Pd nanoparticles supported on amphiphilic porous organic polymer as an efficient catalyst for aqueous hydrodechlorination and Suzuki-Miyaura coupling reactions

Article abstract of DOI:10.1002/aoc.5364

Developing efficient and recyclable heterogeneous catalysts for organic reactions in water is important for the sustainable development of chemical industry. In this work, Pd nanoparticles supported on DABCO-functionalized porous organic polymer was successfully prepared through an easy copolymerization and successive immobilization method. Characterization results indicated that the prepared catalyst featured big surface area, hierarchical porous structure, and excellent surface amphiphilicity. We demonstrated the use of this amphiphilic catalyst in two case reactions, i.e. the aqueous hydrodechlorination and Suzuki-Miyaura coupling reactions. Under mild reaction conditions, the catalyst showed high catalytic activities for the two reactions. In addition, the catalyst could be easily recovered and reused for several times. Also, no obvious Pd leaching and aggregation of Pd nanoparticles occurred up during the consecutive reactions.

Full text of DOI:10.1002/aoc.5364

Received: 6 August 2019
DOI: 10.1002/aoc.5364
Revised: 22 September 2019
Accepted: 16 October 2019
F U L L P A P E R
Pd nanoparticles supported on amphiphilic porous organic
polymer as an efficient catalyst for aqueous
hydrodechlorination and Suzuki‐Miyaura coupling
reactions
1
1
2
1
1
Yizhu Lei
| Wenchao Zhu | Yali Wan | Renshu Wang | Hailong Liu
1
School of Chemistry and Materials
Engineering, Liupanshui Normal
University, Liupanshui, Guizhou 553004,
China
Developing efficient and recyclable heterogeneous catalysts for organic reac-
tions in water is important for the sustainable development of chemical indus-
try. In this work, Pd nanoparticles supported on DABCO‐functionalized porous
organic polymer was successfully prepared through an easy copolymerization
and successive immobilization method. Characterization results indicated that
the prepared catalyst featured big surface area, hierarchical porous structure,
and excellent surface amphiphilicity. We demonstrated the use of this amphi-
philic catalyst in two case reactions, i.e. the aqueous hydrodechlorination
and Suzuki‐Miyaura coupling reactions. Under mild reaction conditions, the
catalyst showed high catalytic activities for the two reactions. In addition, the
catalyst could be easily recovered and reused for several times. Also, no obvi-
ous Pd leaching and aggregation of Pd nanoparticles occurred up during the
consecutive reactions.
2
School of Chemistry and Chemical
Engineering, Guizhou University,
Guiyang, Guizhou 550025, China
Correspondence
Yizhu Lei, School of Chemistry and
Materials Engineering, Liupanshui
Normal University, Liupanshui. Guizhou,
553004, China.
Email: yzleiabc@126.com
Funding information
Academician Workstation of Liupanshui
Normal University, Grant/Award Num-
ber: qiankehepingtairencai [2019]5604
hao; National Natural Science Foundation
of China, Grant/Award Number:
KEYWORDS
heterogeneous catalysis, hydrodechlorination, palladium nanoparticles, porous organic polymer,
21763017; Science and Technology Fund
Suzuki‐Miyaura coupling
Project of Guizhou Province, Grant/
Award Number: qian ke he ji chu
[2018]1414] and[2016]1133; Scientific and
Technological Innovation Platform of
Liupanshui, Grant/Award Number:
52020‐2018‐03‐02 and 52020‐2017‐02‐02
1
| INTRODUCTION
switching of homogeneous organic reactions would be
an ideal pathway for green and sustainable organic syn-
With increasing consciousness for environmental protec-
tion, the use of water as a green reaction medium for
replacing traditional organic solvents has gained consid-
thesis. Nevertheless, organic transformations in water
often suffer from poor reaction efficiency due to the high
mass transfer resistance of hydrophobic organic sub-
[1,2]
[7,8]
erable attention in recent years.
On the other hand,
strates.
Thus, synthesis of water‐compatible and effi-
heterogeneous switching of homogeneous catalysis is
considered as an important strategy for realizing environ-
cient solid catalyst that allows low mass transfer
resistance of the hydrophobic reactants in water is still a
[3–6]
[9,10]
mentally benign organic transformations.
Therefore,
challenging task.
Over the past decades, many
there is good reason to believe that developing highly effi-
cient catalyst for realizing aqueous and heterogeneous
attempts have been made to address this challenging
topic, while successful examples are limited to building
Appl Organometal Chem. 2019;e5364.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
1 of 13
https://doi.org/10.1002/aoc.5364

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LEI ET AL.
[11]
emulsion systems,
support.
and utilizing amphiphilic
polymer (P (DVB‐DABCO)). As
organocatalyst, P (DVB‐DABCO) exhibited excellent cata-
a
heterogeneous
[
9,10]
Pd nanoparticles with small diameters (1–10 nm) have
lytic activity for the transesterification of glycerol with
[
39]
been increasingly the focus of catalysis research in recent
dimethyl carbonate.
In addition to being an
[12–16]
decades.
Due to the high surface‐to‐volume ratios
organocatalyst, DABCO is also an efficient and inexpen-
sive ligand for transition metals. In 2004, Li and
and quantum size effects, Pd nanoparticles usually
[
40]
exhibited high catalytic activities in a variety of organic
coworkers
reported the first example of using DABCO
[12–16]
reactions.
However, these nanoparticles are thermo-
as an efficient ligand for palladium‐catalyzed Suzuki‐
Miyaura cross‐coupling reaction. After that, DABCO‐
metal complexes have been widely used as catalysts for
dynamically unstable and easy to form Pd agglomerates
because of their high surface energy. Generally, the aggre-
gation of Pd nanoparticles leads to rapid decrease of the
catalytic activities, and thus restricting their extensive
applications. To this end, Pd nanoparticles supported on
[
41–43]
various Cross‐Coupling reactions.
Although
DABCO‐metal complexes have been widely investigated,
DABCO‐functionalized porous organic polymer sup-
ported metal nanoparticles and their catalytic applica-
tions in water have never been investigated.
[
17,18]
a variety of porous supports, such as zeolites,
porous
[19,20]
[21]
carbons,
ordered mesoporous materials,
and
[22,23]
metal–organic frameworks (MOFs),
have been
To develop efficient and heterogeneous palladium cat-
alysts for organic reactions in water, we herein report the
synthesis (Scheme 1) and catalytic applications of palla-
dium nanoparticles supported on DABCO‐functionalized
porous organic polymer. The prepared catalyst featured
big surface area, hierarchical porous structure, and excel-
lent surface amphiphilicity. Under mild reaction condi-
tions, the catalyst exhibited high catalytic activity,
excellent aggregation resistant ability, and good reusabil-
ity for aqueous hydrodechlorination and Suzuki‐Miyaura
coupling reactions.
attempted to resolve this issue. The results suggested that
the porous supports could not noly enhance the stability
of Pd nanoparticles, but also facilitate their recovery
and reuse.
Porous organic polymers (POPs), which feature big
surface areas and designable pore structures, have gained
considerable attention recently as the solid supports to
[24–26]
stabilize metal nanoparticles.
To date, a number of
nitrogen and phosphine ligands functionalized POPs
have been developed and used as the catalyst supports
[27–29]
for palladium nanoparticles.
Due to the porous
structure and nice electron‐donating ability of the sup-
ports, these solid catalysts usually exhibited good aggre-
2 | EXPERIMENTAL
2.1 | Materials
[27–29]
gation and leaching resistant ability.
Nevertheless,
the vast majority of POPs consist of hydrophobic aromatic
frameworks, endowing the POPs with hydrophobic prop-
erty, and thus, restricting their catalytic applications in
1,4‐Diazabicyclo[2.2.2]octane (DABCO), Pd (OAc) , 4‐
vinylbenzyl chloride (90%), NaBH , aryl halides and aro-
2
[
30–32]
water.
To resolve this problem, solid catalysts could
4
[
9,33–35]
be designed to be amphiphilic.
In recent years,
matic boric acids were supplied by Energy Chemical.
Divinylbenzene (DVB, 85%) was obtained from Alfa
Aesar, washed repeatedly with NaOH solution (0.5 M)
and deionized water before use. 2,2′‐Azobis(2‐
methylpropionitrile) (AIBN) was purchased from Aladdin
Chemistry and used as received. Vinyl functionalized
DABCO monomer (DABCO monomer) was synthesized
through the quaternization reaction of DABCO and 4‐
vinylbenzyl chloride, the detailed procedures was
investigations about the catalytic applications of metal
nanoparticles supported on POPs have been widely
reported, however, studies on amphiphilic POPs sup-
ported metal nanoparticles and their catalytic applica-
[30–32]
tions in water have rarely been explored.
DABCO, a cage‐like and small diazabicyclic molecule,
has been widely used as an organocatalyst for various
[36–38]
organic reactions.
Recently, we reported the first
[
39]
example of DABCO‐functionalized porous organic
described in our previous report.
SCHEME 1 Synthesis of Pd@P(DVB‐
DABCO) catalyst.

LEI ET AL.
3 of 13
2.2 | Preparation of P (DVB‐DABCO)
2.5 | Suzuki‐Miyaura coupling reaction
DABCO‐functionalized porous organic polymer, P (DVB‐
Suzuki‐Miyaura coupling reaction was conducted in a
10 ml reaction flask. In a typical procedure, Pd@P
(DVB‐DABCO) (26.5 mg, Pd:0.005 mmol), aryl halide (1
mmoml), arylboronic acid (1.5 mmol), and K PO ▪3H O
[39]
DABCO), was prepared as our previous report.
In a
typical procedure, divinylbenzene (1.2 g), DABCO mono-
mer (0.8 g) and AIBN (50 mg) were dissolved in DMF
3
4
2
(
20 ml) in a Teflon autoclave (100 mL). Under nitrogen
(2.0 mmol) were added to deionized water (4 ml). Then,
the flask was stirred at 40 °C. After the reaction, the
resulting mixture was separated by centrifugation, the
recovered catalyst was extracted with ethanol for three
times. For the model reaction, the combined liquid was
quantitatively analyzed by gas chromatography with N,
N‐dimethylformamide as an internal standard. For inves-
tigation of the substrate scope, the combined liquid was
purified using thin‐layer chromatography with petroleum
ether as the eluting solvent. Purity of the product was
atmosphere, the autoclave was stirred at room tempera-
ture for 1 hr, then heated in a preheated oven at 100 °C
for 24 hr. After the polymerization reaction, the resulting
solid was extracted with ethanol and dried vacuum.
Then, a pale‐yellow solid was obtained and denoted as
P (DVB‐DABCO).
2
.3 | Preparation of Pd@P (DVB‐DABCO)
1
analyzed by H NMR. All of the obtained products are
known compounds, and have been reported as our previ-
ously report.
Generally, P (DVB‐DABCO) (1.0 g) was added to a stirred
solution of palladium acetate (0.044 g) in 30 ml ethanol,
the resulting suspension was stirred at room temperature
for 12 hr. Then, a solution of sodium borohydride (0.22 g)
in 5 ml ethanol was added to the suspension dropwise
and the resulting mixture was magnetically stirred for
[
32]
2.6 | Characterization
Nitrogen sorption isotherms of the samples was deter-
mined by a Micrometrics ASAP 2020 system at 77 K. FT‐
IR was analyzed on a Bruker Equinox 55 FT‐IR spectro-
2
hr. The resulting solid was separated by filtration,
washed repeatedly with ethanol and deionized water,
and then dried under vacuum. The obtained gray solid
−
1
photometer using KBr pellet technique at a 2 cm resolu-
tion. TEM image was obtained on a FEI Tecnai G2 F30 type
microscope. SEM image was recorded on a Hitachi S‐4800
type microscope. Palladium contents were measured using
an ICP‐PerkinElmer Optima 8000 instrument. XPS was
recorded on a VG multilab 2000 spectrometer equipped
with a Mg‐AlKa X‐ray source. Contact angle was measured
(1.0 g) was denoted as Pd@P (DVB‐DABCO). The palla-
dium loading of Pd@P (DVB‐DABCO) was 2.0 wt% as
determined by ICP analysis.
2.4 | Hydrodechlorination reaction
1
on a Dataphysics OCA20 system. H NMR analysis was
performed on a Bruker AVANCE III NMR spectrometer
The hydrodechlorination reaction was carried out in a
0 ml reaction flask which fitted with H balloon. Gener-
(
400 MHz). Gas chromatography (GC) analysis was carried
1
2
out on a Scientific™ TRACE™ 1310 (TRACE TR‐WAX
capillary column) with a FID detector.
ally, Pd@P (DVB‐DABCO) (21.2 mg, Pd: 0.004 mmol),
aryl chloride (1 mmol), and NaOH (0.048 g, 1.2 mmol)
were added to deionized water (4 ml). Then, the mixture
was magnetically stirred at 25 °C under balloon of H2.
After the reaction, the resulting mixture was separated
by centrifugation, the solid was extracted with ethanol
for three times. The combined liquid was quantitatively
by gas chromatography with biphenyl or N,N‐
dimethylformamide as an internal standard.
3 | RESULTS AND DISCUSSION
3.1 | Characterization of the catalyst
As shown in Table 1, the results of Brunauer–Emmett–
Teller (BET) analyses revealed that BET surface areas of
TABLE 1 Physical properties of the P (DVB‐DABCO) and Pd@P (DVB‐DABCO)
2
−1
3
a
b
Entry
Catalysts
S
BET (m ·g
)
Pore volume (cm /g)
Average pore radius (nm)
1
2
P (DVB‐DABCO)
412
384
0.64
0.55
6.2
5.1
Pd@P (DVB‐DABCO)
a
o
Single point adsorption total pore volume of pores at P/P = 0.95.
b
Adsorption average pore diameter (4 V/A by BET).

4
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LEI ET AL.
P (DVB‐DABCO) and Pd@P (DVB‐DABCO) were 412
2
−1
and 384 m ·g , respectively. After supporting Pd nano-
particles, the surface area, pore volume and average pore
radius of Pd@P (DVB‐DABCO) decreased slightly. The
decrease of these physical properties could be attributed
to the partial pore filling with Pd nanoparticles.
Nitrogen adsorption–desorption isotherms of P (DVB‐
DABCO) and Pd@P (DVB‐DABCO) were shown in
Figure 1. The two samples displayed the combined sorp-
tion behavior of type I and type IV by IUPAC classifica-
tion. The steep nitrogen gas uptake at low relative
pressure (P/P < 0.01) indicated the abundance of micro-
0
pores, the slight hysteresis loops at P/P = 0.7–1.0 regions
0
implied the presence of mesopores; while the adsorption
at medium to high pressure regions (P/P = 0.8–1.0) sug-
0
gested the presence of macropores. Pore size distribution
curves (Figure 2) of P (DVB‐DABCO) and Pd@P (DVB‐
DABCO) by NLDFT calculation method further demon-
strated that the obtained samples had broad pore size dis-
tribution, comprising of micropores, mesopores and
macropores. For solid catalyst, the abundant micropores
facilitate the dispersion and stabilization of metal nano-
particles, while the big surface area and presence of
mesopores and macropores in the solid catalyst could
minimize diffusion barriers and enhance mass transport
FIGURE 2 Pore size distribution curves of P(DVB‐DABCO) and
Pd@P(DVB‐DABCO) by NLDFT method
showed similar morphology, indicating that Pd@P
(DVB‐DABCO) retained very well morphology of the P
(DVB‐DABCO) support. TEM characterization was used
to analyze the particle size of Pd nanoparticles in the
Pd@P (DVB‐DABCO) catalyst. As shown in Figure 3c‐
d, the TEM images of Pd@P (DVB‐DABCO) showed
that Pd nanoparticles was well distributed in the sup-
port with a relatively narrow size distribution. In
Figure 3d, the average diameter of Pd clusters was
about 2.8 nm.
[24–29]
of the reactants.
Thus, it is reasonable to expect that
the prepared solid catalyst would be a promising choice
for heterogeneous catalyst due to its hierarchical porous
structure and big surface area.
SEM characterization was used to analyze the mor-
phology of the as‐synthesized P (DVB‐DABCO) and
Pd@P (DVB‐DABCO). It can be observed from Figure 3
a‐b that P (DVB‐DABCO) and Pd@P (DVB‐DABCO)
FT‐IR spectra of P (DVB‐DABCO) and Pd@P (DVB‐
DABCO) were shown in Figure 4. The results revealed
FIGURE 1 Nitrogen adsorption (solid)‐
desorption (open) isotherms of P(DVB‐
DABCO) and Pd@P(DVB‐DABCO)

LEI ET AL.
5 of 13
FIGURE 3 SEM and TEM images of the samples. SEM images of (a) P(DVB‐DABCO) and (b) Pd@P(DVB‐DABCO); (c‐d) TEM images of
Pd@P(DVB‐DABCO) at different magnification.
FIGURE 4 FT‐IR spectra of (a) P(DVB‐
DABCO) and (b) Pd@P(DVB‐DABCO)
that P (DVB‐DABCO) and Pd@P (DVB‐DABCO) have
almost the same characteristic peaks of infrared absorp-
tion (Figure 4, a and b), indicating no obvious structure
change after Pd immobilization. The absorption peaks at
−
1
2921 and 2841 cm could be attributed to the stretching
[
39]
vibration of ‐CH and ‐CH groups.
The peaks bands at
2

6
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LEI ET AL.
−
1
1
607 and 1453 cm
should be assigned to the C‐C
Previous results suggested that surface wettability of
the solid catalysts has great influence on their catalytic
[39]
stretching vibration of aromatic ring.
[
9,30–35,44]
XPS studies were carried out to analyze the elemental
compositions and electronic states of Pd species in the
samples. As shown in Figure 5a, XPS full spectra of P
performances in water.
To test the surface wetta-
bility of Pd@P (DVB‐DABCO), contact angle measure-
ments were carried out. For comparison, the contact
angle of P (DVB‐DABCO) towards water and methyl-
benzene was also tested. Figure 6a‐b illustrated the
contact angles of P (DVB‐DABCO) and Pd@P (DVB‐
DABCO) for water. Interestingly, the water droplets were
quickly absorbed by the two samples without any residue,
suggesting the excellent hydrophilic properties of P
(DVB‐DABCO) and Pd@P (DVB‐DABCO). Thus, the con-
tact angles of the support and catalyst for water were
recorded as 0°. Figure 6c‐d illustrated the contact angles
of P (DVB‐DABCO) and Pd@P (DVB‐DABCO) towards
methylbenzene. Similarly, methylbenzene droplets were
quickly absorbed by the two samples without any residue,
suggesting their high lipophilicity. Experimental results
of contact angle measurements revealed that the prepared
Pd@P (DVB‐DABCO) has excellent surface amphi-
philicity. For solid catalyst in water, the excellent hydro-
philicity enables the catalyst well disperse in water,
while the excellent lipophilicity could enrich organic sub-
strates in the porous framework of the catalyst, and thus
(
DVB‐DABCO) and Pd@P (DVB‐DABCO) validated the
presence of N, C and Cl elements in the two samples.
Besides, an additional Pd 3d band was observed for
Pd@P (DVB‐DABCO), suggesting the successful immobi-
lization of palladium species in Pd@P (DVB‐DABCO)
catalyst. Pd 3d XPS spectrum in Figure 5b revealed that
Pd species had the binding energies of 341.0 eV and
3
35.5 eV, corresponding to binding energies of Pd 3d3/2
and Pd 3d5/2, respectively. This indicated that Pd species
in Pd@P (DVB‐DABCO) was present in a zero state, thus
proving the success reduction of Pd species in Pd@P
(
DVB‐DABCO) catalyst.
[
30–32,44]
accelerating the reaction rate.
Hence, it is not
unreasonable to expect that the prepared solid could be
a promising heterogeneous catalyst for catalyzing organic
reactions in water due to its excellent surface
amphiphilicity and porous structure.
3.2 | Hydrodechlorination of aryl chloride
The goal for preparation of porous and amphiphilic poly-
mer supported nanopalladium is to develop efficient het-
erogeneous catalyst for aqueous organic reactions. With
the expected material in hand, hydrodechlorination of
aryl chloride, which is regarded as the most promising
approach for the safe disposal of chlorinated organic pol-
[
45–47]
lutants in water,
was employed to investigate the
catalytic performance of the obtained Pd@P (DVB‐
DABCO). Firstly, hydrodechlorination of 4‐chlorophenol
with H was chosen as a model reaction to optimize the
2
reaction conditions. The model reaction was carried out
at room temperature under balloon pressure of H , the
2
results were summarized in Table 2. To our delight, the
reaction occurred smoothly at room temperature. With
0.5 mol% of Pd usage, a moderate conversion (60%) of 4‐
chlorophenol and yield (60%) of phenol were obtained
within 3 hr using Et N as a base (Table 2, entry 1). Under
3
Ar atmosphere, no hydrodechlorination product was
detected (Table 2, entry 2), suggesting the necessity of
H . The reaction was also carried out in the absence of
2
FIGURE
5
(a) XPS full spectra of P(DVB‐DABCO) and
Pd@P(DVB‐DABCO) (elemental scan); (b) Pd3d XPS spectrum of
Pd@P(DVB‐DABCO)

LEI ET AL.
7 of 13
FIGURE 6 Images of contact angle measurements for the samples. Photograph of a water droplet for (a) P(DVB‐DABCO) and (b)
Pd@P(DVB‐DABCO), photograph of a methylbenzene droplet for (c) P(DVB‐DABCO) and (d) Pd@P(DVB‐DABCO)
a
TABLE 2 Hydrodechlorination of 4‐chlorophenol under various conditions
b
b,c
d
Entry
Base
T (h)
Conv. (mol%)
Yield (mol%)
TOF
1
Et
Et
‐
3
3
N
N
3
3
3
3
3
3
3
3
2
1
2
2
60
‐
60
‐
40
‐
e
2
3
4
5
6
7
8
9
21
79
72
>99
33
84
98
87
96
84
21
79
70
>99
33
84
98
86
96
84
14
DABCO
DBU
53
47
NaOH
66
NaHCO
Na CO
3
22
2
3
56
NaOH
NaOH
NaOH
NaOH
98
10
11
12
172
120
140
f
g
a
Reaction conditions: Pd@P (DVB‐DABCO) (0.5 mol% Pd), H
800 rpm).
2
(balloon), 4‐chlorophenol (1.0 mmol), base (1.2 mmol), water (4 ml), 25 °C, stirring speed
(
b
GC yields.
c
The total yields of phenol and sodium phenoxide.
d
−1
−1
(
mol product) h (mol Pd) .
e
Under balloon of Ar.
f
Pd@P (DVB‐DABCO) (0.4 mol% Pd).
g
Pd@P (DVB‐DABCO) (0.3 mol% Pd).
base, the result indicated that the absence of base dimin-
ished the catalytic efficiency (Table 2, entry 3). Considering
the significant influence of base, different inorganic and
organic bases were also tested (Table 2, entries 4–8).
Among them, NaOH afforded the highest catalytic activity,
and > 99% yield of hydrodechlorination product was

8
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LEI ET AL.
FIGURE
hydrodechlorination of 4‐chlorophenol. Reaction conditions:
Pd@P(DVB‐DABCO) (0.4 mol% Pd), H2 (balloon), 4‐chlorophenol
1.0 mmol), NaOH (1.2 mmol), water (4 ml), 2 hr, 25 °C, stirring
7
Reuse
of
Pd@P(DVB‐DABCO)
for
the
(
speed (800 rpm)
FIGURE 8 TEM images of the 6th recycling Pd@P(DVB‐
DABCO) catalyst after the hydrodechlorination of 4‐chlorophenol

LEI ET AL.
9 of 13
a
TABLE 4 Hydrodechlorination of various aryl chlorides with Pd@P (DVB‐DABCO)
b
b
Entry
R
T (h)
Conv. (mol%)
Yield (mol%)
1
2
3
4
5
6
7
8
p‐Me
2
3
3
3
2
2
2
2
2
6
93
97
91
98
99
93
99
95
82
97
93
97
91
98
99
91
99
95
82
97
m‐Me
o‐Me
p‐OMe
p‐NH
2
p‐COMe
p‐COOH
p‐F
9
p‐Ph
c
1
0
a
Reaction conditions: Pd@P (DVB‐DABCO) (0.4 mol% Pd), H
800 rpm).
2
(balloon), 4‐chlorophenol (1.0 mmol), NaOH (1.2 mmol), water (4 ml), 25 °C, stirring speed
(
b
GC yields.
,4‐dichlorophenol (0.5 mmol).
c
2
a
TABLE 5 Effects of base and catalyst loading
b
b
c
Entry
Base
Catal. loading (mol%)
Yield (mol%)
TOF
1
2
3
4
5
6
7
8
9
K
K
2
3
CO
3
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.25
0.1
0.5
0.5
0.5
75
92
53
86
37
80
90
68
66
21
97
95
24
19
23
13
22
9
PO
4
▪3H
2
O
KOH
Cs CO
NaHCO
2
3
3
DABCO
DBU
20
23
17
33
26
22
24
6
3
Et N
K
K
K
K
K
3
PO
PO
PO
PO
PO
4
4
4
4
4
▪3H
▪3H
▪3H
▪3H
▪3H
2
2
2
2
2
O
O
O
O
O
1
1
1
1
0
1
2
3
3
3
3
3
d
e
e,f
a
Reaction conditions: Pd@P (DVB‐DABCO) (0.5 mol%), bromobenzene (1.0 mmol), phenylboronic acid (1.5 mmol), base (2 mmol), water (4 ml), 40 °C, 8 hr,
stirring speed (800 rpm).
b
GC yields.
c
−1
−1
(
mol product) h (mol Pd) .
d
e
9
hr.
25 °C, 15 hr.
f
Pd@UPOP‐1, 0.5 mol% Pd.

10 of 13
LEI ET AL.
obtained (Table 2, entry 6). Then, the effect of reaction time
and catalyst usage were investigated (Table 2, entries 9–
heterogeneous property of the catalyst, Pd leaching
during the catalytic reaction was also studied. Pd@P
1
2). Under the optimal reaction conditions, a 0.4 mol% of
palladium catalyst usage was sufficient for high conversion
96%) of 4‐chlorophenol within 2 hr, achieving a high TOF
(DVB‐DABCO)
catalysed
hydrodechlorination
of
4‐chlorophenol was allowed to react for 1 hr firstly, the
conversion of 4‐chlorophenol reached to 77%. Then, the
catalyst was filtered off. The resulting liquid mixture
was added into another reaction tube and allowed to stir
(
−
1
of 120 h (Table 2, entry 11). Thus, without any surfac-
tants,
[45]
a highly active solid catalyst was obtained for
the hydrodechlorination of 4‐chlorophenol in water.
The comparison results of Pd@P (DVB‐DABCO) with
some typical Pd‐loaded catalysts for the hydro-
dechlorination of 4‐chlorophenol were listed in Table 3.
The results indicated that the obtained Pd@P (DVB‐
for 2 hr under balloon pressure of H . No conversion
2
increase was observed after 2 hr. Besides, the Pd content
in the liquid mixture was also measured by ICP, the
result suggested that the Pd leaching was quite low, to
be ca. 0.1 ppm, thus verifying the heterogeneity of the
Pd@P (DVB‐DABCO) catalyst.
[46]
DABCO) herein showed comparable
and higher cata-
[47]
[48]
lytic activities than Pd‐IL/AC‐cr,
Fe O @PPY@Pd,
PdNP@AT‐mont.,
Next, we tested the scope and generality of the catalytic
system. Aryl chlorides bearing different functional groups
were investigated, and the results were summarized in
Table 4. Para‐, meta‐ and ortho‐methyl‐substituted aryl
chlorides reacted smoothly under the optimal reaction
conditions, achieving high yields of dechlorinated prod-
ucts within 3 hr (Table 4, entries 1–3). It was also observed
that para‐substituted aryl chlorides with different
electron‐donating and electron‐withdrawing groups were
also well tolerated, affording moderate to excellent yields
of dechlorinated products in 2 hr (Table 4, entries 4–9).
Additionally, as a representative example of polyha-
logenated substrate, 2,4‐dichlorophenol was dechlorinated
to 97% yield of phenol in 6 hr (Table 4, entry 10). Thus, this
study offers an active and heterogeneous catalyst for the
hydrodechlorination of aryl chloride in water.
3
4
[49]
[50]
[51]
Pd/MSC,
Pd/SiO ‐ODPA,
2
[52]
[53]
Pd/clay,
and AgPd /C.
This superior catalytic activ-
4
ity may be attributed to the porous and amphiphilic prop-
erties of Pd@P (DVB‐DABCO), which benefit the mass
transfer of 4‐chlorophenol in water.
Then, recycling experiment of Pd@P (DVB‐DABCO)
was conducted. After the catalytic reaction, the recovered
catalyst was washed with ethanol and water for three
times. Then, the recycling solid was directly used for the
next catalytic run. As shown in Figure 7, after reusing
for six times, Pd@P (DVB‐DABCO) was still capable of
catalysing the hydrodechlorination of 4‐chlorophenol in
9
1% yield, suggesting that the prepared Pd@P (DVB‐
DABCO) was quite robust under the reaction conditions.
Pd content of the Pd@P (DVB‐DABCO) after reusing 6
times was 1.97 wt% as determined by ICP. TEM images
(Figure 8) of the recycled catalyst suggested that no sig-
nificant change of morphology and no obvious aggrega-
tion of Pd nanoparticles occurred up during the
recycling. These results further verified the robustness
of the Pd@P (DVB‐DABCO) catalyst. To conform the
3.3 | Suzuki–Miyaura coupling reaction
To further verify the catalytic performance of Pd@P
(DVB‐DABCO) in water, Suzuki‐Miyaura coupling of aryl
TABLE 6 Comparing the performance of different solid catalysts in the coupling of bromobenzene and phenylboronic acid
Entry
Catalysts
Pd (mol%)
Conditions
O, 40 °C
EtOH/H O, 80 °C
T (h)
Yield(%)
Run
Ref.
1
2
3
4
5
6
7
8
Pd@P (DVB‐DABCO)
Phen‐Pd‐MOP
0.5
0.6
0.6
1
H
2
9
0.5
4
97
99
75
99
99
99.6
98
80
6
12
12
5
Present work
[
[
[
[
[
[
[
54]
54]
32]
6]
2
Phen‐Pd‐MOP
H
2
H
2
H
2
O, 80 °C
O, 25 °C
O, 100 °C
Pd@UPOP‐1
18
3
Pd/KAPs (DCM‐TPP)
Pd@PFN‐P
1.29
0.1
0.12
0.1
5
55]
56]
57]
EtOH/H
2
2
O, 80 °C
O, 60 °C
6
5
Fe
3
O
4
@SiO
2
@N,S‐wG@Pd
EtOH/H
0.5
8
7
PAA/PVA
H
2
O, 80 °C
5
Nanofiber‐NHC‐Pd
(NHC)Pd‐rGO
[
[
[
58]
59]
60]
9
0.2
EtOH, 75 °C
EtOH/H O, 80 °C
O, 50 °C
2
3
3
98
92
91
6
4
7
1
1
0
1
(1,4‐C
6
H
4
)(GO‐CPTMS@HPTPy‐Pd‐TPy)
2
1.38
0.01
2
M‐GO/(AM‐MBA‐β‐CD@Pd)
H
2

LEI ET AL.
11 of 13
[8,16,32,42]
halide, which is a typical coupling reaction,
was
the influence of base was first investigated (Table 5,
employed as the second case reaction. The coupling of
phenylboronic acid with bromobenzene was chosen as a
model reaction (Table 5). With 0.5 mol% of Pd usage,
entries 1–8). Among the bases examined, K PO ▪3H O
3
4
2
afforded the highest catalytic activity, achieving 92% yield
of biphenyl at 40 °C in 8 hr (Table 5, entry 2). Decreasing
the Pd usage to 0.25 mol%, biphenyl was gained in 66%
−
1
yield with a TOF of 33 h (Table 5, entry 9). Prolonging
the reaction time to 9 hr, 97% yield of biphenyl was
obtained (Table 5, entry 11). Interestingly, Pd@P (DVB‐
DABCO) was also quite efficient at 25 °C, and 95% yield
of biphenyl could be gained in 15 hr (Table 5, entry 12).
For comparison, palladium supported on urea‐based
amphiphilic porous organic polymer (Pd@UPOP‐1), a
heterogeneous catalyst for aqueous Suzuki–Miyaura cou-
[
32]
pling reaction that we reported recently,
was also
tested under the same reaction conditions. However, only
24% yield of biphenyl was obtained (Table 5, entry 13).
The comparison results of Pd@P (DVB‐DABCO) with
some recent heterogeneous catalysts for the coupling of
bromobenzene and phenylboronic acid were also listed
(
(
Table 6). Under the mild reaction conditions, Pd@P
DVB‐DABCO) showed moderate activity among the
FIGURE 9 Reuse of Pd@P(DVB‐DABCO) for Suzuki‐Miyaura
coupling of bromobenzene and phenylboronic acid. Reaction
conditions: Pd@P(DVB‐DABCO) (0.5mol% Pd), bromobenzene (1.0
mmol), phenylboronic acid (1.5 mmol), K3PO4?3H2O (2 mmol),
water (4 ml), 40 °C, 9 hr, stirring speed (800 rpm).
reported solid catalysts (Table 6, entries 2–12). Although
Pd@P (DVB‐DABCO) showed moderate catalytic activity
for this coupling reaction, it should be noted that Pd@P
(DVB‐DABCO) is more in line with the requirements of
a
TABLE 7 Suzuki–Miyaura coupling reaction catalysed by Pd@P (DVB‐DABCO)
1
2
b
Entry
R
R
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
9
p‐Me
m‐Me
o‐Me
p‐OMe
p‐OH
p‐COMe
p‐CN
H
H
9
9
94
90
94
88
96
92
94
95
93
96
72
H
H
12
15
7
H
H
H
8
H
8
p‐Me
p‐OMe
p‐CN
H
9
H
9
1
1
0
1
H
9
c
12
c
1
2
H
20
17
a
3 4 2
Reaction conditions: Pd@UPOP‐1 (0.5 mol% Pd), aryl bromide (1.0 mmol), arylboronic acid (1.5 mmol), K PO 3H O (2.0 mmol), water (4 ml), 40 °C, stirring
speed (800 rpm).
b
Isolated yields.
c
Aryl chlorides as the substrate.

12 of 13
LEI ET AL.
green synthesis such as pure water reaction medium,
mild reaction temperature, and facile preparation
procedure.
occurred up during the consecutive reactions. In light of
the easy preparation, good catalytic performance and
excellent water stability of the present Pd@P (DVB‐
DABCO) catalyst, the results in this study would provide
an efficient method and good reference for developing
water‐compatible heterogeneous nanometal catalysts.
Next, the recyclability of Pd@P (DVB‐DABCO) cata-
lyst was investigated over the coupling of phenylboronic
acid with bromobenzene. After the completion of the
model reaction, the recovered catalyst was washed with
ethanol and water for three times, and then subjected to
the next catalytic run. As depicted in Figure 9, the
Pd@P (DVB‐DABCO) catalyst could be effectively reused
for five times with only a slight decrease of its activity.
Thus, this result further verified the robustness of the pre-
pared Pd@P (DVB‐DABCO) in water‐mediated reactions.
To investigate the scope and limitations of the Pd@P
ACKNOWLEDGMENTS
This work is financial supported by the National Natural
Science Foundation of China [grant number 21763017];
the Science and Technology Fund Project of Guizhou
Province [grant number qian ke he ji chu [2018]1414]
and[2016]1133]; the Scientific and Technological Innova-
tion Platform of Liupanshui (52020‐2018‐03‐02 and
52020‐2017‐02‐02); the Academician Workstation of
Liupanshui Normal University (qiankehepingtairencai
[2019]5604 hao); and the Fund of Liupanshui Normal
University (LPSSYZDXK201602).
(DVB‐DABCO) catalyst in Suzuki–Miyaura coupling
reaction, aryl bromides and aryl boronic acids bearing dif-
ferent functional groups were tested. The results were
summarized in Table 7. Firstly, the coupling reactions
between substituted aryl bromides and phenylboronic
were investigated (Table 7, entries 1–7). The results
revealed that aryl bromides bearing both electron‐
withdrawing and electron‐donating groups could react
smoothly with phenylboronic, affording the correspond-
ing biaryls in good to excellent yields within 15 hr. Then,
the scope of arylboronic acids was also examined with
several typical arylboronic acids (Table 7, entries 8–10).
High yields of biaryls were gained in 9 hr regardless of
the electronic property of the substituted groups. Chloro-
benzene and 4‐nitrochlorobenzene, as two representative
substrates of aryl chlorides, were also tested under the
optimal conditions. 72% yield of target biaryl was gained
for 4‐nitrochlorobenzene (Table 7, entry 11). However,
only 17% yield of biphenyl was gained for chlorobenzene
ORCID
Yizhu Lei https://orcid.org/0000-0002-9247-6000
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