The effect of framework functionality on the catalytic activation of supported Pd nanoparticles in the Mizoroki–Heck coupling reaction

Article abstract of DOI:10.1016/j.crci.2016.06.002

Palladium nanoparticles (Pd-NPs) were supported on functional and nonfunctional Co-coordination polymers (Pd/CoBDCNH₂ and Pd/CoBDC). Advanced analytical techniques revealed that Pd-NPs are supported on the external surface of the polymer framework and the functionalized framework possesses effective influence to prevent Pd-NP aggregation. Supported Pd-NPs were effectively applied as heterogeneous recyclable catalysts in the Mizoroki–Heck C–C cross coupling reactions of iodobenzene and either aromatic or aliphatic terminal alkenes. Catalytic results exhibited that highly dispersed Pd-NPs with low loading (1%) on the functional polymer (Pd/CoBDCNH₂) are more effective than aggregated Pd-NPs with high loading (9%) on the nonfunctional polymer (Pd/CoBDC). Both catalysts can simultaneously provide high activity and selectivity to E-coupled products, high efficiency in low amounts, easy separation of heterogeneous catalyst and appropriate performance in the recycling reaction without addition of a reducing agent.

Full text of DOI:10.1016/j.crci.2016.06.002

C. R. Chimie xxx (2016) 1e9
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Full paper/Memoire
The effect of framework functionality on the catalytic
activation of supported Pd nanoparticles in the
MizorokieHeck coupling reaction
,
Fatemeh Ashouri a *, Maryam Zare b, Mojtaba Bagherzadeh c
a Department of Applied Chemistry, Faculty of Pharmaceutical Chemistry, Pharmaceutical Sciences Branch, Islamic Azad University,
Tehran, Iran
b Department of Basic Sciences, Golpaygan University of Technology, P.O.Box 87717-65651, Golpaygan, Iran
c Department of Chemistry, Sharif University of Technology, P.O. Box 11155-3516, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Palladium nanoparticles (Pd-NPs) were supported on functional and nonfunctional Co-
coordination polymers (Pd/CoBDCNH2 and Pd/CoBDC). Advanced analytical techniques
revealed that Pd-NPs are supported on the external surface of the polymer framework and
the functionalized framework possesses effective influence to prevent Pd-NP aggregation.
Supported Pd-NPs were effectively applied as heterogeneous recyclable catalysts in the
MizorokieHeck CeC cross coupling reactions of iodobenzene and either aromatic or
aliphatic terminal alkenes. Catalytic results exhibited that highly dispersed Pd-NPs with
low loading (1%) on the functional polymer (Pd/CoBDCNH2) are more effective than
aggregated Pd-NPs with high loading (9%) on the nonfunctional polymer (Pd/CoBDC). Both
catalysts can simultaneously provide high activity and selectivity to E-coupled products,
high efficiency in low amounts, easy separation of heterogeneous catalyst and appropriate
performance in the recycling reaction without addition of a reducing agent.
Received 8 January 2016
Accepted 6 June 2016
Available online xxxx
Keywords:
Palladium nanoparticles
Heterogeneous catalyst
MizorokieHeck coupling reaction
Nonfunctional coordination polymer
Functionalized framework
© 2016 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
thermal and chemical stabilities, and good dispersion of the
active catalytic site [7e9].
There has recently been considerable interest in
research on the fabrication of metal nanoparticles with
high stability and controllable size distribution. This is
largely due to their potential application in many fields,
especially in catalysis [1e3]. Among catalytically active
nanoparticles, palladium nanoparticles (Pd-NPs) have
extensively been utilized for the formation of CeC bonds
[4e6] that play significant roles in modern synthetic
chemistry. The Pd-NPs exhibit suitable catalytic activity.
Moreover, heterogeneous metal nanocatalysts provide
considerable advantages such as easy isolation of products,
efficient recovery and recyclability of catalysts, good
A number of solid materials as supports have broadly
been investigated for the immobilization of palladium such
as clay [10], carbon nanofibers [11], carbon nanotubes [12],
graphene [13], ionic liquids [14,15], mesoporous silica [16],
zeolites [17], SBA-15 [18], metal oxides [19,20] and poly-
mers [21]. Among these solid supports, metaleorganic
frameworks (MOFs) or porous coordination polymers can
be considered as a suitable solid material for the stabili-
zation of ligand-free metal nanoparticles [22,23]. On the
other hand, finding a suitable support to immobilize Pd-
NPs without agglomeration is still a tempting challenge in
the field of heterogeneous catalysis.
Here, we report the comparative study on the functional
effect of polymers on the dispersion and catalytic activity of
supported Pd-NPs. We used functional and nonfunctional
* Corresponding author.
E-mail address: f.ashouri@iaups.ac.ir (F. Ashouri).
http://dx.doi.org/10.1016/j.crci.2016.06.002
1631-0748/© 2016 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Please cite this article in press as: F. Ashouri, et al., The effect of framework functionality on the catalytic activation of supported
Pd nanoparticles in the MizorokieHeck coupling reaction, Comptes Rendus Chimie (2016), http://dx.doi.org/10.1016/
j.crci.2016.06.002

2
F. Ashouri et al. / C. R. Chimie xxx (2016) 1e9
Co-coordination polymers, Pd/CoBDCNH2 and Pd/CoBDC,
respectively, as a support for Pd-NPs where CoBDCNH2
[Co3(BDCNH2)3(DMF)2(H2O)2]n, CoBDC [Co3(BDC)3
(DMF)2(H2O)2]n, H2BDCNH2 ¼ 2-amino-1,4-benzenedicar
boxylic acid and H2BDC ¼ 1,4-benzendicarboxylic acid.
Catalytic activity of these supported Pd-NPs was examined
in the MizorokieHeck coupling reactions of iodobenzene
with terminal alkenes.
of DMF in a small sample vessel. The solution was heated
for 24 h at 90 ꢀC. A light cream powder of [Co3(BDC
NH2)3(DMF)2(H2O)2]n (named CoBDCNH2, 85% yield based
on H2BDCNH2) was obtained as an amino-functionalized
polymer. The crystals were washed with DMF (3 mL, 2
¼
¼
times) and dried at 80 ꢀC. Anal. Calcd: for Co3C30H33N5O16
:
C, 40.19; H, 3.71; N, 7.81. Found: C, 40.72; H, 3.70; N, 7.75.
FT-IR (KBr 4000e400 cmꢁ1): 3491 (br), 2931 (w), 1663 (s),
1619 (s), 1559 (s), 1418 (s), 1254 (w), 1115 (m), 855 (m), 813
(m), 760 (s), 693 (s), 655 (m), 468 (m).
2. Experimental
2.1. Materials and instruments
2.4. Synthesis of supported palladium nanoparticles on the
CoBDC polymer framework
All reagents for synthesis and analysis were obtained
commercially and of analytical grade and used without
further purification. The elemental analysis (CHN) of com-
pound was performed using a Carlo ERBA Model EA 1108
analyzer. Fourier transform infrared (FT-IR) spectroscopy
was carried out by utilizing a Unicam Matson 1000 FT-IR
spectrophotometer using KBr disks at room temperature.
Thermogravimetric analysis (TGA) was performed on a
Perkin Elmer TGA7 analyzer in a N2 atmosphere with a
heating rate of 5 ꢀC minꢁ1. Powder X-ray diffraction (XRD)
patterns were recorded by using a Rigaku D-max C III and
The prepared CoBDC polymer (0.15 g) was added to an
orange solution of PdCl2 (0.04 g, 0.2 mmol) and NaCl
(0.58 g, 1.0 mmol) in DMF (10 mL) under vigorous stirring.
Upon adding hydrazine hydrate (4 mL, excess), the mixture
immediately turned gray. After stirring for 15 min, the solid
was isolated by centrifugation, washed with DMF and dried
in an oven at 90 ꢀC. Supported Pd nanoparticles on the Co-
coordination polymer (Pd/CoBDC) was obtained as a gray
powder. The Pd contents (9 wt %) in the samples were
determined by ICP-MS. FT-IR (KBr 4000e400 cmꢁ1): 3475
(br), 3332 (br), 2935 (w), 1659 (w), 1560 (s), 1555 (m), 1419
(s), 1358 (m), 1142 (m), 855(m), 828 (w), 807 (w), 732 (s),
695 (s), 529 (w), 480 (w).
X-ray diffractometer using Ni-filtered Cu Ka radiation.
Inductively coupled plasmaemass spectroscopy (ICP-MS)
was performed by using an ICP-MS HP 4500. The
morphology and size of palladium nanoparticles in Pd/
MnBDC were investigated by incorporating scanning elec-
tron microscopy (SEM, S-4160, Hitachi) and high-resolution
transmission electron microscopy (HR-TEM, Philips CM30)
at 300 kV. X-ray photoelectron spectroscopy (XPS) mea-
2.5. Synthesis of supported palladium nanoparticles on the
CoBDCNH2 polymer framework
surements were performed on
a PerkinElmer PHI
5000CESCA system with a base pressure of 10ꢁ9 Torr. The
products of the coupling reaction were determined and
analyzed by using an HP Agilent 6890 gas chromatograph
equipped with an HP-5 capillary column (phenyl-
The supported Pd-NPs on the amino-functionalized Co-
coordination polymer (Pd/CoBDCNH2) was obtained as a
gray powder by the addition of an orange solution of PdCl2
(0.04 g, 0.2 mmol) and NaCl (0.58 g, 1.0 mmol) in DMF
(10 mL) to prepare CoBDCNH2 (0.15 g) in the presence of
hydrazine hydrate (4 mL, excess). After stirring for 15 min,
the solid was isolated by centrifugation, washed with DMF
and dried in an oven at 90 ꢀC. The Pd contents (1 wt %) in
the samples were determined by ICP-MS. FT-IR (KBr
4000e400 cmꢁ1): 3485 (br), 2930 (w), 1659 (s), 1620 (s),
1550 (m),1420(s), 1250 (w), 1102 (m), 850 (m), 810 (m), 765
(s), 690 (s), 650 (m), 460 (m).
methylsiloxane 30 m ꢂ 320
m
m ꢂ 0.25
mm) and a flame-
ionization detector.
2.2. Synthesis of the [Co3(BDC)3(DMF)2(H2O)2]n framework
The [Co3(BDC)3(DMF)2(H2O)2]n coordination polymer
(CoBDC) was synthesized based on our previous study [24]
by adding
a solution of 1,4-benzenedicarboxylic acid
(H2BDC) (166 mg, 1 mmol) in 5 mL of DMF to CoCl2$6H2O
(291 mg, 1 mmol) solution (DMF, 5 mL). The solution was
heated for 48 h at 80 ꢀC. After 2 days, purple crystals of
[Co3(BDC)3(DMF)2(H2O)2]n (85% yield based on H2BDC)
were collected. Anal. Calcd: for Co3C30H24N2O16: C, 42.42;
H, 3.32; N, 3.30. Found: C, 42.63; H, 2.86; N, 3.28. FT-IR (KBr
4000e400 cmꢁ1): 3491 (br), 2931 (w), 1663 (s), 1619 (s),
1559 (s), 1418 (s), 1254 (w), 1115 (m), 855 (m), 813 (m), 760
(s), 693 (s), 655 (m), 468 (m).
2.6. General procedure for Heck coupling reactions catalyzed
by Pd/CoBDC and Pd/CoBDCNH2 catalysts
The heterogeneous CeC coupling reaction was con-
ducted in a two-necked round-bottom flask fitted to a
condenser and magnetic stirrer and placed in
a
temperature-controlled oil bath. Typically, 1.1 mmol of the
substrate was taken in 2 mL of solvent, followed by the
addition of 13 mg Pd/CoBDC (0.11 mol % Pd) or 5 mg Pd/
CoBDCNH2 (0.05 mol % Pd) catalyst, 1 mmol iodobenzene
and 1.5 mmol base. The flask was kept at 90 ꢀC and stirred
at appropriate times. The products from the reaction
mixture were analyzed by gas chromatography and were
identified by comparison to known standards.
2.3. Synthesis of the [Co3(BDCNH2)3(DMF)2(H2O)2]n
framework
A DMF solution (5 mL) of CoCl2$6H2O (291 mg, 1 mmol)
was added to
a
solution of 2-amino-1,4-benzene
dicarboxylic acid (H2BDCNH2) (182 mg, 1 mmol) in 5 mL
Please cite this article in press as: F. Ashouri, et al., The effect of framework functionality on the catalytic activation of supported
Pd nanoparticles in the MizorokieHeck coupling reaction, Comptes Rendus Chimie (2016), http://dx.doi.org/10.1016/
j.crci.2016.06.002

F. Ashouri et al. / C. R. Chimie xxx (2016) 1e9
3
Fig. 1. FT-IR spectrum of the H2BDCNH2 ligand (a) and CoBDCNH2 (b) and CoBDC (c) polymers.
3. Results and discussion
The differences between the functional and nonfunc-
tional polymers are very obvious in the FT-IR spectra of
these polymers (Fig. 1). The finger point area for eNH2
functional group is distinguishable in free ligands (Fig. 1a)
and the Co-amino-functionalized polymer (Fig. 1b). These
peaks appear at 3503 and 3394 cmꢁ1 in free ligands and at
3310 and 3149 cmꢁ1 in the amino-functionalized polymer,
respectively. The existence of these peaks in the polymer
indicates that the functional group remained unchanged
after polymer formation. The slight shifts are due to the
ortho effects of amino and carboxylate groups that happen
after framework formation. The absence of these finger
point peaks in the Co-nonfunctional polymer is the obvious
difference between these two polymers (Fig. 1c).
3.1. Characterization of the polymer framework and
supported Pd nanoparticles
The [Co3(BDC)3(DMF)2(H2O)2]n framework was synthe-
sized and characterized based on our previous reported
work [24]. The CoBDC polymer is made of CoeO6 octahe-
dral linked by H2BDC ligands. The coordination polymer
structure is a 2D-periodic framework formed by two-
dimensional infinite straightforward chains through cova-
lent interactions.
The CoBDCNH2 framework was synthesized in the same
way but the attempt to obtain its suitable single crystal was
unsuccessful. Therefore, the amino-functionalized frame-
work of CoBDCNH2 was characterized based on solid
powder.
Fig. 2 demonstrates the following coordination modes
in H2BDCNH2 linker ligand from carboxylate groups to the
metal centers that help to form a polymer framework.
Co
Co
Co
Co
Co Co
Co
Co
O
HO
O
O
O
O
O
O
O
O
H
H
H
N
N
N
H
H
H
O
HO
O
O
O
O
O
O
O
O
Co
Co
Co
Co
Co
Co
Co
Co
(a)
(b)
(c)
Fig. 2. The inter-hydrogen bond in the H2BDCNH2 linker ligand (a), coordination modes in the nonfunctional polymer (b) [25], and in the amino-functionalized
polymer (c).
Please cite this article in press as: F. Ashouri, et al., The effect of framework functionality on the catalytic activation of supported
Pd nanoparticles in the MizorokieHeck coupling reaction, Comptes Rendus Chimie (2016), http://dx.doi.org/10.1016/
j.crci.2016.06.002

4
F. Ashouri et al. / C. R. Chimie xxx (2016) 1e9
Fig. 3. TGA curves of CoBDC (a), CoBDCNH2 (b), Pd/CoBDC (c) and Pd/CoBDCNH2 (d) coordination polymers.
A thermal study shows that both polymers have similar
CoBDC coordination polymer. As observed in Pd/MIL-
53(Al) [4], this aggregation was predictable due to the
nonfunctionalized polymer framework [4,23]. PdNPs were
well dispersed on the surface of CoBDCNH2 polymers
(Fig. 5c and d). It seems that the functionalized polymer
possesses an effective influence to prevent the aggregation
of particles. Another difference between functionalized
and nonfunctionalized polymers is the morphology. It was
observed from the SEM images that the change in
morphology occurs from nanospheres in the CoBDC
polymer to nanosheets in the CoBDCNH2 polymer due to
functionalized linker ligands (Fig. 6). It is obvious that the
morphology remains unchanged after the loading of
PdNPs.
decomposition profiles (Fig. 3). Final destruction occurred
at 330e350 ꢀC for CoBDC and at 460e490 ꢀC for the Co-
BDCNH2 polymer. It seems that the functionalized polymer
has a higher thermal stability. The first major mass loss
step of 19.56% at 380 ꢀC in Co-BDCNH2 polymer was
attributed to the removal of 2 DMF and 2 water molecules
per formula unit (calcd. 20.04%). Furthermore, upon
further heating, there was no mass loss until the structure
collapsed at 460e480 ꢀC (weight loss 43.56%). These
weight losses are in agreement with [Co3(BDCNH2)3
(DMF)2(H2O)2]n empirical formula. This supposed formula
of the Co-BDCNH2 polymer was further confirmed by
elemental analysis.
The solution impregnation method was used to immo-
bilize Pd-NPs on the functional and nonfunctional Co-
coordination polymers (Pd/CoBDCNH2 and Pd/CoBDC).
The TGA analysis of supported PdNPs on the CoBDC
polymer (Fig. 3c) exhibited the same destruction profile as
CoBDC but with a slow loss of weight. The weight loss
started at 80 ꢀC and continued to 160 ꢀC, then reached
400 ꢀC by a constant slope. Final collapse occurred at
420e470 ꢀC. The weight loss in Pd/CoBDCNH2 polymer
started at 100e300 ꢀC by gentle slope and continued to
340e450 ꢀC by steep slope. The final decomposition of this
polymer occurred at 530 ꢀCe600 ꢀC. It seems that the
presence of active Pd-NPs on polymers is due to the simple
degradation of organic moieties [25].
As shown in the XRD pattern, the presence of PdNPs had
no influence on the structural characteristics of the poly-
mers and there is no significant loss of crystallinity in
framework diffraction patterns after PdNP loading (Fig. 4).
The characteristic peaks of Pd (111) and Pd (200) at
2
q
¼ 40.10 and 46.5ꢀ,respectively, are distinguishable.
The size and local composition of PdNPs were investi-
gated by HR-TEM (Fig. 5). The images obviously show that
the highly aggregated Pd-NPs are attached to the polymer
surface (Fig. 5a,b). EDX spectroscopy confirmed the pres-
ence of aggregated Pd-NPs on the external surface of the
Fig. 4. Powder XRD patterns of CoBDC (a), Pd/CoBDC before (b) and after
four circles in the catalysis reaction (c), CoBDCNH2 (d) and Pd/CoBDCNH2
before (e) and after four cycles in the catalysis reaction (f). The 2
characteristic for palladium are highlighted (*).
q values
Please cite this article in press as: F. Ashouri, et al., The effect of framework functionality on the catalytic activation of supported
Pd nanoparticles in the MizorokieHeck coupling reaction, Comptes Rendus Chimie (2016), http://dx.doi.org/10.1016/
j.crci.2016.06.002

F. Ashouri et al. / C. R. Chimie xxx (2016) 1e9
5
Fig. 5. TEM images of supported Pd-NPs on CoBDC (a, b) and CoBDCNH2 (c, d) polymer framework.
Fig. 6. SEM images of CoBDC (a), CoBDCNH2 (b, c), Pd/CoBDC (d) and Pd/CoBDCNH2 (e, f).
Using the DebyeeScherer equation, the average diam-
eter of Pd-NPs was estimated to be 30 nm for Pd/CoBDC and
40 nm for Pd/CoBDCNH2, which matched very well with
TEM data as estimated by size distribution. The Pd contents
in Pd/CoBDC and Pd/CoBDCNH2 polymers were determined
(9% and 1% wt, respectively) by inductively coupled plas-
maemass spectroscopy (ICP-MS).
The X-ray photoelectron spectroscopy measurement
(XPS) study demonstrated that the Pd species in polymers
are present in the metallic state (Fig. 7). This is verified by
the two peaks with a binding energies of 335.6 and 341.1 eV
in Pd/CoBDC (Fig. 7a) and 336.3 and 341.9 eV in Pd/
CoBDCNH2 (Fig. 7b) in the 3d5/2 and 3d3/2 levels of Pd(0),
respectively. Photoelectrons emitted from carboxyl groups,
Fig. 7. Wide scan XPS spectra of the Pd/CoBDC (a) and Pd/CoBDCNH2 (b) with Pd core level spectra.
Please cite this article in press as: F. Ashouri, et al., The effect of framework functionality on the catalytic activation of supported
Pd nanoparticles in the MizorokieHeck coupling reaction, Comptes Rendus Chimie (2016), http://dx.doi.org/10.1016/
j.crci.2016.06.002

6
F. Ashouri et al. / C. R. Chimie xxx (2016) 1e9
C 1s and O 1s core level in the 1,4-benzenedicarboxylate
linker in Pd/CoBDC, generated peaks centered at 284 and
533 eV binding energy, respectively [23]. Photoelectrons
emitted from carboxyl groups and an amine branch, C 1s, N
1s and O 1s core level in Pd/CoBDCNH2, generated peaks
centered at 285.5, 399.8 and 532 eV binding energy,
respectively. The peaks at 788 and 800 eV were assigned to
suitable reaction conditions to achieve the maximum yield
of the MizorokieHeck reaction, conditions such as solvent,
base and reaction temperature were studied by choosing
styrene and iodobenzene as a model reaction (Table 1). The
excellent yields of products were obtained in dimethyla-
cetamide (DMA) (entries 1e5) even at a lower temperature
(entry 14). Among the different organic and inorganic
bases, the highest conversion of coupling reactions was
observed in the presence of Et3N base (entries 3, 8, 11e13).
A controlled experiment indicated that no cross-coupling
product was observed in the absence of the catalyst or
base (entries 15, 16).
Co(2p3/2) and Co(2p1/2) in the Co-O6 environment,
respectively [26].
3.2. MizorokieHeck coupling reaction of iodobenzene and
terminal alkenes in the presence of supported Pd-NPs
The coupling between iodobenzene and various termi-
nal alkenes has been investigated under the above-
optimized reaction conditions, Et3N as the base and DMA
as the solvent at 90 ꢀC (Table 2). The results show that in the
presence of supported PdNPs, alkenes with either electron-
withdrawing or electron-donating substituents react with
The coupling of CeC bonds constitutes significant re-
actions in organic chemistry that can lead to a diverse range
of derivatives. Therefore, the catalytic activity of supported
PdNPs on the coordination polymers was applied to the
MizorokieHeck coupling reaction. In order to find the
Table 1
Optimization of the reaction conditions in the cross coupling reaction of iodobenzene and styrene in the presence of Pd/CoBDC and Pd/CoBDCNH2 catalysts.a
I
cat.
Base
+
+
Entry
1
Catalyst
Solvent
DMSO
Base
Et3N
% Conversionb
% Selectivityc
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
Pd/CoBDC
Pd/CoBDCNH2
e
80
80
87
90
95
97
55d
50d
20
25
60
55
70
75
75
78
70
70
82
82
85
85
15
17
13
10
70e
65e
1
90
95
88
90
92
95
85
85
70
75
85
85
85
85
82
82
82
82
90
90
90
90
85
87
87
85
88
85
e
2
DMF
Et3N
3
DMA
CH3CN
p-xylene
DMSO
DMF
Et3N
4
Et3N
5
Et3N
6
K2CO3
7
K2CO3
8
DMA
DMSO
DMF
K2CO3
9
NaCH3CO2
NaCH3CO2
NaCH3CO2
Pyridine
Pyrrolidine
10
11
12
13
14
15
16
DMA
DMA
DMA
DMA
DMA
DMA
Et3N
e
2
e
Et3N
1f
e
e
1f
e
a
Reaction conditions: 13 mg Pd/CoBDC (0.11 mol % Pd), 5 mg Pd/CoBDCNH2 (0.05 mol % Pd), styrene 1.1 mmol, iodobenzene 1 mmol, base 1.5 mmol,
temperature 90 ꢀC, after 9 h.
b
Determined by GC, based on iodobenzene; average of two runs.
Selectivity to trans-stilbene.
Solvent boiling point.
Temperature 70 ꢀC.
c
d
e
f
Reaction without catalyst.
Please cite this article in press as: F. Ashouri, et al., The effect of framework functionality on the catalytic activation of supported
Pd nanoparticles in the MizorokieHeck coupling reaction, Comptes Rendus Chimie (2016), http://dx.doi.org/10.1016/
j.crci.2016.06.002

F. Ashouri et al. / C. R. Chimie xxx (2016) 1e9
7
Table 2
The coupling reaction of iodobenzene and terminal alkenes catalyzed by Pd/CoBDC and Pd/CoBDCNH2.a
I
R
Cat, Et3N
R
+
DMA, 90 o
C
Entry
1
Catalyst
Olefin
% Conversionb
% Selectivity to product
Pd/CoBDC
Pd/CoBDCNH2
95
97
92
95
2
3
4
Pd/CoBDC
Pd/CoBDCNH2
85
85
90
90
Pd/CoBDC
Pd/CoBDCNH2
84
75
H3CO
H3CO
88
90
Pd/CoBDCNH2
Pd/CoBDC
15
15
90
90
CN
CN
5
6
Pd/CoBDC
Pd/CoBDCNH2
90
90
85
86
O
O
Pd/CoBDC
Pd/CoBDCNH2
95
99
O
O
100
100
O
O
7
8
9
Pd/CoBDC
Pd/CoBDCNH2
85
98
O
O
100
100
O
O
O
Pd/CoBDC
Pd/CoBDCNH2
80
80
(CH2)10
O
(CH2)10
77
78
O
O
Pd/CoBDC
Pd/CoBDCNH2
55
55
O
O
OH
OH
60
65
(continued on next page)
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8
F. Ashouri et al. / C. R. Chimie xxx (2016) 1e9
Table 2 (continued)
Entry
Catalyst
Olefin
% Conversionb
% Selectivity to product
O
O
10
Pd/CoBDC
Pd/CoBDCNH2
75
80
O
O
92
90
a
Reaction conditions: 13 mg Pd/CoBDC (0.11 mol % Pd), 5 mg Pd/CoBDCNH2 (0.05 mol % Pd), 1.1 mmol substrate, 1 mmol iodobenzene, 1.5 mmol Et3N, in
DMA solvent, temperature 90 ꢀC, after 9 h.
b
Determined by GC, based on iodobenzene; average of two runs.
iodobenzene, rapidly forming the corresponding coupled
products with good yields and excellent selectivity to E-
isomeric products (Table 2). The conversion and selectivity
of products show that the coupling reactions catalyzed by
both catalysts proceed through the same mechanism pro-
posed in the literature [23].
Since some of the active sites in the solid catalyst could
dissolve into the solution during the catalytic reaction, the
amount of palladium in solution after each catalytic run
was determined by ICP-MS to find whether palladium
leaching occurs during the reaction. Therefore, after the
first catalytic reaction of iodobenzene and styrene by Pd/
CoBDC and Pd/CoBDCNH2, the heterogeneous catalyst was
simply separated from the reaction mixture by centrifu-
gation and the content of palladium in solution was
determined by ICP-MS (Table 3). The leaching test after
each catalytic run revealed that the amount of palladium
leached from the catalyst to solution is very negligible.
Moreover, fresh reagents were added to the solution and
stirred at 90 ꢀC. Only less than 6% conversion was observed
after 24 h for both catalysts. Therefore, there is no contri-
bution of catalytically active palladium leached species in
solution.
In order to further confirm that the reaction was indeed
catalyzed by supported PdNPs instead of free Pd-NPs in
styrene and iodobenzene coupling reaction, a hot filtration
test was carried out by stopping the reaction after 3 h. The
reaction reached 25 and 32% conversion for Pd/CoBDC and
Pd/CoBDCNH2, respectively. Then the catalyst was sepa-
rated from the reaction mixture and reaction was
continued. The conversion was increased by 6 and 7%,
respectively, after 24 h. These results confirmed that the
coupling reaction could only continue in the presence of
the solid catalyst, and there was no contribution from the
homogeneous catalysis of leached active species in the
liquid phase.
The recyclability of the supported Pd-NPs catalyst was
investigated in the reaction of styrene with iodobenzene
using Et3N/DMA at 90 ꢀC for 9 h in the presence of Pd/
CoBDC (13 mg, 0.11 mol % Pd) and Pd/CoBDCNH2 (5 mg,
0.05 mol % Pd). The solid catalyst was easily isolated by
centrifugation after the first catalytic reaction and recov-
ꢀ
ered by being washed with the solvent and dried at 80 C.
Afterwards, it was used for the next run under the same
reaction conditions. The catalytic activity was found to
remain almost unchanged even after four cycles, without
significant degradation in activity and selectivity to trans-
stilbene as a major E-product (Table 3).
The catalytic results show that supported PdNPs on
polymers are active catalysts in the CeC coupling reaction.
For C-C coupling reaction of iodobenzene and terminal
olefins, amount of 13 mg (0.11 mol % Pd) from Pd/CoBDC
catalyst and 5 mg (0.05 mol % Pd) from Pd/CoBDCNH2
catalyst, were used. So, from a catalytic point of view, the
Pd/CoBDCNH2 is superior in terms of the amount of the
catalyst. It seems that highly dispersed and low loading
PdNPs on CoBDCNH2 (1%) are efficient than aggregated and
high loading Pd-NPs on CoBDC (9%). This fact demonstrates
the functionality effect of the polymer on catalyst
efficiency.
The XRD patterns of catalysts after the reaction dis-
played the same diffraction profile and relatively similar
intensity that indicated that the catalysts retained a well-
crystallized structure after the catalytic reaction (Fig. 4c,f).
Table 3
The reusability and palladium leaching test in the MizorokieHeck
coupling reaction of iodobenzene with styrene catalyzed by Pd/CoBDC and
Pd/CoBDCNH2 heterogeneous catalysts.a
4. Conclusion
Supported palladium nanoparticles (Pd-NPs) on the
functional and nonfunctional Co-coordination polymers
were prepared using a solution impregnation method. Pd-
NPs are highly dispersed on the functional polymer with an
average diameter of 30 nm and a loading of 1%, while the
nonfunctional polymer showed high loading (9%) and
aggregated Pd-NPs with an average diameter of 40 nm.
Therefore, not only does the functional framework prohibit
the aggregation of Pd-NPs, but it also causes the catalyst Pd/
CoBDCNH2 to show high efficacy in comparison to Pd/
CoBDC despite being less in amount (5 mg Pd/CoBDCNH2,
Entry
Catalyst
Conversion (%) Selectivity (%)b % Pdc
Run 1 Pd/CoBDC
95
Pd/CoBDCNH2 97
92
95
92
95
91
95
91
94
0.15
0.02
0.08
0.007
0.05
0.004
0.02
<0.001
Run 2 Pd/CoBDC
91
Pd/CoBDCNH2 95
Run 3 Pd/CoBDC
87
Pd/CoBDCNH2 92
Run 4 Pd/CoBDC
85
Pd/CoBDCNH2 88
a
b
c
Reaction conditions: same as those in Table 2.
Selectivity (%) to E-product.
The palladium content in the solution, determined by ICP-MS.
Please cite this article in press as: F. Ashouri, et al., The effect of framework functionality on the catalytic activation of supported
Pd nanoparticles in the MizorokieHeck coupling reaction, Comptes Rendus Chimie (2016), http://dx.doi.org/10.1016/
j.crci.2016.06.002

F. Ashouri et al. / C. R. Chimie xxx (2016) 1e9
9
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Acknowledgements
F.A. acknowledges the research council of the Sharif
University of Technology and Pharmaceutical Sciences
Branch-Islamic Azad University for the research funding of
this project.
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Please cite this article in press as: F. Ashouri, et al., The effect of framework functionality on the catalytic activation of supported
Pd nanoparticles in the MizorokieHeck coupling reaction, Comptes Rendus Chimie (2016), http://dx.doi.org/10.1016/
j.crci.2016.06.002