Porous metal-organic framework catalyzing the three-component coupling of sulfonyl azide, alkyne, and amine

Article abstract of DOI:10.1021/ic4012229

The robustly porous metal-organic framework MOF-Cu₂I ₂(BTTP4) (BTTP4 = benzene-1,3,5-triyl triisonicotinate) was shown to work as an efficiently heterogeneous catalyst for the three-component coupling of sulfonyl azides, alkynes, and

Full text of DOI:10.1021/ic4012229

Article
pubs.acs.org/IC
Porous Metal−Organic Framework Catalyzing the Three-Component
Coupling of Sulfonyl Azide, Alkyne, and Amine
Tao Yang, Hao Cui, Changhe Zhang, Li Zhang,* and Cheng-Yong Su*
MOE Laboratory of Bioinorganic and Synthetic Chemistry/KLGHEI of Environment and Energy Chemistry, State Key Laboratory of
Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou
510275, P.R. China
S
* Supporting Information
ABSTRACT: The robustly porous metal−organic framework MOF−
Cu2I2(BTTP4) (BTTP4 = benzene-1,3,5-triyl triisonicotinate) was shown to
work as an efficiently heterogeneous catalyst for the three-component coupling
of sulfonyl azides, alkynes, and amines, leading to the formation of N-sulfonyl
amidines in good yields. MOF−Cu2I2(BTTP4) can be recycled by simple
filtration and reused at least four times without any loss in yield. Studies of the
ligand effects on the three-component coupling reactions showed that BTTP4
could enhance the rate, as well as the chemoselectivity, when aromatic alkynes
were employed. The catalytic process has been thoroughly studied by means of
single-crystal and powder X-ray diffraction, gas and solvent adsorption, in situ 1H
NMR and FT-IR spectroscopy, X-ray photoelectron spectra (XPS), and ICP analysis of Cu leaching.
ligands such as benzimidazole, triazole, and pyridine could
accelerate CuI-catalyzed reactions.34,35 Taking these consid-
erations into account, we are interested in the self-assembly of
CuI−MOFs using commercially available CuI and N-
heterocyclic tripodal ligands with the desire to develop porous
MOFs potentially possessing ligand-accelerated catalytic
activity.
1. INTRODUCTION
In the past decade, crystalline metal−organic frameworks
(MOFs), also called porous coordination polymers (PCPs),
have attracted considerable interest due to their intrinsic
properties such as high internal surface area and micro/meso
porosity. They are regarded as promising porous materials that
are able to mimic zeolite catalysts with specific shape- and/or
size-selectivity. Since the 1990s, a large number of MOFs have
been examined as heterogeneous catalysts.1−8 Among many
strategies for synthesizing catalytic MOFs, direct incorporation
of a homogeneous catalyst into a linker ligand and the grafting
of an organocatalyst onto a metal node have become the most
promising approaches toward efficiently building hetereoge-
neous catalysts.9−15 Within both strategies, the metal nodes are
the building units rather than the catalytic sites.
We are interested in the development of catalytic MOFs, in
which the metal nodes can act as the catalytic sites and promote
the reactions leading to the formation of valuable prod-
ucts.16−24 We found that the CuI ion is an adequate metal
candidate, which prefers to generate coordination hosts with
low coordination numbers (usually from 2- to 3-coordination),
while allowing additional metal−guest interactions due to its
flexible coordination environment (up to 5).25−27 Its potential
redox activity is essential for a variety of catalytic reactions.
Therefore, construction of porous CuI−MOFs may provide a
convenient approach to heterogeneously self-support catalysts
with CuI ions acting as both metal nodes and catalytic sites. CuI
also plays an important role in many conventional catalytic
reactions, especially in the remarkable click reactions28,29 and
the multicomponent coupling reactions.30−33 On the other
hand, careful investigations into catalytic activity, as well as
detailed mechanistic studies, show that nitrogen-containing
In light of this strategy, our group recently developed a
robust, porous CuI-based MOF, Cu2I2(BTTP4) (BTTP4 =
benzene-1,3,5-triyl triisonicotinate, hereafter designated as
MOF−Cu2I2(BTTP4)).25 After fully characterizing this MOF
by single-crystal X-ray crystallography, thermogravimetry and
variable-temperature powder X-ray diffraction (PXRD), and
gas/vapor adsorption, we believe that MOF−Cu2I2(BTTP4)
could be an ideal MOF structural model (Figures 1 and S1) for
application in heterogeneous catalysis due to the following
considerations: (i) it has a large free volume of 1776.9 Å3,
which amounts to 43% of the unit cell volume; (ii) it has large
one-dimensional channels (9 × 12 Å2) after considering the van
der Waals radii, which can be completely evacuated to leave
permanent porosity for guest molecule access; (iii) the metal
core is a Cu2I2 cluster, which contains one four-coordinating
CuI center in a CuI2N2 tetrahedral geometry and one three-
coordinating CuI center in a CuI2N trigonal geometry,
providing an unsaturated metal site to be exposed in the cavity
for potential catalytic reactions; and (iv) the empty framework
has been proven to preferentially include aromatic guests over
nonaromatics easily through a solid-solution diffusion/exchange
process. These features may make MOF−Cu2I2(BTTP4) a
Received: May 16, 2013
Published: July 25, 2013
© 2013 American Chemical Society
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reaction (based on phenylacetylene) was monitored by 1H NMR every
10 min.
3. RESULTS AND DISCUSSION
3.1. Catalytic Performances of MOF−Cu2I2(BTTP4).
Recently, Chang and co-workers discovered that CuI can
promote three-component coupling of sulfonyl azides, alkynes,
and amines to generate N-sulfonyl amidines, which are
prominent structural motifs in numerous natural bioactive
products.30 Encouraged by this important finding, we were
interested in exploring if the MOF−Cu2I2(BTTP4) can be used
to promote the three-component coupling in a heterogeneous
way. Compared to the conventional heterogeneous catalysts
based on polymer supports, self-supported porous MOFs as
heterogeneous catalysts are expected to display superior shape-
and/or size-selectivity because they provide a platform to carry
out catalytic reactions within their cavities.1−7 According to our
previous adsorption and guest exchange studies, MOF−
Cu2I2(BTTP4) exhibited good gas and solvent adsorptive
capacity and facile aromatic guest inclusion behavior, and it had
the capability to take in two aromatic molecules such as
benzene, toluene, and ethylbenzene per Cu2I2 unit through a
diffusion/exchange process via the solid-solution interface.25
This paves the way for testing the catalytic capability of MOF−
Cu2I2(BTTP4) in the three-component coupling reactions,
especially for those with aromatic alkynes. To our delight, a
series of aromatic alkynes can take part in the catalytic reactions
(entries 1−7, Table 1). It is noted that due to the highest
stability of MOF−Cu2I2(BTTP4) in CH3CN, we herein chose
CH3CN as the reaction media rather than THF because it was
proven to be the best solvent for naked CuI-catalyzed
reactions.30 In all cases, N-tosylamidines were formed as the
sole products, whereas tosyltriazoles have not been detected.
Chang and Fokin discovered that tosyltriazoles might become
the major products when the CuI-catalyzed reactions occurred
at lower temperature (e.g., 0 °C) in CHCl3 and in the absence
of amines.36 We also found that if the CuI-catalyzed three-
component coupling reaction among tosylazide (Ts−N3),
phenylacetylene (PhCCH), and diisopropylamine ((i-
Pr)2NH) proceeded in 1:1 CH3CN/CHCl3, the chemo-
selectivity of N-tosylaldimine (1a) and tosyltriazole (1b) was
changed to 3:1 (more information will be discussed in the next
section). The molecular structures of amidines 1a and 4a have
been unambiguously determined by single-crystal X-ray
crystallographic analyses, which disclosed an E-form of the
generated CN double bond (Figures S11 and S12), the same
as the transformation catalyzed by naked CuI.30
Figure 1. Molecular structure of the ligand BTTP4, 1D channels in
MOF−Cu2I2(BTTP4), and representation of catalytic behaviors.
platform to carry out reactions in the framework channels and
to display shape- and/or size-selective catalytic capability.
Herein, we employ MOF−Cu2I2(BTTP4) to the three-
component coupling reactions of sulfonyl azides, alkynes, and
amines (Figure 1).30 To the best of our knowledge, this is the
first report of the application of a MOF catalyst into the
synthesis of amidines.
2. EXPERIMENTAL SECTION
2.1. General Information. All the reagents in the present work
were obtained from the commercial source and used directly without
further purification. Infrared spectra on KBr pellets were collected with
a Nicolet/Nexus-670 FT-IR spectrometer in the region of 400−4000
cm−1. 1H NMR spectra were recorded with a Varian Mercury Plus 300
MHz spectrometer. The X-ray powder diffraction patterns were
measured on a Bruker D8 Advance diffractometer at 40 kV and 40 mA
with a Cu target tube and a graphite monochromator. The sorption
isotherms for CO2 (195 K) gas and CH3OH (298 K) vapor were
measured with a Micromeritics ASAP 2020 gas sorption analyzer. Prior
to the sorption examination, the samples are vacuumed at 35 °C for 16
h. Synthesis of MOF−Cu2I2(BTTP4) was completed according to our
previous procedure.25
2.2. Typical Procedure for the Three-Component Coupling
Reactions Catalyzed by MOF−Cu2I2(BTTP4). To CH3CN (1 mL)
in a vessel (10 mL) were added MOF−Cu2I2(BTTP4) (10 mg, 0.012
mmol), phenylacetylene (51.0 mg, 0.5 mmol), and tosyl azide (118
mg, 0.6 mmol). Then, diisopropylamine (60.6 mg, 0.6 mmol) was
added slowly to the above vessel. The whole reaction mixture was
allowed to stand at room temperature for 2 h. After that, the
supernatant was filtered through a thin pad of Celite and was
concentrated to dryness, which was followed by a flash chromatog-
raphy. A pure product of N,N-diisopropyl-2-phenyl-N′-tosylacetimid-
amide (1a) was obtained as an off-white solid (163.3 mg, 88%). Rf =
0.66 (EtOAc/hexane = 1/2). 1H NMR (300 MHz, CDCl3) δ: 7.82 (d,
J = 8.3 Hz, 2H), 7.31−7.18 (m, 7H), 4.41 (s, 2H), 3.97 (dt, J = 13.2,
6.7 Hz, 1H), 3.48−3.43 (m, 1H), 2.40 (s, 3H), 1.41 (d, J = 6.8 Hz,
6H), 0.89 (d, J = 6.6 Hz, 6H). IR (KBr, ν, cm−1): 2973, 2930, 1542,
1458, 1443, 1374, 1262, 1137, 1083, 754, 546 cm−1. MS (ESI) m/z:
calcd for C21H29N2O2S [M + H]+ 373.19; found, 373.11.
For comparison, N-tosylamidines were obtained with modest
yields from the reactions with alkyl alkynes (entries 8−12).
Especially, the yields of 10−12a were less than 60%, which
were obtained from the bulky alkynes (entries 10−12). In
contrast, the corresponding amidines in the CuI-catalyzed
reactions were isolated in high yields.30 For example, 10a was
obtained with 79% yield from the CuI-catalyzed reaction,
compared to a lower yield (51%, entry 10) in the presence of
MOF−Cu2I2(BTTP4).
We monitored the process of the catalytic transformations
with the preferable aromatic alkyne PhCCH over the less-
1
favored aliphatic alkyne t-BuCCH by in situ H NMR, as
2.3. Procedure for the Three-Component Coupling Reac-
1
shown in Figures 2 and S6−9. For comparison purposes, we
also monitored the process catalyzed by naked CuI. As shown
in Figure 2, in the presence of MOF−Cu2I2(BTTP4), the
reactions of PhCCH and t-BuCCH started with almost the
tions Monitored by In Situ H NMR. To a NMR tube were added
0.006 mmol MOF−Cu2I2(BTTP4) (or CuI), phenylacetylene (25.5
mg, 0.25 mmol), tosyl azide (59.3 mg, 0.3 mmol), diisopropylamine
(30.3 mg, 0.3 mmol), and CD3CN (0.5 mL). The conversion of the
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Table 1. Three-Component Coupling Reactions of Sulfonyl
Azide, Alkyne, and Amine Catalyzed by MOF−
a
Cu2I2(BTTP4)
Figure 2. Different catalytic behaviors of CuI and MOF−
Cu2I2(BTTP4).
transformation rate, and the reaction with t-BuCCH gave
slightly higher conversion under the same reaction time. The
induction period in the presence of MOF−Cu2I2(BTTP4) for
the t-BuCCH might be due to the slow diffusion of bulky t-
BuCCH into the pores of the MOF catalyst.
Besides the much more obvious size effect of MOF−
Cu2I2(BTTP4) catalysis compared to that of naked CuI-
catalyzed reactions, electronic variation of alkynes caused a big
change in the efficiency of the MOF−Cu2I2(BTTP4)-catalyzed
reactions (entries 4 vs 6). It is noted that the reaction with
electron-deficient alkyne ethyl propiolate generates amidine
14a and tosyltriazone 14b with 55 and 7% yield, respectively,
which was the only case in our system that a minor amount of
tosyltriazole was formed (entry 14). With respect to functional
group compatibility, a range of functional groups including
halide, alcohol, ester, and silyl functional groups were well-
tolerated in the MOF−Cu2I2(BTTP4)-catalyzed reactions.
Amines other than (i-Pr)2NH such as N-methylaniline
(Ph(Me)NH) and diphenylamine (Ph2NH) have also been
tested, and the results showed that the reactivity was in the
order of (i-Pr)2NH > Ph(Me)NH > Ph2NH (entries 1, 15, and
16).
To investigate whether the catalytic reactions are heteroge-
neous or homogeneous, we carried out a filtration experiment
(Figure 3). At the 45% conversion of the three-component
coupling of Ts−N3, PhCCH, and (i-Pr)2NH in the presence of
MOF−Cu2I2(BTTP4) for 40 min, the reaction mixture was
a
Reaction conditions: tosylazide, 118 mg, 0.6 mmol; alkynes, 0.5
mmol; amine, 0.6 mmol; MOF−Cu2I2(BTTP4), 10 mg, 0.012 mmol;
b
c
CH3CN, 1 mL. Triazole (7%) was found. Et3N (1.2 equiv to alkyne)
d
was added. Run for 6 h.
same initial conversion (less than 5%) in 10 min; however, they
led to the completion of 80 and 12%, respectively, in 50 min. At
this time, the biggest completion difference of 68% was evident
for these two substrates. In contrast, in the presence of CuI, the
reactions of PhCCH and t-BuCCH displayed almost the same
Figure 3. (a) Filtration experiment for MOF−Cu2I2(BTTP4).
■
Conversions are given as a function of time. The full square ( )
represents the reaction with MOF−Cu2I2(BTTP4) as a catalyst. (b)
□
The open square ( ) represents the reaction course after filtration of
the catalyst at 45% conversion.
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separated into two parts. One part of the reaction containing
the catalyst was allowed to react for another 80 min until the
reaction reached 100% conversion, whereas the remaining part
of the reaction was passed through a Celite pad (P4) to remove
the catalyst, and the supernatant was allowed to stand for 80
min. Compared to 100% completion for the part of the reaction
with the catalyst, it was found that the conversion of the
supernatant rose to 51% with only a 6% increase during the
same time. Based on the filtration experiment, we believe that
the reaction is basically heterogeneous, and we ascribe the
additional 6% conversion to the leached copper during the
reaction. Inductively coupled plasma optical emission spec-
trometer analysis of the reaction filtrate indicated that the
amount of the copper leaching into the reaction mixture was
3.0% of the total Cu content in the MOF−Cu2I2(BTTP4)
catalyst, corresponding to 1.888 ppm.
One remarkable feature of this three-component coupling
catalysis is that MOF−Cu2I2(BTTP4) crystals can be easily
isolated from the reaction suspension by simple filtration alone
and can be reused at least four times without any loss in yield
(Figure 4). As shown in Figure S2, the PXRD patterns recorded
Figure 5. Gas CO2 (195 K) and vapor CH3OH (298 K) adsorption/
desorption isotherms of MOF−Cu2I2(BTTP4) before and after
catalytic reactions.
retained after catalytic reactions (Figure S2). On the contrary,
the amount of CH3OH uptake before and after catalytic
reactions did not display a big difference and reach 9.1 and 8.0
wt %, corresponding to 2.6 and 2.3 CH3OH per Cu2I2 unit,
respectively. This means that although the Cu2I2 active sites
could be partially shielded by the remaining reactants or
products after catalytic reactions, the methanol molecules can
still access the framework pores due to the stronger interactions
between the pore surface and methanol molecules rather than
CO2 molecules.
Furthermore, we carried out the FT-IR experiments of
MOF−Cu2I2(BTTP4) before and after catalytic reactions
(Figure 6). By simply immersing as-synthesized MOF−
Cu2I2(BTTP4) crystals in a CH3CN solution of Ts−N3 at
room temperature for 2 h, the FT-IR spectrum of the solid
sample displayed a small peak at 2125 cm−1, confirming the
presence of azide (−N3) in the porous framework. On the
other hand, Figure 6 also showed the FT-IR spectrum of
MOF−Cu2I2(BTTP4) after catalytic reaction. The sharp band
at 1541 cm−1 was assignable to CN bending vibration,
indicative of the presence of amidine in the MOF−
Cu2I2(BTTP4) catalyst. Moreover, Ts−N3 was found in
MOF−Cu2I2(BTTP4) after catalytic reactions. Based on
these results, we proposed that azides entered the framework
channels of MOF−Cu2I2(BTTP4) and underwent reactions
inside the catalyst pores to yield the amidine products.
3.3. In Situ MOF Preparation. Although MOF−
Cu2I2(BTTP4) displayed much bigger size and greater
electronic effects than naked CuI in the three-component
coupling reactions, both catalysts were highly effective for
Figure 4. Recycling experiments.
for the recovered catalyst after the four runs showed no signs of
framework collapse and decomposition. On the other hand, the
XPS spectra displayed the same two intense peaks at 932.8
0.2 and 952.5
0.2 eV assigned to Cu 2p3/2 and Cu
2p1/2 components for MOF−Cu2I2(BTTP4) catalysts before
and after the reaction (Figure S10). These data suggested that
both the valence states of the copper before and after the
reaction were +1.
3.2. Physical Characterizations of MOF−Cu2I2(BTTP4)
after Reactions. We measured CO2 gas adsorption/
desorption isotherms for MOF−Cu2I2(BTTP4) samples,
which were activated under similar conditions before and
after catalytic reactions (Figure 5). At 195 K, the amount of
CO2 uptake at 1 atm reach 25.4 and 8.9 wt % before and after
catalytic reactions, corresponding to 6.4 and 1.8 CO2 molecules
per Cu2I2 unit, respectively. We ascribe the reduction of
adsorption capability of CO2 by MOF−Cu2I2(BTTP4) after
catalysis to the presence of remaining tosylazide (0.2 equiv
excess relative to alkyne) or amidine products that might block
the adsorption sites inside the framework pores because the
integrity of the porous framework and crystallinity of MOF−
Cu2I2(BTTP4) catalysts have been proven by PXRD to be well-
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Figure 6. (a) FT-IR of 1a, (b) samples of MOF−Cu2I2(BTTP4) after
catalytic reaction, (c) as-prepared MOF−Cu2I2(BTTP4), and (d)
samples of MOF−Cu2I2(BTTP4) immersed in solution of Ts−N3.
Figure 7. Ligand-accelerated catalytic performances with variable CuI/
BTTP4 molar ratios.
acceleration effect and improved chemoselectivity of BTTP4
was limited in a shorter reaction time (e.g., 30 min). The
conversions with a longer reaction time in the presence of
naked CuI or the mixtures of CuI/BTTP4 are shown in Figure
S3. After 2 h, the CuI-catalyzed reaction accomplished with the
same completion values that are approximately 80% of those for
CuI/BTTP4 mixtures.
As discussed above, we observed that the catalytic
effectiveness relied closely on the molar ratios of CuI/
BTTP4, which aroused our interests to analyze the CuI/
BTTP4 mixtures and disclose the structures of the in situ
formed crystallites at different molar ratios. We measured the
PXRD patterns of the solids isolated from suspension of CuI
and BTTP4 mixtures with different molar ratios. As depicted in
Figure 8, the PXRD patterns of orange solids obtained from
aromatic alkynes. On the other hand, it has been well-
established by Finn and Fokin that nitrogen-containing ligands
such as triazoles, benzimidazoles, and pyridines can display
dramatic enhancement in reactivity and selectivity in CuI-
catalyzed reactions. To test the effects of the pyridine-based
ligand BTTP4 on CuI catalysis of such three-component
coupling, we chose the reaction among Ts−N3, an aromatic
alkyne of PhCCH, and (i-Pr)2NH as a model reaction. In the
typical procedure for CuI-catalyzed reactions, 10 mol % of CuI
was employed, and the reactions were performed under a N2
atmosphere.30 To challenge the BTTP4 ligand, a limited
amount of CuI (2.4 mol %) was used with no effort to exclude
oxygen beyond capping the reaction vial. CuI and BTTP4 were
separately dissolved in the corresponding highly soluble
solvents of CH3CN and CHCl3, respectively, and thus, different
molar ratios (e.g., 3:1, 2:1, 1:1, and 1:2) of CuI/BTTP4
mixtures have been prepared. It was found that regardless of the
varied CuI/BTTP4 ratios, a large amount of orange-yellow
crystallites formed rapidly when a CH3CN solution of CuI was
mixed with a CHCl3 solution of BTTP4. After the process of
mixing, to the obtained suspension were subsequently added
Ts−N3, PhCCH, and (i-Pr)2NH, and violent bubbling
appeared after this addition, indicating the start of the reaction.
Until the completion of the reaction, negligible loss of the
orange-yellow crystallites was detected.
As shown in Figure 7, the CuI-catalyzed three-component
coupling reaction among Ts−N3, PhCCH, and (i-Pr)2NH leads
to the formation of N-sulfonylamidine (1a) as the major
product and tosyltriazole (1b) as the minor one. In the absence
of the BTTP4 ligand, the reaction gave less than 40% of 1a in
30 min at room temperature, whereas the addition of 1/3 or 1/
2 of BTTP4 ligand with respect to CuI yielded around 80% of
1a in the same time and at the same temperature. However, at a
CuI/BTTP4 molar ratio of 1:2, the reaction obviously became
inhibited, reducing the completion of the reaction down to less
than 20%. On the other hand, existence of the BTTP4 ligand
can largely enhance the chemoselectivity of this three-
component coupling reaction. In the absence of BTTP4, the
1a/1b ratio was 3:1, whereas in the presence of 1/3, 1/2, 1, and
2 equiv of BTTP4, the 1a/1b ratios were 27:1, 40:1, 21:1, and
8:1, respectively. These results suggest that BTTP4 ligand is
competent in protecting CuI under the reaction conditions and
promoting CuI-catalyzed transformation of the three-compo-
nent coupling with a noticeable ligand-acceleration effect and
chemoselectivity. Nevertheless, it should be noted that the
Figure 8. Comparison of the PXRD patterns of as-prepared MOF−
Cu2I2(BTTP4) with those of the crystallites isolated from suspension
of CuI and BTTP4 mixtures with different molar ratios. Inset shows
the photos of in situ mixtures.
1:2, 1:1, and 2:1 CuI/BTTP4 mixtures all closely match those
of as-synthesized MOF−Cu2I2(BTTP4) but with different
degrees of crystallinity. The results indicated that a 2:1 CuI/
BTTP4 mixture gave the highest relative crystallinity, and the
degrees of crystallinity of Cu2I2(BTTP4) were in sequence of c
(2:1) > b (1:1) > a (1:2). These observations help us believe
that the effective catalyst in the mixture was actually the
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framework of MOF−Cu2I2(BTTP4), regardless of the different
CuI/BTTP4 ratios, due to the following reasons: (i) MOF−
Cu2I2(BTTP4) was the unique product in these solutions in
spite of varied CuI/BTTP4 ratios (e.g., 1:2, 1:1, 2:1, and 3:1),
whereas the filtrate did not display noticeable catalytic activity
with the conversion less than 2.8% after 2 h (Figure S4); (ii)
excess CuI in solution (in the case of CuI/BTTP4 ratio of 3:1)
contributed little to transformation in comparison with the
MOF−Cu2I2(BTTP4), which was quantitatively formed in the
case of the 2:1 CuI/BTTP4 ratio; and (iii) an excess amount of
BTTP4 (in cases of CuI/BTTP4 ratios of 1:1 and 1:2) showed
an inhibiting effect on reactions probably because they not only
prevented the substrates from approximating the active metal
centers of MOF−Cu2I2(BTTP4), but the 1:1 and 1:2 CuI/
BTTP4 mixtures also gave a lower relative crystallinity
compared to 2:1 CuI/BTTP4 mixtures.
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4. CONCLUSIONS
In summary, the permanently porous metal−organic frame-
work, MOF−Cu2I2(BTTP4), which is assembled from a rigid
tritopic ligand benzene-1,3,5-triyl triisonicotinate (BTTP4) and
CuI, is proven to be able to catalyze the three-component
coupling of sulfonyl azides, alkynes, and amines in an efficiently
heterogeneous way, leading to formation of important organic
compounds of amidines with good yields. The unique structural
features of MOF−Cu2I2(BTTP4), including incorporation of
redox-active and coordinatively unsaturated CuI sites into pore
surface, suitable framework channel size surrounded by rigid
nitrogen-containing tripodal ligands, and porosity robustness
against evacuation of solvent molecules, endow the MOF−
Cu2I2(BTTP4) catalyst with versatile character such as
unprecedented heterogeneous ligand-accelerated effect, size-
effect, and recyclability for reuse of the catalyst. The catalytic
performance has been studied by various physical and chemical
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