Engineering a Zirconium MOF through Tandem "click" Reactions: A General Strategy for Quantitative Loading of Bifunctional Groups on the Pore Surface

Article abstract of DOI:10.1021/acs.inorgchem.7b03123

Metal-organic frameworks (MOFs) assembled from linkers of identical length but with different functional groups have gained increasing interests recently. However, it is very challenging for precise control of the ratios of different functionalities. Here

Full text of DOI:10.1021/acs.inorgchem.7b03123

Article
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
pubs.acs.org/IC
Engineering a Zirconium MOF through Tandem “Click” Reactions: A
General Strategy for Quantitative Loading of Bifunctional Groups on
the Pore Surface
Yingfan Zhang, Bo Gui, Rufan Chen, Guiping Hu, Yi Meng, Daqiang Yuan, Matthias Zeller,§
†
†
†
†
†
‡
,
†
and Cheng Wang*
†
College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China
‡
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences,
Fuzhou 350002, China
§
Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
S Supporting Information
*
ABSTRACT: Metal−organic frameworks (MOFs) assembled from linkers of identical length but with different functional
groups have gained increasing interests recently. However, it is very challenging for precise control of the ratios of different
functionalities. Herein, we reported a stable azide- and alkyne-appended Zr-MOF that can undergo quantitative tandem click
reactions on the different functional sites, thus providing a unique platform for quantitative loading of bifunctional moieties. As
an added advantage, the same MOF product can be obtained via two independent routes. The method is versatile and can
tolerate a wide variety of functional groups, and furthermore, a heterogeneous acid−base MOF organocatalyst was synthesized by
tandemly introducing both acidic and basic groups onto the predesigned pore surface. The presented strategy provides a general
way toward the construction of bifunctional MOFs with a precise control of ratio of different functionalities for desirable
applications in future.
INTRODUCTION
bringing heterogeneity into an MOF is appealing, it is always
difficult to control the proportion of each functionality via
direct solvothermal synthesis. Usually, once the initial solution
conditions change, their ratio will also change. As a result, the
synergistic behavior in the MOF may be affected. To the best of
our knowledge, up to this point only one MOF that displayed a
magic predefined ratio between the different functionalities has
■
As a new type of novel porous material with high permanent
porosity and structural tunability, metal−organic frameworks
1
,2
(
MOFs) have attracted intensive attention over the past two
3
−7
8−12
decades for applications in gas absorption,
separation,
1
3−20
21−23
24−26
catalysis,
sensors,
drug delivery,
energy stor-
2
7−29
age,
etc. Recently, multivariate MOFs (MTV-MOFs), in
37
been reported. In light of this challenge, the development of a
more general strategy for precise control of the ratio of different
functionalities in an MTV-MOF is highly desirable.
which a mixture of different linkers or nodes can serve the same
structural role throughout MOF crystal and thus may function
in a synergistic manner, have triggered substantial interest.
3
0−37
38−41
Postsynthetic modification (PSM),
which can introduce
In particular, many efforts have been focused on assembling
linkers with identical length but different functional groups into
new functional groups within the main molecular skeleton after
the MOF lattice is formed, has been widely used to
functionalize MOFs in recent years. In principle, this approach
3
4−37
one MOF.
For example, Yaghi and co-workers reported a
series of MTV-MOFs containing up to eight different
34
functionalities in one crystalline phase, and some of the
MTV-MOFs showed substantially better gas-separation proper-
ties than their best same-link counterparts. However, while
Received: December 15, 2017
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.7b03123
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Inorganic Chemistry
Article
a
Scheme 1. Synthesis and PSM of UiO-68-N /CC via Tandem Click Reactions from Two Different Routes
3
a
The topology is shown in simplified form as an octahedral cage.
1
Figure 1. H NMR (400 MHz, DMSO-d ) spectra of digested UiO-68-N /CC and other corresponding Zr-MOFs obtained through PSM.
6
3
can provide a reasonable route to synthesize MTV-MOFs with
a precise ratio of different functionalities. Starting from linkers
bearing different functional groups that can be further modified,
the obtained MTV-MOF with fixed ratio can be used as a
platform for precise loading of new functional groups through
PSM. For example, by modulating the percentage of amino-
quantitative, the ratio of incorporated new functionalities
cannot keep consistent with that of the initial MOF.
Accordingly, the proportion of each functionality is still not
controllable, and further improvements are needed.
The copper(I)-catalyzed azide−alkyne cycloaddition
(CuAAC) “click” reaction, which provides a highly reliable
means to quantitatively establish covalent connections between
building blocks containing different functional groups, has been
widely employed in organic synthesis, medicinal chemistry,
42
and bromo-functionalized ligands used in an MOF synthesis,
Cohen and co-workers reported a series of mixed-ligand MOFs,
which can subsequently undergo PSM reactions on the
orthogonal functional sites to generate a wide variety of
MTV-MOFs. However, as the yield of PSM reactions is not
43−45
material science, etc.
Over the past 10 years, this reaction
has proven to be ideally suited for PSM of MOFs, as long as the
B
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Inorganic Chemistry
Article
pore size is sufficiently large enough to allow the reagents and
46−49
catalysts to reach the anchor positions inside the MOF.
For example, Zhou et al. reported several highly stable azide-
48
tagged zirconium MOFs (Zr-MOFs), which offered an ideal
platform for quantitative pore surface engineering with a variety
49
of alkynes. Our group reported an alkyne-tagged Zr-MOF,
which can be functionalized with different azide compounds in
quantitative yield. Since the click reaction can proceed
efficiently with quantitative yields and high specificity in the
presence of various functional groups, if an MTV-MOF bearing
both azide and alkyne groups can be obtained, it should provide
a unique platform for quantitative loading of different
functionalities via tandem PSM.
Figure 2. FT-IR spectra of UiO-68-N /CC and other correspond-
3
With these considerations in mind, we report herein the
design and synthesis of a stable bifunctional Zr-MOF (UiO-68-
ing Zr-MOFs obtained through PSM. The disappearance of
−1
−1
characteristic peak at ∼3286 cm (alkyne group) and ∼2100 cm
N /CC, Scheme 1), which has both accessible azide and
3
(azide group) indicates the complete click reaction.
alkyne groups on the inner pore surface with an ∼1:1 ratio.
This Zr-MOF can undergo quantitative tandem click reactions
on the tandem functional sites while retaining the framework,
thus providing a unique platform for quantitative loading of
bifunctional groups. Interestingly, these tandem click reactions
can be performed on two independent routes, leading to the
same MOF product. Moreover, by using this tandem strategy,
we were able to decorate the pore surface with both acidic and
basic functionalities, leading to the formation of a heteroge-
neous acid−base MOF organocatalyst.
RESULTS AND DISCUSSIONS
■
To design a highly stable azide- and alkyne-appended Zr-MOF
with large cavities for quantitative loading of bifunctional
groups, we chose the reported 2′,5′-bis(azidomethyl)-
Figure 3. PXRD patterns of UiO-68-alkyne, UiO-68-N /CC and
3
other corresponding Zr-MOFs obtained through PSM. Obviously, the
frameworks were well-retained during PSM process.
48
[
1,1′:4′,1″-terphenyl]-4,4″-dicarboxylic acid (1) and 2′,5′-
49
diethynylterphenyl-4,4″-dicarboxylic acid (2) as mixed ligands
and ZrCl as the metal salts. We aimed to construct Zr-MOFs
4
because of its robustness compared with more commonly used
50−52
Zn/Cu-centered MOFs.
After the treatment of a reaction
mixture containing ZrCl , ligand 1, ligand 2, acetic acid, and
4
N,N-dimethylformamide (DMF) in a preheated 80 °C oven for
7
2 h, UiO-68-N /CC was obtained as octahedron-shaped
3
53
crystals in reasonable yield. The structure and composition of
UiO-68-N /CC were determined by several techniques. As
3
1
shown in Figure 1 and Figure S1, the H NMR spectrum of
digested UiO-68-N /CC is the same as the combination of
3
ligand 1 and ligand 2, indicating the intactness of ligands in the
MOF. On the basis of the integrals for the particular resonances
of methylene proton and alkyne proton, the ratio of ligand 1 to
ligand 2 was calculated to be ∼1:1. The Fourier transform
Figure 4. N sorption properties at 77 K for UiO-68-N /CC and
2
3
other corresponding Zr-MOFs obtained through PSM.
infrared (FT-IR) spectrum of activated UiO-68-N /CC
3
−1
displayed two peaks at 2100 and 3286 cm (Figure 2),
characteristic for the azide and alkyne groups. In addition, UiO-
the same MOF product (Scheme 1). We first studied the
tandem PSM of UiO-68-N /CC through Route A. After the
3
6
8-N /CC was shown to possess typical UiO-68 structure,
crystals were treated with phenylacetylene in the presence of
3
with its powder X-ray diffraction (PXRD) pattern identical to
catalytic CuI at 60 °C in DMF for 24 h, UiO-68-Ph(1)/CC
1
that reported for UiO-68-alkyne (Figure 3). Moreover, nitrogen
was isolated with a quantitative yield. From the H NMR
gas sorption at 77 K demonstrated that UiO-68-N /CC
spectrum of digested UiO-68-Ph(1)/CC (Figure 1 and
Figure S5), all the azide groups of ligand 1 in the framework
were quantitatively transformed to the corresponding triazole
derivative, while ligand 2 was retained. This was further
confirmed by the high-resolution electrospray ionization mass
(HR-ESI-MS) spectrum of digested sample (Figure S6), which
displayed two peaks that can be assigned to the corresponding
triazole derivative and ligand 2. In addition, the characteristic IR
3
displayed a type I gas sorption isotherm (Figure 4), with a high
2
Brunauer−Emmett−Teller (BET) surface area up to 3260 m
−
1
g .
The highly porous structure of UiO-68-N /CC should
3
allow the inside azide and alkynyl groups accessible. To assess
this applicability, PSM of UiO-68-N /CC was performed
3
through independent and tandem click reactions with both
azide and alkyne groups. In principle, there are two routes for
performing such tandem click reactions, which should lead to
band for the azide group in UiO-68-N /CC disappeared
3
completely (Figure 2), indicating a complete click reaction.
C
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Inorganic Chemistry
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Scheme 2. Synthesis of UiO-68-Ac/Ba and UiO-68-Es/Ba through PSM of UiO-68-N /CC
3
We then investigated the PSM of UiO-68-Ph(1)/CC with
azidomethylbenzene in the presence of CuI at 60 °C in DMF.
After 24 h, UiO-68-Ph(1)/Ph(2)-(A) was also isolated in
quantitative yield. Similarly, the characteristic IR band for the
alkyne group in UiO-68-Ph(1)/CC disappeared (Figure 2),
tandem click reactions of UiO-68-N /CC with but-3-ynoic
3
acid and then (R)-2-(azidomethyl)pyrrolidine. In addition, we
also synthesized UiO-68-Es/Ba from methyl propiolate and
then (R)-2-(azidomethyl)pyrrolidine, for a control experiment.
All of the modified Zr-MOFs shown in Scheme 2 were
characterized by several techniques (Figures S11−S15),
confirming the successful loading of bifunctional groups with
1
indicating a complete click reaction. From the H NMR
spectrum of digested UiO-68-Ph(1)/Ph(2)-(A) (Figure 1 and
Figure S5), all of the alkyne groups in ligand 2 were also
quantitatively transformed to the corresponding triazole
derivative, which was further confirmed by HR-ESI-MS
experiment (Figure S6). By integrating the resonance peak
intensities, both of the corresponding triazole derivatives in
UiO-68-Ph(1)/Ph(2)-(A) have the same ratio (∼1:1) as that of
the same ratio (∼1:1) as that of original UiO-68-N /CC.
3
We then investigated the catalytic performance of UiO-68-
Ac/Ba, by choosing the aldol addition of cyclohexanone with 4-
nitrobenzaldehyde as a model reaction (Table 1). To a mixture
a
Table 1. Catalytic Studies for Aldol Addition of 4-
Nitrobenzaldehyde and Cyclohexanone with Different Zr-
MOFs
UiO-68-N /CC, indicating the quantitative loading of
3
bifunctional groups.
Following the same procedure, we also tested the tandem
PSM of UiO-68-N /CC via Route B (Scheme 1). As
3
confirmed by several different characterization techniques
(
Figures 1 and 2, Figures S7 and S8), UiO-68-N /CC can
3
also be quantitatively transformed to first UiO-68-N /Ph(2)
and then to UiO-68-Ph(1)/Ph(2)-(B) via tandem click
reactions. Once again, from the H NMR spectra (Figure 1),
both of the corresponding triazole derivatives in UiO-68-
b
c
3
catalyst
mass (mg)
M
(% mmol)
yield (%)
UiO-68-Ac/CC
UiO-68-Es/Ba
UiO-68-Ac/Ba
5.1
5.9
6.2
∼1.1
∼1.0
∼1.1
13
32
95
1
Ph(1)/Ph(2)-(B) have a ratio of ∼1:1, the same as that of the
a
Reaction conditions: 40 °C, 60 h, 0.13 mmol of 4-nitrobenzaldehyde,
.3 mmol of cyclohexanone, 200 μL of H O. Relative to 4-
nitrobenzaldehyde. Determined by H NMR
starting UiO-68-N /CC.
b
3
1
2
From the PXRD analysis (Figure 3), all of the modified Zr-
MOFs shown in Scheme 1 displayed high crystallinity,
indicating the frameworks were retained during these PSM
processes. In addition, the BET surface area value (Figure 4)
c
1
of cyclohexanone, 4-nitrobenzaldehyde, and H O, a certain
2
amount of UiO-68-Ac/Ba (∼1% based on 4-nitrobenzalde-
2
−1
for the modified MOFs decreased to 2100 m g and then to
1
to 2385 m g and then to 1310 m g , confirming their
microporosity. Therefore, via the two independent PSM routes,
hyde) was added. After the suspension was shaken at 40 °C for
2
−1
385 m g through Route A, whereas in Route B it decreased
6
0 h, the expected aldol product was formed with a conversion
2
−1
2
−1
yield up to 95%, based on the integration of corresponding
NMR resonance peak intensities (Figure S19). On the basis of
chiral high-performance liquid chromatography (HPLC), four
different aldol adduct isomers were determined (Figure S20),
with dr-value of 35:65 (syn/anti). In addition, we tested the
stability and recyclability of the UiO-68-Ac/Ba catalyst, by
subjecting it to three cycles of the aldol reaction. It shows low
variation in yields ranging from initially 95% down to 91% after
three cycles (Table S3), and the framework was retained during
this process (Figure S21). To test the influence of reactant size,
we repeated the reaction with a larger molecule, 2-
UiO-68-N /CC can be quantitatively transformed to the
3
same bifunctional Zr-MOF product, without loss of crystallinity
or porosity. More importantly, the ratio of incorporated
bifunctional struts is the same as that of the initial UiO-68-
N /CC, confirming the quantitative loading.
3
To further demonstrate the potential application of this
strategy, we decided to construct a heterogeneous acid−base
Zr-MOF, which may function as a synergistic catalyst. By using
Route A, we synthesized UiO-68-Ac/Ba (Scheme 2), through
D
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Article
naphthaldehyde instead of 4-nitrobenzaldehyde, under other-
wise identical conditions. Only a low conversion of ca. 9% was
observed after reaction for 7 d (Figure S22), demonstrating that
the catalytic reaction with the smaller 4-nitrobenzaldehyde did
indeed occur within the pores of UiO-68-Ac/Ba.
To prove that the catalytic behavior of UiO-68-Ac/Ba was
ascribed to the cooperation of the acid sites and base sites, we
performed several control experiments, by studying the catalytic
performance of UiO-68-Ac/CC and UiO-68-Es/Ba under
the same reaction condition. As shown in Table 1, UiO-68-Ac/
CC with acid sites gave a yield of only 13%, where UiO-68-
Es/Ba with base sites showed a slightly higher yield of 32%,
respectively. Therefore, the high catalytic activity of UiO-68-
Ac/Ba can be ascribed to the incorporation of both acidic sites
calculate the BET surface area were subject to the consistency criteria
5
6
detailed by Walton and Snurr. FT-IR spectra were recorded on a
Bruker TENSOR-27 infrared spectrometer using KBr pellets.
Enantiomeric excesses were determined by HPLC analysis (Daicel
Chiralcel AD-H column) in comparison with racemic products. The
absolute configurations of the products were determined by
57
comparison with compounds previously published.
MOFs Activation. The MOF crystals were allowed to immerse in
DCM several times to replace and remove DMF and were then
evacuated in oil pump vacuum at room temperature.
1
MOFs Digestion and H NMR Study. In a typical procedure, ∼5 mg
of activated MOF was digested with heating in ∼1 mL of deuterated
dimethyl sulfoxide (DMSO-d ) and 20 μL of DCl aqueous solution.
6
1
The digested solution was used directly for H NMR, and a big peak
from solvent was observed from approximately 4.8 to 5.2 ppm.
Synthesis of UiO-68-N /CC. ZrCl (17.7 mg, 0.076 mmol),
3
4
and basic sites into UiO-68-N /CC through tandem click
3
ligand 1 (17.2 mg, 0.040 mmol), ligand 2 (14 mg, 0.038 mmol), and
acetic acid (680 μL) were ultrasonically dissolved in DMF (2.4 mL)
and then placed in a preheated 80 °C oven for 72 h. Single crystals
with octahedral shape were harvested with a yield of ∼28 mg. The
crystals were rinsed with DMF to remove unreacted starting materials
reactions, indicating the powerful promise of this unique
strategy.
CONCLUSION
In conclusion, we have synthesized a highly stable bifunctional
■
1
and then kept in DMF for further use. From the H NMR spectrum of
digested sample (Figure 1 and Figure S1), the ratio of ligands 1 and 2
was determined to be ∼1:1. In addition, both ligands 1 and 2 can be
found in HR-ESI-MS spectrum of digested sample (Figure S2). By
using the same method, we also synthesized several MOFs starting
from ligand 1 and ligand 2 with different ratios. These MOFs were also
characterized by several techniques (Figures S3 and S4), and the ratio
Zr-MOF (UiO-68-N /CC), with accessible azide and alkyne
3
groups, in an ∼1:1 ratio. This Zr-MOF can provide a unique
platform for anchoring bifunctional groups with precise ratio
control (∼1:1) on the pore surface, via tandem click reactions
on the tandem functional sites. As an added advantage, the
same bifunctional MOF product can be obtained through two
independent PSM routes. Since a series of Zr-MOFs with
different ratios of azide and alkyne groups can be synthesized
by modulating the initial ratio utilized in the solvothermal
1
of two ligands was determined (Table S1) from the H NMR spectra
of digested samples.
Synthesis of UiO-68-Ph(1)/CC. Phenylacetylene (0.1 mL, 0.9
mmol) was added to a mixture of UiO-68-N /CC (∼60 mg) and
3
5
3
synthesis, we also envision that it is possible for quantitative
loading of bifunctional groups with other ratios in an MOF.
Moreover, acid and base groups have been tandemly
introduced onto the predesigned pore surface from this
platform, leading to the formation of a heterogeneous acid−
base MOF organocatalyst. Therefore, we strongly believe our
design strategy provides a general way toward the construction
of bifunctional MOF with a precise control of the ratio of
different functionalities for desirable applications. The con-
struction of other bifunctional MOFs with cooperative
functionality for other applications is ongoing in our lab.
CuI (5.0 mg) in DMF (4.0 mL). The reaction mixtures were kept at
60 °C under N atmosphere for 24 h without stirring. The resultant
2
octahedral crystals were collected, washed with DMF, and then kept in
1
DMF for further modification. From H NMR spectrum of digested
sample (Figure 1 and Figure S5), UiO-68-Ph(1)/CC was obtained
in quantitative yield. Moreover, both components can be found in the
HR-ESI-MS spectrum of digested sample (Figure S6).
Synthesis of UiO-68-Ph(1)/Ph(2)-(A). Azidomethylbenzene (0.1
mL, 0.8 mmol) was added to a mixture of activated UiO-68-Ph(1)/
CC (∼50 mg) and CuI (4.0 mg) in DMF (4.0 mL). The reaction
mixtures were kept at 60 °C under N atmosphere for 24 h without
2
stirring. The resultant octahedral crystals were collected by
1
centrifugation and then washed with DMF. From H NMR spectrum
EXPERIMENT SECTION
(Figure 1 and Figure S5) of digested sample, UiO-68-Ph(1)/Ph(2)-
■
(A) was obtained in quantitative yield. Moreover, the HR-ESI-MS
General Methods. 4-Methoxyl carbonylphenylboronic acid, 1,4-
dibromo-2,5-dimethylbenzene, sodium azide, N-bromosuccinimide,
phenylacetylene, methyl propiolate, but-3-ynoic acid, and benzoylper-
oxide were purchased from AK Scientific, Inc. Pd(PPh ) was bought
spectrum (Figure S6) of digested sample showed a major peak that
should be assigned to both components, as they have same molecular
weight.
3
4
Synthesis of UiO-68-N /Ph(2). Azidomethylbenzene (0.1 mL, 0.8
3
from Aladdin. Zirconium(IV) chloride was purchased from Alfa Aesar.
Triisopropylsilane and copper(I) iodide were purchased from Adamas.
mmol) was added to a mixture of UiO-68-N /CC (∼60 mg) and
3
4
8
49
54
CuI (5.0 mg) in DMF (4.0 mL). The reaction mixtures were kept at
Ligand 1, ligand 2, (R)-2-(azidomethyl)pyrrolidine, and
55
60 °C under N atmosphere for 24 h without stirring. The resultant
azidomethy benzene were synthesized according to the literature
2
octahedral crystals were collected, washed with DMF, and then kept in
procedure.
1
1H and 13C NMR spectra were measured on a Bruker Fourier 400
DMF for further modification. From H NMR spectrum of digested
sample (Figure 1 and Figure S7), UiO-68-N /Ph(2) was obtained in
M spectrometer. High-resolution mass spectra were collected on
Bruker Daltonics Inc. APEXII FT-ICR mass spectrometer, which was
equipped with EI, ESI, and MALDI as ionization source. PXRD data
were recorded on a Rigaku Smartlab 9KW diffractometer operated at
3
quantitative yield. Moreover, both components can be found in the
HR-ESI-MS spectrum of digested sample (Figure S8).
Synthesis of UiO-68-Ph(1)/Ph(2)-(B). Azidomethylbenzene (0.1
mL, 0.9 mmol) was added to a mixture of activated UiO-68-N /Ph(2)
4
5 kV, 200 mA for Cu Kα (λ = 1.5406 Å) with a scan speed of 5°/min
3
and a step size of 0.01° in 2θ at ambient temperature and pressure.
Thermogravimetric analysis from 30 to 800 °C was performed on a
DTA-60 Simultaneous DTG-TG Apparatus (Shimadzu) in air
atmosphere using a 10 °C/min ramp without equilibration delay.
The nitrogen adsorption and desorption isotherms were measured at
(∼50 mg) and CuI (4.0 mg) in DMF (4.0 mL). The reaction mixtures
were kept at 60 °C under N atmosphere for 24 h without stirring. The
2
resultant octahedral crystals were collected by centrifugation and then
1
washed with DMF. From the H NMR spectrum of digested sample,
UiO-68-Ph(1)/Ph(2)-(B) was obtained in quantitative yield (Figure 1
and Figure S7). Moreover, the HR-ESI-MS spectrum of digested
sample (Figure S8) showed a major peak that should be assigned to
both components, as they have the same molecular weight.
7
7 K using a Quantachrome Nova 4200e surface area and pore size
analyzer. Before measurement, the samples were degassed under
vacuum at room temperature for 12 h. The isotherm points chosen to
E
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Synthesis of UiO-68-Ac/CC. But-3-ynoic acid (50 mg, 0.6 mmol)
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.7b03123.
■
was added to a mixture of UiO-68-N /CC (∼60 mg) and CuI (5.0
3
*
S
mg) in DMF (4.0 mL) in a glass tube. The reaction mixtures were kept
at 60 °C under N atmosphere for 30 h without stirring. The resultant
2
octahedral crystals were collected, washed with DMF, and then kept in
1
DMF for further use. From the H NMR spectrum of digested sample
(
Figure S11), UiO-68-Ac/CC was obtained in quantitative yield.
Characterization details and catalytic experiments (PDF)
Moreover, both components can be found in the HR-ESI-MS
spectrum of digested sample (Figure S12).
AUTHOR INFORMATION
Corresponding Author
E-mail: chengwang@whu.edu.cn.
ORCID
■
Synthesis of UiO-68-Ac/Ba. (R)-2-(Azidomethyl)pyrrolidine (0.1
mL, 0.9 mmol) was added to a mixture of UiO-68-Ac/CC (∼50
mg) and CuI (5.0 mg) in DMF (4.0 mL) in glass tube. The reaction
*
mixtures were kept at 60 °C under N atmosphere for 24 h without
2
stirring. The resultant octahedral crystals were collected, washed with
DMF, and then kept in DMF for further use. From the H NMR
Daqiang Yuan: 0000-0003-4627-072X
Cheng Wang: 0000-0003-0326-2674
Notes
1
spectrum of digested sample (Figure S11), UiO-68-Ac/Ba was
obtained in quantitative yield. Moreover, both components can be
found in the HR-ESI-MS spectrum of digested sample (Figure S12).
Synthesis of UiO-68-Es/CC. Methyl propiolate (0.1 mL, 1.1
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We gratefully acknowledge the financial support from the
National Natural Science Foundation of China (21572170,
■
mmol) was added to a mixture of UiO-68-N /CC (∼60 mg) and
3
CuI (5.0 mg) in DMF (4.0 mL) in a glass tube. The reaction mixtures
were kept at 60 °C under N atmosphere for 30 h without stirring. The
2
2
1772149), the Research Fund for the Doctoral Program of
resultant crystals were collected, washed with DMF, and then kept in
1
Higher Education of China (20130141110008), the Funds for
Creative Research Groups of Hubei Province (2017CFA002),
and the Beijing National Laboratory for Molecular Sciences.
DMF for further use. From the H NMR spectrum of digested sample
(
Figure S13), UiO-68-Es/CC was obtained in quantitative yield.
Moreover, both components can be found in the HR-ESI-MS
spectrum of digested sample (Figure S14).
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8-Ac/Ba as catalyst was further purified by flash chromatography in
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F
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