DOI: 10.1002/cctc.201600774
Full Papers
Palladium(II)@Zirconium-Based Mixed-Linker Metal–
Organic Frameworks as Highly Efficient and Recyclable
Catalysts for Suzuki and Heck Cross-Coupling Reactions
Rong Sun, Bing Liu, Bo-Geng Li, and Suyun Jie*[a]
Two series of amine-functionalized Zr-based mixed-linker
metal–organic frameworks (MOFs; UiO-66-Mix and UiO-67-Mix)
have been synthesized with different ratios of 1,4-benzenedi-
carboxylate/2-amino-1,4-benzenedicarboxylate and 4,4’-biphe-
nyldicarboxylic acid/2-amino-biphenyl-4,4’-dicarboxylic acid in-
corporated into their structures. The pendant amino groups
were postmodified by the condensation reaction with pyri-
dine-2-carboxaldehyde, and Pd metal centers were anchored
onto the MOFs by coordination to the pyridylimine moieties.
The two series of heterogeneous Pd catalysts (UiO-66-Mix-PI-
Pd and UiO-67-Mix-PI-Pd) were utilized for the Suzuki and
Heck cross-coupling reactions in ethanol/water under mild re-
action conditions and they showed a remarkably high catalytic
activity. The porosity of the MOFs and the density of the metal
binding sites of the Pd catalysts had great influence on the
Suzuki and Heck cross-coupling reactions. The best results
were achieved with a very low Pd loading (0.054 mol%), and
the use of UiO-67-3-PI-Pd catalyst led to the complete conver-
sion of reaction substrates. Moreover, the catalysts were readily
recovered and recycled in at least 10 cycles without significant
leaching or loss of catalytic activity. The catalysts were general-
ly applicable for different reaction substrates with various sub-
stituents in both Suzuki and Heck reactions.
Introduction
Palladium-catalyzed cross-coupling reactions, one of the most
powerful tools for the formation of CÀC bonds, such as Suzuki
and Heck reactions, are of great interest from both academic
and industrial points of view.[1] The significance of Pd catalysis
was emphasized by the award of the 2010 Nobel Prize to
Heck, Suzuki, and Negishi for their pioneering work in this
field.[2] As a result of the limited availability and high price of
Pd, environmental concerns and economic considerations
make it essential to develop Pd catalysts with the full utiliza-
tion of each Pd active site with excellent recyclability and neg-
ligible metal leaching to reduce the cost of the catalysts and
pollution to the environment.[3]
erogeneous catalysts because they contain inherent catalytical-
ly active sites within the frameworks or as supporting materials
for various catalysts.[6] There have been many reports about
MOFs as heterogeneous catalysts or catalyst supports applied
in a variety of organic transformations, which include cross-
coupling, oxidation, and multicomponent reactions.[7] Postsyn-
thetic modification (PSM) is an attractive and powerful tool for
the introduction of functional groups into MOFs by incorporat-
ing organic linkers or unsaturated metal sites.[8] For this pur-
pose, the basicity and reactivity of pendant amino groups has
resulted in the exploitation of amino-functionalized MOFs for
this purpose.[9] Heterogeneous catalysts prepared by the intro-
duction of metal centers onto amino-functionalized MOFs have
been applied in coupling reactions.[10] The dilution of function-
alization through the use of a mixed-linker approach is an ef-
fective method to tune activity by varying the composition of
mixed-linker MOFs.[11]
As a result of their high surface area, porosity, and chemical
tenability, metal–organic frameworks (MOFs) have emerged as
an important class of functional porous materials with distinct
structural properties that are constructed by metal ions or clus-
ters and bridging organic ligands.[4] The advantages of MOFs
have led to the intensive examination of their properties for
potential applications in several areas, which include gas stor-
age, sensors, thin films, optics, drug carriers, and catalysis.[5]
Heterogeneous catalysis is superior to homogeneous catalysis
because it leads to easier separation, reusability, minimized
waste, and cleaner products. MOFs have been pursued as het-
In our ongoing investigations into the application of mixed-
linker MOFs for Suzuki and Heck cross-coupling reactions, Zr-
based MOFs have drawn our attention because of their excel-
lent thermal, aqueous, and acid stability.[11a,12] UiO-66- and UiO-
67-type MOFs were chosen for the incorporation of Pd active
centers because of their high specific surface areas and unpre-
cedented stability.[13] Herein, we report the quantitative PSM of
two series of mixed-linker MOFs (UiO-66-Mix and UiO-67-Mix)
by the reaction with pyridine-2-carboxaldehyde and the further
coordination of Pd to the pyridylimine moieties to afford heter-
ogeneous Pd catalysts (UiO-66-Mix-PI-Pd and UiO-67-Mix-PI-
Pd). The Suzuki and Heck cross-coupling reactions catalyzed by
these heterogeneous Pd catalysts were investigated in detail,
[a] R. Sun, Dr. B. Liu, Prof. B.-G. Li, Prof. S. Jie
State Key Laboratory of Chemical Engineering
College of Chemical and Biological Engineering
Zhejiang University Hangzhou 310027 (P.R. China)
Supporting information for this article can be found under http://
ChemCatChem 2016, 8, 1 – 12
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