High Catalytic Performance of Mesoporous Dual Br?nsted Acidic Ternary Poly (Ionic Liquids) for Friedel-Crafts Alkylation

Article abstract of DOI:10.1002/aoc.5180

A newfangled cross-linked dual Br?nsted acidic ternary mesoporous poly (ionic liquids)(MPILs) with mesoporous structure was successfully synthesized with divinylbenzene as cross linker, 1-vinyl-3-butyl imidazole bromide and sodium p-styrene sulfonate as functional group through an ordinary post-modification method and anion exchange process. A sponge-like mesoporous tunnel structure was observed and the obtained P (BVS-SO₃H)-SO₃CF₃ sample appeared a relatively high thermal stability, a large surface area (up to 286.8?m²/g) and great pore volume (0.73?cm³/g). The abundant dual acidic group of sulfonic acid and trifluoromethanesulfonic acid of the composite in the polymer framework impart Br?nsted acidity. For the sake of demonstrating our claims, the sample has been used as a novel solid acid catalyst for the reaction of alkylation of o-xylene with styrene to 1-diphenylethane (PXE). Under optimal reaction conditions (reaction under 120?°C for 3?hr, catalyst amount was 0.5?wt% of the reaction system, and the mass ratio of o-xylene/styrene was 7.5:1, a 100% conversion of styrene and 93.7% PXE yield was acquired. After four times recycle, the yield remains 53.3%. Comparing with the commercial liquid acid catalyst, it processing a higher catalytic property and recyclability. Moreover, this fresh dual acidic heterogeneous catalyst owning a promising future applied in other acidic catalytic reactions and provide a new method to modify catalyst.

Full text of DOI:10.1002/aoc.5180

Received: 12 May 2019
DOI: 10.1002/aoc.5180
Revised: 24 July 2019
Accepted: 24 July 2019
F U L L P A P E R
High Catalytic Performance of Mesoporous Dual Brønsted
Acidic Ternary Poly (Ionic Liquids) for Friedel‐Crafts
Alkylation
Xiao Sha1,2
Jiehua Bao1,2
| Xiaoli Sheng1,2 | Yuming Zhou1,2 | Beibei Wang1,2 | Yonghui Liu1,2
|
1 School of Chemistry and Chemical
Engineering, Southeast University,
Nanjing 211189, China
2 Jiangsu Optoelectronic Functional
Materials and Engineering Laboratory,
Nanjing 211189, China
A newfangled cross‐linked dual Brønsted acidic ternary mesoporous poly (ionic
liquids)(MPILs) with mesoporous structure was successfully synthesized with
divinylbenzene as cross linker, 1‐vinyl‐3‐butyl imidazole bromide and sodium
p‐styrene sulfonate as functional group through an ordinary post‐
modification method and anion exchange process. A sponge‐like mesoporous
tunnel structure was observed and the obtained P (BVS‐SO3H)‐SO3CF3 sample
appeared a relatively high thermal stability, a large surface area (up to
286.8 m2/g) and great pore volume (0.73 cm3/g). The abundant dual acidic
group of sulfonic acid and trifluoromethanesulfonic acid of the composite in
the polymer framework impart Brønsted acidity. For the sake of demonstrating
our claims, the sample has been used as a novel solid acid catalyst for the reac-
tion of alkylation of o‐xylene with styrene to 1‐diphenylethane (PXE). Under
optimal reaction conditions (reaction under 120 °C for 3 hr, catalyst amount
was 0.5 wt% of the reaction system, and the mass ratio of o‐xylene/styrene
was 7.5:1, a 100% conversion of styrene and 93.7% PXE yield was acquired.
After four times recycle, the yield remains 53.3%. Comparing with the commer-
cial liquid acid catalyst, it processing a higher catalytic property and recyclabil-
ity. Moreover, this fresh dual acidic heterogeneous catalyst owning a promising
future applied in other acidic catalytic reactions and provide a new method to
modify catalyst.
Correspondence
Xiaoli Sheng and Yuming Zhou, School of
Chemistry and Chemical Engineering,
Southeast University, Nanjing 211189,
China; Jiangsu Optoelectronic Functional
Materials and Engineering Laboratory,
Nanjing 211189, China.
Email: xlsheng@seu.edu.cn;
ymzhou@seu.edu.cn
Funding information
“Six Talents Pinnacle Program’’ of Jiangsu
Province of China, Grant/Award Number:
JNHB‐006; Fund Project for Transforma-
tion of Scientific and Technological
Achievements of Jiangsu Province of
China, Grant/Award Number:
BA2014100; Qing Lan Project of Jiangsu
Province, Grant/Award Number:
1107040167; Innovative Research Group
Project of the National Natural Science
Foundation of China., Grant/Award
Numbers: 21376051, 51673040, 21306023
and 21676056
KEYWORDS
dual‐acid catalysis, functional, mesoporous structure, polymers
1 | INTRODUCTION
Typically, Brønsted acidic, such as H2SO4, HCl and HF
are usually used as the catalyst of the reaction[4]. However,
The alkylation of o‐xylene with styrene is a significant
industrial Friedel‐Crafts reaction, the research has last
for a very long time for the product phenylxylylethane
(PXE) exhibits a great range of application, such as the
pressure‐sensitive record materials, a heating medium,
an electric‐insulating oil and other applied materials.[1–3]
these traditional catalysts are difficult to separate and
always show a low active performance, which make them
high‐cost catalysts. In order to overcome these drawbacks,
it is significant and urgent to discover an environment‐
friendly heterogeneous solid catalysts for this Friedel‐
Crafts reaction.
Appl Organometal Chem. 2019;e5180.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.5180

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SHA ET AL.
Increasing attention has recently been drawn to ionic
activity of the catalyst which is attribute to the perfor-
mance of the target reaction of alkylation of o‐xylene with
styrene. Furthermore, a series of comparative experi-
ments were put into effect to investigate the effect of dif-
ferent molar ratio of p‐styrenesulfonate, and the amount
of catalysts, the reaction condition of temperature and
recycle times on the alkylation of o‐xylene with styrene.
The results of this paper may provide a promising insight
in to the acidic reaction field.
liquids (ILs) because of its broad applicability, from sol-
vent to catalysis chemistry with the properties of unique
combination ability, low flammability, negligible vapor
pressure, controllable acidity and basicity, high ionic con-
ductivity and so on.[5] One important utilization of ILs is
that they display wide applications as a catalyst in many
organic reactions. However, the liquid state of ionic liq-
uids limits their recyclability which may attribute to the
drastic loss in catalytic activity. Meanwhile, the low sur-
face area of current homogeneous catalyst of ionic liquids
catalysts limits their catalytic efficiency and is more diffi-
cult to separate from the reaction system than heteroge-
neous ones, which leading to their low competitiveness
in industrial applications. Synthesis of a heterogeneous
catalyst with porous structure would be a short‐cut way
to obtain better catalytic efficiency and recycling perfor-
mance than current ionic liquids catalysts.
2 | EXPERIMENTAL
2.1 | Materials
All chemicals and solvents were commercially available
and used without any purification. 1‐butyl‐3‐
vinylimidazolium bromide (99 wt%) (B), 1,4‐diethenyl‐
benzen(80 wt%)(V), 2,2′‐azobis (2‐methylpropionitrile)
(AIBN) were purchased from Aladdin Industrial Corpora-
tion, anhydrous ether (AR), sodium p‐styrenesulfonate(-
S), 1,4‐epoxy‐butan (AR) and ethanol absolute (AR)
were purchased from Sinopharm Chemical Reagent Co.,
Ltd. o‐xylene, styrene and tetrahydrofuran (THF) were
supplied by Shanghai Lingfeng Chemical Reagent Co.,
Ltd.
As heterogeneous catalyst, solid acidic catalyst has
been widely used in esterification[6], hydrogenation reac-
tion[7], Beckmann rearrangements[8], Friedel‐Crafts acyl-
ation reaction. Mesopores poly (ionic liquids)(MPILs), as
a special type of ionic liquids (ILs),is composed of ILs
containing polymerizable units, crosslinkers and other
functional groups with mesoporous structure[9,10]. Thus,
MPILs show some unique properties which not only com-
bined that of ILs and polymer materials, but also allowed
for the existence of fresh properties for a wide range of
applications in separations, catalysis and electricity[4,11–
15]. The preferences of MPILs compared to the corre-
sponding homogeneous ILs are inspired by the superiori-
2.2 | Preparation of catalysts
ties of easy separation and controllable structure[16]
.
2.2.1 | Preparation of mesoporous P (BVS‐
SO3Na)
Theoretically, the exchange of intrinsic anions in MPILs
by functional ones can bring some novel performances
and constitute porous structure[3,11,17–24]. For example,
Suo[25] has prepared a family of new mesoporous MPILs
containing long chain carboxylate ILs as anion functional
group through a methodology to create mesopores struc-
ture via microphase separation. In our previous work,
As a typical run for compound of P (BVS‐SO3Na), 2.44 g
(15 mmol) of 1,4‐divinyl‐benzene (D) was added into a
solution containing 4.0 ml of deionized water followed
by addition of 20 ml of THF, then add the appropriate x
amount of sodium p‐styrene sulfonate (x = 1.5, 2.0, 2.5,
where x represents the molar ratio of sodium p‐styrene
sulfonate/1‐vinyl‐3‐butyl imidazole bromide/DVB at
x/1.0/2.0.) was introduced in a 100 ml Schlenk flask.
After stirring at ambient temperature for 2 hr, 0.16 g 2,
2′‐azobis (2‐methylpropionitrile) (AIBN) was added into
the above mixture and continue stirring under ambient
temperature for 3 hr. Then, the mixture was deoxygen-
ated for 30 min and backfilled with N2 continually,
followed by vigorous magnetic stirring at 80 °C for
18 hr. After evaporation of the solvents at room tempera-
ture, the P (BVS‐SO3Na) sample was washed with a large
amount of EtOH before centrifugal separation, and dried
under vacuum at 343 K for 24 hr. Then, the resultant yel-
low powder was ground for further applications.
we
have
successfully
synthesized
alkoxysilyl‐
functionalized polymer ionic liquid by solvothermal and
post‐synthesis method where ILs act as both template
and silica source[26]. All these reports can strongly dem-
onstrate the theory that the type of anion in MPILs can
greatly influence their functionality and performance.
In this work, a newfangled dual Brønsted acidic MPILs
has been reported via a facile post‐modification method,
in which ILs and sulfonic functional monomers were
copolymerized by DVB as cross‐linker, sodium p‐
styrenesulfonate as a functionl group and then ‐SO3CF3
group can be anchored into polymer chains by anion
exchange. The ‐SO3CF3 and ‐SO3H groups within the
samples can significantly increase the effective acidic

SHA ET AL.
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(BJH) model, respectively. a A Rigaku ThermoPlus
TG8120 system was used under a rate of 10 °C min−1 in
air to excute Thermo Gravimetric Analysis (TGA).
2.2.2 | Preparation of mesoporous P (BVS‐
SO3H)
To get a P (BVS‐SO3H) sample, the P (BVS‐SO3Na) sam-
ple was further ion‐exchanged by using 2 M sulfuric acid.
As a typical route, 1.5 g of P (BVS‐SO3 Na) was dispersed
into 15 ml anhydrous ethanol solution, then 15 ml of 2 M
H2SO4 was added with vigorous magnetic stirring by con-
stant pressure funnel. After stirring for 24 hr under ambi-
ent temperature, the sample was treated by centrifugation
and washed with ethyl ether until the supernatant was
neutral and repeat this step for three times. Then, dried
the sample under high vacuum at 343 K for 24 hr, finally
P (BVS‐SO3H) was obtained.
2.4 | Determination of alkylation catalyst
activity
The alkylation of o‐xylene and styrene was used to evalu-
ate the catalytic performance of the prepared products.
Through a typical procedure, 30 g o‐xylene, 4 g styrene,
and catalyst (x wt%, where x represents relative to the
weight of the whole reaction system) were blended in a
250 ml flask. Then, we heated the mixture to 120 °C in
an oil bath with continued magnetic stirring for 3 hr
under common pressure. And after the procedure, cata-
lyst sample was recycled through vacuum filter procedure
and dry at 60 °C for 12 hr. The catalyst performance of
the samples were detected by gas chromatograph, GC
9890A.
2.2.3 | Preparation of mesoporous P (BVS‐
SO3H)‐SO3CF3
Firstly, 1.0 g of P (BVS‐SO3Na) was added to the solution
with 25 mL of toluene and 3 ml HSO3CF3 and string for
24 hr at ambient temperature and filter to remove the sol-
vent. Then, wash the sample with anhydrous ether solu-
tion and dry at 333 K for 6 hr. After that, repeat this
operation once again, the P (BVS‐SO3H)‐SO3CF3 sample
was obtained finally.
3 | RESULT AND DISCUSSION
3.1 | Catalysts characterization
It can be observed in the Figure 1 A that the different
molar ratio of sodium p‐styrene sulfonate of the P (BVS‐
SO3Na) never influence the peaks in the FT‐IR spectra.
Peaks at 2970 and 2920 cm−1 are associated with the C–
H stretching of C–H bending of CH3 and CH2 functional
group respectively. Peaks at 1449, 789 and 722 cm−1 are
associated with in‐plane and out‐of‐plane rings of C–H
bending within CH3 and CH2 functional group The bands
at around 1633 and 1224 cm−1 is a to the are derived from
C=N and C–N stretching for imidazole. Peaks at 1157and
1041 cm−1 represents the asymmetric and symmetric
stretching of the O=S=O bonds within sulfonic
groups[27,28]. In Figure 1 B, the new bands at around
2.3 | Characterization of catalysts
The construction and morphology of the catalysts were
examined through Fourier transform infrared (FT‐IR,
FTIR‐6700), scanning electron microscopy (SEM, FEI
Inspect F50) and transmission electron microscopy
(TEM, JEOL, JEM‐2100). The N2 adsorption/desorption
isotherms were recorded on an ASAP 2020 apparatus
(Micromertics USA). And the specific surface area and
pore size distributions were performed using Brunauer–
Emmett–Teller (BET) and Barrett–Joyner–Halenda
FIGURE 1 A: FT‐IR spectra of different ratio of P (BVS‐ SO3Na), a) x = 1.5, b) x = 2, c) x = 2.5; B: FT‐IR spectra of d) P (BVS‐SO3H) and e)
P (BVS‐SO3H)‐SO3CF3

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SHA ET AL.
1597, 1127, 791, 663 cm−1 is associated with the existence
of S‐O and C‐F in ‐SO3CF3 functional group respectively.
And the peak of benzene ring in P (BVS‐SO3H) is red-
shift, which indicate the much more stable combination
of the group. While the peaks at 2335 cm−1 in Figure 1
A and peak of benzene ring at 2364 cm−1 in Figure 1 B
is commonly attribute to the CO2 in the atmosphere. All
the above results indicate the oxidation and the successful
introduction of ‐SO3CF3 groups onto the PILs through the
anion exchange route.
As demonstrated in Figure 2, the P (BVS‐SO3Na) and P
(BVS‐SO3H)‐SO3CF3 sample exhibit a type‐IV curve with
a diminutive hysteresis loop of type H1 in the relative
pressure (P/P0) region of 0.5–1.0, which can indicate the
existence of mesopores within the samples. Accordingly,
the pore size of P (BVS‐SO3Na) is mainly distributed at
20 nm and that of P (BVS‐SO3H)‐SO3CF3 was distributed
at around 35 nm. The BET data were listed in the Table 1.
And the BET surface of P (BVS‐SO3Na) and P (BVS‐
SO3H)‐SO3CF3 are 417.5cm2/g and 286.9cm2/g, respec-
tively. The smaller surface area of P (BVS‐SO3H)‐SO3CF3
is attributed to the partial blockage and destruction of the
mesopores by acid in anion exchange. While the P (BVS‐
SO3H) sample shows a surprisingly low BET surface of
17.89cm2/g and there is almost no mesopores pore in
the P (BVS‐SO3H).
As we can observe in the Figure 3, P (BVS‐SO3Na) and
P (BVS‐SO3H)‐SO3CF3 show an analogous sponge‐like
porous structure with a large amount of mesoporous
architecture within the samples which could thanks to
the solvent extraction procedure which manufacture a
plethora of mesopores within the sample. The
crosslinking of the monomers and the solvent
extravagation procedure construct the mesoporous struc-
ture. Nevertheless, the P (BVS‐SO3Na) exhibits a more
solid construction than P (BVS‐SO3H)‐SO3CF3 which
may as a result of the process of ion exchange of
CF3SO3−. In picture (b), it can be easily observed that
the porous structure is blocked and is different from the
TABLE 1 The Textural Parameters of Various Polymer Acid
Catalysts
a
b
c
SBET
DAV
Vp
MPILs
(m2 g−1
)
(nm)
(cm3 g−1
)
P (BVS‐SO3Na)
417.50
17.89
9.61
0.81
0.05
0.73
P (BVS‐SO3H)
25.04
11.79
P (BVS‐SO3H)‐SO3CF3
286.90
sponge‐like structure which may due to the introduction
of H2SO4 through the acidification step, the structure of
which choke the mesoporous texture. But the framework
of cross‐linked dual Brønsted acidic MPILs kept tight dur-
ing the whole anion exchange process and the loose
porous structure of it is consistent with the BET analysis
result.
It can be obviously observed in Figure 3(d), (e) and (f)
that P (BVS‐SO3Na) exhibits an abundant hierarchical
net‐like mesoporous construction and the TEM of P
(BVS‐SO3H)‐SO3CF3 shows a different conformation,
which can be owing to the re‐crosslinking and partly
breakage during the introduction of CF3SO3H. While
the TEM of P (BVS‐SO3H) shows a relatively tight struc-
ture, which is correspond to the SEM result that the pores
within the framework is blocked.
Since two different kinds of strong Brønsted acids were
utilized to decorate the catalyst through the impregnation
step with P (BVS‐SO3Na) powders, it was of great neces-
sity to verify the thermal and structural stability of the
product after acidic treating. TG curves of the three sam-
ples were presented in Figure 4. All the synthesized prod-
ucts comprise three main weight loss steps at 50–120 °C,
260–395 °C and 410–600 °C[27,29–31]. When the tempera-
ture is lower than 120 °C, the first stage of the curve, it
could be observed that P (BVS‐SO3Na) and P (BVS‐
SO3H)‐SO3CF3 show a consistent thermogravimetric loss
at about 8.7% which may due to the combined water
within the samples. While the weight loss of P (BVS‐
SO3H) is nearly double of that of the other two samples
FIGURE 2 A: N2 adsorption–desorption isotherm and B:Pore size distribution of a) P (BVS‐SO3Na), b) P (BVSSO3H)‐SO3CF3, c) P (BVS‐
SO3H)

SHA ET AL.
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FIGURE 3 SEM image of a) P (BVS‐SO3Na), b)P (BVS‐SO3H) and c) P (BVS‐SO3H)‐SO3CF3; TEM image of d) P (BVS‐SO3Na), e)P (BVS‐
SO3H) and f) P (BVS‐SO3H)‐SO3CF3
as much as that of other two samples. Considering the
SEM and TEM analysis, the H2SO4 may leave in the
remains. Obviously, the P (BVS‐SO3H)‐SO3CF3 is slightly
less stable than P (BVS‐SO3Na) and the remains of P
(BVS‐SO3Na) is sort of more than that of P (BVS‐SO3H)‐
SO3CF3 which may all attribute to the small partly
destruction of precursor by introducing acidic ‐SO3CF3
groups during anion exchange.
3.2 | Catalytic performance evaluation
3.2.1 | Catalysis performance of P (BVS‐
SO3H)
FIGURE 4 TG curves of a) P (BVS‐SO3Na), b) P (BVS‐SO3H)
and c) P (BVS‐SO3H)‐SO3CF3
Effect of the catalyst amount
In this section, the catalysts with different ratio of sodium
p‐styrenesulfonate are investigated through the
which reflected that the hydrophilic property of P (BVS‐
SO3H) is much better ascribed to the acidification step
of sulfuric acid. The disintegration of acidic groups is cor-
responding to the second stage, P (BVS‐SO3Na) shows a
minor advantage of thermal stability than P (BVS‐SO3H)
and P (BVS‐SO3H)‐SO3CF3[29,32,33]. Apparently, the cata-
lyst is stable enough before 300 °C. The last stage is attrib-
uted to the collapse of the frameworks, P (BVS‐SO3H) and
P (BVS‐SO3H)‐SO3CF3 only have about less than 5% of
residue left, while the residue of P (BVS‐SO3H) is twice
target alkylation of o‐xylene with styrene (showed in
Figure 5). The specific reaction process is listed in the
experimental section. It can be observed that when the
x = 2 the catalyst perform a much better yield (showed in
Table 2). Too little or too much sodium p‐
styrenesulfonate both effect the property of the sample
and the reason of this phenomenon may attribute to the
polymerization of different functional groups during the
process which may block the active site of the catalyst.
Then we choose the sample with the system of sodium

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SHA ET AL.
FIGURE 5 The catalysis performance
of catalyst different x ratio of sodium p‐
styrenesulfonate in P (BVS‐SO3H): a)
x = 1.5, b) x = 2, c) x = 2.5
TABLE 2 Yield of PXE and conversion of styrene with different x
ratio of sodium p‐styrenesulfonate in P (BVS‐SO3H)
TABLE 3 Yield of PXE and conversion of styrene under different
temperature
Styrene conversion
rate (%)
PXE
yield (%)
Styrene
Catalyst
Temperature conversion PXE
Catalyst
(°C)
rate (%)
yield (%)
P (BVS‐SO3H) (x = 1.5)
P (BVS‐SO3H) (x = 2.0)
P (BVS‐SO3H) (x = 2.5)
69.4
90.1
68.7
64.4
80.0
59.3
P (BVS‐SO3H)‐SO3CF3 40 °C
P (BVS‐SO3H)‐SO3CF3 60 °C
P (BVS‐SO3H)‐SO3CF3 80 °C
P (BVS‐SO3H)‐SO3CF3 100 °C
P (BVS‐SO3H)‐SO3CF3 120 °C
40.2
51.0
71.0
83.1
100.0
32.2
44.8
61.1
73.3
93.7
The reaction temperature is 120 °C and the addition is 0.5 wt%
p‐styrene
sulfonate/1‐vinyl‐3‐butyl
imidazole
The addition is all the 0.5 wt%.
bromide/DVB/THF/H2O at a molar ratio of 2.0/1.0/2.0/
32.2/14.46 to carry out the following performance testing.
Effect of P (BVS‐SO3H)‐SO3CF3 amount
The adequate reaction temperature has been confirmed
to be 120 °C in the above section, in order to carry out
further and more in‐depth research, the aspect of addi-
tion amount of catalyst P (BVS‐SO3H)‐SO3CF3 has been
discussed to study its impact on the yield(%) of PXE
(showed in Table 4). It is no doubt that with the augment
of catalyst, it made a great influence on the PXE yield
(%) for it can introduce more active sites which can be
beneficial to provide more exposure of acidic sites. It is
easy to explain that the more active site we introduce,
the stronger the catalyst will show in the reaction under
the same reaction condition. Comparing with diverse
addition amount of cross‐linked mesoporous dual
Brønsted acidic poly (ionic liquids) P (BVS‐SO3H)‐
SO3CF3, it can be easily observed that the yield of PXE
almost achieve 100% with the catalyst is 0.5 wt%. When
the addition of catalyst is under a relatively lower condi-
tion the catalysis performance is not good enough, while
the increasing amount of catalyst never continually
increase the yield of PXE.
3.2.2 | Catalysis performance of P (BVS‐
SO3H)‐SO3CF3
Effect of the reaction temperature
Temperature of reaction was confirmed as another key
factor of the catalysis performance. In order to optimize
the reaction condition through a specific method, the cat-
alysts addition was identical controlled under an amount
of 0.5 wt%, and this section only changed the reaction
temperature (40 °C, 60 °C, 80 °C, 100 °C, 120 °C, respec-
tively) (showed in Table 3). Conversion rate (%) of styrene
was another evidence to prove the catalyst performance.
With the increasing of reaction temperature, the styrene
conversion rate (%) gradually increased synchronously.
The conversion rate (%) of styrene all reached 100% at
the temperature of 120 °C. A relatively higher tempera-
ture condition will be better for the alkylation reaction
of o‐xylene and styrene, and under this temperature, sty-
rene can achieve 100% which means that there is no sty-
rene leave in the reaction system.

SHA ET AL.
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TABLE 4 Yield of PXE and conversion of styrene under different
amount of P (BVS‐SO3H)‐SO3CF3
times recycling. The possible reason is that the sulfonic
acid groups within the structure of catalyst were
destroyed after reaction of alkylation of o‐xylene and sty-
rene for high reaction temperature and some of acidic
group ‐SO3CF3 may remain in the solvent of reaction sys-
tem. All these may be the ground for the low recycling
utilization. The SEM comparison of the two catalysts
has been listed in supporting information.
The results of BET, SEM, TEM and TG analysis are
corresponding to the result of catalysis performance of
the P (BVS‐SO3H) and P (BVS‐SO3H)‐SO3CF3. The block-
age of the pores within the sample may result from the
introduction of H2SO4 procedure in which the mesopores
are stifled which can also explain the SEM and TEM
result that the structure of P (BVS‐SO3H) is not the
sponge‐like one as the same of P (BVS‐SO3H) and P
(BVS‐SO3H)‐SO3CF3. All the above possible reasons lead
to the catalysis property of P (BVS‐SO3H) is much weaker.
Styrene
Addition
(wt%)
conversion
rate (%)
PXE
yield (%)
Catalyst
P (BVS‐SO3H)‐SO3CF3
P (BVS‐SO3H)‐SO3CF3
P (BVS‐SO3H)‐SO3CF3
P (BVS‐SO3H)‐SO3CF3
0.075
0.250
0.500
0.600
100.0
100.0
100.0
100.0
39.5
77.8
93.7
89.3
The reaction temperature is all the 120 °C.
3.2.3 | Recyclability of P (BVS‐SO3H)‐
SO3CF3 and P (BVS‐SO3H) catalyst
Depending on the above research, the recyclability of P
(BVS‐SO3H)‐SO3CF3 and P (BVS‐SO3H) catalyst was
investigated under the conditions of 120 °C and the
amount of catalyst is 0.5 wt% (relative to the weight of
the whole reaction system) is the optimal conditions.
Though the catalyst showed great catalysis performance
in the target alkylation, the recycling possibility of cata-
lyst would be an effective way to estimate the perfor-
mance of catalysts. In this section, we consider the
styrene conversion rate (%) and PXE yield(%) to estimate
the catalysis performance of the product and the reaction
cycle is also used to evaluate the stability of it. It is
remarkable that the recyclability of the catalyst we syn-
theses was not as stable as we anticipated. After the first
catalyst reaction, the P (BVS‐SO3H)‐SO3CF3 sample
exhibits a gradually degradation of catalysis performance
while the P (BVS‐SO3H) product display a sharp drop in
Figure 6. It can also be observed through the Figure 6 that
the property of P (BVS‐SO3H)‐SO3CF3 is much better
than that of P (BVS‐SO3H) through the reaction cycle test,
the yield of PXE from 93.7% to 53.3% after 5 times repeat-
ing comparing to the yield from 81.0% to 40.6% after 5
3.3 | Plausible mechanism of the catalyst
Figure 7 displays the possible construction mechanism of
[34–
P (BVS‐SO3H)‐SO3CF3. It is well known that HSO3CF3
38] as a kind of protonic super organic acid, whose acidity
is much higher in organic solvent than common acid
such as H2SO4. And the triflate is stable enough that the
redox reaction cannot happen. In addition, entirely stabil-
ity of network structure was greatly enhanced by the
energy between covalent bond and the interaction
between cations and anions. The copolymerization proce-
dure consists of three main synthesis steps. Firstly, DVB,
1‐vinyl‐3‐butyl imidazole bromide and sodium p‐styrene
sulfonate was crosslinked under a mild condition and
the solvent extraction is a critical process to produce
mesoporous structure. In the next step, H2SO4 was used
as material of acidification through ion exchange progress
FIGURE 6 The recycling of catalyst a)
P (BVS‐SO3H)‐SO3CF3 and b) P (BVS‐
SO3H)

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SHA ET AL.
FIGURE 7 Assumptive formation mechanism of ternary dual acidic MILs
to produce P (BVS‐SO3H). The final product P (BVS‐
SO3H)‐SO3CF3 was prepared by anion exchange. And
the original network was still keeping stable after
functionalization. The morphology difference of P (BVS‐
SO3H)‐SO3CF3 and P (BVS‐SO3Na) may be attributed to
the re‐crosslinking of polymer during the anion exchange
of ‐SO3CF3 which also lead to the reduce of some
mesopores inside the product. While the acidic of the
sample exhibit a great increase after the introduction of
‐SO3CF3 through the catalyst reaction.
of application potential, the sample showed promising
catalytic performance in alkylation of o‐xylene and sty-
rene. Through this study, it may be possible to develop
some novel green Brønsted‐based catalyst and time‐
saving routes for reactions such as Friedel‐Crafts reac-
tion, transesterification, esterification, cellulose hydroly-
sis reaction and so on. This may finally greatly expand
the application of solid acidic catalytic materials.
ACKNOWLEDGEMENTS
The authors are grateful to the financial supports of the
National Natural Science Foundation of China (Grant
No. 21676056, 21376051, 51673040, and 21306023), “Six
Talents Pinnacle Program” of Jiangsu Province of China
(JNHB‐006), Qing Lan Project of Jiangsu Province
(1107040167), Fund Project for Transformation of Scien-
tific and Technological Achievements of Jiangsu Province
of China (Grant No. BA2014100).
4 | CONCLUSION
In conclusion, a fresh cross‐linked mesoporous dual
Brønsted acidic poly (ionic liquids) with three monomers
was successfully synthesized. Accordingly, dual Brønsted
acid‐functionalized P (BVS‐SO3H)‐SO3CF3 was obtained
by sulfonating in the polymer framework. And the results
proved that the P (BVS‐SO3H)‐SO3CF3 under the condi-
tion of the molar ratio is B:V: S = 1:2:2, the reaction tem-
perature is 120 °C and the addition of catalyst is 0.5 wt%
of the reaction system, P (BVS‐SO3H)‐SO3CF3 catalyst the
can achieve the best conversion ratio(100%) and PXE
Yield(93.7%) Also, the catalyst contains abundant
mesopores and presents great thermal stability and sur-
face area. Comparing to other single acidic solid catalysts,
the introduction of ‐SO3H and ‐SO3CF3 groups would
markedly increase the exposed active acidic sites and
finally improved the catalytic performance. As a hetero-
geneous catalyst, P (BVS‐SO3H)‐SO3CF3 can be easily
detached from the reaction solvent and reduce the cost
of the catalyst especially. Furthermore, from a viewpoint
CONFLICT OF INTEREST
There are no conflicts to declare.
ORCID
Xiao Sha https://orcid.org/0000-0002-7377-2293
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