A robust phenazine-containing organic polymer as catalyst for amine oxidative coupling reactions

Article abstract of DOI:10.1016/j.jcat.2020.03.031

Here we present the design and synthesis of a new robust microporous organic polymer (TPBP) decorated with phenazine groups which endowed reversibly redox-active properties. The obtained TPBP possesses relatively high surface area (359 m²/g) and good thermal stability. TPBP exhibits excellent catalytic capability for the oxidative homocoupling of amines with high activity and selectivity toward target products. Besides, this metal-free catalyst demonstrated excellent recyclability after 6 cycles under the investigated conditions. By means of EPR and UV-vis spectroscopy, a plausible mechanism of the amine oxidative coupling reaction was deduced via a single electron transfer from TPBP radical cations to amine substrates.

Full text of DOI:10.1016/j.jcat.2020.03.031

Journal of Catalysis 385 (2020) 338–344
Contents lists available at ScienceDirect
Journal of Catalysis
journal homepage: www.elsevier.com/locate/jcat
A robust phenazine-containing organic polymer as catalyst for amine
oxidative coupling reactions
a
Junyu Lin a, Zhiyong Guo a,b, , Hongbing Zhan
⇑
a College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108, Fujian, PR China
b Key Laboratory of Eco-materials Advanced Technology, Fuzhou University, Fuzhou 350108, Fujian, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Here we present the design and synthesis of a new robust microporous organic polymer (TPBP) decorated
with phenazine groups which endowed reversibly redox-active properties. The obtained TPBP possesses
relatively high surface area (359 m2/g) and good thermal stability. TPBP exhibits excellent catalytic capa-
bility for the oxidative homocoupling of amines with high activity and selectivity toward target products.
Besides, this metal-free catalyst demonstrated excellent recyclability after 6 cycles under the investigated
conditions. By means of EPR and UV-vis spectroscopy, a plausible mechanism of the amine oxidative cou-
pling reaction was deduced via a single electron transfer from TPBP radical cations to amine substrates.
Ó 2020 Elsevier Inc. All rights reserved.
Received 11 January 2020
Revised 24 March 2020
Accepted 26 March 2020
Keywords:
Phenazine
Microporous organic polymers
Radical cations
Amine homocoupling
Heterogeneous catalyst
1. Introduction
struction of phenazines are Rh-catalyzed amination-cyclization-
aromatization cascade reported by Lian et al. [30], and Pd-
Microporous organic polymers (MOPs), which are designed and
synthesized by the structural and functional organic building
blocks, have drawn tremendous scientific interest because of the
intrinsic properties and related applications, such as gas storage
[1–5], molecular separation [6,7], heterogeneous catalysis [8–13],
organic electronic [14] and biomedical application [15]. MOPs have
numerous advantages over traditional porous materials such as
diverse building blocks, low density, large surface areas, tunable
porous structure, and high thermal and chemical stability [16–
18]. During the past decade, a variety of MOPs have been effec-
tively prepared based on many types of reactions such as Friedel-
Crafts arylation [19,20], Suzuki cross-coupling reaction [21],
cyclotrimerization [22], Sonogashira-Hagihara reaction [23,24],
Schiff-base reaction [25], Buchwald-Hartwig [26] and Yamamoto
coupling reaction [27]. Moreover, the copious tactics of building
units and post-modification make MOPs an effective way for devel-
oping functional organic porous materials [28].
catalyzed domino double-arylations proposed by Laha et al. [31].
Phenazine has many modification sites and these derivative com-
pounds have a variety of fascinating properties and application.
Especially the reduced phenazine, which possesses strong
electron-donating ability and good stability, has been designed as
fluorescent probes [32], catalysts for the esterification of alcohol
and aldehyde [33] and active materials for organic batteries [34].
Among those reduced products, dihydrophenazine derivatives pro-
duced radical cations via simple one-electron oxidation reaction
have been particularly attractive to researchers and widely used
in electro-, photo- and magneto-chemical compounds. Based on
the properties of radical cations, Miyake et al. [35] employed it
as an outstanding catalyst in atom transfer radical polymerization
driven by visible light. Dai et al. [36] assembled a dual-ion organic
symmetric cell by introducing 4, 40-(phenazine-5, 10-diyl)
dibenzoate as a bipolar active material, and it exhibits an average
discharge voltage of 2.5 V and an energy density of 127 W kgꢀ1
at 1°C.
Phenazine, a kind of redox-active compounds with the core
structure of pyrazine ring, can be structurally modified by a variety
of convenient synthetic methods [29]. Among those reported syn-
thetic methods, the most promising strategies for the ring con-
Recently, Mejía et al. [37] synthesized a series of N, N’-disubsti
tuted-dihydrophenazines and utilized their radical cations as effi-
cient metal-free catalysts for the oxidative homo- and cross-
coupling of a variety of different amines. However, like other pre-
vious reports, the current usage of pyrazine radical cation as cata-
lysts is still limited in homogenous states, which greatly hinder
their applications in industry. Herein, we synthesized a robust
⇑
Corresponding author at: College of Materials Science and Engineering, Fuzhou
University, Fuzhou 350108, China.
E-mail address: guozhy@fzu.edu.cn (Z. Guo).
https://doi.org/10.1016/j.jcat.2020.03.031
0021-9517/Ó 2020 Elsevier Inc. All rights reserved.

J. Lin et al. / Journal of Catalysis 385 (2020) 338–344
339
microporous polymer decorated with phenazine groups and fur-
2.2. Catalytic activity test of TPBP
ther demonstrated its excellent catalytic capability in oxidative
coupling of amines as well as good recyclability.
General procedure for oxidative coupling of benzyl amines:
2 mg (0.017 mmol) NOBF4 and 0.4 mL acetonitrile were placed in
a 3 mL centrifuge tube to obtain solution A. Solution A was later
added to a 10 mL single-necked round flask containing 20 mg
(0.017 mmol) TPBP, and then the whole system was bubbled with
N2 to release NO. In the meanwhile, BF-4 was remaining in the solu-
tion as a counterion to get a TPBP radical cation. Benzyl amine
0.6 mL (5.5 mmol) was added subsequently. Finally, the reaction
mixture was stirred at 100 °C for 16 h under an oxygen atmosphere
(1 bar). This catalytic testing approach was then applied to other
various substituted benzyl amines. The catalytic reaction products
were determined by GCMS or 1H NMR spectroscopy.
2. Experimental section
2.1. Materials and synthesis
Preparation of 2,4,6-tris(4-bromophenyl)-1,3,5-triazine (TBT):
2,4,6-tris(4-bromophenyl)-1,3,5-triazine was synthesized from 4-
bromobenzonitrile according to previous report [38].
Preparation of TPBP: Phenazine (170 mg, 0.944 mmol) was dis-
solved in 5 mL ethanol in a three-neck flask and heated to 80 °C
under N2 atmosphere. Then, a solution of sodium dithionite
(1.6 g, 9.190 mmol) in 40 mL water was added and a pale green
precipitate appeared. After stirred at 100 °C for 3 h under nitrogen
protection, the mixture was isolated via vacuum filtration and
acquired 5,10-dihydrophenazine as a pale green solid. A round-
bottom flask was charged with 5, 10-dihydrophenazine, TBT
(305 mg, 0.562 mmol), potassium carbonate (1.3 g, 9.406 mmol),
and toluene (50 mL). The mixture was heated to 80 °C under an
atmosphere of nitrogen. After that, palladium(II) acetate
(26.3 mg, 0.117 mmol) and tri-tert-butylphosphine (1 mL) were
added into the reaction mixture, and the solution was stirred at
120 °C for 48 h. After the mixture was cooled to room temperature,
the brown precipitate was then filtered and washed with distilled
water and methanol. The precipitate was further Soxhlet extrac-
tion with boiling methanol, dichloromethane, and acetone to
remove unreacted monomers or catalysts. The collected solid
was dried at 80 °C under vacuum (Scheme 1).
2.3. Recyclability test of the catalytic reaction
After the catalytic reaction finished, the solid catalyst was iso-
lated from the liquid phase by centrifugation. The recycled catalyst
was washed with ethanol 5 times and then dried at 80 °C subse-
quently. The recycled catalyst was re-oxidized by NOBF4 in addi-
tional runs.
2.4. Instrumentation
Brunauere-Emmette-Teller (BET) surface areas were performed
by N2 adsorption/desorption isotherm using a Micromeritics ASAP
2020 instrument at 77 K. TPBP was activated at 100 °C until outgas
rate reached 3
lmHg/min before the BET measurement. Powder X-
ray diffraction (PXRD) measurements were carried out on a Rigaku
Scheme 1. Synthesis of microporous organic polymer with phenazine group (TPBP).

340
J. Lin et al. / Journal of Catalysis 385 (2020) 338–344
Miniflex 600 diffractometer with Cu K
a
radiation (40 kV, 15 mA,
Fig. S1a and S1b. The XPS signal of C1s certified the chemical states
of carbon included CAC/C@C/CAH (284.8 eV) and CAN/C@N
(286.7 eV). The XPS signal of N1s showed the charts of TPBP con-
tained -N= (398.7 eV) and -N- (399.9 eV). ICP-MS result showed
that there is negligible palladium existing in TPBP. The 13C solid
state NMR spectrum was also used to study the local structures
of TPBP. As depicted in Fig. 1b, the peak at dc = 170 ppm belonged
to the carbon of triazine rings and other peak located at
105 ~ 150 ppm is ascribed to the carbon atoms of the benzene
groups. The resonance peak at 142 ppm was assigned to the carbon
atoms of CAN between triazine ring and phenazine. All of the
above characterizations clearly suggested that the obtained solid
is the target product.
The porosity properties of TPBP were analyzed by nitrogen
adsorption/desorption isotherms at 77 K. In order to remove the
residual compounds within the porous framework, TPBP was
washed thoroughly with low boiling point solvents, and then
degassed under high vacuum at 100 °C for 10 h. As shown in
Fig. 2a, TPBP exhibited a combination of type I and type IV nitrogen
isotherms according to the IUPAC classification. The nitrogen iso-
therm curves shown a steep rise of N2 uptake at a low relative
pressure P/P0, indicated the existence of abundant micropores.
The gradual rising of N2 uptake in the P/P0 ranging from 0.1 to
0.99 in the isotherm indicated the existence of a few mesopores
and macropores. The Brunauer-Emmett-Teller (BET) surface areas
of TPBP were calculated to be 359 m2 gꢀ1 and the total volume
(P/P0 = 0.99) was 0.313 cm3 gꢀ1, respectively. The pore size distri-
bution (PSD) of TPBP was calculated by the nonlocal density func-
tional theory (NLDFT) approach. As shown in Fig. 2b, 1.4 and
1.8 nm pores are dominant in polymer TPBP, which clearly indi-
cates its microporous nature.
k = 0.1541 nm). Fourier transform infrared (FT-IR) Spectra were
collected on a Thermo Nicolet 5700 spectrometer with the KBr pel-
let technique. Thermo-gravimetric analyses (TGA) were obtained
using a Netzsch STA449-F5 analyzer under N2 atmosphere at the
heating rate of 10 °C minꢀ1 within a temperature range of 30–
900 °C. Electron paramagnetic resonance (EPR) measurements
were carried out on a Bruker model A300 spectrometer. X-ray pho-
toelectron spectroscopy (XPS) measurements were performed on a
Thermo ESCALAB 250 spectrometer, using non-monochromatic Al
Ka X-rays as the excitation source and choosing C 1 s (284.6 eV)
as the reference line. UV-visible (UV-vis) spectra were recorded
at room temperature on an Agilent Cary 7000 in the wavelength
range of 200–1500 nm. Transmission Electron Microscope (TEM)
images were collected on a Tecnai G2 F20. Scanning electron micro-
scope (SEM) images were obtained on a FEI Nova NanoSEM 230. 1H
NMR spectra were recorded on a Bruker AVANCE III NMR spec-
trometer at 400 MHz, respectively, using tetramethylsilane (TMS)
as an internal standard. Solid-state 13C CP/MAS NMR was per-
formed on a Bruker SB AVANCE III 500 MHz spectrometer with a
4-mm double-resonance MAS probe. GC-MS determinations were
performed using an Agilent Technologies 7890B GC system with
5977B MSD and a column of Agilent 19091S-433UI HP-5MS. The
oven temperature program of GC measurements was 30 °C
(3 min), 30–300 °C (20 °C/min), 300 °C (3 min). Palladium content
in TPBP was determined using inductively coupled plasma-mass
spectrometry (ICP-MS, XSERIES 2).
3. Results and discussion
3.1. Structural characterization
The powder- X-ray- diffraction (PXRD) patterns showed no
characteristic peak, indicating the amorphous nature of this poly-
mer (Fig. 3a). Thermogravimetric analysis (TGA) measurement
was carried out to study the thermal stability of TPBP. As shown
in Fig. 3b, TPBP exhibits comparative good thermal stability. Under
the N2 atmosphere, it showed no more than 5% weight loss under
420 °C. Scanning-electron microscopy (SEM) images of the pre-
pared polymer networks are shown in Fig. 3c and 3d. The low mag-
nifications images demonstrated the irregular morphology
resulted from aggregation of small particles. Further magnification
showed the existence of clustered particles, which was common
among polymers with the size range between 50 and 600 nm.
Transmission electron microscopy (TEM) was used to investigate
the microstructure of the formed TPBP materials. The high-
resolution TEM images illustrated the amorphous structure of TPBP
and the existence of homogenous pore constituted an extended
As shown in Scheme 1, phenazine and TBT were successfully
coupled to afford TPBP as a brown powder, which was insoluble
in common organic solvents, such as acetone, ethanol and N, N’-
dimethylformamide. TPBP was further detailed characterized by
Fourier transform infrared spectroscopy (FTIR), X-ray photoelec-
tron spectroscopy (XPS), and 13C cross-polarization magic-angle
spinning (CP/MAS) NMR spectrum. The FTIR spectra of the polymer
and its building monomers are shown in Fig. 1a. The peaks at
1593 cmꢀ1, 1506 cmꢀ1 and 1307 cmꢀ1 are assigned to the triazine
rings. The new vibration band at 1330 cmꢀ1 is corresponding to the
C-N stretching vibrations in the polymer TPBP, while the disap-
pearance vibration band at 495 cmꢀ1 is C-Br stretching vibration
of the monomer TBT. These FTIR profiles together suggest the suc-
cessful coupling reaction between TBT and phenazine. The results
of the XPS verified the two characteristic elements C and N in
Fig. 1. (a) IR spectra of TBT (black line), phenazine (red line) and TPBP (blue line). (b) Solid-state 13C CP-MAS NMR spectrum of TPBP.

J. Lin et al. / Journal of Catalysis 385 (2020) 338–344
341
Fig. 2. (a) Nitrogen-sorption isotherm at 77 K and (b) pore-size distribution of TPBP.
Fig. 3. (a) Powder X-ray diffraction patterns of TPBP (black line) and TPBP after the catalysis of the amine oxidative coupling reaction (red line). (b) TGA of TPBP with a heating
rate of 5 °C /min in the range of 35–900 °C under N2. (c), (d) SEM images and (e), (f) TEM images of TPBP.
network in the polymer (Fig. 3e). TEM images of TPBP also disclose
the presence of a continuous microporous structure (Fig. 3f).
with alcohols [33]. To investigate catalytic performances of TPBP in
heterogeneous reaction, the oxidative homocoupling of amines to
imines were carried out in detail. The temperature factors were
first screened to attain the most suitable reaction condition. As
shown in Fig. 4a, under the same reaction condition, at room tem-
perature, only about 7.8% yield of the imine dimer was obtained
after 16 h, and with the increase of the temperature, the conver-
sion of benzyl amine augmented and conversion reached 45% at
60 °C, until closed to 100% at 100 °C. To confirm that the O2 is
3.2. Catalytic studies
Phenazine derivatives with inherent electron-donating capabil-
ity are easy to turn into phenazine radical cations which can be
used to catalyze lots of oxidative reactions, such as oxidative cou-
pling of benzyl amine to imine [37] and esterification of aldehydes

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J. Lin et al. / Journal of Catalysis 385 (2020) 338–344
Fig. 4. (a) Conversion of benzyl amine oxidative coupling reaction at different temperatures. Reaction conditions: benzyl amine (0.6 mL), TPBP catalyst (20 mg), NOBF4
(2 mg), O2 (1 bar), 16 h. (b) Time-conversion plot of the oxidative coupling of benzyl amine catalyzed with TPBP. Reaction conditions: benzyl amine (0.6 mL), TPBP catalyst
(20 mg), NOBF4(2 mg), 100 °C, O2 (1 bar).
essential for the reaction, a control experiment was conducted
under inert atmosphere and only found trace imine dimer after
the reaction. Another control experiment was performed in the
air, and the catalyst could only catalyze the reaction with a conver-
sion of 31.4% after 16 h. In contrast, the reaction conversion
increases to more than 95% under 1 bar O2 at 100 °C under the
same condition. Thus, it can be concluded that O2 is indispensable
in this oxidative coupling reaction. Fig. 4b showed the effect of
reaction time of benzyl amine oxidation over TPBP radical cations
catalyst. It is clear that the conversion of benzyl amine gradually
increased with reaction time and the plot show a typical zero-
order kinetic reaction character with a rate constant k of 6.57.
The TOF (TOF = mmol of amine converted per gram of catalyst
per hour) of the reaction was calculated to be 16.9[39]. It should
be noted that the catalytic performance of TPBP is comparable to
other reported heterogeneous catalysts including noble-metal
based catalyst and photocatalyst in this oxidative coupling reaction
(Table S1) [11,39–45].
Fig. 5. Recyclability of TPBP in benzyl amine oxidative coupling reaction. Reaction
To study the general applicability of the TPBP radical catalysts,
several substituted benzyl amines with either electron-donating or
electron-withdrawing group were also examined, as shown in the
Table 1. Under the current reaction condition, all the above substi-
tuted benzyl amines were easily oxidized by TPBP to the corre-
sponding products in good yields and excellent selectivity.
conditions: benzyl amine (0.6 mL), TPBP catalyst (20 mg), NOBF4 (2 mg) 100 °C, O2
(1 bar), 16 h.
Besides, these catalytic performance are comparable with the
homogenous catalyst PhRCs reported by Esteban Mejía [37]. On
Table 1
Oxidative coupling of various amines by using TPBP radical cations.a
Entry
Substrate
Product
Conversionb (%)
99
Selectivityb (%)
97
1
2
3
98
98
98
96
4
99
97
5
6
7
8
98
97
99
99
98
97
98
96
a
Reaction conditions: 0.6 mL amine, 20 mg TPBP, 2 mg NOBF4, 0.4 mL CH3CN and an oxygen atmosphere at 100 °C.
b
Conversion was determined by GC and verified by 1H NMR spectroscopy and GCMS.

J. Lin et al. / Journal of Catalysis 385 (2020) 338–344
343
Fig. 6. EPR spectra (a) and UV-vis spectra (b) of TPBP (black line), TPBP after the oxidation with NOBF4 (red line) and subsequent addition of benzyl amine (blue line).
Fig. 7. Propose mechanism for the amine oxidative coupling reaction in the presence of TPBP.
the other hand, as shown in Fig. 5, TPBP demonstrated good recy-
clability in the oxidative coupling reaction. After reaction, the
weight of the catalyst merely changed and the catalytic activity
kept closely for at least six recycle experiments. Similar to other
polymeric solid catalysts, the TPBP catalysts could be reused after
simple filtration. During the recycled experiments, TPBP needs to
be treated with NOBF4 again. Hence, it can be concluded that the
as-prepared TPBP radical cation-based catalyst possessed excellent
stability and recyclability.
3.3. Mechanism investigation
TPBP radical cations are obtained by oxidizing TPBP polymers
with NOBF4. As shown in Scheme 2, the phenazine group contained
16-p electrons was oxidized to the corresponding 15-p electron
radical cations. During this process, N2 was bubbled to release
NO, and the remaining BF-4 was used as the counterion of the
obtained TPBP radical cations.
To get more insight into the benzyl amine oxidation catalyzed
by TPBP radical cations, EPR and UV-vis spectroscopy were used
to explore the mechanism. As shown in Fig. 6a, the pristine TPBP
sample exhibited very low EPR signal. However, after oxidation
by NOBF4, a single-peak with g = 2.0026 appeared, which clearly
support the formation of TPBP radical cations [46,47]. The integra-
tion of the EPR signal is proportional to the yield of radical cations
[48,49], which demonstrated that NOBF4 plays an essential role in
the formation of TPBP radical cations. UV-Vis diffuse-reflectance
spectroscopy measurement was performed to further illustrate
the generation of TPBP radical cations during the catalytic reaction.
As depicted in Figure S2 and Fig. 6b, after adding oxidant NOBF4,
the catalyst color changed from brown to green immediately. Cor-
respondingly, in UV–vis spectroscopy, a new broad band appeared
around 600–1200 nm and two new distinct shoulder peaks are also
emerged around 685 and 755 nm, which is probably due to the for-
mation of TPBP radical cations. After 1 equiv benzyl amine was
Scheme 2. Oxidation of the TPBP with NOBF4 to form the TPBP radical cations.

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J. Lin et al. / Journal of Catalysis 385 (2020) 338–344
added to the treated catalyst, its color changed back to dark brown
and the characteristic absorption band was almost completely
recovery. This phenomenon was mainly attributed to the decrease
of radical cations and subsequently the recovery of its electronic
state via single electron transfer from benzyl amine to TPBP radical
cations. This result is also consistent with its EPR measurement.
A possible reaction mechanism of amine oxidation catalyzed by
TPBP radical cations is then proposed based on the presented UV-
vis spectroscopy and EPR measurements (Fig. 7 and Figure S3). At
beginning, molecular oxygen was used to oxidize TPBP to form
TPBP radical cations and superoxide radical anion (O2Åꢀ). However,
under the high temperature (100 °C) and low pressure (1 atm), it is
very difficult to obtain the TPBP radical cations adequately. There-
fore, NOBF4 was used as a pre-oxidant agent in assisting the rapid
production of TPBP radical cations. Without the pre-oxidant, the
overall catalytic conversion of the corresponding imines was only
22%. In contrast, without catalyst, in the case of NOBF4, the reaction
conversion was about 30.8%. After reacting with benzyl amine, the
TPBP radical cations restore back to the non-radical TPBP and the
benzyl amine radical cation (1) is generated [44]. Then, the super-
oxide radical abstracts protons from the amine radical cations (1)
to produce hydrogen peroxide and benzyl imine intermediate (2)
as claimed by Loh [50]. The produced hydrogen peroxide can also
catalyze the benzyl amine substrate to form benzyl imine interme-
diate (2) [51]. Finally, the above benzyl imine collided with another
free benzyl amine molecule to form the aminal intermediate (3),
which generally prone to decompose to the target imine product
and ammonia.
References
[1] M.M. Abdelnaby, N.A.A. Qasem, B.A. Al-Maythalony, K.E. Cordova, O.C.S. Al
Hamouz, ACS Sustainable Chem. Eng. 7 (2019) 13941–13948.
[2] N. Song, T. Wang, H. Yao, T. Ma, K. Shi, Y. Tian, Y. Zou, S. Zhu, Y. Zhang, S. Guan,
Polym. Chem. 10 (2019) 4611–4620.
[3] G. Chang, Z. Shang, T. Yu, L. Yang, J. Mater. Chem. A 4 (2016) 2517–2523.
[4] W. Li, A. Zhang, H. Gao, M. Chen, A. Liu, H. Bai, L. Li, Chem. Commun. 52 (2016)
2780–2783.
[5] H. Lim, M.C. Cha, J.Y. Chang, Macromol. Chem. Phys. 213 (2012) 1385–1390.
[6] Y. Yuan, F. Sun, L. Li, P. Cui, G. Zhu, Nat. Commun. 5 (2014) 4260.
[7] L. Zou, J. Yuan, Y. Yuan, J. Gu, G. Li, L. Zhang, Y. Liu, CrystEngComm 21 (2019)
3289–3294.
[8] H. Li, Y. Yang, C. He, L. Zeng, C. Duan, ACS Catal. 9 (2019) 422–430.
[9] C. Su, X. Duan, J. Miao, Y. Zhong, W. Zhou, S. Wang, Z. Shao, ACS Catal. 7 (2017)
388–397.
[10] V.M. Suresh, S. Bonakala, H.S. Atreya, S. Balasubramanian, T.K. Maji, ACS Appl.
Mater. Interfaces 6 (2014) 4630–4637.
[11] B. Chen, L. Wang, W. Dai, S. Shang, Y. Lv, S. Gao, ACS Catal. 5 (2015) 2788–2794.
[12] B. Ye, R. Jiang, Z. Yu, Y. Hou, J. Huang, B. Zhang, Y. Huang, Y. Zhang, R. Zhang, J.
Catal. 380 (2019) 307–317.
[13] Y. Han, H. Xu, Y. Su, Z.-L. Xu, K. Wang, W. Wang, J. Catal. 370 (2019) 70–78.
[14] Q. Zhang, H. Dong, W. Hu, J. Mater. Chem. C 6 (2018) 10672–10686.
[15] W. Zhang, X. Sun, T. Huang, X. Pan, P. Sun, J. Li, H. Zhang, X. Lu, Q. Fan, W.
Huang, Chem. Commun. 55 (2019) 9487–9490.
[16] T.L. Church, A.B. Jasso-Salcedo, F. Björnerbäck, N. Hedin, Sci. China. Chem 60
(2017) 1033–1055.
[17] Q. Li, S. Razzaque, S. Jin, B. Tan, Sci. China. Chem 60 (2017) 1056–1066.
[18] N. Chaoui, M. Trunk, R. Dawson, J. Schmidt, A. Thomas, Chem. Soc. Rev. 46
(2017) 3302–3321.
[19] X. Yang, L. Tan, L. Xia, C.D. Wood, B. Tan, Macromol. Rapid Commun. 36 (2015)
1553–1558.
[20] Q. Yu, D. Tan, T. Huang, T. Zhao, L. Li, Green Chem. 20 (2018) 4746–4751.
[21] L. Chen, Y. Yang, Z. Guo, D. Jiang, Adv Mater 23 (2011) 3149–3154.
[22] E. Preis, N. Schindler, S. Adrian, U. Scherf, ACS Macro Lett. 4 (2015) 1268–1272.
[23] S. Fischer, A. Schimanowitz, R. Dawson, I. Senkovska, S. Kaskel, A. Thomas, J.
Mater. Chem. A 2 (2014) (1829) 11825–11831.
[24] K. Zhang, B. Tieke, F. Vilela, P.J. Skabara, Macromol. Rapid Commun. 32 (2011)
825–830.
4. Conclusions
[25] Z. Xiao, X. Huang, K. Zhao, Q. Song, R. Guo, X. Zhang, S. Zhou, D. Kong, M.
Wagner, K. Mullen, L. Zhi, Small 15 (2019) e1900244.
[26] Y. Liao, J. Weber, C.F. Faul, Chem. Commun. 50 (2014) 8002–8005.
[27] J. Schmidt, M. Werner, A. Thomas, Macromolecules 42 (2009) 4426–4429.
[28] A. Laybourn, R. Dawson, R. Clowes, J.A. Iggo, A.I. Cooper, Y.Z. Khimyak, D.J.
Adams, Polym. Chem. 3 (2012) 533–537.
[29] N. Guttenberger, W. Blankenfeldt, R. Breinbauer, Bioorg. Med. Chem. 25 (2017)
6149–6166.
[30] Y. Lian, J.R. Hummel, R.G. Bergman, J.A. Ellman, J. Am. Chem. Soc. 135 (2013)
12548–12551.
[31] J.K. Laha, K.S.S. Tummalapalli, A. Gupta, Eur. J. Org. Chem. 2013 (2013) 8330–
8335.
[32] L. Yang, X. Li, J. Yang, Y. Qu, J. Hua, ACS Appl. Mater. Interfaces 5 (2013) 1317–
1326.
[33] S. Chun, Y.K. Chung, Org. Lett. 19 (2017) 3787–3790.
[34] G. Kwon, S. Lee, J. Hwang, H.-S. Shim, B. Lee, M.H. Lee, Y. Ko, S.-K. Jung, K. Ku, J.
Hong, K. Kang, Joule 2 (2018) 1771–1782.
[35] J.C. Theriot, C.-H. Lim, H. Yang, M.D. Ryan, C.B. Musgrave, G.M. Miyake, Science
352 (2016) 1082–1086.
In summary, we have successfully constructed the first microp-
orous polymer built on phenazine using the Buchwald-Hartwig
coupling reaction. The strategy mentioned here will be helpful
for the diversity of phenazine related compounds, especially for
the field of metal-organic frameworks (MOFs), covalent-organic
frameworks (COFs) and other porous materials. This polymer pos-
sesses highly reversible redox properties due to the presence of
phenazine groups in its framework and it can produce TPBP radical
cations by one-electron oxidation. The EPR and UV-visible spec-
troscopy further directly verify the existence of TPBP radical
cations in the oxidized framework. Interestingly, the TPBP based
heterogeneous catalyst demonstrates excellent catalytic perfor-
mance for the benzyl amine oxidative coupling reaction. Moreover,
it can be reused for at least six times without obvious deactivation.
It is to be expected that this work will stimulate extensive research
on phenazine related porous materials due to their fascinating
electronic properties.
[36] G. Dai, Y. He, Z. Niu, P. He, C. Zhang, Y. Zhao, X. Zhang, H. Zhou, Angew. Chem.
Int. Ed. 58 (2019) 9902–9906.
[37] R. Brisar, F. Unglaube, D. Hollmann, H. Jiao, E. Mejia, J. Org. Chem. 83 (2018)
13481–13490.
[38] A. Ranganathan, B.C. Heisen, I. Dix, F. Meyer, Chem. Commun. (2007) 3637–
3639.
[39] V.R. Battula, H. Singh, S. Kumar, I. Bala, S.K. Pal, K. Kailasam, ACS Catal. 8 (2018)
6751–6759.
Declaration of Competing Interest
[40] W. Deng, J. Chen, J. Kang, Q. Zhang, Y. Wang, Chem. Commun. 52 (2016) 6805–
6808.
[41] T.K. Kapuge, W.R.K. Thalgaspitiya, D. Rathnayake, J. He, P. Kerns, S.L. Suib, Appl.
Catal. B: Environ. 268 (2019) 118386.
[42] X.H. Li, M. Antonietti, Angew. Chem. Int. Ed. 52 (2013) 4572–4576.
[43] X. Cui, W. Li, K. Junge, Z. Fei, M. Beller, P.J. Dyson, Angew. Chem. Int. Ed. 59
(2020) 2–9.
[44] C. Xu, H. Liu, D. Li, J.H. Su, H.L. Jiang, Chem. Sci. 9 (2018) 3152–3158.
[45] Z. Liu, Q. Su, P. Ju, X. Li, G. Li, Q. Wu, B. Yang, Chem. Commun. 56 (2020) 766–
769.
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
Acknowledgements
This work was supported by the financial support from the
National Natural Science Foundation of China (Grant No.
51703031).
[46] T. Li, G. Tan, D. Shao, J. Li, Z. Zhang, Y. Song, Y. Sui, S. Chen, Y. Fang, X. Wang, J.
Am. Chem. Soc. 138 (2016) 10092–10095.
[47] J.L. Grant, V.J. Kramer, R. Ding, L.D. Kispert, J. Am. Chem. Soc. 110 (1988) 2151–
2157.
[48] B. Lu, Y. Chen, P. Li, B. Wang, K. Mullen, M. Yin, Nat. Commun. 10 (2019) 767.
[49] Y. Jiao, K. Liu, G. Wang, Y. Wang, X. Zhang, Chem. Sci. 6 (2015) 3975–3980.
[50] C. Su, M. Acik, K. Takai, J. Lu, S.J. Hao, Y. Zheng, P. Wu, Q. Bao, T. Enoki, Y.J.
Chabal, K.P. Loh, Nat. Commun. 3 (2012) 1298.
Appendix A. Supplementary material
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.jcat.2020.03.031.
[51] J. Yang, C.Y. Mou, Appl. Catal. B: Environ. 231 (2018) 283–291.