Constructing magnetic Si-C-Fe hybrid microspheres for room temperature nitroarenes reduction

Article abstract of DOI:10.1039/c7ta01156c

In this work, we present, for the first time, the synthesis and characterization of magnetic Si-C-Fe hybrid microspheres and their catalytic performance in room temperature reduction of 4-nitrophenol as a representative sustainable process for converting environmental pollutants to fine chemicals. The ferrocene-modified polydivinylbenzene (Fc-PDVB) precursor was synthesized by Pt-catalyzed hydrosilylation between the residual vinyl groups on the PDVB surface and 1,1′-bis (dimethylsilyl)ferrocene, where further pyrolysis led to the formation of Fe nanocrystal-containing Si-C-Fe hybrid microspheres. The precursor and hybrid microspheres were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), BET surface area/porosity, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), magnetic properties and MAS solid-state NMR measurements. The ultimate microspherical catalyst exhibited nano- and meso-pores, a high specific surface area (i.e., 347.9 m² g^-1) and good ferromagnetic properties. Efficient catalytic activity (TOF: 0.163 s^-1), 100% selectivity (to 4-aminophenol) and excellent reusability (with easy separation) have been delivered. The achieved microspheres outperform a number of nanomaterials such as supported noble metal particles, composites, monoliths and sheets. We have confirmed by DFT calculations that the activation of 4-nitrophenol via its weak non-covalent interaction with the sp² carbon domain of Si-C-Fe hybrid microspheres contributed to the superior performance which can be extended to a range of nitrobenzenes.

Full text of DOI:10.1039/c7ta01156c

View Article Online
View Journal
Journal of
Materials Chemistry A
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: X. Zhang, L. Chen,
J. Yun, X. Wang and J. Kong, J. Mater. Chem. A, 2017, DOI: 10.1039/C7TA01156C.
This is an Accepted Manuscript, which has been through the
Volume
4 Number 1 7 January 2016 Pages 1–330
Royal Society of Chemistry peer review process and has been
accepted for publication.
Journal of
Materials Chemistry A
Accepted Manuscripts are published online shortly after
Materials for energy and sustainability
www.rsc.org/MaterialsA
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 2050-7488
PAPER
Kun Chang, Zhaorong Chang et al.
Bubble-template-assisted synthesis of hollow fullerene-like
MoS2 nanocages as a lithium ion battery anode material
rsc.li/materials-a

Page 1 of 44
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C7TA01156C
Table of Contents Entry
1/1

Journal of Materials Chemistry A
Page 2 of 44
View Article Online
DOI: 10.1039/C7TA01156C
Constructing Magnetic Si-C-Fe Hybrid Microspheres for
Room Temperature Nitroarenes Reduction
Xiaofei Zhang,a Lixin Chen,a Jin Yun,a Xiaodong Wang,b,* and Jie Konga,*
aMOE Key Laboratory of Space Applied Physics and Chemistry, Shaanxi Key
Laboratory of Macromolecular Science and Technology, School of Science,
Northwestern Polytechnical University, Xi’an, 710072, P. R. China
bSchool of Engineering, University of Aberdeen, Aberdeen AB24 3UE, Scotland, UK
Corresponding author e-mail addresses:
kongjie@nwpu.edu.cn (J.K.) and x.wang@abdn.ac.uk (X.W.)
1/43

Page 3 of 44
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C7TA01156C
Abstract:
In this work, we present the first synthesis and characterization of magnetic Si-C-Fe
hybrid microspheres and their catalysis in room temperature reduction of
4-nitrophenol as a representative sustainable process of converting environmental
pollutants to fine chemicals. The ferrocene-modified polydivinylbenzene (Fc-PDVB)
precursor was synthesized by Pt-catalyzed hydrosilylation between the residual vinyl
groups on PDVB surface and 1, 1’-bis (dimethylsilyl)ferrocene, where further
pyrolysis led to the formation of Fe nanocrystals-containing Si-C-Fe hybrid
microspheres. The precursor and hybrid microspheres were characterized in terms of
transmission electron microscopy (TEM), Fourier transform infrared spectroscopy
(FT-IR), BET surface area/porosity, powder X-ray diffraction (XRD), X-ray
photoelectron spectroscopy (XPS), magnetic properties and MAS solid-state NMR
measurements. The ultimate microspherical catalyst exhibited nano- and meso-pores,
high specific surface area (i.e., 347.9 m2 g-1) and good ferromagnetic properties.
Efficient catalytic activity (TOF: 0.163 s-1), 100% selectivity (to 4-aminophenol) and
excellent reusability (with easy separation) have been delivered. The achieved
performance outperforms a number of nanomaterials such as supported noble metal
particles, composites, monoliths and sheets. We have confirmed by DFT calculations
that the activation of 4-nitrophenol via its weak non-covalent interaction with the sp2
carbon domain of Si-C-Fe hybrid microspheres contributed to the superior
performance which can be extended to a range of nitrobenzenes.
2/43

Journal of Materials Chemistry A
Page 4 of 44
View Article Online
DOI: 10.1039/C7TA01156C
1. Introduction
Transition metal-containing polymers have received considerable attention in the past
two decades due to their great potential in lithography, redox-active gels, molecular
and ion recognition, liquid crystalline and supramolecular materials.1-5 Hybrid
materials or ceramics with porous structures can be generated by the emission of
volatile species from cross-linked transition metal-containing polymers through
moderate temperature pyrolysis (400–600 oC). It is evident that these hybrid materials
or ceramics with incorporated transition metals exhibit not only improved optical,
electrical, thermal and magnetic properties but also catalytic functionalities.6-9
Due to the above, transition metal-containing polymers are important precursors for
the synthesis of metal-containing nanoparticles (NPs) if the polymerization and
pyrolysis conditions are controlled.10-12 In addition to the common cobalt (Co) and
nickel (Ni)-containing NPs, various iron (Fe)-containing NPs13-15 have also been
proven to possess excellent magnetic, electrical and catalytic properties, where
ferrocene16 has been widely used as a precursor to synthesize carbon nanomaterials
with Fe NPs. So far studies have been mainly focused on the pyrolysis of
ferrocene-containing polymers like linear polyferrocenylsilanes (PFS), cross-linked
PFS, PFS block copolymers, cobalt-clustered PFS, and hyperbranched PFS to obtain
bulk materials,17-21 with little information on using ferrocene-containing polymers for
the synthesis of materials at micro/nano-scale and particularly spherical materials.
Owing to the spherical morphology, spherical materials have shown numerous real
3/43

Page 5 of 44
Journal of Materials Chemistry A
View Article Online
and emerging applications.22,23 For example, spherical catalysts can be easily
DOI: 10.1039/C7TA01156C
dispersed in the reaction solution and separated. In addition, spherical materials
exhibit good mobility and high packing density that promote their use as the electrode
materials.24-26
In this work, we propose for the first time the functionalization of readily available
polydivinylbenzene (PDVB) particles (from precipitation polymerization, with
significant surface residual vinyl groups27-29) by incorporating ferrocene to prepare
ferrocene-containing polymer microspheres whose further pyrolysis can generate
magnetic Si-C-Fe hybrid microspheres. This low-cost and recyclable magnetic
material has been employed for the sustainable conversation of environmental
pollutant 4-nitrophenol (4-NP) at room temperature. This is a critical reaction often
chosen to evaluate the catalytic performance of metal nanoparticles,30-32 since 4-NP
has been a priority pollutant named by the U. S. Environmental Protection Agency
due to its carcinogenic, anthropogenic and toxic nature and the target product
4-aminophenol (4-AP) is a chemical intermediate that is widely used in the synthesis
of analgesic drugs such as acetaminophen, photographic developers, corrosion
inhibitors and dyes.33,34 Most research on catalytic reduction of 4-NP has focused on
noble metallic nanoparticles such as Au, Pd, Pt and Ag.35-43 The development of
cheaper and efficient alternatives is always challenging.
2. Experimental
2.1 Materials
4/43

Journal of Materials Chemistry A
Page 6 of 44
View Article Online
DOI: 10.1039/C7TA01156C
Divinylbenzene (m-and p-mixture, stabilized with 4-tert-butylcatechol),
2-amino-4-chloro-6-nitrophenol, 5-fluoro-2-nitrophenol, 1-bromo-4-nitrobenzene,
2-methoxy-5-nitrophenol, 2-methyl-5-nitrophenol, 1,2-dimethyl-4-nitrobenzene,
n-butyllithium (1.6 M in hexane), N, N, N′, N′-tetramethylethylenediamine (TMEDA),
chlorodimethylsilane (98%), ferrocene (FeCp2, 99%) and
platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (Karstedt’s catalyst, 0.1
M in polydimethylsiloxane terminated with vinyl groups), Fe powder, sodium
borohydride (NaBH4, > 97%) and 4-NP (> 99%) were supplied by J.&K. Sci. Co., Ltd.
China. Toluene was distilled freshly under reflux by sodium/benzophenone. PDVB
microspheres were synthesized according to previous report.44 Chlorodimethylsilane
and ferrocene were used to synthesis 1, 1,-bis(dimethylsilyl)ferrocene as described
previously.45
2.2 Synthesis and pyrolysis of ferrocene-modified PDVB microspheres
Under an argon (purity ≥ 99.999%) atmosphere, a dry flask was charged with PDVB
microspheres (1 g), 1, 1’-bis(dimethylsilyl)ferrocene (4 g), 0.01g of Karstedt’s
catalyst and 150 mL of anhydrous toluene. After sufficient ultrasonic dispersing, the
reaction mixture was stirred for 12 h at 80 oC under argon, the crude product was
separated by vacuum filtration and washed three times successively with
tetrahydrofuran, acetone and diethyl ether. A yellow sample was obtained after drying
at 50 oC for 24 h in vacuum. Then, the as-prepared Fc-PDVB powder was loaded to a
vertical tube furnace for (6 h) pyrolysis in argon (70 mL min-1) at 500 oC, and cooled
down to ambient temperature (at 5 oC min-1). Finally, the Si-C-Fe hybrid microspheres
5/43

Page 7 of 44
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C7TA01156C
were obtained.
2.3 Characterization
Transmission electron microscopy (TEM, FEI, Tecnai G2 F20) was operated at 200
kV, coupled with electron diffraction analysis. Samples for analysis were dispersed in
alcohol and deposited on a holey carbon/Cu grid (200 Mesh). Raman spectra were
recorded using Raman Microprobe (Renishaw, UK) with 514.5 nm Ar+ laser
excitation. UV-vis spectra were recorded using a spectrophotometer UV-2550 model
(Shimadzu, Japan). Fourier Transform Infrared Spectroscopy (FT-IR) was measured
using a Nicolet iSTO spectrometer (Varian, Palo Alto, California, USA) between
4000 to 400 cm-1. The XPS spectra were recorded with a Kratos Axis 165 X-ray
photoelectron spectrometer using a monochromatic Al Kα radiation (hν = 1486.6 eV),
at a take-off angle of 0o. All binding energy values were corrected to C 1s signal
(285.0 eV). The pyrolysis of precursor was studied by thermogravimetric analysis
(TGA) using STA 449 F3 thermoanalyzer with a ramp of 10 K min-1 in argon (50 mL
min-1) between 40−1100 oC.
The MAS solid-state NMR measurements were carried out on a NMR spectrometer
(Bruker Anance III-400, Germany). All spectra were acquired using magic angle
spinning (MAS 54.74) technique with a rotation frequency of 6 kHz for 13C. All
samples were measured with a crosspolarization sequence (CP). The recycle delay
used was 3 s for 13C and the acquisition time was 42.3 ms for 13C. The 29Si NMR
6/43

Journal of Materials Chemistry A
Page 8 of 44
View Article Online
DOI: 10.1039/C7TA01156C
CP/MAS spectra were measured at a spinning speed of around 4.0 kHz, a contact time
of 5 ms, and a recycle delay of 5 s.
X-ray diffractograms (XRD) were recorded on X9Pert Pro Powder diffractometer
using Cu Ka radiation (40 kV, 40 mA, PANalytical B.V., Netherlands). The specific
surface area of selected samples was determined by N2 adsorption–desorption
isotherms at 195.8 oC using the commercial Micromeritics TriStar II 3020 and the
Brunauer–Emmett–Teller (BET) method. Samples were outgassed at 150 oC for 24 h
prior to measurements. The pore-size distribution was obtained using the adsorption
isotherm and Barret-Joyner-Halender (BJH) method.
Magnetic properties of the samples were investigated by a commercial magnetic
property measurement system (Quantum Design Inc., San Diego, USA). The
magnetic behavior as a function of constant applied field (from -10 kOe to 10 kOe)
was recorded at 300 K. ICP-MS (inductively coupled plasma mass spectrometry) was
conducted on an Agilent 7700ce (Agilent Technologies, Santa Clara, CA, USA) using
the aqueous solution.
2.4 Catalytic reduction of 4-nitrophenol (4-NP)
In a typical experiment, 2 mL of 4-NP aqueous solution (3 mM) was mixed with 10
mL fresh NaBH4 solution (0.06 M). N2 gas was then purged through the solution for
30 min to remove dissolved O2. Subsequently, the N2 flow was stopped and 4 mg
as-prepared Si-C-Fe hybrid microspheres (or other catalysts) were added into the
above solution (time t = 0 for reaction) under continuous agitation (at 200 rpm) at 298
7/43

Page 9 of 44
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C7TA01156C
K. Aliquots were removed from the reactor every minute and filtered through a 0.22
μm membrane filter for the determination of activity with UV-vis absorption
spectroscopy. The composition of the product mixture was also analyzed by HPLC
(LC-8A) equipped with a Welchrom® (C18, 5μm, 4.6 × 250 mm) column and
SPD-20A UV-vis detector. Methanol, water and phosphate buffer (pH = 7) were
employed as the mobile phase at a flow rate of 0.5 mL min-1. After each reaction, the
catalyst was separated and washed using 5 mL of 0.01 M NaBH4 solution before the
next experiment.
2.5 Computational details
Although there are considerable enhancements obtained over LDA and such
conventional hybrid density functional theory (DFT) as B3LYP recently.46,47 it is still
changeling to describe accurately non-covalent weak interaction systems in DFT. The
hybrid functional M06-2X, developed by Truhlar et al.48 provides relatively reliable
results for π-π stacking systems.49 Therefore, in this paper, all geometric optimizations
were performed at M06-2X/6-311+g(d,p) level with the D3 version of Grimme's
dispersion correction by using the Gaussian 09 program.
3. Results and Discussion
3.1 Synthesis and characterization of ferrocene-modified PDVB microspheres
The synthesis route of Fc-PDVB microspheres is illustrated in Scheme 1. They were
obtained via the hydrosilylation between vinyl groups on the surface of PDVB
microspheres and 1,1’-bis(dimethylsilyl)ferrocene. As previously reported,50 the
8/43

Journal of Materials Chemistry A
Page 10 of 44
View Article Online
DOI: 10.1039/C7TA01156C
olefin was considered as a nucleophile and thus the Pt colloid/R3SiH intermediate
from the reaction of the Pt colloid and R3SiH was an electrophile in this reaction. So
the ferrocenyl substituent which has electron donating characteristics in
1,1’-bis(dimethylsilyl)ferrocene has an adverse impact on hydrosilylation, while the
electron donating ability of phenyl makes vinyl groups on the surface of PDVB
microspheres display a faster rate of hydrosilylation. Normally, the reaction hardly
occurred when temperature was lower than 50 oC. With increasing temperature from
50 to 80 oC, the reaction was initiated and consequently the color of as-prepared
Fc-PDVB microspheres changed from light yellow to orange. According to PDVB
microspheres formation mechanism,51 PDVB microspheres have a thin surface layer
consisting of lightly crosslinked and swellable poly(divinylbenzene), and at high
temperature (80 oC), toluene can lead to swollen surface layer of PDVB microspheres
so that the 1,1’-bis(dimethylsilyl)ferrocene can penetrate into every space among the
polymer chains, giving it more chance to react with double bond from the surface of
PDVB microspheres, even in the interior. The TEM images in Fig. 1 show
well-defined, smooth and uniform Fc-PDVB microspheres with an average diameter
of about 2 μm and morphology which is similar to that of the original PDVB
microspheres. This confirms the preparation procedure (e.g., washing) is sufficient in
removing any unreacted 1,1’-bis(dimethylsilyl)ferrocene and Karstedt’s catalyst on
the surface of microspheres by physical adsorption.
In Fig. 2, the FT-IR characteristic peak at 1254 cm-1 corresponds to the asymmetric
deformation vibration of the Si-CH3 and the out-of-plane CH bending vibration of Cp
9/43

Page 11 of 44
Journal of Materials Chemistry A
View Article Online
is observed at 1165 and 1035 cm-1. In addition, the peak of Si-H at 2113 cm-1
decreases significantly, which indicates that Si-H groups from 1,
DOI: 10.1039/C7TA01156C
1’-bis-(dimethylsilyl)ferrocene reacted with vinyl groups. Due to the influence of
aromatic structures from PDVB segments and ferrocenyl units, it is difficult to
determine the decrease of the absorption peak intensity of double bonds located on the
surface of PDVB microspheres from FT-IR spectra. We therefore employed the MAS
solid-state NMR to probe this and the 13C CP/MAS NMR and 29Si NMR spectra are
shown in Fig. 3 along with the peak assignments according to the literature.52,53 In
comparison to the original PDVB microspheres, the ferrocene-modified ones show
decreased intensity of the signals at 137.3 and 112.4 ppm for the carbon atoms of
CH=CH2, demonstrating the consumption of double bonds located on the surface of
PDVB. The increased intensity of the peak at 29.5 ppm from CH2Ph shows the
generation of SiCH2CH2Ph from β-addition hydrosilylation. The intensity of the peak
at 15.5 ppm from C-CH3 is not increased, which means that no α-adducts were
obtained. In another words, the hydrosilylation between carbon-carbon double bonds
on the PDVB surface and 1, 1’-bis-(dimethylsilyl)ferrocene is conducted in β-addition
regime. In addition, the chemical shifts at 71.9, 68.9 and −2.4 ppm clearly show the
existence of Cp and Si-CH3, which further confirms the occurrence of hydrosilylation.
Similarly, in the 29Si NMR spectrum (Fig. 3), it is evident that there are two types of
silicon atoms. The first one, δ = −0.1 ppm, is correlated with Si-CH2 from the 1,
1’-bis-(dimethylsilyl)ferrocene on the PDVB surface after hydrosilylation. The
second one, δ = −19.8 ppm, can be assigned to the chemical shift of unreacted Si-H
10/43

Journal of Materials Chemistry A
Page 12 of 44
View Article Online
groups on the other side of 1, 1’-bis-(dimethylsilyl)ferrocene. These results furDthOeI:r10.1039/C7TA01156C
confirm that our hydrosilylation between vinyl groups on the surface of PDVB
microspheres and 1,1’-bis(dimethylsilyl)ferrocene has a high regioselectivity, whereas
it was reported in the literature that both α- and β-isomers might be obtained in other
hydrosilylation systems.54 This can be attributed to the remarkable steric hindrance of
phenyl and ferrocenyl, which have unfavorable influences on attack between Pt
colloid/R3SiH intermediate and methine carbon on double bonds. In addition, owing
to the weak electron-withdrawing inductive effect of phenyl on double bonds, the
electron density of methylene carbon is higher than that of methine carbon, which
makes the latter easier for attack by an electrophile to form β-addition.
The surface characteristics of Fc-PDVB microspheres were evaluated by XPS
analysis (Fig. 4) and the associated atomic composition can be found in Table 1. All
the silicon, carbon, oxygen and iron elements are evident on the surface. The Si 2p
peak can be deconvoluted into the C-Si and C-Si-O peaks and the C1s peak can be
deconvoluted into the C=C and C-C, C-O-H, and C=O peaks. The Fe 2p spectrum
shows two peaks that can be assigned to Fe 2p3/2 and Fe 2p1/2 in the ferrocene unit,
respectively. These are consistent with comparable systems reported in the
literature.55-57 The presence of oxygen on the surface of microspheres is mainly due to
the moisture and O2 absorbed by the samples before measurement. In summary, the
FT-IR, 13C and 29Si CP/MAS NMR and XPS results have provided fundamental
details on the structure of ferrocene-modified PDVB microspheres after surface
hydrosilylation.
11/43

Page 13 of 44
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C7TA01156C
3.2 Pyrolysis of ferrocene-modified PDVB microspheres and characterization of
the produced materials
As can be seen from the TGA curves in Fig. 5, the 1,1’-bis-(dimethylsilyl)ferrocene is
almost totally sublimated or evaporated after around 200 oC. For the original PDVB
microspheres, a rapid thermolytic degradation in the temperature range of 400-600 oC
can be observed, after which the TGA curve almost levels off. In comparison to this,
the yield upon heat treatment of the Fc-PDVB microspheres is slightly increased. This
is due to the better thermal stability of ferrocenylsilane units introduced by the
hydrosilylation of 1,1’-bis-(dimethylsilyl)ferrocene. Fig. 6 shows the simultaneous
TGA and mass spectrometry results of the Fc-PDVB microspheres. Similar to the
original PDVB microspheres, the thermolysis of Fc-PDVB microspheres is mainly
accompanied by the evolutions of H2 (m/z=2), hydrocarbons CHx (x=1-3, m/z=13-15),
CH4 (m/z=16), H2O (m/z=18), CHCH (m/z=26), CH2CH2 (m/z=28), CHCHC
(m/z=38), CH3CHO (m/z=44) and oligomer fragments (m/z=50, 52, 63 and 74).
The evolution of CH4 and/or hydrocarbons between 300 and 600 oC can be attributed
to the decomposition of Si-CH3 groups and cleavage of C-C bonds. An ionized group
with mass of 12 is observed, resulting from carbon monoxide and carbon dioxide.
Oxygen, which allows the oxidation of samples to produce CO, H2O, and CO2 at high
temperature, originates from the moisture content absorbed by the microspheres’
surface. However, the thermolysis behavior of Fc-PDVB microspheres is noticeably
different from that of PDVB microspheres, with the decomposition of Si-CH3 and Cp,
12/43

Journal of Materials Chemistry A
Page 14 of 44
View Article Online
the CH3 (m/z=15), CHCHC (m/z=38) and oligomer fragment (m/z=52) evolutiDoOnIs: 10.1039/C7TA01156C
becomes stronger than that of PDVB microspheres at 350-700 oC. In contrast, the
evolution of C (m/z=12), OH (m/z=17), H2O (m/z=18) and CO2 (m/z=44) from the
pyrolysis of Fc-PDVB microspheres is decreased significantly. This can be attributed
to the fact that the formation of Fc-PDVB microspheres has consumed the vinyl
groups (easy to oxidize) on the PDVB surface.
The pyrolyzed microspheres from Fc-PDVB at 500 oC in argon were further
characterized by XPS as shown in Fig. 7. The summary of binding energy of different
chemical bonds is given in Table 2, where detailed assignment of spectra can be
found in the literature.58-61 Besides C-Si, C=C, C-C, some oxygen-related bonds, such
as Si-O, C-O, C-OH, C=O and COOH can also be found. For the Fe 2p spectrum, the
peaks at 707.5 eV, 709.6 eV and 712.0 eV represent the binding energies of Fe0 2p3/2,
Fe2+ 2p3/2 and FeOOH 2p3/2, respectively. These different oxidation states could be
produced by the surface oxidation of Fe0 by the moisture adsorbed. XPS analysis
indicates that the pyrolyzed microspheres exhibit a Si-C-Fe hybrid structure which is
also confirmed by the XRD results (see Fig. S1(a)†) indicating the formation of Fe
nanocrystals (ICSD, PDF#06-0696) in the microspheres. As shown in the XPS results,
the major ingredient of Si-C-Fe hybrid microspheres is free carbon, and therefore
Raman spectroscopy as an efficient tool for the examination of the structure of free
carbons was used to study the structural information of the free carbon in Si-C-Fe
hybrid microspheres. The Raman spectra (see Fig. S1(b)†) exhibit a broad absorption
peak at 1355 cm-1 and a sharp one at 1580 cm-1, corresponding to carbon vibration of
13/43

Page 15 of 44
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C7TA01156C
the D and G bands, respectively. The former one is ascribed to sp3 carbons while the
latter originates from in-plane bond stretching of sp2 carbon.62 The strong absorption
peak at 1580 cm-1 suggests the present of large number of sp2-bonded carbons in
Si-C-Fe hybrid microspheres.
Representative TEM images of Si-C-Fe hybrid microspheres are shown in Fig. 8.
Compared with Fc-PDVB microspheres (Fig. 1b), the size of the pyrolyzed samples
became smaller because of sharp shrinkage during the transformation of the organic
network of Fc-PDVB microspheres to organic-inorganic Si-C-Fe hybrid microspheres.
In addition, nanoscale Fe-rich region (diameter of ~10 nm) is evident in the higher
magnification TEM image. The measured d (110) spacing of Fe is 0.203 nm that is
consistent with the value obtained from XRD measurement and the literature. This
further confirms the presence of Fe0. The nitrogen physisorption measurements of the
pyrolyzed microspheres in Fig. 9 exhibit a type I isotherm, which is typical for nano-
and meso-porous structures with a specific surface area of 347.9 m2 g-1. A large
nitrogen uptake at low relative pressure (p/p0 < 0.05) indicates the presence of
significant fraction of micropores below 20 Å. The formation of porous structures can
be resulted from the evolutions of gases (see Fig. 6) during the transformation of
organic to inorganic microspheres.
The magnetic properties of the Si-C-Fe hybrid microspheres have been studied and
the magnetization curve is presented in Fig. 10. In the magnetic field at 300 K, the
pyrolyzed microspheres are swiftly magnetized with an immediate rise in its
14/43

Journal of Materials Chemistry A
Page 16 of 44
View Article Online
magnetization curve and the saturation magnetization was 2.4 emu g-1. In the eDnOlaI: r1g0.e10d39/C7TA01156C
magnetization curve in the low-field region, the Si-C-Fe hybrid microspheres exhibit
hysteresis loops with low small remanent magnetization (0.31 emu g-1). This indicates
Si-C-Fe hybrid microspheres have soft ferromagnetism at room-temperature which is
similar to the Si/C/Fe ceramic material containing Fe0 nanoparticles.63 This result
further confirms the formation of Fe0 nanocrystals in Si-C-Fe hybrid microspheres
which is in line with previous analyses. To summarize, Si-C-Fe hybrid microspheres
containing nanocrystalline Fe0 and significant regions of sp2-bonded carbons were
prepared successfully by Fc-PDVB microspheres pyrolysis with high specific surface
area and good ferromagnetism.
3.3 Catalytic response
The reduction of 4-NP by NaBH4 was chosen as a model reaction to evaluate the
catalytic performance of Si-C-Fe hybrid microspheres in pollutant treatment for
environmental sustainability. A series of control experiments have been conducted to
benchmark the results in this work. We first excluded the possibility of any reaction
taking place in the absence of catalyst as shown in Fig. S2†. It is well established that
4-NP solution exhibits a strong absorption peak at 400 nm after addition of an
aqueous solution of NaBH4.64,65 The intensity of the absorption peak at 400 nm
showed no significant decrease (in 5 min) and the characteristic peak of 4-AP did not
appear even at prolonged period (i.e., 100 min, see Fig. S2†). This means that there is
no reduction happening as a result of the repulsion between the negatively charged
15/43

Page 17 of 44
Journal of Materials Chemistry A
View Article Online
−
DOI: 10.1039/C7TA01156C
BH4 and ionized 4-NP (i.e., 4-nitrophenolate ions).66 Su and coworkers have reported
previously that pure carbon materials also exhibit catalytic activity in nitrobenzene
reduction (by hydrazine hydrate)71-73 We then considered whether the carbon
components in our catalyst are active as there is a large amount of carbon in the
Si-C-Fe hybrid microspheres according to the XPS and Raman results (see Fig. 7 and
Fig. S1b†). To check this, carbon microspheres were prepared by the pyrolysis of
pure PDVB microspheres (i.e., with no Fe or Si) under the same conditions and
examined. The results show that the pyrolyzed PDVB microspheres exhibit no
catalytic activity in 4-NP reduction (Fig. S3†), attributable to the absence of active
sites like C-O, -COO-, C-O-B, B=O, B-O, C-B groups on the surface of our catalysts
(prepared/treated in an inert Ar atmosphere). The same response was also observed
over the Si-C hybrid materials (pyrolyzed product of silicon and acetylene polymer
heated at 773 K, i.e., with no Fe)
Fig. 11(a) shows the successive UV-Vis spectra of aqueous solutions containing 4-NP
and NaBH4 in the presence of Si-C-Fe hybrid microspheres. By adding a small
amount (4 mg) of magnetic Si-C-Fe microspheres as catalyst, the absorption peak at
400 nm disappeared completely (i.e., 100% conversion, Fig. 11(b)) in 5 min with a
simultaneous increase in the characteristic peak of 4-AP. The appearance of a
colorless solution (from yellow), indicated that only the conversion of 4-NP into 4-AP
was achieved (i.e., 100% selectivity).40,67 Since NaBH4 was used in excess, the
reduction of 4-NP can be considered as a first order reaction and the following
kinetics is applicable.
16/43

Journal of Materials Chemistry A
Page 18 of 44
View Article Online
DOI: 10.1039/C7TA01156C
ln(Ct/C0) = −kappt (or ln(At/A0) = −kappt)
where Ct is the concentration of 4-NP at time t and kapp is the apparent rate constant.
kapp can then be normalized to the concentration of Fe deriving knor.68,69 Fig. 11(c)
shows ln(At/A0) as a function reaction time over Si-C-Fe hybrid microspheres, where
kapp and knor obtained are 19.27  10-3 s-1 and 0.326 s-1 mM-1 (using a Fe content of
0.99 wt% (from ICP analysis)), respectively. In order to investigate the intrinsic
catalytic response, it is necessary to establish reaction conditions under
kinetic/chemical control wherein transport constraints are minimized. A nearly
proportional change (8.05, 19.27 and 36.73  10-3 s-1) in the apparent rate constant
(Fig. 11(c) and S4†) with changing catalyst mass (2, 4 and 8 mg) has been observed,
demonstrating negligible interphase diffusional limitations. Subsequent tests were
thus conducted using 4 mg of catalyst. To further demonstrate the potential of the
synthesized Si-C-Fe microspheres in catalysis, a harsher reaction condition, i.e.,
sub-ambient temperature, 273 K, was considered and it is stimulating to notice that
the catalyst can still promote the target reaction, although at a lower rate (kapp = 4.49 
10-3 s-1, see Fig. S5†).
Initial turnover frequency (TOF, moles of 4-NP converted per mole of Fe per second)
can be calculated using the obtained kapp. The performance (under comparable
conditions) of different metal nanocatalysts employed for the reduction of 4-NP have
been summarized in Table 3. It is noteworthy that our system has outperformed most
of the recent catalysts reported including noble metals (Pd, Pt, Au and Ag)31,39-43 in
various forms (e.g., nanoparticles, nanocomposites, etc.) and is ~20% more active
17/43

Page 19 of 44
Journal of Materials Chemistry A
View Article Online
(0.163 s-1 vs. 0.136 s-1) than the work employing nanosheet array-like Cu DcOaIt: a10l.y10s3t9/C7TA01156C
(CuxMg3-xAl-layered double hydroxide/reduced graphene oxide) reported very
recently.70 Moreover, the magnetic Si-C-Fe microspheres can be easily separated
from the reaction system by an external magnet for reuse (see Fig. 11(b)) and
the recycled catalyst exhibited similar high activity in five successive cycles
(see Fig. 11(d)), demonstrating excellent reusability. These results suggest an
interesting development in novel catalyst formulations for room and sub-ambient
temperature pollution abatement.
In addition to the high surface area and well dispersed Fe0 (as active sites74 and Fig.
S6†) on the surface of Si-C-Fe hybrid microspheres (see characterization) that are
beneficial for catalysis, we also consider that the non-covalent interaction between
4-NP and the sp2 carbon domain (see Raman spectra in Fig. S1b†) is the main reason
for the high activity achieved. It is such interaction that gathers 4-NP on the surface of
Si-C-Fe hybrid microspheres, accessible to the active sites. This consideration is
based on previous reports that the intimate interaction between graphene (sp2 carbon)
and aromatic derivatives due to their π-character may make the reactants easily
accessible to the active sites of noble metal.75,76 In order to confirm the presence of
such interaction in our system, quantum chemical DFT calculations were carried out.
The optimized structures of 4-NP, sp2 carbon domain and their mixture are shown in
Fig. 12. The calculated atomic distance between the carbons of 4-NP and sp2 carbon
domain of Si-C-Fe hybrid microspheres is about 3.1-3.4 Å which is within the typical
range of van der Waals distance (3−4 Å).77 This demonstrates that the
18/43

Journal of Materials Chemistry A
Page 20 of 44
View Article Online
concentration/activation of 4-NP on the catalyst surface can be related to van dDeOrI: 10.1039/C7TA01156C
Waals forces between sp2 carbons domain and 4-NP, i.e., weak non-covalent
interaction.
To ensure the general applicability of our catalyst in converting environmental
pollutants into useful chemicals, a series of nitroarenes with different substituent
groups were also considered. The results (see Table 4) illustrate that the Si-C-Fe
hybrid microspheres exhibit efficient catalytic activity to selectively reduce
nitroarenes with different functionalities, showing great potential as an alternative to
the noble metal catalytic materials.
4. Conclusions
In summary, ferrocene-modified PDVB microspheres were successfully synthesized
by the hydrosilation between the residual vinyl groups on the PDVB surface and 1,
1’-bis (dimethylsilyl)ferrocene. The pyrolysis of ferrocene-modified PDVB
microspheres resulted in the formation of novel Fe nanocrystal-containing Si-C
magnetic microspheres which exhibited nano- and meso-porous structures, large
surface area, good ferromagnetic properties and superior catalytic activity (due to the
weak non-covalent interaction) in the reduction of a series of nitrobenzenes with a
reusability feature. The results in this study provide a convenient strategy for the
synthesis of low cost, magnetic, hybrid microspherical materials with catalysis
functionalities, which may find wide applications in sustainable conversion of
environmental pollutants as well as chemical intermediates production.
19/43

Page 21 of 44
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C7TA01156C
Acknowledgments
This research is supported by the National Natural Science Foundation of China
(21174112). X.W. acknowledges support from School of Engineering, the University
of Aberdeen. The useful discussion with Dr. M.D. Symes (University of Glasgow) is
gratefully acknowledged.
Notes and References
1 G. R. Whittell, M. D. Hager, U. S. Schubert, I. Manners, Nat. Mater., 2011, 10
,
176-188.
2 K. Liu, C. L. Ho, S. Aouba, Y. Q. Zhao, Z. H. Lu, P. Srebri, N. Coombs, P. Dube,
H. E. Ruda, W. Y. Wong, I. Manners, Angew. Chem. Int. Ed., 2008, 47, 1255-1259.
3 M. A. Hempenius, C. Cirmi, F. L. Savio, J. Song, G. J. Vancso, Macromol.
Rapid Commun., 2010, 31, 772-783.
4 R. Ahmed, A. Priimagi, C. F. J. Faul, I. Manners, Adv. Mater., 2012, 24, 926-931.
5 Q. Sun, J. W. Y. Lam, K. Xu, H. Xu, J. A. K. Cha, P. C. L. Wong, G. Wen, X.
Zhang, X. Jing, F. Wang, B. Z. Tang, Chem. Mater., 2000, 12, 2617-2624.
6 Q. Li, X. Yin, W. Duan, L. Kong, X. Liu, L. Cheng, L. Zhang, J. Eur. Ceram.
Soc., 2014, 34, 2187-2201.
7 M. Zaheer, T. Schmalz, G. Motz, R. Kempe, Chem. Soc. Rev., 2012, 41
,
5102-5116.
8 M. Zaheer, C. D. Keenan, J. Hermannsdörfer, E. Roessler, G. Motz, J. Senker, R.
Kempe, Chem. Mater., 2012, 24, 3952-3963.
9 M. Hojamberdiev, R. M. Prasad, K. Morita, M. A. Schiavonc, R. Riedel,
Micropor. Mesopor. Mater., 2012, 151, 330-338.
10 L. Ren, J. Zhang, C. G. Hardy, S. Ma, C. Tang, Macromol. Rapid Commun.,
2012, 33, 510-516.
11 R. Fu, T. F. Baumann, S. Cronin, G. Dresselhaus, M. S. Dresselhaus, J. H.
Satcher Jr, Langmuir, 2005, 21, 2647-2651.
20/43

Journal of Materials Chemistry A
Page 22 of 44
View Article Online
DOI: 10.1039/C7TA01156C
12 W. Y. Chan, S. B. Clendenning, A. Berenbaum, A. J. Lough, S. Aouba, H. E.
Ruda, J. Am. Chem. Soc., 2005, 127, 1765-1772.
13 H. M. T. Galvis, J. H. Bitter, C. B. Khare, M. Ruitenbeek, A. I. Dugulan, K. P.
de Jong, Science, 2012, 335, 835-838.
14 C. Lee, J. Y. Kim, W. I. Lee, K. L. Nelson, J. Yoon, D. L. Sedlak, Environ, Sci.
Technol., 2008, 42, 4927-4933.
15 Y. Xu, D. Zhao, Water Res., 2007, 41, 2101-2108.
16 Y. Lu, Z. Zhu, Z. Liu, Carbon, 2005, 43, 369-374.
17 K. Liu, S. B. Clendenning, L. Friebe, W. Y. Chan, X. Zhu, M. R. Freeman, G.
C. Yang, C. M. Yip, D. Grozea, Z. H. Lu, I. Manners, Chem. Mater., 2006, 18
,
2591-2601.
18 D. A. Rider, K. Liu, J. C. Eloi, L. Vanderark, L. Yang, J. Y. Wang, D. Grozea, Z.
H. Lu, T. P. Russell, I. Manners, ACS Nano, 2008, , 263-270.
19 N. McGrath, F. H. Schacher, H. Qiu, S. Mann, M. A. Winnik, I. Manners,
Polym. Chem., 2014, , 1923-1929.
2
5
20 K. Temple, K. Kulbaba, K. N. Power-Billard, I. Manners, K. A. Leach, T. Xu,
T. P. Russell, C. J. Hawker, Adv. Mater., 2003, 15, 297-300.
21 J. Shi, B. Tong, Z. Li, J. Shen,W. Zhao, H. Fu, J. Zhi, Y. Dong, M. Häussler, J.
W. Y. Lam, B. Z. Tang, Macromolecules, 2007, 40, 8195-8204.
22 M. Xie, X. Dai, S. Meng, X. Fu, S. Chen, Chem. Eng. J., 2014, 245, 107-116.
23 R. Nan, Y. H. Yang, S. Jiang, Y. H. Zhang, H. L. Xu, G. Zi, Y. Tang, J. Catal.,
2007, 251, 182–188.
24 C. Zhang, Z. Chen, Z. Guo, X. W. D. Lou, Energ. Environ. Sci., 2013, 6,
974-978.
25 Z. Ju, C. Guo, Y. Qian, B. Tang, S. Xiong, Nanoscale, 2014,
26 J. Zhou, J. Lian, L. Hou1,J. Zhang, H. Gou, M. Xia, Y. Zhao, T. A. Strobel, L.
Tao, F. Gao, Nat. Commun., 2015, , 8503.
6, 3268-3273.
6
27 I. Koprinarov, A. P. Hitchcock, W. H. Li, Y. M. Heng, H. D. H. Stöver,
Macromolecules, 2001, 34, 4424-4429.
28 J. S. Downey, R. S. Frank, W. H. Li, H. D. H. Stöver, Macromolecules, 1999,
21/43

Page 23 of 44
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C7TA01156C
32, 2838-2844.
29 W. H. Li, H. D. H. Stöver, Macromolecules, 2000, 33, 4354-4360.
30 J. Zeng, Q. Zhang, J. Chen, Y. Xia, Nano Lett., 2009, 10, 30-35.
31 P. Zhang, C. Shao, Z. Zhang, M. Zhang, J. Mu, Z. Guo, Y. Liu, Nanoscale,
2011, , 3357-3363.
3
32 S. Saha, A. Pal, S. Kundu, S. Basu, T. Pal, Langmuir, 2010, 26, 2885-2893.
33 S. K. Tanielyan, J. J. Nair, N. Marin, G. Alvez, R. J. McNair, D. Wang, R. L.
Augustine, Org. Process Res. Dev., 2007, 11, 681-688.
34 J. F. Corbett, Dyes Pigments, 1999, 41, 127-136.
35 S. Gao, Z. Zhang, K. Liu, B. Dong, Appl. Catal. B: Environ., 2016, 188
,
245-252.
36 X. Gu, W. Qi, X. Xu, Z. Sun, L. Zhang, W. Liu, X. Pan, D. S. Su, Nanoscale,
2014, , 6609-6616.
6
37 P. Zhao, X. Feng, D. Huang, G. Yang, D. Astruc, Coordin. Chem. Rev., 2015,
287, 114-136.
38 M. A. Mahmoud, M. A. El-Sayed, ChemCatChem, 2014, 6, 3540-3546.
39 M. Zhu, C. Wang, D. Meng, G. Diao, J. Mater. Chem. A, 2013, 1,
2118-2125.
40 Y. Fang, E. Wang, Nanoscale, 2013, 5, 1843–1848.
41 H. Liu, D. Wan, D. Jiang, J. Ming, ACS Appl. Mater. Interfaces, 2015
20885−20892.
, 7,
42 M. Tang, G. Huang, X. Li, X. Pang, H. Qiu, Mater. Chem. Phys., 2015, 162,
31-40.
43 W. Hu, B. Liu, Q. Wang, Y. Liu, Y. Liu, P. Jing, S. Yu, L. Liu, J. Zhang,
Chem. Commun., 2013, 49, 7596-7598.
44 F. Bai, X. Yang, W. Huang, Macromolecules, 2004, 37, 9746-9752.
45 R. Jain, H. Choi, R. A. Lalancette, J. B. Sheridan, Organometallics, 2005, 24
1468-1476
,
46 X. Xu, W.A. Goddard III, Proc. Natl. Acad. Sci. U.S.A., 2004, 101, 2673–2677.
47 H. Tachikawa, H. Kawabata, J. Phys. Chem. C, 2009, 113, 7603–7609.
22/43

Journal of Materials Chemistry A
Page 24 of 44
View Article Online
DOI: 10.1039/C7TA01156C
2,
48 Y. Zhao, N.E. Schultz, G.D. Truhlar, J. Chem. Theory Comput., 2006,
364–382.
49 W. Sun, Y. Bu, Y. Wang, J. Phys. Chem. C, 2011, 115, 3220–3228.
50 L. N. Lewis. J. Am. Chem. Soc., 1990, 112, 5998-6004.
51 J. S. Downey, G. McIsaac, R. S. Frank, H. D. H. Stöver, Macromolecules, 2001,
34, 4534-4541.
52 M. Gaborieau, L. Nebhani, R. Graf, L. Barner, C. Barner-Kowollik,
Macromolecules, 2010, 43, 3868-3875.
53 J. Kong, T. Schmalz, G. Motz, A. H. E. Müller, Macromolecules, 2011, 44
1280-1291.
,
54 S. J. Wang, X. D. Fan, J. Kong, J. R. Lu, Polymer, 2009, 50, 3587-3594.
55 G. Zhang, S. Sun, D. Yang, J. P. Dodelet, E. Sacher, Carbon, 2008, 46
,
196-205.
56 L. L. Meng, X. F. Zhang, Y. S. Tang, K. H. Su, J. Kong, Sci. Rep., 2015, 5,
7910.
57 C. M. Woodbridge, D. L. Pugmire,R. C. Johnson, N. M. Boag, M. A. Langell,
J. Phys. Chem. B, 2000, 104, 3085-3093.
58 J. R. Waldrop, R. W. Grant, Y. C. Wang, R. F. Davis, J. Appl. Phys., 1992, 72
,
4757-4760.
59 W. F. Zhao, Y. S. Tang, J. Xi, J. Kong, Appl. Surf. Sci., 2015, 326, 276-284.
60 V. Stambouli, C. Palacio, H. J. Mathieu, D. Landolt, Appl. Surf. Sci., 1993, 70
,
240-244.
61 J. Kong, M. J. Wang, J. H. Zou, L. N. An, ACS Appl. Mater. Interfaces, 2015,
6733-6744.
7,
62 S. Karlin, P. Colomban, J. Raman Spectrosc., 1997, 28, 219-228.
63 Z. Yu, L. Yang, H. Min, P. Zhang, C. Zhou, R. Riedel, J. Mater. Chem. C, 2014,
, 1057-1067.
2
64 J. Zeng, Q. Zhang, J. Chen, Y. Xia, Nano Lett., 2010, 10, 30-35.
65 K. Hayakawa, T. Yoshimura, K. Esumi. Langmuir, 2003, 19, 5517-5521.
66 D. Xu, P. Diao, T. Jin, Q. Wu, X. Liu, X. Guo, H. Gong, F. Li, M. Xiang, R. Yu,
23/43

Page 25 of 44
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C7TA01156C
ACS Appl. Mater. Interfaces, 2015, 7, 16738-16749.
67 P. Zhang, R. Li, Y. Huang, Q. Chen, ACS Appl. Mater. Interfaces, 2014,
2671-2678.
6,
68 T. Yu, J. Zeng, B. Lim, Y. Xia, Adv. Mater., 2010, 22, 5188-5192.
69 M. Rashid, TK Mandal. Adv. Funct. Mater., 2008, 18, 2261-2271.
70 L. Dou, H. Zhang, J. Mater. Chem. A, 2016, 4, 18990-19002.
71 S. Wu, G. Wen, R. Schlögl, D. S. Su, Phys. Chem. Chem. Phys., 2015, 17
,
1567-1571.
72 Y. Lin，S. Wu，W. Shi，B. Zhang，J. Wang, Y. A. Kim, M. Endo, D. S. Su,
Chem. Commun., 2015, 51, 13086-13089.
73 S. Wu, G. Wen, B. Zhong, B. Zhang,X. Gu, N. Wang, D. S. Su, Chin. J.
Catal. 2014, 35, 914-921.
74 S. Bae, K. Hanna, Environ. Sci. Technol., 2015, 49,10536-10543.
75 R. Nie, J. Shi, W. Du, W. Ning, Z. Hou, F. S. Xiao, J. Mater. Chem. A, 2013,
9037-9045.
1
,
76 J. H. Yang, G. Sun, Y. Gao, H. Zhao, P. Tang, J. Tan, A.Lu, D. Ma, Energ.
Environ. Sci., 2013, 6, 793-798.
77 P. Sutter, J. T. Sadowski, E. Sutter, Phys. Rev. B, 2009, 80, 308-310.
24/43

Journal of Materials Chemistry A
Page 26 of 44
View Article Online
DOI: 10.1039/C7TA01156C
Table, Scheme and Figure Captions:
Table 1 The binding energy (B.E.) of chemical bonds of ferrocene-modified PDVB
microspheres.
Table 2 The binding energy (B.E.) of chemical bonds of the synthesized Si-C-Fe
hybrid microspheres.
Table 3 Comparison of catalytic performance by various metal nanocatalysts for the
reduction of 4-nitrophenol.
Table 4 Catalytic performance of Si-C-Fe hybrid microspheres in the reduction of
various nitroarenes (to the corresponding amines).a
Scheme 1 The synthesis scheme of ferrocene-modified PDVB microspheres by the
hydrosilylation between vinyl groups on the surface of PDVB microspheres and 1,
1’-bis(dimethylsilyl)ferrocene.
25/43

Page 27 of 44
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C7TA01156C
Fig. 1 TEM images of PDVB microspheres (a) and ferrocene-modified PDVB
microspheres (b).
Fig. 2 The FT-IR spectra of ferrocene-modified PDVB microspheres (a), PDVB
microspheres (b) and 1, 1’-bis-(dimethylsilyl)ferrocene (c).
Fig. 3 13C CP/MAS NMR spectra of ferrocene-modified PDVB microspheres (red
line) and PDVB microspheres (black line), and 29Si CP/MAS NMR spectrum of
ferrocene-modified PDVB microspheres (green line).
Fig. 4 XPS spectra of ferrocene-modified PDVB microspheres after surface
hydrosilylation of microspheres and 1, 1’-bis(dimethylsilyl)ferrocene.
Fig. 5 The thermalgravimetry curves of ferrocene-modified PDVB microspheres (a),
original PDVB microspheres (b) and 1, 1’-bis-(dimethylsilyl)ferrocene (c).
Fig. 6 The simultaneous TGA and mass spectrometry results of ferrocene-modified
PDVB microspheres (a) and original PDVB microspheres (b).
Fig. 7 The XPS spectra of the synthesized Si-C-Fe hybrid microspheres.
Fig. 8 TEM images of the synthesized Si-C-Fe hybrid microspheres at low (a) and
high (b) magnification; (c) is local magnification of (b).
Fig. 9 Nitrogen adsorption-desorption isotherms and the corresponding pore-size
distributions for the synthesized Si-C-Fe hybrid microspheres.
Fig. 10 Plots of magnetization, M, versus external applied magnetic field, H, at 300
K, for the synthesized Si-C-Fe hybrid microspheres.
Fig. 11 (a) UV-vis absorption spectra during Si-C-Fe hybrid microspheres promoted
reduction of 4-NP; (b) At/A0 as a function of reaction time; (c) linear relationship of
ln(At/A0) as a function of time; and (d) the recyclability of the Si-C-Fe hybrid
microspheres.
Fig. 12 The calculated structures of 4-NP, sp2 carbon domain and their mixture using
DFT.
26/43

Journal of Materials Chemistry A
Page 28 of 44
View Article Online
DOI: 10.1039/C7TA01156C
Table 1 The binding energy (B.E.) of chemical bonds of ferrocene-modified PDVB microspheres.
Si 2p
B.E. (eV)
C 1s
B.E. (eV)
Fe 2p
Bond
Si-C
C-Si-O
--
Bond
C=C
Bond
C-OH
COO
π-π*
B.E. (eV)
286.8
Bond
B.E. (eV)
708.0
720.7
--
100.3
102.1
--
284.5
285.2
286.1
Fe 2p3/2
Fe 2p1/2
--
C-C
289.1
C*-C=O
290.8
27/43

Page 29 of 44
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C7TA01156C
Table 2 The binding energy (B.E.) of chemical bonds of the synthesized Si-C-Fe hybrid
microspheres.
Si 2p
C 1s
Fe 2p3/2
Bond B.E. (eV)
Bond B.E. (eV)
Bond
C-Si
B.E. (eV)
283.1
Bond
B.E. (eV)
287.1
Si-C
Si-O
--
101.1
102.7
--
C-O-Si
C=O
Fe0
Fe2+
707.5
709.9
712.0
C=C
C-C
284.1
288.3
285.0
COOH
289.5
FeOOH
C-OH
285.8
28/43