Series of M-MOF-184 (M = Mg, Co, Ni, Zn, Cu, Fe) Metal-Organic Frameworks for Catalysis Cycloaddition of CO2

Article abstract of DOI:10.1021/acs.inorgchem.0c02807

In light of the chemical exploitation of CO2, new reusable materials for efficiently catalyzing the cycloaddition of CO2 and epoxides under moderate conditions are needed. Herein, a new series of isostructural metal-organic frameworks (MOFs) M2(EDOB) [EDO

Full text of DOI:10.1021/acs.inorgchem.0c02807

pubs.acs.org/IC
Article
Series of M‑MOF-184 (M = Mg, Co, Ni, Zn, Cu, Fe) Metal−Organic
Frameworks for Catalysis Cycloaddition of CO2
Y. B. N. Tran, Phuong T. K. Nguyen,* Quang T. Luong, and Khoi D. Nguyen
Cite This: https://dx.doi.org/10.1021/acs.inorgchem.0c02807
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: In light of the chemical exploitation of CO2, new
reusable materials for efficiently catalyzing the cycloaddition of CO2
and epoxides under moderate conditions are needed. Herein, a new
series of isostructural metal−organic frameworks (MOFs)
M2(EDOB) [EDOB4− = 4,4′-(ethyne-1,2-diyl)bis(2-oxido-
benzoate), M = Mg, Ni, Co, Zn, Cu, Fe], known as M-MOF-
184, analogous to a well-studied MOF-74 structure, were
synthesized and fully characterized. The M-MOF-184 (M = Mg,
Co, Ni, Zn) frameworks exhibit accessible mesopore channels (24
Å) and high porosity. Among them, Mg-MOF-184 demonstrated
the most upper surface area (>4000 m2 g−1) in any reported MOF-
74-type frameworks. Furthermore, Co-MOF-184 revealed the
highest CO2 uptake (73 cm3 g−1, at 298 K), and Zn-MOF-184
showed the highest catalytic activity upon the cycloaddition of CO2 (96% conversion, 86% selectivity, and 82% yield) under mild
conditions (1 atm CO2, 80 °C, 6 h, and solvent-free). Notably, the catalytic performance of Zn-MOF-184 outperformed that of the
original M-MOF-74 (M = Mg, Co, Zn) materials and various Zn-based MOFs. To evaluate the acidity and basicity of a series of M-
MOF-184 (M = Mg, Co, Ni, Zn) frameworks, the interaction of these MOFs with acetonitrile vapor was investigated by vapor
adsorption and ATR-FTIR spectroscopy measurements. As such, Zn-MOF-184 showed the strongest Lewis acidity derived by Zn
cations, which was correlated to the highest catalytic activity upon the cycloaddition of CO2. Interestingly, the 2-oxidobenzoate
anions from Co-MOF-184 showed the strongest basicity among the series, which was associated with the highest saturated
acetonitrile uptake (544 cm3 g−1 at 298 K). Our findings suggest that the integration of Lewis acidic and basic sites, high surface area,
and large accessible pores into the framework can facilitate the CO2 fixation reaction.
Metal−organic frameworks (MOFs) are a class of crystalline
porous materials constructed by inorganic and organic building
units via strong bonds.13 Due to their structural and chemical
tunability, MOFs can possess high surface area, multiple active
sites (e.g., acid and base sites), and variable chemical
functionalities, which can be beneficial for improving the
efficiency of the CO2 cycloaddition reaction.14−20 In particular,
MOFs consisting of both acidic and basic sites have been
demonstrated to potentially catalyze the cycloaddition
reaction.21−24 In general, Lewis acid metal centers and
Brønsted acid groups promote the activation of the epoxide
ring, while the basic functions (e.g., amine, pyridine, imidazole,
triazole, tetrazole, and amide groups) improve the CO2 affinity
inside the pore or halide nucleophiles facilitate the opening
INTRODUCTION
■
Given the utilization of CO2 emission, the chemical conversion
of CO2, a significant greenhouse gas, to fine chemicals has
emerged as an environmental and attractive approach.1,2 In this
respect, the cycloaddition of CO2 and epoxides to form cyclic
carbonates is a highly atom-economical process that has been
extensively studied due to wide applications in the
pharmaceutical and fine chemical industries of the carbonate
products.3−5 Although many homogeneous catalysts have been
extensively studied in the synthesis of cyclic carbonates, the
reactions often have difficulties in the separation of catalyst and
product.5 In contrast, the CO2 fixations catalyzed by
heterogeneous catalysts such as ionic liquid-supported solids,6,7
polymers,8,9 and porous organic frameworks10,11 have the
advantages of facile separation and regeneration of the catalyst.
However, these solid catalysts often required harsh conditions
(high CO2 pressure/temperature) due to a lack of accessible
surface area for accelerating interactions of CO2 and reagents
with active sites.3,5,12 Therefore, new heterogeneous catalysts
which efficiently promote this reaction under mild conditions
are still highly desirable.
Received: September 21, 2020
https://dx.doi.org/10.1021/acs.inorgchem.0c02807
© XXXX American Chemical Society
Inorg. Chem. XXXX, XXX, XXX−XXX
A

Inorganic Chemistry
pubs.acs.org/IC
Article
process of epoxide ring. For instance, Co-MOF-74 and Mg-
MOF-74 replete with Lewis metal acid and basic O2− sites
exhibited outstanding conversions of styrene oxide (95%) in
the presence of chlorobenzene solvent at 100 °C under 2 MPa
CO2 and without cocatalyst.25,26 In addition, the composite
polyILs@MIL-101 catalyst,21 formed by the polymerization of
imidazolium-based poly(ionic liquid)s into the MIL-101
structure, revealed excellent catalytic activity toward CO2
cycloaddition with the use of acetonitrile solvent under mild
conditions (<1 bar CO2 pressure, ≤70 °C) due to the synergic
effects of Lewis acid sites (Cr3+) and basic sites (Br−) from
polyILs. Nevertheless, the bifunctional MOFs still have
disadvantages of solvent use,21,25,26 long reaction times,22−24
and high temperature.25,26
To overcome these challenges, we attempted to develop new
MOF-based catalysts in which the acidic and basic sites, high
surface area, and accessibly large aperture functionalized by
polarized moieties can synergistically promote CO2 fixation at
a short reaction time under ambient CO2 pressure and
moderate temperature without the use of solvent. We
envisioned that the polarized pore is able to enrich the
concentration of substrates within the framework, and the large
pore diameter offers an accessible space for the chemical
reactions. As a result, the surface interactions among MOFs,
CO2, and reagent molecules can be improved, which makes
MOFs reach the demand for mild conditions. To date, only a
few reported MOFs exhibit these desired properties in
combination with a high surface area and can be synthesized
via a one-pot reaction. Specifically, a well-established M-MOF-
74 (M2(DOBDC), DOBDC4− = 2,5-dioxidobenzene-
dicarboxylate, also known as CPO-27-M) family27,28 has
emerged as a promising framework for heterogeneous catalysis.
The MOF-74 structure is composed of metal oxo chains
M3[(−O)3(−CO2)3]∞ (M2+ = Mg, Ni, Co, Zn, Cu, Mn, Fe)
connected by organic DOBDC4− units, resulting in highly
porous structures with accessible hexagonal channels. The
infinite rod units contain a high density of open metal sites
serving as Lewis acid sites and the 2-oxidobenzoate anions
acting as basic sites, which have been demonstrated as highly
active nodes capable of gas adsorption29,30 and catalytic
processes.31−33 Furthermore, the MOF-74 prototype also takes
advantage of creating isostructural frameworks with three
strategies including altering the metal components, extending
the length of the organic unit, and modifying chemical
functional groups within the organic unit.28,34
Figure 1. Crystal structure of M-MOF-184. Infinite, rod-shaped metal
clusters, M3[(−O)3(−CO2)3]∞ (where M = Mg, Co, Ni, Zn, Cu, Fe),
are joined with EDOB4− linkers to form M-MOF-184. Atom colors:
C, gray; O, red; and metals, blue. H atoms are omitted for clarity.
by a rigid CC spacer that can minimize the flexibility of the
organic backbone,43 resulting in robust mesopore structures
with a high surface area44 and a polarizable environment
induced by π systems from phenyl rings and alkyne bonds. In
principle, these π systems can interact with a metal (cationic or
neutral), an anion, and another π system by electrostatic
interaction, which can improve the surface affinity of the MOF
framework for all of the reactants such as epoxide, CO2, and
the cocatalyst. By taking advantage of the large surface area, the
conjugated π system within the robust structure, and the high
concentration of accessibly acidic metal and basic 2-
oxidobenzoate anion sites, the M-MOF-184 structure achieves
efficient and heterogeneous catalysis to convert CO2 to cyclic
carbonates under ambient conditions. In previous work, two
M-MOF-184 (M = Mg, Ni) compounds constructed from the
EDOB4− linker had been obtained through large-scale
semitechnical routes.42 However, the quality of experimental
PXRD data of Mg-MOF-184 had not been allowed for
structural elucidation, and the BET surface areas of the M-
MOF-184 frameworks were nonoptimal (SBET = 3154 and
2449 m2 g−1 for Mg- and Ni-MOF-184, respectively), possibly
due to the possible presence of impurity phases. Herein, we
proposed that the employment of a small-scale solvothermal
reaction in the synthesis of M-MOF-184 will be a potential
strategy for achieving the pure phase of the crystalline
framework endowed with optimal surface areas and accessible
pore apertures.45,46 As expected, our activated M-MOF-184
In view of exploring the acidity and basicity of heteroge-
neous catalysts, infrared spectroscopy (IR) on material-
adsorbed acetonitrile has often been used to determine the
surface properties of many solids such as metal oxides and
zeolite.35−38 Acetonitrile with a nitrogen electron lone pair
acting as a soft Lewis base coordinates to an open metal ion
(Lewis acid site), and the proton in the methyl group serves as
a weak Brønsted acid interacting with the basic oxygen anion,
resulting in carbanion and/or acetamide species.36 By FTIR
analysis using acetonitrile as the probe molecule, there are
some studies devoted to determining the Lewis acidity of
MOFs;39−41 however, no study on characterizing the basicity
property of MOFs has been reported.
(M = Mg, Co, Ni, Zn) materials had high surface areas (SBET
>
3200 m2 g−1), and Mg-MOF-184 represented one of the
highest BET surface area values reported for isoreticular MOF-
74 structures (>4000 m2 g−1). Specifically, Co-MOF-184 had
the highest CO2 uptake at 298 K, and Zn-MOF-184 revealed
the best catalytic activity upon cycloaddition of CO2 among
the series. The vapor acetonitrile adsorption at 298 K on four
M-MOF-184 frameworks (M = Mg, Co, Ni, Zn) followed by
FTIR spectroscopy was accordingly studied to determine the
relative strength of acidity and basicity of these M-MOF-184
frameworks. As expected, the FTIR analysis revealed the
strongest Lewis acidity of the Zn-MOF-184 framework, which
was correlated to the highest catalytic performance on CO2
fixation. Also, the 2-oxidobenzoate anions constructed in the
Co-MOF-184 structure revealed the strongest basicity in the
series, which complemented the highest saturated acetonitrile
and CO2 uptakes at 298 K. This work demonstrated the
importance of the high surface area, accessible pore channel,
In this article, we report the synthesis of the M2(EDOB)
series, also known as MOF-18442 (where M = Mg, Ni, Co, Zn,
Cu, and Fe; EDOB4− = 4,4′-(ethyne-1,2-diyl)bis(2-oxido-
benzoate)), with analogous expansion to MOF-74 (Figure 1).
The extended EDOB4− linker contains two phenyl rings joined
B
https://dx.doi.org/10.1021/acs.inorgchem.0c02807
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
anhydrous MeOH, and activated at elevated temperature under
dynamic vacuum. Specifically, due to the facile oxidation of Fe2+, the
solvent exchange and activation for the Fe compound were conducted
with an air-free technique and N2 flow. The solvent-exchange and
activation procedure of the Cu compound were similar to those of
other M-MOF-184 (M = Mg, Co, Ni, Zn) species.
and presence of both Lewis acid and base sites within the
MOF structure, which are suitable for efficiently catalyzing the
chemical fixation of CO2 under mild conditions. To the best of
our knowledge, we first presented the employment of vapor
acetonitrile adsorption combined with FTIR spectroscopy as
an appropriate strategy for investigating the nature of acidic
and basic sites of MOFs.
Even after exhaustive attempts, we were not able to find suitable
conditions for obtaining single-crystalline materials; therefore,
experimentally obtained PXRD patterns were used to determine the
crystal structure. Initial structural models of M-MOF-184 were built
by using Materials Studio 7.0 (Accelrys Software Inc.) software47
(Section S4), in which the trigonal space group (R3) and inorganic
connectivity unit of the MOF-74 structure remained. The DOBDC4−
ligand of the MOF-74 structure was replaced by the EDOB4− linker.
Accordingly, geometry optimization was performed by using the
universal force field implemented in the Forcite module, and the unit
cell parameters were optimized until energy convergence was
achieved (10−4 kcal/mol). As for the preparation for the powder X-
ray diffraction (PXRD) measurement, only the Fe-MOF-184 sample
was placed on an airtight specimen holder in a glovebox to avoid
oxidation of the powder sample. The others were mounted on a zero
background holder under an ambient environment. PXRD measure-
ments were collected with the 2θ range from 3 to 50°, a step size of
0.02°, and a fixed count time of 2 s per step. The predicted M-MOF-
184 structures were also validated with the Pawley refinements using
the Reflex module in which the PXRD patterns of activated samples
are matched with those calculated from crystal models. Full details are
described in the Supporting Information, Section S4.
Catalytic Studies of M-MOF-184 for the Cycloaddition of
CO2 and Epoxide. In a model experiment, epoxide (5 mmol),
activated MOF catalyst (1.2 mol % ratio based on active metal sites),
and tetrabutylammonium bromide (nBu4NBr, 1.5 mol %) were
inserted into a 25 mL Schlenk tube in a N2-filled glovebox. The tube
was flash frozen under a liquid N2 bath and subsequently evacuated (3
× 5 min) before being connected to a CO2 balloon. The reaction was
stirred, heated to 80 °C, and regularly monitored by GC analysis of
sample aliquots. After completion, the reaction was cooled in an ice
bath, the unreacted CO2 was vented, and the MOF catalyst was
removed by centrifugation. The catalytic conversion, selectivity, and
yield of the reaction were determined by GC−FID analysis of an
aliquot of the reaction using biphenyl as the internal standard. For the
recycling experiment, the recovered MOF catalyst was washed with
anhydrous MeOH (3 × 3 mL) for 24 h, activated with the same
procedure of parent MOF, and then reused for successive cycles. The
procedure for the cycloaddition reaction under high CO2 pressure was
conducted in a Parr high-pressure reactor. The autoclave reactor was
evacuated (3 × 5 min), purged with CO2, and then placed under the
desired pressure of CO2 for 15 min to allow the system to equilibrate.
Then the reactor was allowed to stir and set at 80 °C for 6 h. At the
end of the reaction, the reactor was placed in an ice bath for 20 min,
and the unreacted CO2 was vented before the reactor was opened. All
catalytic experiments were performed at least three times. As for the
FTIR studies on MOFs in contact with the reactants, all recovered
MOF samples were swiftly soaked in anhydrous MeOH (2 mL) after
the adsorbed experiments, and then dried under vacuum (0.03 Torr)
at room temperature.
EXPERIMENTAL SECTION
■
Materials and Analytical Techniques. All of the information for
materials, general procedures, and analytical instruments are described
in the Supporting Information (SI). Briefly, the H4EDOB linker was
synthesized via four consecutive steps (Supporting Information,
Scheme S1). Full synthesis details are provided in the SI, Section S2.
1H and 13C nuclear magnetic resonance (NMR) spectra were
recorded on a Bruker Advance II 500 MHz spectrometer. Powder X-
ray diffraction data were collected using a Bruker D8 Advance
diffractometer in reflectance Bragg−Brentano geometry at 40 kV and
40 mA for Cu Kα radiation (λ = 1.54178 Å). Thermogravimetric
analysis (TGA) was carried out using a TA Q500 thermal analysis
system. Attenuated total reflectance Fourier transform infrared spectra
(ATR-FTIR) were recorded on a Bruker Vertex 70 system by
accumulating 100 scans at 2 cm−1 resolution. A dried MOF sample
(∼2 mg) was placed on a diamond crystal plate and well-flatted with a
spatula. All of the ATR-FTIR spectra were measured at least four
times, and the output signals are described as follows: vs, very strong;
s, strong; m, medium; sh, shoulder; w, weak; vw, very weak; and br,
broad. Elemental microanalyses for activated samples were performed
on a LECO CHNS-932 analyzer. Low-pressure N2 and CO2
adsorption isotherms were volumetrically recorded on a Micro-
meritics 3Flex instrument. The products of catalytic reactions were
identified with an Agilent 19091s-433 gas chromatography (GC)
system equipped with an Agilent 5973N mass spectrometry detector
(GC−MS), and the catalytic conversions, selectivities, and yields were
determined using an Agilent 123-0132 GC system equipped with a
flame ionization detector (GC−FID) in the presence of biphenyl as
an internal standard.
Vapor acetonitrile (CH3CN) isotherms were measured with a BEL
Japan BELSORP-aqua3. To ensure the reproducibility of acetonitrile
sorption, all of the measurements were recorded three times and the
results obtained with standard deviations of 0.1, 0.1, 0.2, and
0.1% for Mg-, Co-, Ni-, and Zn-MOF-184, respectively. For the
evaluation of acidity and basicity properties, M-MOF-184 samples
after the acetonitrile adsorption were evacuated under a dynamic
vacuum to achieve a pressure of 10 Torr at room temperature,
followed by performing ATR-FTIR spectroscopy.
Synthesis and Structural Determination of M-MOF-184. Full
synthesis and characterization details of each M-MOF-184 framework
can be found in the SI, Section S3.
M-MOF-184 (M = Mg, Co, Ni, Zn). A hydrated metal nitrate (M =
Mg, Co, Ni, Zn) and the H4EDOB linker were added to different
mixtures of N,N-dimethylformamide (DMF) and methanol
(MeOH)/ethanol (EtOH)/water (H2O). The reaction mixture was
placed in a scintillation vial, sealed with a PTFE-lined cap, sonicated
until affording a clear solution, and held at 120 °C for 24 h. The
resulting M-MOF-184 solid was washed with anhydrous DMF,
immersed in anhydrous MeOH, and held at 100 °C under dynamic
vacuum.
M-MOF-184 (M = Cu, Fe). The syntheses of Cu and Fe frameworks
were conducted under an inert atmosphere of N2. By using a cannula,
a solvent mixture of anhydrous DMF and anhydrous isopropanol/
anhydrous MeOH was transferred to a Schlenk tube, which was
preloaded with hydrate copper nitrate or anhydrous iron(II) chloride
and H4EDOB linker. The mixtures were flash frozen and evacuated at
least three times to remove O2, followed by stirring and heating at an
appropriate temperature under a N2-filled balloon. Upon completion,
the brown-red (for Fe-MOF-184) and greenish (Cu-MOF-184) solids
were produced at the bottom of the tube. The resulting Cu- and Fe-
based solids were washed with anhydrous DMF, immersed in
RESULTS AND DISCUSSION
■
Structural Characterization of M-MOF-184. The
successful synthesis of microcrystalline M-MOF-184 frame-
works was confirmed by PXRD analysis of the experimental
samples in comparison with the predicted patterns from the
crystal models (SI, Section S4). The PXRD patterns of as-
prepared M-MOF-184 frameworks showed good agreement in
peak position with the predicted patterns (Figures S5−S10).
Accordingly, full profile matching Pawley refinements were
performed and achieved good matches of the initial and refined
unit cell parameters (Figure 2) (SI, Section S4). The refined
C
https://dx.doi.org/10.1021/acs.inorgchem.0c02807
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
agreement with the calculated values derived from EA (21.8,
37.3, 33.4, 38.3, 37.0, 30.3%, respectively). The singular
morphology of stick-shaped crystallites observed for as-
synthesized M-MOF-184 samples through the scanning
electron microscopy (SEM) images confirmed the phase
purity of as-made M-MOF-184 (Figures S20−S25).
Porosity and CO2 Adsorption Properties. The
permanent porosity of all activated M-MOF-184 compounds
was evaluated by measuring the N2 isotherms at 77 K. The
resulting profiles displayed a type IV isotherm with full
reversibility, which is typical of a mesoporous material. The
isotherms showed steep increases in the range of P/P0 = 0.05−
0.07 without hysteresis, which was attributed to the pore filling
in regular mesopores (Figure S26). From these isotherms,
Brunauer−Emmett−Teller (BET)/Langmuir surface areas for
Mg, Co, Ni, Zn, Cu, and Fe compounds were estimated to be
4050/4240, 3250/3580, 3250/3470, 3750/3450, 2460/2200,
and 3020/2450 m2 g−1, respectively (Table 1). The
experimental surface areas and pore volumes for Cu- and Fe-
MOF-184 have proven challenging due to the low crystallinity
(for Cu) and high oxidation (for Fe) upon conventional
activation, thus Cu and Fe variants will not be further
evaluated. Notably, our BET specific surface area values for
Mg- and Ni-MOF-184 were higher compared to the previously
reported data for Mg- and Ni-MOF-184 (3154 and 2449 m2
g−1, respectively).42 The pore volumes estimated at P/P0 =
0.15 from the N2 isotherms for Mg-, Co-, Ni-, and Zn-MOF-
184 (1.41, 1.18, 1.10, and 1.12 cm3 g−1, respectively) were 2
times higher than those of Mg-, Co-, Ni, and Zn-MOF-74
(Table 1). The experimental surface areas and pore volumes
for Mg-, Co-, Ni-, and Zn-MOF-184 compounds well matched
the theoretical van der Waals values calculated from the refined
crystal structures with open metal sites (Table S7), indicating
the complete desolvation and structural robustness of four
frameworks upon conventional activation. Moreover, the pore
size distributions were estimated to be around 22−23 Å and
exhibited good agreement with the mesopore nature obtained
from crystallographic data (Figure S27). It was worth noting
that the surface areas for M-MOF-184 (M = Mg, Co, Ni, Zn)
compounds were greater than those of the M2(dobpdc)
compounds (SBET = 3000−3900 m2 g−1)48 and IRMOF-74-III-
R (R = H, CH3, NH2, SBET = 2440−2720 m2 g−1).51
Remarkably, the surface area of representative Mg-MOF-184
(SBET = 4050 m2 g−1) is one of the highest values reported for
isoreticular MOF-74 structures [SBET = 3270 m2 g−1 for
Mg2(dobpdc),52 SLangmuir = 5770 m2 g−1 for Mg2(dotpdc)53].
We systematically investigated the low-pressure CO2 uptake
property of M-MOF-184 (M = Mg, Co, Ni, Zn). The CO2
Figure 2. Pawley refinement of Mg-MOF-184. Shown are the
experimental (red), refined (black), and difference (green) patterns.
The Bragg positions are marked as pink bars, and the patterns
calculated from the crystal models are shown in blue.
M-MOF-184 structures exhibited unit cell parameters that
were nearly equivalent to the predictions with good agreement
factors and low convergence residuals (Rwp = 2.29−5.84%, Rp
= 1.45−4.07%) (Section S4, Tables S1−S6). The variant of the
void volumes, lattice parameters, and unit cell volumes for the
refined M-MOF-184 structures could account for the different
ionic radii of these divalent cations (Tables S1−S6). The pore
channels of M-MOF-184 have larger diameters (23 × 25 Å2)
compared to those of M-MOF-74 (10 × 13 Å2).28 We noticed
that the unit cell volumes of M-MOF-184 (9862−10 656 Å3)
were nearly 3 times greater than those of M-MOF-74 (3067−
4066 Å3) (Table 1). Interestingly, the calculated crystal
densities from the refined structure of Mg-MOF-184 with or
without coordinated water (0.53/0.48 cm3 g−1, respectively)
were lower than those of IRMOF-74-III(Mg) (0.58/0.53 cm3
g−1, respectively), even though Mg-MOF-184 has smaller
aperture diameters than IRMOF-74-III(Mg) (22.2 × 27.3
Å2).28
The thermal gravimetric analysis (TGA) of activated M-
MOF-184 showed no weight loss up to 150 °C, implying the
absence of guest molecules in the pores (Figure S19). The
major weight loss for each compound associated with the
framework degradation was observed at 200 °C (Fe), 250 °C
(Cu), 300 °C (Co, Ni), and 350 °C (Mg, Zn) (Figure S19).
An analysis of the weight percent of residual metal oxide for
Mg (21.8%), Co (37.1%), Ni (33.6%), Zn (38.1%), Cu
(37.0%), and Fe (30.3%) variants was found to be in good
Table 1. Comparison of Pore Structure and Gas Adsorption Properties between the Refined M-MOF-184 (M-MOF-74)
Framework Families
a
a
a
b
c
d
M
d
cryst/cm3 g−1
unit cell volume/%
void space/%
S
BET/m2 g−1
V
pore/cm3 g−1
CO2 uptake/cm3 g−1
Qst/kJ mol−1
e
e
e
e
f
e
Mg
Co
Ni
Zn
Cu
Fe
0.53 (0.91)
0.64 (1.17)
0.68 (1.19)
0.64 (1.22)
0.68 (1.31)
0.65 (1.12)
10 656.10 (3964.72)
10 396.06 (3967.06)
9861.76 (3909.02)
10 698.49 (3981.47)
9992.66 (3663.26)
10 186.40 (4065.85)
75.6 (60.5)
74.2 (58.7)
74.3 (60.3)
74.6 (58.2)
74.9 (58.8)
74.4 (58.8)
4050 (1603)
3250 (1572)
3250 (1351)
3750 (1279)
2460 (1369)
3020 (1360)
1.41 (0.60)
1.18 (0.57)
1.10 (0.53)
1.12 (0.47)
0.65
68
73
71
43
35
33
36
21
e
e
e
g
0.82
a
b
Calculated from the refined crystal structures of M-MOF-184 and the reported crystal structures of M-MOF-74. The pore volume was calculated
c
d
at P/P0 = 0.15 from the N2 isotherm (77 K). At 800 Torr and 298 K. The isosteric heat of CO2 adsorption was calculated at zero coverage.
e
f
g
Reference 48. Reference 49. Reference 50.
D
https://dx.doi.org/10.1021/acs.inorgchem.0c02807
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
adsorption behaviors of these four MOF-184 frameworks
differed from that of the metal component. In such, the initial
uptakes in the low-pressure region for Mg, Co, and Ni at 298 K
were much steeper than those observed for Zn (Figure 3),
Catalytic Studies of M-MOF-184 for the Cyclo-
addition of CO2 and Epoxide. Motivated by the structural
features of M-MOF-184 (M = Mg, Co, Ni, Zn) frameworks
including a high density of different Lewis acidic and basic
sites, high surface area, and an accessible mesopore channel, we
sought to explore their catalytic activity on the cycloaddition of
CO2. To obtain an optimized reaction condition, we first used
styrene oxide (5 mmol) as an example epoxide, activated M-
MOF-184 (1.2 mol %, calculated on the basis of metal sites)
materials, and nBu4NBr (1.5 mol %), solvent-free, at 80 °C
under atmosphere CO2 pressure for 6 h. Under the model
conditions, four M-MOF-184 materials exhibited moderate
conversions of styrene oxide (>60%) (Figure S36) and a high
selectivity of styrene carbonate formation (>80%) (Table S8).
Among this series, Zn-MOF-184 displayed the highest catalytic
performance in the formation of styrene carbonate with highly
epoxide conversion (96%), selectivity (85%), and yield (82%)
in a solvent-free environment at 80 °C for 6 h (Table 2, Figure
4). The media catalyzed by Zn-MOF-184 were used for up to
Figure 3. CO2 isotherms at 298 K for M-MOF-184 (M = Mg, Co, Ni,
Zn). Adsorption and desorption branches are marked by filled and
open symbols, respectively. The connecting curves are guides for the
eye.
indicative of the high affinity of Mg, Co, and Ni frameworks to
CO2. Except for Zn-MOF-184 revealing the smallest total CO2
uptake at 298 K, the capacities for Mg, Co, and Ni frameworks
were slightly different from each other, in which the greatest
CO2 uptake observed for Co-MOF-184 (73 cm3 g−1) was a bit
higher than the uptake value of Ni-MOF-184 (71 cm3 g−1),
followed by Mg-MOF-184 (68 cm3 g−1).54 The variable-
temperature CO2 adsorption properties were recorded at 273,
283, and 298 K (Figures S28−S30), and the isosteric heat of
CO2 adsorption (Qst) was subsequently calculated by fitting
the respective isotherms using a virial-type expansion (Figure
S32). The higher Qst values for Ni, Mg, and Co (36, 35, and 33
kJ mol−1, respectively) compared to that of the Zn variant (21
kJ mol−1) led to strong interactions of CO2 with the exposed
Ni2+, Mg2+, and Co2+ metal centers. The lowest Qst value of the
Zn framework could be attributed to its fully 3d10 electron
configuration.55 With the empirical Irving−Williams series for
high-spin octahedral divalent cations, the trend in Qst values
(Ni > Mg > Co > Zn) tracked inversely well with the ionic
radius of the high-spin divalent metal cation (Ni < Mg < Co <
Zn).
Figure 4. Time-dependent yield of styrene carbonate catalyzed by M-
MOF-184 (M = Mg, Co, Ni, Zn, Cu, Fe). Error bars indicate the
range of data based on three repeat experiments.
8 h and observed to have no significant increase in carbonate,
implying the completeness of reaction at 6 h (Figure S37). Mg,
Co, and Ni compounds exhibited high selectivities of styrene
carbonate (>82%) but lower conversions of styrene oxide
(62−73%). The turnover number (TON) and turnover
frequency (TOF) for the Zn compound (20, 10 h−1,
respectively) were also found to be at least 2 times higher
a
Table 2. Catalytic Performance of M-MOF-184 for the Cycloaddition of Styrene Oxide and CO2
b
c
d
e
c
d
f
c
d
no.
M-MOF-184
con./%
TON
TOF/h−1
con./%
TON
TOF/h−1
con./%
TON
TOF/h−1
1
2
3
4
Zn-MOF-184
Mg-MOF-184
Co-MOF-184
Ni-MOF-184
62
35
28
14
20
11
10
4.6
10
86
54
54
35
28
19
19
12
6.9
4.8
4.8
3.0
96
72
72
61
31
23
23
21
5.1
3.8
3.8
3.5
5.5
5.0
2.3
a
Reaction conditions: styrene oxide (5.0 mmol), MOF catalyst (1.2 mol % metal active site), nBu4NBr (1.5 mol %), 1 atm CO2 (balloon pressure),
b
c
80 °C, and 6 h. Conversion determined by GC−FID analysis of the crude reaction mixture after 2 h. TON = (moles of product)/(moles of metal
in the catalyst). TOF = TON/reaction time. Conversion determined by GC−FID analysis of the crude reaction mixture after 4 h. Conversion
determined by GC−FID analysis of the crude reaction mixture after 6 h.
d
e
f
E
https://dx.doi.org/10.1021/acs.inorgchem.0c02807
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
than those of others (Table 2), implying the high catalytic
activity of the Zn-based framework. The reaction in the
absence of MOF catalyst afforded only a 12% yield of
carbonate, indicating the significant impact induced by M-
MOF-184 (M = Mg, Co, Ni, Zn) frameworks on the chemical
transformation of CO2.
To demonstrate the potential and applicability of the Zn-
MOF-184 system, the substrate scope was also studied on
other epoxides including propylene oxide, epichlorohydrin, and
cyclohexene oxide (Figure 5). Propylene oxide and epichlor-
Furthermore, the reusable nature of Zn-MOF-184 was
evident when the leaching and recycling experiments were
performed. At the outset of the 1 h catalysis reaction, the Zn-
MOF-184 catalyst was isolated by centrifugation, and filtration
was allowed to continue under the same condition. As shown
in Figure S37, there were insignificant increases in the
formation of styrene carbonate (an increase of 8.6% yield).
Moreover, only a trace amount of Zn2+ leached from the
framework into the filtrate, as confirmed by ICP analysis (the
concentration of Zn2+ < 0.043 ppm). For the recycling study,
there were insignificant decreases in the catalytic performance
after five consecutive runs of the experiments (Figure S38).
The structural stability of Zn-MOF-184 after several reactions
was accordingly evaluated by PXRD, BET, and FTIR analyses
of the reused Zn-MOF-184 samples after the sixth cycled
reaction. As expected, the PXRD pattern revealed the
unimportant change in the peak intensity and position,
indicating the stability of the Zn-based framework (Figure
S39). The BET surface area presented a slight decrease,
indicative of the insignificant degradation of Zn-MOF-184
(Figure S40). Additionally, the IR spectra for recovered Zn-
MOF-184 after activation and the parent Zn-MOF-184
showed a good in-line profile, implying that the structural
integrity remained after several catalysis reactions (Figure
S41).
The catalytic activity of the heterogeneous Zn-MOF-184
framework was further compared with other homogeneous and
heterogeneous Zn-based catalysts. As depicted in Table S9
(entries 1−4), homogeneous metal salts Mg(NO3)3·6H2O,
Co(NO3)3·6H2O, Ni(NO3)3·6H2O, and Zn(CH3COO)2·
2H2O and heterogeneous solids Zn and ZnO facilitated
lower catalytic performances (9.6−57% yield) compared to
that of Zn-MOF-184. We found that the TOF values at 6 h of
reaction time catalyzed by these nonporous homogeneous and
heterogeneous metal-based catalysts (0.6−3.6 h−1) were lower
than that of Zn-MOF-184 (5.1 h−1), indicative of the
outperformed activity of the porous Zn-MOF-184 framework.
Interestingly, neither the Zn precursor [Zn(NO3)2·6H2O] nor
the H4EDOB linker resulted in low conversions of styrene
oxide (37 and 25%, respectively) and moderate selectivities of
styrene carbonate formation (63 and 52%, respectively) under
similar conditions (Table S9, entries 4 and 6). Also, the
mixture of Zn(NO3)2·6H2O and the H4EDOB linker afforded
a slight increase in the styrene oxide conversion (45%) but
with less selectivity toward the styrene carbonate (50%) (Table
S9, entry 7). This evidence supported the high catalytic activity
of the porous Zn-MOF-184 framework constructed from the
coordination between the infinite rod Zn-oxo cluster and the
H4EDOB linker. Furthermore, as shown in Table S9 (entries
14−16), two isostructural Mg- and Co-MOF-74 frameworks
with the same topological network, smaller pore aperture sizes,
and lower porosities promoted the lower conversions of
styrene oxide (27 and 31%, respectively) compared to that of
Zn-MOF-184 under the same condition (1.2 mol % catalyst,
calculated on the basis of metal sites). Interestingly, Zn-MOF-
184 and Zn-MOF-74 had activities than outperformed Mg-
and Co-MOF-74 frameworks, implying the strong Lewis
acidity derived from the infinite Zn-oxo rod unit. It was
worth noting that Zn-MOF-184 with the larger aperture size
exhibited higher conversion and selectivity in the formation of
styrene carbonate than did Zn-MOF-74 (Table S9), suggesting
the important role of large pore structure in catalytic
performance.
Figure 5. Catalytic performance during the synthesis of different
cyclic carbonates catalyzed by Zn-MOF-184. Error bars indicate the
range of data based on three repeat experiments.
ohydrin had the highest conversions (100%) compared with
styrene oxide (96%) and cyclohexene oxide (69%) owing to
the faster diffusion of small substrates rather than large
substrates into the MOF’s pores. In particular, the large
epoxide substrates restrict the diffusion into the MOF pores,
which limit the access of reactants (e.g., epoxides, CO2,
nBu4NBr) to the active sites (e.g., Lewis metal sites, 2-
oxidobenzoate anions), resulting in the low conversion.14,56−58
Epichlorohydrin exhibited slightly lower selectivity and yield in
the formation of carbonate than propylene oxide, attributed to
the electron-withdrawing effect of the −Cl group reducing the
electron density of the epoxide oxygen. The lower conversion
of styrene oxide in comparison to propylene oxide and
epichlorohydrin was associated with the low reactivity of its β-
carbon attributed to the conjugation between the benzene ring
and the epoxy group. Among the epoxides examined,
cyclohexene oxide exhibited the lowest catalytic performance
(yield of 59%) owing to steric hindrance originating from the
two rings of the substrate, which restricts the ring opening. We
noticed that large substrates cyclohexene oxide and styrene
oxide exhibited higher selectivities in the formation of
respective carbonates (88 and 86%, respectively) than did
small substrates propylene oxide and epichlorohydrin (70 and
72%, respectively). These observations indicated that Zn-
MOF-184 exhibited the high catalytic conversion of small
substrates and remarkably catalytic selectivity of large
substrates in the CO2 fixation reaction.
F
https://dx.doi.org/10.1021/acs.inorgchem.0c02807
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
To further validate the large pore function on the
cycloaddition reaction, the catalytic performances of propylene
oxide, epichlorohydrin, styrene oxide, and cyclohexene oxide
were also evaluated on the Zn-MOF-74 catalyst (Figure 6). As
more significant impact of the structural function of the Zn-
MOF-184 framework in comparison to the high surface area
and high CO2 uptake properties in catalyzing CO2 fixation.
Due to the quadrupole moment of CO2, the phenolate
anions in the MOF-74 (CPO-27)-type structure acting as basic
sites can activate CO2 in the cycloaddition reaction, resulting
in CO2-phenolate nucleophiles. These CO2-phenolate nucle-
ophiles then undergo the ring-opening process of epoxide,
followed by yielding the cyclic carbonate product.63 This
consequence had been established from the experimental
works in which the cycloaddition reaction catalyzed by M-
MOF-74 (CPO-27, M = Mg, Co) in the absence of the
nBu4NBr cocatalyst (the Br− anion of the nBu4NBr cocatalyst
can lead to nucleophilic attack on the epoxide, leading to ring-
opening progress) had produced the carbonate product with a
yield of >95% under a CO2 pressure of 2 MPa.25,26 To explore
the role of the phenolate anions in our MOF-184 platform, we
also employed the cycloaddition reaction without using
nBu4NBr cocatalyst under two CO2 conditions: ambient
pressure and 2 MPa. The results showed that there was no
carbonate product formed under either reaction condition. We
accordingly characterized the Zn-MOF-184 catalyst after the
cocatalyst-free reactions (named SO/CO2@Zn) by using
FTIR analysis, and the results exhibited the emergence of
two peaks at 1490 and 1517 cm−1 associated with two ν-
2−
carbonate CO3 vibrations attributed to the formation of
CO2-phenolate (Figure S46).38,64 However, as stated above,
none of the carbonate product was found, indicating that the
CO2-phenolate nucleophiles derived from Zn-MOF-184 do
not proceed with the ring-opening process, thus the cocatalyst-
free reaction catalyzed by Zn-MOF-184 cannot produce the
cyclic carbonate product. This result was attributed to the large
distance between the CO2-phenolate nucleophile and the
epoxide ring (Figure S47), resulting in an impossible attack on
the CO2-phenolate nucleophile and epoxide ring. Motivated by
this evidence, we demonstrated that the phenolate anions
constructed in the M-MOF-184 network are not involved in
the important catalytic sites which directly promote the ring-
opening epoxide process in the formation of cyclic carbonate.
We noted that the effect of phenolate anions enhances the
surface affinity of MOF’s pore wall for CO2.
Figure 6. Conversions and yields of various cyclic carbonates
generated from CO2 cycloadditions catalyzed by Zn-MOF-184
(dark colors) and Zn-MOF-74 (light colors). Error bars indicate
the range of data based on three repeat experiments.
expected, the catalytic conversions of these epoxides catalyzed
by Zn-MOF-74 (aperture size of 11 Å) were lower than those
catalyzed by Zn-MOF-184 (aperture size of 22 Å) under the
same condition (1.2 mol % catalyst, calculated on the basis of
metal sites). Yields of generated cyclic carbonates catalyzed by
Zn-MOF-74 were only 52% for propylene oxide, 48% for
epichlorohydrin, 50% for styrene oxide, and 38% for
cyclohexene oxide, which were poorer (average of 20%) than
those of Zn-MOF-184. We also found that the selectivity in the
formation of cyclohexene carbonate catalyzed by Zn-MOF-74
(only 63%) was lower than that catalyzed by Zn-MOF-184
(88%), confirming the outperformed catalytic selectivity
attributed to the larger pore function of Zn-MOF-184. The
outstanding effect of the large pore feature within the Zn-
MOF-184 framework on the catalytic performance of CO2
fixation was worth noting.
To demonstrate the superior activity of the infinite Zn-oxo
chain cluster, model reactions proceeding by other Zn-based
MOFs such as MOF-5,59 MOF-177,60 ZIF-8,61 and MOF-
50862 were carried out (Table S9, entries 17−20). These
MOFs constructed by representative cluster typesoctahedral
(Zn4O(CO2)6 for MOF-5 and MOF-177), tetrahedral (ZnN4
for ZIF-8), and paddle-wheel (Zn2N2(CO2)4 for MOF-508)
geometriespromoted a lower catalytic transformation than
did Zn-MOF-184. This result indicated the high catalytic
activity of the infinite rod of Zn3[O3(CO2)3]∞ units.
Moreover, we noticed that the surface area and CO2 uptake
properties of Zn-VNU-74 (SBET = 3750 m2 g−1/CO2 uptake =
43 cm3 g−1) were lower than those of other MOFs such as Mg-
MOF-184 (4050 m2 g−1/68 cm3 g−1, respectively), M-MOF-74
series (600−1300 m2 g−1/120−130 cm3 g−1, respectively), and
MOF-5 (970 cm3 g−1/56 cm3 g−1, respectively), indicating the
To investigate the surface interaction of reactants and the
Zn-MOF-184 framework, ATR-FTIR analysis was carried out
on the Zn-MOF-184 samples in contact with styrene oxide
(termed SO@Zn) and after 4 h of reaction under the model
condition (named Sub@Zn).65 As depicted in Figure S48, the
emergence of weak peaks at 2176 and 2150 cm−1 ascribing to
stretching vibrations of CC bonds was observed for both
SO@Zn and Sub@Zn samples. In general, the CC
stretching absorptions (near 2100 cm−1) for symmetrically
internal alkyne are weak or absent due to the minimal dipole of
the CC bond. Indeed, the CC stretching modes were not
found in activated Zn-MOF-184 material (Figure S48).
However, both SO@Zn and Sub@Zn samples showed the
occurrence of these CC stretching vibrations, indicating that
the dipole moment of CC bonds was increased due to the
surface interaction between the EDOB4− linker and the
reactants. Moreover, the presence of new peaks at 1129 and
1070 cm−1 was observed in SO@Zn owing to the characteristic
peaks of alkoxide C−O−C stretching vibrations of styrene
oxide.66,67 The intensity of absorbed bands at 1103 and 1029
cm−1 associated with alkoxy C−O stretching vibrations of the
2-oxidobenzoate anion was increased in the Sub@Zn sample.
G
https://dx.doi.org/10.1021/acs.inorgchem.0c02807
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
These results implied the high affinity of the Zn-MOF-184
framework for organic substrates.
(M = Mg, Co, Ni, Zn) frameworks were slightly different from
each other, probably due to their same topological network
and similar structural functions of unit cell volume, void space,
and porosity (Table S10). Interestingly, Co-MOF-184 reached
the highest uptake (548 cm3 g−1, 1.00 g g−1) with the broadest
hysteresis loop (P/P0 = 0.20−0.35), and Mg-MOF-184
exhibited second-order saturation uptake with the narrowest
hysteresis loop (P/P0 = 0.20−0.25). As for this series, we
found the saturated capacities to follow the trend of Co > Mg
> Ni ≈ Zn, while the volumetric uptakes were arranged in the
order Co > Ni > Zn > Mg (Table 3). Steeply increased uptakes
below P/P0 = 0.05 were observed, which was possibly
associated with the coordination of the metal centers to the
nitrogen atom of acetonitrile. Depending on the metal ions, the
capillary condensations induced in two different pressure
regions (P/P0 = 0.1−0.2 and 0.2−0.35) and hysteresis loops
were observed with various extensions (defined in percentage,
Section S8) in the order Co (26%) > Zn (19%) > Ni (12%) >
Mg (4%). These findings suggested distinguishing surface
interactions between M-MOF-184 frameworks and vapor
acetonitrile.
In comparison with the MOF-74 structure, the ATR-FTIR
analysis was also evaluated on the activated Zn-MOF-74
material adsorbed on styrene oxide (named SO@Zn-MOF-
74). As shown in Figure S49, there were unimportant
differences in the intensities of the absorbed bands (1129−
1026 cm−1) associated with alkoxy C−O stretching vibrations
of styrene oxide and the 2-oxidobenzoate anion of the
activated Zn-MOF-74 and SO@Zn-MOF-74 samples, imply-
ing the weak interactions between the Zn-MOF-74 structure
and epoxide. These observations further demonstrated the
high polarity of the Zn-MOF-184 framework attributed to the
incorporation of the CC bond in the EDOB4− linker,
resulting in the high affinity of Zn-MOF-184 for the reactants.
Accordingly, a plausible mechanism for the cycloaddition of
CO2 catalyzed by Zn-MOF-184 was proposed (Figure 7).14−17
For comparison, acetonitrile adsorption isotherms were
conducted on Co-MOF-74, Basolite C300 (HKUST-1),
Basolite Z1200 (ZIF-8), and BPL carbon (Figure S50). As
shown in Table 3, the maximum uptake capacity of Co-MOF-
184 (0.99 g g−1) was 2 times higher than that of Co-MOF-74
(0.48 g g−1), BPL carbon (0.44 g g−1), Basolite Z1200 (0.41 g
g−1), and Basolite C300 (0.32 g g−1). The volumetric
maximum capacity for Co-MOF-184 (348 cm3 cm−3) was
also higher than that of Co-MOF-74 (308 cm3 cm−3), Basolite
C300 (60 cm3 cm−3), Basolite Z1200 (78/70 cm3 cm−3), and
BPL carbon (105 cm3 cm−3). We noted that Basolite C300 and
Basolite Z1200, well-known MOFs endowed with Lewis acid
sites (Cu2+ and Zn2+ ions, respectively), and BPL carbon, a
microporous material with an absence of the acid and base
sites, exhibited smaller acetonitrile adsorption properties
compared to those of Co-MOF-184 and Co-MOF-74.
Among these comparative MOFs, Co-MOF-74 revealed a
larger acetonitrile uptake compared to those of Basolite C300,
Basolite Z1200, and BPL carbon even though the lowest
surface area was noted for Co-MOF-74 (Table S10),
suggesting the significant structural function of the accessibly
infinite rod-based structure containing both Lewis acid and
base sites. Furthermore, the aperture diameters of Co-MOF-
184 are larger than those of Co-MOF-74, resulting in the
higher acetonitrile uptake capacity for Co-MOF-184, indicative
of the important impact of large aperture diameter on the
acetonitrile adsorption. Accordingly, ATR-FTIR analysis on
M-MOF-184 (M = Mg, Co, Ni, Zn) samples after the vapor
acetonitrile adsorption were conducted to characterizing the
acidic and basic sites of four frameworks (Figure 9).68−70 In
such, Mg, Zn, Co, and Ni frameworks showed an absorption
band corresponding to the ν(CN) vibrational mode of
acetonitrile (2252 cm−1), which shifted to higher frequencies
of 2256, 2257, 2275, and 2281 cm−1, respectively, indicating
the presence of coordination between nitrogen atoms to open
metal sites (Figure 9A). The largest magnitude of intensity for
the shift was found in the Zn compound, followed by the order
Mg > Ni > Co, implying that the Zn framework has the
strongest Lewis acidity in the series.39−41 This evidence
confirmed the best performer to be Zn-MOF-184 for the
catalysis cycloaddition of CO2.
Figure 7. Proposed reaction mechanism for the cycloaddition of CO2
with epoxides catalyzed by Zn-MOF-184.
First, the epoxide ring is activated by an O atom through
interaction with Zn sites. Second, the Br− nucleophile
generated from the nBu4NBr cocatalyst triggers the C atom
of epoxide and engages in ring-opening, resulting in a Zn-
bromoalkoxide. Subsequently, O2− of the Zn-bromoalkoxide
interacts with CO2 enriched in the pore, forming a Zn-
alkycarbonate intermediate. Finally, a carbonate product is
obtained through a ring-closure step accompanied by the
regeneration of the Zn-MOF-184 catalyst and Br− nucleophile.
Characterization of Acidity and Basicity Properties.
While the surface areas, aperture sizes, and unit cell parameters
of the four M-MOF-184 (M = Mg, Co, Ni, Zn) frameworks
were relatively similar, their catalytic performance on CO2
fixation was dramatically different. Moreover, M-MOF-184
structures replete with both Lewis acidic (open metal center)
and basic 2-oxidobenzoate anion sites, large pore apertures,
and high surface areas engage the chemical interactions with
acetonitrile. Motivated by these features, we sought to
investigate the relative strength of acidity and basicity using
an ATR-FTIR study on M-MOF-184 (M = Mg, Co, Ni, Zn)
frameworks with adsorbed vapor acetonitrile.
As depicted in Figure 8 and Table 3, the acetonitrile
isotherms at 298 K for four M-MOF-184 (M = Mg, Co, Ni,
Zn) frameworks showed several steps and a hysteresis loop
with high saturation capacities (>480 cm3 g−1, 0.88 g g−1). The
saturated acetonitrile uptake capacities for four M-MOF-184
H
https://dx.doi.org/10.1021/acs.inorgchem.0c02807
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
Figure 8. Acetonitrile isotherms at 25 °C for (A) Mg, (B) Co, (C) Ni, and (D) Zn materials. Closed and open circles represent the adsorption and
desorption branches, respectively. The connecting line is provided as a guide.
in which the largest intensity of two bands was noted in Co
and Zn variants, followed by Mg and Ni (Figure 9B).
Furthermore, the presence of new peaks ascribing to the
scissor and asymmetric vibrations of C−H bonds (1482−1468
cm−1) and C−H bending movements (∼1307 cm−1)
associated with the formation of (CH2CN)− carbanionic
species of the basic O2− sites to the H atoms of −CH3 groups
was noted for Co, Ni, and Mg materials (Figure 9C),35−37 in
which the relative intensities of these absorption bands were
found to follow the order Co > Ni > Mg > Zn. All of this
evidence indicated that the greatest number of (CH2CN)−
carbanions created within Co-MOF-184 resulted from the
coordinative interactions of the CH3CN−Co framework and
the polymerization of CH3CN−CH3CN.37 This was attributed
to the strongest basicity of the 2-oxidobenzoate anions sites
coordinating to the Co centers. Interestingly, we noted that
Co-MOF-184 presented the strongest basicity and the highest
acetonitrile uptake, which were also correlated to the highest
CO2 uptake property, a wide probe molecule used for
characterizing basic sites.72−74 Our results suggested that the
use of acetonitrile adsorption and corresponding ATR-FTIR
analysis on MOF’s adsorbed acetonitrile was an appropriate
method for evaluating the acidity and basicity of MOF’s
structure consisting of Lewis acidic and basic sites.
Table 3. Acetonitrile Adsorption Properties for M-MOF-
184 in Comparison with Representative MOFs/
Adsorbents
a
no.
material
uptake capacity/g g−1 uptake capacity/cm3 cm−3
1
2
3
4
5
6
7
8
Mg-MOF-184
Co-MOF-184
Ni-MOF-184
Zn-MOF-184
Co-MOF-74
Basolite C300
Basolite Z1200
BPL
0.96
0.99
0.89
0.88
0.48
0.32
0.41
0.44
278
348
330
309
308
60
78
105
a
The maximum uptake was calculated at P/P0 = 0.9.
On the other hand, the characterization of the basicity
property through surface interactions of the basic 2-
oxidobenzoate anions with acetonitrile was evaluated. In
such, the peaks that appeared at about 2230 and 2210 cm−1
(Figure 9A) related to the CN vibrational modes in the
formation of physisorbed CH3CN species and the polymer-
ization of (CH2CN)− carbanions, respectively,71 were
examined in each framework (Figure 9A). As for this series,
Co-MOF-184 had the highest intensity for these bands,
following the order Ni > Mg ≈ Zn. Furthermore, four M-
MOF-184 compounds exhibited the occurrence of new
absorption bands relating to the formation of (CH2CN)−
carbanions (2020−2033 cm−1) whose CN stretching
bands were observed at about 2038−2046 cm−1 (Figure 9B),
SUMMARY
■
The synthesis and full characterization of an isostructural series
M-MOF-184 (M = Mg, Co, Ni, Zn, Cu, Fe) were reported. In
this series, the Co framework showed the highest low-pressure
I
https://dx.doi.org/10.1021/acs.inorgchem.0c02807
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
Figure 9. ATR-FTIR spectra of acetonitrile (CH3CN) adsorbed on M-MOF-184 (M = Mg, Co, Ni, Zn) frameworks.
CO2 uptake (73 cm3 g−1, at 800 Torr, 298 K), and Ni
presented the highest isosteric heat of adsorption (36 kJ
mol−1). Zn-MOF-184 revealed the highest catalytic perform-
ance upon cycloaddition of CO2 (conversion of 96%,
selectivity of 86%, and yield of 82%) under mild reaction
conditions (solvent-free, balloon pressure of CO2, 80 °C, 6 h).
The catalysis performance of Zn-MOF-184 outperformed that
of homogeneous, heterogeneous catalysts, the M-MOF-74 (M
= Mg, Co, Zn) series, and other Zn-based MOFs. Through
FTIR analysis of these MOFs after acetonitrile adsorption, the
relative acidity and basicity of four M-MOF-184 members were
determined. Accordingly, the Lewis acid Zn sites in the Zn
structure and the basic 2-oxidobenzoate anions derived from
the Co framework were proven to have the strongest acidity
and basicity, respectively. These results were found to be in
agreement with the best catalytic activity of Zn-MOF-184 on
cycloaddition of CO2 and the highest CO2 and acetonitrile
uptakes of Co-MOF-184. Our contribution paves the way for
the future development of MOFs applicable to catalysis
cycloaddition of CO2 and provides a convenient guideline for
the characterization of MOFs replete with both Lewis acidic
and basic sites.
Chi Minh City (VNUHCM), Ho Chi Minh City 700000,
Vietnam; orcid.org/0000-0002-9149-2279;
Email: ntkphuong@inomar.edu.vn
Authors
Y. B. N. Tran − Center for Innovative Materials and
Architectures (INOMAR), Vietnam National UniversityHo
Chi Minh City (VNUHCM), Ho Chi Minh City 700000,
Vietnam
Quang T. Luong − Center for Innovative Materials and
Architectures (INOMAR), Vietnam National UniversityHo
Chi Minh City (VNUHCM), Ho Chi Minh City 700000,
Vietnam
Khoi D. Nguyen − Center for Innovative Materials and
Architectures (INOMAR), Vietnam National UniversityHo
Chi Minh City (VNUHCM), Ho Chi Minh City 700000,
Vietnam
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.inorgchem.0c02807
Funding
This work was financially supported by grant INOMAR-
CS2018-50-03, Vietnam National UniversityHo Chi Minh
City (VNUHCM).
ASSOCIATED CONTENT
■
sı
* Supporting Information
Notes
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.inorgchem.0c02807.
The authors declare no competing financial interest.
Full details for linker and MOF synthesis and character-
izations (PXRD, TGA curves, FTIR, and gas adsorp-
tion), catalytic reactions, vapor sorptions details (PDF)
ACKNOWLEDGMENTS
■
We thank Assoc. Prof. Thang Bach Phan (VNU-HCM) for
supporting this work and Dr. Hiroyasu Furukawa (UC
Berkeley) for insightful comments.
AUTHOR INFORMATION
■
REFERENCES
Corresponding Author
■
Phuong T. K. Nguyen − Center for Innovative Materials and
Architectures (INOMAR), Vietnam National UniversityHo
(1) Aresta, M.; Dibenedetto, A.; Angelini, A. Catalysis for the
Valorization of Exhaust Carbon: from CO2 to Chemicals, Materials,
J
https://dx.doi.org/10.1021/acs.inorgchem.0c02807
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
and Fuels. Technological Use of CO2. Chem. Rev. 2014, 114, 1709−
1742.
(21) Ding, M.; Jiang, H.-L. Incorporation of Imidazolium-Based
Poly(ionic liquid)s into a Metal-Organic Framework for CO2 Capture
and Conversion. ACS Catal. 2018, 8, 3194−3201.
(22) Ugale, B.; Kumar, S.; Dhilip Kumar, T. J.; Nagaraja, C. M.
Environmentally Friendly, Co-catalyst-Free Chemical Fixation of CO2
at Mild Conditions Using Dual-Walled Nitrogen-Rich Three-Dimen-
sional Porous Metal-Organic Frameworks. Inorg. Chem. 2019, 58,
3925−3936.
(23) Sun, Y.; Huang, H.; Vardhan, H.; Aguila, B.; Zhong, C.;
Perman, J. A.; Al-Enizi, A. M.; Nafady, A.; Ma, S. Facile Approach to
Graft Ionic Liquid into MOF for Improving the Efficiency of CO2
Chemical Fixation. ACS Appl. Mater. Interfaces 2018, 10, 27124−
27130.
(24) Liang, J.; Chen, R.-P.; Wang, X.-Y.; Liu, T.-T.; Wang, X.-S.;
Huang, Y.-B.; Cao, R. Postsynthetic ionization of an imidazole-
containing metal-organic framework for the cycloaddition of carbon
dioxide and epoxides. Chem. Sci. 2017, 8, 1570−1575.
(25) Cho, H.-Y.; Yang, D.-A.; Kim, J.; Jeong, S.-Y.; Ahn, W.-S. CO2
adsorption and catalytic application of Co-MOF-74 synthesized by
microwave heating. Catal. Today 2012, 185, 35−40.
(2) Liu, Q.; Wu, L.; Jackstell, R.; Beller, M. Using carbon dioxide as
a building block in organic synthesis. Nat. Commun. 2015, 6, 5933.
(3) Martín, C.; Fiorani, G.; Kleij, A. W. Recent Advances in the
Catalytic Preparation of Cyclic Organic Carbonates. ACS Catal. 2015,
5, 1353−1370.
(4) Shaikh, R. R.; Pornpraprom, S.; D’Elia, V. Catalytic Strategies for
the Cycloaddition of Pure, Diluted, and Waste CO2 to Epoxides
under Ambient Conditions. ACS Catal. 2018, 8, 419−450.
(5) North, M.; Pasquale, R.; Young, C. Synthesis of cyclic carbonates
from epoxides and CO2. Green Chem. 2010, 12, 1514−1539.
(6) Shi, L.; Xu, S.; Zhang, Q.; Liu, T.; Wei, B.; Zhao, Y.; Meng, L.;
Li, J. Ionic Liquid/Quaternary Ammonium Salt Integrated Hetero-
geneous Catalytic System for the Efficient Coupling of Carbon
Dioxide with Epoxides. Ind. Eng. Chem. Res. 2018, 57, 15319−15328.
(7) Shi, X.-L.; Chen, Y.; Duan, P.; Zhang, W.; Hu, Q. Conversion of
CO2 into Organic Carbonates over a Fiber-Supported Ionic Liquid
Catalyst in Impellers of the Agitation System. ACS Sustainable Chem.
Eng. 2018, 6, 7119−7127.
(8) Ziaee, M. A.; Tang, Y.; Zhong, H.; Tian, D.; Wang, R. Urea-
Functionalized Imidazolium-Based Ionic Polymer for Chemical
Conversion of CO2 into Organic Carbonates. ACS Sustainable
Chem. Eng. 2019, 7, 2380−2387.
(9) Yang, Z.; Yu, B.; Zhang, H.; Zhao, Y.; Chen, Y.; Ma, Z.; Ji, G.;
Gao, X.; Han, B.; Liu, Z. Metalated Mesoporous Poly-
(triphenylphosphine) with Azo Functionality: Efficient Catalysts for
CO2 Conversion. ACS Catal. 2016, 6, 1268−1273.
(10) Sun, Q.; Aguila, B.; Perman, J.; Nguyen, N.; Ma, S. Flexibility
Matters: Cooperative Active Sites in Covalent Organic Framework
and Threaded Ionic Polymer. J. Am. Chem. Soc. 2016, 138, 15790−
15796.
(11) Zhi, Y.; Shao, P.; Feng, X.; Xia, H.; Zhang, Y.; Shi, Z.; Mu, Y.;
Liu, X. Covalent organic frameworks: efficient, metal-free, heteroge-
neous organocatalysts for chemical fixation of CO2 under mild
conditions. J. Mater. Chem. A 2018, 6, 374−382.
(12) Sakakura, T.; Kohno, K. The synthesis of organic carbonates
from carbon dioxide. Chem. Commun. 2009, 1312−1330.
(13) Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. The
Chemistry and Applications of Metal-Organic Frameworks. Science
2013, 341, 1230444.
(14) 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.
(26) Yang, D.-A.; Cho, H.-Y.; Kim, J.; Yang, S.-T.; Ahn, W.-S. CO2
capture and conversion using Mg-MOF-74 prepared by a
sonochemical method. Energy Environ. Sci. 2012, 5, 6465−6473.
(27) Caskey, S. R.; Wong-Foy, A. G.; Matzger, A. J. Dramatic
Tuning of Carbon Dioxide Uptake via Metal Substitution in a
Coordination Polymer with Cylindrical Pores. J. Am. Chem. Soc. 2008,
130, 10870−10871.
(28) Deng, H.; Grunder, S.; Cordova, K. E.; Valente, C.; Furukawa,
́
H.; Hmadeh, M.; Gandara, F.; Whalley, A. C.; Liu, Z.; Asahina, S.;
Kazumori, H.; O’Keeffe, M.; Terasaki, O.; Stoddart, J. F.; Yaghi, O. M.
Large-Pore Apertures in a Series of Metal-Organic Frameworks.
Science 2012, 336, 1018.
(29) Tan, K.; Zuluaga, S.; Gong, Q.; Canepa, P.; Wang, H.; Li, J.;
Chabal, Y. J.; Thonhauser, T. Water Reaction Mechanism in Metal
Organic Frameworks with Coordinatively Unsaturated Metal Ions:
MOF-74. Chem. Mater. 2014, 26, 6886−6895.
(30) Queen, W. L.; Hudson, M. R.; Bloch, E. D.; Mason, J. A.;
Gonzalez, M. I.; Lee, J. S.; Gygi, D.; Howe, J. D.; Lee, K.; Darwish, T.
A.; James, M.; Peterson, V. K.; Teat, S. J.; Smit, B.; Neaton, J. B.;
Long, J. R.; Brown, C. M. Comprehensive study of carbon dioxide
adsorption in the metal-organic frameworks M2(dobdc) (M = Mg,
Mn, Fe, Co, Ni, Cu, Zn). Chem. Sci. 2014, 5, 4569−4581.
(31) Valvekens, P.; Vandichel, M.; Waroquier, M.; Van Speybroeck,
V.; De Vos, D. Metal-dioxidoterephthalate MOFs of the MOF-74
type: Microporous basic catalysts with well-defined active sites. J.
Catal. 2014, 317, 1−10.
(32) Gao, Z.; Yu, Z. W.; Liu, F. Q.; Yu, Y.; Su, X. M.; Wang, L.; Xu,
Z. Z.; Yang, Y. L.; Wu, G. R.; Feng, X. F.; Luo, F. Ultralow-Content
Iron-Decorated Ni-MOF-74 Fabricated by a Metal-Organic Frame-
work Surface Reaction for Efficient Electrocatalytic Water Oxidation.
Inorg. Chem. 2019, 58, 11500−11507.
(33) Sun, D.; Sun, F.; Deng, X.; Li, Z. Mixed-Metal Strategy on
Metal-Organic Frameworks (MOFs) for Functionalities Expansion:
Co Substitution Induces Aerobic Oxidation of Cyclohexene over
Inactive Ni-MOF-74. Inorg. Chem. 2015, 54, 8639−8643.
(34) Fracaroli, A. M.; Furukawa, H.; Suzuki, M.; Dodd, M.; Okajima,
(15) Ding, M.; Flaig, R. W.; Jiang, H.-L.; Yaghi, O. M. Carbon
capture and conversion using metal-organic frameworks and MOF-
based materials. Chem. Soc. Rev. 2019, 48, 2783−2828.
(16) He, H.; Perman, J. A.; Zhu, G.; Ma, S. Metal-Organic
Frameworks for CO2 Chemical Transformations. Small 2016, 12,
6309−6324.
(17) Hou, S.-L.; Dong, J.; Zhao, B. Formation of C-X Bonds in CO2
Chemical Fixation Catalyzed by Metal-Organic Frameworks. Adv.
Mater. 2020, 32, 1806163.
(18) Lu, B.-B.; Yang, J.; Liu, Y.-Y.; Ma, J.-F. A Polyoxovanadate-
Resorcin[4]arene-Based Porous Metal-Organic Framework as an
Efficient Multifunctional Catalyst for the Cycloaddition of CO2 with
Epoxides and the Selective Oxidation of Sulfides. Inorg. Chem. 2017,
56, 11710−11720.
́
S.; Gandara, F.; Reimer, J. A.; Yaghi, O. M. Metal-Organic
Frameworks with Precisely Designed Interior for Carbon Dioxide
Capture in the Presence of Water. J. Am. Chem. Soc. 2014, 136, 8863−
8866.
(19) Nguyen, P. T. K.; Nguyen, H. T. D.; Nguyen, H. N.; Trickett,
(35) Pelmenschikov, A. G.; van Santen, R. A.; Janchen, J.; Meijer, E.
Acetonitrile-d3 as a probe of Lewis and Broensted acidity of zeolites.
J. Phys. Chem. 1993, 97, 11071−11074.
́
C. A.; Ton, Q. T.; Gutierrez-Puebla, E.; Monge, M. A.; Cordova, K.
́
E.; Gandara, F. New Metal-Organic Frameworks for Chemical
Fixation of CO2. ACS Appl. Mater. Interfaces 2018, 10, 733−744.
(20) Zhang, L.; Yuan, S.; Fan, W.; Pang, J.; Li, F.; Guo, B.; Zhang,
P.; Sun, D.; Zhou, H.-C. Cooperative Sieving and Functionalization of
Zr Metal-Organic Frameworks through Insertion and Post-Mod-
ification of Auxiliary Linkers. ACS Appl. Mater. Interfaces 2019, 11,
22390−22397.
(36) Morterra, C.; Penarroya Mentruit, M.; Cerrato, G. Acetonitrile
̃
adsorption as an IR spectroscopic probe for surface acidity/basicity of
pure and modified zirconias. Phys. Chem. Chem. Phys. 2002, 4, 676−
687.
(37) Aboulayt, A.; Binet, C.; Lavalley, J.-C. IR study of acetonitrile
adsorption on hydroxylated zirconium dioxide: mechanism of
K
https://dx.doi.org/10.1021/acs.inorgchem.0c02807
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
acetonitrile hydrolysis. J. Chem. Soc., Faraday Trans. 1995, 91, 2913−
2920.
Elucidating CO2 Chemisorption in Diamine-Appended Metal-
Organic Frameworks. J. Am. Chem. Soc. 2018, 140, 18016−18031.
(54) All of the CO2 adsorption experiments were performed at least
three times, and the total CO2 uptakes at 298 K were obtained with
standard deviations of 0.1, 0.15, 0.1, and 0.1 cm3 g−1 for the
Mg, Co, Ni, and Zn compounds, respectively.
(38) Lavalley, J. C. Infrared spectrometric studies of the surface
basicity of metal oxides and zeolites using adsorbed probe molecules.
Catal. Today 1996, 27, 377−401.
́
(39) Volkringer, C.; Leclerc, H.; Lavalley, J.-C.; Loiseau, T.; Ferey,
G.; Daturi, M.; Vimont, A. Infrared Spectroscopy Investigation of the
Acid Sites in the Metal-Organic Framework Aluminum Trimesate
MIL-100(Al). J. Phys. Chem. C 2012, 116, 5710−5719.
(40) Herbst, A.; Khutia, A.; Janiak, C. Brønsted Instead of Lewis
Acidity in Functionalized MIL-101Cr MOFs for Efficient Heteroge-
neous (nano-MOF) Catalysis in the Condensation Reaction of
Aldehydes with Alcohols. Inorg. Chem. 2014, 53, 7319−7333.
(41) Guillerm, V.; Ragon, F.; Dan-Hardi, M.; Devic, T.;
Vishnuvarthan, M.; Campo, B.; Vimont, A.; Clet, G.; Yang, Q.;
(55) Gygi, D.; Bloch, E. D.; Mason, J. A.; Hudson, M. R.; Gonzalez,
M. I.; Siegelman, R. L.; Darwish, T. A.; Queen, W. L.; Brown, C. M.;
Long, J. R. Hydrogen Storage in the Expanded Pore Metal-Organic
Frameworks M2(dobpdc) (M = Mg, Mn, Fe, Co, Ni, Zn). Chem.
Mater. 2016, 28, 1128−1138.
(56) Wu, P.; Li, Y.; Zheng, J.-J.; Hosono, N.; Otake, K.-I.; Wang, J.;
Liu, Y.; Xia, L.; Jiang, M.; Sakaki, S.; Kitagawa, S. Carbon dioxide
capture and efficient fixation in a dynamic porous coordination
polymer. Nat. Commun. 2019, 10, 4362.
́
Maurin, G.; Ferey, G.; Vittadini, A.; Gross, S.; Serre, C. A Series of
(57) Stavila, V.; Foster, M. E.; Brown, J. W.; Davis, R. W.;
Edgington, J.; Benin, A. I.; Zarkesh, R. A.; Parthasarathi, R.; Hoyt, D.
W.; Walter, E. D.; Andersen, A.; Washton, N. M.; Lipton, A. S.;
Allendorf, M. D. IRMOF-74(n)-Mg: a novel catalyst series for
hydrogen activation and hydrogenolysis of C-O bonds. Chem. Sci.
2019, 10, 9880−9892.
(58) Xia, Q.; Li, Z.; Tan, C.; Liu, Y.; Gong, W.; Cui, Y. Multivariate
Metal-Organic Frameworks as Multifunctional Heterogeneous Asym-
metric Catalysts for Sequential Reactions. J. Am. Chem. Soc. 2017,
139, 8259−8266.
Isoreticular, Highly Stable, Porous Zirconium Oxide Based Metal-
Organic Frameworks. Angew. Chem., Int. Ed. 2012, 51, 9267−9271.
(42) Oh, H.; Maurer, S.; Balderas-Xicohtencatl, R.; Arnold, L.;
Magdysyuk, O. V.; Schutz, G.; Muller, U.; Hirscher, M. Efficient
̈ ̈
synthesis for large-scale production and characterization for hydrogen
storage of ligand exchanged MOF-74/174/184-M (M = Mg2+, Ni2+).
Int. J. Hydrogen Energy 2017, 42, 1027−1035.
(43) Furukawa, H.; Sun, X. Extended Linkers for Ultrahigh Surface
Area Metal-Organic Frameworks. In The Chemistry of Metal-Organic
Frameworks: Synthesis, Characterization, and Applications; Kaskel, S.,
Ed.; Wiley, 2016; Chapter 10, pp 271−307.
(59) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.; 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.
(44) Farha, O. K.; Wilmer, C. E.; Eryazici, I.; Hauser, B. G.; Parilla,
P. A.; O’Neill, K.; Sarjeant, A. A.; Nguyen, S. T.; Snurr, R. Q.; Hupp,
J. T. Designing Higher Surface Area Metal-Organic Frameworks: Are
Triple Bonds Better Than Phenyls? J. Am. Chem. Soc. 2012, 134,
9860−9863.
(45) Furukawa, H. Synthesis and Characterization of Metal-Organic
Frameworks. In Gas Adsorption in Metal-Organic Frameworks:
Fundamentals and Applications; Glover, T., Mu, B., Eds.; CRC Press,
2018; Chapter 2, pp 17−81.
(46) Firmino, A. D. G.; Mendes, R. F.; Tome, J. P. C.; Almeida Paz,
F. A. Synthesis of MOFs at the Industrial Scale. In Metal-Organic
Frameworks: Applications in Separations and Catalysis; García, H.,
(60) Furukawa, H.; Miller, M. A.; Yaghi, O. M. Independent
Verification of the Saturation Hydrogen Uptake in MOF-177 and
Establishment of a Benchmark for Hydrogen Adsorption in Metal-
Organic Frameworks. J. Mater. Chem. 2007, 17, 3197−3204.
(61) Wang, B.; Cote, A. P.; Furukawa, H.; O’Keeffe, M.; Yaghi, O.
M. Colossal cages in zeolitic imidazolate frameworks as selective
carbon dioxide reservoirs. Nature 2008, 453, 207−211.
(62) Chen, B.; Liang, C.; Yang, J.; Contreras, D. S.; Clancy, Y. L.;
Lobkovsky, E. B.; Yaghi, O. M.; Dai, S. A Microporous Metal-Organic
Framework for Gas-Chromatographic Separation of Alkanes. Angew.
Chem., Int. Ed. 2006, 45, 1390−1393.
(63) Xu, K.; Moeljadi, A. M. P.; Mai, B. K.; Hirao, H. How Does
CO2 React with Styrene Oxide in Co-MOF-74 and Mg-MOF-74?
Catalytic Mechanisms Proposed by QM/MM Calculations. J. Phys.
Chem. C 2018, 122, 503−514.
(64) Cerruti, M.; Morterra, C. Carbonate Formation on Bioactive
Glasses. Langmuir 2004, 20, 6382−6388.
́
́
Navalon, S., Eds; Wiley, 2018; Chapter 3, pp 57−80.
(47) Accelrys Materials Studio, version 7.0; Accelrys Inc.: San Diego,
CA, 2012.
́
́
́
(48) Garzon-Tovar, L.; Carne-Sanchez, A.; Carbonell, C.; Imaz, I.;
Maspoch, D. Optimised room temperature, water-based synthesis of
CPO-27-M metal-organic frameworks with high space-time yields. J.
Mater. Chem. A 2015, 3, 20819−20826.
(49) Rosnes, M. H.; Opitz, M.; Frontzek, M.; Lohstroh, W.; Embs, J.
P.; Georgiev, P. A.; Dietzel, P. D. C. Intriguing differences in
hydrogen adsorption in CPO-27 materials induced by metal
substitution. J. Mater. Chem. A 2015, 3, 4827−4839.
(50) Bloch, E. D.; Murray, L. J.; Queen, W. L.; Chavan, S.;
Maximoff, S. N.; Bigi, J. P.; Krishna, R.; Peterson, V. K.; Grandjean,
F.; Long, G. J.; Smit, B.; Bordiga, S.; Brown, C. M.; Long, J. R.
Selective Binding of O2 over N2 in a Redox-Active Metal-Organic
Framework with Open Iron(II) Coordination Sites. J. Am. Chem. Soc.
2011, 133, 14814−14822.
(65) As stated, all of the MOF samples (SO@Zn and Sub@Zn)
were swiftly soaked in anhydrous MeOH (2 mL) and then dried
under vacuum (0.03 Torr) at room temperature before performing
the FTIR analysis.
(66) Guo, X.; Zhou, Z.; Chen, C.; Bai, J.; He, C.; Duan, C. New rht-
Type Metal-Organic Frameworks Decorated with Acylamide Groups
for Efficient Carbon Dioxide Capture and Chemical Fixation from
Raw Power Plant Flue Gas. ACS Appl. Mater. Interfaces 2016, 8,
31746−31756.
(67) Nguyen, H. T. D.; Tran, Y. B. N.; Nguyen, H. N.; Nguyen, T.
(51) Fracaroli, A. M.; Furukawa, H.; Suzuki, M.; Dodd, M.; Okajima,
S.; Gandara, F.; Reimer, J. A.; Yaghi, O. M. Metal-organic frameworks
with precisely designed interior for carbon dioxide capture in the
presence of water. J. Am. Chem. Soc. 2014, 136, 8863−8866.
(52) Gygi, D.; Bloch, E. D.; Mason, J. A.; Hudson, M. R.; Gonzalez,
M. I.; Siegelman, R. L.; Darwish, T. A.; Queen, W. L.; Brown, C. M.;
Long, J. R. Hydrogen Storage in the Expanded Pore Metal-Organic
Frameworks M2(dobpdc) (M = Mg, Mn, Fe, Co, Ni, Zn). Chem.
Mater. 2016, 28, 1128−1138.
́
C.; Gandara, F.; Nguyen, P. T. K. A Series of Metal-Organic
Frameworks for Selective CO2 Capture and Catalytic Oxidative
Carboxylation of Olefins. Inorg. Chem. 2018, 57, 13772−13782.
(68) Mudunkotuwa, I. A.; Minshid, A. A.; Grassian, V. H. ATR-
FTIR spectroscopy as a tool to probe surface adsorption on
nanoparticles at the liquid-solid interface in environmentally and
biologically relevant media. Analyst 2014, 139, 870−881.
(69) Cerruti, M.; Bolis, V.; Magnacca, G.; Morterra, C. Surface
chemical functionalities in bioactive glasses. The gas/solid adsorption
of acetonitrile. Phys. Chem. Chem. Phys. 2004, 6, 2468−2479.
(70) Sushkevich, V. L.; Ivanova, I. I.; Yakimov, A. V. Revisiting
Acidity of SnBEA Catalysts by Combined Application of FTIR
(53) Forse, A. C.; Milner, P. J.; Lee, J.-H.; Redfearn, H. N.;
Oktawiec, J.; Siegelman, R. L.; Martell, J. D.; Dinakar, B.; Porter-
Zasada, L. B.; Gonzalez, M. I.; Neaton, J. B.; Long, J. R.; Reimer, J. A.
L
https://dx.doi.org/10.1021/acs.inorgchem.0c02807
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
pubs.acs.org/IC
Article
Spectroscopy of Different Probe Molecules. J. Phys. Chem. C 2017,
121, 11437−11447.
(71) Granados-Reyes, J.; Salagre, P.; Cesteros, Y.; Busca, G.;
Finocchio, E. Assessment through FT-IR of surface acidity and
basicity of hydrocalumites by nitrile adsorption. Appl. Clay Sci. 2019,
180, 105180.
(72) Yan, X.; Wang, K.; Xu, X.; Wang, S.; Ning, Q.; Xiao, W.; Zhang,
N.; Chen, Z.; Chen, C. Brønsted Basicity in Metal-Organic
Framework-808 and Its Application in Base-Free Catalysis. Inorg.
Chem. 2018, 57, 8033−8036.
(73) Zhu, L.; Liu, X.-Q.; Jiang, H.-L.; Sun, L.-B. Metal-Organic
Frameworks for Heterogeneous Basic Catalysis. Chem. Rev. 2017, 117,
8129−8176.
(74) Tan, Y. C.; Zeng, H. C. Lewis basicity generated by localised
charge imbalance in noble metal nanoparticle-embedded defective
metal-organic frameworks. Nat. Commun. 2018, 9, 4326.
M
https://dx.doi.org/10.1021/acs.inorgchem.0c02807
Inorg. Chem. XXXX, XXX, XXX−XXX