Highly efficient polymer-based nanoreactors for selective oxidation of alcohols in water

Article abstract of DOI:10.1016/j.mcat.2019.110422

In this study, we demonstrate the fabrication of thermo-responsive polymer-based TEMPO nanoreactors and their application in the catalytic selective oxidation of alcohols as a highly efficient and recoverable catalyst in aqueous media. First, a diblock amphiphilic copolymer NHS-P(MMA₂₅-b-OEGMA₇₅) consisting of poly(methyl methacrylate) (PMMA) and poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA₃₀₀) with a terminal N-hydroxysuccinimide (NHS) activated ester was synthesized utilizing reversible addition–fragmentation chain transfer polymerization (RAFT) techniques. Free radical 2,2,6,6,-tetramethyipiperidinooxy (TEMPO) was then introduced into the end of the copolymer based on activated ester functionalization to afford the temperature responsive polymer-supported catalyst TEMPO-P(MMA₂₅-b-OEGMA₇₅). Next, core-shell TEMPO nanoreactors were formed through self-assembly of the amphiphilic block polymers in deionized water. The morphology of the nanoreactors was well characterized by dynamic light scattering (DLS) and scanning electron microscopy (SEM). The nanoreactors were then successfully applied in the selective oxidative of alcohols in water. A variety of aldehydes and ketones were achieved in excellent yields and selectivities in high reaction rates with low catalyst loading. The high efficiency in catalysis of the nanoreactors may attributed to the ideal environment where enhancing the interactions between the catalyst and the alcohol substrate, mimicking the environment of enzymes. The thermo-responsive polymer-based nanoreactors could be conveniently recovered in the temperature above the LCST of the polymer after extraction of product from the reaction mixture. This strategy provides an effective and cleaner way for the selective oxidative of alcohols in organic synthesis and industrial application.

Full text of DOI:10.1016/j.mcat.2019.110422

MolecularCatalysis474(2019)110422
Contents lists available at ScienceDirect
Molecular Catalysis
journal homepage: www.elsevier.com/locate/mcat
Highly efficient polymer-based nanoreactors for selective oxidation of
alcohols in water
Tao Chena,⁎, Zhenkai Xua, Lei Zhoua, Jiaqi Qiua, Maolin Wanga, Jiping Wangb,⁎
a Key Laboratory of Advanced Textile Materials & Manufacturing Technology, Ministry of Education, Eco-Dyeing and Finishing Engineering Research Center, Ministry of
Education, National Base for International Science and Technology Cooperation in Textiles and Consumer-Goods Chemistry, Zhejiang Sci-Tech University, Hangzhou,
Zhejiang, 310018, China
b Fashion College of Technology, Shanghai University of Engineering Science, Shanghai, 201620, China
A R T I C L E I N F O
A B S T R A C T
Keywords:
TEMPO
Nanoreactor
Selective oxidation of alcohol
Recoverable catalyst
In this study, we demonstrate the fabrication of thermo-responsive polymer-based TEMPO nanoreactors and
their application in the catalytic selective oxidation of alcohols as a highly efficient and recoverable catalyst in
aqueous media. First, a diblock amphiphilic copolymer NHS-P(MMA25-b-OEGMA75) consisting of poly(methyl
methacrylate) (PMMA) and poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA300) with a
terminal N-hydroxysuccinimide (NHS) activated ester was synthesized utilizing reversible addition–-
fragmentation chain transfer polymerization (RAFT) techniques. Free radical 2,2,6,6,-tetramethyipiperidinooxy
(TEMPO) was then introduced into the end of the copolymer based on activated ester functionalization to afford
the temperature responsive polymer-supported catalyst TEMPO-P(MMA25-b-OEGMA75). Next, core-shell TEMPO
nanoreactors were formed through self-assembly of the amphiphilic block polymers in deionized water. The
morphology of the nanoreactors was well characterized by dynamic light scattering (DLS) and scanning electron
microscopy (SEM). The nanoreactors were then successfully applied in the selective oxidative of alcohols in
water. A variety of aldehydes and ketones were achieved in excellent yields and selectivities in high reaction
rates with low catalyst loading. The high efficiency in catalysis of the nanoreactors may attributed to the ideal
environment where enhancing the interactions between the catalyst and the alcohol substrate, mimicking the
environment of enzymes. The thermo-responsive polymer-based nanoreactors could be conveniently recovered
in the temperature above the LCST of the polymer after extraction of product from the reaction mixture. This
strategy provides an effective and cleaner way for the selective oxidative of alcohols in organic synthesis and
industrial application.
1. Introduction
possessing poor dispersibility was adopted [12]. The development of
new polymer carrier, which possesses good solubility or dispersivity
The oxidation of alcohols into their corresponding carbonyl com-
pounds is of great importance in organic synthesis and industrial pro-
cesses owing to their wide application in drug synthesis etc. [1]. The
development of efficient catalysts for the selective oxidation of alcohols
has always been the goal of chemists. In the last decade years, 2,2,6,6-
tetramethylpiperidine-1-oxyl (TEMPO) was found to be efficient for the
selective oxidation of alcohols in combination with renewable oxidants
such as molecular oxygen, hydrogen peroxide or hypochlorite [2].
While, isolation and recovery of catalyst remain key issues for large-
scale application just as other homogeneous catalysis. To address these
shortcomings, immobilization of TEMPO onto diverse carriers to form
recoverable heterogeneous catalysts has been widely reported [3–11].
However, the activity of catalyst often decreases when carrier
combining the benefits of homogeneous and heterogeneous catalysis,
such as high activity and recyclability will be very meaningful [13–15].
On the other hand, chemical transformation is often accomplished
in nano-sized enzymes and other confined spaces under mild and green
conditions in nature. Inspired by nature, chemists attempt to construct
various nanoreactors in order to achieve efficient chemical conversion
by using the special effects in nanoreactors, such as small size effect,
surface effect, confinement effect and synergistic effect etc [16–18].
Usually, nanoreactors have good dispersibility and are easy to recycle
and reuse. In addition, the efficiency is much higher than traditional
heterogeneous catalysis due to the enhanced local substrate con-
centration, active catalyst and accordingly the interactions between the
substrate and the catalyst when the catalytic reaction is carried out in
⁎ Corresponding authors.
E-mail addresses: tao.chen@zstu.edu.cn (T. Chen), jipingwanghz@gmail.com (J. Wang).
https://doi.org/10.1016/j.mcat.2019.110422
Received 21 March 2019; Received in revised form 21 May 2019; Accepted 22 May 2019
2468-8231/©2019ElsevierB.V.Allrightsreserved.

T. Chen, et al.
MolecularCatalysis474(2019)110422
nanoreactors, [19–26].
oil (Scheme 2). The degree of polymerization was determined by the
crude 1H NMR spectroscopy. Molecular weight and dispersity were
determined by GPC with THF as an eluent and using poly(methylme-
tacrylate) (PMMA) as standards.
In recent years, core-shell type polymeric nanoreactors through self-
assembly of amphiphilic copolymers have attracted more and more
attention. In these nanoreactors, the active catalyst was encapsulated
inside the hydrophobic core, which greatly increased its concentration,
and accordingly the catalytic activity. Besides, the hydrophilic shell
made the nanoreacters evenly dispersed in water, which enabled the
catalysis in water [27–33]. In most cases, the active catalyst was in-
troduced to nanoreactors by functionalization of hydrophobic part of
amphiphilic block copolymers by chemical reactions with high speci-
ficity, or copolymerization of active catalyst-containing monomer into
the hydrophobic block. For example, Weck et al. reported a class of
shell cross-linked micelles-supported Co(III)-salen complexes, which
were prepared by the esterification reaction of hydroxyl group from
salen ligand and carboxyl groups from the hydrophobic block, then
metalated with Co(II) and oxidized to Co(III)-salen complexes. These
supported Co(III)-salen complexes displayed not only high catalytic
efficiencies but also an unique substrate selectivity [34]. In O’reilly
et al.’s study, copolymerization of monomer with a L-proline moiety in
the hydrophobic block of amphiphilic block copolymers, then self-as-
sembly to form nanoreactors for asymmetric Aldol reaction in aqueous
media was reported [35].
2.3. Preparation of TEMPO-P(MMA25-b-OEGMA75
)
To a solution of NHS-P(MMA25-b-OEGMA75) (0.5 g, 0.02 mmol) in
THF (15 mL), 4-amino-TEMPO (6.85 mg, 0.04 mmol) and TEA (10 μL,
0.072 mmol) was added under nitrogen atmosphere and the resulting
mixture was stirred at room temperature for 24 h. The product was
precipitated from cold n-hexane to yield TEMPO-P(MMA25-b-
OEGMA75) as an orange-red viscous oil (Scheme 3).
2.4. Fabrication of polymer-supported nanoreactors
20 mg of TEMPO-P(MMA25-b-OEGMA75) was added to 2 mL of de-
ionized water. The mixture was oscillated continuously to fully dis-
solve. Nanoparticles formed through self-assembly of the amphiphilic
block polymers in water. The size and morphology of the nanoreactors
were investigated by dynamic light scattering (DLS) and scanning
electron microscope (SEM).
Herein we wish to report the facile synthesis of an amphiphilic block
copolyer with a TEMPO organocatalyst in the terminal of the hydro-
phobic block, the fabrication of core-shell TEMPO nanoreactors by self-
assembly of the amphiphilic block copolymers in water, and the in-
vestigation of their catalytic activities and recyclability in the selective
oxidation of alcohols. The results demonstrate high efficiency, easy
recycling and environmental friendliness of the TEMPO-based nanor-
eactors, which highlight the potential utility of this catalysis system in
organic synthesis and industrial production.
2.5. General procedure of the catalytic oxidation of alcohols
Alcohol (0.8 mmol), NaBr (1.25 mol%), and nanoreactors (20 mg,
0.1 mol%) were added to the mixed solution of NaClO (1.0 mmol,
1.25 mol equil., 2 mL) at 0 °C. The pH value of the aqueous solution was
adjusted to 9.1 using NaHCO3. The resulting mixture was vigorously
stirred at 0 °C. After completion of the reaction, ether was added to
extract unreacted alcohol and product. The conversion and selectivity
were analyzed by GC-MS. The catalyst was left in aqueous phase and
recovered by heating and centrifugation. And the recycled catalyst was
reused for next run after careful washing with cold ether.
2. Experimental section
2.1. Preparation of NHS-PMMA25 (Macro-CTA)
3. Results and discussion
NHS-CEPA was prepared followed by our previous report [36].
Macro-CTA was prepared as below. NHS-CEPA (144.0 mg, 0.4 mmol),
methyl methacrylate (MMA) (1.00 g, 10.0 mmol), and AIBN (6.57 mg,
0.04 mmol) were added to dioxane (4 mL) in a 50 mL ampule. The re-
sulting solution was degassed by 3 freeze–pump–thaw cycles and the
ampule was refilled with nitrogen and tightly sealed. The RAFT poly-
merization was carried out at 65 °C for 24 h, after that the reaction
mixture was opened to air and cooled down. The polymer was pre-
cipitated in cold n-hexane (4˜5 °C) to yield Macro-CTA as a yellow oil
(Scheme 1). The degree of polymerization was determined by the crude
1H NMR spectroscopy. Molecular weight and dispersity were de-
termined by GPC with THF as an eluent using poly(methylmetacrylate)
(PMMA) as standards.
3.1. Synthesis and structural characterization of TEMPO-P(MMA25-b-
OEGMA75
)
In our study, macro-chain transfer agent NHS-P(MMA25) (NHS-CTA)
(Mn =3.16 kg mol−1, PDI = 1.21) (Table 1) with a terminal activated
ester functional group was synthesized by RAFT polymerization em-
ploying NHS-CEPA as the chain transfer agent. Then, an amphiphilic
diblock copolymer incorporating a NHS moiety on the hydrophobic
block side was synthesized affording a low dispersity NHS-P(MMA25-b-
OEGMA75) (Mn =23.0 kg mol−1, PDI = 1.22) (Table 1), determined by
gel permeation chromatography (GPC) (Fig. S1).
Next, TEMPO was then brought into the end of the amphiphilic
diblock copolymer through activated ester functionalization strategy,
reaction of the NHS-P(MMA25-b-OEGMA75) with 4-amino-TEMPO to
provide TEMPO-P(MMA25-b-OEGMA75) in nearly quantitative yield
(Fig. 1).
2.2. Preparation of NHS-P (MMA25-b-OEGMA75
)
Macro-CTA (286 mg, 0.10 mmol), OEGMA (1.50 g, 7.5 mmol) and
AIBN (1.64 mg, 0.01 mmol) were added to 1,4-dioxane (4 mL) in a
50 mL ampule. Similar procedure with the preparation of NHS-PMMA25
was adopted for the polymerization. The polymer was precipitated in
cold n-hexane (4˜5 °C) to yield NHS-P (MMA25-b-OEGMA75) as a yellow
The successfully introduction of TEMPO moiety into the amphi-
philic diblock copolymer was confirmed by the 1H NMR spectrum and
Electron Spin Resonance (ESR) spectrum. It can be found from 1H NMR
spectrum (Fig. S8) that the proton resonance at 2.85 ppm, which is
Scheme 1. Synthesis of Macro-CTA.
2

T. Chen, et al.
MolecularCatalysis474(2019)110422
Scheme 2. Synthesis of NHS-P(MMA25-b-OEGMA75).
Scheme 3. Synthesis of TEMPO-P(MMA25-b-OEGMA75
.
Table 1
Characterization data of the NHS-containing polymers.
Sample
Mna
Mnb
PDI
NHS-P(MMA25) (Macro-CTA)
2860
25360
3160
22980
1.21
1.22
NHS-P(MMA25-b-OEGMA75
)
a
Measured by 1H NMR (in CDCl3, Figures S6, S7).
Measured by GPC (in THF).
b
corresponded to NHS, completely disappeared after reaction.
Meanwhile, it can be seen from EPR spectrum (Fig. 2) that the char-
acteristic triplet signal of TEMPO radical appeared at 3450–3550 G.
Comparison of ESR signals of TEMPO-P(MMA25-b-OEGMA75) and 4-
Amino-TEMPO at the same molar concentration (Fig. S9), accompanied
by the observation of in 1H NMR, NHS-P(MMA25-b-OEGMA75) is con-
sidered to be fully converted to TEMPO-P(MMA25-b-OEGMA75).
Fig. 2. The triplet signal of TEMPO radical of TEMPO-P(MMA25-b-OEGMA75).
Fig. 1. Schematic illustration of the preparation of TEMPO-P(MMA25-b-OEGMA75) and formation of TEMPO-based nanoreactors.
3

T. Chen, et al.
MolecularCatalysis474(2019)110422
Fig. 3. The percent transmittance of copolymer
versus temperature by UV–vis (a), and the de-
rivation absolute value (|△S/△T |) of the
curve of transmittance versus temperature (b).
3.2. Determination of the lower critical solution temperatures (LCSTs)
reports in TEMPO catalysis confirmed this point (Table S1, entries 2˜5).
There exists a obvious decrease in catalytic activity of supported cata-
lysts such as TEMPO/magnetic polystyrene nanosphere (TEMPO/
MPNs) (TOF = 0.333 s−1) [8], microporous organic nanotube networks
(TEMPO/MONNs) (TOF = 0.199 s−1) [11], TEMPO-P(MEO2MA-co-
OEGMA), and PEG-supported TEMPO (TOF is up to 0.333 s−1) [4],
compared to homogeneous TEMPO (TOF = 0.555 s−1) [8]. While, the
TEMPO nanoreactors demonstrated remarkably high oxidative activity
(TOF = 2.667 s−1). The enhanced reaction rates may attribute to the
enzyme-mimic catalyst system, where, the hydrophobic environment
within the nanoreactors allowing hydrophobic alcohols can readily
transfer into the core of micelles. In addition, the existence of hydro-
philic ester bonds in the hydrophobic block makes certain amounts of
water, sodium hypochlorite and sodium bromide to diffuse into the
catalytic sites to facilitate the catalytic oxidation of alcohols.
The recycling of thermo-responsive polymer-based catalyst based on
its thermo-responsive property is one of the straight forward catalyst
recover methods. When the temperature is higher than its LCST in
aqueous solution, the thermo-responsive polymer turns hydrophobic,
and realizes phase separation from water [37,38]. To understand the
thermo-responsive perperty of TEMPO-P(MMA25-b-OEGMA75), its LCST
was investigated. Polymer solutions were prepared in 1.0 mg mL−1 of
aqueous solution for the UV–vis absorption measurements. Fig. 3 shows
the percentage transmittance of the samples at 500 nm probed by
UV–vis spectroscopy. By plotting the derivation absolute value with
aspect to temperature as a function of temperature (Fig. 3b), It can be
seen that the copolymer NHS-P(MMA25-b-OEGMA75) displayed thermo-
responsive property and its LCST is determined as the temperature
showing the maximum in the first derivative, which is 66.5 °C. The
LCST of TEMPO-P(MMA25-b-OEGMA75) is 0.5 °C lower than that of
NHS-P(MMA25-b-OEGMA75), which should be attributed to the sub-
stitution of NHS with a more hydrophobic TEMPO moiety.
3.5. Substrate scope study of the catalytic oxidation of alcohols
Further tests using TEMPO nanoreactors revealed that a variety of
alcohols can be oxidated to their corresponding carbonyl compounds
(Table 2). The reactions were performed at 0 °C in water for all the
substrates. The benzyl alcohols containing electron-withdrawing group
in the para position (NO2-, Br-, Cl-) were quantitatively converted into
their corresponding aldehydes within 5 min (Table 2, entries 1–3,
TOF = 2.667 s−1), similar to the unsubstituted benzyl alcohol (Table
S1, entry 6). It is noteworthy that these nanoreactors were equally
applicable in different types of aromatic alcohols such as 4-methyl-
thiobenzyl alcohol, 1-phenylethanol and 1-naphthalenemethanol
(Table 2, entries 6–8, TOF = 2.667 s−1), giving their corresponding
aldehydes in excellent conversion and selectivity. Significantly, TEMPO
nanoreactors displayed extremely high oxidative activities to the benzyl
alcohols with electron-donating group (Me-, MeO-, Ph-), offering the
respective aldehydes within 2 min (Table 2, entries 4, 5 and 9,
TOF = 6.667 s−1). Obviously, the nanoreactor is more effective than
the unloaded catalyst, only 45% conversion for the selective oxidation
of 4-phenylbenzyl alcohol was achieved when 4-amino-TEMPO was
used as catalyst (Table 2, entry 9 in parenthesis). In addition, the na-
noreactors also exhibited excellent activities in the oxidation of both
secondary benzylic and secondary aliphatic alcohols to yield the cor-
3.3. Preparation and characterization of TEMPO nanoreactors
With the amphiphilic diblock copolymer TEMPO-P(MMA25-b-
OEGMA75) in hand, the copolymer was self-assembled into micelles in
water (TEMPO nanoreactors) through direct dissolution method.
TEMPO-P(MMA25-b-OEGMA75) was dissolved into deionized water at
room temperature (T < LCST), then self-assembled until thermo-
dynamic equilibrium micelles formed (Fig. 1). The size, shape, and
distribution of this micelle system were then determined by DLS
(Fig. 4a, b) and SEM (Fig. 4c, d). Analysis of the polymeric micelles by
DLS at 1.0 mg mL−1 in water indicated that nanoparticles with an
average hydrodynamic diameter of 240 nm and particle size distribu-
tion of 1.20. To further confirm the formation of nanoparticles, the
surface topography of TEMPO nanoreactors were characterized by SEM.
Nanoparticles with a spherical morphology and average diameter of
around 300 nm was being observed, which is generally in line with the
results of DLS analysis.
3.4. Application of TEMPO nanoreactors for catalytic oxidation of alcohols
in water
responding ketones within
5 or 2 min (Table 2, entries 10–14,
TOF = 2.667˜6.667 s−1). The sterically hindered alcohols were also
effectively oxidized to their corresponding carbonyl compounds in high
conversion and excellent selectivity although somewhat longer reaction
times were required (Table 2, entries 15–18, TOF = 1.293˜2.587 s−1).
Notably, there was no obvious catalytic reaction for 2-adamantanol
when 4-amino-TEMPO was adopted as catalyst (Table 2, entries 16 in
parenthesis).
To investigate the catalytic activity of the thermo-responsive
polymer-supported TEMPO nanoreactors in the catalytic oxidation of
alcohols, the oxidation of benzyl alcohol in water was firstly chosen to
study their catalytic activity. After optimization, the reaction condition
of using sodium hypochlorite as the oxidant and sodium bromide as the
co-catalyst at pH = 9.1 and 0 °C were adopted. At the optimized reac-
tion conditions, benzyl alcohol could be selectively oxidized to the
corresponding benzaldehyde in excellent conversion and selectivity
(Table S1, entry 6). Usually, the catalytic activity of supported catalysts
decreases due to the decrease of the dispersion of the catalysts. Previous
3.6. The reuse of the TEMPO nanoreactors
After the preliminary activity study, recovery and recycling of the
4

T. Chen, et al.
MolecularCatalysis474(2019)110422
Fig. 4. DLS distribution (a) autocorrelation function (b) SEM characterization (c) and Histogram of particle size distribution obtained by SEM (d) of TEMPO
Nanoreactor.
Table 2
TEMPO nanoreactors catalyzed catalytic oxidation of alcohols to the corresponding carbonyl compoundsa.
Entry
R1 (or alcohol)
R2
Time (min)
Conv.b (%)
Sel.b(%)
TOF (s−1
)
1
2
3
4
5
6
7
8
4-NO2Ph
4-BrPh
2-ClPh
4-MePh
4-MeOPh
4-MeSPh
Bn
1-Naphthyl
4-PhPh
Ph
H
H
H
H
H
H
H
H
5
5
5
2
2
5
5
5
2
2
5
5
2
5
5
> 99
> 99
> 99
> 99
> 99
> 99
> 99
> 99
> 99 (45)
> 99
98
> 99
> 99
> 99
> 99
> 99
> 99
> 99
> 99
> 99 (> 99)
> 99
> 99
> 99
> 99
> 99
98
2.667
2.667
2.667
6.667
6.667
2.667
2.667
2.667
6.667
6.667
2.613
6.667
6.667
2.667
2.533
9c
10
11
12
13
14
15
H
Me
Me
Me
Me
Ph
4-NO2Ph
2-MeOPh
4-MeOPh
Ph
> 99
> 99
> 99
95
16c
5
97 (N.R.)
> 99
2.587
17
10
99
> 99
1.293
18
a
10
99
> 99
1.306
The reactions were performed with alcohol (0.8 mmol), TEMPO nanoreactors (0.1 mol%), NaBr (1.25 mol %), NaClO aq. (1.25 equiv.), at 0 °C, pH = 9.1.
Determined by GC-MS.
The results in parenthesis were obtained using 4-amino-TEMPO as catalyst.
b
c
5

T. Chen, et al.
MolecularCatalysis474(2019)110422
thermo-responsive polymer-supported TEMPO nanoreactors was next
investigated using the catalytic selective oxidation of benzyl alcohol as
the model reaction. After the completion of the reaction, the product
was extracted by cooled ether. Increasing the temperature of the re-
sidual aqueous phase to above the LCST of TEMPO-P(MMA25-b-
OEGMA75) at 70 °C produced the precipitate of catalyst from water.
Next, the dispersion was centrifugated with care to recover the catalyst,
and it could be reused after careful washing with cold ether. A certain
amount catalyst loss was observed, which is about 10% by calculation
from UV–vis standard curve of TEMPO-P(MMA25-b-OEGMA75) (Fig.
S2). The loss of catalyst during the recovery should be arise from the
incompletely precipitation. Scaling up production probably can reduce
the loss. In the next run, the recovered catalyst together with 10%
amount of supplement was dissolved into deionized water at room
temperature (T < LCST) to form nanoparticles, and similar activity
was achieved for at least 6 cycles (Fig. S3). Although there is room for
further improvement, this strategy represents a straightforward and
promising recycling method.
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In summary, we have successfully introduced a TEMPO organoca-
talyst to an amphiphilic block copolyers in the terminal of the hydro-
phobic part. Core-shell type of polymeric nanoreactors were fabricated
through the self-assembly of the amphiphilic block polymers in water.
The nanoractors were then successfully apllied in the selective oxida-
tive of alcohols in aqueous media. The corresponding aldehydes and
ketones were achieved in excellent yield and selectivity. Importantly,
higher TOF were achieved with both lower TEMPO loading and less
reaction time compared to the previously reported polymer-supported
TEMPO catalyst systems, which may attributed to the ideal environ-
ment for catalysis where enhancing the interactions between the cata-
lyst and the alcohol substrate, mimicking the environment of enzymes.
Furthermore, the temperature responsivity of the nanoreactors fa-
cilitated the recovery of the catalyst from the reaction system. The
catalyst can be easily recovered utilizing the thermo-responsive char-
acteristic. The thermo-responsive polymer-supported TEMPO nanor-
eactors combine product selectivity, high efficiency and easy recycling
in an environmentally safe medium, which highlights the potential
application of this nanoreactor system in the industrial practice of the
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The financial support from Zhejiang Provincial Natural Science
Foundation of China (No. LY17B020013) and Key Technology Research
and Development Project of Zhejiang Province (No. 2017C03016)
throughout the project is greatly appreciated.
Appendix A. Supplementary data
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