A new hybrid nanocatalyst based on Cu-doped Pd-Fe3O4 for tandem synthesis of 2-phenylbenzofurans

Article abstract of DOI:10.1039/c5ta05111h

We report a one-pot synthesis of hybrid nanocomposites of Cu-doped Pd-Fe₃O₄via controlled thermal decomposition of Fe(CO)₅ and reduction of Pd(OAc)₂ and Cu(acac)₂. Sodium oleate, used as a capping age

Full text of DOI:10.1039/c5ta05111h

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New hybrid nanocatalyst based on Cu-doped Pd-Fe O for
3
4
tandem synthesis of 2-phenylbenzofurans
a
a
b
c
c
Hyunje Woo, Daeho Kim, Ji Chan Park, Ji-Woong Kim, Sungkyun Park, Jae
d
a
Myung Lee and Kang Hyun Park *
a
Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National
University, Busan 609ꢀ735, Korea.
Phone: (+82)ꢀ51ꢀ510ꢀ2238; Fax: (+82)ꢀ51ꢀ980ꢀ5200; eꢀmail: chemistry@pusan.ac.kr
b
Clean Fuel Laboratory, Korea Institute of Energy Research, Daejeon, 305ꢀ343, Korea.
c
Department of physics, Pusan National University, Busan 609ꢀ735, Korea.
d
Department of Naval Architecture & Ocean Engineering, Pusan National University, Busan
609ꢀ735, Korea.
Abstract
We report a oneꢀpot synthesis of hybrid nanocomposites of Cuꢀdoped PdꢀFe
3
O
4
via controlled
. Sodium oleate,
used as a capping agent, affected both the morphologies and surface areas of the Cuꢀdoped
PdꢀFe nanocomposites. To the best of our knowledge, these magnetically recyclable
5 2 2
thermal decomposition of Fe(CO) and reduction of Pd(OAc) and Cu(acac)
3
O
4
hybrid nanocomposites are a new class of nanocatalyst, and the tandem synthesis of 2ꢀ
phenylbenzofuran from 2ꢀiodophenol with phenylpropiolic acid catalyzed by heterogeneous
nanocatalysts has not been reported in the literature. Moreover, Cuꢀdoped PdꢀFe
nanocatalyst is superior to previously reported catalysts for this tandem reaction.
3 4
O
Key words
Hybrid; Nanoparticles; Heterogeneous; Catalyst; Tandem reaction
Introduction
In recent years, much effort has been devoted to the synthesis of hybrid multimetallic
nanoparticles (NPs), because of their advantages such as high selectivity, catalytic activity,
and chemical/physical stability compared with those of the corresponding monometallic
1
,2
components. Pd and Fe
high catalytic activity (Pd) and magnetic reusability (Fe
nanocatalyst. Hybrid PdꢀFe nanocomposites synthesized using various capping agents
3
O
4
nanocomposites have attracted much attention because of the
3
O
4
) of each component in the
3
O
4
3
,4
5
were previously reported by our group. Chen and coworkers reported the synthesis of
6
Pd/Fe
oneꢀpot synthesis of seaꢀurchinꢀlike FePdꢀFe
clusters of FePd NPs with Fe nanorod spikes. These hybrid nanostructures were prepared
using various hydrophilic (e.g., trisodium citrate) or hydrophobic (e.g., oleylamine and oleic
3
O
4
heterodimers with controllable interfaces for CO oxidation. Sun et al. reported a
3
4
O nanocomposites, consisting of spherical
3
O
4

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acid) capping agents.
Until now, the binding selectivity of the capping agents on different crystal facets has affected
7–9
the anisotropic growth of NPs into various shapes such as cubes, rods, and wires; therefore,
the use of specific capping agents provides an effective strategy for the synthesis of nobleꢀ
10
metal nanocrystals. Catalytic selectivity is also sensitive to the packing of atoms on the
11
surface or the exposed facets of a nanocrystal, and it is, therefore, crucial to identify the
interactions between capping agents and NP surfaces clearly to achieve a comprehensive
understanding of NP surface chemistry and to optimize the NP properties and performances
for various applications.
The privileged 2ꢀsubstituted benzofuran motif occurs widely in numerous natural products
12
and pharmaceutical compounds. The tandem synthesis of benzofurans from 2ꢀhalophenols
and terminal alkynes by crossꢀcoupling and subsequent intramolecular hydroalkoxylation is a
1
3
useful and reliable method. However, this tandem reaction using alkynylcarboxylic acids as
coupling partners has not been extensively developed, although alkynylcarboxylic acids are
promising alternatives to terminal alkynes because of their high reactivity, simplicity, and
1
4,15
ready availability from inexpensive aldehydes.
Also, carboxylate groups are the leaving
groups in crossꢀcoupling, and therefore carbon dioxide is the only byproduct. To the best of
our knowledge, the tandem synthesis of 2ꢀphenylbenzofuran from 2ꢀiodophenol with
phenylpropiolic acid catalyzed by heterogeneous nanocatalysts has been not reported in the
literature. In this work, we developed a facile oneꢀpot synthesis of hybrid nanocomposites of
Cuꢀdoped PdꢀFe
hybrid Cuꢀdoped PdꢀFe
the tandem synthesis of 2ꢀphenylbenzofurans.
3
4
O , with a controlled amount of sodium oleate (NaOL; Scheme 1). These
3
O
4
nanocomposites showed high catalytic activities and stabilities in
3 4
Scheme 1 Synthetic scheme of Cuꢀdoped PdꢀFe O nanocomposites.
Experimental
Synthesis of Cu-doped Pd-Fe O and Pd-Fe O -0.3 nanocomposites
3
4
3
4
A mixture solution of sodium oleate (0.3g) and 1ꢀoctadecene (ODE) (10 mL) in a threeꢀ
necked flask was heated to 200 °C under argon flow and magnetic stirring to make sodium
oleate dissolved thoroughly. Then the solution was cooled down to room temperature and a

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mixture of Pd(OAc)
The flask was heated to 60 C and further heated to 120 C at a heating rate of 6 C/min. This
mixture was kept at this temperature for 30 min. Under a blanket of argon gas, Fe(CO) (0.15
2
(0.112 g) and oleylamine (OAm) (10 mL) was added into the solution.
o
o
o
5
o
o
ml) was added. Then the solution was further heated to 160 C at a heating rate of 4 C/min
and kept at this temperature for 30 min. Cu(acac)
2
/OAm solution (32 mg/5 ml) was added
o
o
dropwise in a mixture and heated to 240 C at a heating rate of 2.7 C/min. Then the solution
was kept at this temperature for 30 min. The heating source was removed, and the solution
was cooled to room temperature. A black product was precipitated by adding ethanol and
hexane, and separated by centrifugation.
3 4 5
PdꢀFe O ꢀ0.3 nanocomposites were also synthesized similarly. After Fe(CO) was injected,
o
o
the solution was further heated to 160 C at a heating rate of 4 C/min and kept at this
o
temperature for 30 min. Then, the mixture was further heated to 240 C at a heating rate of
o
2
.7 C/min without addition of Cu(acac)
2
/OAm solution. The solution was kept at this
temperature for 30 min. The heating source was removed, and the solution was cooled to
room temperature. A black product was precipitated by adding ethanol and hexane, and
3 4
separated by centrifugation. The PdꢀFe O ꢀ0.3 nanocomposites were used as a control.
General procedure for tandem synthesis of 2-phenylbenzofurans
The Cuꢀdoped PdꢀFe (generally Cu base: 1 mol% and Pd base: 5.5 mol%), 2ꢀiodophenol
0.056 ml, 0.5 mmol, 1.0 equiv), phenylpropiolic acid (0.088 g, 0.6 mmol, 1.2 equiv), Sodium
3
O
4
(
acetate (0.164 g, 1.0 mmol, 2.0 equiv) and DMSO (5.0 mL) were mixed into a stainless steel
reactor. The mixture was vigorously stirred at 130 °C. After the reaction, catalyst was filtered
and the reaction mixture was extracted with ethylacetate and water. Drying with MgSO
filtration, and solvent evaporation of the filtrate yielded the reaction products.
4
,
Recyclability tests
After the reaction, the catalyst was separated from the clean solution by centrifugation and
decanted by using external magnet. The recovered particles were reused as a catalyst for the
next reaction.
Characterization
The morphology of each sample was characterized by transmission electron microscopy
(TEM) (Omega EM912 operated at 120 kV, Korea Basic Science Institute, and a Tecnai G2
F30 operated at 300 kV, KAIST) by placing a few drops of the corresponding colloidal
solution on carbonꢀcoated copper grids (200 mesh, F/C coated, Ted Pella Inc., Redding, CA,
USA). FEꢀscanning electron microscopy (SEM) (HITACHI_ S_4800, National Nanofab
Center, South Korea) was also used for analyses. Magnetization data were taken using a
superconducting quantum interference device (SQUID) (MPMSꢀ7, Quantum design). The Xꢀ
ray powder diffraction (XRD) patterns were recorded on a Rigaku D/MAXꢀRB (12 kW)
diffractometer. Xꢀray photoelectron spectroscopy (XPS) (Theta Probe, Thermo) was

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employed to measure the structural and chemical properties of the nanocomposites. The
1
tandem reaction products were analyzed by H nuclear magnetic resonance (NMR)
spectroscopy using a Varian Mercury Plus (300 MHz). Chemical shift values were recorded
as parts per million (ppm) relative to tetramethylsilane as an internal standard unless
otherwise indicated, and coupling constants are given in Hz. Mass spectra were obtained on
Shimadzu GC/MS QPꢀ2010 SE (EI) (Pusan National University).
Results
Characterization of the hybrid Cu-doped Pd-Fe
3 4
O catalyst
The Cuꢀdoped PdꢀFe nanocomposites were synthesized by facile decomposition of
3
O
4
Fe(CO) and reduction of Pd(OAc) and Cu(acac) in OAm and ODE. In the synthesis,
5
2
2
2
Pd(OAc) (0.114 g), OAm (10 mL), ODE (10 mL), and a controlled amount of NaOL were
mixed at 60 °C and then heated to 120 °C at a heating rate of 6 °C/min. The mixture was kept
at this temperature for 30 min. Fe(CO) (0.15 mL) was added under argon gas, and the
solution was heated to 160 °C at a heating rate of 4 °C/min and kept at 160 °C for 30 min.
Cu(acac) (32 mg) in OAm was added; the mixture was heated to 240 °C and kept at this
5
2
temperature for 30 min. The mixture was cooled to room temperature. The sample was
centrifuged in ethanol and hexane, giving a black precipitate. The products were analyzed
using inductively coupled plasmaꢀatomic emission spectroscopy (ICPꢀAES). The Pd/Fe/Cu
3 4
molar ratios in the Cuꢀdoped PdꢀFe O nanocomposites synthesized at 240 °C were
controlled at 30:63:7 to 36:55:9 by increasing the amount of NaOL from 0 to 0.5 g (Table 1).
Table 1. ICP molar ratio and BET surface area of hybrid nanocomposites.
BET surface area
Pd
Fe
Cu
2
(
m /g)
Pd-Fe O -0.3
42
30
36
36
58
63
54
55
ꢀ
7
7.30
28.2
31.2
34.1
3
4
Cu-doped Pd-Fe
Cu-doped Pd-Fe
Cu-doped Pd-Fe
3
3
3
O
O
O
4
4
4
-0
-0.3
-0.5
10
9

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Fig. 1 SEM images of (a) PdꢀFe O , (b) Cuꢀdoped PdꢀFe O ꢀ0, (c) Cuꢀdoped PdꢀFe O ꢀ0.3 and (d) Cuꢀdoped
3
4
3
4
3
4
3 4
PdꢀFe O ꢀ0.5 hybrid nanocomposites. The bars in the inset represent (b,c) 100 nm.
Fig. 1 shows scanning electron microscopy images of the PdꢀFe
3 4
O ꢀ0.3 and Cuꢀdoped Pdꢀ
Fe O ꢀn hybrid nanocomposites, synthesized using different amounts of NaOL; n denotes the
3
4
amount of NaOL (g) in the reaction mixture. As a control experiment, a PdꢀFe
3 4
O ꢀ0.3
nanocomposite was synthesized without addition of the Cu(acac) precursor (Fig. 1a). In the
2
absence of NaOL (Cuꢀdoped PdꢀFe
15 nm, were obtained (Fig. 1b).
Interestingly, when the NaOL capping agent was added, hybrid Cuꢀdoped PdꢀFe
nanocomposites showed sheetꢀassembled structure not spherical shape (Fig. 1c and d).
Transmission electron microscopy (TEM) images of the PdꢀFe ꢀ0.3 and Cuꢀdoped Pdꢀ
Fe O ꢀn nanocomposites are also shown in Fig. 2. The PdꢀFe O ꢀ0.3 nanocomposites did not
3 4
O ꢀ0), spherical structures, with an average diameter of
2
3
O
4
3
O
4
3
4
3
4
grow well, and consisted of seedꢀlike nanostructures (Fig. 2a). When the amount of NaOL
was increased (0.5 g), the morphology was slightly decomposed (Fig. 2c and d). Lowꢀ
3 4
resolution TEM images of the Cuꢀdoped PdꢀFe O ꢀn nanocomposites are shown in Fig. S1.

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Fig. 2 TEM images of (a) PdꢀFe
3 4 3 4 3 4
O , (b) Cuꢀdoped PdꢀFe O ꢀ0, (c) Cuꢀdoped PdꢀFe O ꢀ0.3 and (d) Cuꢀdoped
PdꢀFe ꢀ0.5 hybrid nanocomposites. The bars in the inset represent 20 nm.
3
O
4
Fig. 3 (a,b) XRD patterns of PdꢀFe
.3.
3 4 3 4 3 4
O and Cuꢀdoped PdꢀFe O and (c) HRꢀTEM image of Cuꢀdoped PdꢀFe O ꢀ
0
The crystal structures of the Cuꢀdoped PdꢀFe O ꢀn nanocomposites were determined using Xꢀ
3
4
ray diffraction (XRD; Fig. 3a). All the peaks in the XRD patterns can be assigned to the (111),
(
(
(
200), and (220) lattice planes of a faceꢀcentered cubic (fcc) Pd crystal structure, and the
220), (311), (422), (511), and (440) lattice planes of the cubic spinel structure of Fe
JCPDS No. 19ꢀ0629). The magnified image in Fig. 3b shows that the diffraction peak of Cuꢀ
3
O
4
doped Pd at around 40° shifted to a higher angle than that of Pd. This shifts indicates Pd

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1
6,17
lattice contraction caused by replacing fcc Pd atoms with Cu.
A highꢀresolution TEM
image of the Cuꢀdoped PdꢀFe
have wellꢀdefined structures and uniformly spaced lattice fringes, with fringe distances of
.225 nm for the Pd (111) plane and 0.25 nm for the Fe (311) plane, corresponding to fcc
Pd and Fe structures, respectively. The highꢀangle annular darkꢀfield scanning TEM
image and elemental mappings of Cu, Pd, and Fe also show that Cuꢀdoped Pd and Fe are
dispersed in all areas of the composite, confirming the hybrid Cuꢀdoped PdꢀFe structure
Fig. 4).
3 4 3 4
O ꢀ0.3 nanocomposite (Fig. 3c) shows that the Pd and Fe O
0
3 4
O
3
O
4
3
O
4
3
O
4
(
Fig. 4 (a) HAADFꢀSTEM image of Cuꢀdoped PdꢀFe
e) overlap.
3 4
O ꢀ0.3 and elemental mapping of (b) Cu, (c) Pd, (d) Fe and
(
Sheetꢀassembled structures are widely used for sensors, lithiumꢀion batteries, and
18
photocatalysts, because of their large specific surface areas. The Brunauer–Emmett–Teller
BET) surface areas of PdꢀFe ꢀ0.3, and Cuꢀdoped PdꢀFe ꢀ0, ꢀ0.3, and ꢀ0.5
nanocomposites were calculated to be 7.30, 28.2, 31.2, and 34.1 m g , respectively (Table 1).
These values are much higher than those for previously reported hollow and solid Fe
(
3
O
4
3 4
O
ꢀ1
2
3
O
4
2
ꢀ1
19
microspheres (12.27 and 5.43 m g ), because of the individual nanosheet structures. A high
amount of NaOL increased the BET surface areas of the Cuꢀdoped PdꢀFe nanocomposites,
3 4
O
demonstrating the effect of NaOL on the surface area and morphology. However, it is unclear
how NaOL capping agents affect the nanocomposite morphology during the growth step. To
clarify the synthetic mechanism, the reaction mixture was immediately transferred to an iceꢀ
bath to quench the synthesis when the temperature reached 160 °C. We assume that PdꢀFe
seed particles are first formed and then selfꢀaggregate before the nanosheets start to grow on
the surfaces of the PdꢀFe seed aggregates (Fig. 5). Fig. S2 shows TEM images of Cuꢀ
doped PdꢀFe ꢀ0.3 nanocomposites synthesized at different temperatures (160 and 200 °C).
Although the nanocomposite seeds were well synthesized, the temperatures were not high
enough for thermal decomposition of Fe(CO) and reduction of Pd(OAc) and Cu(acac)
resulting in poor growth, and PdꢀFe ꢀ0.3 seeds remained in the nanocomposites.
3 4
O
3
O
4
3
O
4
5
2
2
,
3
O
4

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Fig. 5 PdꢀFe O ꢀ0.3 seed aggregates (Reaction mixture was immediately transferred into iceꢀbath to quench
3
4
further synthesis when the temperature was reached to 160 °C.). The bars in the inset represent 5 nm.
Elemental analysis of Cuꢀdoped PdꢀFe
spectroscopy (XPS; Fig. 6). The wideꢀscan XPS spectra of Cuꢀdoped PdꢀFe
photoelectron lines at a binding energy of about 285.5 eV, attributed to C 1s (Fig. 6a). There
are two Cu 2p3/2 peaks, for Pd–Cu and Cu O, which can be clearly distinguished from those
of Cu. The binding energy of the Pd–Cu peak (931.8 eV) is lower than that that of Cu metal
3
O
4
ꢀ0.3 was performed using Xꢀray photoelectron
3
O
4
ꢀ0.3 shows
2
(
932.3 eV); these Cu peak shifts are indicative of the formation of PdꢀCu bimetallic particles
20
2
(Fig. 6b). The Cu 2p3/2 peak for Cu O (932.9 eV) is shifted slightly to higher binding energy,
21
by 0.6 eV, compared with that of Cu. In the Fe 2p spectrum (Fig. 6c), the Fe 2p1/2 and Fe
3/2 peaks are located at 710.8 and 724.3 eV, not at 709.9 and 723.5 eV as in the case of γꢀ
2
p
2
2
Fe
2
O
3
.
For Pd, the most intense peaks are observed at binding energies of around 335.1
(3d5/2) and 340.3 (3d3/2) eV, respectively, indicating metallic Pd characteristics (Fig. 6d). The
superconducting quantum interference device data show the magnetic curves as a function of
the applied field at 300 K (Fig. S3). The saturation magnetization value of the Cuꢀdoped Pdꢀ
ꢀ1
Fe
3 4
O ꢀ0.3 nanocomposite was 9.2 emu·g . Moreover, both the remanence and coercivity of
the nanocomposite were close to zero, indicating superparamagnetism.

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3 4
Fig. 6 The XPS spectra of Cuꢀdoped PdꢀFe O ꢀ0.3 nanocomposites.
Table 2 Tandem synthesis of 2ꢀphenybenzofurans
.
[
a]
Entry
Catalyst
Time
Base
Conv. (%)
(
h)
1
1
1
1
1
1
1
1
1
[
b]
1
2
3
4
5
6
7
8
9
Cuꢀdoped PdꢀFe
Cuꢀdoped PdꢀFe
Cuꢀdoped PdꢀFe
3
3
3
O
O
O
4
4
4
ꢀ0
ꢀ0
ꢀ0
NaOAc
NaOAc
NaOAc
LiOAc
36
[
c]
52
90
54
45
95
54
7
Cuꢀdoped PdꢀFe O ꢀ0
3
3
4
4
Cuꢀdoped PdꢀFe
O
ꢀ0
2 3
Cs CO
Cuꢀdoped PdꢀFe
Cuꢀdoped PdꢀFe
3
3
O
O
4
4
ꢀ0.3
ꢀ0.5
NaOAc
NaOAc
NaOAc
NaOAc
NaOAc
NaOAc
3 4
PdꢀFe O ꢀ0.3
[
d]
Cuꢀdoped PdꢀFe
Cuꢀdoped PdꢀFe
Cuꢀdoped PdꢀFe
3
3
3
O
O
O
4
4
4
ꢀ0.3
ꢀ0.3
ꢀ0.3
15
1
0
0.5
1
83
[
e]
11
46
3 4
Reaction condition: Cuꢀdoped PdꢀFe O catalyst (Cu base: 1.0 mol%, Pd base: 5.5 mol%), 2ꢀiodophenol (0.5 mmol),
[
a]
phenylpropiolic acid (0.6 mmol), base (1.0 mmol), solvent (5.0 ml) Reaction temperature: 130 °C. Determined by using
[
b,c]
[d]
GCꢀMS spectroscopy based on 2ꢀiodophenol.
DMF and NMP were used as solvent, respectively.
Reaction was
[
e]
conducted at 100 °C. 0.5 mol% of catalyst (Cu base) was used.
Tandem synthesis of 2-phenybenzofurans
The catalytic activity of Cuꢀdoped PdꢀFe
ꢀphenylbenzofurans from 2ꢀiodophenols with phenylpropiolic acids as a model reaction,
under various conditions (Table 2). First, the effect of the solvent was examined in the
presence of Cuꢀdoped PdꢀFe ꢀ0 at 130 °C for 1 h (Table 2, entries 1ꢀ3). The use of a more
3 4
O was investigated, using the tandem synthesis of
2
3
O
4
polar solvent (DMSO) led to an increase in the conversion, because of the superior solubility
of the reactant and catalyst in the reaction medium. The influences of bases such as NaOAc,
LiOAc, and Cs
2
CO
3
in the standard reaction were also studied (Table 2, entries 3ꢀ5). Better
CO . Among the Cuꢀ
conversion was achieved with NaOAc (90%) than with LiOAc and Cs
2
3

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doped PdꢀFe
Table 2, entries 3, 6, and 7). Although the Cuꢀdoped PdꢀFe
highest surface area, a low conversion was obtained because of destruction of the catalyst
structure. PdꢀFe ꢀ0.3 was used in a control experiment, and the catalytic activity was
3
O
4
ꢀn
catalysts, Cuꢀdoped PdꢀFe
3
O
4
ꢀ0.3 showed the highest catalytic activity
(
3 4
O
ꢀ0.5 nanocomposites had the
3
O
4
significantly lower without copper (Table 2, entry 8). Until now, multimetallic catalytic
tandem reactions have attracted much attention because they avoid the need for tedious
intermediate separation processes; this significantly lowers energy consumption and the cost
2
3
of the final products. Bimetallic catalytic systems also have higher catalytic activities than
singleꢀmetal catalytic systems, because of electron transfer across the metalꢀmetal interface.
The catalytic activity of Cuꢀdoped PdꢀFe
3 4 3 4
O ꢀn was therefore better than that of PdꢀFe O ꢀ0.3
because of the presence of copper, which is efficient in activating phenylpropiolic acid, and
2
ꢀ1
24
3 4
the low surface area of PdꢀFe O ꢀ0.3 (7.30 m g ; Table 2, entries 5 and 6). As expected, 15 %
conversion was achieved at low temperature (100 °C; Table 2, entries 6 and 9). We also tested
the effects of the amount of catalyst and reaction time. The conversions were lower (83% and
4
6%) when a short reaction time (0.5 h) and a smaller amount of catalyst (Cu base: 0.5 mol),
respectively, were used (Table 2, entries 10 and 11). The optimum reaction conditions were
found to be as follows: Cuꢀdoped PdꢀFe ꢀ0.3 (Cu base: 1.0 mol%, Pd base: 5.5 mol%);
solvent: DMSO (5.0 mL); temperature: 130 °C; and reaction time: 1 h (Table 2, entry 6). The
catalytic activity of Cuꢀdoped PdꢀFe ꢀ0.3, without any additives and ligands, was better
than those previously reported for a homogeneous CuI catalyst, in terms of the turnover
3
O
4
3
O
4
14
frequency (TOF). We also compared the catalytic activity with those heterogeneous
3,4,25,26
catalysts previously reported by our group (Fig. 7).
.3 showed the highest TOF under given conditions; this can be attributed to the dualꢀ
catalytic effect of Pd and Cu. After the tandem reaction, the Cuꢀdoped PdꢀFe ꢀ0.3 catalyst
could be totally separated using an external magnet, because of the superparamagnetic
3 4
Among them, Cuꢀdoped PdꢀFe O ꢀ
0
3
O
4
27
properties of Fe
and its initial high activity (>91%) was maintained, without any loss, during recycling (Fig.
S4). The morphology and crystal structure of the Cuꢀdoped PdꢀFe nanocomposites
3 4 3 4
O particles. The Cuꢀdoped PdꢀFe O ꢀ0.3 catalyst was recycled ten times
3 4
O
remained almost unchanged after the reaction (Fig. S5). In Pd and Cu leaching tests, the
filtered solution after the catalytic reaction was checked using ICPꢀAES; small amounts of Pd
and Cu, 1.62 and 9.00 ppm, respectively, were detected in the solution. We can conclude that
in the Cuꢀdoped PdꢀFe
3 4
O ꢀ0.3 nanocomposite, the Cuꢀdoped Pd has high catalytic activity,
and high stability was confirmed through recycling and leaching tests.

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Fig. 7 Comparison of catalytic activity with previous reported heterogeneous catalysts in our group. Reaction
condition: 2ꢀiodophenol (0.5 mmol), phenylpropiolic acid (0.6 mmol), NaOAc (1.0 mmol), DMSO (5.0 ml),
Catalyst (1.0 mol%), 130 °C, 1 h.
In conclusion, we successfully developed a oneꢀpot synthesis of Cuꢀdoped PdꢀFe
nanocomposites through controlled thermal decomposition of Fe(CO) and reduction of
Pd(OAc) and Cu(acac) . NaOL affected both the morphology and surface area of the hybrid
of the Cuꢀdoped PdꢀFe . The synthesized Cuꢀdoped PdꢀFe ꢀ0.3 hybrid catalyst showed
3 4
O hybrid
5
2
2
O
3 4
3 4
O
high catalytic activity in the tandem synthesis of 2ꢀphenylbenzofurans and was magnetically
recyclable. The same concept could be extended to other multimetallic NP systems, making it
possible to tune NP catalysis for many different chemical reactions.
Acknowledgment
This research was supported by Basic Science Research Proꢀgram through the National
Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planꢀ
ning (No.2013R1A1A1A05006634) and GCRCꢀSOP (No.2011ꢀ0030013). K. H. P thanks to
the TJ Park Junior Faculty Fellowship and LG Yonam Foundation. S. P thanks for the
support by KAERI and KBSI (E35800).
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