1402 m²/g for 1_ipr). For 1_Me, very high CO₂ adsorption (98.5 wt % at 195 K, 42.9 wt % at 273 K, 23.3 wt % at 298 K) at 1 bar was found, while for 1_ipr, it was significantly less (14.3 wt % at 298 K and 1 bar, 54.4 wt % at 298 K at 50 bar). 1_Me exhibited H₂ uptake of 3.2 wt % at 77 K and 1 bar of pressure, which compares well with other benchmark MOFs. For 1_ipr, the H₂ uptake was found to be 2.54 wt % under similar experimental conditions. The significant adsorption of H₂ and CO₂ for 1_Me could be due to the presence of micropores as well as unsaturated metal sites in these MOFs besides the presence of substituents that interact with the gas molecules. The experimental adsorption behavior of the MOFs could be justified by theoretical calculations. Additionally, catalytic conversions of CO₂ and CS₂ into useful chemicals like cyclic carbonates, cyclic trithiocarbonates, and cyclic dithiocarbonates could be achieved.

Full text of DOI:10.1021/acs.inorgchem.9b03012

pubs.acs.org/IC
Article
Metal−Organic Frameworks of Cu(II) Constructed from
Functionalized Ligands for High Capacity H2 and CO2 Gas
Adsorption and Catalytic Studies
Mayank Gupta, Nabanita Chatterjee, Dinesh De, Ranajit Saha, Pratim Kumar Chattaraj,*
Clive L. Oliver,* and Parimal K. Bharadwaj*
Cite This: https://dx.doi.org/10.1021/acs.inorgchem.9b03012
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: Two Cu(II)-based metal−organic frameworks (MOFs) having paddle-wheel secondary building units (SBUs),
namely, 1Me and 1ipr, were synthesized solvothermally using two new bent di-isophthalate ligands incorporating different
substituents. The MOFs showed high porosity (BET surface area, 2191 m2/g for 1Me and 1402 m2/g for 1ipr). For 1Me, very high
CO2 adsorption (98.5 wt % at 195 K, 42.9 wt % at 273 K, 23.3 wt % at 298 K) at 1 bar was found, while for 1ipr, it was significantly
less (14.3 wt % at 298 K and 1 bar, 54.4 wt % at 298 K at 50 bar). 1Me exhibited H2 uptake of 3.2 wt % at 77 K and 1 bar of pressure,
which compares well with other benchmark MOFs. For 1ipr, the H2 uptake was found to be 2.54 wt % under similar experimental
conditions. The significant adsorption of H2 and CO2 for 1Me could be due to the presence of micropores as well as unsaturated
metal sites in these MOFs besides the presence of substituents that interact with the gas molecules. The experimental adsorption
behavior of the MOFs could be justified by theoretical calculations. Additionally, catalytic conversions of CO2 and CS2 into useful
chemicals like cyclic carbonates, cyclic trithiocarbonates, and cyclic dithiocarbonates could be achieved.
Previously, we reported a porous Cu(II)-MOF built with the
tetra-acid linker (Scheme 1a) that afforded a porous structure
with paddle-wheel secondary building units (SBUs) and having
free amine groups in the channels that exhibited a H2
adsorption of 6.6 wt % at 77 K and 62 bar of pressure besides
very high CO2 adsorption (60 wt %) at 298 K.5 Later on, the
linker was modified with the introduction of OMe, CF3, and
NH2 groups on opposite sides of the central aromatic ring
(Scheme 1b,c) to probe their possible influence in the gas
adsorption behavior.6 The Cu(II)-MOF with the linker shown
in Scheme 1b afforded 34.2 wt % CO2 at 273 K and negligible
H2 adsorption, while with the linker shown in Scheme 1c, it
INTRODUCTION
■
Metal−organic frameworks (MOFs) are an emerging class of
hybrid porous materials. Due to their structural and functional
tunability, easy synthesis, as well as their ever-expanding scopes
of practical applications, MOFs have become one of the most
pursued classes of materials.1 The most important aspect is the
fact that the overall structure and porosity in these materials
can be systematically varied and fine-tuned through the choice
of both metal ions and organic ligands.2 Particularly,
functionalization of MOFs with the polar functional group
(NH2, NO2, Cl, Br, CO2H, OCH3, or SO3H)3 enhances their
adsorption performances for various gases (mainly H2, CO2,
and CH4) besides developing their heterogeneous catalytic
potential. The coordination space that can be rendered
hydrophobic if alkyl or fluorinated (CH3, CF3) groups are
present in the linkers could help in retaining gas adsorption
efficiency even under moist conditions.4
Received: October 12, 2019
https://dx.doi.org/10.1021/acs.inorgchem.9b03012
© XXXX American Chemical Society
Inorg. Chem. XXXX, XXX, XXX−XXX
A

Inorganic Chemistry
pubs.acs.org/IC
Article
like pharmaceuticals and dyes, as an electrolyte in Li+ ion
batteries, as polar aprotic solvents, as intermediates for the
synthesis of ethylene glycol, as polymeric materials, as a
precursor of polycarbonates, etc.10 The cycloaddition products
with CS2, e.g., dithiocarbonates and trithiocarbonates, are used
in radioprotective studies,11 polymer syntheses,12 and making
different insecticides.13
Scheme 1. Schematic Diagram of Various Tetra-Acid
Linkers
EXPERIMENTAL SECTION
■
Materials. Cu(NO3)2·3H2O and other reagent grade chemicals
were purchased from commercial suppliers (Sigma-Aldrich, Alfa
Aesar, an TCI) and were used as received. All the solvents were
acquired from S. D. Fine Chemicals, India. These solvents were
purified following standard protocols prior to use.
Physical Measurements. All spectroscopic data were collected as
described earlier.5 Prior to the gas sorption analysis, the as-
synthesized MOFs were kept in dry acetone and then heated at
120 °C under a high vacuum for 12 h to get rid of all the solvent
molecules from the cavity. A Micromeritics 3Flex Surface Area
Analyzer was used for all gas and water vapor sorption experiments.
Sample preparation was achieved using a Micromeritics Flowprep
with a constant flow of N2 gas over the sample at 60 °C for 4 h.
Afterward, the sample was heated first at 100 °C under a vacuum for 2
h followed by another hour of heating at 120 °C before the analysis
commenced. The Brunauer−Emmett−Teller (BET) method was
applied to data points with the slope of the Roquerol BET graph
remaining positive.
X-ray Structural Studies. A Bruker SMART CCD diffractometer
with graphite monochromated Mo Kα radiation (λ = 0.71073 Å) at
100 K was used for all data collections. The data collection, data
reduction, structure solution, and refinements were carried out as
described earlier.5 The solvent molecules present in the structures
were highly disordered. To tackle this, the PLATON-SQUEEZE14
program was used and the number of solvent molecules calculated
based on TGA and elemental analyses. The crystal data are shown in
Table S1, and selected bond distances and angles are collected in
Table S2.
Computational Details. We have analyzed the H2 and CO2 gas
storage capacity of the synthesized MOFs in terms of the results from
related computational studies. In order to reduce the computational
cost, we have extracted and simplified the MOF structure from the
associated experimental crystallographic data in such a way that all
relevant interactions were kept intact. We studied the adsorption of
H2 and CO2 gas molecules at different positions of the model
complex. All of the structures were optimized using DFT-based
ωB97x-D15 functional in conjunction with the TZVP basis set.
Frequency calculations were done at the same level of theory on the
optimized structures. All real frequency values ensured that the
optimized structures were at the minima on their respective potential
energy surfaces. The Gaussian 09 suite of program package16 was
used. The binding energy (BE) per gas molecule and Gibbs’ free
energy changes (ΔG) per gas molecule for both of the gas storage
processes have been computed as
exhibited 35.5 wt % CO2 at 273 K and 1.72 wt % H2 at 77 K
and 1 bar of pressure. To probe the possible effects of electron
donating methyl and isopropyl groups (Scheme 1d,e), the
linkers H4L1 and H4L2 were synthesized and used to
synthesize two Cu(II)-MOFs solvothermally. All the Cu(II)-
MOFs built with the linkers shown in Scheme 1 were iso-
structural with copper paddle-wheel-based SBUs (Schemes 2
and 3) having highly porous and water stable architectures,
allowing a comparative study of gas adsorption to be made.
The significant adsorption of CO2 and H2 could be attributed
to not only micropores and unsaturated metal sites formed in
these MOFs but also enhanced interactions of functional
groups with the gas molecules.7
Inspired by the excellent CO2 sorption by the activated 1Me,
its usefulness as a heterogeneous catalyst in the cycloaddition
reactions between various epoxides and CO2 or CS2 at 1.0 atm
were probed. Catalytic conversion of carbon dioxide (CO2)
and carbon disulfide (CS2) into useful chemicals like cyclic
carbonates and cyclic tri- and dithiocarbonates is important for
the effective utilization of harmful CO2 and CS2.8 The
synthesis of cyclic carbonates by reacting an epoxide with
CO2 is a profitable reaction.9 With the use of this reaction, this
greenhouse gas can be reduced significantly. Also, the product
cyclic carbonates in this reaction are useful in several industries
Scheme 2. Synthesis of the MOF, 1Me
B
https://dx.doi.org/10.1021/acs.inorgchem.9b03012
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
Scheme 3. Synthesis of the MOF, 1ipr
Scheme 4. Synthetic Route for the Ligand, H4L1
1
n
ΔEint = ΔEpauli + ΔEel + ΔEorb + ΔEdisp
(3)
BE = ((nEGas + EMOF) − EnGas@MOF
)
(1)
(2)
The ΔEpauli represented the repulsion between the electrons having
same spin in the occupied orbitals of the interacting fragments. The
ΔEel term presented the quasi-classical electrostatic interaction energy
between the fragments under consideration. In general, the ΔEel term
was attractive in nature. Another attractive energy contribution was
from the orbital interaction energy, ΔEorb, originating from the charge
transfer, mixing of the occupied and unoccupied orbitals between the
fragments, and the polarization effect. The term ΔEdisp represented
the dispersion energy correction toward the total attraction energy.
To analyze the nature of noncovalent interactions present in the H2
and CO2 adsorbed MOFs, an atoms-in-molecules (AIM)25 analysis
had been performed. Several density based parameters were
computed at the ωB97x-D/TZVP level of theory to find out the
nature of the interactions. These calculations were done using
Multiwfn software.26
1
n
ΔG = ((nGGas + GMOF) − GnGas@MOF
)
where the E and G are the computed electronic energies and Gibbs’
free energies of the optimized geometries respectively. The value of n
is 21 for H2 and 12 for the CO2 gas adsorbed MOFs. The
thermochemical parameters had been computed at 298 K temperature
and 1 atm pressure.
The charge (q) on each atomic center was computed by natural
population analysis (NPA),17 and the Wiberg bond index (WBI)18
between two atoms was calculated as per the natural bond orbital
(NBO) scheme19 at the ωB97x-D/TZVP level using NBO 3.120 as
implemented in Gaussian 09. An ultrafine grid, with 99 radial shells
per atom, and 950 angular points per shell, had been used throughout
the computations.
The NCIPLOT software27,28 was used to evaluate the noncovalent
interactions between the guest gas molecules and the host MOF. The
NCI analysis was based on the electron density (ρ) and its reduced
density gradient (s) as
The energy decomposition analysis (EDA)21 was performed at the
SSB-D22/TZP//ωB97x-D/TZVP level of theory using the ADF
2013.01 program package.23,24 The SSB-D functional with Grimme’s
dispersion correction was reported to be suitable in representing weak
interactions. In the EDA scheme, the interaction energy (ΔEint) is
decomposed into four energy terms, viz., the Pauli repulsion (ΔEpauli),
the electrostatic interaction energy (ΔEel), the orbital interaction
energy (ΔEorb), and the dispersion interaction energy (ΔEdisp), as
1
|∇ρ|
2(3π2)1/3 ρ4/3
where ∇ρ is the gradient of ρ.
s =
(4)
C
https://dx.doi.org/10.1021/acs.inorgchem.9b03012
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
Figure 1. (a) Coordination environment around Cu2+ ions in 1Me and (b) spherical cages in 1Me
.
A weak, noncovalent interaction between the molecular pairs could
be identified by the low ρ and low s values. The Laplacian of electron
density (∇2ρ(r)) was a parameter for describing the nature of the
interaction between the molecular pairs. But, the ∇2ρ(r) index solely
could not distinguish between different types of noncovalent
interactions (hydrogen bonds, steric interactions, van der Waals’
(vdW) interactions) by itself. The eigenvalues λi of the electron
density Hessian (second derivative) matrix such that ∇2ρ(r) = λ1 + λ2
+ λ3 (λ1 < λ2 < λ3) were useful to identify various noncovalent
interactions. As for H bonds, λ2 < 0; for steric interactions, λ2 > 0, and
for vdW type of interactions, λ2 ≲ 0. Thus, s was plotted against
sign(λ2)ρ(r) (product of sign(λ2) and ρ(r)). The positions of the
troughs associated with the reduced density gradient (s(ρ(r)))
appearing in the 2D plot give an idea about the type of the
noncovalent interaction. The real space intermolecular interaction iso-
surface was generated using VMD visualization package.29
C46H74N8O19Cu2: C, 47.21; H, 6.37; N, 9.57%. Found: C, 46.30; H,
6.73; N, 9.49%.
Thermal Stability and Activation of the Compounds, 1Me
and 1ipr. The bulk phase purity of the materials could be confirmed
by matching their powder X-ray diffraction patterns (Figures S20 and
S21) with those of crystallographically characterized samples. The
thermogravimetric analysis showed a gradual loss of lattice solvent
molecules from 50 °C onward, and decomposition of the compounds
could be achieved only beyond 400 °C (Figure S22). The
thermograms of the acetone exchanged samples exhibited a loss of
solvent molecules up to 100 °C. Thereafter, no loss of weight could
be observed up to 400 °C (Figures S23), suggesting robustness of the
structures. High thermal stability of the compounds was also
confirmed by the variable temperature PXRD measurements, showing
the frameworks as stable at least up to 200 °C (Figures S20 and S21).
Before gas sorption measurements and catalytic studies (for 1Me), the
as-synthesized samples were activated as mentioned above to afford
a1Me and a1ipr.
General Procedure for the Cycloaddition of CO2 to
Epoxides. An epoxide (20 mmol), catalyst a1Me (10 wt %), and
cocatalyst TBAB (1 mmol) were added to a Schlenk tube at room
temperature with bubbling CO2 (99.999%). Once the reaction was
completed as found by TLC, the catalyst was filtered out, washed with
5 mL of DCM, and air-dried. The product was purified by silica gel
column chromatography and characterized by 1H NMR spectroscopy.
In a similar way, the conversion of atmospheric CO2 into cyclic
carbonate was carried out. We purged the laboratory air as a CO2
source, and the mixture was allowed to stir for 24 h.
SYNTHESIS
■
Synthesis of the Ligand 2′-Amino-5′-methyl-[1,1′:3′,1″-
terphenyl]-3,3″,5,5″-tetracarboxylic Acid (H4L1). Synthesis of
the ligand H4L1 was completed in several steps following a published
procedure,1b as illustrated in Scheme 4. The precursor 2′-amino-5′-
methyl-[1,1′:3′,1″-terphenyl]-3,3″,5,5″-tetracarboxylic ester (H4L1
ester) was characterized by X-ray crystallography (Figure S4), with
Table S3 showing the crystal and refinement data.
Synthesis of the Ligand 2′-amino-5′-isopropyl-[1,1′:3′,1″-
terphenyl]-3,3″,5,5″-tetracarboxylic Acid (H4L2). Synthesis of
the ligand H4L2 was likewise completed in multiple steps following a
similar procedure as above using p-isopropyl aniline in place of p-
methyl aniline (Scheme S2). Synthetic details for H4L1 and H4L2 are
provided in the Supporting Information.
Synthesis of {[Cu2(L1)(H2O)2]·(6DMF)(3H2O)}n (1Me). A sol-
ution of Cu(NO3)2·3H2O (22 mg, 0.092 mmol) and H4L1 (20 mg,
0.046 mmol) in 2 mL of DMF and 1 mL of H2O was placed in a
Teflon-lined stainless steel autoclave. It was heated under autogenous
pressure to 90 °C for 3 days and then allowed to cool to room
temperature. Blue crystals of 1Me in the form of rectangular
parallelopipeds were filtered, washed with DMF followed by
methanol, and finally dried in the air. Yield ∼ 23 mg (45%), based
on the ligand H4L1. FTIR (KBr pellets; cm−1): 3314 (b), 2920 (w),
1690 (m), 1630 (s) 1570 (s), 1467 (w), 1423 (s), 1365 (s), 919 (m),
863(w), 780 (m), 722 (m), 646 (m), 468 (m) (Figure S19a). Anal.
Calcd for C41H65N7O19Cu2: C, 45.29; H, 6.03; N, 9.01%. Found: C,
44.16; H, 6.41; N, 8.96%.
General Procedure for the Synthesis of Cyclic Trithiocar-
bonates. Carbon disulfide (40 mmol), an epoxide (20 mmol),
catalyst a1Me (10 wt %), and cocatalyst TBAB (1 mmol) were placed
in a sealed pressure tube and stirred at 0, 30, or 80 °C. After
completion of the reaction, it was filtered, and the filtrate was
evaporated off. The product was passed with a short plug of silica
using ethyl acetate as the eluent and analyzed by 1H NMR
spectroscopy.
RESULTS AND DISCUSSION
■
Solvothermal reactions between H4L1 or H4L2 with Cu-
(NO3)2 in the mixed solvent system of DMF and H2O gave
blue-colored crystals of 1Me and 1ipr, respectively. On the basis
of single-crystal X-ray diffraction analysis in addition to thermal
(TGA, Figures S22−24) and elemental analyses, these
compounds were formulated as {[Cu2(L1)(H2O)2]·6DMF·
3H2O)}n, 1Me, and {[Cu2(L2)(H2O)2]·7DMF·2H2O)}n, 1ipr.
Both the compounds crystallized in the space group P63/mmc
with the asymmetric unit comprising one-fourth of the ligand
besides a Cu(II) ion and a coordinated water molecule, each
with half occupancy. As expected from an isophthalate moiety,
Synthesis of {[Cu2(L2)(H2O)2]·(7DMF)(2H2O)}n (1ipr). A similar
procedure as above was followed using H4L2 (20 mg, 0.043 mmol) in
lieu of H4L1. Yield ∼ 22 mg (43%), based on the ligand H4L2. FTIR
(KBr pellets; cm−1): 3443 (b), 2961 (w), 1655 (s), 1572(w),
1432(m), 1369 (s), 1250(w), 1230 (w) 1103 (w), 1069 (w) 922 (w),
783 (m), 727 (m), 657 (w), 482 (m) (Figure S19b). Anal. Calcd For
D
https://dx.doi.org/10.1021/acs.inorgchem.9b03012
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
Figure 2. (a) Coordination environment around Cu2+ ions in 1ipr and (b) spherical cages in 1ipr.
the structure in 1Me or 1ipr was composed of paddle-wheel
[Cu2(COO)4] secondary building units (SBUs) with carbox-
ylate bridging. (The Cu···Cu bond distance was 2.650(3) and
2.6551(15) Å in 1Me and 1ipr, respectively; Figures 1a and 2a.)
The Cu−O bond distances were in the range 1.949(6) to
2.087(11) Å for 1Me and 1.950(6) to 2.124(6) Å for 1ipr,
forming an overall three-dimensional framework. These and
other bond distances were within normal statistical errors as
found in the literature. The overall structures of the present
two compounds were quite similar to those with other linkers
shown in Scheme 1. As depicted in Figures 1b and 2b, two
types of voids of spherical shape were found with approximate
diameters of 10 Å (yellow color) and 8 Å (violet color). These
were further connected to each other via small triangular
windows of dimensions ∼5 Å. The bigger void was in close
proximity with the alkyl substituent, while the smaller void had
−NH2 groups. Disordered solvent molecules occupied these
voids whose number was established from the weight-loss in
Figure 3. N2 physisorption isotherm of 1Me at 77 K.
the thermogram, elemental, and IR spectral analyses. The
sharp peaks at 1630 and 1655 cm−1 in the IR spectra (Figure
S19) of 1Me and 1ipr, respectively, were consistent with the C
O stretching vibration of the lattice DMF molecules. All these
experimental data were in good agreement with the PLATON
calculated solvent-accessible void volume, which was found to
be 61.3% (4335/7068.2 Å3) for 1Me and 57% (4037/7076.3
Å3) for 1ipr of the total cell volume.
Gas Adsorption Studies for 1Me. The permanent porosity
in a1Me was established by nitrogen adsorption experiments at
77 K. As shown in Figure 3, it exhibited a reversible type I
sorption behavior, revealing its microporous nature with a
maximum N2 uptake of 568 cm3(STP) g−1 at 1 bar,
corresponding to the BET surface area of 2191 m2g−1.
The high permanent porosity, presence of open metal sites,
and more importantly the presence of free amine/methyl
groups prompted us to carry out CO2 adsorption measure-
ments. We have carried out the measurements at different
temperatures (Figure 4). The CO2 measurement results are
summarized in Table 1.
The CO2 adsorption capacities of a1Me (Figure 4 and Table
1) at 195, 273, 278, 283, 288, 293, and 298 K were found to be
502 cm3 g−1 (98.5 wt %), 219 cm3 g−1 (42.9 wt %), 199 cm3
g−1 (39.0 wt %), 183 cm3 g−1 (35.8 wt %), 171 cm3 g−1 (33.6
wt %), 146 cm3 g−1 (28.7 wt %), and 119 cm3 g−1 (23.3 wt %),
respectively. These high uptake capacities compared well with
some of the MOFs known for CO2 adsorbing ability (Table
S4). At zero loading, the Qst value calculated using the
Figure 4. Physisorption isotherms: CO2 at 195 to 298 K for a1Me
.
Clausius−Clapeyron equation was 26.63 kJ mol−1, indicative of
a favorable interaction of CO2 with the host framework (Figure
5). For the process to calculate heat of CO2 adsorption from
the Clausius−Clapeyron equation, see the SI.
The ability of a1Me to adsorb H2 gas at 77 K had also been
carried out, with the results shown in Figure 6. The gas uptake
reached about 355 cm3 (STP) g−1, corresponding to 3.2 wt %
at a pressure of 1.07 bar. The adsorption and desorption follow
E
https://dx.doi.org/10.1021/acs.inorgchem.9b03012
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
Table 1. CO2 Gas Sorption Results for 1Me
CO2, 195 K, 0.95 bar
CO2, 273 K, 1.04 bar
CO2, 278 K, 1.07 bar
CO2, 283 K, 1.12 bar
CO2, 288 K, 1.22 bar
CO2, 293 K, 1.14 bar
CO2, 298 K, 1.06 bar
502 cm3 g−1 (98.5 wt %)
219 cm3 g−1 (42.9 wt %)
199 cm3 g−1 (39.0 wt %)
183 cm3 g−1 (35.8 wt %)
171 cm3 g−1 (33.6 wt %)
146 cm3 g−1 (28.7 wt %)
119 cm3 g−1 (23.3 wt %)
Figure 7. Physisorption isotherms: N2 at 77 K for a1ipr.
The CO2 adsorption capacity of a1ipr up to 1 bar of pressure
(Figure 8) at 298 K was found to be 73 cm3 (STP) g−1 (14.3
Figure 5. Isosteric heat of adsorption for CO2 (Qst) for in a1Me
.
Figure 8. Physisorption isotherms: CO2 at 298 K at 1 bar pressure for
a1ipr.
wt %), which was significantly less than the value obtained in
the case of a1Me. This could be attributed to the larger size of
the isopropyl group compared to the methyl group reducing
the available space.
Figure 6. Physisorption isotherms: H2 at 77 K (a1Me).
the same path without hysteresis. Noticeably, the hydrogen
uptake value was higher than those of MOF-5 (2.0%), MOF-
505 (2.47%), Cu-BTT (2.42%), Fe-BTT (2.3%), PCN-68
(1.87%), PCN-66 (1.79%), SNU-4 (2.07%), MOF-74(Mg)
(2.2%), and LCu (2.57% and 1.72%) by Bharadwaj et al.30,6b
and many among the NOTT measured at 1 bar of pressure
(Table S5).
The structure of 1ipr was isostructural with 1Me. The only
difference was 1ipr had an isopropyl group in place of the
methyl group. The permanent porosity in 1ipr was established
by N2 adsorption experiments at 77 K. As shown in Figure 7,
a1ipr exhibited a maximum N2 uptake of 491 cm3 (STP) g−1 at
1 bar, corresponding to the BET surface area of 1402 m2g−1.
We also compared the CO2 gas sorption in isostructural
MOFs at 298, 1 bar. When there is a methyl group, it is
showing the highest uptake (119 cm3 g−1), while when there is
no group, the uptake was moderate (90 cm3 g−1; Table 2). But
when the methyl group is replaced by a triflouromethyl group,
the uptake was reduced to 106 cm3 g−1. The trifluoromethyl
group is electron withdrawing in nature, while the methyl
group is electron donating, which increases the electron
density at the amino group, leading to a favorable interaction
with gas molecules. One should also notice that the
trifluoromethyl group is bulkier than the methyl group,
which can also lead to a decrease in gas sorption. But when
the bulkier trifluoromethyl group was replaced by a smaller
F
https://dx.doi.org/10.1021/acs.inorgchem.9b03012
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
Table 2. Comparison of CO2 Gas Sorption at 298 K, 1 Bar in Isostructural MOFs
fluoride group, no change in the gas sorption uptake was
observed (Table 2). This shows that the size of the methyl
group is appropriate at this pore size. The trifluoromethyl and
fluoride groups showed more gas sorption when there was no
group because of their favorable interactions with the gas
molecule.
An attempt to increase the electron density at the amino
group by replacing the methyl group with an isopropyl group
leads to less gas uptake (73 cm3 g−1). In this case, the bulkiness
of the isopropyl group as compared to the methyl group causes
inferior results. Hence, from the above observation, it can be
concluded that the stereoelectronics are responsible for higher
gas sorption.
molecules in the paddle-wheel of the MOFs had been studied
earlier and explained.32−34 The H2 molecules were placed in
these preferred binding sites and optimized. Two H2 molecules
resided near each of the Cu atoms of the MOFs. The Cu−H
bond lengths were in the range of 2.312−2.315 Å for all of the
H2 gas adsorbed MOFs. In these gas adsorbed MOFs, the H−
H bond lengths of the two H2 molecules close to the Cu atoms
were elongated to 0.750 Å compared to 0.744 Å in the free H2
molecule (see Table S6). The remaining H2 molecules were
distributed over the Cu-paddle and aromatic linkers. The
elongation in the H−H bond was small in these H2 molecules
compared to free H2 molecules (see Table S6). A similar type
of scenario was present in case of the CO2 adsorbed MOFs.
Two Cu atoms were found to be bound with two CO2
molecules showing Cu−O interactions. The Cu−O distances
were in the range 2.403−2.425 Å for all of the MOFs (see
Table S7). The C−O1 bond distance (1 referred to the O
close to the Cu atom) in CO2 was increased, whereas the other
one (C−O2 bond) was shortened as compared to free CO2.
For the remaining CO2 molecules, the elongation was very
small. The O1−C−O2 bond angle was bent in the adsorbed
form for all CO2 molecules. As we could see for the H2 as well
as for the CO2 gas molecules, the change in the structural
parameters was very small. Hence, physisorption of these gases
was expected in the case of all the MOFs.
The ability of a1ipr to adsorb H2 gas at 298 K up to a
pressure of 1 bar has also been carried out, and the results are
shown in Figure 9. The gas uptake reaches about 284.6 cm3
(STP) g−1, corresponding to 2.54 wt % up to a pressure of 1
bar.
The binding energy per gas molecule (BE) and the Gibbs’
free energy change per gas molecule (ΔG, kcal/mol) were
computed and are presented in Table S8. The BE values were
the same for a particular gas in case of the 1Me, as well as for
the 1ipr and 1CF3. The H2 and CO2 storage capacity could be
explained in terms of the ΔG values. The ΔG values for both
of the CO2 adsorbed MOFs were the same, which supports
almost equal CO2 storage capacity in the MOFs at 298.15 K
and 1 atm. For the H2 desorption process, the ΔG value for
1Me was −4.9 kcal/mol; for 1ipr, −5.0 kcal/mol; and for 1CF3
,
−5.1 kcal/mol. Thus, the high H2 gas storage in 1Me and 1ipr as
compared to the 1CF3 was thermochemically supported. The
computational results were in conformity with those obtained
from related experiments.
Figure 9. Physisorption isotherms: H2 at 77 K (a1ipr).
In the EDA scheme, we had considered three fragmentation
processes as shown in Table S9. In the first scheme, two gas
molecules near the two Cu centers were considered as one
fragment, and the remaining part (n−2)gas@MOF was
considered as the other fragment. In the second fragmentation
process, we had considered the two nearby gas molecules near
the Cu atoms and the MOF, i.e., 2gas@MOF, as one fragment,
and the remaining (n−2) gas molecules as another fragment.
In the last fragmentation process, we had considered the MOF
as one fragment and all of the n gas molecules as the second
fragment. For all of the fragmentation processes, the
The gas adsorption selectivity for both the frameworks was
measured31 according to the ideal adsorbed solution theory
(IAST) at 273 K up to 1 bar of pressure using single-
component adsorption isotherms for CO2, H2, and N2 (Figure
10). From the Figure, it was clear that the amounts of N2 and
H2 uptake were negligibly small, whereas a1Me and a1ipr
adsorbed significant amounts of CO2. For a1Me, the selectivity
of CO2 over N2 was found to be 43, while it was 24 for a1ipr.
Computational Study. The optimized geometries of the
MOFs and H2 and CO2 adsorbed MOFs presented in Figure
11 with the −CH3, −iPr, and −CF3 substitution in the
aromatic linker represented as 1Me, 1ipr, and 1CF3, respectively,
in this study. The preferred binding sites for the H2 gas
contributions from the noncovalent interactions (ΔEelstat
+
ΔEdisp) were more than the covalent interaction (ΔEorb). The
two gas molecules near the Cu atoms were mainly stabilized by
G
https://dx.doi.org/10.1021/acs.inorgchem.9b03012
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
Figure 10. CO2, H2, and N2 absorption isotherm for a1Me (left) and a1ipr (right) at 273 K.
Figure 11. Optimized geometries of all the structures at the ωB97x-D/TZVP level of theory.
the ΔEelstat (49.1−58.7%), which was followed by the ΔEorb
(28.6−40.3%) and ΔEdisp (10.5−17.7%) as per the first
fragmentation way. For the remaining (n−2) gas molecules,
the ΔEdisp contributes 42.0−45.4% toward the total stabiliza-
tion energy, becoming the major stabilizing factor for these gas
molecules as per the second fragmentation procedure. Overall,
it was clear that the noncovalent interactions (ΔEelstat and
ΔEdisp) were the major stabilizing factor compared to the
ΔEorb.
The molecular graphs of the H2 and CO2 adsorbed MOFs
had been generated at the wB97x-D/TZVP level and presented
in Figure S25. Large numbers of bond paths cropped up
between different atoms of the MOFs and gas molecules,
indicating all of the interactions in these gas adsorbed MOF
systems. The computed density based descriptors at the bond
H
https://dx.doi.org/10.1021/acs.inorgchem.9b03012
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
Figure 12. Plot of (a) the NCI isosurface for 21H2@1Me. The iso-surface is generated for s = 0.5 au and (b) the reduced density gradient (s) versus
sign(λ2)ρ for 21H2@1Me
.
Figure 13. Plot of (a) the NCI isosurface for 12H2@ 1ipr. The iso-surface is generated for s = 0.5 au and (b) the reduced density gradient (s) versus
sign(λ2)ρ for 12H2@ 1ipr.
critical points (BCP) are presented in Table S10. We had
considered only one of each kind of BCP for the discussion.
The electron density (ρ(rc)) values were low at the BCPs
originating between the adsorbed gas molecules and MOFs.
The low ρ(rc), positive Laplacian of the electron density
(∇2ρ(rc)), and positive energy density (H(rc)) at the BCP
indicated noncovalent type interactions present between the
gas molecules and MOFs. The NCI plots for all of these gas
adsorbed MOF systems have been presented in Figures 12, 13,
S26, and S27. The generated green surface between the gas
and MOFs surface indicated the origin of van der Waals
interaction among them. The 2-D plot showed the generation
of a green area near the electron density equal to zero,
indicating all of the interactions between the MOF surface and
gas molecules. The H2 and CO2 near the Cu atom had their
finger prints near the region of sign(λ2)ρ(r) ≈ −0.021 to
−0.028, which almost coincided with the Cu−Cu interaction
in the paddle-wheel.
The results obtained from the NBO analysis for the H2 and
CO2 adsorbed MOF systems have been presented in Table
S11 and Table S12, respectively. The charges on the Cu atoms
in 1Me are 1.093 and 1.094 |e|, in 1ipr are 1.093 and 1.094 |e|,
and in 1CF3 are 1.093 and 1.093 |e|. On H2 adsorption, the
charges on the Cu atoms decreased to 1.045 for 1Me, 1.045 for
1ipr, and 1.046 and 1.045 for 1CF3. The two H2 molecules near
the Cu atoms had a positive charge on them. This signified a
transfer of electron density from the H2 molecules to the Cu
centers. The remaining H2 molecules in the vicinity of the
I
https://dx.doi.org/10.1021/acs.inorgchem.9b03012
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
aromatic linkers were polarized, which was the origin of the
vdW force. The total charges on the two CO2 molecules near
the two Cu atoms were 0.048 and 0.044 |e| in 12CO2@1Me and
0.045 and 0.044 |e| in 12CO2@1ipr and 0.046 and 0.044 |e| in
12CO2@1CF3, respectively. This accumulation of positive
charge on CO2 with a concomitant decrease of the charge
on both the Cu atoms indicated that electron density donation
occurred from CO2 toward the MOFs. The remaining 10 CO2
molecules were polarized. The Cu−H and Cu−O(CO2) WBI
values were low, supporting the noncovalent type of
interactions. The WBIH−H values in the adsorbed H2 molecules
were slightly smaller compared to those in the free H2
molecules. A similar picture was found for the WBIC−O in
the adsorbed CO2 molecules.
Catalytic Studies. Cycloaddition of CO2 to Different
Epoxides. High CO2 adsorption ability with significant heat of
adsorption for a1Me convinced us to attempt to fix adsorbed
CO2 as cyclic carbonates by reacting with different epoxides. In
a typical experiment, an epoxide (20 mmol), catalyst a1Me (10
wt %), and cocatalyst TBAB (1 mmol) were placed in a
Schlenk tube with stirring at room temperature, and CO2
(99.999%) was allowed to bubble into the reaction mixture.
The catalyst system was quite versatile, as structurally different
epoxides could be converted to the corresponding cyclic
carbonates in excellent yields (Table 3).
dichloromethane. No further reaction occurred when the
filtrate was allowed to react under the same reaction conditions
(Figure S28). To check the reusability of the catalyst, it was
collected by filtration, washed with CH2Cl2, and dried under a
vacuum at 120 °C for 5 h and used for the second run using
the same reactants. The catalyst could be reused without any
noticeable loss of activity (Figure S29) and crystallinity (Figure
S30) at least up to four cycles. The yields in four runs were
almost the same. Formation of the desired carbonate was
1
confirmed by its H NMR (Figures S31−S35). High yields of
the desired products in these reactions under mild conditions
may be due to high accessibility of the empty Cu(II)
coordination sites where an epoxide could easily bind.
We then attempted bubbling of laboratory air into the
reaction mixture of an epoxide, TBAB, and the catalyst a1Me,
taken in the same proportion as above for 24 h at room
temperature. The results were quite interesting (Table 4), and
a significant amount of the product could be isolated this way.
Table 4. Cycloaddition Reactions by Bubling Laboratory Air
for 24 h into the Reaction Mixture at 298 K
To confirm the heterogeneous nature of the reaction, a hot
filtration technique was adopted. The reaction using
epichlorohydrin as the substrate was stopped by hot filtration
of the catalyst at partial conversion (∼50%) after dilution with
Table 3. Cycloaddition of CO2 and Various Epoxides
a
Catalyzed by a1Me in the Presence of TBAB
Cycloaddition of CS2 to Epoxides. We next attempted to
catalyze the reaction between an epoxide and CS2 in the
presence of 1Me. The reaction was performed in a sealed
pressure tube using an epoxide (20 mmol), CS2 (40 mmol),
catalyst a1Me (10 wt %), and the cocatalyst TBAB (1 mmol) at
different temperatures under solvent free conditions. At 0 °C,
after 12 h, two major products could be isolated after
purification through silica chromatography and characterized
as a mixture of cyclic dithiocarbonate and trithiocarbonate
1
through H NMR. On increasing the temperature to 30 °C,
still the mixture was obtained. On further increasing the
temperature to 80 °C, thin-layer chromatography (TLC)
showed a single major spot, which was passed through a short
plug of silica using CH2Cl2 as an eluent and characterized by
1H NMR (Figures S36−S40) and matched with the reported
literature,35 which confirmed the formation of exclusive cyclic
trithiocarbonate (Table 5). In some cases, crystals appeared
after some time. X-ray structure data were also collected for
those crystals, which confirmed the presence of cyclic
trithiocarbonate (Figure S41). The probable mechanism28 is
a
provided in Figure S42. A heterogeneous nature (Figure S43)
and recyclability (Figures S44 and S45) were also confirmed as
in the case of cyclic carbonates.
a
b
Catalyzed by 1Me only. Catalyzed by the cocatalyst TBAB alone.
J
https://dx.doi.org/10.1021/acs.inorgchem.9b03012
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
Kharagpur, Kharagpur 721302, India; Email: pkc@
chem.iitkgp.ac.in
Table 5. Cycloaddition of CS2 and Various Epoxides
Catalyzed by a1Me
Clive L. Oliver − Centre for Supramolecular Chemistry Research
(CSCR), Department of Chemistry, University of Cape Town,
Cape Town, South Africa; orcid.org/0000-0001-7946-
6492; Email: clive.oliver@uct.ac.za
Parimal K. Bharadwaj − Department of Chemistry, Indian
Institute of Technology Kanpur, Kanpur 208016, India;
Department of Chemistry, Indian Institute of Technology
Bombay, Mumbai 400076, India; orcid.org/0000-0003-
3347-8791; Email: pkb@iitk.ac.in
Other Authors
Mayank Gupta − Department of Chemistry, Indian Institute of
Technology Kanpur, Kanpur 208016, India
Nabanita Chatterjee − Centre for Supramolecular Chemistry
Research (CSCR), Department of Chemistry, University of Cape
Town, Cape Town, South Africa
Dinesh De − Department of Basic Science, Vishwavidyalaya
Engineering College, Lakhanpur, Sarguja University, Lakhanpur
497116, India
Ranajit Saha − Department of Chemistry and Center for
Theoretical Studies, Indian Institute of Technology Kharagpur,
Kharagpur 721302, India
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.inorgchem.9b03012
CONCLUSIONS
■
Two 3D Cu(II)-MOFs were synthesized solvothermally with
two new tetra-acid ligands and characterized by single crystal
X-ray diffraction. Each structure had a metal-bound aqua
ligand in addition to a number of solvent molecules in the
voids. All these could be removed upon heating without a
breakdown of the 3D architecture, leading to highly porous
structures. The amino group remained uncoordinated in the
voids, which along with uncoordinated metal centers exhibited
very high H2 and CO2 adsorption by the MOFs. With activated
1Me, the adsorbed CO2 could be easily fixed as a cyclic
carbonate on reacting with an epoxide at room temperature in
the presence of TBAB as the cocatalyst. Even CO2 from
laboratory air could be fixed this way. Conversion of
carbondisulfide (CS2) into cyclic trithiocarbonates was also
achieved using 1Me. Theoretical calculations supported high
uptake capacity for CO2 and H2.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We gratefully acknowledge the financial support received from
the DST and MNRE, New Delhi, India (to P.K.B.) and SRF
from the University Grants Commission (UGC), New Delhi,
India to M.G. D.D. thanks “TEQIP Collaborative Research
Scheme (CRS).” R.S. and P.K.C. thank UGC and DST, New
Delhi, for Ph.D. and J. C. Bose fellowships, respectively.
REFERENCES
■
(1) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.;
O’Keeffe, M.; Yaghi, O. M. Systematic Design of Pore Size and
Functionality in Isoreticular MOFs and Their Application in Methane
Storage. Science 2002, 295, 469−472. (b) Gupta, M.; Kottilil, D.;
Tomar, K.; Lu, S.; Vijayan, C.; Ji, W.; Bharadwaj, P. K. Two-Photon
Absorption and Fluorescence in Micrometer-Sized Single Crystals of a
Rhodamine B Coordinated MOF. ACS Appl. Nano Mater. 2018, 1,
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.inorgchem.9b03012.
■
sı
́
5408−5413. (c) Ferey, G.; Mellot-Draznieks, C.; Serre, C.; Millange,
X-ray crystallographic data of 1Me (CCDC 1896029),
1ipr (CCDC 1896030), H4L1 ester (CCDC 1896027),
and H4L2 ester (CCDC 1896028); ESI-MS spectra; IR
spectra; TGA, PXRD, and NMR spectra (PDF)
́
F.; Dutour, J.; Surble, S.; Margiolaki, I. A Chromium Terephthalate-
Based Solid with Unusually Large Pore Volumes and Surface Area.
Science 2005, 309, 2040−2042. (d) Banerjee, R.; Phan, A.; Wang, B.;
Knobler, C.; Furukawa, H.; O’Keeffe, M.; Yaghi, O. M. High-
Throughput Synthesis of Zeolitic Imidazolate Frameworks and
Application to CO2 Capture. Science 2008, 319, 939−943.
(e) Furukawa, H.; Ko, N.; Go, Y. B.; Aratani, N.; Choi, S. B.; Choi,
E.; Yazaydin, A. O.; Snurr, R. Q.; O’Keeffe, M.; Kim, J.; Yaghi, O. M.
Ultra high Porosity in Metal-Organic Frameworks. Science 2010, 329,
424−428. (f) Kottilil, D.; Gupta, M.; Tomar, K.; Zhou, F.; Vijayan,
C.; Bharadwaj, P. K.; Ji, W. A cost-effective realization of multimode
exciton-polaritons in single-crystalline microplates of a layered metal-
organic framework. ACS Appl. Mater. Interfaces 2019, 11, 7288−7295.
(g) Lu, W.; Wei, Z.; Gu, Z.-Y.; Liu, T.-F.; Park, J.; Park, J.; Tian, J.;
Zhang, M.; Zhang, Q.; Gentle, T., III; Bosch, M.; Zhou, H.-C. Tuning
the structure and function of metal−organic frameworks via linker
design. Chem. Soc. Rev. 2014, 43, 5561−5593. (h) Stock, N.; Biswas,
S. Synthesis of Metal-Organic Frameworks (MOFs): Routes to
Accession Codes
CCDC 1896027−1896030 contain the supplementary crys-
tallographic 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
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Authors
Pratim Kumar Chattaraj − Department of Chemistry and
Center for Theoretical Studies, Indian Institute of Technology
■
K
https://dx.doi.org/10.1021/acs.inorgchem.9b03012
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
Various MOF Topologies, Morphologies, and Composites. Chem. Rev.
2012, 112, 933−969. (i) Li, M.; Li, D.; O’Keeffe, M.; Yaghi, O. M.
Topological Analysis of Metal−Organic Frameworks with Polytopic
Linkers and/or Multiple Building Units and the Minimal Transitivity
Principle. Chem. Rev. 2014, 114, 1343−1370.
Framework for Chemical Fixation of CO2 under Ambient Conditions.
Angew. Chem., Int. Ed. 2014, 53, 2615−2619.
(9) (a) Biggadike, K.; Angell, R. M.; Burgess, C. M.; Farrell, R. M.;
Hancock, A. P.; Harker, A. J.; Irving, W. R.; Ioannou, C.; Procopiou,
P. A.; Shaw, R. E.; Solanke, Y. E.; Singh, O. M. P.; Snowden, M. A.;
Stubbs, R.; Walton, S.; Weston, H. E. Selective Plasma Hydrolysis of
Glucocorticoid γ-Lactones and Cyclic Carbonates by the Enzyme
Paraoxonase: An Ideal Plasma Inactivation Mechanism. J. Med. Chem.
2000, 43, 19−21. (b) Shaikh, A.-A. G.; Sivaram, S. Organic
Carbonates. Chem. Rev. 1996, 96, 951−976.
(2) (a) Sun, D.; Ke, Y.; Mattox, T. M.; Parkin, S.; Zhou, H.-C.
Stability and Porosity Enhancement through Concurrent Ligand
Extension and Secondary Building Unit Stabilization. Inorg. Chem.
̆
2006, 45, 7566−7568. (b) Horike, S.; Dinca, M.; Tamaki, K.; Long, J.
R. Size-Selective Lewis Acid Catalysis in a Microporous Metal-
Organic Framework with Exposed Mn2+ Coordination Sites. J. Am.
Chem. Soc. 2008, 130, 5854−5855.
(10) (a) Clements, J. H. Reactive Applications of Cyclic Alkylene
Carbonates. Ind. Eng. Chem. Res. 2003, 42, 663−674. (b) 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. (c) Sakakura, T.; Choi, J.-C.; Yasuda, H.
Transformation of Carbon Dioxide. Chem. Rev. 2007, 107, 2365−
2387.
(11) Robbe, Y.; Fernandez, J. P.; Dubief, R.; Chapat, J. P.; Sentenac-
Roumanou, H.; Fatome, M.; Laval, J.-D.; Subra, G. Comparative
radioprotective activity of various pentagonal compounds with two
heteroatoms. Eur. J. Med. Chem. Chem.Ther. 1982, 17, 235−243.
(12) (a) Belokon, Y. N.; Maleev, V. I.; North, M.; Usanov, D. L.
VO(salen)(X) catalysed asymmetric cyanohydrin synthesis: an
unexpected influence of the nature of anion X on the catalytic
activity. Chem. Commun. 2006, 4614−4616. (b) Motokucho, S.; Sudo,
A.; Sanda, F.; Endo, T. Controlled monomer insertion into polymer
main chain: synthesis of sequence ordered polystyrene containing
thiourethane and trithiocarbonate units by the RAFT process. Chem.
Commun. 2002, 1946−1947.
(3) (a) Banerjee, R.; Furukawa, H.; Britt, D.; Knobler, C.; O’Keeffe,
M.; Yaghi, O. M. Control of Pore Size and Functionality in
Isoreticular Zeolitic Imidazolate Frameworks and their Carbon
Dioxide Selective Capture Properties. J. Am. Chem. Soc. 2009, 131,
3875−3877. (b) Yang, Q.; Wiersum, A. D.; Llewellyn, P. L.; Guillerm,
V.; Serre, C.; Maurin, G. Functionalizing porous zirconium
terephthalate UiO-66(Zr) for natural gas upgrading: a computational
exploration. Chem. Commun. 2011, 47, 9603−9605. (c) Gcwensa, N.;
Chatterjee, N.; Oliver, C. L. Interchanged Hysteresis for Carbon
Dioxide and Water Vapor Sorption in a Pair of Water-Stable,
Breathing, Isoreticular, 2-Periodic, Zn(II)-Based Mixed-Ligand
Metal−Organic Frameworks. Inorg. Chem. 2019, 58, 2080−2088.
(4) (a) Cadiau, A.; Belmabkhout, Y.; Adil, K.; Bhatt, P. M.; Pillai, R.
S.; Shkurenko, A.; Martineau-Corcos, C.; Maurin, G.; Eddaoudi, M.
Hydrolytically stable fluorinated metal-organic frameworks for energy-
efficient dehydration. Science 2017, 356, 731−735. (b) Gladysz, J. A.;
́
Curran, D. P.; Horvath, I. T. Handbook of Fluorous Chemistry; Wiley-
́
VCH: Weinheim, Germany, 2004. (c) Horvath, I. T.; Rabai, J. Facile
(13) Runge, F.; El-Hewehi, Z.; Renner, H.-J.; Taeger, E. To note the
trithiocarbonic acid. IV. The Preparation and Properties of
Trithiocarbonic Diesters and Their Use as Pesticides. J. Prakt.
Chem. 1960, 11, 284−308.
catalyst separation without water: fluorous biphase hydroformylation
of olefins. Science 1994, 266, 72−75. (d) Santra, A.; Senkovska, I.;
Kaskel, S.; Bharadwaj, P. K. Gas Storage in a Partially Fluorinated
Highly Stable Three-Dimensional Porous Metal−Organic Framework.
Inorg. Chem. 2013, 52, 7358−7366.
(14) Spek, A. L. Single-crystal structure validation with the program
PLATON. J. Appl. Crystallogr. 2003, 36, 7−13.
(5) Sharma, V.; De, D.; Saha, R.; Das, R.; Chattaraj, P. K.;
Bharadwaj, P. K. A Cu(II)-MOF capable of fixing CO2 from air and
showing high capacity H2 and CO2 adsorption. Chem. Commun. 2017,
53, 13371−13374.
(6) (a) Gupta, M.; De, D.; Tomar, K.; Bharadwaj, P. K. From Zn(II)
to Cu(II) Framework via Single-Crystal to Single-Crystal Metathesis
with Superior Gas Uptake and Heterogeneous Catalytic Properties.
Inorg. Chim. Acta 2018, 482, 925−934. (b) Gupta, A. K.; De, D.;
Tomar, K.; Bharadwaj, P. K. A Cu(II) metal−organic framework with
significant H2and 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.
(7) (a) Dietzel, P. D. C.; Johnsen, R. E.; Fjellvag, H.; Bordiga, S.;
Groppo, E.; Chavan, S.; Blom, R. Adsorption properties and structure
of CO2 adsorbed on open coordination sites of metal−organic
framework Ni2(dhtp) from gas adsorption, IR spectroscopy and X-ray
diffraction. Chem. Commun. 2008, 5125−5127. (b) McDonald, T. M.;
D’Alessandro, D. M.; Krishna, R.; Long, J. R. Enhanced carbon
dioxide capture upon incorporation of N,N′-dimethylethylenediamine
in the metal−organic framework CuBTTri. Chem. Sci. 2011, 2, 2022−
2028. (c) Vaidhyanathan, R.; Iremonger, S. S.; Shimizu, G. K. H.;
Boyd, P. G.; Alavi, S.; Woo, T. K. Direct Observation and
Quantification of CO2 Binding Within an Amine-Functionalized
Nanoporous Solid. Science 2010, 330, 650−653.
(15) Chai, J. D.; Head-Gordon, M. Long-range corrected hybrid
density functionals with damped atom−atom dispersion corrections.
Phys. Chem. Chem. Phys. 2008, 10, 6615−6620.
(16) Frisch, M. J.; et al. Gaussian 09, revision C.01; Gaussian, Inc.:
Wallingford, CT, 2009.
(17) Reed, A. E.; Weinstock, R. B.; Weinhold, F. Natural population
analysis. J. Chem. Phys. 1985, 83, 735−746.
(18) Wiberg, K. B. Application of the pople-santry-segal CNDO
method to the cyclopropylcarbinyl and cyclobutylcation and to
bicyclobutane. Tetrahedron 1968, 24, 1083−1096.
(19) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Intermolecular
Interactions from a Natural Bond Orbital, Donor-Acceptor View-
point. Chem. Rev. 1988, 88, 899−926.
(20) Glendening, E. D.; Reed, A. E.; Carpenter, J. E.; Weinhold, F.
NBO, version 3.1; Gaussian Inc., Pittsburgh.
(21) Mitoraj, M. P.; Michalak, A.; Ziegler, T. A. A Combined Charge
and Energy Decomposition Scheme for Bond Analysis. J. Chem.
Theory Comput. 2009, 5, 962−975.
̀
(22) Swart, M.; Sola, M.; Bickelhaupt, F. M. A new all-round density
functional based on spin states and SN2 barriers. J. Chem. Phys. 2009,
131, 094103−1−094103−9.
(23) Baerends, E. J.; et al. ADF2013.01, SCM, Theoretical
Chemistry; SCM, Vrije Universiteit, Theoretical Chemistry: Am-
sterdam, The Netherlands, 2013.
(8) (a) Aguila, B.; Sun, Q.; Wang, X.; O’Rourke, E.; Al-Enizi, A. M.;
Nafady, A.; Ma, S. Lower Activation Energy for Catalytic Reactions
through Host−Guest Cooperation within Metal−Organic Frame-
works. Angew. Chem., Int. Ed. 2018, 57, 10107−10111. (b) He, H.;
Sun, Q.; Gao, W.; Perman, J. A.; Sun, F.; Zhu, G.; Aguila, B.; Forrest,
K.; Space, B.; Ma, S. A Stable Metal−Organic Framework Featuring a
Local Buffer Environment for Carbon Dioxide Fixation. Angew. Chem.,
Int. Ed. 2018, 57, 4657−4662. (c) 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
(24) te Velde, G.; Bickelhaupt, F. M.; Baerends, E. J.; Fonseca
Guerra, C.; van Gisbergen, S. J. A.; Snijders, J. G.; Ziegler, T.
Chemistry with ADF. J. Comput. Chem. 2001, 22, 931−967.
(25) Bader, R. F. W. Atoms in Molecules: A Quantum Theory; Oxford
University Press: Oxford, UK, 1990.
(26) Lu, T.; Chen, F. W. Multiwfn: A multifunctional wavefunction
analyzer. J. Comput. Chem. 2012, 33, 580−592.
(27) Johnson, E. R.; Keinan, S.; Mori-Sanchez, P.; Contreras-Garcia,
J.; Cohen, A. J.; Yang, W. Revealing Noncovalent Interactions. J. Am.
Chem. Soc. 2010, 132, 6498−6506.
L
https://dx.doi.org/10.1021/acs.inorgchem.9b03012
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
(28) Contreras-Garcia, J.; Johnson, E. R.; Keinan, S.; Chaudret, R.;
Piquemal, J.-P.; Beratan, D. N.; Yang, W. NCIPLOT: A Program for
Plotting Noncovalent Interaction Regions. J. Chem. Theory Comput.
2011, 7, 625−632.
(29) Humphrey, W.; Dalke, A.; Schulten, K. VMD: Visual molecular
dynamics. J. Mol. Graphics 1996, 14, 33−38.
(30) 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.
(31) De, D.; Neogi, S.; Bharadwaj, P. K. Stoichiometry Controlled
Structural Variation in Three-Dimensional Zn(II)−Frameworks:
Single-Crystal to Single-Crystal Transmetalation and Selective CO2
Adsorption. Cryst. Growth Des. 2016, 16, 5238−5246.
̈
(32) Fischer, M.; Hoffmann, F.; Froba, M. Preferred Hydrogen
Adsorption Sites in Various MOFsA Comparative Computational
Study. ChemPhysChem 2009, 10, 2647−2657.
(33) Rowsell, J. L. C.; Eckert, J.; Yaghi, O. M. Characterization of H2
Binding Sites in Prototypical Metal−Organic Frameworks by Inelastic
Neutron Scattering. J. Am. Chem. Soc. 2005, 127, 14904−14910.
(34) Saha, R.; Sharma, V.; De, D.; Bharadwaj, P. K.; Chattaraj, P. K.
A (T-P) Phase Diagram for the Adsorption/Desorption of Carbon
Dioxide and Hydrogen in a Cu(II)-MOF. Polyhedron 2018, 153,
254−260.
(35) (a) Cao, J.; Yu, M.; Li, H.; Wang, L.; Zhu, X.; Wang, G.; Shi, Y.;
Cao, C. Synthesis of cyclic di-and trithiocarbonates from epoxides and
carbon disulfide catalysed by N-heterocyclic carbene. Res. Chem.
Intermed. 2015, 41, 5323−5330. (b) Beattie, C.; North, M.
Titanium(salen)-Catalysed Synthesis of Di- and Trithiocarbonates
from Epoxides and Carbon Disulfide. ChemCatChem 2014, 6, 1252−
1259. (c) Beattie, C.; North, M. North, Mechanistic Investigation of
the Reaction of Epoxides with Heterocumulenes Catalysed by a
Bimetallic Aluminium Salen Complex. Chem. - Eur. J. 2014, 20,
8182−8188. (d) Diebler, J.; Spannenberg, A.; Werner, T. Atom
economical synthesis of di- and trithiocarbonates by the lithium tert-
butoxide catalyzed addition of carbon disulfide to epoxides and
thiiranes. Org. Biomol. Chem. 2016, 14, 7480−7489. (e) Dotsenko, I.
A.; Zhao, Q.; Franz, A. H.; Batoon, P.; Samoshina, N. M.; Samoshin,
V. V. Convenient synthesis of 1,3-dithiolane-2-thiones: cyclic
trithiocarbonates as conformational locks. ARKIVOC 2014, 5, 16−41.
M
https://dx.doi.org/10.1021/acs.inorgchem.9b03012
Inorg. Chem. XXXX, XXX, XXX−XXX