Tuning Lewis Acidity of Metal-Organic Frameworks via Perfluorination of Bridging Ligands: Spectroscopic, Theoretical, and Catalytic Studies

Article abstract of DOI:10.1021/jacs.8b05765

The Lewis acidity of metal-organic frameworks (MOFs) has attracted much research interest in recent years. We report here the development of two quantitative methods for determining the Lewis acidity of MOFs - based on electron paramagnetic resonance (EPR) spectroscopy of MOF-bound superoxide (O₂^?-) and fluorescence spectroscopy of MOF-bound N-methylacridone (NMA) - and a simple strategy that significantly enhances MOF Lewis acidity through ligand perfluorination. Two new perfluorinated MOFs, Zr₆-fBDC and Zr₆-fBPDC, where H₂fBDC is 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylic acid and H₂fBPDC is 2,2′,3,3′,5,5′,6,6′-octafluoro-4,4′-biphenyldicarboxylic acid, were shown to be significantly more Lewis acidic than nonsubstituted UiO-66 and UiO-67 as well as the nitrated MOFs Zr₆-BDC-NO₂ and Zr₆-BPDC-(NO₂)₂. Zr₆-fBDC was shown to be a highly active single-site solid Lewis acid catalyst for Diels-Alder and arene C-H iodination reactions. Thus, this work establishes the important role of ligand perfluorination in enhancing MOF Lewis acidity and the potential of designing highly Lewis acidic MOFs for fine chemical synthesis.

Full text of DOI:10.1021/jacs.8b05765

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Article
Tuning Lewis Acidity of Metal-Organic Frameworks via Perfluorination
of Bridging Ligands: Spectroscopic, Theoretical, and Catalytic Studies
Pengfei Ji, Tasha Drake, Akiko Murakami, Pau Oliveres, Jonathan H. Skone, and Wenbin Lin
J. Am. Chem. Soc., Just Accepted Manuscript • Publication Date (Web): 26 Jul 2018
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Journal of the American Chemical Society
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Tuning Lewis Acidity of Metal-Organic Frameworks via Per-
fluorination of Bridging Ligands: Spectroscopic, Theoretical,
and Catalytic Studies
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†‡
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Pengfei Ji, Tasha Drake, Akiko Murakami, Pau Oliveres, Jonathan H. Skone, and Wenbin Lin*
†
th
Department of Chemistry, The University of Chicago, 929 E 57 St, Chicago, IL 60637, USA
‖Research Computing Center, The University of Chicago, 5607 S. Drexel Ave, Chicago, IL 60637, USA
catalysts due, in part, to the insolubility and structural complexity
of MOFs. Although notable efforts have been made to use reac-
tion kinetics to probe Lewis acidity, the reaction rates are convo-
luted with intrinsic Lewis acidity, diffusion rates of sub-
strates/products through the MOF channels and in solution, and
ABSTRACT: The Lewis acidity of metal-organic frameworks
MOFs) has attracted much research interest in recent years. We
(
report here the development of two quantitative methods for de-
termining the Lewis acidity of MOFs—based on electron para-
magnetic resonance (EPR) spectroscopy of MOF-bound superox-
3
2, 47-48
•
-
partition of substrates/products between MOF channels.
ide (O2 ) and fluorescence spectroscopy of MOF-bound N-
methylacridone (NMA)—and a simple strategy that significantly
enhances MOF Lewis acidity through ligand perfluorination. Two
new perfluorinated MOFs, Zr -fBDC and Zr -fBPDC, where
The objectives of this work are to develop quantitative methods to
determine the Lewis acidity of MOFs and to discover effective
strategies to enhance their Lewis acidity. Significant enhancement
of Lewis acidity of MOFs can afford porous solid catalysts with
much larger pores and channels than zeolites for fine chemical
synthesis.
6
6
H fBDC is 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylic acid and
2
H fBPDC
2
is
2,2’,3,3’,5,5’,6,6’-octafluoro-4,4’-
biphenyldicarboxylic acid, were shown to be significantly more
Lewis acidic than non-substituted UiO-66 and UiO-67 as well as
the nitrated MOFs Zr -BDC-NO and Zr -BPDC-(NO ) . Zr -
6
2
6
2 2
6
fBDC was shown to be a highly active single-site solid Lewis acid
catalyst for Diels-Alder and arene C-H iodination reactions. Thus,
this work establishes the important role of ligand perfluorination
in enhancing MOF Lewis acidity and the potential of designing
highly Lewis acidic MOFs for fine chemical synthesis.
INTRODUCTION
Metal-organic frameworks (MOFs) have emerged as a novel class
1
-16
of single-site solid catalysts in the past few years.
MOFs are
typically endowed with catalytic activity either through covalent
incorporation of catalytically active species into the organic lig-
1
7-19
ands or the inorganic nodes
or through entrapment of metal
enzymes , or inorganic clusters in the chan-
One class of MOF catalysts distinguishes itself from
20-21
22
nanoparticles,
23-24
nels.
other catalysts by using the inorganic nodes as single-site catalytic
centers. The metal centers in these MOFs feature unique elec-
tronic properties and steric environments that are not accessible to
2
5-
conventional homogeneous or heterogeneous catalytic species.
2
7
In this context, early demonstrations of MOF catalysis took
2
8-29
advantage of Lewis acidity of the metal-connecting points,
but these MOFs are relatively unstable and do not possess high
catalytic activities. The advent of highly stable MOFs based on
0
30-31
early metals of d electronic configurations
brought about
porous solid catalysts with enhanced Lewis acidity for a number
3
2-33
34
of catalytic reactions such as isomerization,
hydrolysis, and
35
36-39
dehydration among others.
Figure 1. Framework structures and bridging ligands of two se-
ries of MOFs isostructural to UiO-66 and UiO-67 with defect
Zr O (OH) nodes studied in this work. Electron-deficient nitrated
and perfluorinated bridging ligands increase Lewis acidity of Zr
centers within defect nodes.
4
0-46
Despite recent progress,
existing MOFs exhibit significant-
ly lower Lewis acidity than homogeneous systems such as
6
4
4
Sc(OTf) . In contrast to homogeneous systems, where Lewis acid-
3
ity at the active sites can be precisely measured, no techniques are
currently available to quantitatively assess Lewis acidity of MOF
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We report here the development of two general methods for
tion of EPR and fluorescence methods to a variety of Lewis acidic
MOFs, especially the MOFs with defect Zr O (OH) nodes, has
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determining Lewis acidity of MOFs. The first method probes
Lewis acidity through the coordination of in situ generated super-
oxide which displays diagnostic electron paramagnetic resonance
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4
4
unveiled a strong correlation between dicarboxylate electron den-
sity and Zr O (OH) Lewis acidity. Based on this insight, we have
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4
(
EPR) features. The second method probes the Lewis acidity
significantly enhanced the Lewis acidity of Zr-MOFs using per-
fluorinated bridging ligands to afford porous solid catalysts for
challenging transformations typically effected by strongly Lewis
acidic homogeneous catalysts (Figure 1).
through the binding of a fluorescent dye with strongly coordina-
tive electron lone pairs. We prepared a series of UiO MOFs
featuring defect Zr O (OH) inorganic nodes with missing linkers
and unsaturated coordination around Zr active sites.
49
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Applica-
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Figure 2. Synthesis of defect Zr -fBDC (a) and Zr -fBPDC (b) from ZrOCl ·8H O and perfluorinated linkers. The missing organic linkers
give rise to unsaturated coordination around the Zr nodes. The coordination environments of the Zr active sites are approximately Zr(ꢀ -
O) (ꢀ -OH) (L) (OH ) in these two MOFs (L is fBDC or fBPDC).
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lated to be Zr (ꢀ -O) (ꢀ -OH) (fBDC) [(OH)(OH )]2.66. The
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4.67
2
RESULTS AND DISCUSSION
Synthesis and Characterization of Perfluorinated MOFs. We
have synthesized two perfluorinated UiO-MOFs, Zr -fBDC and
defect density of Zr -fBDC is slightly larger than that of defect
6
UiO-66, which was reported to be 0.7 missing linkers per Zr6
6
node, presumably due to the relatively weaker coordination
61
Zr -fBPDC, by replacing 1,4-benzenedicarboxylate (BDC) in Zr -
strength of the fBDC ligand to the Zr node. The structure of
6
6
6
BDC (UiO-66) and 4,4’-biphenyldicarboxylate (BPDC) ligands in
Zr -BPDC (UiO-67) with 2,3,5,6-tetrafluoro-1,4-
benzenedicarboxylate (fBDC) and 2,2’,3,3’,5,5’,6,6’-octafluoro-
4
2
of ZrOCl ·8H O and H fBDC in acidic tetrahydrofuran (THF) at
8
Zr -fBDC is isostructural to UiO-66 (Figure S6, SI). The porosity
of Zr -fBDC was confirmed by N sorption isotherms, which
displayed a Brunauer-Emmett-Teller (BET) surface area of 1021
m /g. DFT fitting of the N sorption isotherms of Zr -fBDC gave
pore sizes of ~6 and ~8 Å that are attributable to the tetrahedral
and octahedral cages of the UiO structure, respectively (Figure
S7, SI), in addition to a larger pore at ~12 Å due to the missing
fBDC ligands. The surface area of Zr -fBDC is lower than that of
UiO-66 due to the increased formula weight in the perfluorinated
MOF (1875 Da for Zr -fBDC vs 1664 Da for UiO-66). Unlike
previously reported perfluorinated MOFs,
high thermal stability with a decomposition temperature of 380 °C
as measured by thermal gravimetric analysis (TGA, Figure S8,
SI). A combination of F NMR and ICP-MS techniques showed
Zr -fBDC was unaltered after desolvation and catalysis based on
6
6
the retention of the Zr -fBDC PXRD patterns.
6
Zr -fBPDC, a UiO-67 analogue of Zr -fBDC with larger chan-
6
6
,4’-biphenyldicarboxylate (fBPDC) ligands, respectively (Figure
nels, was prepared similarly. The H fBPDC linker was synthe-
2
). Zr -fBDC was synthesized in 86% yield by heating a mixture
sized by CuCl -mediated oxidative aryl-aryl coupling of the me-
6
2
2
2
2
thyl tetrafluorobenzoate organozinc reagent followed by ester
0 °C. Powder X-ray diffraction (PXRD) studies indicated that
6
hydrolysis (Figure S1, SI). Zr -fBPDC was synthesized in 90%
6
yield by heating a mixture of ZrOCl ·8H O and H fBPDC in acid-
2
2
2
6
2
ic THF at 80 °C. The PXRD pattern of Zr -fBPDC matched well
6
with the simulated pattern for UiO-67, indicating their isostruc-
tural nature (Figure S11, SI). Compared to Zr -fBDC, Zr -fBPDC
2
2
6
6
6
2
has a larger BET surface area of 1148 m /g while maintaining
high thermal stability with a decomposition temperature of 310 °C
as measured by TGA (Figure S12-13, SI). Zr -fBPDC displayed
6
6
two types of pores at ~12 and ~15 Å, corresponding to the tet-
rahedral and octahedral cages, respectively, and a larger pore
6
at ~22 Å due to the missing fBPDC ligands. The number of
5
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19
Zr -fBDC features
6
missing linkers per Zr node was determined by F NMR and
6
ICP-MS to be 1.73 per Zr6 node, giving the formula Zr (ꢀ -
6
3
O) (ꢀ -OH) (fBPDC) [(OH)(OH )]
for Zr -fBPDC (Figure
4
3
4
4.27
2
3.46
6
19
S10, SI).
the number of missing linkers to be 1.33 per Zr node (Figure S5,
SI). Based on this information, the formula of Zr -fBDC is calcu-
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Synthesis and Characterization of Nitrated MOFs
Zr -BDC-NO and Zr -BPDC-(NO ) were synthesized to com-
pare their Lewis acidity with those of perfluorinated MOFs. Zr6-
similarity of their PXRD patterns (Figure S21, SI). The porosity
of The Zr -BPDC-(NO ) was confirmed by N2 sorption iso-
therms, affording a BET surface area of 1205 m /g and pore di-
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6
2
6
2 2
6
2 2
2
BDC-NO was prepared from H BDC-NO and ZrOCl ·8H O in
ameters of ~12, ~15, and ~22 Å (Figure S22, SI).
2
2
2
2
2
acidified DMF. PXRD studies indicated its isostructural nature
with UiO-66. N sorption isotherms of Zr -BDC-NO afforded a
2
6
2
Probing Lewis acidity by superoxide EPR spectra
2
BET surface area of 960 m /g and pore diameters of ~6, ~8, and
Spectroscopic measurements of MOFs, such as UV-vis, fluores-
cence and EPR measurements, have been challenging as the sig-
nals tend to be weak and noisy owing to poor dispersibility of and
strong scattering by MOFs. One solution to this problem is to
~
12 Å (Figure S18, SI). The similar porosity of Zr -BDC-NO and
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2
Zr -fBDC makes them a good pair to study the impact of Lewis
6
acidity on catalytic performance without the complication of
varying diffusion kinetics through MOF channels. The number of
utilize probes that have high sensitivity toward photon excitations.
1
•-
missing linkers was determined by H NMR and ICP-MS to be
We have chosen superoxide (O
2
) and N-methylacridone (NMA)
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.94 per Zr node, thus giving Zr -BDC-NO the formula Zr (ꢀ -
as two sensitive probes to assess the Lewis acidity of MOFs. Su-
peroxide ions display strong EPR signals and NMA is a highly
emissive fluorescent dye. More importantly, their signals are sen-
sitive to the Lewis acidity of binding metal ions. These probes
were pioneered by Fukuzumi and coworkers for studying Lewis
acidity of soluble metal salts. In this work, we show for the first
time that EPR of MOF-bound superoxide and fluorescence of
MOF-bound NMA provide sensitive indicators for the Lewis
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2
6
3
O) (ꢀ -OH) (BDC-NO ) [(OH)(OH )] (Figure S16, SI). The
defect density of Zr -BDC-NO is essentially the same as that of
Zr -fBDC.
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4
2 5.06
2
1.88
6
2
6
Zr -BPDC-(NO ) with larger channels was synthesized in 85%
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2 2
49
yield by heating a mixture of H BPDC-(NO ) and ZrOCl ·8H O
in acidified THF at 80 °C. The H BPDC-(NO ) ligand was syn-
thesized in high yield using the Pd-catalyzed Suzuki-Miyaura
cross-coupling reaction followed by ester hydrolysis (Figure S4,
SI). Zr -BPDC-(NO ) is isostructural to UiO-67 based on the
2
2 2
2
2
2
2 2
acidity
of
MOFs.
6
2 2
•-
Figure 3. (a) Proposed mechanism for the superoxide binding to the defect Zr sites in Zr
6
-fBDC. (b) Zr(O
2
6 6
) EPR spectra of Zr -BDC (black), Zr -BDC-
•-
NO
2
(red), and Zr
6
-fBDC (blue). (c) Zr(O
2
) EPR spectra of Zr
6
-BPDC(black), Zr
6
-BPDC-(NO (red), and Zr -fBPDC (blue). (d) DFT optimized superox-
2
)
2
6
•
-
ide binding mode on Zr
6
2
-fBDC-O .
•-
-
singly occupied molecular orbital (SOMO) of the O2•- π* orbitals.
Superoxide ions (O ) can be generated in situ by the 1 e re-
2
duction of O using the dimeric 1-benzyl-1,4-dihydronicotinamide
The ꢁE is related to the g value following the Känzig-Cohen
2
zz
•-
63
[
(BNA) ] as a photoreductant. The photo-generated O2 is very
equation. Metal centers with stronger Lewis acidity should split
2
small and easily diffuses through the MOF channel before
quenching. Additionally, O2 is very electron-rich and has a
strong binding affinity to Lewis acids such as the defect Zr sites
in UiO-MOFs. O2 binds to Zr active sites by displacing the
weakly coordinating H O molecule to form the EPR-active
Zr(O ) species (Figure 3a). Lewis acid coordination significantly
changes the EPR signature of O . The rhombic g-tensor of the
EPR spectrum, most evidently the g component, is diagnostic of
the binding strength between O2 and the Lewis acid. This effect
is due to coordination of the electron pair in the highest doubly
occupied molecular orbital (HOMO) of the O2 π* orbitals, which
increases the energy splitting (ꢁE) between the HOMO and the
the π* orbitals to a greater extent, thus giving larger ꢁE values.
The EPR spectra of superoxide ions bound to a variety of UiO
MOFs were measured on a Bruker Elexsys 500 X-band EPR
spectrometer at 100 K. A clear trend was observed for the meas-
ured gzz values. UiO MOFs grown from more electron-deficient
dicarboxylates, namely those with electron-withdrawing groups,
showed smaller gzz values for the anisotropic EPR spectra, indi-
cating larger ꢁE values. Zr -BDC produced a g value of 2.0344,
•-
•-
2
•-
2
•-
2
zz
6
zz
•-
62
which corresponds to a ꢁE of 0.8735 eV. This ꢁE is the smallest
value in the UiO-66 MOF series in this study. The Zr -BDC-NO
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2
•-
MOF, which was previously reported to catalyze (+)-citronellal
32
isomerization, showed a smaller gzz value of 2.0330, which cor-
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responds to a larger ꢁE of 0.9114 eV. Impressively, Zr -fBDC
2.193 and 2.231 Å, with a small degree of binding asymmetry.
6
exhibited a gzz of 2.0324 and a ꢁE of 0.9304 eV, making it the
most Lewis acidic MOF in the UiO-66 series.
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This effect was tentatively rationalized through electronic struc-
ture analysis of the π* orbital, which displayed significant anti-
symmetric repulsive interactions between the carboxylate electron
lone pair and the superoxide π* electrons, thus leading to the
To validate the trend observed for the UiO-66 series, two new
MOFs of UiO-67 topology were prepared. Zr -BPDC showed a
6
gzz of 2.0343 and a ꢁE of 0.8743 eV, similar to that of Zr -BDC.
elongation of one of the Zr-O bonds (Figure S33, SI). Comparison
6
•-
Zr -BPDC-(NO ) gave a g of 2.0334 and a ꢁE of 0.9014 eV.
of the Zr(O
2
) bond distances in the Zr
6
-BDC and Zr
6
-fBDC
to different
Zr centers. Indeed, the Zr-O distances in Zr -fBDC are 2.18 and
6
2 2
zz
•-
The perfluorinated MOF, Zr -fBPDC, is much more Lewis acidic
models offered insight into the binding strength of O
2
6
with a gzz of 2.0326 and a ꢁE of 0.9246 eV. These experiments
prove that perfluorination is an effective way to enhance Lewis
acidity of UiO-MOFs with defect Zr O (OH) nodes.
6
2.21 Å, shorter than those in Zr -BDC (2.19 and 2.23 Å). This
6
computational result verified that electron withdrawing groups on
the organic linker increase the Lewis acidity of Zr sites in defect
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•-
UiO-MOFs, as indicated by the higher Zr(O ) binding strength.
Density Functional Theory (DFT) Calculations of Superoxide
Binding on Zr Active Sites
2
The enhancement of MOF Lewis acidity by installing electron
withdrawing groups on the linker was also verified by DFT
through calculation of ꢁE values. The molecular orbital diagram
•-
of a Zr(O ) fragment in the Zr -BDC model structure was ana-
2
6
lyzed by biorthogonalization (Figure S32). We have clearly ob-
•-
served that the bonding orbitals for the O significantly over-
2
4+
lap with the Zr orbitals. This observation is indicative of strong
•-
binding of O2 onto the Zr center, and not simply electrostatic
attachment. The SOMO and HOMO molecular orbital eigenval-
ues were calculated using restricted open shell calculations (Fig-
ure 4a). The energy gap between the HOMO and SOMO is corre-
lated to the ꢁE measured from EPR analysis. We have observed
that the HOMO-SOMO energy gaps increase in the following
order: Zr -BDC ≈ Zr -BPDC < Zr -BDC-NO < Zr -BPDC-
6
6
6
2
6
(
NO ) < Zr -fBPDC < Zr -fBDC (Figure 4; Figure S34-38, SI).
2 2 6 6
A linear relationship between the calculated ꢁE
with the EPR
DFT
2
measured ꢁE was observed with an adjusted R of 0.953 (Figure
b). Thus, DFT calculations support the proposal that electron-
withdrawing groups on the MOF ligand significantly increase the
4
•-
binding strength of O2 on the MOF node.
DFT calculations were also used to elucidate the impact of de-
fect density on MOF Lewis acidity. For Zr -fBDC, two additional
6
models for superoxide-bound MOF nodes, one with two missing
•-
carboxylates (Zr -fBDC-2def- O ) and another with three miss-
6
2
•-
ing carboxylates (Zr -fBDC-2def- O ), were optimized and ana-
6
2
lyzed for SOMO-HOMO gaps (Section 5.3, SI). The superoxide
moieties in the doubly or triply defected models adopt identical
coordination modes as the singly defected model and produced
identical SOMO-HOMO gaps of 2.84 eV (Figure S39-42, SI).
The inclusion of more defects, unlike the exchange of carbox-
ylates, does not alter the primary coordination environment
around Lewis acidic Zr centers.
•
-
Figure 4. (a) Molecular orbital diagram for Zr(O ) in the model
2
•
-
structure. The HOMO-SOMO gap for Zr -BDC-O , indicated by
6
2
Probing Lewis acidity by NMA fluorescence
•-
the dotted line, is 2.74 eV. (b) The linear relationship between ꢁE
values calculated by DFT, ꢁE , and ꢁE values measured by
Although O2 is an accurate indicator of MOF Lewis acidity, the
DFT
2
experimental procedures for superoxide generation and EPR
measurement are lengthy and tedious. Therefore, we have also
used NMA fluorescence to probe Lewis acidity of MOFs. NMA is
a commercially-available fluorescent dye, which features lone
pairs that can effectively bind to vacant metal sites in MOFs. The
fluorescence maxima (λmax) of NMA shifts significantly upon
binding to metal centers. These shifts are indicative of the binding
affinity of the probe to the metals and thus can be used as a meas-
ure of Lewis acidity. A large excess of Lewis acids is typically
used with respect to NMA to avoid the emission of non-
coordinated NMA molecules. The fluorescence spectra of NMA
coordinated to three different UiO-66 MOFs are shown in Figure
EPR, ꢁEEPR, with an adjusted R of 0.953.
Density functional theory (DFT) calculations were carried out to
gain insight into the coordination mode and electronic structure of
O2 bound to Zr nodes. To reduce the computational expense,
only the three ligands that were directly connected to the Zr(O )
species were allowed to fully relax. The corresponding linkers
and clusters were optimized at the M06 level of theory. All oth-
er dicarboxylate ligands were replaced with acetates and held
fixed.(Section 5.1, SI) The optimized structures for the models of
all six MOFs showed a side-on binding mode of the O2 on the
Zr node (Figure 3d). The side-on coordination is analogous to the
•-
6
•-
2
64
•-
6
5
c-d. In the case of Zr -BDC and Zr -BDC-NO , the λ
of
6
6
2
max
one generally proposed for superoxide ions bound to a zirconia
NMA changed dramatically from 433.0 nm to 466.4 nm and
469.0 nm, respectively, upon coordination of the dye to defect Zr
65
•-
(
ZrO ) surface. For the Zr -BDC-O model structure, the O-O
2 6 2
•-
distance at the Zr(O ) site is 1.301 Å, longer than the O-O dis-
2
sites. Zr -fBDC shifted the NMA emission wavelength the most,
6
•-
tance in a free O2 species (1.28 Å). This is presumably due to the
weakening of the O-O bond by the coordination to Zr centers.
Interestingly, the Zr-O bond distances in Zr -BDC-(O ) are
with a λmax of 470.6 nm. The same trend was observed for the
three UiO-67 MOFs, where the Zr -fBPDC shifted the NMA
•-
6
6
2
4
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emission wavelength the most, with a λmax of 469.6 nm. We also
orbital, which is proposed to be responsible for the NMA coordi-
nation to Zr (Figure S43, SI).
1
2
3
4
5
6
7
8
9
found that the λmax of Zr-bound NMA was linearly related to the
ꢁE measured from the EPR method, with an adjusted R-squared
value of 0.954. A fitted empirical relationship (Figure 5e) be-
tween the λmax and ꢁE was obtained and used to calculate the
NMA fluorescence-derived ꢁE values (ꢁENMA) for every MOF.
The ꢁENMA values were compared with the EPR-measured ꢁE
values to check the reliability of the fluorescence method. The
λmax, ꢁENMA and ꢁE for each of the six different MOFs are sum-
marized in Table 1. The ꢁENMA consistently reproduces the EPR-
measured ꢁE, indicating that the fluorescence dye is a convenient
probe for assessing Lewis acidity in MOFs.
To exclude the possibility that the Brønsted acidic ꢀ -OH (pKa
3
66
~ 3.52) might have caused the shift in the NMA emission, a
series of Brønsted acids (trifluoroacetic acid, benzoic acid, acetic
acid, and 4-aminobenzoic acid) covering the pKa range of -0.25 ~
4
.86 were mixed with NMA in MeCN to measure fluorescence.
None of the four acids caused any shift in the NMA emission
spectra, indicating Brønsted acids are not responsible for the
shifts in NMA fluorescence in the UiO series (Figure S27, SI).
For weak Lewis acids that have ꢁE values less than 0.5 eV, NMA
cannot coordinate to the metal centers effectively thus leading to
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
49
almost no shift in emission wavelength. Two common Lewis
The coordination mode and electronic structure of NMA bound
67-68
acidic MOFs, MOF-5 and HKUST-1,
displayed no shift in the
to the Zr node was also studied by DFT. The optimized structure
6
NMA fluorescence, indicating the Zn O node in MOF-5 and the
4
showed that the carbonyl group (instead of the aryl or nitrogen) is
Cu node in HKUST-1 have ꢁE values less than 0.5 eV (Figure
2
coordinated to the vacant site of the Zr node, adopting a side-on
6
S29, SI).
coordination mode. Molecular orbital calculations of the NMA
fluorescent dye revealed the electronic structure of the HOMO
Figure 5. (a) The coordination of NMA dye to the Zr defect sites in Zr
dination mode of NMA on the Zr node of Zr
blue) in MeCN at 298 K. (d) Fluorescence spectra of NMA binding to Zr
K. (e) Linear relationship between the EPR measured ꢁEEPR and the DFT calculated ꢁEDFT
6
-fBDC, leading to a dramatic shift in the emission maxima. (b) DFT optimized coor-
6
6
-BDC. (c) Fluorescence spectra of NMA binding to Zr
6
-BDC (black), Zr
6
2 6
-BDC-NO (red), and Zr -fBDC
(
6
-BPDC (black), Zr -BPDC-(NO
6
2
)
2
(red), and Zr
6
-fBPDC (blue) in MeCN at 298
.
synthesis of six-member ring structures with high regioselectivity
69-70
and stereoselectivity.
However, the reaction generally requires
Table 1. List of the fluorescence maxima (λmax), calculated
•-
high temperatures and long reaction times when performed with-
out the addition of an acid catalyst. Unlike classical Lewis acidic
metal complexes, MOF catalysts benefit from having uniform
active sites which can lead to better reaction selectivity. The solid
nature of MOFs offers additional advantages, including easy sepa-
ration from reaction mixtures and catalyst reusability. For the
cyclization of 1,4-benzoquinone with 2,3-dimethylbuta-1,3-diene,
only 4% yield of product was observed in the absence of catalyst
ꢁ
ENMA from NMA λmax, and ꢁEEPR measured from Zr-(O ) EPR
2
spectra.
ꢁ
ENMA
MOFs
λmax (nm)
ꢁEEPR (eV)
(eV)
Zr -BDC
466.4
469.0
470.6
465.5
468.4
469.6
0.8788
0.9121
0.9326
0.8673
0.9044
0.9200
0.8735
0.9114
0.9304
0.8743
0.9014
0.9246
6
Zr -BDC-NO2
6
Zr -fBDC
6
Zr -BPDC
6
at 25 °C after 2 h (entry 1, Table 2). In the presence of Zr -BDC,
6
Zr -BPDC-(NO )
6
2 2
which has been shown to be active for ethanol dehydration at 250
Zr -fBPDC
6
35
°
C, the product yield increased to 14% under the same reaction
conditions (entry 2, Table 2). Zr -BDC-NO , which is reported to
6
2
be active for (+)-citronellal isomerization at 100 °C, increased the
reaction yield to 25% at the same reaction condition (entry 3,
Perfluorinated MOF-Catalyzed Diels-Alder Reactions
The synthesis of perfluorinated Zr-MOFs and the characterization
of their prominent Lewis acidity inspired the investigation of their
catalytic activities. We first tested perfluorinated Zr MOFs for
Diels-Alder reactions.
The Diels-Alder reaction is of great synthetic value to the or-
ganic chemistry community and has been widely applied to the
Table 2). Under the same reaction conditions, Zr -fBDC afforded
6
the cycloaddition product in 78% yield. Elongation of the reaction
time from 2 h to 8 h further increased the yield to 98%. Consider-
ing Zr -fBDC has a higher density of defect sites, additional con-
6
trol experiments were performed by increasing the catalyst load-
5
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Page 6 of 9
ing of Zr -BDC and Zr -BDC-NO to the same loading of defect
hexa-1,3-diene and 2,3-dimethylbuta-1,3-diene at 25 °C to afford
6
6
2
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
sites as Zr -fBDC. However, Zr -fBDC still afforded the product
6
6
cycloaddition products in 74% and 84% yields, respectively.
at much higher yield than Zr -BDC and Zr -BDC-NO in these
Moreover, Zr -fBDC was reused for at least three runs without
6
6
2
6
experiments (Table S5, SI). The reaction is proposed to be initiat-
ed by the coordination of the lone pair electrons of the quinones
to the Zr centers. This coordination is expected to lower the ener-
gy of the LUMO orbital to enhance the overlap with the HOMO
orbital of the dienes. The coordination of quinones to Zr is pro-
posed to be analogous to the coordination of NMA to Zr, since
they both contain electron-rich carbonyl groups.
significant loss of catalytic activity for the cyclization of 2,3-
dimethylbuta-1,3-diene with 2-chloro-1,4-benzoquinone (Figure
S44, SI).
Perfluorinated MOF-Catalyzed Arene C-H Iodination Reac-
tions
Aryl iodides are very useful building blocks in organic synthesis.
The C-I bonds of arenes readily undergo cross-coupling reactions
72-73
Table 2. Catalyst evaluation and substrate scope of Zr -fBDC
and nucleophilic substitutions.
There are multiple synthetic
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
a
catalyzed Diels-Alder reactions.
methods to access these compounds, including the Sandmeyer
reaction, halide exchange reactions, and electrophilic substitu-
tions. The most straightforward method is the direct C-H io-
74-75
dination using iodine or N-iodosuccinimide (NIS).
Many acid
catalysts have been developed to perform such reactions, notably
the BF -H O system reported by Olah and co-workers which
3
2
7
6
could iodinate very challenging electron-deficient arenes. For
electron-rich arenes, however, many catalysts suffer from poor
Product
Catalyst
Time
2 h
Yield
4 %
regioselectvity, leading to the formation of multi-iodinated prod-
1
2
3
4
5
No catalyst
77
ucts. Zr -fBDC was tested for the iodination of anisole at 25°C
6
Zr -BDC
2 h
14 %
25 %
78 %
98 %
6
using MeCN as the solvent. These conditions afforded exclusively
the mono-idodination product in 96% yield after 30 h. Other arene
substrates, such as 2-methoxynaphthalene, aniline, and N-
methylaniline, were also iodinated in high yields with excellent
regioselectivity (entry 5-8, Table 3).
Zr -BDC-NO
6
2 h
2
Zr -fBDC
6
2 h
Zr -fBDC
6
8 h
Table 3. Catalyst evaluation and substrate scope of Zr -fBDC
6
a
catalyzed C-H iodination reactions.
6
7
8
Zr -fBDC
12 h
24 h
30 h
94 %
99 %
95 %
6
Zr -fBDC
6
Product
Catalyst
Time
12 h
12 h
12 h
Yield
10 %
16 %
28 %
1
2
3
No catalyst
Zr -BDC
6
Zr -fBDC
6
Zr -BDC-NO2
6
4
Zr -fBDC
6
12 h
85 %
5
6
Zr -fBDC
18 h
30 h
81 %
96 %
9
Zr -fBDC
48 h
48 h
84 %
74 %
6
6
Zr -fBDC
6
7
Zr -fBDC
2 h
2 h
95 %
93 %
6
1
0
Zr -fBDC
6
a
Reaction conditions: dienophile (1 equiv., 1 mmol), diene (1.2
equiv.), Zr MOFs (5 mol%, 0.05 mmol), CH Cl (3.0 mL), 25 °C.
8
Zr -fBDC
6
2
2
1
Reaction yields were determined from H NMR using mesitylene
as an internal standard.
a
Reaction conditions: arenes (1 equiv., 0.5 mmol), N-
iodosuccinimide (1.1 equiv.), Zr MOFs (4 mol%, 0.02 mmol),
The MOF-catalyzed Diels-Alder reaction displayed a broad
substrate scope (entry 5-10, Table 2). Cyclohexa-1,3-diene, a less
reactive diene than cyclopentadiene or 2,3-dimethylbuta-1,3-
diene, was cyclized with 1,4-benzoquinone in 94% yield in 12h in
1
MeCN (1.5 mL), 25 °C. Reaction yields were determined from H
NMR using mesitylene as an internal standard.
7
1
The catalytic performance of Zr -fBDC was compared to other
6
the presence of 5 mol% Zr -fBDC. Quinone substrates contain-
6
MOFs to show the importance of ligand perfluorination. At iden-
tical reaction conditions and catalyst loading, Zr -BDC and Zr -
ing electron-donating groups, such as the 2-methyl-1,4-
benzoquinone, are generally less reactive in Diels-Alder reactions
due to their much higher LUMO energy. The presence of a me-
thyl group also greatly increases the steric hindrance of the qui-
none substrate. Impressively, in the presence of 5 mol% Zr6-
fBDC, 2-methyl-1,4-benzoquinone efficiently reacted with cyclo-
6
6
BDC-NO only iodinated 2-methoxynaphthalene in 16% and 28%
2
yield, respectively, while Zr -fBDC gave 85% yield of the 3-
6
iodinated product. Even when the catalyst loadings of Zr -BDC
6
and Zr -BDC-NO were increased to the same loading of defect
6
2
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Journal of the American Chemical Society
sites as Zr -fBDC, the yields of product were still much lower
2. Lee, J.; Farha, O. K.; Roberts, J.; Scheidt, K. A.; Nguyen, S. T.;
Hupp, J. T., Chem. Soc. Rev. 2009, 38, 1450-1459.
3. Ingleson, M. J.; Barrio, J. P.; Bacsa, J.; Dickinson, C.; Park, H.;
Rosseinsky, M. J., Chem. Commun. 2008, 1287-1289.
4. Wang, Z.; Cohen, S. M., Chem. Soc. Rev. 2009, 38, 1315-1329.
5. Uemura, T.; Yanai, N.; Kitagawa, S., Chem. Soc. Rev. 2009,
38, 1228-1236.
6
1
2
3
4
5
6
7
8
9
than that of Zr -fBDC (Table S6, SI). Other Lewis acidic MOF
6
catalysts, e.g., MOF-5 and HKUST-1, also displayed much lower
catalytic performance than Zr -fBDC (Table S8). Impressively,
6
Zr -fBDC could be recycled at least 6 times without a significant
6
drop in catalytic activity, illustrating the robustness of the solid
Lewis acid catalyst (Figure S47, SI).
6
. Liu, Y.; Xuan, W.; Cui, Y., Adv. Mater. 2010, 22, 4112-4135.
CONCLUSION
7. Alexandra, F.; A., C. P.; P., I. C.; A., T. A.; Z., K. Y.; V., W.
P.; R., D. J.; J., R. M., Angew. Chem. 2012, 124, 7558-7562.
8. Yoon, M.; Srirambalaji, R.; Kim, K., Chem. Rev. 2012, 112,
1196-1231.
9. Gu, Z. Y.; Park, J.; Raiff, A.; Wei, Z.; Zhou, H. C.,
ChemCatChem 2014, 6, 67-75.
10. Liu, J.; Chen, L.; Cui, H.; Zhang, J.; Zhang, L.; Su, C.-Y.,
Chem. Soc. Rev. 2014, 43, 6011-6061.
11. Zhao, M.; Ou, S.; Wu, C.-D., Acc. Chem. Res. 2014, 47, 1199-
1207.
12. Jiang, J.; Gándara, F.; Zhang, Y.-B.; Na, K.; Yaghi, O. M.;
Klemperer, W. G., J. Am. Chem. Soc. 2014, 136, 12844-12847.
13. Choi, K. M.; Na, K.; Somorjai, G. A.; Yaghi, O. M., J. Am.
Chem. Soc. 2015, 137, 7810-7816.
14. Chen, Y. Z.; Wang, C.; Wu, Z. Y.; Xiong, Y.; Qiang, X.; Yu,
S. H.; Jiang, H. L., Adv. Mater. 2015, 27, 5010-5016.
15. Xiao, D. J.; Oktawiec, J.; Milner, P. J.; Long, J. R., J. Am.
Chem. Soc. 2016, 138, 14371-14379.
We developed two general methods for quantifying the Lewis
acidity of MOFs by measuring the changes in superoxide EPR
signals and shifts of NMA fluorescence peaks upon their coordi-
nation to MOFs. We prepared a series of UiO-MOFs featuring
defect Zr O (OH) nodes with missing linkers and unsaturated
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
6
4
4
coordination around Zr active sites. The application of the EPR
and fluorescence methods to a variety of MOFs unveiled a strong
correlation between dicarboxylate electron density and
Zr O (OH) Lewis acidity, leading to the discovery of significant-
6
4
4
ly enhanced Lewis acidity within Zr-MOFs containing perfluori-
nated bridging ligands. The new perfluorinated MOFs, Zr -fBDC
6
and Zr -fBPDC, are significantly more Lewis acidic than non-
6
substituted UiO-66 and UiO-67 as well as the nitrated MOFs Zr6-
BDC-NO and Zr -BPDC-(NO ) . Zr -fBDC was shown to be a
2
6
2 2
6
highly active Lewis acid catalyst for Diels-Alder and arene C-H
iodination reactions. This work, thus, establishes the important
role of ligand perfluorination in enhancing MOF Lewis acidity
and the potential of designing new, highly Lewis acidic MOFs as
single-site porous solid catalysts for fine chemical synthesis.
16. Metzger, E. D.; Comito, R. J.; Hendon, C. H.; Dincă, M., J.
Am. Chem. Soc. 2017, 139, 757-762.
1
7. Zhang, T.; Manna, K.; Lin, W., J. Am. Chem. Soc. 2016, 138,
ASSOCIATED CONTENT
3241-3249.
18. Manna, K.; Ji, P.; Lin, Z.; Greene, F. X.; Urban, A.; Thacker,
N. C.; Lin, W., Nat. Commun. 2016, 7, 12610.
1
Vermeulen, N. A.; Cramer, C. J.; Gagliardi, L.; Hupp, J. T.;
Farha, O. K., J. Am. Chem. Soc. 2016, 138, 14720-14726.
Supporting Information
This material is available free of charge via the Internet at
http://pubs.acs.org. Synthesis and characterization of the ligands
and MOFs; procedures for DFT calculations; procedures for the
superoxide binding and fluorescent dye binding; procedures for
the Diels-Alder reactions and regioselective C-H iodination reac-
9. Noh, H.; Cui, Y.; Peters, A. W.; Pahls, D. R.; Ortuño, M. A.;
2
0. Na, K.; Choi, K. M.; Yaghi, O. M.; Somorjai, G. A., Nano
Lett. 2014, 14, 5979-5983.
21. An, B.; Zhang, J.; Cheng, K.; Ji, P.; Wang, C.; Lin, W., J. Am.
Chem. Soc. 2017, 139, 3834-3840.
tions. Crystallographic data for Me fBPDC (CCDC 1845893).
2
AUTHOR INFORMATION
2
2. Lian, X.; Fang, Y.; Joseph, E.; Wang, Q.; Li, J.; Banerjee, S.;
Lollar, C.; Wang, X.; Zhou, H.-C., Chem. Soc. Rev. 2017, 46,
3
2
Corresponding Author
386-3401.
wenbinlin@uchicago.edu
3. Zhang, Z.-M.; Zhang, T.; Wang, C.; Lin, Z.; Long, L.-S.; Lin,
W., J. Am. Chem. Soc. 2015, 137, 3197-3200.
Author Contribution
24. Fortea-Pérez, F. R.; Mon, M.; Ferrando-Soria, J.; Boronat, M.;
Leyva-Pérez, A.; Corma, A.; Herrera, J. M.; Osadchii, D.;
Gascon, J.; Armentano, D.; Pardo, E., Nat. Mater 2017, 16, 760.
P. J. and T. D. contributed equally.
Notes
2
5. Phan, A.; Czaja, A. U.; Gándara, F.; Knobler, C. B.; Yaghi, O.
M., Inorg. Chem. 2011, 50, 7388-7390.
6. Xiao, D. J.; Bloch, E. D.; Mason, J. A.; Queen, W. L.;
The authors declare no competing financial interest.
2
Hudson, M. R.; Planas, N.; Borycz, J.; Dzubak, A. L.; Verma, P.;
Lee, K.; Bonino, F.; Crocellà, V.; Yano, J.; Bordiga, S.; Truhlar,
D. G.; Gagliardi, L.; Brown, C. M.; Long, J. R., Nat. Chem. 2014,
ACKNOWLEDGMENT
6
, 590.
We thank Prof. John Anderson and Dr. Ethan Hill for help with
EPR measurements. This work was supported by NSF (CHE-
2
7. Ji, P.; Solomon, J. B.; Lin, Z.; Johnson, A.; Jordan, R. F.; Lin,
W., J. Am. Chem. Soc. 2017, 139, 11325-11328.
8. Fujita, M.; Kwon, Y. J.; Washizu, S.; Ogura, K., J. Am. Chem.
Soc. 1994, 116, 1151-1152.
9. Evans, O. R.; Ngo, H. L.; Lin, W., J. Am. Chem. Soc. 2001,
123, 10395-10396.
0. Bai, Y.; Dou, Y.; Xie, L.-H.; Rutledge, W.; Li, J.-R.; Zhou,
H.-C., Chem. Soc. Rev. 2016, 45, 2327-2367.
1. Yuan, S.; Qin, J.-S.; Lollar, C. T.; Zhou, H.-C., ACS Central
Science 2018, 4, 440-450.
2. Vermoortele, F.; Vandichel, M.; Voorde, B. V. d.; Ameloot,
1
464941). XAS analysis was performed at Beamline 10-BM. Use
2
of the Advanced Photon Source, an Office of Science User Facili-
ty operated for the U.S. DOE Office of Science by ANL, was
supported by the U.S. DOE under Contract No. DE-AC02-
2
0
6CH11357.
3
3
References
3
1
1
. Ma, L.; Abney, C.; Lin, W., Chem. Soc. Rev. 2009, 38, 1248-
256.
R.; Waroquier, M.; Speybroeck, V. V.; Vos, D. E. D., Angew.
Chem. Int. Ed. 2012, 51, 4887-4890.
7
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 8 of 9
3
3. Vermoortele, F.; Bueken, B.; Le Bars, G.; Van de Voorde, B.;
54. Cai, G.; Jiang, H. L., Angew. Chem. Int. Ed. 2017, 56, 563-
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Vandichel, M.; Houthoofd, K.; Vimont, A.; Daturi, M.;
Waroquier, M.; Van Speybroeck, V.; Kirschhock, C.; De Vos, D.
E., J. Am. Chem. Soc. 2013, 135, 11465-11468.
567.
55. Stefano, D.; Konstantin, E.; R., H. W.; Gregor, K.; A., F. R.,
Adv. Mater. 2018, 1704501.
56. Yang, C.; Wang, X.; Omary, M. A., J. Am. Chem. Soc. 2007,
129, 15454-15455.
57. Yang, C.; Wang, X.; Omary, M. A., Angew. Chem. Int. Ed.
2009, 48, 2500-2505.
3
4. Mondloch, J. E.; Katz, M. J.; Isley Iii, W. C.; Ghosh, P.; Liao,
P.; Bury, W.; Wagner, G. W.; Hall, M. G.; DeCoste, J. B.;
Peterson, G. W.; Snurr, R. Q.; Cramer, C. J.; Hupp, J. T.; Farha,
O. K., Nat. Mater 2015, 14, 512.
35. Yang, D.; Ortuño, M. A.; Bernales, V.; Cramer, C. J.;
Gagliardi, L.; Gates, B. C., J. Am. Chem. Soc. 2018, 140, 3751-
58. Chen, T.-H.; Popov, I.; Zenasni, O.; Daugulis, O.; Miljanic,
O. S., Chem. Commun. 2013, 49, 6846-6848.
59. Noro, S.-i.; Nakamura, T., Npg Asia Materials 2017, 9, e433.
60. Cheplakova, A. M.; Kovalenko, K. A.; Samsonenko, D. G.;
Lazarenko, V. A.; Khrustalev, V. N.; Vinogradov, A. S.; Karpov,
V. M.; Platonov, V. E.; Fedin, V. P., Dalton Trans. 2018, 47,
3283-3297.
61. Yang, D.; Odoh, S. O.; Borycz, J.; Wang, T. C.; Farha, O. K.;
Hupp, J. T.; Cramer, C. J.; Gagliardi, L.; Gates, B. C., ACS Catal.
2016, 6, 235-247.
62. Sobańska, K.; Krasowska, A.; Mazur, T.; Podolska-Serafin,
K.; Pietrzyk, P.; Sojka, Z., Top. Catal. 2015, 58, 796-810.
63. Känzig, W.; Cohen, M. H., Phys. Rev. Lett. 1959, 3, 509-510.
64. Zhao, Y.; Truhlar, D. G., Theor. Chem. Acc. 2008, 120, 215-
241.
65. Bedilo, A. F.; Plotnikov, M. A.; Mezentseva, N. V.; Volodin,
A. M.; Zhidomirov, G. M.; Rybkin, I. M.; Klabunde, K. J., PCCP
2005, 7, 3059-3069.
66. Islamoglu, T.; Atilgan, A.; Moon, S.-Y.; Peterson, G. W.;
DeCoste, J. B.; Hall, M.; Hupp, J. T.; Farha, O. K., Chem. Mater.
2017, 29, 2672-2675.
67. Vishnyakov, A.; Ravikovitch, P. I.; Neimark, A. V.; Bülow,
M.; Wang, Q. M., Nano Lett. 2003, 3, 713-718.
68. Kaye, S. S.; Dailly, A.; Yaghi, O. M.; Long, J. R., J. Am.
Chem. Soc. 2007, 129, 14176-14177.
69. Nicolaou, K. C.; Snyder, S. A.; Montagnon, T.;
Vassilikogiannakis, G., Angew. Chem. Int. Ed. 2002, 41, 1668-
1698.
3
3
759.
6. Beyzavi, M. H.; Klet, R. C.; Tussupbayev, S.; Borycz, J.;
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Vermeulen, N. A.; Cramer, C. J.; Stoddart, J. F.; Hupp, J. T.;
Farha, O. K., J. Am. Chem. Soc. 2014, 136, 15861-15864.
3
7. Rasero-Almansa, A. M.; Iglesias, M.; Sanchez, F., RSC Adv.
2016, 6, 106790-106797.
38. Sang, X.; Zhang, J.; Xiang, J.; Cui, J.; Zheng, L.; Zhang, J.;
Wu, Z.; Li, Z.; Mo, G.; Xu, Y.; Song, J.; Liu, C.; Tan, X.; Luo, T.;
Zhang, B.; Han, B., Nat. Commun. 2017, 8, 175.
3
9. Ly, H. G. T.; Fu, G.; Kondinski, A.; Bueken, B.; De Vos, D.;
Parac-Vogt, T. N., J. Am. Chem. Soc. 2018, 140, 6325-6335.
0. Zou, R.-Q.; Sakurai, H.; Han, S.; Zhong, R.-Q.; Xu, Q., J. Am.
4
Chem. Soc. 2007, 129, 8402-8403.
41. Horike, S.; Dincǎ, M.; Tamaki, K.; Long, J. R., J. Am. Chem.
Soc. 2008, 130, 5854-5855.
4
2. Henschel, A.; Gedrich, K.; Kraehnert, R.; Kaskel, S., Chem.
Commun. 2008, 4192-4194.
3. Shultz, A. M.; Farha, O. K.; Hupp, J. T.; Nguyen, S. T., J. Am.
Chem. Soc. 2009, 131, 4204-4205.
4. Tanabe, K. K.; Cohen, S. M., Inorg. Chem. 2010, 49, 6766-
4
4
6774.
45. Srirambalaji, R.; Hong, S.; Natarajan, R.; Yoon, M.; Hota, R.;
Kim, Y.; Ho Ko, Y.; Kim, K., Chem. Commun. 2012, 48, 11650-
1
4
1652.
6. Jiang, Z. R.; Wang, H.; Hu, Y.; Lu, J.; Jiang, H. L.,
Chemsuschem 2015, 8, 878-885.
7. Alaerts, L.; Séguin, E.; Poelman, H.; Thibault‐Starzyk, F.;
Jacobs, P. A.; De Vos, D. E., Chem. Eur. J 2006, 12, 7353-7363.
8. Horcajada, P.; Surble, S.; Serre, C.; Hong, D.-Y.; Seo, Y.-K.;
7
0. Woodward, R. B.; Sondheimer, F.; Taub, D.; Heusler, K.;
4
McLamore, W. M., J. Am. Chem. Soc. 1952, 74, 4223-4251.
71. Ahrendt, K. A.; Borths, C. J.; MacMillan, D. W. C., J. Am.
Chem. Soc. 2000, 122, 4243-4244.
4
Chang, J.-S.; Greneche, J.-M.; Margiolaki, I.; Ferey, G., Chem.
Commun. 2007, 2820-2822.
7
7
4
7
2. Ma, D.; Cai, Q., Acc. Chem. Res. 2008, 41, 1450-1460.
3. Kambe, N.; Iwasaki, T.; Terao, J., Chem. Soc. Rev. 2011, 40,
937-4947.
4
9. Ohkubo, K.; Menon, S. C.; Orita, A.; Otera, J.; Fukuzumi, S.,
J. Org. Chem. 2003, 68, 4720-4726.
0. Katz, M. J.; Brown, Z. J.; Colon, Y. J.; Siu, P. W.; Scheidt, K.
A.; Snurr, R. Q.; Hupp, J. T.; Farha, O. K., Chem. Commun. 2013,
9, 9449-9451.
4. Racys, D. T.; Sharif, S. A. I.; Pimlott, S. L.; Sutherland, A., J.
5
Org. Chem. 2016, 81, 772-780.
75. Wu, J.; He, D.; Zhang, L.; Liu, Y.; Mo, X.; Lin, J.; Zhang, H.,
Org. Lett. 2017, 19, 5438-5441.
4
51. Wu, H.; Chua, Y. S.; Krungleviciute, V.; Tyagi, M.; Chen, P.;
Yildirim, T.; Zhou, W., J. Am. Chem. Soc. 2013, 135, 10525-
7
6. Prakash, G. K. S.; Mathew, T.; Hoole, D.; Esteves, P. M.;
Wang, Q.; Rasul, G.; Olah, G. A., J. Am. Chem. Soc. 2004, 126,
1
5
0532.
1
7
5770-15776.
2. Shearer, G. C.; Chavan, S.; Ethiraj, J.; Vitillo, J. G.; Svelle, S.;
7. Racys, D. T.; Warrilow, C. E.; Pimlott, S. L.; Sutherland, A.,
Olsbye, U.; Lamberti, C.; Bordiga, S.; Lillerud, K. P., Chem.
Mater. 2014, 26, 4068-4071.
Org. Lett. 2015, 17, 4782-4785.
5
3. A., T. C.; J., G. K.; Seungkyu, L.; Felipe, G.; Hans‐Beat, B.;
M., Y. O., Angew. Chem. Int. Ed. 2015, 54, 11162-11167.
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