Pd/MOF-199: As an efficient heterogeneous catalyst for the Suzukie Miyaura cross-coupling reaction

Article abstract of DOI:10.1002/jccs.201800428

Successful deposition of Pd nanoparticles is described using MOF-199 as a support. Various characterization techniques including FTIR, XRD, SEM, BET-BJH, TG-DTA, and NH₃-TPD were used to verify the efficiency of catalysts. Pd/MOF-199 is utilized as a catalyst for Suzukie Miyaura reactions with reasonable to excellent reaction yields under reflux conditions in H₂O: ethanol solvent.

Full text of DOI:10.1002/jccs.201800428

Received: 9 November 2018
DOI: 10.1002/jccs.201800428
Revised: 24 January 2019
Accepted: 1 February 2019
A R T I C L E
Pd/MOF-199: As an efficient heterogeneous catalyst for the
Suzukie Miyaura cross-coupling reaction
Mehran Sanaei | Razieh Fazaeli | Hamid Aliyan
Department of Chemistry, Shahreza Branch,
Successful deposition of Pd nanoparticles is described using MOF-199 as a sup-
Islamic Azad University, Shahreza, Iran
port. Various characterization techniques including FTIR, XRD, SEM, BET-BJH,
Correspondence
Razieh Fazaeli, Department of Chemistry,
TG-DTA, and NH3-TPD were used to verify the efficiency of catalysts. Pd/MOF-
199 is utilized as a catalyst for Suzukie Miyaura reactions with reasonable to excel-
lent reaction yields under reflux conditions in H2O: ethanol solvent.
Shahreza Branch, Islamic Azad University,
Shahreza 86145-311, Iran.
Email: raziehfazaeli@yahoo.com
Funding information
KEYWORDS
Islamic Azad University
heterogeneous catalyst, Suzukie Miyaura cross-coupling reaction, MOF-199,
palladium
diverse chemical compositions, high surface areas, tunable
pore size, and internal microenvironments, MOFs allow the
1
| INTRODUCTION
Nowadays, one of the most significant challenges heteroge-
neous catalysis faces is translating material design into an
actual catalyst through controlled synthesis. Despite many
advances, conventional synthetic techniques usually fall
short in delivering materials with the desired properties. The
preparation of metal nanoparticle-based catalysts, where it is
not always possible to achieve desired metal loadings and
controlled particle size, is an outstanding example of this
challenge. Recent advances in this field include (a) the use
of colloidal,[1] reverse micelle,[2] and dendrimer chemistry[3]
in the production of metal and metal oxide nanoparticles
with well-defined sizes, shapes, and compositions, (b) the
introduction of sol–gel[4] and atomic layer deposition[5]
chemistry for the production and modification of high-sur-
face-area supports and active phases, (c) the design of dumb-
bells, core/shell, and other complex nanostructures leading
to multiple functionality in catalysis,[6] and (d) the mixed
molecular-nanostructure approach that can be used to
develop more demanding catalytic sites, by derivatization of
the surface of solids or tethering or immobilizing other
chemical functionalities.[7,8]
implementation of catalytic properties by embedding metal
NPs.[15] This strategy is widely accepted and becomes a signif-
icant tool for expanding MOF-supported application in cataly-
sis. On the other hand, MOFs themselves are inherent
heterogeneous catalysts due to their inorganic–organic hybrid
composition and polymeric nature. Therefore, the incorpora-
tion of MOF-supports with the metal NPs would lead to
enhanced or even novel catalytic properties compared to their
pristine counterparts.[16] MOF-199, a 3D porous MOF mate-
rial, has shown significant capacities for catalyst engineer-
ing.[17] Because of the correlation between their size and the
accessible dimensions of the windows of each cage, the intro-
duction of molecular inorganic species, nanoparticles, and
drugs within cages of porous structure could be achieved.[18,19]
Herein, we report a rapid, simple, and high yielding synthe-
sis of Pd/MOF-199 as a catalyst for the Suzuki reaction. MOF-
199 was chosen because it represents open metal sites.[20]
2
| RESULTS AND DISCUSSION
2.1 | Characterization of Pd/APN-MOF-199
As a unique class of porous materials, metal–organic
frameworks (MOFs) are promising platforms for creating a
composite heterogeneous catalyst system.[9–14] Owing to their
The IR spectra of MOF-199 and Pd/MOF-199 (Figure 1)
exhibited strong stretching vibrations of carboxylate anions
© 2019 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
J Chin Chem Soc. 2019;1–6.
http://www.jccs.wiley-vch.de
1

2
SANAEI ET AL.
(a)
(c)
Wavenumber (cm-1
)
10
10
10
20
20
20
30
30
30
40
40
40
50
50
50
60
60
60
70
70
70
(b)
(b)
1.0
0.8
0.6
0.4
0.2
0.0
(a)
4000
3000
2000
1000
Wavenumber [cm-1]
FIGURE 1 FTIR spectra of (a) MOF-199 and (b) Pd/MOF-199
at 1639, 1593, and 1,448 cm−1, which could be assigned to
the characteristic vibrations of C=O. The peaks at about
1,444 cm−1 were ascribed to the C-C stretching on the ben-
zene ring.[18] The appearance of
a broad band at
3500–2700 cm−1 indicated the presence of water and –OH
groups in the structure of the material.
2θ (ο)
The XRD patterns of MOF-199 and Pd/MOF-199 are
indicated in Figure 2. The XRD pattern of the Pd/MOF-199
is similar to that of MOF-199[19] in d-spacing and line shape,
demonstrating that chemical functionalization can be
achieved without a loss of structural integrity but with some
slight variations in the Bragg intensities. Furthermore, there
is no apparent loss of crystallinity in X-ray diffraction pat-
terns and no supplementary Bragg peaks appear after the
metal complex formation, but the intensities of the peaks of
MOF-199 change confirming the introduction of the com-
plex into the pores. For both 3% and 7% Pd/MOF-199
(Figure 2b and c, respectively), The absence of a Pd diffrac-
tion pattern relates to the low Pd contents in the materials.
An irregular arrangement of mesopores and macropores
is shown in SEM images of Pd/MOF-199 (Figure 3). This
bimodal porous structure contains <50 nm mesopores and
a broad distribution of macropores (50–100 nm). Figure 3g
FIGURE 2 XRD patterns of (a) MOF-199, (b) 3% Pd/MOF-199, and
(c) 7% Pd/MOF-199
shows the SEM–EDX spectrum of Pd/MOF-199 samples,
which show the presence of Pd, Zn, N, C, and oxygen as
elements of Pd/MOF-199 structures. The peaks of Pd are
distinct in Figure 4g at 2.8 and 3.6 keV. This result con-
firms the existence of Pd atoms in the AP-MOF matrix.
According to the EDX spectrum, it is concluded that a suf-
ficient amount of Pd was loaded into AP-MOF-199.
The N2 adsorption–desorption isotherms of Pd/MOF-199
catalysts are shown in Figure 4. In accordance with the
IUPAC nomenclature, both samples show typical IV type
isotherms and H1 type hysteresis looped at high relative
pressures.[21]

SANAEI ET AL.
3
(a)
(b)
(a)
45
40
35
30
25
20
15
10
5
Ads
Des
(c)
(d)
0.0
0.2
0.4
0.6
0.8
1.0
p/po
(b)
0.004
0.003
0.002
0.001
Ads
0.004
0.003
0.002
0.001
0.000
(e)
(f)
2
4
6
8
10
12
14
r
p
/nm
0
20
40
60
80
100
rp/nm
FIGURE 4 (a) N2-adsorption–desorption isotherms and (b) pore size
distributions calculated using the BJH method of Pd/MOF-199
organic framework, as observed in the DTA curve (exother-
mic peak at 350ꢀC).
(g)
Cu
The acidic properties of Pd/MOF-199 were measured by
a temperature program desorption (TPD) technique using
NH3 (NH3-TPD) as a probe gas (Figure 6). In principle, the
higher the desorption temperature, the stronger the acidity.
The spectra in Figure 6 indicated two different sorption sites
in Pd/MOF-199: a strong site (596ꢀC) and three weak sites
(395, 314, and 204ꢀC). It is notable that TPD using NH3 as
the probe often overestimates the quantity of acid sites
because of the small molecular size of NH3 (2.9 Å) allowing
it to penetrate in almost all the accessible pores of the porous
solids and possible additional NH3 adsorption due to NH3–
NH3 interactions.[22,23]
500
C
400
300
O
200
Cu
Pd
Pd
100
N
Cu
keV
0
0
5
10
FIGURE 3 (a–f) SEM images and (g) EDS patterns of Pd/MOF-199
2.2 | Catalytic activity of Pd/MOF-199 in the
Hosomi–Sakurai reaction
The thermogravimetric (TG), derivative thermogravi-
metric (DTG), and differential thermal analyses (DTA) of
Pd/MOF-199 are shown in Figure 5. The TG curve shows
about 4% weight loss, associated with the volatilization and
decomposition of organic species such as ethanol and
dichloromethane. The other significant weight loss in the
150–540ꢀC range is attributed to decomposition of the metal
The catalytic activity of Pd/MOF-199 was investigated
using the Suzuki coupling reaction of various aryl bromides
with phenylboronic acid. The reactions were carried out
using K2CO3 as a base, ethanol/H2O (2:1) as a solvent in
the presence of the Pd/MOF-199 (0.01 g) catalysts under

4
SANAEI ET AL.
100
80
60
40
20
0
100
80
60
40
20
3.97%
57.43 %
0
200
400
600
800
1
2
3
4
5
Temerature (oC)
Run
FIGURE 7 Recycling efficiency of the Pd/MOF-199 catalyst in the Suzuki
FIGURE 5 TG-DTA analysis of Pd/MOF-199
cross-coupling reaction
0.16
0.14
0.12
0.10
0.08
596
withdrawing nature of the substitution on the reactants. In
presence of p-NO2 as an electron withdrawing group the
yield increased, whiles in presence of p-OCH3 as an elec-
tron-releasing group the yield decreased (Table 1,
entries 4,6).
After the reaction, catalysts were collected and set aside
for recycling experiments. In addition, the filtrate was
checked for evidence of palladium leaching. Fortunately,
ICP-MS showed no significant loss of palladium from either
catalyst. The products were obtained of the same purity as in
the first to fifth runs, but the yields were gradually decreased
in runs carried out using the recycled catalyst (Figure 7).
To show the merit of the present work in comparison
with recently reported protocols, we compared the results
with respect to the amounts of the catalysts used, reaction
temperature, reaction times, and yields of the products
(Table 2). Comparison of Pd/MOF-199 with these catalysts
for the Suzukie Miyaura cross-coupling shows that our pre-
sent Pd/MOF-199 catalyst system exhibited a higher conver-
sion and yield at room temperature with a minimum amount
of Pd loading under milder conditions.
0.06
395
314
0.04
0.02
0.00
204
200
400
600
800
Temperature (°C)
FIGURE 6 NH3-TPD of Pd/MOF-199
TABLE 1 Suzukie Miyaura reactions with different substituents catalyzed
by Pd/MOF-199 under optimized reaction conditions
Pd/MOF-199
R1
(OH)2B
+
Br
R1
K2CO3
R2
R2
Entry
R1
R2
Time (hr)
5.0
Yielda,b
1
2
3
4
5
6
7
8
H
H
92
90
87
85
98
98
95
95
3
| EXPERIMENTAL
H
4-CH3
3-CH3
H
5.5
H
6.0
Chemicals used were all of reagent grade. Reaction courses
and product mixtures were monitored by thin layer chroma-
tography and GC. A Perkin Elmer Spectrum 65 spectropho-
tometer was used to obtain infrared spectra
(400–4,000 cm−1) from KBr pellets. Cu Kα (1.54056 Å)
radiation with automatic control was used to obtain powder
XRD diffraction patterns on a XRD, Bruker D8 ADVANCE
and PW1830 instrument. Adsorption/desorption of nitrogen
at liquid nitrogen temperature was used to determine BET
specific surface areas and pore volumes of the catalysts with
a Micromeritics Bel sorp mini II instrument. The samples
were outgassed at 623 K for 12 hr under a vacuum of 10−4
OCH3
COCH3
NO2
COCH3
COCH3
7.5
H
4.5
H
3.5
4-OCH3
4-NO2
4.5
4.0
a
Isolated yield.
b
Reaction conditions: Bromoarene (1 mmol), arylboronic acid (1.5 mmol),
K2CO3 (0.75 mmol), H2O:EtOH (1:2), (6 mL) and Pd/MOF-199 (0.3 mol
%), 60ꢀC.
reflux conditions for 30 min. The catalytic results are listed
in Table 1. As a shown in Table 1, the yield of the Suzuki
cross-coupling reaction depends on the electron donating or

SANAEI ET AL.
5
TABLE 2 Comparison of activity for different catalytic systems in the Suzukie Miyaura cross-coupling
Entry
Catalyst
Reaction conditions
K2CO3, H2O, 100ꢀC, N2
K2CO3, CTAB, H2O, 100ꢀC, 24 hr
K2CO3,H2O, (60–90) oC, (2–20) hr
Na2CO3, DMF:H2O (1:1), 1 hr
Na2CO3,H2O:EtOH (1:2), 4–5.5 hr
Yield (%)
48–98
61
Ref.
[24]
1
2
3
4
5
PANI-Pd (2 mol%)
[25]
[26]
[27]
10% Pd/C (1 mol%)
Pd@PMO-IL (0.1–1) mol%
Pd(0)-NaY zeolite (0.025 mmol)
Pd/MOF-199 (0.01 g)
18–97
26–100
87–95
Present work
Pa prior to the adsorption measurements. Catalyst pore sizes
were obtained from the peak positions of the distribution
curves determined by the adsorption branches of the iso-
therms. A Joel JEM 2010 scan-transmission electron micro-
scope was used to obtain transmission electron micrographs
(TEM). To perform the TEM measurement, the sample was
suspended in ethanol and supported on a carbon-coated cop-
per grid. A Shimadzu, MPC-2200 UV–Vis spectrophotometer
operating within the range of 190–900 nm at a resolution of
2.0 nm was used to obtain DRUV spectra. A scan-
transmission electron microscope was used to obtain trans-
mission electron micrographs (TEM). ICP/OES was carried
out using a Varian Vista-MPX CCD Simultaneous ICP/OED
device, the used Pd-standard was 10,000 ppm Pd
in 5% HNO3.
MOF-199
+
+ Pd(phCN)2Cl2
Toluene
CH2Cl2
AP-MOF-199
4-Aminopyridine
Pd/MOF-199
FIGURE 8 Synthesis of Pd/MOF-199
3.3 | Preparation of Pd/AP-MOF-199 (Pd/MOF-199,
hereafter)
An amount of 20 mg of PdCl2(PhCN)2 was poured in a
25 mL round-bottom flask that contained 5 mL of dichloro-
methane. The solution thus obtained was added to a suspen-
sion of 200 mg of AP-MOF-199 in CH2Cl2 (10 mL). The
mixture was then heated at reflux for 4 hr, cooled to ambient
temperature, filtered, and washed with CH2Cl2 to remove
any unreacted Pd complex and finally dried at 353 K in
vacuo (Figure 8).
3.1 | Synthesis of MOF-199
Benzenetricarboxylic acid (500 mg, 2.38 mmol) was mixed
in 12 mL of a 1:1:1 mixture of DMF/EtOH/H2O. Cu(OAc)2.
H2O (860 mg, 4.31 mmol) was mixed with 12 mL of the
same solvent and the mixtures were combined with stirring.
Triethylamine (0.5 mL) was added to the reaction mixture,
which was stirred for 23 hr. The product was collected by
filtration and washed with 2 × 25 mL of DMF and a sample
was collected for PXRD analysis, which showed pure MOF-
199 by comparison with the pattern simulated from SXRD
data (Figure 2d).[16] The product was collected by filtration,
washed with 2 × 25 mL of DMF, then immersed in 50 mL
of CH2Cl2 (HPLC grade) overnight. The next day, the sol-
vent was exchanged for fresh solvent three times (50 mL
portions) and left overnight. It was then evacuated to ≤5
mTorr overnight, during which time the deep blue solid
became blue-violet. The product was brought into the glove
box under vacuum and weighed (316 mg, 44%).
3.4 | Catalyst usage for Suzukie Miyaura coupling
reaction
Typically, aryl halide (0.5 mmol), phenylboronic acid
(0.6 mmol), K2CO3 (1.5 mmol), EtOH/H2O (4 mL, 1:1,
v/v), and Pd/MOF-199 (20 mg, 0.01 mol%) were added to a
round-bottom flask. The reaction mixture was stirred at room
temperature for an appropriate time in air (TLC monitoring).
After completion, the catalyst was separated by centrifuga-
tion and the reaction mixture was diluted with 10 mL of
H2O and extracted with ethyl acetate (3 × 10 mL). Then, the
organic layer was combined, dried over anhydrous MgSO4,
and filtered, and the solvent was removed under reduced
pressure. For the purification of impure products, chroma-
tography on silica gel was performed. All of the biphenyls
1
were characterized by melting point, mass, and H NMR
spectroscopy.
3.2 | Preparation of AP-MOF-199
4
| CONCLUSION
An amount of 0.5 g of MOF-199 was dehydrated at 393 K
under vacuum to obtain a dark-brown solid. A solution of
4-aminopyridine (50 mg, 0.53 mmol) was added to a sus-
pension in toluene (15 mL) of the dehydrated material, the
mixture was heated at 90ꢀC for 12 hr, filtered, washed with
CH2Cl2, and dried at 373 K for 3 hr.
In summary, we have successfully designed and synthesized
a new modified Pd@MOF-199 with 4-aminopyridine and
presented its activity as a heterogeneous palladium catalyst
in Suzukie Miyaura cross-coupling reaction. This catalyst
was capable of promoting the reaction of aryl iodide, bro-
mides, and even aryl with excellent yields under a green and

6
SANAEI ET AL.
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and recycled for five successive runs without substantial
diminution in yields. Therefore, this approach opens up a
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ACKNOWLEDGMENTS
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We gratefully thank Shahreza Branch, Islamic Azad Univer-
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ORCID
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How to cite this article: Sanaei M, Fazaeli R,
Aliyan H. Pd/MOF-199: As an efficient heteroge-
neous catalyst for the Suzukie Miyaura cross-coupling
reaction. J Chin Chem Soc. 2019;1–6. https://doi.org/
10.1002/jccs.201800428
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