Urea-based amphiphilic porous organic polymer-supported palladium as a reusable catalyst for Suzuki–Miyaura coupling and hydroxycarbonylation reactions in water

Article abstract of DOI:10.1002/aoc.4421

The development of environmentally friendly heterogeneous catalysts for organic reactions in water is becoming of growing importance for the development of sustainable processes. In this work, a porous organic polymer-supported palladium catalyst (Pd@UPOP-1) was successfully fabricated from 3,3′-diaminobenzidine and methylenediphenyl diisocyanate through a facile urea-forming condensation reaction. The structure and composition of the catalyst were characterized using several physicochemical methods. Pd@UPOP-1 was found to possess good porous structure and excellent amphiphilicity. Under mild reaction conditions, the catalyst showed excellent catalytic activity and good substrate compatibility for the Suzuki–Miyaura coupling reaction of aryl bromides, as well as the hydroxycarbonylation reaction of aryl iodides. In addition, the catalyst could be used for several consecutive recycles in both cases.

Full text of DOI:10.1002/aoc.4421

Received: 25 February 2018
DOI: 10.1002/aoc.4421
Revised: 9 April 2018
Accepted: 14 April 2018
F U L L P A P E R
Urea‐based amphiphilic porous organic polymer‐supported
palladium as a reusable catalyst for Suzuki–Miyaura
coupling and hydroxycarbonylation reactions in water
Yizhu Lei1
| Guosong Lan1 | Dajian Zhu2 | Renshu Wang1 | Xiao‐Yu Zhou1 | Guangxing Li2
1 School of Chemistry and Materials
Engineering, Liupanshui Normal
University, Liupanshui, Guizhou 553004,
People's Republic of China
2 School of Chemistry and Chemical
Engineering, Huazhong University of
Science and Technology, Luoyu Road
1037, Wuhan, Hubei 430074, People's
Republic of China
The development of environmentally friendly heterogeneous catalysts for
organic reactions in water is becoming of growing importance for the
development of sustainable processes. In this work, a porous organic poly-
mer‐supported palladium catalyst (Pd@UPOP‐1) was successfully fabricated
from 3,3′‐diaminobenzidine and methylenediphenyl diisocyanate through a
facile urea‐forming condensation reaction. The structure and composition of
the catalyst were characterized using several physicochemical methods.
Pd@UPOP‐1 was found to possess good porous structure and excellent
amphiphilicity. Under mild reaction conditions, the catalyst showed excellent
catalytic activity and good substrate compatibility for the Suzuki–Miyaura
coupling reaction of aryl bromides, as well as the hydroxycarbonylation
reaction of aryl iodides. In addition, the catalyst could be used for several
consecutive recycles in both cases.
Correspondence
Yizhu Lei, School of Chemistry and
Materials Engineering, Liupanshui
Normal University, Liupanshui, Guizhou
553004, China.
Email: yzleiabc@126.com
Guangxing Li, School of Chemistry and
Chemical Engineering, Huazhong
University of Science and Technology,
Wuhan, Hubei 430074, China.
Email: ligxabc@163.com
KEYWORDS
amphiphilicity, carbonylation, palladium, porous organic polymer, water
Funding information
Liupanshui Key Laboratory of High Per-
formance Fibers and Advanced Porous
Materials, Grant/Award Number: 52020‐
2017‐02‐02; National Natural Science
Foundation of China, Grant/Award
Number: No. 21763017; Guizhou Key
Built Discipline Project, Grant/Award
Number: ZDXK[2016]24; School‐Level
Key Discipline of Chemistry, Grant/
Award Number: LPSSYZDXK201602;
Science and Technology Fund Project of
Guizhou Province, Grant/Award Number:
qian ke he ji chu [2016]1133 and qian ke
he ji chu [2018]1414; Youth Talent
Growth Project of Educational Depart-
ment of Guizhou Province, Grant/Award
Number: qian jiao he KY [2016]264; Sci-
ence and Technology Creative Team Pro-
ject of Liupanshui Normal University,
Grant/Award Number:
LPSSYKJTD201501
Appl Organometal Chem. 2018;e4421.
wileyonlinelibrary.com/journal/aoc
Copyright © 2018 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4421

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LEI ET AL.
the facile urea‐forming condensation reaction, though it
needs tedious reaction procedures and the use of
hypertoxic chemicals.[36] Very recently, we reported a
facile method for the preparation of amphiphilic porous
polyurea (UPOP) via the condensation of readily avail-
able 3,3′‐diaminobenzidine (DAB) and 1,4‐phenylene
1 | INTRODUCTION
Water is a cheap, safe and nontoxic solvent and has thus
attracted considerable attention when it is used as a
solvent in organic synthesis.[1–3] Meanwhile, the
functionalization of aryl halides is of major importance
in the field of modern organic chemistry due to the ubiq-
uity of aromatic and heteroaromatic units.[4–6] However,
the catalytic transformations of aryl halides in water
generally require water‐soluble homogeneous catalysts,
which suffer from practical problems such as catalyst sep-
aration and recycling.[3,7–9] In addition, homogeneous
systems generally induce contamination of the ligand
and metal residue in products.[10,11] From the standpoint
of green and sustainable organic synthesis, environmen-
tally friendly, efficient and recyclable heterogeneous cata-
lysts for transformation reactions of aryl halides in water
offer a solution to these vital problems by facilitating
product separation and catalyst reuse.[12–17]
Palladium complexes represent the most powerful
catalysts for coupling reactions of aryl halides.[18] In this
regard, great effort has been made to immobilize palla-
dium complexes on various organic and inorganic solid
supports to create heterogeneous catalysts,[19–23] as well
as these hydrophilic heterogeneous catalysts being used
in aqueous conditions.[24] Among various catalytic sup-
ports, polymers have attracted great attention due to their
excellent capability of post‐synthetic modification.[21,22]
However, catalysts supported on traditional polymers
have basic problems in terms of tedious synthetic routes,
fewer and inhomogeneously distributed active sites, low
specific surface area, poor stability, as well as low effi-
ciency in mass transport.[25] Hence, developing more
active and heterogeneous catalytic systems is imperative
and merits further study.
diisocyanate,[13] and
a
UPOP‐supported palladium
catalyst exhibited excellent catalytic activity for
aminocarbonylation reactions in water.
In order to explore the generality of the preparation
strategy of urea‐based amphiphilic polymer and extend
the applications of UPOP to different catalytic reactions,
in the work reported in this paper, an amphiphilic porous
organic polymer‐supported palladium (Pd@UPOP‐1)
catalyst was fabricated via the urea‐forming condensation
of DAB and methylenediphenyl diisocyanate (MDI),
followed by immobilization of palladium acetate
(Scheme 1). The catalytic performances of Pd@UPOP‐1
were evaluated for the Suzuki–Miyaura coupling and
hydroxycarbonylation reactions of aryl halides in water.
2 | EXPERIMENTAL
2.1 | Materials
DAB (99%) and MDI (98%) were obtained from Meryer
Chemical Technology (Shanghai) Co. Ltd, and used as
received. Palladium acetate (99%) was purchased from
Energy Chemical (Shanghai) Co. Ltd. Aryl halides,
arylboronic acids and bases were of analytical reagent
grade. 1,4‐Dioxane was an analytical reagent and purified
by refluxing over sodium. CO with a purity of 99.99% was
purchased from a local manufacturer.
2.2 | Preparation of Porous Polymer
Porous organic polymers (POPs), which feature high
surface areas and designable pore structures, have
attracted great attention recently due to their potential
to combine the best features of homogeneous catalysts
and heterogeneous catalysts.[25–30] A series of POPs con-
taining various nitrogen ligands and phosphine ligands
have been successfully synthesized and used as catalyst
supports.[31–33] Results showed that some of them even
exhibited higher catalytic activities than the correspond-
ing homogeneous counterparts. However, the over-
whelming majority of POPs mainly consist of
hydrophobic aromatic frameworks, which lead to their
poor dispersion in water and results in low accessibility
towards substrates.[34,35] Hence, the construction of
porous polymers with both porosity and good hydrophi-
licity still remains to be explored. In 2014, Wang and
co‐workers[36] made an important contribution to the
preparation of amphiphilic porous polymers by using
UPOP‐1 was prepared according to the synthetic proce-
dure for UPOP with some modifications.[13] Generally,
freshly dehydrated 1,4‐dioxane (80 ml) was added to a
250 ml flask, followed by the addition of 2.0 g of MDI
(8.0 mmol). After the mixture was heated to 80 °C, a solu-
tion of DAB (0.85 g, 4.0 mmol) in 80 ml of 1,4‐dioxane
was added slowly in an oil bath and then stirred at
80 °C for 4 days. After the reaction, the resulting pale‐yel-
low solid was washed with methanol, tetrahydrofuran
and diethyl ether, and dried under vacuum (2.82 g). The
prepared polymer was designated as UPOP‐1.
2.3 | Preparation of Catalyst
Pd@UPOP‐1 was obtained following the same procedures
as for the synthesis of Pd@UPOP.[13] Generally, UPOP‐1
(1.0 g) was added to a solution of palladium acetate

LEI ET AL.
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SCHEME 1 Synthesis of urea‐based amphiphilic polymer‐supported palladium catalyst
(0.0443 g) in 30 ml of dichloromethane and stirred at
room temperature for 12 h. Pd@UPOP‐1 was collected
with a Hirsch funnel, washed with acetone, purified by
Soxhlet extraction with acetone for 24 h and then dried
under vacuum. The palladium content was 1.9 wt% as
determined using atomic absorption spectroscopy.
extracted with copious methanol and the combined liquid
was acidic to litmus with HCl (5 wt%). Then, the liquid
was extracted five times with 5 ml of EtOAc. The
combined organic layers were dried over MgSO4 and vac-
uum‐evaporated to afford the products. Purity of products
1
was determined using by H NMR analysis (Supporting
Information) and yields were based on aryl iodides.
2.4 | Typical Procedure for Suzuki–
Miyaura Coupling Reactions
2.6 | Adsorption of Chlorobenzene
Suzuki–Miyaura coupling reactions were performed
under ambient conditions in a 10 ml reaction flask. Gen-
erally, Pd@UPOP‐1 containing 1 mol% Pd, aryl bromide
(0.5 mmol), arylboronic acid (0.75 mmol), base (1.0 mmol)
and water (4 ml) were loaded into the flask. Then, the
flask was stirred at 25 °C until aryl bromide was totally
consumed (determined by TLC). For the coupling reac-
tions of aryl chlorides, the reaction was heated at 85 °C
for 24 h. After that, the mixture was separated by centri-
fugation and the catalyst was extracted with copious ethyl
acetate. Then, the combined liquid was concentrated and
purified by TLC using petroleum ether as eluting solvent.
The adsorption capacity of Pd@UPOP‐1 for chloroben-
zene was determined as follows. Generally, Pd@UPOP
(0.3 g) was added to 2.0 g of chlorobenzene in 20 ml of
deionized water under magnetic stirring. After stirring
at 25 °C for 60 min, the mixture was centrifuged at
5000 rpm for 10 min. The obtained solid was extracted
four times with 5 ml of ethanol, and the collected ethanol
was then analyzed with gas chromatography.
2.7 | Characterization
Nitrogen sorption isotherms were obtained with a
Micrometrics ASAP 2020 system at 77 K, the polymer
being pretreated under vacuum at 100 °C for 5 h before
the measurements. The surface area was calculated using
the Brunauer–Emmett–Teller (BET) method. The pore
size distribution was calculated using the nonlocal den-
sity functional theory (NLDFT) method. Fourier trans-
form infrared (FT‐IR) spectroscopy was conducted with
a Bruker Equinox 55 FT‐IR spectrophotometer using the
KBr pellet technique, over the range 400–4000 cm−1 at a
resolution of 2 cm−1. The size and morphology of the
polymer was observed with a Hitachi SU8000 field emis-
sion scanning electron microscopy (SEM) instrument.
X‐ray photoelectron spectroscopy (XPS) measurements
of the polymer and catalyst were carried out with a VG
Multilab 2000 spectrometer using a Mg‐AlKa X‐ray
source, and the C1s transition was adjusted to 284.8 eV.
1
Purity of products was determined using H NMR analy-
sis (Supporting Information) and yields were based on
aryl bromides.
2.5 | Typical Procedure for
Hydroxycarbonylation Reactions
These catalytic reactions were carried out in a Teflon‐
lined stainless steel autoclave (50 ml) that was equipped
with a magnetic stirrer bar and an automatic temperature
controller. In a typical experiment, Pd@PUP‐1 containing
1 mol% Pd, aryl iodide (1.0 mmol), K2CO3 (1.0 mmol) and
deionized water (5 ml) were added to the autoclave. After
purging four times with CO, the autoclave was pressur-
ized with CO to 5 bar. Then, the reaction was allowed
to react at 100 °C for a definite time. The resulting
mixture was separated by centrifugation. The solid was
Thermogravimetric analysis was conducted with
a

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LEI ET AL.
NETZSCH STA 449 F5 instrument under a dynamic
nitrogen atmosphere, and the sample was heated from
room temperature to 600 °C at a heating rate of
10 °C min−1 1H NMR spectra were recorded with a
.
Bruker Avance III NMR spectrometer (400 and
100 MHz) at ambient temperature. The contact angles
were measured with a Dataphysics OCA 20 system.
Atomic absorption spectroscopy was performed with a
PerkinElmer AA‐300 spectrophotometer. GC analysis
was performed using a Scientific™ TRACE™ 1310 appa-
ratus equipped with a TRACE TR‐WAX capillary column
and a flame ionization detector.
3 | RESULTS AND DISCUSSION
3.1 | Characterization of Catalyst
The FT‐IR spectra of UPOP‐1, Pd@UPOP‐1 and reactive
monomers are shown in Figure 1. MDI shows a
stretching band of isocyanate at 2278 cm−1. While the
band at 2278 cm−1 was absent in the spectrum of
UPOP‐1, and a new stretching band of C═O at
1650 cm−1 emerged. These results suggest that the
condensation reaction between DAB and MDI was
finished.[13,36]
XPS studies were performed to investigate the ele-
mental compositions of the surface and coordination
states of Pd species. In Figure 2(a), the XPS results for
UPOP‐1 validated that C, N and O elements were present
in the polymer. The XPS spectrum of Pd@UPOP‐1
(Figure 2b) revealed that Pd species were present in the
Pd2+ state, corresponding to a binding energy of
337.7 eV in the Pd 3d5/2 level. In comparison with that
of free Pd (OAc)2 (338.4 eV),[37] the Pd2+ binding energy
in the Pd@UPOP shifted negatively by 0.7 eV, which
FIGURE 2 XPS spectra: (a) XPS spectra of UPOP‐1 and
Pd@UPOP‐1 (elemental scan); (b) XPS spectrum of Pd in
Pd@UPOP‐1
should be attributed to the interaction of Pd (OAc)2 with
the UPOP‐1 support.
The thermogravimetric analysis of UPOP‐1 is depicted
in Figure 3. There is no obvious weight loss below 250 °C,
and rapid weight loss that takes place at 280–550 °C, sug-
gesting that UPOP‐1 can be stable at least up to 250 °C.
Nitrogen adsorption–desorption isotherms and pore
size distribution curve of UPOP‐1 are shown in Figure 4.
The sample exhibits typical sorption behavior of type IV.
A sharp rise at medium‐ and high‐pressure regions
(P/P0 = 0.8–1.0) indicates the presence of macropores.
The appearance of hysteresis could be an indicator for
the softness of UPOP‐1, demonstrating the deformation
and swelling of the network.[38] UPOP‐1 has a BET sur-
face area of 146 m2 g−1. The pore size distribution curve
(inset of Figure 4) of UPOP‐1 based upon the NLDFT cal-
culation method reveals that the sample has a very broad
FIGURE 1 FT‐IR spectra of DAB, MDI, UPOP‐1 and Pd@UPOP‐1

LEI ET AL.
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quickly absorbed without any residue, and the contact
angle was recorded as 0°. The catalyst was also dispersed
in water and hexane to further investigate its
amphiphilicity (Figure 7). The results show that
Pd@UPOP‐1 was well dispersible in water and retained
in the aqueous phase in a water–hexane biphasic system.
These results suggest that the synthesized Pd@UPOP‐1
has good amphiphilic property. The hydrophilicity could
be ascribed to the hydrophilic urea moieties, and the
strong oleophilicity was ascribed to the presence of
hydrophobic composition of phenyl rings. Thus, a porous
and amphiphilic catalytic support for heterogeneous
catalysis was achieved.
3.2 | Suzuki–Miyaura Coupling Reactions
FIGURE 3 Thermogravimetric analysis of UPOP‐1
For the purpose of extending the applications of urea‐
based amphiphilic polymer catalyst, the catalytic perfor-
mance of Pd@UPOP‐1 was initially evaluated for the
Suzuki‐Miyaura coupling reaction of aryl bromides in
pure water. Our study began with the coupling reaction
of bromobenzene and phenylboronic acid in the presence
of K2CO3 as base. After reacting at room temperature for
12 h, 1.0 mol% Pd@UPOP‐1 gave a GC yield of biphenyl
of 81% with nearly 100% selectivity (Table 1, entry 1). Pre-
vious research indicated that bases had significant effects
on the activity of the Suzuki–Miyaura coupling reac-
tion.[39] Hence, several organic and inorganic bases were
investigated for this coupling reaction (Table 1, entries
2–6). Among the bases screened, K2CO3 was identified
as optimal, providing a GC yield of 99% after a prolonged
reaction time (Table 1, entry 7). Thus, a highly active cat-
alyst was obtained for the Suzuki–Miyaura coupling reac-
tion. Given the structure and properties of Pd@UPOP‐1,
its excellent catalytic performance should be attributed
to the special amphiphilic porous structure. The good
hydrophilicity enabled its effective dispersion in water
and good contact with organic substrates, while the
porous structure and strong oleophilicity provided a
microenvironment with high concentration of organic
substrates inside the frameworks. As a proof of high con-
centration of organic substrates inside the frameworks,
an adsorption experiment in water showed that the
adsorption capacity of Pd@UPOP‐1 for chlorobenzene
was 2907 mg g−1, while the solubility of chlorobenzene
in water was only 0.4 mg g−1 under the same conditions.
With the optimal conditions in hand, we next investi-
gated the scope and generality of this Suzuki–Miyaura
coupling reaction (Table 2). Firstly, various aryl bromides
were examined using phenylboronic acids as the coupling
partners. The results showed that aryl bromides bearing
both electron‐withdrawing and electron‐donating groups
participated in the reactions readily, affording the
FIGURE
4
Nitrogen adsorption (filled symbols)–desorption
(open symbols) isotherms and pore size distribution curve of
UPOP‐1
pore size distribution, suggesting its hierarchical porous
structure comprised of micropores and mesopores.
SEM and transmission electron microscopy (TEM)
images of UPOP‐1 are shown in Figure 5. The images
show that that UPOP‐1 exhibited a sponge‐like three‐
dimensional network morphology with abundant
macroporous structures. Thus, SEM and TEM images
provide further evidence of porosity.
Given that hydrophilic urea linkages could impart
wettability to UPOP‐1, the wettability of Pd@UPOP‐1
polymer was thus investigated. The wettability was firstly
examined using contact angle measurements. Figure 6
illustrates the contact angles of Pd@UPOP‐1 for water
and salad oil droplets. The contact angle between
Pd@UPOP‐1 and water was about 53°, indicating a good
hydrophilicity. While for salad oil, the droplet was

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LEI ET AL.
FIGURE 5 (a, b) SEM and (c, d) TEM images of UPOP‐1
FIGURE 7 Hydrophilic measurements of Pd@UPOP‐1: in water
(left); in water–hexane (right)
electronic nature of the aryl boronic acids (Table 2,
entries 11–14). Activated aryl chlorides, such as 4‐CN‐,
4‐NO2‐ and 4‐CF3‐substituted chlorobenzenes, were also
investigated under the optimized reaction conditions.
Unfortunately, no target biaryls were detected after the
reaction. On further elevating the reaction temperature
to 85 °C, moderate yields of corresponding biaryls were
obtained after 24 h (Table 2, entries 15–17).
In addition to catalytic activity, the recovery and reus-
ability of the catalyst are also crucial in the evaluation of
economic feasibility of a catalytic process. To evaluate the
recyclability and reusability of the Pd@UPOP‐1 catalyst,
we performed the Suzuki–Miyaura coupling reaction of
FIGURE
6
Images of contact angle measurements for
Pd@UPOP‐1: (a) photograph of a water droplet; (b) photograph of
a salad oil droplet
corresponding biaryl products in good to excellent yields
within 30 h (Table 2, entries 1–10). The scope of
arylboronic acids for this catalytic Suzuki–Miyaura
coupling reaction was also examined. The reactions with
various arylboronic acids proceeded smoothly, and excel-
lent yields of biaryls were obtained regardless of the

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TABLE 1 Effect of catalyst and basea
Entry
Base
Time (h)
Yield (%)b
1
2
3
4
5
6
7
K2CO3
K3PO4
KHCO3
KOH
12
12
12
12
12
12
18
81
64
47
54
79
77
99
DBU
Et3N
K2CO3
aReaction conditions: Pd@UPOP‐1 (1.0 mol% Pd), bromobenzene (0.5 mmol),
phenylboronic acid (0.75 mmol), base (1 mmol), water (4 ml), 25 °C, stirring
speed of 600 rpm.
FIGURE 8 Reuse of Pd@UPOP‐1 catalyst for Suzuki–Miyaura
cross‐coupling reaction. Reaction conditions: Pd@UPOP‐1
(1.0 mol% Pd), p‐bromoanisole (1.0 mmol), phenylboronic acid
(1.5 mmol), K2CO3 (2.0 mmol), water (5 ml), 25 °C, 25 h, stirring
speed of 600 rpm
bGC yield.
TABLE 2 Suzuki–Miyaura coupling reaction catalyzed by
Pd@UPOPa
p‐bromoanisole with phenylboronic acid under the
optimized reaction conditions. After the completion of
the reaction, the reaction mixture was centrifuged and
filtered. The recovered Pd@UPOP‐1 was washed with
methanol and dried under vacuum at 60 °C before use
for the next catalytic run. The obtained liquid was ana-
lyzed using GC. Figure 8 shows that Pd@UPOP‐1 could
be effectively used up to four times with a slight decrease
of its activity observed. XPS analysis of recovered
Pd@UPOP‐1 after four recycles (Figure 9) showed the
coexistence of Pd(0) and Pd (II) species in the recycled
catalyst, and the ratio of Pd0/Pd2+ is 1.83 as estimated
by the proportion of relative peak areas. This suggested
that the reduction of Pd2+ occurred during the reaction.
Entry R1
R2
Time (h) Yield (%)b
1
p‐Me
H
24
26
28
24
25
24
18
16
15
30
18
18
94
99
97
93
92
99
91
96
95
98
97
97
99
94
70
2
m‐Me
o‐Me
p‐F
H
3
H
4
H
5
p‐OMe
p‐OH
p‐CHO
p‐COMe
p‐CN
p‐C6H5
H
H
6
H
7
H
8
H
9
H
10
11
12
13
14
15c
H
p‐Me
o‐Me
H
H
p‐COMe 18
H
p‐CN
18
24
H
16c
17c
H
H
24
24
87
65
aReaction conditions: Pd@UPOP‐1 (1.0 mol% Pd), aryl bromide (1.0 mmol),
arylboronic acid (1.5 mmol), K2CO3 (2.0 mmol), water (5 ml), 25 °C, stirring
speed of 600 rpm.
bIsolated yield.
cAryl chlorides as substrate, reaction temperature was 85 °C.
FIGURE 9 Pd 3d XPS spectrum of the recovered Pd@UPOP‐1

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LEI ET AL.
TABLE 3 Hydroxycarbonylation of iodobenzenea
carried out with 1 mol% Pd@UPOP‐1 as the catalyst, a
yield of 64% of benzoic acid was obtained in 5 h
(Table 3, entry 1). Further optimizing the base and reac-
tion time, 1 mol% Pd@UPOP‐1 provided a yield of 90%
of benzoic acid in 10 h with K2CO3 as the base (Table 3,
entry 3). After initial experimentation, the reaction
mixture was filtered. The recovered Pd@UPOP‐1 was
washed with sufficient methanol and dried under
vacuum. Then, the solid was subjected to the next run
of hydroxycarbonylation by charging with the same
substrates, base and solvent. The results show that
Pd@UPOP‐1 could be effectively recycled and reused for
up to four consecutive runs.
Various aryl iodides were used to investigate the scope
of this catalytic hydroxycarbonylation (Table 4). When
the reaction was performed in water at 100 °C for
10–15 h, a variety of aryl iodides could be carbonylated
to the corresponding aryl acids in moderate yields. Aryl
iodides bearing different functional groups, such as p‐
CH3, p‐OCH3, p‐OH, p‐C, and p‐NO2, were well tolerated,
and the electronic nature of substituent groups had no
obvious effect on the yields of the reaction (Table 4,
entries 1–7). 2‐Iodopyridine, as a representative example
of an aromatic heterocyclic iodide, afforded the target
acid in a yield of 37%.
Entry
Base
Time (h)
Recycle no.
Yield (%)b
1
2c
3
4
5
6
7
K2CO3
KOH
5
Fresh
64
77
90
91
88
89
82
10
10
10
10
10
12
Fresh
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
0 (fresh)
1
2
3
4
aReaction conditions: Pd catalyst (1.0 mol%), iodobenzene (1.0 mmol),
K2CO3 (1.0 mmol), water (5 ml), 100 °C, CO (5 atm), stirring speed of
600 rpm.
bIsolated yield.
cKOH (2.0 mmol).
TABLE 4 Hydroxycarbonylation of aryl iodidesa
Entry
R
Time (h)
Yield (%)b
1
2
3
4
5
6
7
8
p‐Me
p‐OMe
p‐OH
p‐NO2
p‐Cl
12
12
10
10
10
10
12
15
85
89
91
87
87
84
85
37
4 | CONCLUSIONS
An amphiphilic POP‐supported palladium catalyst was
easily fabricated via a facile urea‐forming condensation
reaction. Characterization results show that the prepared
polymer possesses relatively high surface area, hierarchi-
cal porosity and amphiphilicity. Under mild reaction con-
ditions, the catalyst displayed excellent catalytic activities
for two types of organic reaction in water: (i) Suzuki–
Miyaura coupling of aryl bromides and (ii)
hydroxycarbonylation of aryl iodides. The high catalytic
performance in water could be attributed to the amphi-
philic and porous structure of the catalyst, which could
provide a microenvironment with a high concentration
of organic substrates inside the frameworks. Further-
more, the catalyst can be easily recovered and reused sev-
eral times without significant loss of catalytic activity.
The result obtained in this study could offer an attractive
method and good reference for the development of het-
erogeneous catalysts in water.
m‐Cl
o‐Cl
aReaction conditions: Pd catalyst (1.0 mol%), aryl iodide (1.0 mmol), K2CO3
(1.0 mmol), water (5 ml), 100 °C, CO (5 atm), stirring speed of 600 rpm.
bIsolated yield.
3.3 | Hydroxycarbonylation Reactions
Benzoic acids are common structural motifs in many nat-
ural products, pharmaceuticals and agrochemicals.[40,41]
Palladium‐catalyzed hydroxycarbonylation of aryl halides
represents a widely used approach for preparing such
compounds. The encouraging catalytic performance of
Pd@UPOP‐1 in Suzuki–Miyaura coupling reactions
prompted us to further explore it application in the
hydroxycarbonylation of aryl iodides. When the
hydroxycarbonylation reaction of iodobenzene was
ACKNOWLEDGMENTS
This work was financially supported by the National
Natural Science Foundation of China (no. 21763017),
the Youth Talent Growth Project of Educational

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[2018]1414), the Science and Technology Creative
Team Project of Liupanshui Normal University
(LPSSYKJTD201501), Guizhou Key Built Discipline
Project (ZDXK[2016]24), the School‐Level Key Discipline
of Chemistry (LPSSYZDXK201602) and the Liupanshui
Key Laboratory of High Performance Fibers and
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SUPPORTING INFORMATION
Additional supporting information may be found online
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