Controllable preparation of phosphonium-based polymeric ionic liquids as highly selective nanocatalysts for the chemical conversion of CO2 with epoxides

Article abstract of DOI:10.1039/c7gc00444c

A novel approach to overcoming the insulating properties of olivine 5 V electrode materials is realized in carbon-free LiCoPO₄ thin films by tailoring its chemical composition via the incorporation of lithium cobalt triphosphate into the olivine phase, thereby forming a network of conductive channels. The cyclic voltammograms of the engineered material exhibited a redox potential of ≈4.8 V/4.9 V. The experimentally obtained energy diagram quantified the inductive effect which led to the increase of the redox energy by ≈1.0 eV in comparison to LiCoO₂ layered oxide. Although the enhanced electronic conductivity and excellent electrochemical activity were obtained by using the thin film cathode material, the strategy of the design of olivine with triphosphate can be extended to more thick electrodes (>1 μm), giving a perspective for the development of 5 V all solid state batteries suitable for commercial application. The evident ability to exchange the charge of all Co²⁺ ions with lithiation/delithiation reaction and deliver high power in carbon free high voltage cathode material opens up new perspectives for the development of next generation of high energy density electrochemical storage devices.

Full text of DOI:10.1039/c7gc00444c

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PAPER
Controllable preparation of phosphonium-based polymeric ionic
liquids as highly selective nanocatalysts for the chemical
conversion of CO2 with epoxides
Received 00th January 20xx,
Accepted 00th January 20xx
Ying Liu, Weiguo Cheng, Yanqiang Zhang, Jian Sun and Suojiang Zhang*
DOI: 10.1039/x0xx00000x
Phosphonium-based polymeric ionic liquids have controllably prepared by using microfluidic
technique within an improved membrane microdevice. By the method, their average diameter sizes
could be tuned from 6.4 to 375 nm through varying the dispersed phase flow rates from 1.0 to 7.0
mL/min. The nanoparticles were characterized by FTIR, SEM, HRTEM, EDS, TGA and ICP, and their
catalytic properties were estimated in cycloaddition of CO2 with epoxides. It was found they could
perform from good to excellent yields with more than 99% selectivities, especially 1-bromoacrylic
acid decorated nanoparticles (NPILs-BPA). Additionally, the activity behaved obvious smaller size-
dependence and seven times’ recycling stabilities without loss of catalytic activity and selectivity.
Meanwhile, NPILs-BPA provided carboxylic acid groups and hydrogen bonding donor to active the
ring-opening of epoxides was also tested by in-situ FTIR. This work provided a continuous, simple
method for polymeric ionic liquids (PILs) with controlling-nanosizes, and potentially behaved the
advantage of being scaled-up and throughput in industrial application.
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Introduction
It is generally known that homogeneous catalysts including
metal salen complexes,13 based imidazole or phosphor ionic
Carbon dioxide (CO2) is the most abundant renewable carbon
resource in the world. Many efforts have been made to
transform CO2 into useful chemical products such as cyclic
carbonate,1 polycarbonates,2 carboxylic acid derivatives,3
formate4 and formamide intermediates5, especially cyclic
carbonates which have already applied into these fields
including the lithium secondary batteries6 and the green
organic synthesis of polycarbonates,7,8 pharmaceutical
medicine9 or some fine chemical products.10,11. To date, the
chemical fixation of CO2 onto epoxides via cycloaddition was
considered as the most useful, economical and green route for
the synthesis of cyclic carbonate (Scheme 1).12
liquids (ILs),14-16 and organic halide salts,17,18 performed higher
catalytic activities than their corresponding immobilized
catalysts such as carbon material,19 silicon gels,20,21 MCM-41
and SBA-1522 used as supports, etc.. However, they often
showed some disadvantages in catalysts’ separation and
products’ purification. Recently, imidazolium-based or
phosphonium based PILs not only behaved good separation
properties, but also exhibited good to excellent catalytic
activity in chemical transformation of CO2 with epoxides. It
was noteworthy that the phosphonium-based PILs more easily
gave almost single selectivity than the former. Therefore,
investigations on the design and preparation of PILs with
phosphonium cations’ function moieties have been attracted
much more attentions during recent ten years.23,24
Scheme 1. Cycloaddition between CO and epoxides
2
As the result of direct accessing PILs’ task-special catalytic
properties difficultly by conversional one-step’s radical
polymerization of vinyl-ILs monomers,25 many phosphonium-
based PILs have been successfully synthesized by the simple
post-polymerization modification26,27 such as phoshponium
chlorides immobilized onto fluorous polymer,24b polymer-
supported quaternary phosphonium salts,24c,d polymer grafted
with asymmetric phosphonium ILs24e and phosphonium halides
immobilized on polystyrene,24f,g etc.. , which usually needed
* State Key Laboratory of Multiphase Complex System, Beijing Key Laboratory of severe reaction conditions (scCO2 or high pressure more than
8.0 MPa) for the smooth conversion of CO2 with epoxides.24b
Ionic Liquids Clean Process, Institute of Process Engineering, Chinese Academy of
Sciences, Beijing, China, 100190. E-mail: sjzhang@ipe.ac.cn.
†Electronic Supplementary Information (ESI) available. See
DOI: 10.1039/x0xx00000x
The synergy function of hydrogen bonds with halide anions as
an efficient route has been introduced to improve the catalytic
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activity through facilitating the opening-rates of cyclic polymer chains by using the method of membrane
epoxides’ rings during the reaction process. For example, microdevice combined with post-polymerization of vinyl-
Zhang etal. found hydroxyl-functionalized ILs produced monomers containing with St, DVB and SDPP. The novel
Brønsted acid groups and the hydrogen bonding donor to membrane device (Fig. 2) was assembled by two parts of
accelerate the ring-opening rate of epoxides without any premix microdevice like those previous reported membrane
additional co-catalyst and organic solvent;1,14a Han et al. emulfication setups30, 31 and an additional double membranes’
reported betaine-based salts containing carboxylic acid group microdevice (Fig. S2-3， ESI). Three pieces of the stainless
provided synergetic effect with halide anion to active the ring- steel microfiltration membranes with 1.0 μm pore sizes were
opening of epoxides, and gave high yields of cyclic separately equipped into three parts of experimental setup.
carbonates.28
According to the detail operating procedure in the
Experimental section, the mixture solution of vinyl monomers
used as the dispersed phase flow was rapidly pumped into the
oil phase flow channel and penetrated the pores of premix
microdevice into the water phase flow containing with PVA
and SDS to form oil-in-water (O/W) microdroplets by cross-
flow shearing. Subsequently, microdroplets flow was repeatly
sheared by the pores of double membranes’ microdevice, and
then produced nanodroplets flow. As previous reported
mechanistic process of making droplets within membrane
contactors,32,33 anodic porous alumina membrane,31 and
microfluidic chips,34 each droplet emerged from the surface
pore of membrane often has a neck to connect the pore, the
Laplace pressure will pinch it off at the neck and bigger
droplets will be broken or rebroken into smaller and smaller
droplets.35 After post-polymerization, droplets were solidified
into nanoparticles by using AIBN as initiator, and NPILs
nanocatalysts were successfully synthesized by the covalent
bonds between carbon atom of methylene groups on
bromocarboxylic acid and phosphor atoms of nanoparticles.
Their morphologies were characterized by HRTEM as shown in
Fig. 3. It was found that NPILs had highly uniform-sizes and
spherical morphologies, and their coefficient of variance (CV)
was less than 12%.
Considering carboxylic acid groups could produce stronger
Brønsted acid and hydrogen bonding donor than hydroxyl
groups, and nanocatalysts easily play powerful catalytic
capability in chemical transformations due to their high
specific surface area and more active sites.29 In this work,
phosphonium-based PILs with nanosized particles (NPILs) and
carboxylic acid groups were employed to accelerate the
catalytic activity and products’ selectivity in cycloaddition of
CO2 with epoxides. To synthesize NPILs with uniform and
controllable nanosizes, a novel membrane microdevice was
designed and combined with the post-polymerization of St
,
DVB and SDPP (Fig.1) to tune nanoparticle sizes from 6.4 to
375 nm through simply varying the dispersed phase flow rates.
NPILs nanocatalysts were characterized by FTIR, SEM, HRTEM,
TGA, EDS and ICP. The catalysts performed good to excellent
yields with more than 99% selectivity, and their catalytic
activities behaved obvious smaller size-dependence.
Furthermore, the detailed mechanism for the catalytic
reaction was verified by in-situ FTIR spectroscopy, and the
synergy effect of carboxylic acid groups with bromide anion
units played a facilitated role for enhancing its catalytic activity.
Results and discussion
The force balance between cross-flow shearing and
interfacial forces plays a crucial role for the diameter sizes of
particles from making droplets as templates like polystyrene
nanoparticles31 and PLGA-PEG nanoparticles36. In current
investigation system, there were hardly changed in two
phases’ viscosities and interfacial tensions between two fluids
except pumps’ driving forces. Therefore, the particle sizes
were mainly influenced by two phases flow rates. To precisely
tune NPILs particle sizes, the detailed investigation of the
influence of two phase flow rates on them have been carried
out and the results were shown in Fig. 3d-f and Fig. 4. As the
increase of the dispersed phase flow rates from 1.0 to 7.0
mL/min, the average diameter sizes of NPILs were increased to
375 nm from 10 nm or so. When Qc and Qd were 20 mL/min
and 1.0 mL/min, respectively, the obtained average diameter
size was 6.4 nm with CV value of 12%. As Qd was increased to
3.0 mL/min, its average diameter size was also increased to 67
nm and its CV value was 9.5%. While Qd was increased to 5.0
mL/min, the average diameter size of NPILs was increased to
271 nm with CV value of 8.0%. Notably, when Qd was
continuously increased to 7.0 mL/min, the average diameter
sizes were increased to the biggest size of 375 nm within the
Synthesis of the phosphonium-based ionic liquids (NPILs)
nanocatalysts
Fig.1 General route for synthesizing carboxyl functionalized
phosphonium-based PILs nanocatalysts.
The general route for the synthesis of NPILs was depicted in
Fig.1. Phosphonium groups were directly incorporated into
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Fig. 2 The membrane microdevice with cross-flow shearing and the formation process of uniform-sized nanodroplets within it. Premix
microdevice: L×W×H=40 mm×30 mm×20 mm, both channels within: Ø2.0 mm; double membranes’ microdevice: L×W×H=40 mm×30 mm×21 mm,
channels within: Ø2.00 mm; the metal membrane: 1.0 μm pore size, Ø10 mm.
research scope. However, the CV value still remained a
performed a little bit of blue shift from 1308 to 1339 cm-1 (Fig.
constant like those particles prepared under smaller dispersed
5b). It was noteworthy that two new bands at 997 cm-1 and
phase flow rates.
1734 cm-1 which separately belonged to the intensive bending
FTIR spectroscopy was carried out to reveal the chemical vibrations of O-H bonds and the stretching vibration of C=O
structure of the obtained NPILs particle and the result was bonds. Moreover, as the result of the extended alkyl chains
shown in Fig.5. By the comparative analysis with un-modified after the phosphonium-based ILs modified by BPA compound,
NP (Fig. 5a), NPILs gave a strengthened stretching vibration of the bending vibrations of C-H bonds at the bands of 1406 cm-1
O-H bonds at the band of 3379 cm-1, and its bending vibration
and 1437 cm-1 can be also obviously enhanced.
c
a
b
e
f
d
Fig.3 HRTEM photos and the size distributions of the phosphonium-based polymeric nanoparticles synthesized by the reported microfluidic
technique under three different dispersed fluid flow rates (Qd): (a) and (d) 3.0 mL/min; (b) and (e) 5.0 mL/min; (c) and (f) 7.0 mL/min. Their
corresponding flow rates of continuous fluid remained the value of 20 mL/min.
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a
c
[1]
b
d
[2]
Fig. 4 Effects of dispersed phase flow rate Qd on the NPILs average
diameter sizes under continuous phase flow rate of 20 mL/min.
Fig. 6 SEM images of the magnified surfaces of phosphonium-based
polymer nanoparticle (a) and NPILs (b). The scale bar is 25 nm; (c)
EDS spectrum of the particle at the surface area 1 in Fig. 6a; (d) EDS
spectrum of NPILs particles at the surface area 2 in Fig. 6c.
a
1406 cm-1
Two compounds of 3-bromopropionic acid (BPA) and 4-
bromobutyric acid (BBA) were separately utilized to modify the
NP particles with the average diameters size of 67 nm to form
NPILs-BPA and NPILs-BBA. Their thermal stabilizations were
analysed by TGA as depicted in Fig. 7. The curve of NPILs-BPA
indicated that there was two stages’ weight loss as the
increase of heated temperature ranging from 0 to 750 °C. The
weight loss at the first stage occurred in the temperature
ranging from 200 to 380 °C due to the thermal decomposition
of immobilized BPA, which indicated that NPILs-BPA could
remain thermal stability under the temperature of 200 °C. By
contrast, NPILs-BBA has a gentler and smaller weight loss at
the same temperature range. In addition, another stage
occurred in the temperature ranging from 380 to 450 °C like
the curve of NP nanoparticles because of the thermal
decomposition of their cross-linked network structures.
b
1734 cm-1
3379 cm-1
997 cm-1
1339 cm-1
Fig. 5 FTIR spectra of NP (a) and NPILs (b).
The phosphonium-based NP and NPILs were separately
sticked onto the silicon pellet. After they were coated by
platinum under vacuum, SEM and SEM-EDS were independly
utilized to characterization particles’ outsurfaces and their
corresponding compositions as shown in Fig.6. Compared with
the outsurface of nanoparticles, that of NPILs gave a clear and
rough view due to the grafted ionization structures onto them
like previous reported polymer grafted with asymmetrical
dication ILs (Fig.6a and c).24c Their corresponding SEM-EDS
spectrum shown that the elements of phosphorous, oxygen
and bromine appeared onto NPILs, which indicated that the
nanoparticles could be successfully modified by using the BPA
compound through ionization process.
Fig. 7 TGA curves of polymeric ionic liquids nanocatalysts. NP:
67 nm; NPILs-BPA: 67 nm, modified by BPA; NPILs-BBA: 67 nm,
modified by BBA.
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Cycloaddition reaction
catalytic performances of those reported polymeric ionic liquids in
this reaction such as the phosphonium-based ionic
liquids (FPBILs),14c the fluorous polymers with phosphonium
chloride (FPPC),24b the functionalized guanikdinium-based ILs
(FGILs)37 and polymer-supported task specific ionic liquids,1,38
etc.. Moreover, the catalytic activity of NPILs-BPA was also
affected by reaction times. When the reaction time was 2 h,
the yield of cyclic carbonate was 95% with 99% selectivity
(entry 8, Table 1). As the reaction time was extended to 8 h
from 4 h, the product’s yield was increased to 99% and its
corresponding selectivity always remained the highest value of
more than 99% (entries 4, 9 and 10, Table 1). Under the
reaction conditions of 2MPa CO2 pressure, 150 °C and 4 h, the
catalytic activity of NPILs-BPA could be enhanced by the
increase of their utilization amounts from 0.25 to 0.75 mol%
(entries 4, 11 and 12, Table 1). Especially, when the catalyst’s
amount was increased to 0.75 mol%, NPILs-BPA performed
excellent catalytic activity with the yield of 99% and its
selectivity more than 99%.
The cycloaddition reaction of CO2 with propylene oxide was
chosen as a model reaction to evaluate the catalytic activities
of NPILs nanocatalysts. The influence of reaction parameters
on the catalytic performance was screened by using NPILs-BPA
with the average diameter size of 67 nm as a catalyst under
nonsolvent environment, and the results were summarized in
Table 1. As the temperature increased from 90 to 150 °C, the
product yield of 4-methyl-1,3-dioxolan-2-one was increased
from 35 to 98% within the reaction time of 4 h (entries 1-4,
Table 1). It was wonderful to found that their selectivity always
remained higher values (>99%) and there was no obviously
decreased under lower temperature. For example, the
reaction was carried out under the conditions of 90 °C, 2 MPa
CO2 for 4 h, the yield of obtained carbonate’s product was only
35% with the highest selectivity of 99% (entry 1, Table 1).
Moreover, the pressure of CO2 was an important parameter
for achieving higher product’s yield and the best selectivity.
When the reaction pressure was 1 MPa, the product’s yield
and its corresponding selectivity were 81% and >99%,
respectively (entry 5, Table 1). While the CO2 pressure
gradually increased to 2 MPa from 1 MPa, the catalytic activity
of NPIL-BPA performed a peak value with the highest yield of
98% and more than 99% selectivity. In our experiment, we
meant to continuously enhance the catalytic activity of NPILs-
BPA in cycloaddition by elevating the CO2 pressure;
unexpectedly the overpressure restrained the improvement of
product’s yield. The phenomenon was similar with the
Effects of various catalysts on the cycloaddition of propylene
with CO2 were carried out under these conditions of CO2
pressure 2 MPa, 150 °C, 0.50 mol% of the catalyst’s amount
and reaction for 4 h, and their corresponding results were
summarized in Table 2. When PPh3 as the catalyst was applied
into the reaction, both substrates of propylene and CO2 cannot
be conversed smoothly (entry 1, Table 2). By contrast, the
modified catalysts, for example [Ph3PC3H7]Br (entry 2, Table2),
[Ph3P(CH2)2COOH]Br
(entry
3,
Table
2)
and
[Ph3P(CH2)3COOH]Br (entry 4, Table 2), preferred to exhibit
from middle to excellent catalytic activities (74-98% yield). It
was noteworthy that NP obtained from the reported novel
technique in the work had been performed the higher catalytic
activity than PPh3 (entry 5, Table 2), which possibly resulted
from their physical properties of high specific surface areas
and porous structures. For the purpose of determination of
the carboxyl acid groups having good facilitation roles for the
cycloaddition of CO2 with propylene oxide, BPA and BBA were
separately mixed with NP particles at the molar ratio of 0.20,
and successively catalysed the conversion of propylene oxide
with CO2. It was found that the complex of NP/BPA shown the
higher catalytic activity with the product’s yield of 95% (entry 6,
Table 2) than the complex of NP/BBA, possibly because of the
former catalyst behaved stronger acidity than the latter which
could enhance the catalytic activity and lower the barrier
height value of the ring-closing step during its mechanism
process like other reported functionalized ionic liquids with —
COOH, ‒OH and —SO3H.39,40 Furthermore, both NPILs-BPA
and NPILs-BBA which were obtained by NP separately
modified with BPA and BBA through the covalent bond
between the carbon atom of the carboxylic acid group and the
phosphor atom of NP immobilization to form NPILs-BPA and
NPILs-BBA, exhibited the best catalytic activities than before
(entries 8 and 9, Table 2). It indicated that the catalytic
activities and high selectivity could be still maintained after the
phosphonium-based nanoparticles modified with the
bromocarboxylic acid compounds.
Table 1. Screening reaction parameters for the cycloaddition of CO2
with propylene oxide catalysed by NPILs-BPAa.
Entry Temperature Pressure Time Yieldb Selectivityc
(°C)
(MPa)
(h)
(%)
(%)
1
2
3
4
5
6
7
8
90
2
2
4
4
4
4
4
4
4
2
6
8
4
4
35
71
83
98
81
96
89
95
98
99
92
99
99
99
110
130
150
150
150
150
150
150
150
150
150
2
＞
99
99
99
99
99
2
＞
＞
＞
＞
1
1.5
3
2
99
2
＞
99
99
9
2
＞
10
11d
12e
2
99
2
＞99
aReaction conditions: propylene oxide (14.3 mmol, 0.83 g), NPILs-BPA
(0.50 mol%). b,CDetermined by GC using mesitylene as an internal
standard. dNPILs-BPA (0.25 mol%). eNPILs-BPA (0.75 mol%).
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Table 2 Cycloaddition of CO2 with propylene oxide catalysed by various
phosphonium-based catalystsa
Entry
catalyst
Yieldb (%)
Selectivityc (%)
1
2
PPh3
[Ph3PC3H7]Br
[Ph3P(CH2)2COOH]Br
[Ph3P(CH2)3COOH]Br
NP
trace
74
99
99
99
99
99
98
99
3
84
4
98
5
55
6d
7e
8
NP/BPA
95
NP/BBA
74
Fig. 8 Yield versus times for the cycloaddition reaction catalyzed by
NPILs nanocatalysts with different average diameter sizes. Reaction
conditions: propylene oxide (14.3 mmol), CO2 pressure 2 MPa, catalyst
(0.50 mol%), 150 °C.
NPILs-BPA
98
>
99
9f
NPILs-BBA
92
99
aReaction conditions: propylene oxide (14.3 mmol, 0.83 g), 67 nm of
catalyst (0.50 mol%), 150 °C, CO2 pressure 2 MPa, 4 h; b,cDetermined
by GC using mesitylene as an internal standard. d,eThe molar ratio of
NP to 1-bromocarboxylic acid was 0.20. fBBA anchored onto NP.
Table 3 Substrates tolerance of NPILs nanocatalyst in cycloaddition of
a
epoxides with CO2
Entry Epoxides
Products
Yieldb(%) Selectivityc(%)
The size dependence of the catalytic performance of NPILs
nanocatalysts in cycloaddition was also investigated and the results
were depicted in Fig.8. NPILs nanocatalysts with the different
average diameter sizes of 67 nm, 271 nm and 375 nm were
respectively applied into cycloaddition of propylene oxide with CO2
under the reaction conditions of the catalyst amount of 0.50 mol%,
the CO2 pressure 2 MPa and 150 °C. It was found that different
particle-sized nanocatalyts exhibited different reaction activities.
Nanocatalyst with the smallest particle size of 67 nm gave the
highest yield of 98% within 4 h among them, which could be
ascribed to high concentration active sites on the smaller particle-
sized nanocatalyst like those reported Mac-Pd41 and Rh
1
99
98
＞
99
99
2
3
＞
95
92
99
nanoparticles42
. While 375 nm of the biggest particle-sized
nanocatalyst shown the lowest catalytic activity with the yield of
92% and 99% selectivity under the same reaction conditions.
However, when the reaction time was prolonged to 6 h, the biggest
nanocatalyst achieved the yield of 97% with 99% selectivity.
Therefore, highly efficient catalytic activity was inclined to smaller
particle-sized nanocatalyst, and the catalytic activity of bigger
particle-sized catalyst could achieve the similar yield with that of
smaller particle size by extending reaction times probably due to
their different chemical and structural factors on the surface of
nanocatalysts and the synergy role of hydrogen bonds.
4
5
99
88
＞99
6
94
＞99
aReaction conditions: epoxide (14.3 mmol), CO2 pressure 2 MPa, NPILs-
BPA (0.50 mol%), 150 °C and 4 h. b,cDetermined by GC using mesitylene
as an internal standard and NMR spectroscopy.
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NPILs-BPA with the particle size of 67 nm was chosen to
investigate its substrates tolerance under optimized reaction
conditions, and their results were summarised in Table 3. The
reaction of ethylene oxide with CO2 gave a GC yield of 99% with the
selectivity of more than 99% within 4 h (entry 1, Table 3). When
one hydrogen atom of ethylene oxide was substituted by a methyl
group to active the molecular of CO2, the obtained cyclic carbonate
product was 98% yield and still remained high selectivity value
(entry 2, Table 3). The result could be ascribed to the potential
differences in epoxide ring strain and the conformation of bulkily
ring-opened species, which has already been tested by the
published work.43,44 Reaction enthalpies of ethylene epoxide and
propylene oxide differed by no more than 2 KJ mol-1,44 that was,
both substrates exhibited in most respect almost the same ring
strain. While the one hydrogen of ethylene oxide was substituted
by two methyl groups in the reaction of cyclic carbonate, NPILs-BPA
still performed high selectivity, but there was a little decrease in
cyclic carbonate’s yield of 95% because of the space steric
hindrance from its substituted structure (entry 3, Table 3). Other
substrates with bulky substituted groups were also applied into the
reaction, for example cyclohexene oxide and styrene oxide, which
also gave lower products’ yields of 92% and 88%, respectively
(entries 4 and 5, Table 3). Furthermore, the substrate of 2-
(phenoxymethyl)oxirane gave an excellent yield of 94% with more
than 99% selectivity (entry 6, Table 3) possibly due to the
substituted groups’ electron-withdrawing effect.
Fig. 9 Recycling test of NPILs nanocatalyst. Yield and selectivity of the
product of 4-methyl-1,3-dioxolan-2-one was determined by GC using
mesitylene as an internal standard.
Mechanism process
According to our previous reported work,1,14d a proposed
general mechanism process was despicted in Scheme 2 for the
cycloaddition between CO2 and cyclic epoxides, which
followed a three-step mechanism containing the ring-opening
of epoxides, the insertion of CO2 and the intermolecular
cyclization. Among the three-step mechanism, the ring-
opening process of cyclic epoxides was usually considered as
Recyclability of the catalysts
The catalytic stability of NPILs nanocatalyst was an the rate-determining step during the catalytic transformation
important factor for its large-scaled production. Thus, the
recyclability of NPILs-BPA nanocatalyst with the average
diameter size of 67 nm was carried out under the our
optimized reaction conditions of 150 °C, 2 MPa CO2 pressure,
0.50 mol% catalyst’s amount and 4 h, and the result was
depicted in Fig. 9. The catalyst could be separated and
recovered by a simple centrifugation after being successively
washed with ethyl acetate, ethanol and then dried under
vacuum atmosphere for the next run. As a result, the catalyst
could be recycled at least seven times without the leaching of
phosphonium salts (seeing Figure 8S, ESI), and the selectivity
of 4-methyl-1,3-dioxolan-2-one still remained the high value of
99%. It indicated that the catalyst was not insoluble in the
reaction mixture, but performed excellent catalytic activities
with high cyclic carbonate’s selectivity.
process. In addition, the hydrogen bond between the
carboxylic acid group on NPILs-BPA nanocatalyst and cyclic
epoxides probably played an important role for accelerating
the ring-opening process of cyclic epoxides. To deeply
understand the mechanism process, in-situ FTIR spectroscopy
was utilized to observe the absorption intensity of carbonyl
group under controlled experimental conditions, as shown in
Fig. 10. Fig. 10a depicted there was not changed in the
adsorption intensity at 1735 cm-1 belonged to the stretching
vibration of C=O bond within 4.5 h. The result indicated that
the catalyst was very stable at the temperature of 150 °C
within 4.5 h. The presence of propylene oxide resulted in a
slight shift to lower wavenumber of 1734 cm-1 due to the
1735 cm-1
1802 cm-1
1734 cm-1
1735 cm-1
a
b
c
Fig. 10 In-situ FTIR spectra collected every 20 s. Reaction conditions: (a) 0.25 mmol of NPILs-BPA, KBr 100 mg, 150 °C, 4.5 h; (b) 0.25 mmol
of NPILs-BPA, 14.3 mmol of propylene oxide, KBr 100 mg, 150 °C, 4.5 h; (c) 0.25 mmol of NPILs-BPA, 14.3 mmol of propylene oxide, KBr
100 mg, 0.2 MPa of CO2, 150 °C, 4.5 h.
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Journal Name
hydrogen bond between the carboxylic acid group onto NPILs- cyclohexyl and ether, and exhibited good to excellent yields
BPA and oxygen atom in cyclic epoxide, as shown in Fig.10b. with more than 99% selectivities. By simple centrifugation, it
When CO2 and propylene oxide were altogether introduced into the could be recovered and reused seven times without loss of
system and contacted the catalyst, the adsorption intensity of catalytic activity and selectivity. Furthermore, the mechanism
ν
(C=O) at 1802 cm-1 belonged to the product of propylene process was deeply investigated by In-situ FTIR, and its results
carbonate was gradually strengthened under the controlled verified that the ring-opening of cyclic epoxides benefitted
experiments (Fig. 10c). However, when CO2 was single from the synergic effect of bromide anions with hydrogen
introduced and then contacted NIPILs-BPA, no clearly shift in bond between carboxylic acid groups onto NPILs and oxygen
the adsorption peak at 1735 cm-1 was found in the curves of atoms of epoxides. Further investigation on the adapted
Fig. S7, ESI. These investigation results indicates that the alone scopes of the reported method especially the dispersed phase
catalyst or CO2 could not open the ring of cyclic epoxides flow containing with more hydrophilic monomers and the
probably due to the chemical stability of three-ring of epoxides catalytic versatilities were very important for deeply
under our set experiments, but the hydrogen bond between understand the formation process of nanodroplets and
carboxylic acid groups and oxygen atom on three-ring of catalytic transformation mechanism of CO2.
epoxides was initially constructed and formed a nucleophilic
intermediate like complex(I) in Scheme 2, which more easily
Acknowledgementst
open the epoxide ring by synergistic effects with the bromide
anion of the reported catalysts to further generate carbonates.
The authors gratefully acknowledge the financial supports
from the National Key Projects for Fundamental Research and
Development of China (2016YFB0600903) and the National
Natural Science Foundation of China (21576264, 21306098 and
21476245) in this work.
Experimental section
Materials
Sodium dodecyl sulphate (SDS) and poly (vinyl alcohol) (PVA,
molecular weight 1770) were purchased from Sinopharm.
Group Co. Ltd. In China and directly used without any
purification.
4-Diphenylphosphinostyrene
(SDPP)
was
synthesized by using the reaction between the Grignard
reagent of 4-bromostyrene (Analytical grade, Aladdin. Co., Ltd.,
Shanghai, China) and chlorodiphenylphosphine (Aladdin) in
dried tetrahydrofuran (THF) according to literature reported
method.45 Styrene (St, analytical grades) and divinylbenzene
(DVB, 55%) were obtained from Aladdin Co. Ltd., Shanghai,
China and purified by washing with 3M NaOH aqueous
solution
to
remove
off
inhibitors
within.
2,2-
Scheme 2. Proposed mechanism for cycloaddition.
azobisisobutyronitrile (AIBN, Aladdin) as an initiator for the
copolymerization was recrystallized before being used.
Ethylene oxide (EO), propylene oxide (PO, ≥99.5%),
cyclohexene oxide (98+%), 2,2-dimethyloxirane (98%), styrene
oxide (98+%) and 2-(phenoxymethyl)oxirane (97%) were
obtained from Alfa Aesar and all used as received directly.
Conclusions
In this work, we have developed a novel and continuous
microfluidic method to synthesize NPILs in a novelmembrane
microdevice by using cross-flow shearing. Nanodroplets
containing with phosphor monomers were generated at outlet
of the microdevice and subsequently solidified to spherical
nanoparticles by using a post-polymerization. Their particle
sizes could be controllably changed from 6.4 to 375 nm by
simply varying the dispersed phase flow rates from 1.0 to 7.0
mL/min. For cycloaddition of cyclic epoxides with CO2, NPILs
performed excellent catalytic activities with 99% selectivity,
and their high efficient catalytic performance tended to that of
smaller nanocatalyst. Additionally, it had tolerance to a series
of groups of cyclic epoxide, including methyl, dimethyl, phenyl,
Preparation of carboxyl functionalized phosphonium-
based polymeric ionic liquid (NPILs) nanoparticles
A modified membrane microdevice was equipped by one
premix microdevice and the double membranes’ microdevice
with 1.0 μm pore sizes of the stainless steel microfiltration
membranes. The continuous fluid (Qc) was an aqueous
solution containing 1.0 wt% PVA and 0.5 wt% SDS, and the
dispersed fluid (Qd) was the organic mixture solution
containing SDPP (5.0 mmol, 1.44 g), ST (9.60 mmol, 1.0 g), DVB
8 | J. Name., 2016, 00, 1-3
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Paper
(1.52 mmol, 0.20 g) and AIBN (1.0 wt% of total monomers).
1,2-butylene carbonate: 1H NMR (600 MHz, CDCl3): δ = 4.12
The both fluids were carried to the cross-flow membrane (s, 2H, CH2), 1.49 (s, 6H, 2CH3); 13C NMR (150 MHz,CDCl3): δ =
emulsifiers through steel tubes by two meter-pumps (Beijing 154.69 (C=O), 81.80 (CH2O), 75.47 (CO), 25.87 (2CH3).
Satellite Manufactory Factory, China). Subsequently, the mixed
Styrene carbonate: 1H NMR (600 MHz, CDCl3): δ = 7.45-7.35
fluidic solution was directly flowed into the two steps’ (m, 5H, Ph), 5.67 (t, J = 8.0 Hz, 1H, OCH), 4.79 (t, J = 8.4 Hz, 1H,
membrane emulsifiers to form oil/water microemulsion. The CH), 4.34 (t, J = 8.4 Hz, 1H, CH); 13C NMR (150 MHz, CDCl3): δ =
obtained microemulsion was heated over 75 °C to initiate the 154.95 (C=O), 135.87 (Ar-C), 129.84 (ArCH), 129.34 (ArCH),
copolymerization of monomers. After completing the 125.98 (ArCH), 78.10 (OCH), 71.28 (OCH2).
solidification process, the phosphonium-based nanoparticles
NP were collected by the centrifugal separator and δ= 7.30 (t, J = 8.0 Hz, 2H, m-Ph), 7.00 (t, J = 7.4 Hz, 1H, p-Ph),
successively washed with deionized water (3 50 mL) and 6.90 (d, J = 8.2 Hz, 2H, o-Ph), 5.04-5.00 (m, 1H, OCH), 4.61 (t,
3-Phenyoxypropylene carbonate: 1H NMR (600 MHz, CDCl3):
(
)
×
ethanol (3
×
50 mL). Then, it was dried at 45 °C under vacuum J=8.5 Hz, 1H, CH), 4.53 (t, J = 5.8 Hz, 1H, CH), 4.23 (dd, J = 10.5,
4.3 Hz, 1H, =CHO), 4.15 (dd, J = 10.5, 3.2, 1H, =CHO); 13C NMR
atmosphere.
Carboxylic functionalized phosphonium-based polymeric (150 MHz ,CDCl3): δ=157.83 (ArC), 154.67 (C=O), 129.79 (m-
ionic liquids (PILs) were synthesized in a three-neck flask pre- ArCH), 122.11 (p-ArCH),114.70 (o-ArCH), 74.13 (CH2), 66.97
equipped with a reflux condensing tube under nitrogen gas (CH), 66.34 (CH2O).
atmosphere. The obtained NP particles (1.0 g), 3-
1,2-cyclohexene carbonate: 1H NMR (CDCl3, 600 MHz) δ =
bromopropionic acid (3.0 g) and dried acetonitrile (50 mL) 4.70-4.67 (m, 2H, 2×CH), 1.92-1.89 (m, 4H, 2×CH2), 1.66-1.60
were successively added into the three-neck flask. Then, the (m, 2H, CH2), 1.46-1.40 (m, 2H, CH2); 13CNMR (150 MHz, CDCl3):
mixture was stirred by a magnetic agitator and refluxed for 24 δ = 155.51 (C=O), 75.74 (CH), 26.8 (CH2), 19.19 (CH2).
h. After completing the reaction, it was warmed to the room
temperature, and nanocatalyst NPILs were filtrated out by the Characterization
millipore filtration membrane and washed with diethyl ether
(3×10 mL). Finally, the catalyst was dried at 45 °C under Thermogravimetric analysis (TGA) was carried out on
vacuum and stored under nitrogen atmosphere.
Shimadzu Corp. DTG-60H Thermal Analysis System at a heating
rate of 10 °C/min from 25 to 750 °C under N2 atmosphere. The
infrared spectra of samples were performed with Thermo Corp.
Nicolet 380 FT-IR spectrometer by using KBr as a standard
General procedure for cycloaddition reaction
The cycloaddition reaction of CO2 with epoxides was carried material. The morphologies of the samples were characterized
out in a stainless steel autoclave with 25 cm3 inner volume, by using high resolution transmission electron microscope
and its’ general procedure was described as below: 0.50 mol% (HRTEM) on
a JEOL JEM-2100F (UHR) field emission
of nanocatalyst and epoxide (14.3 mmol) were added into the microscope and scanning electron microscope (SEM) SU8020,
autoclave with a magnetic stirrer at 500 rpm. A constant and their compositions of samples were measured on the
pressure of CO2 was charged into the autoclave at room Oxford electric refrigeration X-ray energy dispersive
temperature, and then heated to a preset temperature for an spectrometer (EDS). The contents of phosphor on the whole
appropriate reaction time. After completing the reaction, the nanocatalysts were determined by the inductively coupled
autoclave was warmed to the room temperature, plasma atomic emission spectroscopy (ICP, Optima 2000DV)
depressurized and the mixture solution was diluted by toluene. successively through being calcined in a muffle furnace at
Biphenyl (40 mg) as the internal standard was added into the 700 °C for 2 h and being charged to a constant volume by using
diluted solution, and the products’ yields were determined by aqua regia. The reaction mechanism was explored by using
GC (Agilent 7890A) and GC-MS (Agilent 6890N/5975B). After Thermo Corp. Nicolet 6700 in-situ FTIR spectrometer at the
removing off the solvent, the purified products were obtained operation temperature of 150 °C.
from the silica gel column chromatography by using ethyl
acetate/petroleum (1:10) as the eluent.
The products’ structures were confirmed by NMR. 1H NMR
and 13C NMR were measured by a JNM-ECA 600 spectrometer,
Notes and references
1
2
3
B.H. Xu, J.Q. Wang, J. Sun, Y. Huang, J.P. Zhang and S.J. Zhang,
Green Chem., 2015, 17(1), 108ꢀ122.
Y. Liu, W.M. Wang, W.P. Zhang, R.R. Zhao and X.B. Lu, Nature
Commun., 2015, 6, 1ꢀ8.
S. Manzini, N. Huguet, O. Trapp and T. Schaub, Eur. J. Org. Chem.,
2015, 1(32), 7122ꢀ7130.
and tetramethylsilane (TMS) was used as an internal standard
to correct chemical shifts. Spectral characteristics of these
products were given as follows:
1
Ethylene carbonate: H NMR (600 MHz, CDCl3): δ = 4.51 (S,
4H, OCH2); 13C NMR (150 MHz, CDCl3): δ =155.48 (C=O), 64.65
(OCH2).
4
5
A. Aouissi and S.S. AlꢀDeyab, J. Nat. Gas. Chem., 2012, 21, 189ꢀ193.
X.L. Du, G. Tang, H.L. Bao, Z. Jiang, X.H. Zhong, D.S. Su and J.Q.
Wang, Chemsuschem., 2015, 8(20), 3489ꢀ3496.
Propylene carbonate: 1HNMR (600 MHz, CDCl3): δ = 4.85-
4.81 (m, 1H, OCH), 4.53(t, J = 8.0 Hz, 1H, CH2), 4.01 (t, J = 8.0
Hz, 1H, CH2), 1.46 (d, J = 6.2 Hz, 3H, CH3); 13C NMR (150 MHz,
CDCl3): δ =155.13 (C=O), 73.64 (OCH), 70.74 (OCH2), 19.50
(CH3).
6
H. Yura, P. HeaiꢀKu, P. HoꢀSeon and L. ChangꢀSeop, J. Nanosci. Nano.
Techno., 2015, 15(11), 8951ꢀ8960.
7
G. Kapiti, H. Keul and M. Möller, Mater. Today Commun., 2015, 5, 1ꢀ
9.
This journal is © The Royal Society of Chemistry 20xx
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DOI: 10.1039/C7GC00444C
Paper
Journal Name
8
9
P. Olsén, K. Odelius, H. Keul and A.C. Albertsson, Macromolecules, 30 Z.D. Liu, Y.C. Lu, M. Zhang, W.M. Wang and G.S. Luo, J. Appl.
2015, 48(6), 1703ꢀ1710.
Polym. Sci., 2013, 1202ꢀ1211.
J.H. Clements, Ind. Eng. Chem. Res., 2003, 42, 663ꢀ674.
31 T. Yanagishita, R. Fujumura, K. Nishio and H. Masuda, Langmuir, 2010,
26(3), 1516ꢀ1519.
10 D.C. Webster, Prog. Org. Coat., 2003, 47, 77ꢀ86.
11 G. Rokicki, Prog. Polym. Sci., 2000, 25, 259ꢀ342.
12 J.M. Sun, S. Fujita and M. Arai, J. Organometal. Chem., 2005, 690,
3490 ꢀ3497.
32 H. Sawalha, Y. Fan, K Schroen and R. Boom, J. Membr. Sci., 2008,
325, 665ꢀ671.
33 N.A. Wagdare, A.T.M. Marcelis, O.B. Ho, R. Boom and C.J.M. van
RijN, J. Membr. Sci., 2010, 347, 1ꢀ7.
13
Salenꢀmetal complexes catalyze cycloaddition under mild conditions:
(a) X.B. Lu, Y.J. Zhang, B. Liang, X. Li and H. Wang, J. Mol. Catal. A: 34 Q.Q. Zhou, Y. Sun, S. Yi, K. Wang and G.S. Luo, Soft Matter, 2016,
Chem., 2004, 210, 31ꢀ34; (b) A. Decortes, A.M. Castilla and A.W. 12, 1674ꢀ1682.
Kleij, Angew. Chem. Int. Ed., 2010, 49, 9822ꢀ9837; (c) R.C. Luo, X.T. 35 J. Pellegrino, L.R. Schulte, De la J. Cruz and C. Stoldt, J. Membr. Sci.,
Zhou, S.Y. Chen, Y. Li, L. Zhou and H.B. Ji, Green Chem., 2014, 16,
1496ꢀ1506.
14 Homogeneous ionic liquids for the cycloaddition of CO2 and epoxides:
2017, 522, 245ꢀ256.
36 M. Rhee, P.M. Valencia, M.I. Rodriguez, R. Langer, O.C. Farokhzad
and R. Kamik, Adv. Mater., 2011, 23, H79ꢀH83.
(a) J. Sun, S.J. Zhang, W.G. Cheng and J.Y. Ren, Tetrahedron Lett., 37 W.L. Dai, B.Jin, S.L. Luo, X.B. Luo, X.M. Tu and C.T. Au, J. Mol.
2008, 49, 3588ꢀ3591; (b) J.S. Tian, J.Q. Wang, J.Y. Chen, J.G. Fan, F. Catal. A: Chem., 2006, 250, 30ꢀ34.
Cai and L.N. He, Appl. Catal. A: General, 2006, 301, 215ꢀ221; (c) W.L. 38 S.J. Zhang, J. Sun, X.C. Zhang, J.Y. Xin, Q.Q. Miao and J.J. Wang,
Dai, B. Jin, S.L. Luo, X.B. Luo, X.M. Tu and C.T. Au, Appl. Catal. A, Chem. Soc. Rev., 2014, 43, 7838ꢀ7869.
2014, 470, 183ꢀ188; (d) W.G. Cheng, B.N. Xiao, J. Sun, K. Dong, P. 39 L. Wang, P. Li, Y. Li, H.Q. He and J.L. Zhang, Thero. Chem. Acc.,
Zhang, S.J. Zhang and N.F.F. Flora, Tetrahedron Lett., 2015, 56(11),
2015,134, 75ꢀ85.
1416ꢀ1419.
40 L.F. Xiao, D.W. Lv, D. Su, W. Wu and H.F. Li, J. Clean Prod., 2014,
67, 285ꢀ290.
41 Y. Liu, Y.C. Lv and G.S. Luo, Chin. J. Catal., 2013, 34, 1635ꢀ1643.
15 M.M. Dharman, H.J. Choi, D.W. Kim and D.W. Park, Catal. Today,
2011, 164, 544ꢀ547.
16 L. Han, H. Li, S. Choi, M.S. Park, S.M. Lee, Y.J. Kim and D.W. Park, 42 Y. Zhang, D.A.J. Michel Ligthart, X.Y. Quek, L. Gao and E.J.M.
Appl. Catal. A: General, 2012, 429ꢀ430, 67ꢀ72. Hensen, Int. J. Hydrogen Energ., 2014, 39, 11537ꢀ11546.
17 Z. Zhou, C. He, J.H. Xiu, L. Yang and C.Y. Duan, J. Am. Chem. Soc., 43 M.W. Lehenmeimer, C. Bruckmeier, S. Klaus, J.E. Dengler, P.
2015, 137(48), 15066ꢀ15069. Deglmann, A.K. Ott and B. Rieger, Chem. Eur. J., 2011, 17, 8858ꢀ8869.
18 R. Babu, A.C. Kathalikattil, R. Roshith, J. Tharun, D.W. Kim and D.W. 44 L. Wang, P. Li, H.Q. He and J.L. Zhang, Theor. Chem. Acc., 2015, 134,
Park, Green Chem., 2016, 18, 232ꢀ242. 75ꢀ85.
19 J. Xu, F. Wu, Q. Jiang, J.K. Shang and Y.X. Li, J. Mol. Catal. A, 2015, 45 Y. Liu, X.J. Feng, D.C. Bao, K.X. Li and M. Bao, J. Mol. Catal. A:
403, 77ꢀ83.
Chem., 2010, 323, 16ꢀ22.
20
B.N. Song, L. Guo, R. Zhang, X.G. Zhao, H.M. Gan, C. Chen, J.Z.
Chen, W.W. Zhu and Z.S. Hou, J. CO2 Utilization, 2014, 6, 62ꢀ68.
21 J.Q. Wang, J.Y. Leong and Y.G. Zhang, Green Chem., 2014, 16, 4515ꢀ
4519.
22 Mesoporous silicon materials as the supports for the conversion of CO2
with epoxides: (a) M.H. Valkenberg, C. deCastro and W.F. Holderich,
Green Chem., 2002, 4, 88ꢀ93; (b) W. Zhang, Q.X. Wang, H.H. Wu, P.
Wu and M.Y. He, Green Chem., 2014, 16, 4767ꢀ4774.
23 For recent reported literatures on cycloaddition of CO2 with epoxides
catalyzed by imidazolimꢀbased polymeric ionic liquids: (a) J.Y. Yuan
and M. Antonietti, Polymer, 2011, 52, 1469ꢀ1482;(b) Y. Xie, Z.F.
Zhang, T. Jiang, J.L. He, B.X. Han, T.B. Wu and K.L. Ding, Angew.
Chem. Int. Ed., 2007, 46, 7255ꢀ7258; (c) S. GhazaliꢀEsfahani, H.B.
Song, E. Pǎunescu, F.D. Bobbink, Z.F. Liu, G. Laurenczy, M.
Bagherzadeh, N. Yan and P.J. Dyson, Green Chem., 2013, 15, 1584ꢀ
1589.
24 Phosphoniumꢀbased polymeric ionic liquids for cycloaddition of CO2
with epoxides: (a) Y.B. Xiong, H. Wang, R.M. Wang, Y.F. Yan, B.
Zheng and Y.P. Wang, Chem. Commun., 2010, 46, 3399ꢀ3401; (b)
Q.W. Song, L.N. He, J.Q. Wang, H. Yasuda and T. Sakakura, Green
Chem., 2013, 15, 110ꢀ115; (c) T. Takahashi, T. Watahiki, S. Kitazume,
H. Yasuda and T. Sakakura, Chem. Commun., 2006, 1664ꢀ1666; (d)
Y.B. Xiong, F. Bai, Z.P. Cui, N. Guo and R.M. Wang, J. Chem., 2013,
1ꢀ9; (e) W.L. Dai, B. Jin, S.L. Luo, X.B. Luo, X.M. Tu and C.T. Au,
Catal. Today, 2014, 233, 92ꢀ99; (f) Y.B. Xiong, Y.J. Wang, H. Wang,
R.M. Wang and Z.P. Cui, J. Appl. Polym. Sci., 2012, 123, 1486ꢀ1493;
(g) Y.B. Xiong, H. Wang, R.M. Wang, Y.F. Yan, B. Zheng and Y.P.
Wang, Chem. Commun., 2010, 46, 3399ꢀ3401.
25 Y.S. Ye, J. Rick and B.J. Hwang, J. Mater. Chem. A, 2013, 1, 2719ꢀ
2743.
26 W.A. Cunningham, J. Chem. Educ., 1935, 12(3), 120ꢀ124.
27 M.A. Gauthier, M.I. Gibson and H.A. Klok, Angew. Chem. Int. Ed.,
2009, 48, 48ꢀ58.
28 Y.X. Zhou, S.Q. Hu, X.M. Ma, S.G. Liang, T. Jiang and B.X. Han, J.
Mol. Catal. A: Chem., 2008, 284, 52ꢀ57.
29 S.W. Cao, F. Tao, Y. Tang, Y.T. Li and J.Q. Yu, Chem. Soc. Rev., 2016,
45, 4747ꢀ4765.
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