Facile Preparation of a Stable Fe3O4@LDH@NiB Magnetic Core-Shell Nanocomposite for Hydrogenation

Article abstract of DOI:10.1002/cjoc.201600759

A novel NiB deposited layered double hydroxide (LDH) coated ferroferric oxide (Fe₃O₄@LDH@NiB) magnetic core-shell nanocomposite was successfully fabricated by the combination of coprecipitation and impregnation-reduction. During the Fe₃O₄@LDH preparation, a facile template-free approach was employed to introduce the LDH shell, which was more efficient than the conventional method for the preparation of mesoporous materials that always needs to introduce and remove templates. The resulted Fe₃O₄@LDH has a relatively high surface area and abundant surface hydroxyl group, which can adsorb metal ions, making it favorable to disperse and stabilize the active Ni species, as demonstraed by TEM, XPS, FT-IR and BET characterizations. Therefore, it exhibited good activity in the selective hydrogenation of cinnamic acid to hydrocinnamic acid with the conversion and selectivity both approaching to 100%. Notably, the obtained Fe₃O₄@LDH@NiB can be easily separated by an external magnetic field and recycled eleven times without appreciable loss of its initial catalytic activity.

Full text of DOI:10.1002/cjoc.201600759

FULL PAPER
DOI: 10.1002/cjoc.201600759
Facile Preparation of a Stable Fe O @LDH@NiB Magnetic
3
4
Core-Shell Nanocomposite for Hydrogenation
Xuejia Gao, Libo Niu, Xianliang Qiao, Wenhui Feng, Yingying Cao, and Guoyi Bai*
Key Laboratory of Chemical Biology of Hebei Province, College of Chemistry and Environmental Science,
Hebei University, Baoding, Hebei 071002, China
3 4
A novel NiB deposited layered double hydroxide (LDH) coated ferroferric oxide (Fe O @LDH@NiB) magnet-
ic core-shell nanocomposite was successfully fabricated by the combination of coprecipitation and impregna-
tion-reduction. During the Fe O @LDH preparation, a facile template-free approach was employed to introduce the
3
4
LDH shell, which was more efficient than the conventional method for the preparation of mesoporous materials that
always needs to introduce and remove templates. The resulted Fe O @LDH has a relatively high surface area and
3
4
abundant surface hydroxyl group, which can adsorb metal ions, making it favorable to disperse and stabilize the ac-
tive Ni species, as demonstraed by TEM, XPS, FT-IR and BET characterizations. Therefore, it exhibited good activ-
ity in the selective hydrogenation of cinnamic acid to hydrocinnamic acid with the conversion and selectivity both
approaching to 100%. Notably, the obtained Fe O @LDH@NiB can be easily separated by an external magnetic
3
4
field and recycled eleven times without appreciable loss of its initial catalytic activity.
Keywords magnetic core-shell nanocomposite, layered double hydroxide, template-free approach, hydrogenation,
good stability
Introduction
the catalysts’ stabilities. Mesoporous materials are re-
garded as one of the best supports due to their large sur-
Catalytic hydrogenation of unsaturated substrates for
the manufacture of saturated or partially saturated
products has attracted much attention in recent years.
Particularly, the fabrication of highly active and stable
catalysts plays a key role for their industrial applications.
Presently, noble metal catalysts, especially Pd-, Pt-, Ru-
and Au-based catalysts, have achieved good activity and
face areas and suitable pores, which can facilitate the
[10-14]
dispersion of the active species.
Furthermore, the
efficient separation and recycling of the used catalysts is
another urgent problem to be solved. Accordingly,
mesoporous magnetic core-shell nanocomposites have
attracted special attention due to their large surface are-
as, big mesopore volumes and efficient separation char-
[1-5]
[
15,16]
[15]
stability.
Although some of them have been applied,
acteristics.
pared a Fe
For instance, Zhao et al.
have pre-
the high prices of noble metals have limited their further
applications, making it desirable to search for more
economical alternatives. Thus, non-noble metal catalysts,
especially NiB catalysts, have attracted much attention
due to their relatively high activity in hydrogenation and
3
4
O @SiO -Au@mSiO nanocomposite by the
2
2
combination of sol-gel process, interfacial deposition,
and surfactant-templating approach, which showed ex-
cellent performance in 4-nitrophenol reduction and sty-
rene epoxidation. However, the complicated preparation
processes of these magnetic mesoporous materials, in-
cluding the introduction and removal of templates, were
time-consuming and high cost. Moreover, to the best of
our knowledge, there was scant report on the prepara-
tion and application of stable non-noble metal magnetic
core-shell nanocomposites. Thus, there is still a need to
develop a more convenient way to prepare non-noble
metal nanocomposites with good stability.
[6-9]
low cost.
To achieve better results, several methods,
including additions of metals or polymers and applica-
tion of ultrasound, have been developed to improve the
[8]
activity of the pure NiB. For example, Chen et al. in-
vestigated the effect of Mo content on the catalytic per-
formance of NiB nanoclusters in the hydrogenation of
p-chloronitrobenzene and found that the addition of Mo
can markedly improve the activity and selectivity of
NiB catalyst. However, poor stability of the unsupported
NiB catalysts still limited their actual applications.
As is well known, immobilization of the active spe-
cies on suitable supports is an effective way to improve
Recently, layered double hydroxide (LDH) has been
widely applied in the field of environment, medical sci-
ence, electrochemistry and catalysis due to its structural
characteristics, such as cation-diversity of brucite-like
*
E-mail: baiguoyi@hotmail.com; Tel.: 0086-0312-5079359, Fax: 0086-0312-5937102
Received November 4, 2016; accepted January 16, 2017; published online XXXX, 2017.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201600759 or from the author.
Chin. J. Chem. 2017, XX, 1—X8
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1

Gao et al.
FULL PAPER
layers, anion exchange by interlayers, and adjustable
2 3
gent Co., Ltd., China. Sodium carbonate (Na CO ) was
purchased from Tianjin Fengchuan Chemical Reagent
Co., Ltd., China. Ultrapure Ar (99.999%) and 5 vol%
[
17-22]
[23]
surface basicity.
reported a novel Fe
site, which exhibited good activity in the oxidation of
-phenylethanol and can be efficiently recycled five
For example, Zhang et al. have
3
4
O @MgAl-LDH@Au nanocompo-
H
2
/N
Preparation of the nanocomposites
Fe @LDH was prepared by a coprecipitation
2
were supplied by Baoding Zhuoda Gas Co.Ltd.
1
times. They attributed this to the synergistic effect be-
tween the MgAl-LDH and the Au active species. How-
ever, there was a few reports on the fabrication of
non-noble metal core-shell nanocomposites using LDH.
Very recently, we have designed and prepared two novel
layered double hydroxide/layered double oxide (LDO)
coated nickel-based core-shell nanocomposites, which
exhibited good catalytic performances in the selective
hydrogenation of benzonitrile to afford N-benzylidene-
3
O
4
[
23,31-33]
method,
of Fe
under ultrasound for 25 min. After that, Na
as shown in Scheme 1. Typically, 0.60 g
was dispersed in deionized water (160 mL)
CO (0.40 g)
3
O
4
2
3
was added to this solution and stirred for 10 min to form
suspension. An aqueous solution (76.8 mL) containing
Mg(NO ) •6H O (1.00 g) and Al(NO ) •9H O (0.72 g)
3 2 2 3 3 2
was then dropwise added to this suspension under vig-
orous stirring. The pH value of the reaction mixture was
controlled to be about 10 by the addition of 1.0 mol/L
NaOH. After stirring at room temperature for 1 h, the
precipitate was collected by magnet, dispersed in de-
ionized water (160 mL) again, and then stirred for an-
other 1 h. The magnetic collection and dispersion was
repeated once. Finally, it was washed with deionized
water three times, and then dried at 333 K for 6 h to
[24]
benzylamine and benzylamine, respectively.
Water
was found to be effective to tune their structures and
acid-base properties, accounting for the interesting
changing-over on selectivity. However, their stabilities
and separation efficiency were still not good enough for
actual applications.
[24-27]
As a continuation of our previous work,
herein designed and prepared a novel NiB deposited
LDH coated ferroferric oxide (Fe @LDH@NiB)
we
O
4
afford Fe
calcined at 773 K under Ar gas atmosphere for 4 h with
a rate of 5 K/min to form Fe @LDO.
Fe @LDH@NiB was prepared by an impregna-
tion-reduction method. In a typical run, 0.25 g of
Fe @LDH was impregnated in an aqueous solution
of NiCl •6H O (0.18 g) and water (0.45 mL). The mix-
3 4 3 4
O @LDH. The obtained Fe O @LDH was
3
magnetic core-shell nanocomposite by the combination
of coprecipitation and impregnation-reduction. It has a
core-shell structure with ferroferric oxide as core, LDH
as the inner shell and NiB as the outer shell. This tem-
plate-free method of coating the LDH shell directly on
3
O
4
3
O
4
3
O
4
the surface of the Fe
3
O
4
core avoided the introduction
2
2
and removal of templates, which markedly improved the
efficiency of catalyst preparation. Notably, the coated
LDH was found to have the ability to disperse and sta-
bilize the Ni ions by their surface hydroxyl group and
ture was first treated under ultrasound for 10 min and
then dried at 353 K for 4 h. After that, the precursor was
reduced by adding 3.0 mL of 1.0 mol/L aqueous KBH
4
containing 0.2 mol/L NaOH dropwise in an ice water
bath under ultrasound. When the reduction was com-
plete, the precipitate was washed with deionized water
several times until neutral, followed by washing with
absolute ethanol three times to remove the residual wa-
ter. Finally, the resulted Fe O @LDH@NiB nanocom-
[28-30]
mesoporous structure,
accounting for the well dis-
persed and stable active Ni species. This nanocomposite
showed good catalytic performance in the hydrogena-
tion of cinnamic acid with the conversion of cinnamic
acid and the selectivity for hydrocinnamic acid to both
approach 100% under relatively mild reaction condi-
tions. Meanwhile, it can be easily separated from the
reaction mixture by an external magnetic field and recy-
cled eleven times without appreciable loss of initial ac-
tivity, making it an attractive candidate for actual appli-
cations.
3
4
posite was kept under absolute ethanol for further use.
Furthermore, Fe O @LDO@NiB and Fe O @NiB were
3
4
3
4
also prepared by an impregnation-reduction method, the
same as that of Fe O @LDH@NiB. NiB was prepared
3
4
in a similar manner to the protocol reported in our pre-
[
34]
vious work.
Catalyst characterization
Experimental
The X-ray diffraction (XRD) patterns were obtained
on a Bruker D8-ADVANCE X-ray diffractometer using
a Cu Ka radiation source. Inductively coupled plasma
analysis (ICP) was carried out using a Varian
Vista-MPX spectrometer. The Brunauer-Emmett-Teller
(BET) surface area was tested using a Micromeritics
Tristar II 3020 surface area and pore analyzer. The Fou-
rier transform infrared spectra (FT-IR) were recorded on
a Bruker VERTEX70 Fourier transform spectrophotom-
Materials
Unless otherwise stated, all chemicals were analyti-
cal grade and used as received. Ferroferric oxide (Fe O )
3 4
nanoparticles and tert-butyl alcohol were purchased
from Aladdin Industrial Inc., Shanghai, China. Magne-
sium nitrate hexahydrate [Mg(NO
nitrate nonahydrate [Al(NO •9H
borohydride (KBH ) were purchased from Tianjin
Fuchen Chemical Reagent Co., Ltd., China. Nickel
chloride hexahydrate (NiCl •6H O) and cinnamic acid
were purchased from Tianjin Guangfu Chemical Rea-
3
)
2
2
•6H
2
O], aluminium
3
)
3
O], and potassium
4
eter using KBr pellets. H
ture-programmed desorption of hydrogen (H
were carried out on a TP-5000 instrument equipped with
2
-chemisorption and tempera-
-TPD)
2
2
2
2
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Chin. J. Chem. 2017, XX, 1—8

Fe
3
O
4
@LDH@NiB Magnetic Core-Shell Nanocomposite for Hydrogenation
@LDH@NiB
Scheme 1 Preparation of Fe
3
O
4
a thermal conductivity detector supplied by Xian quan
Co. Ltd. Transmission electron microscopy (TEM) was
performed using a FEI Tecnai G F20 S-TWIN micro-
ty of these peaks was ascribed to the low crystallinity of
LDH in these nanocomposites, compared to that of
Fe O (Figure S1). Whereas, these characteristic peaks
3 4
2
scope and the particle size distributions were calculated
by a Nano Measurer software based on the TEM results.
Magnetization curves were obtained on a LDJ9600-1
superconducting quantum interference device at room
temperature. The X-ray photoelectron spectroscopy
of LDH disappeared (Figure 1d) after calcination at 773
K under Ar gas atmosphere for 4 h, suggesting the
transformation of LDH to amorphous metal oxides, such
[
36]
as MgO and Al
Considering no peaks related to NiB can be detected
in the XRD curve of Fe @LDH@NiB, XPS was then
performed to confirm the existence of Ni and B. As can
be seen, both Ni and B exist on the surface of Fe
2 3
O .
(XPS) was recorded on a PHI 1600 spectrometer with
3 4
O
monochromatic Mg Kα as the excitation source.
3
4
O @
Catalyst activity test
LDH@NiB (Figure S2a). The characteristic peaks of Ni
2p centered at 852.5 and 855.6 eV can be assigned to
metallic and oxidized Ni, and the peaks of B 1s at 187.9
and 192.0 eV can be assigned to elemental and oxidized
Catalytic performances of the obtained nanocompo-
sites were investigated in the selective hydrogenation of
cinnamic acid. Typically, cinnamic acid (2.0 g, 13.5
mmol), catalyst (0.15 g) and tert-butyl alcohol (40 mL)
were added into a 100 mL Parr 4598HPHT stainless
steel autoclave equipped with a mechanical stirrer and
an electrical heating system. The reaction system was
[37]
B, respectively (Figure 2).
Notably, the binding en-
ergy of the metallic Ni is 0.6 eV lower than that of pure
Ni (853.1 eV) and the binding energy of the elemental B
in Fe O @LDH@NiB is 0.8 eV higher than that of pure
3
4
first filled with H
evacuation, to displace the residual air, then it was
pressured with H to 2.0 MPa and heated to the required
2
to 1.0 MPa three times, followed by
B (187.1 eV), indicating the electron transfer from B to
[
38,39]
Ni,
suggesting the formation of NiB alloys on the
[
37-39]
2
surface of Fe O @LDH.
3
4
temperature. On reaching the required temperature, the
reaction was started by stirring the reaction mixture
vigorously and proceeded for 0.5 h. Selective hydro-
genation of other unsaturated substrates was carried out
using the same reaction conditions as cinnamic acid
unless specially noted. When the reaction was complete,
the reaction mixtures were cooled to room temperature
and separated by an external magnetic field. The reac-
tion mixtures were analyzed by an Agilent 7820A gas
chromatography (GC) and the products structures were
identified using gas chromatography-mass spectroscopy
Ni contents, BET surface areas, pore volumes, and
H -chemisorptions of these nanocomposites and NiB
were measured and the results are summarized in Table
2
1. It was found that the Ni contents of Fe O @LDH@
3
4
NiB and Fe O @LDO@NiB were similar, both a little
3
4
lower than that of Fe O @NiB. The BET surface area
3
4
2
1
and pore volume of Fe O @LDH was 111 m •g and
0.39 cm •g , respectively. In contrast, the BET surface
area and pore volume of Fe O @LDO decreased to 49
m •g and 0.21 cm •g , probably due to the structural
collapse during calcination.
Considering that the BET surface area and pore
3
4
3
1
3
4
2
1
3
1
[
40]
(
GC-MS) on an Agilent 5977A spectrometer.
2
1
3 4
volume of Fe O @LDH@NiB decreased to 61 m •g
and 0.16 cm •g , we speculated that NiB has dispersed
3
1
Results and Discussion
on the outer surface and occupied some pores of
Characterization of catalysts
[41]
Fe
3
O
4
@LDH.
3 4
Even so, these values of Fe O @
Figure 1 shows the XRD patterns of Fe
3
O
4
and the
LDH@NiB were still much higher than those of
Fe @LDO@NiB, Fe @NiB and NiB, ascribed to
the presence of LDH. Additionally, the H -chemisorp-
tion value also showed the same tendency. Fe
LDH@NiB exhibited the largest H -chemisorption val-
ue among all the catalysts, suggesting it has the largest
number of active species and the best catalytic ability.
Thus, we can conclude that the existence of LDH favors
the dispersion of the active NiB species on its surface
prepared nanocomposites. As can be seen, all nano-
composites exhibited characteristic diffraction peaks at
about 18.3°, 30.3°, 35.7°, 43.3°, 53.6°, 57.2°, 62.8° and
3
O
4
3 4
O
2
3
4
O @
7
4.2°, just like those of the pure Fe
the magnetic Fe cores were well retained after the
LDH or LDO coating.
1.4° and 23.2° in Fe
NiB can be assigned to the characteristic peaks of
3
O
4
, indicating that
2
3
O
4
[
35]
Furthermore, the peaks at
@LDH and Fe @LDH@
1
3
O
4
3 4
O
[
23]
LDH,
Fe
demonstrating the existence of LDH in
@LDH and Fe @LDH@NiB. The low intensi-
2
and then accounts for the high H -chemisorption ability
3
O
4
3
O
4
of Fe @LDH@NiB. Furthermore, Figure 3
3 4
O
Chin. J. Chem. 2017, XX, 1—8
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3

Gao et al.
FULL PAPER
characteristic absorption peaks of carbonate, respective-
1
ly. Meanwhile, two peaks at 3428 and 1633 cm are
also observed, which were attributed to the hydroxyl
stretching mode arising from the metal hydroxyl group
of hydrogen-bonded interlayer water and the hydroxyl
[
43]
deformation mode of water. Furthermore, the charac-
1
teristic peak at 582 cm was assigned to Fe－O in the
Fe phase, demonstrating the existence of the Fe
core. In contrast, nearly no adsorption peak was ob-
3
O
4
3 4
O
[
23]
1
served at 1364 cm and the absorption peak at 3428

1
cm was markedly reduced for Fe
b), indicating the removal of the interlayer anion, sur-
face hydroxyl group and water of Fe @LDH during
The existence of interlayer anions
and surface hydroxyl group in Fe @LDH is benefit to
the binding of metal ions, and thereby promotes the
3 4
O @LDO (Figure
4
3
O
4
[40,44]
Figure 1 XRD patterns of (a) Fe O , (b) Fe O @LDH, (c)
the calcination.
3
4
3
4
Fe
3
O
4
@LDH@NiB, (d) Fe
3
O
4
@LDO, and (e) Fe
3
O
4
@LDO@
3 4
O
NiB.
[30]
dispersion and immobilization of the active Ni.
Therefore, due to the lack of interlayer anions and sur-
face hydroxyl group in Fe @LDO, it needs a lot of
exhibits the nitrogen adsorption-desorption isotherm of
Fe
Fe
3
O
O
4
@LDH, Fe
3
O
4
@LDO, Fe
3
O
4
@LDH@NiB and
3 4
O
@LDO@NiB. As can be seen, all samples exhibit
anions to rebuild their LDH structure. Thus, during the
introduction of the Ni precursor and the reduction of the
3
4
typical IV isotherm with H3-type hysteresis loops (p/p
0
＞
0.4), indicating the presence of mesopores in these
precursor using KBH as the reducing agent, it has a
tendency to incorporate neighboring anions. This is also
4
[
42]
nanocomposites.
FT-IR spectra of Fe
@LDH@NiB, Fe
NiB are presented in Figure 4. In the FT-IR spectra of
Fe @LDH and Fe @LDH@NiB, the strong ad-
sorption peaks at 1364 and 677 cm were assigned to
3
O
4
@LDH, Fe
3
O
4
@LDO,
the reason that LDH partially recovered its structure
after reduction (Figure 4d). Accordingly, we speculated
that the improvement on the ability to adsorb anions
would weaken the force between metal and support,
resulting in a negative impact on the adsorption and
dispersion of metal ions.
Fe
3
O
4
3 4 3 4
O @LDO@NiB and Fe O @
3
O
4
3 4
O
1
2

the characteristic absorption peaks of CO
3
and the
Table 1 Structural properties and catalytic performances of the nanocomposites and NiB samples
a
2
1
3
1
3
1
b
Ni content /wt%
Surface area/(m •g ) Pore volume/(cm •g ) H
2
-chemisorption/(cm •g ) Conversion /%
Fe
Fe
Fe
3
3
3
O
O
O
4
4
4
@LDH
@LDO
－
－
111
49
61
42
13
16
0.39
0.21
0.16
0.08
0.03
0.05
－
－
－
－
@LDH@NiB 12.2
0.212
0.057
0.013
0.070
96.7
13.4
2.1
Fe O @LDO@NiB 11.6
3
4
Fe O @NiB
14.2
3
4
c
NiB
79.6
45.5
a
b
Based on ICP results. Reaction conditions: cinnamic acid (2.0 g), catalyst (0.15 g), tert-butanol (40 mL), 383 K, initial p(H
2
)＝2.0 MPa,
c
and reaction time 0.5 h. Catalyst amount (0.023 g).
3 4
Figure 2 XPS spectra of Ni and B in the Fe O @LDH@NiB (a) before and (b) after being used 11 times.
4
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3 4
Fe O @LDH@NiB Magnetic Core-Shell Nanocomposite for Hydrogenation
Figure 3
LDH, (b) Fe
LDO@NiB.
N
2
adsorption-desorption isotherms of (a) Fe
@LDO, (c) Fe @LDH@NiB, and (d) Fe
3
3
O
O
4
@
@
Figure 5
H
2
-TPD profiles of (a) Fe
3 4
O @LDH@NiB, (b)
3
O
4
O
3 4
4
Fe @LDO@NiB, (c) Fe O
3
O
4
3 4
@NiB, and (d) NiB.
3 4
tion of the Ni species due to the magnetism of Fe O ,
although it was still a little larger than that of the pure
NiB.
The morphology of the fresh Fe O @LDH@NiB
3 4
was recorded by TEM and shown in Figure 6, together
with the size distribution of the Ni species. As can be
3 4
seen, Fe O @LDH@NiB exhibits a clear core-shell
structure with a magnetite core, an LDH shell in the
middle, and some Ni species outside (Figure 6a). Obvi-
ously, LDH has a layered structure with rough surface
and irregular edge, which provides abundant accessible
edge and junction sites to support and disperse Ni spe-
cies. As can be seen from the size distributions of the Ni
species (Figure 6b), the particle sizes of the Ni species
are mainly in the range of 8－13 nm with an average
size of 10 nm.
Figure 4 FT-IR spectra of (a) Fe
3 4 3 4
O @LDH, (b) Fe O @LDO,
(
c) Fe O @LDH@NiB, (d) Fe O @LDO@NiB and (e)
3
4
3
4
The room temperature hysteresis loops of Fe
@LDH@NiB and NiB are shown in Figure 7. As
can be seen, the saturation magnetization (M ) value of
@LDH@NiB is 43.4 emu•g at an applied field
of 20000 Oe with no remanence or hysteresis loops be-
3 4
O ,
Fe O @NiB.
3
4
Fe
Fe
3 4
O
Generally, the areas of H
be correlated with the amounts of the active species.
Thus, it was usually used to estimate the active sites for
heterogeneous catalysts. As for this work, it was obvi-
ous that Fe
2
-TPD peaks are believed to
s
[
45]
1
3 4
O
[
49]
ing detectable, indicating its superparamagnetism.
1
O
3 4
@LDH@NiB exhibited two desorption
Considering that the M
very low and can nearly be ignored, the magnetism of
Fe @LDH@NiB is mainly from Fe (93.1
3 4
emu•g ). Notably, the coating by LDH endows Fe O @
s
value of NiB (0.5 emu•g ）is
peaks at about 473 and 574 K and their areas were much
larger than other catalysts (Figure 5). The main peak at
3
O
4
3 4
O
1
4
73 K was attributed to hydrogen chemisorbed on the
[
46]
surface of the highly-dispersed Ni species, which can
serve as capture traps for surface hydrogen diffusion,
resulting in the decrease of the activation energy of hy-
drogen dissociation and then the improvement on the
LDH@NiB appropriate magnetization, accounting for
its efficient separation from the reaction mixture and
also avoiding the undesired aggregation.
[47,48]
Catalytic performance
catalyst activity.
Whereas, the small peak at higher
Catalytic performances of the prepared nanocompo-
sites were investigated in the selective hydrogenation of
cinnamic acid, and the results are listed in Table 1. As
temperature (574 K) was attributed to the hydrogen ad-
[
45]
sorbed on bulk or poorly-dispersed Ni species. Fur-
thermore, the TPD profile of Fe @LDO@NiB also
presents two H -TPD peaks at about 464 and 586 K
3
O
4
3 4
expected, Fe O @LDH@NiB exhibited the best cata-
2
with the higher temperature peak as the main one, but
the intensities of these peaks markedly decreased. This
was attributed to the hydrogen adsorbed on bulk or
poorly dispersed Ni species due to the poor dispersive
lytic performances among the catalysts studied with
96.7% conversion of cinnamic acid and 100% selectivi-
ty for hydrocinnamic acid. In contrast, the conversions
of cinnamic acid were only 13.4% and 2.1% over
effect of LDO. In the case of Fe
only one small desorption peak observed at relatively
higher temperature, which was ascribed to the aggrega-
3
O
4
@NiB, there was
Fe
than that of pure NiB (45.5% conversion). The excellent
catalytic activity of Fe @LDH@NiB was attributed
3 4 3 4
O @LDO@NiB and Fe O @NiB, even much lower
3
O
4
Chin. J. Chem. 2017, XX, 1—8
© 2017 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
5

Gao et al.
FULL PAPER
Figure 6 TEM images of Fe
3
O
4
@LDH@NiB (a) before and (c) after being used 11 times and the corresponding size distributions of the
Ni species (b, d).
shell were helpful to absorb metal ions in solution and
promote the dispersion and immobilization of the active
species. This was beneficial to the good catalytic per-
formance of this catalyst. In contrast, LDO cannot ef-
fectively disperse the active Ni species due to the ab-
sence of interlayer anions and surface hydroxyl group as
well as its low surface area, resulting in the poor activity
of Fe O @LDO@NiB. As for Fe O @NiB, its poor
3 4 3 4
catalytic performance was mainly attributed to the se-
vere aggregation of the active Ni species caused by the
3 4
strong magnetism of Fe O .
Considering that good stability is a key feature for an
industrial catalyst, the stability of Fe O @LDH@NiB
3
4
3 4
Figure 7 Magnetization curves of (a) NiB, (b) Fe O @LDH@
was then investigated in the hydrogenation of cinnamic
acid and the results are shown in Figure 8. Notably,
Fe O @LDH@NiB exhibited excellent stability in the
NiB, and (c) Fe O at room temperature.
3
4
3
4
hydrogenation of cinnamic acid. It can be easily sepa-
rated by magnet and recycled eleven times without ap-
preciable loss of its initial catalytic activity, much better
than the Fe O @nSiO @mSiO @NiCoB nanocompo-
3
4
2
2
[
50]
site reported in our previous work and ascribed to the
confinement effect of LDH. In contrast, the conversion
of cinnamic acid markedly dropped from 13.4% to 3.3%
only in the second run over Fe O @LDO@NiB, further
3
4
demonstrating the superior stabilizing effect of LDH for
the Ni species in Fe @LDH@NiB.
Some characterizations were then carried out to clar-
ify the reasons for the good stability of Fe @LDH@
3
O
4
Figure 8 Stability of Fe O @LDH@NiB. Reaction conditions:
3
4
2
.0 g cinnamic acid, 0.15 g catalyst, 40 mL tert-butyl alcohol,
3 4
O
temperature 383 K, initial p(H )＝2 MPa, reaction time 0.5 h.
NiB. ICP analysis revealed that the amount of Ni in the
used catalyst was 11.6%, very similar to that of the fresh
catalyst (12.2%), indicating the presence of LDH can
efficiently suppress the leaching of the active Ni species
during the recycling, and in turn accounting for its good
stability. XPS spectra of the fresh and used Fe O @
2
to the existence of LDH. On the one hand, the relatively
large specific surface area favors the dispersion of the
active NiB species on the Fe O @LDH nanocomposite,
3 4
resulting in good activity of the catalyst. On the other
hand, abundant hydroxyl groups on the surface of LDH
3
4
LDH@NiB indicated the valence state of nickel kept
6
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© 2017 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2017, XX, 1—8

3 4
Fe O @LDH@NiB Magnetic Core-Shell Nanocomposite for Hydrogenation
Table 2 Hydrogenation of various unsaturated substrates over
unsaturated substrates.
Fe O @LDH@NiB
3
4
Conclusions
Time/h Substrate
Main product
Con./%Sel./%
96.7 100
3 4
In conclusion, a novel Fe O @LDH@NiB magnetic
O
a
core-shell nickel-based nanocomposite was successfully
prepared by the combination of coprecipitation and im-
pregnation-reduction. The LDH layer was introduced
via a facile template-free approach and exhibited good
performances in dispersing and stabilizing the active Ni
species due to its surface hydroxyl group and mesopo-
rous structure. This nanocomposite showed good per-
formances in the selective hydrogenation of cinnamic
acid and other unsaturated substrates. Notably, it can be
easily separated for recycling by an external magnetic
field and recycled eleven times without appreciable loss
of its initial catalytic activity, mainly due to the con-
finement effect of LDH. Thus, this method for the prep-
aration of magnetic core-shell nanocomposite possesses
the advantages of low cost, high efficiency and excellent
catalytic performances, making it an attractive candidate
for actual applications.
0
.5
OH
1
0
.0
.5
91.5 100
99.8 99.4
0
1
4
.5
.5
.5
99.4 99.0
94.9 100
97.3 96.6
b
NO2
Acknowledgement
N c
C
2
.0
100
47.8
This work was supported by the National Natural
Science Foundation of China (Nos. 21376060 and
2
1676068) and the Natural Science Foundation of Hebei
Reaction conditions: 13.5 mmol substrate, 0.15 g catalyst, 40 mL
a
Province (No. B2014201024).
ethanol, temperature 383 K, initial p(H )＝2 MPa. 40 mL
2
b
c
tert-butyl alcohol. Initial p(H )＝3 MPa. 40 mL methanol.
2
References
nearly unchanged during the reaction (Figure 2). Fur-
thermore, TEM image of the used catalyst (Figure 6c
and 6d) demonstrated that the morphology and disper-
sion of the active Ni species kept nearly unchanged after
the recycling. Thus, the LDH shell was proven to be
effective to prevent the leaching and aggregation of the
active Ni species during the reaction, accounting for the
[
1] Shokouhimehr, M.; Shin, K. Y.; Lee, J. S.; Hackett, M. J.; Jun, S. W.;
Oh, M. H.; Jang, J.; Hyeon, T. J. Mater. Chem. A 2014, 2, 7593.
2] Chen, Y.; Yang, J.; Yang, Y.; Peng, Z. Y.; Li, J. H.; Mei, T.; Wang, J.
Y.; Hao, M.; Chen, Y. L.; Xiong, W. L.; Zhang, L.; Wang, X. B.
Chem. Commun. 2015, 51, 10490.
[
[3] Xu, X.; Tang, M. H.; Li, M. M.; Li, H. R.; Wang, Y. ACS Catal.
014, 4, 3132.
2
[
[
4] Zou, L. Y.; Cui, Y. Y.; Dai, W. L. Chin. J. Chem. 2014, 32, 257.
5] Deng, D. S.; Han, J. Q.; Zhu, X.; Xu, X.; Gong, Y. T.; Wang, Y. Chin.
Chem. Lett. 2015, 26, 277.
3 4
excellent stability of Fe O @LDH@NiB.
To evaluate the versatility of this nanocomposite, a
series of unsaturated substrates was investigated and the
results are shown in Table 2. It is apparent that
[
[
6] Lewandowski, M. Appl. Catal. B: Environ. 2015, 168, 322.
7] Wei, S. Q.; Cui, H. Y.; Wang, J. H.; Zhuo, S. P.; Yi, W. M.; Wang, L.
H.; Li, Z. H. Particuology 2011, 9, 69.
3 4
Fe O @LDH@NiB exhibited good catalytic activities
for all substrates, especially for cinnamic alcohol, sty-
rene and α-methyl styrene with the conversion and se-
lectivity both reaching above 90.0% within 1.0 h. In the
case of nitrobenzene, aniline was detected to be the
main product with the conversion and selectivity being
[8] Su, J. F.; Zhao, B.; Chen, Y. W. Ind. Eng. Chem. Res. 2011, 50, 1580.
9] Liaw, B. J.; Chen, C. H.; Chen, Y. Z. Chem. Eng. J. 2010, 157, 140.
10] Zhong, L.; Chokkalingam, A.; Cha, W. S.; Lakhi, K. S.; Su, X. Y.;
Lawrence, G.; Vinu, A. Catal. Today 2015, 243, 195.
11] Lin, X. J.; Zhong, A. Z.; Sun, Y. B.; Zhang, X.; Song, W. G.; Lu, R.
W.; Cao, A. M.; Wan, L. J. Chem. Commun. 2015, 51, 7482.
12] Ghorbani-Vaghei, R.; Hemmati, S.; Veisi, H. J. Mol. Catal. A: Chem.
2014, 393, 240.
[
[
[
[
9
7.3% and 96.6%, respectively. The main by-products
were N-ethylaniline and N-ethylidenebenzenamine,
which resulted from the reaction between nitrobenzene
and ethyl alcohol. Moreover, a high conversion was
achieved in the hydrogenation of benzonitrile. Benzyl-
amine was obtained as the main product with
N-benzylidenebenzylamine and dibenzylamine being
detected as the main by-products. The above results
[13] Zhu, F. X.; Li, H. X. Chin. J. Chem. 2014, 32, 1072.
[
[
[
14] Li, J.; Qian, L. P.; Hu, L. Y.; Yue, B.; He, H. Y. Chin. Chem. Lett.
016, 27, 1004.
2
15] Deng, Y. H.; Cai, Y.; Sun, Z. K.; Liu, J.; Liu, C.; Wei, J.; Li, W.; Liu,
C.; Wang, Y.; Zhao, D. Y. J. Am. Chem. Soc. 2010, 132, 8466.
16] Hu, W. T.; Liu, B. C.; Wang, Q.; Liu, Y.; Liu, Y. X.; Jing, P.; Yu, S.
L.; Liu, L. X; Zhang, J. Chem. Commun. 2013, 49, 7596.
demonstrated that Fe
catalytic performances in the hydrogenation of various
3
O
4
@LDH@NiB possesses good
[17] Rives, V. Layered Double Hydroxides: Present and Future, Nova
Science Publishers, New York, 2001.
Chin. J. Chem. 2017, XX, 1—8
© 2017 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
7

Gao et al.
FULL PAPER
[
[
18] Zumreoglu-Karan, B.; Ay, A. N. Chem. Pap. 2012, 66, 1.
Eng. Chem. Res. 2013, 52, 2266.
[35] Wang, H. G.; Sun, L.; Li, Y. P.; Fei, X. L.; Sun, M. D.; Zhang, C. Q.;
Li, Y. X.; Yang, Q. B. Langmuir 2011, 27, 11609.
[36] Li, L.; Feng, Y. J.; Li, Y. S.; Zhao, W. R.; Shi, J. L. Angew. Chem.,
Int. Ed. 2009, 48, 5888.
[37] Bai, G. Y.; Niu, L. B.; Qiu, M. D.; He, F.; Fan, X. X.; Dou, H. Y.;
Zhang, X. F. Catal. Commun. 2010, 12, 212.
[38] Li, H.; Li, H. X.; Dai, W. L.; Wang, W. J.; Fang, Z. G.; Deng, J. F.
Appl. Surf. Sci. 1999, 152, 25.
[39] Wei, W.; Zhao, Y.; Peng, S. C.; Zhang, H. Y.; Bian, Y. P.; Li, H. X.;
LI, H. J. Mater. Chem. A 2014, 2, 19253.
[40] Tang, S.; Chia, G. H.; Lee, H. K. J. Colloid Interface Sci. 2015, 437,
316.
[41] Wang, S. L.; Wei, W.; Zhao, Y.; Li, H. X.; Li, H. Catal. Today 2015,
258, 327.
[42] Li, W.; Wu, P. X.; Yang, S. S.; Zhu, Y. J.; Kang, C. X.; Tran, L. T.;
Zeng, B. L. RSC Adv. 2015, 5, 8859.
[43] Zhang, H.; Zhang, G. Y.; Bi, X.; Chen, X. T. J. Mater. Chem. A 2013,
1, 5934.
[44] Wang, J.; Liu, Q.; Zhang, G. C.; Li, Z. S.; Yang, P. P.; Jing, X. Y.;
Zhang, M. L.; Liu, T. F.; Jiang, Z. H. Solid State Sci. 2009, 11, 1597.
[45] Lin, W. W.; Cheng, H. Y.; He, L. M.; Yu, Y. C.; Zhao, F. Y. J. Catal.
2013, 303, 110.
[46] Liu, J.; Li, C. M.; Wang, F.; He, S.; Chen, H.; Zhao, Y. F.; Wei, M.;
Evans, D. G.; Duan, X. Catal. Sci. Technol. 2013, 3, 2627.
[47] Helden, P.; Berg, J. A.; Weststrate, C. J. ACS Catal. 2012, 2, 1097.
[48] Weng, M. H.; Chen, H. T.; Wang, Y. C.; Ju, S. P.; Chang, J. G.; Lin,
M. C. Langmuir 2012, 28, 5596.
19] Ay, A. N.; Abramova, N. V.; Konuk, D.; Lependina, O. L.; Sokolov,
V. I.; Zümreoglu-Karan, B. Inorg. Chem. Commun. 2013, 27, 64.
20] Xu, C. H.; Zheng, L. K.; Liu, J. Y.; Huang, Z. Y. Chin. J. Chem.
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
2
011, 29, 691.
21] Shun, N.; Atsushi, T.; Kohki, E. Bull. Chem. Soc. Japan 2010, 83,
46.
8
22] Polshettiwar, V.; Luque, R.; Fihri, A.; Zhu, H.; Bouhrara, M.; Basset,
J. M. Chem. Rev. 2011, 111, 3036.
23] Mi, F.; Chen, X. T.; Ma, Y. W.; Yin, S. T.; Yuan, F. L.; Zhang, H.
Chem. Commun. 2011, 47, 12804.
24] Cao, Y. Y.; Niu, L. B.; Wen, X.; Feng, W. H.; Huo, L.; Bai, G. Y. J.
Catal. 2016, 339, 9.
25] Bai, G. Y.; Shi, L. J.; Zhao, Z.; Wang, Y. L.; Qiu, M. D.; Dong, H. X.
Mater. Lett. 2013, 96, 93.
26] Feng, W. H.; Dong, H. X.; Niu, L. B.; Wen, X.; Huo, L.; Bai, G. Y. J.
Mater. Chem. A 2015, 3, 19807.
27] Ju, X. P.; Liu, X. F.; Gao, X. J.; Niu, L. B.; Feng, W. H.; Bai, G. Y. J.
Mater. Sci. 2016, 51, 7669.
28] Shi, Y.; Yang, H. M.; Zhao, X. G.; Cao, T.; Chen, J. Z.; Zhu, W. W.;
Yu, Y. Y.; Hou, Z. S. Catal. Commun. 2012, 18, 142.
29] Zhang, H.; Huang, F.; Liu, D. L.; Shi, P. Chin. Chem. Lett. 2015, 26,
1
137.
30] Shou, J. X.; Jiang, C. F.; Wang, F.; Qiu, M. Q.; Xu, Q. G. J. Mol. Liq.
015, 207, 216.
31] Chen, C.; Felton, R.; Buffet, J. C.; O'Hare, D. Chem. Commun. 2015,
1, 3462.
32] Chen, X. T.; Mi, F.; Zhang, H.; Zhang, H. Q. Mater. Lett. 2012, 69,
8.
33] Zhang, H.; Zhang, G. Y.; Bi, X.; Chen, X. T. J. Mater. Chem. A 2013,
, 5934.
34] Bai, G. Y.; Wen, X.; Zhao, Z.; Li, F.; Dong, H. X.; Qiu, M. D. Ind.
2
5
4
[49] Xie, Y. J.; Yan, B.; Xu, H. L.; Chen, J.; Liu, Q. X.; Deng, Y. H.;
Zeng, H. B. ACS Appl. Mater. Interfaces 2014, 6, 8845.
[50] Liu, X. F.; Shi, L. J.; Feng, W. H.; Niu, L. B.; Liu, C.; Bai, G. Y. RSC
Adv. 2014, 4, 44302.
1
(Lu, Y.)
8
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