Fe-doped H3PMo12O40 immobilized on covalent organic frameworks (Fe/PMA@COFs): A heterogeneous catalyst for the epoxidation of cyclooctene with H2O2

Article abstract of DOI:10.1039/c8ra10388g

Covalent organic frameworks (COFs) have arisen as one kind of devisable porous organic polymer that has attracted immense attention in catalytic applications. In this work, we prepared cost-effective imine-based COFs (COF-300, COF-LZU1 and CIN-1) via a reaction kettle operated in place of a traditional sealed Pyrex tube. Then, phosphomolybdic acid (PMA) and iron ions were immobilized on the COF supports by impregnation; the resulting frameworks were denoted as Fe/PMA@COFs (Fe/PMA@COF-LZU1, Fe/PMA@CIN-1 and Fe/PMA@COF-300). A series of characterization results demonstrated that the PMA and iron ions were uniformly dispersed on the surface/cavities of the COFs. The catalytic properties of the obtained Fe/PMA@COFs were investigated in the epoxidation of cyclooctene with H₂O₂ as the oxidant. The experimental results show that the Fe/PMA@CIN-1 composite can act as an efficient heterogeneous catalyst for the epoxidation of cyclooctene. The intramolecular charge transfer between the COFs and the dual sites (PMA and Fe ions), the spatial structure and the nitrogen content of the COFs played critical roles in dispersing and stabilizing the active species, which are closely connected with the activity and stability of the catalysts. A novel efficient heterogeneous catalyst for the epoxidation of olefins via a simple and cost-effective process is provided, and this experiment demonstrates the notable application prospects of the covalent organic skeleton as a catalyst support.

Full text of DOI:10.1039/c8ra10388g

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Fe-doped H PMo O immobilized on covalent
3
12 40
organic frameworks (Fe/PMA@COFs):
a heterogeneous catalyst for the epoxidation of
cyclooctene with H O
Cite this: RSC Adv., 2019, 9, 4884
2
2
ab
a
ab
a
a
a
Dandan Yu,† Wenxiu Gao,†* Shuyu Xing, Lili Lian, Hao Zhang, Xiyue Wang
a
and Dawei lou
*
Covalent organic frameworks (COFs) have arisen as one kind of devisable porous organic polymer that has
attracted immense attention in catalytic applications. In this work, we prepared cost-effective imine-based
COFs (COF-300, COF-LZU1 and CIN-1) via a reaction kettle operated in place of a traditional sealed Pyrex
tube. Then, phosphomolybdic acid (PMA) and iron ions were immobilized on the COF supports by
impregnation; the resulting frameworks were denoted as Fe/PMA@COFs (Fe/PMA@COF-LZU1, Fe/
PMA@CIN-1 and Fe/PMA@COF-300). A series of characterization results demonstrated that the PMA and
iron ions were uniformly dispersed on the surface/cavities of the COFs. The catalytic properties of the
2 2
obtained Fe/PMA@COFs were investigated in the epoxidation of cyclooctene with H O as the oxidant.
The experimental results show that the Fe/PMA@CIN-1 composite can act as an efficient heterogeneous
catalyst for the epoxidation of cyclooctene. The intramolecular charge transfer between the COFs and
the dual sites (PMA and Fe ions), the spatial structure and the nitrogen content of the COFs played
critical roles in dispersing and stabilizing the active species, which are closely connected with the activity
and stability of the catalysts. A novel efficient heterogeneous catalyst for the epoxidation of olefins via
a simple and cost-effective process is provided, and this experiment demonstrates the notable
application prospects of the covalent organic skeleton as a catalyst support.
Received 19th December 2018
Accepted 24th January 2019
DOI: 10.1039/c8ra10388g
rsc.li/rsc-advances
0
Pd nanoparticles, named Pd-trzn-COF, as a good hydrolytically
Introduction
17
stable catalyst for multi-fold Heck and C–C coupling reactions.
2
Covalent organic frameworks (COFs) are a class of crystalline An sp -rich non-polar phenyl framework and Schiff linkages
organic porous materials that are constructed from light serve as a polar matrix mimicking the environment typically
18
elements and linked by covalent bonds to create predesigned present in homogeneous molecular catalysts. Bhaumik and
1,2
skeletons and nanopores. By means of the organic functional coworkers used a nitrogen-rich porous covalent imine network
group of the framework, a multitude of active sites are intro- (CIN-1) material as an efficient catalytic support for C–C
19
duced into the porous network to develop COFs with diverse coupling reactions. The stability of the catalyst is due to the
3
–6
applications, such as gas storage and separation,
energy intimate contact between the nitrogen-rich organic support and
According to Pd nanoparticles.
research, imine-based COFs are highly stable in water and
The epoxidation of olens is an important chemical indus-
7
8–10
11–14
conversion, optoelectronics,
and catalysis.
common organic solvents; moreover, coordination chemistry trial process. The preparation of more efficient heterogeneous
demonstrates that imine-type ligands are versatile in incorpo- catalysts for the aerobic epoxidation of olens by an environ-
1
5,16
rating a variety of metal ions.
COFs have been used as excellent candidates for catalytic in recent years. On the one hand, the seldomly employed oxygen
applications.
Several kinds of imine-based mentally benign route has attracted considerable study interest
12,15,17,18
Vaidhyanathan's
group
reported oxidant hydrogen peroxide (H O ) is the most popular
2 2
a nitrogen-rich and triazine-based COF (trzn-COF) loaded with environment-friendly reagent. Different kinds of heterogeneous
catalysts have been widely investigated. Polyoxometalates
(
POMs) are one class of efficient epoxidation catalysts of
12,20,21
a
olens.
Noritaka Mizuno and his research group found
Department of Analytical Chemistry, Jilin Institute of Chemical Technology, 45
Chengde Street, Jilin 132022, P. R. China. E-mail: dwlou@hotmail.com
that peroxotungstate immobilized on dihydroimidazolium-
is an efficient heterogeneous
epoxidation catalyst of various olens with H O . On the other
2 2
b
Department of Physical Chemistry, Jilin University, 2699 Qianjin Street, Changchun based ionic liquid-modied SiO
2
1
30012, P. R. China
22
†
These authors contributed equally.
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ꢀ
hand, numerous transition metal complexes of iron have been added to the above solutions with stirring at 80 C. Aer 12 h of
23–26
investigated as alkene epoxidation catalysts.
Costas and stirring, a certain concentration of Fe(NO ) $9H O solution was
3 3 2
coworkers developed a series of Fe-pdp catalysts with chiral added to the reaction ask, and the mixture was stirred
ꢀ
tetradentate ligands for the epoxidation of a wide range of continuously to guarantee reaction for 24 h at 80 C. The
27
olens. In this work, iron coordination complexes bearing product was ltered off, washed with water and ethanol, and
ꢀ
tetradentate aminopyridine ligands are shown to constitute dried at 80 C overnight under vacuum to afford the Fe/
a privileged platform for epoxidation. Carboxylic acid can be PMA@COFs.
envisioned as a valuable partner to modulate the structure of
oxygen atom species in reactions where peroxides are used as
Results and discussion
oxidants.
Previously, Jia and his group prepared various POMs or Characterization techniques
transition metal complex-based heterogeneous catalysts for
FT-IR spectra were recorded on an Interspec 200-X FTIR spec-
trometer in the range 3500–500 cm . XRD patterns were
28–34
olen epoxidation.
As a follow-up work, in this study, we
ꢁ1
prepared cost-effective imine-based COFs (COF-LZU1, CIN-1,
and COF-300) using a reaction kettle. Then, phosphomolybdic
acid (PMA) and iron ions were immobilized onto the COF
supports by impregnation, and the resulting materials were
denoted as Fe/PMA@COFs (Fe/PMA@COF-LZU1, Fe/
PMA@CIN-1, and Fe/PMA@COF-300). The physicochemical
properties of the Fe/PMA@COFs were determined by
a comprehensive range of characterization techniques, such as
Fourier-transform infrared (FT-IR) spectroscopy, X-ray powder
diffraction (XRD), scanning electron microscopy (SEM), trans-
collected using a Bruker D8 Advance X-ray powder diffractom-
eter in reectance Bragg–Brentano geometry employing Ni-

ltered Cu Ka line-focused radiation at 1600 W (40 kV, 40 mA)
power. N adsorption/desorption isotherms were measured at
2
liquid nitrogen temperature using a Micromeritics ASAP 2020
automated adsorption analyzer. All samples were degassed at
393 K for 12 h before measurements. The surface areas were
calculated using the Brunauer–Emmett–Teller (BET) method
using the adsorption data in the relative pressure range of 0.05–
0.2. Total pore volumes were derived at the relative pressure of
2
mission electron microscopy (TEM), N adsorption/desorption
P/P0 ¼ 0.99, assuming full surface saturation with nitrogen.
and X-ray photoelectron spectroscopy (XPS), and their cata-
lytic performances were tested in the epoxidation of cyclooctene
with H O as oxidant. The experimental results show that the
Pore size distributions were calculated from the N adsorption
2
isotherms by non-linear density functional theory methods. The
2
2

eld-emission SEM images were obtained on an FEI Nova Nano
Fe/PMA@CIN-1 composite can act as an efficient heterogeneous
catalyst for the epoxidation of cyclooctene. The intramolecular
charge transfer between the COFs and the dual sites (Fe and
PMA ions), as well as the spatial structure and nitrogen content
of the COFs, played critical roles in dispersing and stabilizing
the active species, which are closely connected with the activity
and stability of the catalysts.
SEM 450. TEM and energy-dispersive X-ray spectrometry (EDS)
were carried out using a JEM-2100F electron microscope. XPS
measurements were performed on a Thermo ESCALAB 250
system with a Mg Ka source (1253.6 eV).
Material characterization
Fig. 2 shows the FT-IR spectra of the PMA, COFs, and Fe/
PMA@COFs. The characteristic peaks of the COFs in the
whole region presented good agreement with the literature-
Experimental
Preparation of imine-based COFs
15,19,34
reported results.
The existence of a strong C]N stretch-
ꢁ1
ing vibration at around 1619 cm is indicative of the formation
of imine bonds during reaction kettle operation. This result
conrms that the COFs (COF-LZU1, CIN-1 and COF-300) were
successfully synthesized by using the reaction kettle method.
Comparing the spectra of the Fe/PMA@COFs and COFs, the
COF was well conserved aer loading the PMA and Fe ions. The
apparent red shi of the C]N peak indicated the coordination
COF-LZU1, CIN-1, and COF-300 were prepared via a simple and
cost-effective process, using a reaction kettle (Teon-lined
stainless-steel autoclave) operated in place of a traditional
sealed Pyrex tube. The reaction monomers were transferred to
the reaction kettle and crystallization occurred at a lower
ꢀ
ꢀ
temperature (COF-LZU1, CIN-1, and COF-300: 120 C, 168 C
ꢀ
and 120 C, respectively). The other steps were performed
35
1
5,19,34
of Fe ions to imine N atoms in the framework. The charac-
according to procedures described in the literature.
Among them, the nitrogen content of COF-LZU1, CIN-1 and
COF-300 was 14.2%, 45% and 9.14%, respectively (Fig. 1).
ꢁ1
teristic absorption peak of P–O at 1064 cm in PMA shied to
a
ꢁ
1
around 1059 cm aer immobilization, indicating the chem-
12
ical interaction between PMA and the COFs. The characteristic
ꢁ
1
ꢁ1
peaks of Mo–O
b
at 968 cm , Mo–O
b
–Mo at 870 cm , and Mo–
Preparation of Fe/PMA@COFs
ꢁ1
O
c
–Mo at 798 cm partially overlapped with the absorption
Fe/PMA@COF complexes were prepared by the impregnation peaks of the COFs.
method. All the chemicals used for synthesis were of analytical Fig. 3 displays the XRD patterns of PMA, Fe(NO ) , COFs and
3
3
grade and commercially available. Ultrapure water was used in Fe/PMA@COFs. The main characteristic diffraction peaks of
all experiments. COFs (0.1 g) were dispersed in 20 mL of COF-LZU1, CIN-1 and COF-300 were preserved, indicating that
ultrapure water under ultrasonic irradiation for 1 h. Aerward, doping of PMA caused no destruction of the structure of the
3
a certain concentration of H PMo12O40 aqueous solution was support. The characteristic diffraction peaks of PMA and
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Fig. 1 Construction of (a) COF-LZU1, (b) CIN-1, and (c) COF-300.
Fig. 3 XRD spectra of PMA, COFs and Fe/PMA@COFs.
Fig. 2 FT-IR spectra of PMA, COFs and Fe/PMA@COFs.
Fe(NO
highly and molecularly dispersed within the surface and pores (Fig. 3c).
of the COF. With regard to the characteristic peaks of Fe/
Fig. 4 shows the SEM images of the COFs and Fe/
3 3
)
were absent in Fe/PMA@COFs, indicating that PMA is 300 framework aer introducing the PMA and Fe ions
38–41
PMA@COFs, a decreased intensity, increased width, and PMA@COFs. The morphology of the COFs prepared via the
signicant shis to high-angle regions were observed, sug- reaction kettle is similar to literature ndings (Fig. 4a, c and
1
5,19,34
gesting that several cavities were lled with the introduced e).
active substance.
The image of the Fe/PMA@COF-LZU1 composite shows
The appearance of the new low-angle peaks a layered-sheet morphology with a size of around 300 nm
in the Fe/PMA@COF-300 composites is similar to that observed (Fig. 4b).
36,37
12
in a previous report, and this nding should be related to the
The image of Fe/PMA@CIN-1 depicts spherical-like nano-
distribution of PMA units and slight transformation of the COF- particles of size ca. 40–60 nm (Fig. 4d). A smaller packing
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Fig. 6a–c show the HAADF-STEM images of the Fe/
PMA@COFs. As shown in the EDS mapping images, P and Mo
originated from the PMA units, whereas Fe came from the
loaded Fe ions (Fig. 6h, d and i). These images conrm that the
PMA units and Fe ions were uniformly distributed over the
whole composite. More Fe ions were also observed in Fe/
PMA@CIN-1 compared with Fe/PMA@COF-LZU1 and Fe/
PMA@COF-300 (Fig. 6b versus Fig. 6a and c). The Fe ions dis-
played a close relationship with the nitrogen content of the
carriers. From this nding, we assumed that the Fe ions were
loaded onto the COF by chemical reaction with C]N and
physical adsorption.
Fig. 7 shows the nitrogen adsorption–desorption isotherms
of the COFs and Fe/PMA@COFs. According to IUPAC classi-
cation, the COF-LZU1, CIN-1 and COF-300 samples exhibited
2 0 0
type IV isotherms. A steep N uptake at P/P < 0.01 and P/P > 0.8
characterized the micro- and macro-structure of the materials,
and the increased nitrogen uptake above a partial pressure of
0.2 in the isotherm indicated the presence of mesopores. These
characteristics show that the COFs prepared via the reaction
kettle are hierarchically porous. Compared with the COFs, the
BET surface areas and total pore volume of the Fe/PMA@COFs
notably decreased (Table 1). This phenomenon indicates that
certain amounts of PMA units and Fe ions were introduced not
only on the surface of the COFs but also into the cavities.
Moreover, signicant changes in the pore size distributions
suggest that the introduction of PMA units and Fe ions could
block or destroy the pores of the COFs.
Fig. 4 SEM images of (a) COF-LZU1, (b) Fe/PMA@COF-LZU1, (c) CIN-
1
, (d) Fe/PMA@CIN-1, (e) COF-300, and (f) Fe/PMA@COF-300.
Fig. 8 provides the XPS measurements. Fig. 8a displays the N
1
s spectra of the support CIN-1, PMA@CIN-1, and Fe/
structure of particles usually features a larger surface area and
better loading property. The Fe/PMA@COF-300 composite
shows a similar morphology to the grain shape of rice, achieving
better dispersion rather than agglomeration (Fig. 4f). From the
morphology observed in the SEM images, we can preliminarily
determine that the size of the COFs synthesized by the reactor
was uniform and well dispersed, and no visible evidence of the
accumulation of active species was found.
Fig. 5 displays the TEM images of Fe/PMA@COFs. Fe/
PMA@COF-LZU1 can be observed to have an eclipsed
layered-sheet arrangement (Fig. 5a and b). At rst, several
black spots were observed to be uniformly dispersed on the
composite surface at a certain magnication in the TEM
image. Lattice fringes can also be observed aer extended
irradiation, showing good agreement with the d spacing of the
PMA crystal planes (424), (225), (521), (434) and (305) (Fig. 5c).
Meanwhile, a similar phenomenon also occurred in Fe/
PMA@COF-300. Aer an extended irradiation time, the
crystal planes (512), (424), (306), (502), and (335) (PDF #46-
PMA@CIN-1. The binding energy (BE) of 399.2 eV is attrib-
uted to the nitrogen species in the imine groups of CIN-1. For
PMA@CIN-1 and Fe/PMA@CIN-1, the peak of N 1s shied to
a lower position, with values of 398.9 and 397.2 eV, respectively.
The N 1s peak moved toward to a lower level by 1 eV aer doping
Fe ions, further reecting the presence of an interaction
between Fe ions and the CIN-1 support. Combined with
infrared characterization, it was found that the doping of PMA
units and Fe ions is not merely a simple physical adsorption but
also a coordination of chemical bonds. The Fe 2p spectrum was
deconvoluted into one doublet Fe2p 1/2 at 723.1 eV and Fe2p 3/2
at 710.2 eV (Fig. 7b), which is attributed to the Fe oxidation
state. More importantly, compared with the pure iron oxide (BE
of approximately 710.8 and 724.2 eV),
toward a lower BE of Fe was observed in the catalyst
composite, and this result may be due to the interaction
between iron ions and the carrier.
3
+
45–48
a minimal shi
3
+
0
482 PMA) can be observed (Fig. 5i).
Catalytic properties
Notably, the morphology of COF-300 changed to a certain
extent aer introducing the PMA units and Fe ions, and a rela-
tively rough surface appeared over the composite particles
Fig. 5g and h). These phenomena imply that the dopant not
The catalytic performances of the Fe/PMA@COFs composites
were investigated in the epoxidation of cyclooctene with H O as
2 2
the oxidant. In order to ensure the accuracy of the experimental
data, the results in Table 2 were repeated ve times or more. Fe/
PMA@COF-LZU1, Fe/PMA@CIN-1 and Fe/PMA@COF-300
respectively yielded 69% (s.d. ¼ 2.4), 88% (s.d. ¼ 1.3) and
(
only dispersed on the outer surface of the carrier but also
participated in the recrystallization process of COF-300, which
42–44
is compatible with the carrier skeleton structure.
62% (s.d. ¼ 2.6) conversion values of cyclooctene with an
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Fig. 5 TEM images of (a–c) Fe/PMA@COF-LZU1, (d–f) Fe/PMA@CIN-1, and (g–i) Fe/PMA@COF-300.
Fig. 6 EDS images of (a) PMA/Fe/COF-LZU1, (b) PMA/Fe/CIN-1, and
c) PMA/Fe/COF-300.
(
ꢀ
extremely high selectivity of epoxide ($99%) aer 9 h at 80 C,
and no detectable side products were observed under the test
conditions (Table 2). PMA@COF-LZU1, PMA@CIN-1 and
PMA@COF-300 respectively yielded 49% (s.d. ¼ 2.3), 83% (s.d.
¼
1.4) and 52% (s.d. ¼ 2.5) conversion values of cyclooctene. For
comparison, the catalytic properties of PMA@COFs were also
tested. PMA@COF composites showed 5–20% lower cyclooctene
conversion values than the dual site catalyst Fe/PMA@COFs. Fig. 7
N
2
adsorption–desorption isotherms and pore size distribution
curve for (a) COF-LZU1, (b) Fe/PMA@COF-LZU1, (c) CIN-1, (d) Fe/
PMA@CIN-1, (e) COF-300, and (f) Fe/PMA@COF-300.
Among these catalysts, Fe/PMA@CIN-1 is the most efficient.
Moreover, the catalytic properties of Fe/PMA@CIN-1 were
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Table
1 Corresponding physicochemical properties of the as-
prepared samples
Pore size
[A]
Pore volume
2
ꢁ1
3
ꢁ1
˚
Sample
S
BET [m g
]
[cm g
]
COF-LZU1
Fe/PMA@COF-LZU1
CIN-1
Fe/PMA@CIN-1
COF-300
Fe/PMA@COF-300
207
35
246
77
284
56
82
23
144
49
36
32
0.44
0.14
0.89
0.17
0.25
0.13
Fig.
9
Reaction conditions: cis-cyclooctene: 1.0 mmol,
H
2
O :
2
ꢀ
1
.0 mmol, catalyst: 10 mg, solvent (CH
3
CN): 2 mL and 80 C.
2 2
of cyclooctene was catalyzed with H O as the oxidant. The
Fig. 8 X-ray photoelectron spectra of (a) N 1s and (b) Fe 2p.
catalyst was removed, and the conversion rate was measured. A
small amount of cyclooctene conversion was observed within
2
h aer separation of the solid catalyst Fe/PMA@COF-300 and
Table
2
Reaction conditions: cis-cyclooctene 1.0 mmol,
H
2
O
2
Fe/PMA@CIN-1. Aer 2 h, no further increase in conversion rate
was observed. This result may be due to the loss of the reactant
cis-cyclooctene and a slight shedding of the active species
during the separation operation, indicating the loss of a trace
amount of active species to the reaction medium and the
predominant heterogeneous catalysis. A relatively strong inter-
ꢀ
1
.0 mmol, catalyst 10 mg, solvent (CH
3
CN) 2 mL, 80 C, 9 h. All
selectivities for the epoxide are $99%
Selectivity
Substrate
Catalyst
Con. (%)
(%)
PMA@COF-LZU1
Fe/PMA@COF-LZU1
PMA@CIN-1
Fe/PMA@CIN-1
PMA@COF-300
Fe/PMA@COF-300
49
69
83
88
52
62
3+
3ꢁ
action is built between the dual-site units (Fe and PMo12
)
and COF frameworks by intramolecular charge transfer,
consistent with the previous characterization results. Therefore,
it was proved that the stability of Fe/PMA@COF-300 and Fe/
PMA@CIN-1 is high. On the contrary, the stability of Fe/
PMA@LZUI is poor and the conversion rate continues to
increase aer separation of the solid catalyst. Combining the
above catalytic data with the characterization results, it is clear
that the conguration of the covalent organic skeleton is closely
related to the stability of the catalysts. Fe/PMA@CIN-1
possesses an outstanding stability due to CIN-1 having a rich
nitrogen content, small particle unit, and large surface area.
Meanwhile, the 3-D structure of COF-300 can also assist in
inhibiting active substance doping, which possibly explains why
$99
Fe/PMA@CIN-1
58
$99
further explored for the epoxidation of cyclododecene. It was
found that this relatively bulky cyclododecene (with a kinetic
diameter of around 8 A) could also be converted to the corre-
˚
sponding epoxide over the dual site catalysts. These results
suggest that PMA and Fe ions are distributed throughout the
support, and most of them are easily accessible even for the
bulky olen. Combined with previous characterization, the
results indicate that both PMA units and Fe ions play a crucial
role in the catalytic process. The increased nitrogen content of
the carriers is benecial to introducing more Fe , thus
promoting the catalytic performance in the epoxidation
reaction.
As shown in Fig. 9, the stability of the Fe/PMA@COF catalysts
was investigated by leaching tests. In duplicate reactions, the
solid catalyst was separated by hot ltration, and the ltrate was
further stirred to study the continuing activity at the reaction
temperature. When using the Fe/PMA@COFs, the epoxidation
Fe/PMA@COF-300 showed
PMA@COF-LZU1 (Fig. 9).
a
higher stability than Fe/
Conclusions
3
+
In this work, we prepared imine-based COFs (COF-300, COF-
LZU1, and CIN-1) via a reaction kettle. PMA and iron ions
were immobilized onto the COF supports to form Fe/
PMA@COFs. A series of characterization methods veried that
PMA and Fe ions were uniformly dispersed on the surface/
cavities of the COFs. A relatively strong interaction was ach-
ieved between the dual-site units and COF frameworks. The
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experimental results show that the Fe/PMA@CIN-1 composite 14 P. Pachfule, A. Acharjya, J. Roeser, T. Langenhahn,
can act as an efficient heterogeneous catalyst for the epoxida-
tion of cyclooctene. The intramolecular charge transfer between
M. Schwarze, R. Schom ¨a cker, A. Thomas and J. Schmidt, J.
Am. Chem. Soc., 2018, 140, 1423–1427.
COFs and the dual-site units (Fe and PMA) and the spatial 15 S. Y. Ding, J. Gao, Q. Wang, Y. Zhang, W. G. Song, C. Y. Su
conguration and nitrogen content of the COFs have played and W. Wang, J. Am. Chem. Soc., 2011, 133, 19816–19822.
critical roles in dispersing and stabilizing the active species, 16 H. Zhang, X. Y. Wang, N. Li, J. H. Xia, Q. M. Meng, J. C. Ding
which are closely connected with the activity and stability of the and J. Lu, RSC Adv., 2018, 8, 34241.
catalysts. This experiment demonstrates the notable applica- 17 D. Mullangi, S. Nandi, S. Shalini, S. Sreedhala, C. P. Vinod
tion prospects of the covalent organic skeleton as a catalyst
carrier.
and R. Vaidhyanathan, Sci. Rep., 2015, 5(1), 1–10.
18 F. Wang, J. Mielby, F. H. Richter, G. H. Wang, G. Prieto,
T. Kasama, C. Weidenthaler, H. J. Bongard, S. Kegnæs,
A. F u¨ rstner and F. Sch u¨ th, Angew. Chem., Int. Ed., 2014,
Conflicts of interest
126, 8789–8792.
There are no conicts to declare.
19 M. K. Bhunia, S. K. Das, P. Pachfule, R. Banerjee and
A. Bhaumik, Dalton Trans., 2012, 41, 1304.
2
0 H. Kim, J. C. Jung, S. H. Yeom, K. Y. Lee and I. K. Song, J. Mol.
Catal. A: Chem., 2006, 248, 21–25.
Acknowledgements
This work was supported by the National Natural Science 21 Y. Leng, J. Wu, P. Jiang and J. Wang, Catal. Sci. Technol.,
Foundation of China (No. 21375046, 21605056), Project of
2014, 4, 1293.
Science and Technology Development of Jilin Province (No. 22 K. Yamaguchi, C. Yoshida, S. Uchida and N. Mizuno, J. Am.
0140203013GX, 2013C041), and Plan for Science and Tech- Chem. Soc., 2005, 127(2), 530–531.
nology Innovation Developing Project of Jilin City (No. 23 D. Vidal, M. Costas and A. Lle ´o , ACS Catal., 2018, 8, 3667–
2
201831757). Financial support received from the Key Laboratory
3672.
of Fine Chemicals of Jilin Province is also acknowledged.
24 W. Nam, H. J. Han, S. Y. Oh, Y. J. Lee, M. H. Choi, S. Y. Han,
C. Kim, S. K. Woo and W. Shin, J. Am. Chem. Soc., 2000, 122,
8
677–8684.
Notes and references
2
5 F. Yan, J. W. Munos, P. H. Liu and H. W. Liu, Biochemistry,
1
2
3
4
5
6
7
8
9
A. P. C ˆo t ´e , A. I. Benin, N. W. Ockwig, M. O'Keeffe,
A. J. Matzger and O. M. Yaghi, Science, 2005, 310, 1166.
F. J. Uribe-Romo, C. J. Doonan, H. Furukawa, K. Oisaki and
O. M. Yaghi, J. Am. Chem. Soc., 2011, 133, 11478–11481.
H. Furukawa and O. M. Yaghi, J. Am. Chem. Soc., 2009,
2006, 45, 11473–11481.
26 S. Bhattacharjee, T. J. Dines and J. A. Anderson, J. Phys.
Chem. C, 2008, 112, 14124–14130.
27 O. Cuss ´o , J. Serrano-Plana and M. Costas, ACS Catal., 2017,
7, 5046–5053.
28 J. Du, J. Yu, J. Tang, J. Wang, W. Zhang, W. R. Thiel and
M. Jia, Eur. J. Inorg. Chem., 2011, 2361–2365.
29 H. Gao, J. Yu, J. Du, H. Niu, J. Wang, X. Song, W. Zhang and
M. Jia, J. Cluster Sci., 2014, 25, 1263–1272.
1
31(25), 8875–8883.
Y. Pramudya and J. L. Mendoza-Cortes, J. Am. Chem. Soc.,
016, 138(46), 15204–15213.
J. L. Mendoza-Cortes, S. S. Han, H. Furukawa, O. M. Yaghi
2
and W. A. Goddard, J. Phys. Chem. A, 2010, 114, 10824–10833. 30 J. Wang, Y. Zou, Y. Sun, M. Hemgesberg, D. Schaffner,
W. C. Song, X. K. Xu, Q. Chen, Z. Z. Zhuang and X. H. Bu,
Polym. Chem., 2013, 4, 4690–4696.
H. B. Aiyappa, J. Thote, D. B. Shinde, R. Banerjee and 31 K. Li, J. Wang, Y. Zou, X. Song, H. Gao, W. Zhu, W. Zhang,
S. Kurungot, Chem. Mater., 2016, 28(12), 4375–4379. J. Yu and M. Jia, Appl. Catal., A, 2014, 482, 84–91.
L. Chen, K. Furukawa, J. Gao, A. Nagai, T. Nakamura, Y. Dong 32 X. Song, W. Zhu, K. Li, J. Wang, H. Niu, H. Gao, W. Gao,
and D. Jiang, J. Am. Chem. Soc., 2014, 136(28), 9806–9809.
W. Zhang, J. Yu and M. Jia, Catal. Today, 2015, 259, 59–65.
S. Wan, F. G ´a ndara, A. Asano, H. Furukawa, A. Saeki, 33 X. Song, W. Zhu, Y. Yan, H. Gao, W. Gao, W. Zhang and
S. K. Dey, L. Liao, M. W. Ambrogio, Y. Y. Botros, X. Duan, M. Jia, J. Mol. Catal. A: Chem., 2016, 413, 32–39.
S. Seki, J. F. Stoddart and O. M. Yaghi, Chem. Mater., 2011, 34 F. J. Uribe-Romo, J. R. Hunt, H. Furukawa, C. Kl ¨o ck,
H. Gao, X. Song, W. Zhang, M. Jia and W. R. Thiel, Chin. J.
Catal., 2014, 35532–35539.
2
3(18), 4094–4097.
0 Q. Xu, S. Tao, Q. Jiang and D. Jiang, J. Am. Chem. Soc., 2018,
40(24), 7429–7432.
M. O'Keeffe and O. M. Yaghi, J. Am. Chem. Soc., 2009, 131,
4570–4571.
35 M. K. Bhunia, S. K. Das, P. Pachfule, R. Banerjee and
A. Bhaumik, Dalton Trans., 2012, 41, 1304.
36 Z. Karimi, A. R. Mahjoub and F. Davari Aghdam, Inorg. Chim.
Acta, 2009, 362, 3725–3730.
1
1
1
1
1 D. B. Shinde, S. Kandambeth, P. Pachfule, R. R. Kumar and
R. Banerjee, Chem. Commun., 2014, 21(2), 7944–7952.
2 W. Gao, X. Sun, H. Niu, X. Song, K. Li, H. Gao, W. Zhang,
J. Yu and M. Jia, Microporous Mesoporous Mater., 2015, 213, 37 Z. Karimi, A. R. Mahjoub and S. M. Harati, Inorg. Chim. Acta,
9–67. 2011, 376, 1–9.
3 H. Li, Q. Pan, Y. Ma, X. Guan, M. Xue, Q. Fang, Y. Yan, 38 W. Łuzny and M. Hasik, Solid State Commun., 1996, 99, 685–
V. Valtchev and S. Qiu, J. Am. Chem. Soc., 2016, 138, 14783– 689.
4788.
5
1
1
4890 | RSC Adv., 2019, 9, 4884–4891
This journal is © The Royal Society of Chemistry 2019

View Article Online
Paper
RSC Advances
3
9 E. S. Pomarza n´ ska, M. Hasik, W. Turek and A. Pro n´ , J. Mol. 44 J. Li, X. D. Yang, C. Y. Bai, Y. Tian, B. Li, S. Zhang, X. Y. Yang,
Catal. A: Chem., 1996, 114, 267–275.
0 S. Bureekaew, H. Sato, R. Matsuda, Y. Kubota, R. Hirose,
S. D. Ding, C. Q. Xia, X. Y. Tan, L. J. Ma and S. J. Li, J. Colloid
Interface Sci., 2015, 437, 211–218.
4
J. Kim, K. Kato, M. Takata and S. Kitagawa, Angew. Chem., 45 X. Liang, R. Yang, G. Li and C. Hu, Microporous Mesoporous
Int. Ed., 2010, 49, 7660–7664. Mater., 2013, 182, 62–72.
1 T. K. Maji, R. Matsuda and S. Kitagawa, Nat. Mater., 2007, 6, 46 S. Yang, G. Liang, A. Gu and H. Mao, Appl. Surf. Sci., 2013,
42–148. 285, 721–726.
2 X. Feng, X. S. Ding and D. L. Jiang, Chem. Soc. Rev., 2012, 41, 47 N. S. McIntyre and D. G. Zetaruk, Anal. Chem., 1977, 49,
010–6022. 1521–1529.
3 S. Wan, F. G ´a ndara, A. Asano, H. Furukawa, A. Saeki, 48 L. Sun, Y. Y. Cai, T. Ji and G. Y. Zhang, RSC Adv., 2018, 8,
4
4
4
1
6
S. K. Dey, L. Liao, M. W. Ambrogio, Y. Y. Botros,
X. F. Duan, S. Seki, J. F. Stoddart and O. M. Yaghi, Chem.
Mater., 2011, 23, 4094–4097.
35337.
This journal is © The Royal Society of Chemistry 2019
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