A Carbazolyl Porphyrin-Based Conjugated Microporous Polymer for Metal-Free Photocatalytic Aerobic Oxidation Reactions

Article abstract of DOI:10.1002/cctc.202000199

Herein, a carbazolyl porphyrin-based π-conjugated microporous polymer was prepared via simple FeCl₃-catalyzed oxidative polymerization. The resulting polymer (TCPP-CMP) exhibits high surface area, permanent pores, good stability, broad light absorption range and suitable redox potentials. As expected, TCPP-CMP is a highly effective metal-free and heterogeneous photocatalyst for a variety of aerobic oxidation reactions, including oxidative coupling of primary amines, oxidative dehydrogenation of secondary amines, and oxidation of sulfides into sulfoxides using molecular oxygen under visible light irradiation. Importantly, natural sunlight is able to promote the aerobic oxidation of benzylamine and thioanisole via TCPP-CMP photocatalyst with high conversion and selectivity, which are comparable with reactions conducted under artificial light. In addition, heterogeneous TCPP-CMP has good recyclability, which retained its activity even after four cycles. The current work lays the foundation for future applications of TCPP-CMP as metal-free heterogeneous photocatalyst for aerobic oxidation reactions.

Full text of DOI:10.1002/cctc.202000199

The European Society Journal for Catalysis
Supported by
Accepted Article
Title: A Carbazolyl Porphyrin-Based Conjugated Microporous Polymer
for Metal-Free Photocatalytic Aerobic Oxidation Reactions
Authors: Jun Jiang, Zhongxiu Liang, Xiaoyan Xiong, Xiantai Zhou, and
Hongbing Ji
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ChemCatChem
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A Carbazolyl Porphyrin-Based Conjugated Microporous
Polymer for Metal-Free Photocatalytic Aerobic Oxidation
Reactions
[
a]
[a]
[a]
[c]
[b]
Jun Jiang, Zhongxiu Liang, Xiaoyan Xiong, Xiantai Zhou,* and Hongbing Ji*
[
a]
Dr. Jun Jiang, Zhongxiu Liang, Prof. Xiaoyan Xiong
Guangdong Industrial Analysis and Testing Center
Guangdong Academy of Sciences
Guangzhou 510650, People’s Republic of China
E-mail: jiangjgas@163.com
[
[
b]
c]
Prof. Hongbing Ji
Fine Chemical Industry Research Institute, School of Chemistry
Sun Yat-sen University
Guangzhou 510275, People’s Republic of China
E-mail: jihb@mail.sysu.edu.cn
Prof. Xiantai Zhou
School of Chemical Engineering and Technology
Sun Yat-sen University
Zhuhai 519082, People’s Republic of China
E-mail: zhouxtai@mail.sysu.edu.cn
Supporting information for this article is given via a link at the end of the document.
Abstract: Herein,
a
carbazolyl porphyrin-based -conjugated
-catalyzed
applications still require a universal or highly efficient metal-free,
reusable and heterogeneous photocatalyst system for aerobic
oxidation reactions.
microporous polymer was prepared via simple FeCl
3
oxidative polymerization. The resulting polymer (TCPP-CMP)
exhibits high surface area, permanent pores, good stability, broad
light absorption range and suitable redox potentials. As expected,
TCPP-CMP is a highly effective metal-free and heterogeneous
photocatalyst for a variety of aerobic oxidation reactions, including
oxidative coupling of primary amines, oxidative dehydrogenation of
secondary amines, and oxidation of sulfides into sulfoxides using
molecular oxygen under visible light irradiation. Importantly, natural
sunlight is able to promote the aerobic oxidation of benzylamine
and thioanisole via TCPP-CMP photocatalyst with high conversion
and selectivity, which are comparable with reactions conducted
under artificial light. In addition, heterogeneous TCPP-CMP has
good recyclability, which retained its activity even after four cycles.
The current work lays the foundation for future applications of
TCPP-CMP as metal-free heterogeneous photocatalyst for aerobic
oxidation reactions.
Recent reports have shown metal-free heterogeneous
[
8]
3 4
photocatalysts, for example graphitic carbon nitride (g-C N ),
covalent organic frameworks (COFs),[9] hyper-crosslinked
polymers (HCPs),[10] covalent triazine-based frameworks
(CTFs)[ and conjugated microporous polymers (CMPs), as
heterogeneous visible-light catalysts. Particularly, CMPs, a
class of -conjugated organic polymers, are capable of
integrating photoactive monomers into the covalent framework
while retaining its permanent porous structure.[13] Naturally,
CMPs possess outstanding physicochemical properties
including high surface area, permanent pores, excellent
thermostability, high flexibility and broad visible-light absorption,
making it an ideal photocatalytic platform for aerobic oxidation
11]
[12]
reactions. Over the past several years, CMPs based
photoactive monomers such as carbazole,[
12a]
BODIPY,[14]
benzothiadiazole,[ and truxene
15]
[16]
have been developed as
efficient photocatalysts for various aerobic oxidation reactions
of organic compounds such as sulfides and amines. However,
to the best of our knowledge, CMPs-based aerobic oxidation
reactions are performed under artificial light sources such as
xenon and LED lamp, which are usually expensive and require
high-energy setup. Therefore, natural sunlight, an inexhaustible
energy, is an ideal light source for future large-scale industrial
applications.
Introduction
Selective oxidation of organic compounds, such as oxidative
coupling of primary amines, oxidative dehydrogenation of
secondary amines and oxidation of sulfides into sulfoxides, is
an elementary and fundamental conversion in organic
[
1]
chemistry. Especially, aerobic oxidation reactions involving
molecular oxygen (O ) or air as the oxidant, which have
Porphyrins, a class of 18-electron -conjugated macrocycles
with individual photoredox characteristics, are generally
2
attracted considerable interest owing to their renewability,
environmental friendliness and low cost.[2] In this context, visible
light-driven aerobic oxidation reactions based on transition-
metal complexes[3] and organic dyes[4] as photocatalysts have
been extensively reported, but possess numerous drawbacks
including poor stability, precious metals, non-reusability and
metal contamination, thereby restricting their industrial
applications. Recent explorations about reusable homogeneous
photocatalysts have utilized metal-organic frameworks
employed as important building monomers for the construction
[17]
of porous material.
containing CMPs photocatalysts
It has been reported that carbazole-
[12a, 18]
carbazolyl monomer core
consist of small conjugate rings such as benzene or triazine,
whereas a -conjugated macrocyclic core is rare. Compared to
these small conjugate rings, porphyrins possess a broad
absorption rang of light, which promotes photocatalytic
reactions under broad spectrum of natural sunlight. In the
present article, we designed and prepared carbazolyl porphyrin-
based conjugated microporous polymer (TCPP-CMP), which
was employed as a metal-free heterogeneous photocatalyst for
three representative aerobic oxidation reactions, namely:
(
MOFs)[5] and immobilization of photosensitizers on inorganic
materials to overcome this issue.[ Previously, we have
reported tin porphyrin-based porous aromatic framework,[7]
which initially alleviates this drawback. However, sustainable
6]
1
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ChemCatChem
10.1002/cctc.202000199
FULL PAPER
oxidative
coupling
of
primary
amines,
oxidative
dehydrogenation of secondary amines and oxidation of sulfides
to sulfoxides at room temperature. As expected, TCPP-CMP
shows high efficiency and good tolerance toward the
aforementioned reactions over a large scope of substrates.
Especially, natural sunlight is able to drive the oxidation of
benzylamine and thioanisole via TCPP-CMP photocatalyst with
high conversion and selectivity, which are comparable with
those under artificial light sources. In addition, TCPP-CMP
exhibits good recyclability and high reusable efficiently, at least
four cycles without apparent decrease of catalytic performance,
owing to its robust and rigid framework.
Results and Discussion
Figure 2. (A) FT-IR spectra of TCPP monomer and TCPP-CMP polymer; (B)
N 1s XPS spectra of TCPP-CMP; (C) Typical SEM and (D, E) TEM images of
TCPP-CMP.
Preparation and Characterization
N
N
NH
N
NH
N
FeCl
CHCl3
3
N
N
N
N
N
HN
N
HN
N
N
TCPP
TCPP-CMP
Figure 1. Synthesis of TCPP-CMP
TCPP-CMP was synthesized via iron chloride (FeCl
3
)-promoted
oxidative polymerization, which is an efficient method for the
preparation of conjugated microporous polymers (CMPs).[
Typically, polymerization of the monomer, tetrakis (carbazol-9-
ylphenyl) porphyrin (TCPP), was promoted using catalytic
19]
2
Figure 3. (A) Absorption isotherms of TCPP-CMP under N at 77 K; (B) Pore
amount of FeCl
3
in anhydrous chloroform and nitrogen
size distributions of TCPP-CMP (based on the NLDFT method); (C) UV-Vis-
NIR DRS spectra of the monomer TCPP and the polymer TCPP-CMP; Cut in
the image is the energy diagram of the HOMO and LUMO positions of TCPP-
CMP; (D) Steady-state PL emission spectra of the monomer TCPP and the
polymer TCPP-CMP (excitation at 450 nm).
atmosphere (Figure 1). The resulting TCPP-CMP is a purple
red powder, which is insoluble in common organic solvents (e.g.
methanol and chloroform). Thermal analysis of TCPP-CMP
shows excellent thermal stability with only 6% total mass loss
upon heating to 520 °C (Figure S1). Fourier transform infrared
spectroscopy (FT-IR) spectra show the removal of the
The porosity characteristics of TCPP-CMP were studied via
-
1
2
N adsorption isotherms. Figure 3A shows that TCPP-CMP has
characteristic peaks at 712 and 752 cm (specified to the
phenyl ring in the carbazole moiety), and appearance of a peak
2
-1
high Brunauer−Emmett−Teller (BET) surface area of 544 m g
and total pore volume of 0.349 cm3 g-1. Nonlocal density
functional theory (NLDFT) pore-size distribution analysis shows
the presence of abundant micropores, around 0.6, 0.7 and 1.2
nm in size (Figure 3B). Light absorption capacity of the polymer
was assessed using ultraviolet-visible-near-infrared diffuse
reflectance spectrometer (UV-Vis-NIR DRS). Notably, TCPP-
CMP, displays features related to TCPP monomer, with a
strong and broad light absorption range bewteen 200–1200 nm
-
1
at 799 cm (corresponding to the vibration of C−H bonds on the
carbazole moiety) (Figure 2A).[18a,
20]
The solid-state 13C
CP/MAS NMR spectrum reveals a set of peaks in the range of
7-125 ppm (Figure S2), which are related to the aromatic
carbon atoms of the porphyrin macrocycle and
9
carbazolyphenylene. The crucial elemental composition of
TCPP-CMP was analyzed using X-ray photoelectron
spectroscopy (XPS).
N
1s energy level signals are
(Figure 3C). This allows it to promote the electrons of TCPP-
deconvoluted into two well-separated peaks (Figure 2B). The
CMP to the excited state upon sunlight irradiation. According to
the Kubelka−Munk function, the bandgap value of TCPP-CMP
was calculated as 1.73 eV (Figure S3). Cyclic voltammetry
reveals the lowest unoccupied molecular orbital (LUMO)
position of TCPP-CMP at −0.82 V vs. Ag/AgCl (Figure S4),
peak at 400.0 eV is assigned to pyridine N of N-phenyl
carbazole moiety, whereas the peak at 399.5 V peak is
attributed to the pyrrolic nitrogen N of porphyrin macrocycle.[21]
Scanning electron microscopy (SEM) image of the polymer
shows that TCPP-CMP consists of different morphological
structures (particle and fiberlike) at the micrometer scale

which is lower than the reduction potential of O
2
/O
2
(-0.48 V
vs Ag/AgCl).[ Hence, theoretically, TCPP-CMP activates the
22]
(Figure 2C), which are further verified by transmission electron
molecular oxygen to superoxide radical in solution. The
microscopy (TEM) images (Figure 2D and 2E).
2
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matching highest occupied molecular orbital (HOMO) position
was calculated as 0.91 V vs. Ag/AgCl (inset in Figure 3C). To
further define the positions of the conduction band (CB) and
valence band (VB), Mott-Schottky and VB-XPS measurements
of TCPP-CMP were conducted. Mott-Schottky measurement
shows that the flat band position determined from the
intersection is ~ −0.85 V vs Ag/AgCl (Figure S5). Since the CB
potential of n-type semiconductors is approximately equal to the
flat-band potential,[ then CB of TCPP-CMP is estimated as
photobleaching, while heterogeneous TCPP-CMP displayed
good stability and recyclability (see below). Furthermore,
substrate scopes were systemically investigated, and the
results are listed in Table 1. When benzylamine was substituted
with an electron-donating group (i.e. methoxy) or an electron-
withdrawing group (i.e. bromo) under the same reaction
conditions, comparable conversion yields were obtained, but
the selectivity of the corresponding imine was lower than that of
benzylamine (Table 1, entries 1-3). Comparison of ortho- and
para-methoxy substituents show similar yields (Table 1, entries
2 and 4). 3-Picolylamine and 2-thiophenemethylamine, which
represent heterocyclic amines, were well-tolerated and nearly
fully converted with selectivity of 93% and 83%, respectively
(Table 1, entries 5 and 6). TCPP-CMP photocatalyst was also
applied to oxidative dehydrogenation of secondary amines to
afford imine products. For example, dibenzylamine and
dibenzylamine substituted with methoxy moieties were almost
completely converted with selectivity of 77% and 74%,
respectively (Table 1, entries 7 and 8). In addition, N-tert-
butylbenzylamine was converted to the corresponding imine
with 99% conversion and 90% selectivity (Table 1, entry 9).
These results strongly confirm that TCPP-CMP is an efficient
photocatalyst for aerobic oxidation of various amines (e.g.
substituted amines, heterocyclic amines and secondary
amines) to the imines with high conversion and good selectivity.
23]
−
0.85 V vs Ag/AgCl. Moreover, the VB-XPS measurement
indicates that the VB position determined from the intersection
is located at 1.60 eV (Figure S6).[24] Steady-state
photoluminescence (PL) emission spectra show that TCPP-
CMP has a maximum emission peak of 670 nm, which is
significantly red-shifted and slightly weaken in comparison with
the maximum emission peak of 655 in the monomer TCPP
(Figure 3D). Additionally, the shoulder peak at around 724 nm
of TCPP-CMP is weakened compared to that of TCPP. This red
shift along with the decreased intensity suggests the decline of
recombination of charge carriers,[25] which is derived from the
extended -conjugated structure of TCPP-CMP.
Catalytic Performances
Table 1. Photocatalytic oxidation of various amines into imines using TCPP-
[
a]
CMP
Conv.
%)[b]
Sel.
(%)[b]
Entry
Substrate
Product
(
1
2
3
R = H
R = H
99
97
99
94
78
89
R = OMe
R = Br
R = OMe
R = Br
Figure 4. Comparison of TCPP-CMP photocatalytic performance with no
catalyst, g-C
3 4 2
N , TiO and TCPP for aerobic oxidation of benzylamine to
4
5
6
99
99
99
82
93
83
imine. Reaction conditions: benzylamine (0.5 mmol), photocatalyst (10 mg),
o
O
2
(1 atm), white LED (100 W), acetonitrile (10 mL), 25 C and 16 h.
The oxidation of amines into imines is of great interest due to
the versatility of imines as intermediates in the synthesis of
pharmaceuticals.
oxidation of amines, including oxidative coupling of primary
amines and oxidative dehydrogenation of secondary amines, to
evaluate the photocatalytic properties of TCPP-CMP. Firstly,
the photocatalytic performance of TCPP-CMP was compared
[
26]
Herein, we first examined the aerobic
7
8
R’ = H
R’ = H
99
99
77
74
R’ = OMe
R’ = OMe
9
99
90
[
a] Reaction conditions: substrate (0.5 mmol), TCPP-CMP (10 mg), O
2
(1
3 4 2
with no catalyst, commercial g-C N and anatase TiO , and
o
atm), white LED (100 W), acetonitrile (10 mL), 25
Determined by GC-MS.
C and 16 h; [b]
monomer TCPP. Benzylamine, a primary amine, was selected
as the model substrate. As shown in Figure 4, only trace
amounts of imine were formed when no catalyst was employed.
TCPP-CMP provided the highest imine yield among the tested
As a fundamental organic conversion, selective oxidation of
sulfides into sulfoxides is of considerable interest due to its
important role in organic synthesis.[ Therefore, we performed
the aerobic oxidation of sulfides into sulfoxides using TCPP-
CMP as the photocatalyst. Since water can accelerate the
conversion of intermedium persulfoxide to sulfoxide,[28] the
reaction was performed in a mixture of acetonitrile and water
3 4 2
heterogeneous photocatalysts (g-C N and TiO ). In addition,
27]
compared with heterogeneous TCPP-CMP, TCPP monomer
exhibited comparative photocatalytic activity, which was
attributed to its broad visible light absorption. However, after
irradiation of 16 h, the tawny color of TCPP turned into a flaxen
suspended solid (Figure S7), indicating that TCPP was prone to
3
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(
1:1 v/v). As summarized in Table 2, high conversion of sulfides
The reusability of heterogeneous photocatalysts is a vital
factor. Therefore, the recyclability of TCPP-CMP photocatalyst
was investigated in the oxidative coupling of benzylamine to
imine and oxidation of thioanisole to sulfoxide. The catalyst was
easily recycled four times via centrifugation. As shown in Figure
5, TCPP-CMP maintains high photocatalytic performance for
four and five cycles, respectively, which can be attributed to
robust structure of TCPP-CMP and mild reaction conditions.
Furthermore, no clear change in FT-IR spectra (Figure S8) and
solid-state 13C CP/MAS NMR spectra (Figure S9) of TCPP-
CMP were observed before and after five cycles. But the
surface area of TCPP-CMP had a 45% loss after 5 cycles
and selectivity of sulfoxides were achieved for a broad scope of
thioanisole derivatives, tolerating both electron-donating (i.e.
methoxy and methyl) and electron-withdrawing groups (i.e.
methoxy and methyl) (Table 2, entries 1-5). Moreover,
tetrahydrothiophene, a representative of cyclic sulfides, was
almost completely converted into tetramethylene sulfoxide
(
Table 2, entry 6). These results indicate that TCPP-CMP can
efficiently catalyze the conversion of sulfides into sulfoxides
with high conversion and high selectivity.
Table 2. Photocatalytic oxidation of sulfides into sulfoxides using TCPP-
CMP
[
a]
(Figure S10), which may be due to the collapse of the portion
pore owing to the obvious decrease of total pore volumes from
3
-1
3
-1
0
.349 cm g to 0.112 cm g , especially, micropore volume
3
-1
3
-1
from 0.119 cm g to 0.085 cm g . Additionally, kinetic studies
revealed that after reaction times of 6 h and 12 h, benzylamine
and thioanisole were converted to imine and sulfoxide in 95%
and 96% yield, respectively (Figure S11A). Although monomer
TCPP exhibits enhanced photocatalytic activity compared to
TCPP-CMP in the oxidative coupling of benzylamine, but TCPP
is still prone to photobleaching only after 3 h of irradiation
Entry
Substrate
Product
Conv. (%)[b]
Sel. (%)[b]
1
2
3
4
5
R” = H
R” = H
99
99
99
97
99
97
96
98
98
96
R” = OMe
R” = Me
R” = Cl
R” = Br
R”= OMe
R” = Me
R” = Cl
R” = Br
(
Figure S11B).
Natural sunlight is an extensive, cheap and unexhaustible
6
99
99
energy source, and consists of around 3% ultraviolet light, 44%
visible light, and 53% near-infrared light.[16] Therefore, it is
feasible that natural sunlight can replace the artificial light
source that drives aerobic oxidation reactions. Accordingly, we
performed oxidative coupling of benzylamine and oxidation of
thioanisole as the model reaction. As shown in Figure 6, under
natural sunlight irradiation, benzylamine and thioanisole were
almost completely converted in 88% and 99% selectivity for
imine and sulfoxide, respectively. These results are comparable
with those conducted under artificial light source LED irradiation
[a] Reaction conditions: substrate (0.5 mmol), TCPP-CMP (10 mg), O
2
(1
O (10 mL, 1:1 v/v), 25 oC and 16 h;
atm), white LED (100 W), acetonitrile/H
b] Determined by GC-MS.
2
[
(Table 1, entry 1 and Table 2, entry 1), indicating that TCPP-
CMP has great potential for application in large-scale industrial
production in the future.
Figure 6. Photocatalytic reactions for oxidative coupling of benzylamine to
imine and oxidation of thioanisole to sulfoxide under natural sunlight
irradiation for 16
temperature (30−41 °C), light power density (30-77 mW/cm )).
h
in Guangzhou, China (09/23/2019−09/24/2019,
2
Mechanism Consideration
To obtain greater insight into the possible mechanistic pathway
of the photocatalytic oxidation reaction, we performed
background and inhibition experiments (Table 3). The
background experiments verified that the desired reaction did
not proceed in the absence of catalyst or light, and only trace
Figure 5. Recyclability of TCPP-CMP in oxidative coupling of benzylamine
A) and oxidation of thioanisole (B). Reaction conditions: substrate (0.5
(
o
mmol), TCPP-CMP (10 mg), O
2
(1 atm), white LED (100 W), 25 C, 16 h and
O (10 mL, 1:1 v/v, B).
acetonitrile (10 mL, A) or acetonitrile/H
2
2
amount of product was generated in the presence of N (Table
4
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3
, entries 1-3 and 9-11). Then, inhibition experiments with
(DMPO), a typical trapping agent for O
solvent containing TCPP-CMP. Upon visible light irradiation and
atmosphere, a strong specific quartet signal was generated
(Figure 7A), corresponding to DMPO/OOH derived from the
, was added to the
2
various scavengers including KI, -carotene, benzoquinone and
isopropanol were implemented to determine which active
species were actually generated. The addition of KI, -carotene
and benzoquinone, respectively, to the oxidation of
O
2
 [11]
reaction of DMPO with O
2
.
Next, ESR experiments with
benzylamine and thioanisole showed inhibited ((Table 3, entries
2,2,6,6-tetramethylpiperidine (TEMP) as the trapping agent for
O revealed a strong 1:1:1 triplet signal (Figure 7B), related to
2
2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical formed
+
1
5
-7 and 13-15)), suggesting that hole (h ), superoxide radical
anion (O 
) and singlet oxygen (1O
were involved in
2
2
)
[
10, 29]
1
[31]
photooxidation of benzylamine and thioanisole.
Whereas
via the reaction of TEMP with O
2
.
The above ESR results

and 1
isopropanol hardly suppressed the oxidation of benzylamine
and thioanisole (Table 3, entries 8 and 16), indicating that OH
was not an active species for this system.
clearly confirm that TCPP-CMP is capable of O
generation.
2
O
2
Table 3 Blank and inhibition experiments[a]
TCPP-
CMP
Entny
h
Inhibited
Species
Yield
O
2
Scavengers
1
2
3
4
5
6
7
8
+
+

+
+
+
+
+
+

+
+
+
+
+
+

+
+
+
+
+
+
+



n.d.
7




n.d.
93
61
49
16
99

KI
h+
-carotene
benzoquinone
isopropanol
1O
2

2
O
OH
9



























n.d.
4
10
11
12
13
14
15
16




n.d.
96
62
63
36
97

Figure 7. ESR spectra of the samples after mixing (A) DMPO or (B) TEMP
solution with TCPP-CMP and O
in the dark.
2
under visible light irradiation ( > 420 nm) or
KI
h+
-carotene
benzoquinone
isopropanol
1O
2
Hence, based on the above experimental results and related
literature data, a possible mechanism was proposed for TCPP-
CMP photocatalyzed aerobic oxidation of benzylamine and
thioanisole. As shown in Figure 8A, under visible light
irradiation, photocatalyst (PC) TCPP-CMP was excited and

2
O
OH
[
a] Reaction conditions: substrate (0.5 mmol), TCPP-CMP (10 mg), O
2
(1
atm), scavengers (1.0 mmol), white LED (100 W), 25 C, 16 h and acetonitrile
10 mL) for oxidation of benzylamine or acetonitrile/H O (10 mL,1:1 v/v) for
oxidation of thioanisole; [b] Determined by GC-MS.
o
1
produced the singlet excited state of PC (PC*(S )) and the hole
(
2
+
[16]
(
O
h ), respectively.
However, PC*(S
1
) could directly activate

[12a]
2
into O
2
via single electron transfer (SET).
Additionally,
PC*(S
PC (PC*(T
activated O
1
) could possibly convert into the triplet excited state of
)) via facile intersystem crossing (ISC), then PC*(T
into 1O via energy transfer.[7] Moreover, the
Subsequently,
electron
spin
resonance
(ESR)
3
3
)
measurements were conducted to detect superoxide radical
anion (O 
1
2
2
2
) and singlet oxygen ( O
2
), which have been
+
electron-rich benzylamine was oxidized by h into its radical
cation species (I). Furthermore, the reaction between
benzylamine radical cation species (I) and reactive oxygen
accepted as reactive oxygen species in photocatalytic aerobic
reactions.[30]
oxidation
5,5-Dimethyl-1-pyrroline
N-oxide
5
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10.1002/cctc.202000199
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species (O 
by-product H
benzylamine to produce (phenyl)methanimine (II).
and O
1
) produced (phenyl)methanimine (II) and
Synthesis of TCPP-CMP:[19] The solution of anhydrous chloroform (60
2
2
,[16] which reacted rapidly with an additional
mL) with TCPP (0.383 g, 0.3 mmol) was bubble with N
a suspension of FeCl (2.19 g, 13.5 mmol) in anhydrous chloroform (15
mL) was added dropwise to the TCPP solution under N atmosphere.
The resulting mixture was magnetically stirred for 3 days under N at
2
for 30 min. Next,
O
2 2
[
32]
3
The
2
generated (phenyl)methanimine (II) reacted with an additional
benzylamine to obtain the intermediate (III),[ which further
underwent elimination of ammonia under hole-assisted to give
2
33]
room temperature. Then, methanol (100 mL) was added to the mixture,
and stirred for 1 h, and the solid was gathered by percolation and
washed with methanol. The collected solid was stirred acutely in HCl
solution (37%) for 2 h. The solid was collected by filtration and washed
with methanol and water. The obtained solid was extracted in a Soxhlet
extractor with methanol and tetrahydrofuran for 24 h, respectively. The
collected solid was dried in a vacuum oven at 100 oC overnight (yield:
[
34]
the imine product. In the photooxidation of thioanisole (Figure

8
B), the production pathway of reactive oxygen species (O
) was the same as shown in Figure 8A. The electron-
rich thioanisole was oxidized by h into its radical cation species
IV), which further reacted with O
V).[28b] Then, thioanisole could directly react with 1O
produce persulfoxide (V).
with an additional thioanisole to generate the sulfoxide product.
2
1
and O
2
+

(
(
2
to generate persulfoxide
to
Finally, persulfoxide (V) reacted
9
5%).
2
[
9d]
General procedure for photocatalytic aerobic oxidation: The
corresponding amines or sulfides (0.5 mmol) and photocatalyst TCPP-
CMP (10 mg) in 10 mL of solvent were stirred at 25 oC under O
2
(
A) Oxidative coupling of benzylamine into the imine
atmosphere and irradiated with white LED lamps (100 W). After the
reaction was completed, a small portion of the mixture was diluted with
CH Cl , then dried over anhydrous Na SO and filtered with disposable
SET
2
2
2
4
1
PC*(S )
e
needle filter. The collected samples were identified and quantified by
GC-MS analysis, and MS spectra (EI) of typical products are listed in
supporting information.
O
2
3
ISC PC*(T )
e
2 2
H O
1O
2
O
2
NH2
NH
2
NH
2
NH
N
H
III
h+
I
II
NH
2
Acknowledgements
TCPP-CMP
PC)
NH
2
-
NH
3
(
N
(
B) Oxidation of thioanisole into the sulfoxide
The authors are gretaful for the financial support from the
National Natural Science Foundation of China (21425627,
21938001), Guangdong academy of sciences (GDAS)' Project
of Science and Technology Development (2018GDASCX-0114,
SET
1
PC*(S )
e
O
2
ISC PC*(T
3
)
e
2020GDASYL-20200302014),
Guangdong
academy
of
O
2
O
O
S
O
S
S
sciences (GDAS)' Talent Introduction Project of Thousands
doctoral and postdoctor (2020GDASYL-20200103124) and
Guangzhou Foreign Science and Technology Cooperation
Project (201907010004).
1O
2
2
S
S
V
h+
S
TCPP-CMP
PC)
O
2
(
IV
Figure 8. Proposed mechanism of TCPP-CMP photocatalyzed oxidative
coupling of benzylamine to imine (A) and oxidation of thioanisole to sulfoxide
Keywords: Metal-Free • Conjugated Microporous Polymer •
Heterogeneous Photocatalyst • Aerobic Oxidation • Sunlight
(
B).
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Graphical abstract
R
NH2
R N R
N
NH N
N HN
N
N
R
N
R'
R N R'
H
N
O
S
S
R
R'
R
R'
Reactants
Products
The prepared carbazolyl porphyrin-based -conjugated microporous polymer (TCPP-CMP) is an excellent, metal-free, heterogeneous
photocatalyst for organic transformations under white light-emitting diode (LED) lamp or natural sunlight irradiation and ambient
conditions. Mechanism studies have revealed that photocatalyst TCPP-CMP can efficiently activate molecular oxygen (O
2
) to reactive
1
) and superoxide radical anion (O
2
•)) through energy transfer and/or electron transfer process.
oxygen species (singlet oxygen ( O
2
8
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