Solar light active flexible activated carbon cloth-based photocatalyst for Markovnikov-selective radical-radical cross-coupling of S-nucleophiles to terminal alkyne and liquefied petroleum gas sensing

Article abstract of DOI:10.1002/jccs.202000374

Selective radical-radical coupling of terminal alkynes and thiol has been broadly used in chemical synthesis, providing plausible entries to the formation of anti-Markovnikov products. Because of the selective control and Kharasch effect, the formation of Markovnikov products still remains an immense challenge. Herein, we designed a covalent organic polymer, poly(naphthalene 1,4,5,8-tetracarboxylic dianhydrideimide-benzoquinone) through in situ polymerization on activated flexible carbon cloth to function as a light harvester material for selective Markovnikov radical-radical coupling of terminal alkynes and thiol. Mechanistic explorations verified that cross-coupling between radical of terminal alkynes and thiol might be the key route in this organic transformation, such as C—S bond formation. This selective radical-radical Markovnikov of cross-coupling protocol provide an opportunity to assist the synthesis of valuable vinyl sulfide. Additionally, the synthesized material has been explored as liquefied petroleum gas (LPG) sensor for 0.5, 1.0, 1.5, and 2.0?vol% LPG, respectively. At 2.0?vol% LPG, it shows maximum sensor response as 635.29. Least response and recovery times are 2.44 and 1.0?s, respectively.

Full text of DOI:10.1002/jccs.202000374

Received: 30 August 2020
Revised: 17 March 2021
Accepted: 18 March 2021
DOI: 10.1002/jccs.202000374
A R T I C L E
Solar light active flexible activated carbon cloth-based
photocatalyst for Markovnikov-selective radical-radical
cross-coupling of S-nucleophiles to terminal alkyne and
liquefied petroleum gas sensing
Pooja Singh1 | Rajesh K. Yadav1
| Tae Wu Kim2
| Tara C. Yadav3
|
Vitthal Gole4 | Abhishek K. Gupta5 | Kuldeep Singh6 | Kuldeep Kumar7
Bal Chandra Yadav7 | D. K. Dwivedi5
|
1Department of Chemistry and Environmental Science, Madan Mohan Malaviya University of Technology, Gorakhpur, India
2Department of Chemistry, Mokpo National University, Muan-gun, Jeollanam-do, Republic of Korea
3Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, India
4Department of Chemical Engineering, Madan Mohan Malaviya University of Technology, Gorakhpur, India
5Department of Physics and Material Science, Madan Mohan Malaviya University of Technology, Gorakhpur, India
6BRD Medical College, Gorakhpur, India
7Nanomaterials and Sensors Research Laboratory, Department of Physics, Babasaheb Bhimrao Ambedkar University, Lucknow, India
Correspondence
Rajesh K. Yadav, Department of
Abstract
Chemistry and Environmental Science,
Madan Mohan Malaviya University of
Technology, Gorakhpur-273010, Uttar
Pradesh, India.
Selective radical-radical coupling of terminal alkynes and thiol has been
broadly used in chemical synthesis, providing plausible entries to the forma-
tion of anti-Markovnikov products. Because of the selective control and
Kharasch effect, the formation of Markovnikov products still remains an
immense challenge. Herein, we designed a covalent organic polymer,
poly(naphthalene 1,4,5,8-tetracarboxylic dianhydrideimide-benzoquinone)
through in situ polymerization on activated flexible carbon cloth to function as
a light harvester material for selective Markovnikov radical-radical coupling of
terminal alkynes and thiol. Mechanistic explorations verified that cross-
coupling between radical of terminal alkynes and thiol might be the key route
in this organic transformation, such as C S bond formation. This selective
radical-radical Markovnikov of cross-coupling protocol provide an opportunity
to assist the synthesis of valuable vinyl sulfide. Additionally, the synthesized
material has been explored as liquefied petroleum gas (LPG) sensor for 0.5, 1.0,
1.5, and 2.0 vol% LPG, respectively. At 2.0 vol% LPG, it shows maximum sensor
response as 635.29. Least response and recovery times are 2.44 and 1.0 s,
respectively.
Email: rajeshkr_yadav2003@yahoo.co.in
Tae Wu Kim, Department of Chemistry,
Mokpo National University, Muan-gun,
Jeollanam-do, 58554, Republic of Korea.
Email: twkim@mokpo.ac.kr
K E Y W O R D S
cross coupling, cyclic voltammetry, photocatalysis
J Chin Chem Soc. 2021;1–10.
http://www.jccs.wiley-vch.de
© 2021 The Chemical Society Located in Taipei & Wiley-VCH GmbH
1

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SINGH ET AL.
1 | INTRODUCTION
years.[7] Till date, the majority of synthetic methods for
the preparation of vinyl derivative organic compounds
lead to β-substituted useful organic products.[7,8] Never-
theless, the synthesis of α-substituted vinyl sulfides,
which have excellent potential application in pharmaceu-
tical science[9–13] still remains a key challenge. Tradition-
ally, expensive noble transition metal catalysts are used
to the synthesis of α-substituted vinyl organic compounds
with poor selectivity as per established approaches.[14–19]
An alternative strategy with environmentally friendly,
more simple, economical, and sustainable perspective is
therefore highly interesting. Recently, solar light active
photoredox catalysis has become a powerful tool for the
development of a wide range of radical/radical cross-
coupling under mild conditions.[20–22] Thus, we imagined
that solar light active photocatalysis might enable access
to α-substituted vinyl sulfides through radical/radical
cross-coupling processes. Herein, we report on the syn-
thesis and development of a covalent organic polymer
Radical/radical cross coupling between terminal alkynes
and thiols have long served as potential techniques to
access complex molecules.[1] In this situation, exclusively
anti-Markovnikov products were achieved due to the var-
ious effects such as Kharasch effect.[1,2] Accordingly,
techniques allowing for direct highly efficient synthesis
of α-substituted vinyl derivatives from cross-coupling rad-
ical of terminal alkynes and sulfonyl derivatives have
infrequently been reported.[3] In the literature, generated
the stable radical intermediate from the radical/radical
cross-coupling step is the key for the ultimate selectivity
control, and addition of anti-Markovnikov often provides
the utmost stable radical intermediate (Scheme 1a).
Therefore, seeking a new route to synthesize solar light-
based valuable α-substituted fine chemicals such as vinyl
compounds through radical/radical Markovnikov cross-
coupling procedure is interesting and tremendously chal-
lenging. Inspired by the state of the art of radical/radical
cross coupling,[4] we wondered whether the Markovnikov
products, α-substituted vinyl derivatives, can be achieved
through the general and useful cross-coupling of the radi-
cal, a vinyl carbon, and other organic sulfide radicals
(Scheme 1b).
(COP),
poly
(naphthalene
1,4,5,8-tetracarboxylic
dianhydrideimide-benzoquinone) (see Figure S1) through
in situ polymerization on activated flexible carbon cloth
(PNIB-AFCC) (Scheme 2) to function as a light harvester
material for selective Markovnikov radical-radical cross-
coupling of terminal alkynes and thiols. A wide range of
α-substituted vinyl sulfides can be achieved with exclu-
sive Markovnikov regioselectivity.
According to the abovementioned concept,
α-substituted vinyl sulfides, which are not only used in
biological science, medicinal, and pharmaceutical chem-
istry[5] but also serve as useful synthetic intermediates,[6]
were selected as synthetic target molecules. An enlarge-
ment of synthetic approach to vinyl derivative organic
compounds has received important attention in recent
2 | RESULTS AND DISCUSSION
X-ray diffraction (XRD) analysis of T, N, and PNIB-AFCC
photocatalyst is shown in Figure 1. The XRD analysis of
T and N reveals a small weak peak at 2θ value of 8ꢀ, and
15ꢀ, respectively. A shift in the scattering weak and broad
peaks to near about 14ꢀ in the XRD pattern of PNIB-
AFCC photocatalyst may be recognized to T covalently
attached to N, which indicates that imides bond forma-
tion between the amino group of T and anhydride gp of
N and also broad peak of PNIB-AFCC show the poly-
meric nature of photocatalyst and π–π stacking between
AFCC and PNIB photocatalyst.[23]
The UV–visible absorption spectra of PNIB, PNIB-
AFCC photocatalysts are shown in Figure S2. The
absorption spectrum of PNIB-AFCC photocatalyst reveals
at 430 nm. PNIB shows lower absorption at 430 nm while
PNIB-AFCC shows higher absorption in the same range.
The optical band gap of PNIB-AFCC photocatalyst is
2.63 eV. The optical band gap of PNIB photocatalyst is
nearly the same as the calculated band gap (2.5 eV) by
cyclic voltametric study (Figure S3). The shift of absorp-
tion maxima in PNIB-AFCC photocatalyst compared
with that in PNIB indicates the strong π–π interaction
SCHEME 1 (a) C S bond formation on terminal alkyne via
anti-Markovnikov addition. (b) C S bond formation on terminal
alkyne via Markovnikov addition. PT, proton transfer

SINGH ET AL.
3
SCHEME 2 Synthesis of PNIB-
AFCC photocatalyst with T, N, and
AFCC via in situ polymerization method
photocatalyst is entirely different from the morphology of
T and N moieties, due to the covalently attachment of T
and N materials. Finally, the morphology of PNIB-AFCC
photocatalyst is completely different from the PNIB
photocatalyst morphology, due to the edge of AFCC cov-
ered by PNIB and also confirms the strong π-π interaction
between AFCC and PNIB (Figure 3).[27,28]
Dynamic light scattering technique shows the average
particle size of N, PNIB, and PNIB-AFCC photocatalysts
(see Figure S5). The particle sizes of N, PNIB, and PNIB-
AFCC are 1,000, 400, and 250 nm respectively. The parti-
cle size is one of the significant factors for the photo-
catalytic activity of photocatalyst in organic
transformation. Accoring to the previous study,[29] small
particles have the high surface area associated with the
multi-electron collector capacity of incoming light on
PNIB-AFCC, which facilitates the increase of electron
transfer rate on the surface of PNIB-AFCC
photocatalyst.[30]
Rapidly light-scattering techniques were used for
measuring the zeta potential values of PNIB-AFCC and
PNIB. The zeta potential of PNIB-AFCC is 0.0665 mV
which is less than the zeta potential value of PNIB
0.515 mV (see Figure S6). The less value of PNIB-AFCC
is indicating the strong π–π interaction between AFCC
and PNIB photocatalyst.[31]
The covalent attachment of T and N for the formation
PNIB and PNIB-AFCC photocatalysts was characterized
by Fourier transform infrared (FTIR) spectroscopy as
shown in Figure 4a. The FTIR spectra of N (see
Figure S7) shows strong peak at 1,773 cm−1 due to the
dianhydride carbonylic group and T shows stretching
vibration peak at 1,605 cm−1 of C O gp of quinone.[32,33]
After attachment of T and N, a new peak was observed in
the spectrum of PNIB photocatalyst (see Figure S13) at
1,720 cm−1 which is corresponding to the C O stretching
band of the imide group.[34]
FIGURE 1 XRD analysis of PNIB-AFCC (red), T (blue), and N
(green)
between AFCC and PNIB photocatalyst which is highly
suitable for the C S bond formation under solar light
irradiation.[24–25]
The 3D structure and surface morphology of PNIB
and PNIB-AFCC photocatalysts are shown in Figure 2.
Surface morphology of PNIB and PNIB-AFCC photo-
catalysts is explained with the help of atomic force
microscopy (AFM) analysis (Figure 2b,c). The samples
for AFM analysis were prepared by drop-casting ultra-
sonic treatment of PNIB and PNIB-AFCC in
N,N-dimethylformamide (DMF) (0.00027 g/L) on an
unsoiled glass surface. The topographic average rough-
ness of flexible PNIB and PNIB-AFCC was found to be
2.84 and 3.94 nm, respectively (Figure 2b,c). The surface
height of PNIB-AFCC was higher than PNIB
photocatalyst, which indicates that PNIB is covered on
the edge of AFCC and also confirms the strong π–π inter-
action between AFCC and PNIB.[25,26]
The morphology of the N, T, PNIB and PNIB-AFCC
photocatalysts was also investigated by field-emission
scanning electron microscopy. Figure S4 shows the mor-
phology of T and N which is layered and rod shaped,
respectively. Furthermore, the morphology of PNIB

4
SINGH ET AL.
FIGURE 2 (a) 3D structure of the
PNIB-AFCC photocatalyst, along with
AFM roughness and 3D images of
(b) PNIB and (c) PNIB-AFCC
photocatalysts, respectively
The thermal behavior of N, PNIB, and PNIB-AFCC
respectively, as shown in Figure 4b. Further, last weight
loss of PNIB at 600ꢀC is 30.0% and PNIB-AFCC at 615ꢀC
is 15.8% which shows that the PNIB-AFCC photocatalyst
is thermally more stable than the PNIB photocatalyst.
The TGA analysis was conducted for N in nitrogen atmo-
sphere. The achieved results show that no significant
weight loss was observed before near about 385ꢀC for N,
showing good thermal stability. Upon further heating,
the N sample starts to decompose (Figure 4b).
photocatalysts was investigated in the range of tempera-
ture 25–900ꢀC at a heating rate 10ꢀC/min under nitrogen
flow by different techniques such as thermogravimetric
analysis (TGA), differential thermal analysis (DTA), and
derivative thermogravimetry (DTG) analysis. The PNIB
and PNIB-AFCC photocatalysts displayed slow weight
loss with increase temperature up to 900ꢀC. The next
weight loss of PNIB, PNIB-AFCC photocatalysts started
with 200ꢀC and ended with 500ꢀC with weight loss 57.2
and 45.4% which indicates the dissociation of imides
bond of PNIB and PNIB-AFCC photocatalysts,[35]
DTA analysis also explains the thermal behavior
of N, PNIB, and PNIB-AFCC photocatalysts. In
Figure 5a, the broad exothermic peak of N near about at

SINGH ET AL.
5
FIGURE 5 (a) DTA analysis of PNIB-AFCC (red), PNIB (blue),
and N (green) (b) DTG analysis of PNIB-AFCC (red), PNIB (blue)
and N (green)
FIGURE 3 Field-emission scanning electron microscopy
(FESEM) images of (a) PNIB and (b) PNIB-AFCC photocatalysts
This results from the DTA measurements indicates that
PNIB and PNIB-AFCC photocatalysts are thermally
more stable than N.[36]
Similarly, DTG analysis also confirmed the slow
weight loss in N, PNIB, and PNIB-AFCC photocatalysts,
exhibiting excellent thermal stability for all samples
(Figure 5b). PNIB photocatalyst shows weight loss rate at
two stages, first weight loss at 330ꢀC at 0.009 mg/min
and second weight loss 0.01856 mg/min at 617ꢀC. In the
same way, PNIB-AFCC photocatalyst shows weight loss
at 355, 481, 589ꢀC at 0.0829, 0.202, 0.133 mg/min, respec-
tively. On the other hand, N is showing weight loss rate
at 416ꢀC at 0.148 mg/min, which shows that PNIB and
PNIB-AFCC photocatalysts are thermally more stable
than N.[37]
For preparation of thin film of PNIB-AFCC, spin-
coating technique was used. Glass substrates of the
dimension 1 × 1 cm2 were washed with the distilled
water, ethanol, and acetone followed with the ultrasonic
cleaning. A dilute solution of PNIB-AFCC was made by
dissolving it into the iso-propyl alcohol, stirring at
400 rpm along with heating at 50ꢀC for 2 hr. Sonication
for 30 min gave a sol and further, it was spun on glass
substrate with the help of vacuum-assisted photo-resist
spinner at 800 rpm for 20 s. Later, it was dehydrated on
the hot plate for 3 min. The same spin coating and
dehydrating processes were again performed two times to
obtain the uniform and smooth film. Now the electrodes
FIGURE 4 (a) FTIR analysis of PNIB-AFCC (red), PNIB
(blue), and (b) TGA analysis of PNIB-AFCC (red), PNIB (blue) and
N (green)
400ꢀC indicates the disintegration of N. The breakages
of imide bonds in the PNIB and PNIB-AFCC photo-
catalysts were started at 589 and 580ꢀC, respectively.

6
SINGH ET AL.
on the film were deposited with the help of silver paste
and finally this sensing device was ready for the LPG sen-
sor characterization.[38]
The LPG sensor characterization setup is described
in our previous published article.[39] Experimental
setup consists with Keithley Electrometer model
no. 6517B, glass chamber, and a computer. Glass cham-
ber consists with the gas outlet knob at the side of the
chamber and gas inlet at the top of the chamber which
is connected to flow meter of the LPG cylinder. The
LPG was exposed to the sensing device in the glass
chamber and the corresponding resistance of the sens-
ing material was recorded with the help of Keithley
Electrometer.
FIGURE 6 LPG sensing characteristics of PNIB-AFCC
The sensor response, response-recovery time, and
reproducibility are the main parameters of a sensor. The
%
sensor response of
a
sensor is defined by
as CnH2n + 2. As CnH2n + 2 interacted with ionic oxygen
species it forms the complex CnH2nO with water which is
shown in Equation (6).
Equation (1).[40]
ꢀ
ꢀ
ꢀ
ꢀ
Rg −Ra
Ra
%SR =
ꢁ100
ð1Þ
O2ðgasÞ $ O2ðadsÞ
O2ðadsÞ + e− ! O2 −
ð4Þ
ð5Þ
ð6Þ
where Rg is the resistance of sensing element in the pres-
ence of the LPG while Ra is the resistance in the presence
of air.[41] Response and recovery times are those times in
which sensor output reaches to its 90% of the maximum
after the exposing and removing the gas during the
response and recovery cycle. The response and
recovery time of the sensor were calculated with the
exponential growth and decay-fitted data according to
Equations (2 and 3), respectively. [42]
CnH2n + 2 + O2 − ! CnH2nO + H2O + e−
The sensing behavior of PNIB-AFCC-based sensor
was studied by applying the voltage of 20 V between the
electrodes of the sensing elements. To investigate the gas-
sensing characteristics of sensing device, different con-
centrations of LPG were exposed and the correspondingly
different sensing cycles were obtained which are shown
in Figure 6. The four sensing cycles represent the varia-
tions in the resistance of the sensing material for 0.5, 1.0,
1.5, and 2.0 vol% of LPG, respectively, with respect to
time. The resistance of the sensing element in the air was
found as 1.70 × 108 Ω and as the 0.5 vol% LPG was
exposed inside the chamber; the resistance of sensor was
augmented and reached to 4.20 × 108Ω. After that it got
saturated. As LPG was exposed, the resistance was found
increased and as the outlet was opened, resistance
decreased for each cycle. The % sensor response of the
sensor was calculated for 0.5, 1.0, 1.5, and 2.0 vol% LPG
with the help of Equation (1) and is shown in the
Table 1.
ꢁ
ꢂ
−t
tres
Rm = R0exp
ð2Þ
ð3Þ
ꢃ
ꢁ
ꢂꢄ
−t
trec
Rm = R0 1−exp
Its principle is based on the change in electrical prop-
erties of the sensing material when exposed to the gas.
The LPG sensing operation is based on the charge trans-
fer between the LPG and sensing material. At the room
temperature due to applied electrostatic potential, the
equilibrium between the oxygen present on the surface of
the sensing material and atmospheric oxygen takes place
and forms the ionic oxygen species which are shown by
Equations (4) and (5). As the LPG interacts with the sens-
ing material, the formed ionic oxygen captured the elec-
tron from the sensing material and as a result the
density of the electron decreases which increases the
resistance of the sensing material. LPG mainly consists of
methane, propane, and butane generally can be written
In Figure 7a, change in % sensor response with the
variations to LPG concentration has been illustrated and
this also shows that the sensor has a linear variation in %
sensor response with respect to LPG concentration. This
characteristic of the sensor is highly considerable for the
device fabrication purpose. Figure 7b shows the repro-
ducibility curve for 0.5 vol% of the LPG sensor. The

SINGH ET AL.
7
response and recovery times of the sensor were calculated
by the exponential growth and decay fitting for each con-
centration cycle.
The exponential growth and decay-fitted curves for
1.0and 0.5 vol% LPG are shown in the Figure 7c,d having
response-recovery times as 3.51, 1.00 s, respectively. The
calculated response-recovery time for each cycle is shown
in Table 1.
The reaction conditions for C S bond formation were
optimized by a mixture of phenyl acetylene (1a) and thiol
(thiophenol, 2a), base Na2CO3 (1 eq) along with different
type of photocatalyst (1 mol%) under solar light illumina-
tion.[43] Using 0.3 mmol of 1a, 0.6 mmol of 2a, and
1 equivalent of Na2CO3 in 4 ml DMF along with PNIB as
photocatalyst yielded 82% of the product with 84% con-
version of the reactant (Table 2, entry 1). Similarly, when
we used starting material T (1 mol%)with 2 equivalents of
Na2CO3, 4 ml DMF in 1 hr achieved 26% of the product
with 25% conversion of the reactant (Table 2, entry 4).
The best product yield of 99% with the conversion of 99%
reactant was obtained when we use 1 equivalent of
Na2CO3 base along with PNIB-AFCC photocatalyst and
4 ml DMF in 1 hr (Table 2, entry 2). As a result, high
yield and selectivity was observed upon use of 1 equiva-
lent of Na2CO3 in our experiments. After that when we
use only AFCC as photocatalyst, no product formation or
very less yields of the coupling product (Table 2, entry 4).
Combining the all above experiments, we can say that
base, photocatalyst, and light are essential components
for the formation of the desired coupling product
(Table 2, entry 3, and entry 6–7). Herein, in our experi-
ment AFCC enhancing the photocatalytic properties of
PNIB-AFCC photocatalyst (Table 2, entry 2) for C S
bond formation reaction.
TABLE 1 PNIB-AFCC-based LPG sensor attributes
Sensor parameter
Concentration of LPG
(vol%)
Response
time (s)
Recovery
time (s)
% SR
The scope of C S bond formation was considered for
reaction of phenyl acetylene and thiol under the opti-
mized reaction conditions (Table 3, entry 1). As a result,
various substituted phenyl/cyclic acetylene were evalu-
ated as reactants for the C-S bond formation. As depicted
0.5
1.0
1.5
2.0
147.06 2.44
226.47 3.51
381.63 3.95
635.29 5.82
1.00
1.83
2.88
5.54
FIGURE 7 LPG sensor attributes of PNIB-AFCC

8
SINGH ET AL.
TABLE 2 Optimization conditions
for C S bond formation reaction under
solar light irradiation
aReaction conditions: PNIB-AFCC photocatalyst (1 mol%), thiophenol (0.3 mmol), terminal alkyne
(0.6 mmol) Na2CO3 (1 eq), DMF (4.0 ml), blue LED light under N2 atmosphere, 1 hr.
bWithout irradiation of light.
cWithout using photocatalyst.
in Table 3, the reaction with phenyl acetylene with thiol
gives the expected vinyl sulfide products (phenyl
[1-phenylvinyl] sulfane) in 99% yield with outstanding
99% reactant conversion (Table 3, entry 1, Figure S9). Sig-
nificantly 1-ethynyl-1-cyclohexanol also gives product
(1-(1-[phenylthio]vinyl)cyclohexanol) in 97% yield with
97% reactant conversion (Table 3, entry 2, Figure S10), and
4-ethynyl biphenyl yield 98% with 98% conversion
(Table 3, entry 3, Figure S11) of reactant in product
(1-[biphenyl-4-yl]vinyl)(phenyl)sulfane), which was also
confirmed by 1H NMR spectroscopy (see Figure S8). These
following experiments show outstanding light harvesting
and photocatalytic property of PNIB-AFCC photocatalyst.
SCHEME 3 Plausible mechanisms for the radical-radical
On the basis of these experiments, a possible mecha-
nism of solar light-induced radical-radical addition of sul-
fide radical (C) and α-vinyl carbon radical (E) is shown in
Scheme 3. Initially, S-nucleophile (B) is generated from
acid–base neutralization reaction between thiophenol
(A) and base. Consequently, the excited state of
photocatalyst (PC*) reacts with B to gives intermediate C
along with the formation of radical anionic photocatalyst
(PCꢂ ). Then, photocatalyst (PCꢂ ) reacts with terminal
alkyne (D) to induce the formation of an α-vinyl carbon
radical intermediate E. After that radical-radical coupling
product F is formed through the radical reaction and pro-
ton transfer mechanism.
coupling reaction of terminal alkyne and thiol
potassium pthalimide, hydrazine hydrate, DMF,
thiophenol, phenylacetylene, 1-ethynyl-1-cyclohexanol,
4-ethynyl biphenyl, were purchased from Sigma-Aldrich
and TCI Chemicals.
−
−
3.2 | Synthesis of PNIB and PNIB-AFCC
photocatalysts
3.2.1 | Step 1: Synthesis of tetra
(phthalimido)-benzoquinone (TPB)
3 | EXPERIMENTAL
3.1 | Material
Tetra(phthalimido)-benzoquinone (TPB) was prepared by
following the well-established method.[33] First, TCB 5 g
and potassium phthalimide 15.0 g were mixed in 50.0 ml
of ACN. After that the solution was reflux under inert
atmosphere at 80ꢀC for 16 hours. After the completion of
reaction, the solution was removed from the oil bath, and
Tetrachloro-p-benzoquinone (TCB), naphthalene-1, 4, 5,
8-tetracarboxylic dianhydride, acetonitrile (ACN),

SINGH ET AL.
9
TABLE 3 Substrate scope of
regioselective for C S bond formation
reaction
then cooled solution was filtered. Filtrate was washed
with DMF and copious amount of hot deionized water.
Finally, the obtained product was suspended in 200 ml of
ethanol at 78ꢀC, and then was filtered. Filtrate was then
dried in oven at 105ꢀC for 12 hours. Finally, we obtain
5 g of brown-colored TPB compound.
3.2.3 | Step 3: Synthesis of activated
flexible carbon cloth
Activated carbon cloth was prepared by the reported litera-
ture method.[44] Firstly, we take pieces of carbon cloth,
wash it with acetone and huge amount of water for a num-
ber of times. After that the washed cloth was treated with
conc. HNO3 at 100ꢀC for 4 hr. Finally, the acid-treated car-
bon cloth was washed with distilled water followed by ace-
tone and dried in oven overnight at 50ꢀC. Lastly, we obtain
activated flexible carbon cloth for photocatalytic reaction.
3.2.4 | Step 4: Synthesis of PNIB and
PNIB-AFCC photocatalysts
3.2.2 | Step 2: Synthesis of tetraamino-
benzoquinone
About 15.6 mg of TABQ (T), 50.0 mg N, and 250 mg of
activated flexible carbon cloth were mixed into 20.0 ml of
DMSO solution. Mixture was added to an N2-filled 250-ml
two-neck round bottom flask equipped with a magnetic
stirring bar along with condenser. After that the round
bottom flask was placed in an oil bath and refluxed at
180ꢀC for 2 days. The obtain product was washed with
huge amount of water, and acetone. Finally, the obtained
product PNIB-AFCC photocatalyst was dried in oven. The
PNIB photocatalyst was prepared via the same synthetic
route without the addition of activated flexible carbon
cloth. The chemical structure of PNIB photocatalyst (see
Figure S1) was confirmed by both liquid1H and solid-
state13C nuclear magnetic resonance (NMR) spectroscopy
(Figure S12), elemental analysis (Table S1), and Fourier-
transform infrared spectroscopy (Figure S13).
The as-prepared TPB was mixed with 250.0 ml of hydrazine
hydrate and equipped with 500 ml of round bottom flask.
After that, reflux it at 65ꢀC for 2 hours, the obtained prod-
uct is brown-colored tetraamino-benzoquinone (TABQ).

10
SINGH ET AL.
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Chem. Soc. 2009, 131, 8756.
4 | CONCLUSIONS
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5633.
[24] R. Gomes, P. Bhanja, A. Bhaumik, Chem. Commun. 2015, 51,
10050.
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In this study, we have developed a newly designed PNIB-
AFCC photocatalyst for C S bond formation under solar
light irradiation. With the help of microscopy, thermal analy-
sis, and spectroscopy, the as-prepared PNIB and PNIB-AFCC
photocatalysts have been characterized. Electron-transfer
mechanism and photocatalytic activity of photocatalyst was
studied through cyclic voltammetry. Due to the presence of
light harvesting properties, suitable band gap, and photo-
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The C S bond containing vinyl sulfides compound has wide
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ACKNOWLEDGMENTS
This work was supported by Madan Mohan Malaviya Uni-
versity of Technology (MMMUT), Gorakhpur U.P., India.
ORCID
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Rajesh K. Yadav https://orcid.org/0000-0002-5320-5259
Tae Wu Kim https://orcid.org/0000-0002-6370-0907
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SUPPORTING INFORMATION
Additional supporting information may be found online in
the Supporting Information section at the end of this article.
How to cite this article: Singh P, Yadav RK,
Kim TW, et al. Solar light active flexible activated
carbon cloth-based photocatalyst for Markovnikov-
selective radical-radical cross-coupling of S-
nucleophiles to terminal alkyne and liquefied
petroleum gas sensing. J Chin Chem Soc. 2021;
1–10. https://doi.org/10.1002/jccs.202000374