Zinc porphyrin-based electron donor–acceptor-conjugated microporous polymer for the efficient photocatalytic oxidative coupling of amines under visible light

Article abstract of DOI:10.1016/j.apcata.2019.117352

The application of porous organic polymers is an emerging area of heterogeneous photocatalytic organic synthesis. In principle, the transfer of energy and electrons is significant to improve the photocatalytic efficiency. To obtain an efficient energy- an

Full text of DOI:10.1016/j.apcata.2019.117352

Journal Pre-proof
Zinc porphyrin-based electron donor–acceptor-conjugated microporous
polymer for the efficient photocatalytic oxidative coupling of amines under
visible light
Xiao-Xuan Guo (Conceptualization)
(
(
Investigation)<ce:contributor-role>Writing-Original Draft), Jun Jiang
Conceptualization) (Methodology), Qi Han (Software) (Data
curation), Xiao-Hui Liu (Formal analysis) (Visualization), Xian-Tai
Zhou (Supervision)<ce:contributor-role>Writing-Review and Editing)
(Funding acquisition), Hong-Bing Ji<ce:contributor-role>Project
adminstration) (Funding acquisition)
PII:
S0926-860X(19)30507-1
DOI:
https://doi.org/10.1016/j.apcata.2019.117352
APCATA 117352
Reference:
To appear in:
Applied Catalysis A, General
Received Date:
Revised Date:
Accepted Date:
13 September 2019
13 November 2019
15 November 2019
Please cite this article as: Guo X-Xuan, Jiang J, Han Q, Liu X-Hui, Zhou X-Tai, Ji H-Bing, Zinc
porphyrin-based electron donor–acceptor-conjugated microporous polymer for the efficient
photocatalytic oxidative coupling of amines under visible light, Applied Catalysis A, General
(2019), doi: https://doi.org/10.1016/j.apcata.2019.117352

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Zinc porphyrin-based electron donor–acceptor-conjugated
microporous polymer for the efficient photocatalytic oxidative
coupling of amines under visible light
a
c
a
a
a
Xiao-Xuan Guo , Jun Jiang , Qi Han , Xiao-Hui Liu , Xian-Tai Zhou* , Hong-Bing
Ji*b,d
aSchool of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, China
bFine Chemical Industry Research Institute, the Key Laboratory of Low-carbon Chemistry & Energy
Conservation of Guangdong Province, School of Chemistry, Sun Yat-sen University, Guangzhou
5
10275, China
cGuangdong Industrial Analysis and Testing Center, Guangdong Academy of Sciences, Guangzhou
5
10650，China
dSchool of Chemical Engineering, Guangdong University of Petrochemical Technology, Maoming
5
25000, P.R.China
*
Corresponding author. Tel.: +86-20-84113658; fax: +86-20-84113654.
E-mail: zhouxtai@mail.sysu.edu.cn (X. T. Zhou); jihb@mail.sysu.edu.cn (H. B. Ji)
Graphical Abstract
Zinc porphyrin-based polymer (ZnTEPP-PBI) has wide optical absorption range. By using ZnTEPP-
PBI as the photocatalyst, the oxidative coupling of amines to imines was efficiently realized under
visible light.

Abstract:
The application of porous organic polymers is an emerging area of heterogeneous
photocatalytic organic synthesis. In principle, the transfer of energy and electrons is
significant to improve the photocatalytic efficiency. To obtain an efficient energy- and
electron-transfer catalytic system, a porous organic polymer exhibiting both electron
donor and electron acceptor properties (ZnTEPP-PBI) was synthesized using zinc
porphyrin (ZnTEPP) and perylene bisimide (PBI) monomers as the structural units.
Compared with that of ZnTEPP, the optical absorption range of the ZnTEPP-PBI
polymer was expanded due to the introduction of the PBI monomer. By using ZnTEPP-
PBI as the photocatalyst, the oxidative coupling of amines to imines was efficiently
realized under visible light. In addition, a plausible pathway for the mechanism for the
enhanced energy and electron transfer was proposed.
Keywords: Porphyrin; Perylene bisimide; Visible light; Amine; Oxidative coupling
1. Introduction
Photocatalysis can not only use solar energy as the light source but also prevent
the use of strong oxidants, deleterious reducing agents, and toxic substances [1,2].
Photocatalysis considerably meets the societal requirements in terms of the energy and
environment [3]. By optimizing a photocatalytic system, the selective synthesis of
target products can be achieved, affording a green, energy-efficient method for organic
synthesis [4–6]. Metalloporphyrin exhibits good light-trapping properties, which can

be used as a highly efficient homogeneous photocatalyst [7]. However, porphyrin is
prone to oxidation, degradation, or dimerization, leading to deactivation, and its
separation and recovery are difficult. Hence, from the practical viewpoint, the
preparation of heterogeneous catalysts using porphyrin exhibits more advantages than
homogeneous catalysts [8].
Currently, a majority of studies have prepared composite materials from metal
porphyrins to achieve heterogeneous catalysis. Typical preparation methods include
physical adsorption for the loading of a metalloporphyrins onto molecular sieves or
resins or the combination of porphyrin molecules with carriers via electrostatic forces,
coordination bonds, and covalent bonds [9–11]. However, these methods exhibit some
limitations, including low immobilization ability, poor catalytic activity, and poor
selectivity. Compared to the use of conventional methods, porous organic polymers
prepared using metalloporphyrins as the bonding units can not only enhance their
catalytic activity via the increased density of their active centers but also render a
“
limited effect” on substrates due to their porous structure [12–14]. Notably, the porous
inner surface can considerably shorten the transmission distance of the photogenerated
electrons and holes and improve the utilization of light [15].
The porphyrin ring is an N-containing conjugated system, which can be used as
an electron donor [16], and porphyrin is also considered to be a good photosensitizer
1
for the generation of O
2
[17]. Perylene bisimide exhibits high thermal stability,
photochemical stability, and high electrophilicity. To obtain an efficient photocatalytic
system under visible light, catalysts that exhibiting both electron donor and electron

acceptor properties could be favorable for the transfer of energy and electrons.
With this idea in mind, the donor–acceptor (D–A) conjugated polymer ZnTEPP-
PBI was synthesized by the Sonogashira coupling using zinc porphyrin and perylene
bisimide as the structural units in this study. By the introduction of electron donors and
electron acceptors into conjugated polymer chains, the transfer of charge in conjugated
polymer molecules can be effectively controlled. The optical properties of the ZnTEPP
monomer, PBI, and ZnTEPP-PBI polymer were compared by UV–Vis–NIR absorption
spectroscopy, steady-state fluorescence spectroscopy, and theoretical calculations. The
results revealed that ZnTEPP-PBI can not only improve the utilization of light and
recyclability but also exhibit high catalytic activity and wide substrate scope for the
visible-light photocatalytic oxidative coupling of amines. The catalytic system
1
and O
•, forming the “trinity” photocatalytic
comprises abundant active species O
2
2
process of energy transfer, electron transfer, and hole oxidation.
2. Results and discussion
2
.1. Photocatalyst synthesis and characterization
In this study, ZnTEPP and PBI were synthesized according to previously reported
studies [18,19]. The ZnTEPP and PBI structures were characterized by NMR and
MALDI-TOF spectroscopy, respectively (Figure S1–S7). The D–A polymer ZnTEPP-
PBI was successfully synthesized by the Sonogashira reaction using ZnTEPP and PBI
monomers as the construction units (Scheme 1).
(
Scheme 1)
ZnTEPP-PBI was obtained as a dark-purple powder, which was insoluble in a

majority of solvents. The FTIR spectra of PBI and ZnTEPP-PBI revealed a stretching

1
vibration peak of -CH at 2960 cm (Figure 1A). Two characteristic absorption peaks
3

1
1
corresponding to R-C≡CH were observed at 3293 cm and 2196 cm in the FTIR
spectrum of ZnTEPP [18]; however, these two peaks disappeared in the FTIR spectrum
of ZnTEPP-PBI, indicating that the ZnTEPP monomer is successfully polymerized by
1
3
the PBI monomer in the Sonogashira reaction. Figure S8 shows the solid-state C NMR
spectrum. Peaks observed at 20–165 ppm corresponded to the carbon atoms of the
porphyrin ring, benzene ring, and PBI [19,20]. In addition, the XPS spectrum of
ZnTEPP-PBI revealed peaks corresponding to C 1s, N 1s, O 1s, and Zn 2p (Figure S9-
1
2). The binding energy of Zn 2p3/2 was reduced, indicating that the electrons in pyrrole
N are transferred to the Zn empty orbitals, and the zinc metal center coordinates with
porphyrin ligands [21] (Figure 1B). In the XPS spectrum of O 1s, the binding energies
of 531.5 eV and 533.2 eV respectively belong to O atoms in the structure of C=O and
C-O in PBI (Figure S10). In N 1s XPS spectra, the binding energy appears at 398.3 eV
and 400.4 eV (Figure S11), which belong to acylamide N atom in PBI and pyrrole N
atom in porphyrin unit.
(
Figure 1)
Subsequently, the SEM image clearly revealed that ZnTEPP-PBI mainly
comprises microspheres with various sizes ranging from 0.5 to 2 μm in diameter, and
the TEM image provides direct evidence for the porosity of ZnTEPP-PBI (Figure S13).
This porous structure is favorable for mass transfer [22]. Nitrogen gas adsorption
measurements were conducted on pretreated ZnTEPP-PBI at 77 K to investigate the

permanent porosity. Typical type I isotherms were observed in the N
desorption isotherm. At a low relative pressure (P/P < 0.01), the adsorption isotherm
revealed a sharp increase in the nitrogen uptake, corresponding to the presence of
2
adsorption–
0
2
1
micropores. The Brunauer–Emmett–Teller surface area (SBET) was 465 m g with a
3
1
total pore volume (Vtotal) of 0.20 cm g , indicative of a high surface area and large pore
volume (Figure S14). Furthermore, ZnTEPP-PBI exhibited several micropores with
diameters of 0.9–1.9 nm according to the nonlocal density functional theory method
(
Figure S15).
The light-harvesting capability of the samples was investigated by ultraviolet-visible-
near-infrared diffuse reflectance spectroscopy (UV-Vis-NIR DRS) and
photoluminescence (PL) spectroscopy. The UV absorption peak of ZnTEPP-PBI was
similar to that of ZnTEPP, but the absorption range of ZnTEPP-PBI was expanded due
to the introduction of PBI (Figure 2A). Moreover, the UV-Vis-NIR DRS spectrum of
ZnTEPP-PBI revealed a significant red-shift compared with that of the ZnTEPP
monomer. This shift was related to the extension of the -conjugated structure, resulting
in exceptional light-harvesting capability in the long-wavelength visible region. The
bandgap (Eg) of samples was determined from the UV-diffuse reflectance map. The
positive slopes of Mott-Schottky plots for ZnTEPP-PBI are consistent with the behavior
of a typical n-type semiconductor (Figure S16). According to the UV-Vis-NIR DRS
spectrum, the bandgap of ZnTEPP-PBI was 1.83 eV (Figure S17).
The steady-state fluorescence emission spectra of the ZnTEPP monomer, PBI
monomer, and ZnTEPP-PBI polymer were recorded. At an excitation wavelength of

4
70 nm, PBI exhibited a strong fluorescence emission peak at 691 nm (Figure 2B).
ZnTEPP exhibited two weak fluorescence emission peaks at 692 nm and 745 nm,
respectively. However, fluorescence emission peaks were not observed for ZnTEPP-
PBI, which was related to the photoinduced electron-transfer process in ZnTEPPP-PBI.
By the photoexcitation of ZnTEPP-PBI, the transfer of electrons occurred between the
excited-state electron donor and electron acceptor, and charge-separation products
+

ZnTEPP -PBI were generated, leading to fluorescence quenching [23].
(Figure 2)
Cyclic voltammetry revealed that there was no oxidation peak in PBI, and the
initial oxidation peak of ZnTEPP-PBI was similar to that of ZnTEPP monomer,
indicative of the possibly high oxidizing nature of both ZnTEPP-PBI and ZnTEPP
(Figures S18). Therefore, the D-A character of the ZnTEPP-PBI polymer is reflected in
the ability to separate the electrons and holes produced more effectively by light
excitation. The highest occupied molecular orbital (HOMO) of ZnTEPP-PBI is +0.72
+
V vs Ag/Ag (Figures S18 and S19). The bandgap is the energy difference between the
HOMO and the lowest unoccupied molecular orbital (LUMO). Hence, the LUMO is

1.11 V (Figure S20).
2
.2. Catalytic performance
By using benzylamine as the model substrate, the selective oxidation of amine to
imine catalyzed by ZnTEPP-PBI under the illumination of a white-light-emitting diode
LED) lamp and molecular oxygen was examined. In the control experiment of the
photocatalyst, the product was not obtained under the white-LED illumination for 4 h
(

(
entry 1, Table 1). By only using ZnTEPP as the photocatalyst, imines were obtained in
0% yield (entry 2, Table 1). Surprisingly, when heterogeneous ZnTEPP-PBI was used
7
as the photocatalyst, imine was obtained in a 99% yield (entry 3, Table 1). This
enhancement was related to the intrinsic properties of the photocatalyst, which exhibits
properties of both an electron donor and an electron acceptor after the introduction of
PBI. Hence, the transfer of intramolecular electrons occurs easily, leading to the better
photoelectric properties of the catalyst than the ZnTEPP monomers [24]. Moreover, a
large number of micropores is favorable for the exposure of an increased number of
active sites to active molecular oxygen [25]. Clearly, a reaction did not occur when the
oxidative coupling of the amine reaction was conducted in the dark or under argon
(entries 4 and 5, Table 1, respectively). The apparent quantum yields of N-benzylidene
benzylamine at 420, 450, 485, 535, 595, 630 nm were tested. As shown in Figure S21,
ZnTEPP-PBI has a wide range of light response. Compared with typical solid
photocatalysts such as TiO
benzylamine has a high apparent quantum yield with ZnTEPP-PBI at all wavelengths.
Table 1)
2
, C
N
3 4
, BiMoO , the target product N-benzylidene
6
(
To evaluate the scope of the photocatalytic system, the oxidative coupling of
various primary amines under visible light was investigated by using the ZnTEPP-PBI
catalyst (Table 2).
A majority of the amines were smoothly converted to the corresponding imines in
high yields (Table 2). The efficiency for the oxidative coupling in this catalytic system
was apparently not extremely dependent on the electronic property of the para

substituents of the substrate (entries 1–4, Table 2). However, the efficiency is quite
different in terms of the electronic property of the ortho substituents of the substrate
(entries 5–7, Table 2). Compared to the electron-withdrawing groups, electron-donating
groups at the ortho position were apparently more conducive for the oxidative coupling
of amines. The efficiency was improved by prolonging reaction time for the substrate
bearing electron-withdrawing groups at the ortho position (entry 6, Table 2).
In addition, the catalytic system exhibited high activity for the oxidative coupling
of heterocyclic amines (entry 8, Table 2). The steric hindrance of substrates was clearly
observed in this photocatalytic system. For example, corresponding imines were
obtained in only 53% yield when 1-phenylethanamine was used as the substrate.
Prolonged the reaction time to 9 h, the yield of imines could be enhanced to 85% (entry
1
0, Table 2).
Table 2)
(
2
.3 Catalyst reuse and stability
The stability of the ZnTEPP-PBI catalyst was monitored by multiple sequential
oxidative coupling reactions of benzylamine under visible light. The catalyst was
recovered by centrifugation, filtration, washed with acetonitrile, and dried before using
it in subsequent runs. Figure 3 shows the results obtained.
(
Figure 3)
The results revealed that the photocatalytic activity can be maintained up to the fifth
cycle when it was used for the selective oxidation of benzylamine (Figure 3). At the
same time, according to the FTIR spectrum of fresh ZnTEPP-PBI and its use after five

recycles (Figure S22), the ZnTEPP-PBI structure did not change significantly, and the
zinc active center was still fixed in a strong framework. The results clearly revealed that
the photocatalyst is active for the oxidative coupling of benzylamine and can be reused
without significant decrease in the catalytic activity and with almost similar selectivity.
2
.4 Mechanism consideration
Further experiments were carried out to understand the mechanism for the ZnTEPP-
PBI-photocatalyzed oxidative coupling of benzylamine. Figure 4 shows the profile for
the oxidative coupling of benzylamine catalyzed by ZnTEPP-PBI under visible light.
The conversion of benzylamine slowly increased within the first hour. Then, the
reaction rate rapidly increased. Clearly, an induction period in the photocatalytic
oxidation system was present. The oxidation of benzylamine revealed features of a
radical reaction.
(
Figure 4)
Various inhibitors to the oxidative coupling were used; thus, the active species for
the reaction system can be indirectly investigated (Table 3). With the addition of KI as
a hole inhibitor[4], the yield of the imine decreased to 6% (entry 1, Table 3), possibly
due to the reduction of the photogenerated holes, and benzylamine cannot be further
oxidized to produce benzylamine cation free radicals. Next, with the addition of β-
1
and O
•, the yields of imine
carotene [26] and benzoquinone [27] as inhibitors for O
2
2
sharply decreased to only 11% and 22%, respectively (entries 2 and 3, Table 3),
1
and O
•. In addition,
indicating that the main active species in the reaction system is O
2
2
+
the LUMO of ZnTEPP-PBI was 1.11 V vs Ag/Ag , which can also be considered as

•

theoretical evidence for the activation of molecular oxygen into O
2
by ZnTEPP-PBI
/O •

= 0.61 V vs Ag/Ag ) [28]. With the addition of isopropanol as an inhibitor
+
(
O
2
2
for OH· [4], the yield of the imine was only 16%, indicating that OH· is also an active
oxygen species in the ZnTEPP-PBI-photocatalyzed oxidative coupling of benzylamine
(
entry 4, Table 3).
Table 3)
Subsequently, electron spin resonance (ESR) was employed for the detection of
(
the reactive oxygen species in the photocatalytic system of ZnTEPP-PBI. 2,2,6,6-
Tetramethylpiperidine (TEMP) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) were
1
•
1
used as the O
2
and O
2
capture agents, respectively [29]. An O signal was not
2
observed when the reaction was carried out in the dark (Figure 5A). By the exposure of
the solution with the ZnTEPP-PBI catalyst to visible light for 3 min, a set of strong
1
:1:1 triple peak signal (♠) was observed. These triple peaks corresponded to the signal
1
of TEMPO, which was the product from the reaction of O
2
with TEMP [30,31]. Hence,
1
the presence of O
2
in the system is verified. However, with the addition of benzylamine
to the ZnTEPP-PBI photocatalytic system and exposure to visible light for 3 min, the
1
intensity of the triple peak sharply decreased, indicative of the reaction of O
2
with
benzylamine to obtain imine intermediates.
•

DMPO was used as the capture agent for O
2
(Figure 5B). When the reaction was
conducted in the dark, a signal was not observed. By the irradiation of the solution with
the ZnTEPP-PBI mixture under visible light for 3 min, a group of weak quadruple peaks
•

was observed, corresponding to the adduct of O
2
and DMPO [32]. This result

•

indicated the presence of O
2
in the system. Subsequently, benzylamine was added to
the photocatalytic system and irradiated under visible light for 3 min, and the signal of
the quadruple peak signal (♣) was significantly enhanced. From the observed
phenomenon, photogenerated holes can easily oxidize benzylamine, and the free radical
cation of benzylamine is obtained at the same time. This reduction was conducive to
the inhibition of the recombination of photogenic hole and photogenic electrons.
Accordingly, photogenic electrons can efficiently transfer an increased amount of O to
2
generate O •
.
2
(
Figure 5)
According to the above results obtained from ESR and inhibition experiments, as
well as previous studies [5,33,34], the mechanism for the photocatalytic oxidation of
benzylamine by ZnTEPP-PBI was proposed (Scheme 2).
Under light irradiation, ZnTEPP-PBI is stimulated by the light absorption energy,
and the single excited state containing electron–hole pairs is generated. Benzylamine is
oxidized by photogenic holes, affording benzylamine free radical cations, and
photogenic electrons are transferred to O
2
to generate O
•. In addition, the triple excited
2
states can be obtained by the intersystem crossing of the singlet excited states, and O
2
1
•
can be activated by the triplet excited states via energy transfer to obtain O
2
. O
2
reacts
1
with benzylamine free radical cations, and O
2
reacts with benzylamine. The two
will form OH·, which
reactions produce H
2
O
2
and imide intermediates. Then, H
2
O
2
reacts with benzylamine to form an imine intermediate. The imine intermediate further
reacts with the benzylamine, affording the target product imine.

(
Scheme 2)
3
. Conclusion
In summary, a zinc-porphyrin-based porous organic polymer bearing an electron
donor and an electron acceptor (ZnTEPP-PBI) was successfully synthesized. Compared
with that of ZnTEPP, the optical absorption range of the ZnTEPP-PBI polymer was
expanded due to the introduction of the PBI monomer. The heterogeneous photocatalyst
was found to be efficient for the oxidative homocoupling of amines to imines under
visible light. Various amines including primary and secondary amines were smoothly
converted to the corresponding imines in good yield. The catalyst was easily recycled
and reused for at least five runs without any clear decrease in the catalytic performance.
From emission quenching experiments and ESR tests, molecular oxygen is activated
1
) and superoxide radical anion (O
•) via energy transfer and
into singlet oxygen ( O
2
2
electron transfer, respectively. Particularly, efficient electron transfer occurring between
the electron donor and electron acceptor could enhance the photocatalytic activity.
Author Contribution Statement
Xiao-Xuan Guo: Conceptualization, Investigation, Writing-Original Draft
Jun Jiang: Conceptualization, Methodology
Qi Han: Software, Data curation
Xiao-Hui Liu: Formal analysis, Visualization
Xian-Tai Zhou: Supervision, Writing-Review & Editing, Funding acquisition
Hong-Bing Ji: Project adminstration, Funding acquisition

Acknowledgments
This study was supported by the National Key Research and Development Program
of China (2016YFA0602900), the National Natural Science Foundation of China (No.
2
1425627, 21878344, 21576302 and 21938001), the National Natural Science
Foundation of China-SINOPEC Joint Fund (No. U1663220), Guangdong Provincial
Key R&D Programme(2019B110206002) and the Local Innovative and Research
Teams Project of Guangdong Pearl River Talents Program (2017BT01C102).

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Captions
Table 1. Photocatalytic oxidative coupling of benzylamine
Table 2. Photocatalytic oxidative coupling of amines into imines by ZnTEPP-PBI
Table 3. Control experiments for the photocatalytic oxidative coupling of benzylamine
Figure 1. (A) FTIR spectra of ZnTEPP, PBI, and ZnTEPP-PBI; (B) Zn 2p XPS spectra
of ZnTEPP-PBI.
Figure 2. (A) UV-Vis-NIR DRS spectra of ZnTEPP, PBI, and ZnTEPP-PBI; (B)
Photoluminescence spectra with an excitation wavelength of 470 nm at 298 K for
ZnTEPP, PBI, and ZnTEPP-PBI.
Figure 3. Cycling performance of ZnTEPP-PBI for the oxidative coupling of
benzylamine. Benzylamine (1 mmol), ZnTEPP-PBI (3.5 wt%), MeCN (24 mL), O
2
2
atmosphere (1 atm), white LED lamp (90 mW/cm ), room temperature, 4 h.
Figure 4. Reaction profile for the oxidative coupling of benzylamine. Benzylamine (0.5
mmol), ZnTEPP-PBI (3.5 wt %), MeCN (24 mL), O atmosphere (1 atm), white LED
2
2
lamp (90 mW/cm ), room temperature, 4 h.
Figure 5. ESR spectra of the samples after mixing (A) TEMP or a (B) DMPO solution
with ZnTEPP-PBI and O in the absence or presence of benzylamine in dark under
2
visible-light irradiation or after the addition of benzylamine.
Scheme 1. Structure of ZnTEPP-PBI.
Scheme 2. Proposed mechanism for the oxidative coupling of benzylamine
photocatalyzed by ZnTEPP-PBI

Table 1. Photocatalytic oxidative coupling of benzylaminea
Entry
Catalyst
Conversion/%b
Yield/%b
ND
1
-
ND
70
2
ZnTEPP
70
3
4c
5d
ZnTEPP-PBI
ZnTEPP-PBI
ZnTEPP-PBI
>99
ND
ND
>99
ND
ND
aBenzylamine (0.5 mmol), catalyst (3.5 wt%), MeCN (24 mL), O
atmosphere (1 atm), white LED
2
2
lamp (90 mW/cm ), room temperature, 4 h.
bBased on GC–MS analysis.
cIn the dark.
d
Under argon.

Table 2. Photocatalytic oxidative coupling of amines into imines by ZnTEPP-PBIa
b
Entry
Substrate
Product
Yield (%)
1
93
2
3
4
5
6c
7
8
9
99
99
99
51
96
99
99
53
1
0d
85
aBenzylamine (0.5 mmol), ZnTEPP-PBI (3.5 wt%), MeCN (24 mL), O
atmosphere (1 atm), white
2
2
LED lamp (90 mW/cm ), room temperature, 4 h.
bBased on GC–MS analysis.
cReaction time was 7 h.
dReaction time was 9 h.

Table 3 Control experiments for the photocatalytic oxidative coupling of benzylaminea
Entry
Inhibitor
Conversion/%b
Yield/%b
1
KI
6
6
2
β-carotene
Benzoquinone
Isopropanol
11
22
16
11
22
16
3
4c
aBenzylamine (0.5 mmol), ZnTEPP-PBI (3.5 wt%), inhibitor (1 equivalent), MeCN (24 mL), O
atmosphere (1 atm), white LED lamp, room temperature, 4 h.
bBased on GC–MS analysis.
2
cIsopropanol as the solvent.
Figure 1. (A) FTIR spectra of ZnTEPP, PBI, and ZnTEPP-PBI; (B) Zn 2p XPS spectra of ZnTEPP-
PBI.

Figure 2. (A) UV-Vis-NIR DRS spectra of ZnTEPP, PBI, and ZnTEPP-PBI; (B) Photoluminescence
spectra with an excitation wavelength of 470 nm at 298 K for ZnTEPP, PBI, and ZnTEPP-PBI.
1
00
7
5
2
5
0
5
0
1
2
3
4
5
Cycle numbers
Figure 3. Cycling performance of ZnTEPP-PBI for the oxidative coupling of benzylamine.
2
Benzylamine (1 mmol), ZnTEPP-PBI (3.5 wt%), MeCN (24 mL), O atmosphere (1 atm), white
2
LED lamp (90 mW/cm ), room temperature, 4 h.

1
00
8
6
4
2
0
0
0
0
0
0
1
2
3
4
5
Time /h
Figure 4. Reaction profile for the oxidative coupling of benzylamine. Benzylamine (0.5 mmol),
ZnTEPP-PBI (3.5 wt %), MeCN (24 mL), O
room temperature, 4 h.
atmosphere (1 atm), white LED lamp (90 mW/cm2),
2
Figure 5. ESR spectra of the samples after mixing (A) TEMP or a (B) DMPO solution with
ZnTEPP-PBI and O in the absence or presence of benzylamine in dark under visible-light
irradiation or after the addition of benzylamine.
2

O O
O O
O
N
O
O
N
O
N
N
N
Zn
N
ZnTEPP-PBI
Electron donor
Electron acceptor
Scheme 1. Structure of ZnTEPP-PBI.
Scheme 2. Proposed mechanism for the oxidative coupling of benzylamine photocatalyzed by
ZnTEPP-PBI