Highly active palladium nanoparticles immobilized on NH2-MIL-125 as efficient and recyclable catalysts for Suzuki-Miyaura cross coupling reaction

Article abstract of DOI:10.1016/j.catcom.2015.02.017

Abstract Pd nanoparticles were deposited successfully on a porous metal-organic framework NH₂-MIL-125, and characterized by powder X-ray diffraction, thermogravimetric analysis, N₂ adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and field emission transmission electron microscopy. The as-synthesized NH₂-MIL-125-supported palladium nanoparticles exhibited excellent heterogeneous catalytic performance towards Suzuki cross coupling between the aryl chlorides and arylboronic acids. The catalyst could be reused at least four times under the optimized conditions with only a minor decrease in catalytic activity. The Sheldon test confirmed the heterogeneity of the catalyst.

Full text of DOI:10.1016/j.catcom.2015.02.017

Highly active palladium nanoparticles immobilized on NH2-MIL-125 as
efficient and recyclable catalysts for Suzuki-Miyaura cross coupling reaction
Pillaiyar Puthiaraj, Wha-Seung Ahn
PII:
DOI:
Reference:
S1566-7367(15)00076-X
doi: 10.1016/j.catcom.2015.02.017
CATCOM 4234
To appear in:
Catalysis Communications
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Revised date:
Accepted date:
30 December 2014
10 February 2015
12 February 2015
Please cite this article as: Pillaiyar Puthiaraj, Wha-Seung Ahn, Highly active pal-
ladium nanoparticles immobilized on NH2-MIL-125 as efficient and recyclable cata-
lysts for Suzuki-Miyaura cross coupling reaction, Catalysis Communications (2015), doi:
10.1016/j.catcom.2015.02.017
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Highly Active Palladium Nanoparticles Immobilized on NH2-MIL-
125 as Efficient and Recyclable Catalysts for Suzuki-Miyaura Cross
Coupling Reaction
Pillaiyar Puthiaraj and Wha-Seung Ahn*
Department of Chemistry and Chemical Engineering, Inha University,
Incheon 402-751, South Korea
*E-mail: whasahn@inha.ac.kr
Abstract
Pd nanoparticles were deposited successfully on a porous metal-organic framework
NH2-MIL-125, and characterized by powder X-ray diffraction, thermogravimetric analysis,
N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and field emission
transmission electron microscopy. The as-synthesized NH2-MIL-125-supported palladium
nanoparticles exhibited excellent heterogeneous catalytic performance towards Suzuki cross
coupling between the aryl chlorides and arylboronic acids. The catalyst could be reused at
least four times under the optimized conditions with only a minor decrease in catalytic
activity. The Sheldon test confirmed the heterogeneity of the catalyst.
Keywords: Metal-Organic Frameworks, Palladium nanoparticles, Suzuki coupling,
Titanium, Heterogeneous catalyst.
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Introduction
The palladium-catalyzed Suzuki coupling reaction is one of the most powerful means
for selective C–C bond formation for the construction of symmetrical and asymmetrical
biaryl skeletons, which are often included as a component in pharmaceuticals, natural
products and functional materials [1]. Conventionally, homogeneous catalysts consisting of
palladium complexes with a variety of nitrogen and phosphine based ligands are normally
used in these reactions, and many studies have reported improvements in the activity and
selectivity of these catalysts [2]. Many organometallic compounds with elaborately designed
ligands have been used as catalysts in this reaction, but most suffer from drawbacks, such as
high ligand sensitivity towards air and moisture, tedious multistep ligand synthesis and work-
up with high cost, as well as use of various additives and hazardous organic solvents [3].
Industrial applications of these homogeneous catalysts for coupling reactions also remains
challenging because the limited availability of the ligands and high cost of palladium
complexes, difficulties in separation and reusability/recycle, and metal leaching of these
expensive palladium catalysts make them difficult to use in large scale chemical processes.
To overcome these problems and make the process more environmentally benign and
economical, researchers are focusing on solid supported palladium complexes or palladium
nanoparticles (NPS) supported on carbon, silica, zeolites, metal organic frameworks, or
covalent organic polymers for the selective C-C bond forming reaction [4].
Although these heterogeneous palladium catalysts are attractive for the Suzuki
coupling reactions of aryl iodides and bromides, their catalytic activities were reported to be
somewhat unsatisfactory for aryl chlorides, which are more difficult to activate [5]. As aryl
chlorides are inexpensive and readily available compared to aryl iodides or bromides,
developing a heterogeneous palladium catalyst system with high catalytic activity are
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desirable from an industrial point of view. However, the palladium catalyzed homocoupling
of arylboronic acid is one of the side products during the Suzuki coupling reaction with less
reactive aryl chlorides [6].
Metal-organic frameworks (MOFs) have attracted considerable interest in recent years
because of their highly porous nature, diverse organic functionalization available, modularity,
and structural diversity [7]. Based on these properties, MOFs have been employed
increasingly as heterogeneous catalysts for some organic transformations, especially as a
support material for the immobilization of metal nanoparticles [8]. Cao et al. reported that
palladium NPs supported on NH2-MIL-53(Al) catalyzed Suzuki coupling reactions of
arylbromides [9]. Garcia et al. reported the Pd@MOF with the formula [Pd(2-pymo)2]n (2-
pymo = 2-hydroxypyrimidinolate) catalyzed Suzuki coupling reactions of 4-bromoanisole at
150oC [10]. Jin et al. reported the Suzuki coupling reactions of aryl iodides and bromides by
[Pd(diimine)Cl2] incorporated MOF, which suffered leaching during the reaction [11]. Jiang
et al. showed that Pd/MIL-101 catalyzed the Suzuki coupling reactions of aryl chlorides with
an external tetrabutylammonium bromide (TBAB) additive and the catalyst could be reused
up to five times [12]. Zadehahmadi et al. reported the amino-functionalized NH2-UiO-66 as a
support for Pd and carried out the Suzuki coupling reactions in dimethylformamide (DMF):
water mixture (v/v, 2:2) and the catalyst was reusable several times [13]. Liang et al.
prepared a [Pd(C3H5)(C5H5)]@MOF-5 catalyst by a chemical vapor deposition method, and
tested it as a catalyst for Suzuki reaction of bromobenzene in DMF [14]. Wang et al. reported
Pd NPs encapsulated on MIL-101 for Suzuki coupling reaction of aryl iodides and bromides
at room temperature [15]. Recently, Matute et al. reported the Suzuki coupling reaction with
aryl iodides and bromides catalyzed by Pd NPs supported on a functionalized mesoporous
MOF (Pd@MIL-101(Cr)-NH2) [16]. Yamashita et al. reported the amine-functionalized
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MIL-125 with imbedded palladium nanoparticles as a catalyst for the dehydrogenation of
formic acid at ambient temperature [17]. This paper shows that the amino-functionalized
titanium-based MOF, NH2-MIL-125, is an excellent solid support for palladium NPs
(Pd@NH2-MIL-125), which produces an efficient and reusable heterogeneous catalyst for the
Suzuki coupling reaction of aryl chlorides without employing external additives, an inert
atmosphere, or highly toxic organic solvents. The catalyst was reusable up to four
consecutive runs with only a minor decrease in catalytic activity, and without leaching of the
catalyst or structural change of the MOF structure (Scheme 1).
2. Experimental Section
2.1 General Methods
All chemicals were purchased from commercial suppliers and used as received unless
otherwise noted. The powder X-ray diffraction (PXRD) patterns were recorded on a Rigaku
diffractometer using CuKα (λ=1.54 Å) with 0.5o min-1. The N2 adsorption- desorption
isotherms were measured in a BELsorp-Max (BEL, JAPAN) at 77K. The specific surface
areas and pore volumes of the samples were calculated using the BET (Brunauer–Emmett–
Teller) method, respectively. Field emission transmission electron microscopy (FETEM) was
performed using a FEI TECNAI 30 G2 S-TWIN instrument. The thermal stability of the
samples was evaluated by thermogravimetric analysis (TGA, SCINCO thermal gravimeter S-
o
1000) under a nitrogen atmosphere over the temperature range, 30–600 C, in flowing
o
nitrogen at a heating rate of 5 C min-1. The palladium content was measured by inductively
coupled plasma spectrometry (ICP-OES, Optima 7300DV). The products were analyzed
using a GC (Agilent Technologies, 7890A) fitted with a high performance HP-5 capillary
column and a flame ionization detector. X-ray photoelectron spectroscopy (XPS, Thermo
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scientific) was performed using a monochromatic Al Kα X-ray source and a hemispherical
analyzer. The NMR spectra were recorded using a 300 MHz Brucker spectrometer.
2.2 Synthesis of NH2-MIL-125
NH2-MIL-125 was prepared according to a reported procedure [18]. 2-
aminoterephthalic acid (15 mmol) was introduced to a mixture of 50 mL of N,N-
dimethylformamide (DMF) and 12 mL of methanol at room temperature with stirring. After 1
h, 10 mmol of titanium (IV) isopropoxide was added. The reaction mixture was kept under
stirring and heated under reflux for 72 h at 100 °C. The resulting mixture was cooled to room
temperature and a yellow solid powder was recovered by filtration, washed twice with DMF
to remove the unreacted organic ligand, and then washed with methanol to exchange the
o
DMF. The yellow product was activated under vacuum at 100 C to remove the methanol
from the pores.
2.3. Synthesis of palladium nanoparticles supported on NH2-MIL-125 (Pd@NH2-
MIL-125)
500 mg of NH2-MIL-125 powder was suspended in 50 mL of methanol and 30 mg of
PdCl2 in 1 mL of aqueous solution with HCl was then added. Subsequently, the vessel was
sealed with a rubber septum. After 12 h, the solid was filtered and washed with methanol to
remove the unreacted palladium chloride. The freshly prepared Pd(II)/NH2-MIL-125 was
added to 50 mL of methanol. Hydrazine hydrate (1 mL) was then added dropwise to the
suspension with vigorous stirring; the mixture turned a light green color immediately. After
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stirring for 30 min, the solid was isolated by centrifugation, and Pd@NH2-MIL-125 was
obtained as a light green color powder, which was kept under a nitrogen atmosphere.
2.4. Suzuki cross coupling reaction between aryl chlorides and arylboronic acids
In a typical reaction, a mixture of aryl chloride (1 mmol), arylboronic acid (1.3
mmol), base (1.5 mmol), and the catalyst (60 mg, 0.9 mol% of Pd against aryl chloride
substrate) in methanol (3 mL) were placed in a round bottom flask with a reflux condenser.
The resulting mixture was stirred and kept under reflux for 22 h at 100 oC. After the reaction
was complete, the mixture was cooled to room temperature and the catalyst was filtered off.
The reaction products were analyzed using a GC fitted with a high performance HP-5
capillary column and a flame ionization detector.
3. Results and Discussion
3.1. Characterization of NH2-MIL-125
The synthesized NH2-MIL-125 was characterized by PXRD, TGA and N2 adsorption-
desorption isotherms. In PXRD, a very sharp peak at approximately 7° 2θ was observed,
which indicated that the material was highly crystalline (Fig. 1a). TGA of NH2-MIL-125 over
the temperature range, 80-100 oC, revealed the loss of methanol used as the washing solvent,
o
and the framework decomposition of NH2-MIL-125 was observed at approximately 300 C
(Fig. S1). The overall PXRD pattern and thermal stability of the NH2-MIL-125 were in good
agreement with previous reports [19,20]. The N2 adsorption–desorption isotherms of the
NH2-MIL-125 sample exhibited a type I isotherm at 77 K with no hysteresis (Fig. S2). Table
1 summarizes the textural properties.
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3.2. Characterization of Pd@NH2-MIL-125
The synthesized Pd@NH2-MIL-125 was characterized by PXRD, TGA, N2
adsorption-desorption isotherms, ICP analysis, XPS, and FE-TEM. The crystallinity of the
Pd@NH2-MIL-125 was examined by PXRD, which was comparable to NH2-MIL-125, which
confirmed that the framework and crystallinity of NH2-MIL-125 had been maintained after
deposition of the Pd NPs (Fig. 1). As shown in Fig. 1, the Pd NPs peaks were observed at
40.1o and 68.4o in XRD pattern of Pd@NH2-MIL-125 catalyst, which correspond to (111)
and (220) planes of fcc structure, respectively [4b,20]. The TGA curve of Pd@NH2-MIL-125
o
revealed good thermal stability up to 280 C (Fig. S1). The electronic state of the palladium
species that are bound strongly to the nitrogen atoms in the NH2-MIL-125 were confirmed by
XPS (Fig. S3 & S4). XPS of the fresh Pd@NH2-MIL-125 catalyst exhibited two strong
binding energy peaks at 335.2 and 340.4 eV for the 3d5/2 and 3d3/2 core levels, respectively,
which indicates that the palladium species in the catalyst are in the metallic state (Fig. S3a).
The N1s binding energy of the fresh and after the 4th use of the catalyst at 399.2±2 eV clearly
shows that palladium metallic species are strongly bound to nitrogen atoms in the NH2-MIL-
125 frameworks (Fig. S4). The FE-TEM image in Fig. S5 showed that the Pd NPs are 8 to 13
nm in size. The Pd NPs were too large to enter into the pores of NH2-MIL-125 (the
framework pore diameter is ca. 0.66 nm) and found dispersed on the external surface of the
NH2-MIL-125 frameworks via electrostatic interactions with the amino group of the linker
[21]. ICP analysis revealed the Pd@NH2-MIL-125 to have a Pd content of 1.61 wt. %.
3.3. Catalytic activity of Pd@NH2-MIL-125
Pd@NH2-MIL-125 was tested as a catalyst for the Suzuki coupling of aryl chlorides.
The reaction parameters were optimized using chlorobenzene and phenylboronic acid as a
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screening substrate, and the results are summarized in Table 2. The reaction did not proceed
either in the absence of a catalyst (Table 2, entry 1) or in the presence of NH2-MIL-125
(Table 2, entry 2), which indicates the specific role of the Pd NPs as a catalyst in the Suzuki
cross coupling reaction. Only trace amounts of product was observed with PdCl2 (3 mol%) in
o
the absence of a support as the catalyst in methanol using K2CO3 as a base at 100 C. With
o
Pd@NH2-MIL-125 in MeOH at 100 C, however, the desired product was obtained in 86 %
yield (Table 2, entry 4), confirming the effectiveness of the solid supported Pd nanoparticles
catalyst to increase the reactivity and reusability of the catalyst. No product was observed in
the absence of a base (Table 2, entry 5). A range of solvents were also tested to optimize the
reaction conditions (Table 2, entries 6-11), and an 80, 76, 46, 37, 43 and 39% yield of the
desired coupling products were observed using ethanol, 1,4-dioxane, DMF, dimethyl
sulfoxide (DMSO), N,N’-dimethylacetamide (DMAc), and acetonitrile (ACN), respectively.
On the other hand, the use of a solvent mixture such as DMF:MeOH, H2O:MeOH,
H2O:EtOH, and H2O:iPrOH (v/v; 1:1) resulted in 53, 75, 71 and 69 % yield, respectively
(Table 2, entries 12-15). Among the various inorganic bases employed for this coupling
reaction, K2CO3 gave a higher product yield than NaHCO3 and KOH (Table 2, entries 16-17).
o
When we decreased the reaction temperature to 90 and 80 C, the yield of cross coupled
product had decreased to 74, and 58% respectively (Table 2, entry 18), whereas increasing
the temperature above 100 oC, no obvious change in yield was observed.
The amount of catalyst and the reaction time were also investigated to determine the
optimal reaction conditions. With 0.3 mol% of Pd catalyst, the reaction proceeded slowly
with 23% yield. When the amount of catalyst was increased to 0.6 mol%, the reaction rate
increased with 59% conversion, and the yield was increased further to 86% when the amount
was 0.9 mol% (Table 2, entry 19). Increasing the reaction time from 2 to 22 h increased the
overall yield from 22 to 86%, but further increases in reaction time had no positive effect on
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the overall product yield (Fig. 2a). Therefore, the optimized set of reaction conditions for
chlorobenzene (1 mmol) and phenylboronic acid (1.3 mmol) were as follows: Pd@NH2-MIL-
125 (60 mg, 0.9 mol%) as a catalyst, K2CO3 (1.5 mmol), and MeOH (3 mL) as a solvent
heated at 100 ºC for 22 h.
The reusability of the Pd@NH2-MIL-125 catalyst was then investigated in the Suzuki
coupling reaction under optimized conditions and the results are summarized in Fig. 3 and
Table 3). After the reaction was complete, the catalyst was recovered by centrifugation after
decanting the supernatant and washed three times with DMF. The recovered catalyst was
used for a further four consecutive runs. Only a minor decrease (from 86 to 78%) in catalyst
activity observed, highlighting the good stability of the Pd@NH2-MIL-125 catalyst. After the
4th use, the catalyst stability was further examined by PXRD, XPS and BET surface area
analysis. The PXRD pattern of the fourth used catalyst catalyst was similar that of the fresh
catalyst (Fig. 1c). The BET surface areas (Table 1) and PXRD patterns also clearly show that
no structural change took place in the framework of the material.
The heterogeneity of the Pd@NH2-MIL-125 catalyst and the absence of metallic
species in the filtrate were confirmed using a Sheldon test [22]. The reaction was performed
under optimal conditions, and the reaction mixture at 100 °C was cooled to room temperature
over a 12 h period and the catalyst was removed by centrifugation. The supernatant was then
heated to 100 °C for an additional 10 h and no further reaction was observed (Fig. 2b). These
results clearly show that there was no leaching of metal ions under the present reaction
conditions. The absence of metal leaching was further confirmed by ICP analysis, which
revealed a 1.61% and 1.59% palladium metal content in the fresh and after the 4th use,
respectively. XPS of the catalyst after the 4th use revealed two strong binding energy peaks in
the same region of the fresh catalyst, which indicates that the catalyst had retained the
original palladium metallic state after reaction (Fig. S3b & S4b).
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Finally, the performance of Pd@NH2-MIL-125 catalyst on the Suzuki coupling
reaction was investigated further for different arylboronic acids and aryl chlorides under the
optimized reaction conditions, and the observed results are summarized in Table 4. All the
para- and meta- substituted substrates gave the desired cross coupled product with a good to
excellent yield of the different groups present in the substrates (Table 4, entries 1-8). Ortho-
substituted arylchlorides gave only slightly lower yields (Table 4, entries 9-11) compare to
para- and meta- substituted substrates. The 3-chloropyridine substrate also gave the
corresponding coupled product in good yield (Table 4, entries 12).
Table S1 summarizes the reaction conditions, catalytic activity and efficiency among
the various heterogeneous catalysts employed in previous studies for the Suzuki cross
coupling of aryl chlorides with arylboronic acids. A comparison of the results indicates that
Pd@NH2-MIL-125 (entry 22) exhibits comparable catalytic activity to the other reported
catalysts. More importantly, Pd@NH2-MIL-125 was free of the limitations imposed on other
catalyst systems, such as those requiring external additives (entries 1, 4, 7 & 8), an inert
atmosphere (entries 6, 7 & 13), harmful organic solvents (entries 4-6, 9, 11 & 13), or higher
temperatures (entries 4 & 5).
4. Conclusions
Pd nanoparticles deposited on a titanium-based MOF, Pd@NH2-MIL-125, was
synthesized and investigated as a catalyst for the facile and efficient Suzuki coupling reaction
of aryl chlorides with boronic acids. The catalyst was easily recoverable and could be reused
with good catalytic activity. The heterogeneity of the reaction was confirmed using a Shelton
test and no metal leaching was observed by ICP. Pd@NH2-MIL-125 was active for
promoting reactions among different arylboronic acids and aryl chlorides under the optimized
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reaction conditions, and was free from the necessity of external additives, an inert
atmosphere, or highly toxic organic solvents for the Suzuki coupling reaction.
Acknowledgement
This study was supported by a National Research Foundation of Korea (NRF) grant
funded by the Korean Government (MEST) (No. 2013005862).
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Scheme 1. Pd@NH2-MIL-125 catalyzed Suzuki coupling reaction
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Fig. 1. Powder XRD patterns of NH2-MIL-125, fresh Pd@NH2-MIL-125, and Pd@NH2-
MIL-125 catalyst after the 4th use.
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Fig. 2. Time conversion plot for the Suzuki coupling of chlorobenzene with phenylboronic
acid, (b) after removing the catalyst at 64% product formation
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-
Fig. 3. Recycling experiment of the Pd@NH2 MIL-125 catalyst
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Table 1 N2 sorption isotherm data of NH2-MIL-125, fresh and reused palladium loaded NH2-
MIL-125
Sample
SBET (m2g-1) Vpore (cm3g-1) Pore width (nm)
-
NH2 MIL-125
1562
1191
1076
0.90
0.75
0.69
0.66
0.61
0.64
-
Fresh Pd@NH2 MIL-125
Reused Pd@NH2 MIL-125
-
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Table 2 Optimization of the reaction conditions[a]
Entry Base
Solvent
Conversion (%)[b]
1[c]
2[d]
3[e]
4
K2CO3
MeOH
0
K2CO3
K2CO3
K2CO3
-
MeOH
0
MeOH
3
MeOH
86
5
MeOH
0
6
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
NaHCO3
KOH
DMF
46
7
DMSO
37
8
DMAc
43
9
EtOH
80
10
11
12
13
14
15
16
17
18
19
1,4-Dioxane
ACN
76
39
DMF:MeOH[f]
H2O:MeOH[f]
H2O:EtOH[f]
H2O:iPrOH[f]
MeOH
53
75
71
69
42
MeOH
51
K2CO3
MeOH
58[g], 74[h], 87[i]
86[j], 62[k], 27[l]
K2CO3
MeOH
[a]Reaction Conditions: Chlorobenzene (1 mmol), phenylboronic
acid (1.3 mmol), base (1.5 mmol), Pd@NH2-MIL-125 (1.2 mol% of
o
Pd) solvent (3 mL), 100 C, 24 h; [b]GC analysis, conversion based
on chlorobenzene; [c]Without catalyst; [d]NH2-MIL-125 (80 mg)
alone; [e]3 mol% of PdCl2 catalyst; [f]1:1 (v/v) ratio; [g]80 oC; [h]90 oC;
[i]110 oC; [j]0.9 mol% of Pd; [k]0.6 mol% of Pd; [l]0.3 mol% of Pd.
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-
Table 3. Reusability of Pd@NH2 MIL-125 in the Suzuki Coupling reaction of
chlorobenzene[a]
Runs
1st
86
2nd
84
3rd
80
4th
78
Yield (%)[b]
TOF (h-1) [c]
4.3
4.2
4.0
3.9
[a]Reaction Conditions: Chlorobenzene (1 mmol), phenylboronic
acid (1.3 mmol), K2CO3 (1.5 mmol), MeOH (3 mL), Pd@NH2
-
MIL-125 (0.9 mol% of Pd), 22 hrs; [b]GC analysis, conversion
based on chlorobenzene; [c]Turnover frequency (h-1).
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[a]
-
Table 4 Pd@NH2 MIL-125 promoted Suzuki coupling reaction with different substituents
Yield (%)[b]
Entry Aryl Chlorides
Arylboronic acids
C6H5B(OH)2
(3)
3a
3b
3c
3d
3e
3f
TOF (h-1)[c]
4.3
1
C6H5-Cl
86
83
84
80
81
78
82
80
72
74
67
79
2
4-CH3-C6H4-Cl
C6H5B(OH)2
4.2
3
4-OCH3-C6H4-Cl C6H5-B(OH)2
4.2
4
C6H5-Cl
4-CH3-C6H4-B(OH)2
4.0
5
3-CH3-C6H4-Cl
3-NO2-C6H4-Cl
C6H5-Cl
C6H5-B(OH)2
4.1
6
C6H5-B(OH)2
3.9
7
4-OCH3-C6H4-B(OH)2
4.1
3g
3h
3i
8
4-OCH3-C6H4-Cl 4-OCH3-C6H4-B(OH)2
2-CH3-C6H4-Cl C6H5-B(OH)2
2-OCH3-C6H4-Cl C6H5-B(OH)2
4.0
9
3.6
10
11
12
3.7
3j
2-NO2-C6H4-Cl
3-Cl-Pyridine
C6H5-B(OH)2
C6H5-B(OH)2
3.4
3k
3l
4.0
[a]Reaction Conditions: Chlorobenzene (1 mmol), phenylboronic acid (1.3 mmol),
K2CO3 (1.5 mmol), MeOH (3 mL), Pd@NH2 MIL-125 (0.9 mol% of Pd), 22 hrs; [b]GC
-
analysis, conversion based on aryl chlorides; [c]Turnover frequency (h-1).
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Highly Active Palladium Nanoparticles Immobilized on NH2-MIL-
125 as Efficient and Recyclable Catalysts for Suzuki-Miyaura Cross
Coupling Reaction
Pillaiyar Puthiaraj and Wha-Seung Ahn*
Department of Chemistry and Chemical Engineering, Inha University,
Incheon 402-751, South Korea
*E-mail: whasahn@inha.ac.kr
Highlights of the present work
1. Pd NPs were deposited on NH2-MIL-125 and characterized.
2. The catalyst promoted Suzuki coupling without external additives.
3. The catalyst was recovered easily and reused for at least four runs.
22