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Thienylene combined with pyridylene throughplanar triazine networks for applications as organic
oxygen reduction reaction electrocatalysts†
Kosuke Sato,*a Nodoka Osadaab and Hidenori Aiharaa

Covalent triazine networks are interesting candidates for organic electrocatalytic materials due to their
tunable, durable and sustainable nature. However, the limited availability of molecular designs that
ensure both two-dimensionality and functional groups in the p-conjugated plane has hindered theirdevelopment. In this work, a layered triazine network composed of thiophene and pyridine ring wassynthesized by the novel mild liquid phase condition. The resulting network showed layered nature since
its intramolecular interaction stabilized its planar conformation. The connection on the 2-position of theReceived 3rd March 2023
Accepted 11th April 2023

heteroaromatic ring prevents steric hindrance. The simple acid treatment method could be used to
exfoliate the networks, resulting in high yields of nanosheets. The planar triazine network showed

DOI: 10.1039/d3ra01431b

superior electrocatalytic properties for the oxygen reduction reaction in the structure-deﬁned covalentrsc.li/rsc-advances

organic networks.

1. Introduction
Covalent triazine frameworks have potential because of theirproperties and the emergence of new functions originatingfrom their extended p-conjugated structures.1–5 The twodimensional (2D) nature enhances their properties, incontrast with the amorphous covalent triazine networks (CTN)with a shorter p-conjugation length.6–8 However, the characteristic 2D structure of the frameworks is ensured by the limited
small linker moieties between the triazine rings. If a versatilestrategy to design 2D structured CTN is revealed, a variety offunctional units can be embedded in the long-range p-conjugated plane and can contribute to the production of fascinating
applications. Herein, we report the design and synthesis oflayered CTN and their exfoliation into nanosheets under mild
conditions (Fig. 1). The layered CTN bearing pyridylenethienylene linkers (Py–Th) exhibited enhanced electrocatalytic
activity for the oxygen reduction reaction (ORR) in the structuredened covalent organic networks.
Recently, various electrochemical ORR catalysts have beenstudied as alternative noble metal-based electrocatalysts.
Covalent organic network polymers have attracted attention asinteresting electrocatalysts, owing to their sustainability, lowsolubility to solution, and structural tunability.9–13 In particular,
p-conjugated network polymers comprising heteroaromaticrings
present
great
potentialfororganic
ORR
electrocatalysts.14–23 The electronegative nitrogen and electropositive carbon atom at appropriate distances contribute to themulti-point interactions with oxygen.21,22 Considering thatplanarity is a key factor that ensures smooth charge transfer andhigh interface area, 2D covalent organic frameworks arepotential candidates as superior organic electrocatalysts.19–23
However, only a limited number of highly crystalline CTN havebeen reported because symmetry and atness are required foraOrganic Materials Chemistry Group, Sagami Chemical Research Institute, 2743-1
Hayakawa, Ayase, Kanagawa 252-1193, Japan. E-mail: kosuke-sato@sagami.or.jpb

Course of Applied Science, Graduate School of Engineering, Tokai University, 4-1-1
Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan† Electronic supplementary information (ESI) available: Detailed procedures ofthe synthesis and measurement, characterization of the reference samples andcomparisonofelectrochemical
properties.
See
DOI:
https://doi.org/10.1039/d3ra01431b

11794 | RSC Adv., 2023, 13, 11794–11799

Fig. 1 (a) Schematic representation of the liquid-phase cyclization forthe synthesis of amorphous layered triazine networks. (b) Molecular
structures of the triazine networks synthesized in the present study.

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the linker moiety between triazine rings.6–8,24,25 The development of a strategy to obtain layered CTN can facilitate theunprecedented combination of the functional groups as novel
2D triazine networks. Here, we synthesized layered CTN containing both electron donor units and catalytic active sites toenhance the electrocatalytic properties.
The exfoliation of layered materials is an eﬀective method for
obtaining 2D materials.26–28 Organic layered compounds
comprising layers stacked via van der Waals interaction such ascarbon-related materials, covalent organic frameworks, andlayered network polymers are exfoliated into nanosheets in theliquid phase with the application of certain stimuli.29–37 In
previous studies, several methods such as liquid-phase,mechanical, and charged exfoliation have been applied to thetriazine frameworks.31–36 The periodic highly crystalline structure in the lateral direction reinforces vertical interlayer interaction; therefore, the exfoliation of the triazine frameworks
requires harsh conditions. The present study prepared lowcrystalline 2D structured CTN to facilitate exfoliation. In ourprevious study, amorphous layered conjugated-polymer
networks were reported as eﬀective organic electrocatalysts forwater splitting.37 The amorphous layered structure increased
the interface area and facilitated charge transportation. Herein,
we report the synthesis of amorphous layered CTN for ORR
electrocatalysts. The planar conformation of the heteroaromatic
linker is a key factor for the 2D nature. The resultant lowcrystalline CTN were eﬃciently exfoliated into nanosheets inmild liquid phase. Moreover, the resultant layered Py–Th wasapplied to a metal-free electrocatalyst for ORR.

2.

Materials and methods

2.1

Synthesis of Py–Th

Under air, potassium hydroxide (1.9 mg, 0.033 mmol) and 18crown-6 ether (8.5 mg, 0.033 mmol) was dissolved in ethanol (1mL) and stirred for 10 min. The solution was concentrated toremove solvent under reduced pressure to give an oil product.
To this oil, M1 (500 mg, 0.80 mmol) and xylene (0.8 mL) wereadded. The mixture was reuxed at 150 °C for 48 h. Aer coolingto the room temperature, the crude product was corrected byltration. The crude product was puried by washing withxylene, CHCl3 and water to give Py–Th as yellow solid (405 mg,
81%).
2.2

Characterization

The molecular structure was analyzed by Fourier transform
infrared (FT-IR) spectroscopy using attenuated total reection
method (Jasco, FT-IR 4200). The light absorption properties
were measured by ultraviolet-visible (UV-vis) spectrometer(Jasco, UV-vis 770) with diﬀuse reection method. The bonding
states were estimated by X-ray photoelectron spectroscopy (XPS,
outsourced analysis). The pelletized CTN samples were
measured. The 1H-NMR chart in CDCl3 solution is obtained by
nuclear magnetic resonance (NMR, Bruker, Ascend 400). The
13
C-NMR charts in solid states were obtained by crosspolarization/magic angle spinning method (outsourced© 2023 The Author(s). Published by the Royal Society of Chemistry

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analysis). Assemble structure was analyzed by X-ray diﬀraction(XRD) with Cu-Ka radiation (Rigaku, Smart Lab). The powderedsample was set on a silicon sample holder without diﬀraction
peaks in the measured range. The morphologies of the CTN
samples were observed using a eld-emission type scanningelectron microscopy (SEM, JEOL, JSM 7100 F). The dispersion
liquid containing the exfoliated CTN was dropped on a heatedcopper foil for SEM observation.
2.3

Calculation and simulation

DFT calculations to study the stable conformation of the CTN
performed based on B3LYP-D3BJ/6-31G++(d,p) level theory byusing Gaussian 16. Model compounds containing around 70
atoms were optimized on that condition for a simplicity. In XRD
chart simulation, periodic 2D cartesian of Py–Th was optimized
on B3LYP/6-31G(d) level theory. The 3D coordinate was constructed by laminating the 2D cartesian with interlayer distanceaccording to the literature.1,6
2.4

Electrochemical measurements

A three-electrode setup in a beaker cell was used for electrochemical measurements. A grassy carbon rod (3 mm of diameter) and Ag/AgCl electrode with saturated KCl solution wereused as a counter electrode and reference electrode. The catalyst
lm coated ring-disk electrode (RDE, grassy carbon, 5 mm indiameter) was used as the working electrode. The catalyst lm
was consisting of the CTN, conductive carbon (Vulcan XC-72R,
Cabot) and Naon (purchased from Aldrich). Typically, themixture of Py–Th/carbon was prepared via polymerization of M1
in a solution containing 9 times the weight of the conductive
carbon. To obtain the catalyst ink, the Py–Th/carbon mixture (5mg) and Naon solution (0.05 mL) were dispersed in ethanol(0.95 mL) with sonication. The catalyst ink (35 mL) was casted to
the RDE and dried at 60 °C to fabricate the catalyst lm.
Conductive carbon without the CTN and Pt/C (10 wt%, Aldrich)were used as reference. Detailed setups were described in the
ESI.†

3.

Result and discussion

3.1

Material synthesis and characterization

The triazine networks, Py–Th, were synthesized by a basecatalyzed cyclization of the trinitrile monomer (M1). M1 wassynthesized from commercially available reagents via threesteps (Scheme S1 in the ESI†). The liquid-phase polymerizationof M1 was performed in xylene using KOH/18-crown-6 ether toactivate the nitrile group. Py–Th was obtained in 81% yield. To
the best of our knowledge, this is the rst report on the basecatalyzed liquid-phase polymerization of nitrile groups, incontrast to reported acid-catalyzed cyclization to construct
triazine networks.2–5,38,39 When the nitrile monomer contains
basic groups such as pyridines and amines, the base-catalyzed
approach, under mild liquid-phase conditions, is more eﬀective than the acid-catalyzed trimerization method.
The resultant product was identied to be Py–Th by solidstate NMR, XPS, and FT-IR absorption spectroscopy (Fig. 2a–

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Fig. 2 (a) Solid-state nuclear magnetic resonance (NMR) chart for Py–
Th. (b–d) X-ray photoelectron spectroscopy (XPS) spectra of Py–Th
focusing on C 1s, N 1s, and S 2p. (e) Fourier transform infrared (FT-IR)
spectra of M1 and Py–Th.

e). The attribution of NMR signals was performed according to
the comparison of the experimental and simulated charts(Fig. 2a and S1†). The experimental and simulated charts weresimilar; therefore, the NMR chart shows the generation of Py–
Th. The XPS spectra show the bonding states of the carbon,
nitrogen, and sulfur atoms. The C 1s XPS spectrum was tted
into ve-carbon species at the binding energies of 284.1, 284.9,
285.8, 286.5, and 288.4 eV, corresponding to the C–C, C]C, S–
C, N]C–N, and C^N groups, respectively (Fig. 2b). The C^N
group observed on the Py–Th sample originated from terminalgroups. The photoelectron signals attributed to N 1s and S 2p
were detected from the resultant sample (Fig. 2c and d). The N
1s spectrum was tted into two nitrogen species at the binding
energies of 398.2 and 400.7 eV attributed to the C]N–C andC^N groups, respectively. The FT-IR spectra revealed theformation of Py–Th (Fig. 2e and S1†). The resultant polymer
sample exhibited the absorption bands of the triazine-ring
stretching vibration at 1355 and 1503 cm−1 and aromatic
C]C stretching vibration at 1404 and 1445 cm−1. The triazine
derived absorption peaks were slightly shied from 1347 and
1496 cm−1 of M1 due to appearance of tri-thienyl triazine
moiety. In addition, the absorption bands were broader thanthose of the monomer during the polymerization. The absorption at 2210 cm−1 derived from the stretching vibration of C^N
groups reduced aer the polymerization. These spectroscopies
indicated the formation of Py–Th by liquid-phase polymerization. Py and Ph–Th were synthesized and characterized as
reference samples (Schemes S2, S3 and Fig. S2†).

3.2

Assembled structures

The stable conformation of Py–Th was calculated using thedensity functional theory (DFT) method based on the
B3LYP+D3BJ/6-31+G(d,p) level theory (Fig. 3a). The model

11796 | RSC Adv., 2023, 13, 11794–11799

Fig. 3 (a) Dihedral angles of the optimized structures calculated byusing the DFT method. (b) XRD proﬁles of Py, Ph–Th, and Py–Th(yellow, blue, and red lines, respectively). (c) Comparison of experimental and simulated XRD charts of Py–Th. The stacking states corresponding to eclipsed (i), staggered (ii) and partially slipped (iii)
displacement with (0, 0), (0.5, 0.5) and (0.2,0.2) of oﬀset, respectively.

compound corresponding to Py–Th was optimized to
a completely at nature with practically 0° of dihedral angles.
The angle scan prole of the dihedral angle between the pyridine and thiophene rings shows that Py–Th exhibited two
diﬀerent stable planar conformations (Fig. S3†). The stabler
conformation appeared to be stabilized by the strong intramolecular interaction between the nitrogen and sulphur
atoms.40 The molecular design of Py–Th can realize a planar
primal layer comprising multiple rings. The connection on the
2-position of the heteroaromatic ring prevents steric hindrance
between the C–H bonds of adjacent linkers. The strategy was
eﬀective in the design of 2D organic networks.
The X-ray diﬀraction (XRD) results indicated that Py–Th
formed a roughly stacked layered structure (red line in Fig. 3b).
Py–Th exhibited broadened weak peaks around 2q = 16.8° and
25.9°, corresponding to the lattice spacings of 5.3 and 3.4 Å,
respectively. The periodic space around 3.4 Å corresponded tothe interlayer distance of p–p stacking.1,39 The broadened
diﬀraction peak indicated that the interlayer distance of Py–Th
had a broad distribution centered at 3.4 Å. The periodic spacearound 5.3 Å was ascribed to the weak periodicity in the planar
network comprising heteroaromatic rings. According to thecomparison of the experimental and simulated charts, Py–Th
containing the partially slipped stacking (Fig. 3c). Three types of© 2023 The Author(s). Published by the Royal Society of ChemistryView Article Online

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A-B stacking state displaced from next layer were considered.
The partially slipped stacking displaced by (0.2, 0.2) of oﬀset
explain the periodic space around 5.3 Å. Furthermore, thebroaden diﬀraction in range of 2q = 5–20° should be derived
from various slipped stacking states. Therefore, Py–Th haveperiodicity in laminated direction but low periodicity in lateral
direction.
Py, classied as a typical 2D triazine frameworks, exhibited
diﬀraction peaks around 2q = 16.6° and 26.5° (yellow line,
Fig. 3b). Py and Py–Th exhibited similar low-periodic layered
structures. Contrarily, Ph–Th did not exhibit diﬀraction peaksin the XRD charts (blue line, Fig. 3b). The Ph–Th polymer was in
an isotropic amorphous state because of the twisted nature
derived from the distortion between the benzene and thiophenerings. The simulated dihedral angle of Ph–Th was 24.5° for thebenzene–thiophene bond (Fig. 3a). The lack of atness resulted
in the amorphous nature of Ph–Th. We expect that the propermolecular design toward a planar conformation will enabletriazine networks to assemble a layered structure although thelinkers comprise multiple functional aromatic rings.
3.3

Macroscopic morphology and exfoliation

The anisotropic morphology of Py–Th was observed by scanningelectron microscopy (SEM). The average particle size of Py–Th
was 6.51 ± 3.0 mm. The Py–Th particle exhibited diﬀerent
surface morphologies: smooth and pleated in the plane andvertical directions of the image, respectively. The pleatedsurface corresponded to a cross-section of the laminated layers(highlighted by red arrow in Fig. 4a). The p–p stacking of the

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primal 2D triazine networks of Py–Th formed the layered
structure on the micrometer scale. Mesopore and micropore of
Py–Th were not observed by typical nitrogen adsorption
method. Its amorphous state in the lateral direction may inhibit
to constructing construct continuous pores. The conductivity of
Py–Th was measured on the pelletized samples, but it did notshow a signicant value. The behaviour should be originatingfrom its semiconductor type electronic structure according to
the previous literatures.2,3The layered Py–Th particle was exfoliated into nanosheets inthe liquid phase (Fig. 4b). The layered Py–Th was dispersed in
an HCl aqueous solution (1 mol dm−3) under ultrasonic irradiation for 15 min. Thereaer, the dispersion liquid wasmaintained under stirring at 60 °C for 24 h. The dispersion of
Py–Th was obtained aer centrifugation and decantation toremove the unexfoliated precipitate. The SEM images show the
Py–Th nanosheets, which exhibited an anisotropic shape whose
size was 2.23 ± 0.30 mm in width and 103 ± 20 nm in thickness(Fig. 4c and d).
The eﬃciency of the exfoliation was estimated from theweight of the precipitate in the centrifugation step. The exfoliation yields of Py–Th and Py were 80% and 66%, respectively,
which were comparable to those of earlier studies under harshconditions, such as mechanical mixing and chemical
oxidation.32–36 The driving force of the exfoliation process wasconsidered to be the protonation of the pyridine moieties underacidic conditions. The protonation of Py–Th was conrmed by
UV-Vis spectroscopy (Fig. 3e). The Py–Th spectrum exhibiteda redshi of its absorption edge aer it had been immersed in
an aqueous HCl solution. The redshi was not observed for Ph–
Th but for Py (Fig. S2†). The protonated pyridine moieties
facilitated the intercalation of solvent molecules. In addition,
the low crystallinity of Py–Th may have prompted the exfoliationaccording to the diﬀerence in the yields of Py–Th and Py.

3.4

Fig. 4 (a) Scanning electron microscopy (SEM) image of the pristine

Py–Th particle (scale bar, 5 mm). (b) SEM image of the exfoliated Py–Th
nanosheets (scale bar, 5 mm). (c and d) Thickness (c) and lateral (d) size
histograms of the nanosheets. (e) Ultraviolet-visible (UV-Vis) spectra of
Py–Th samples. Pristine (black line) and samples after immersion in
HCl aqueous solution. (inset) photograph of Py–Th nanosheets
dispersion in HCl aq.

© 2023 The Author(s). Published by the Royal Society of ChemistryElectrochemical properties

The Py–Th electrode functioned as an ORR electrocatalyst ina basic aqueous electrolyte (Fig. 5a and S4†). The working
electrode was prepared by the proposed polymerization methodin the presence of conductive carbons as supports. The
dispersion of the mixture comprising the triazine networks,
conductive carbon, and binder ionomer was cast on a glassy
carbon electrode. The linear sweep voltammetry (LSV) results ofthe triazine network electrodes indicated that the Py–Th electrode exhibited a superior electrocatalytic ORR performance
than those of Py and Ph–Th (Fig. 5b). The onset potentials of the
Py–Th, Py, and Ph–Th electrodes were 0.76, 0.66, and 0.69 V (vs.
RHE), respectively. The LSV results of the Py–Th electrodeexhibited a diﬀusion-limited current in a high overpotential
region, while those of the Ph–Th and Py electrodes exhibiteda reaction-limited current mode. The half-wave potential was
0.68 V vs. RHE on the Py–Th electrode, and its catalytic property
was reproducible (Fig. S5†). The Tafel slopes were 81, 84, and
85 mV per decade for Py–Th, Py, and Ph–Th, respectively(Fig. 5c). Moreover, the onset potential of Py–Th was unchangedaer cyclic voltammetry within 1.2–0 V (vs. RHE) for 250 cycles

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RSC AdvancesPaperelectrocatalyst. Further enhancement of the catalytic performance can be achieved using an advanced structural designfrom molecular to nanometer scales.

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4. Conclusions
The synthesis and electrocatalytic application of amorphouslayered triazine networks were developed. The distortion-freecombination of heteroaromatic rings was the key strategy forthe layered structure. The nanosheets were easily obtainedusing the protonation-assisted exfoliation method. The laterally
low-periodic layered triazine networks exhibited enhanced ORR
electrocatalytic activities. These networks, positioned between
covalent triazine frameworks and CTN, contribute to expanding
the molecular design of organic 2D materials toward highperformance electrocatalysts.
Fig. 5 Electrocatalytic ORR properties of Py–Th and related samples
in O2 saturated 0.1 mol dm−3 KOH aqueous electrolyte. (a) LSV of Py–
Th on various rotating speed. (b) LSV of Py–Th (red line), Ph–Th (blueline), Py (yellow line), the control samples consisting of conductive
carbon and binder (black line), Pt/C (grey line), and layered Py–Th after
cyclic voltammetry in the range 1.2 to 0 V (vs. RHE) for 250 cycles (reddashed line). RDE working electrode was set to be 1600 rpm ofrotating speed. (c) Tafel plots corresponding to the LSV (d) relationshipof disk current on Py–Th electrode (black line), ring current (red line),and calculated nET (blue line). RRDE Pt ring electrode was set to 0.3 V
vs. RHE.

Conﬂicts of interest
There are no conicts to declare.

Acknowledgements
Financial support is gratefully acknowledged from JSPS
KAKENHI (21K14734).

Notes and references(red dashed lines, Fig. 5b). The activity of the Py–Th electrodewas hardly changed when electrolyte contained methanol(Fig. S5†). These results implied that Py–Th can be used asa superior ORR electrocatalyst.
The selectivity of the 4-electron reduction path and 2-electron reduction path was studied by using rotated ring-disk typeworking electrode (Fig. 5d). The estimated electron transfer
number is 3.77 for Py–Th electrode at 0.60 V vs. RHE. The value
indicates that the 4-electron reaction is a major path. The
enhanced electrocatalytic performance was explained by the
combination of pyridine ring and thiophene ring in at conjugated plane. A number of the previous works proposed that theactive site of electrocatalytic ORR was the carbon atom next topyridinic nitrogen (Fig. S6†).22,41,42 The electron donating thiophene moiety contributes to increasing Lewis basicity of theactive site. Coexistence of both electron donor and active site inplaner CTNs is eﬀective design for enhanced organic ORR
catalyst.
The onset potential of Py–Th is one of its best properties,
compared with previous studies regarding the structure-dened
covalent organic frameworks (Fig. S7 and Table S2†). In terms of
the half-wave potential and the nET, Py–Th showed properties
that were comparable to those of the top groups. Although a few
previous studies reported superior properties, they employeda high-temperature process that degraded the molecular
structure. The Py–Th electrode exhibited enhanced properties
and stability as a metal-free and structure-dened ORR

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1 M. A. Kuhn and A. Thomas, Angew. Chem., Int. Ed., 2008, 47,
3450–3453.
2 X. Jiang, P. Wang and J. Zhao, J. Mater. Chem. A, 2015, 3,
7750–7758.
3 X. Li, P. Yadav and K. P. Loh, Chem. Soc. Rev., 2020, 49, 4835–
4866.
4 V. S. Vyas, F. Haase, L. Stegbauer, G. Savasci, F. Podjaski,
C. Ochsenfeld and B. V. Lotsch, Nat. Commun., 2015, 6, 8508.
5 S. Zhang, Q. Yang, C. Wang, X. Luo, J. Kim, Z. Wang and
Y. Yamauchi, Adv. Sci., 2018, 5, 1801116.
6 P. Kuhn, A. Forget, D. Su, A. Thomas and M. Antonietti, J. Am.
Chem. Soc., 2008, 130, 13333–13337.
7 M. Liu, L. Guo, S. Jin and B. Tan, J. Mater. Chem. A, 2019, 7,
5153–5172.
8 K. Sakaushi and M. Antonietti, Acc. Chem. Res., 2015, 48,
1591–1600.
9 C. Lin, D. Zhang, Z. Zhao and Z. Xia, Adv. Mater., 2018, 30,
1703646.
10 M. L. Pegis, C. F. Wise, D. J. Martin and J. M. Mayer, Chem.
Rev., 2018, 118, 2340–2391.
11 R. K. Gupta, Organic Electrodes: Fundamental to Advanced
Emerging Applications, Springer Nature Switzerland AG,
Cham, 2022.
12 A. F. M. EL-Mahdy, C. H. Kuo, A. Alshehri, C. Young,
Y. Yamauchi, J. Kim and S. W. Kuo, J. Mater. Chem. A,
2018, 6, 19532–19541.
13 A. F. M. EL-Mahdy, C. Young, J. Kim, J. You, Y. Yamauchi and
S.-W. Kuo, ACS Appl. Mater. Interfaces, 2019, 11, 9343–9354.

© 2023 The Author(s). Published by the Royal Society of ChemistryView Article Online

Open Access Article. Published on 17 April 2023. Downloaded on 9/21/2024 6:29:17 AM.
This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.

Paper
14 J. Guo, C. Lin, Z. Xia and Z. Xiang, Angew. Chem., Int. Ed.,2018, 57, 12567–12572.
15 X. Long, D. Li, B. Wang, Z. Jiang, W. Xu, B. Wang, D. Yangand Y. Xia, Angew. Chem., Int. Ed., 2019, 58, 11369–11373.
16 S. Roy, A. Bandyopadhyay, M. Das, P. P. Ray, S. K. Pati and
T. K. Maji, J. Mater. Chem. A, 2018, 6, 5587–5591.
17 D. Li, C. Li, L. Zhang, H. Li, L. Zhu, D. Yang, Q. Fang, S. Qiu
and X. Yao, J. Am. Chem. Soc., 2020, 142, 8104–8108.
18 S. Royuela, E. Martı́nez-Periñán, M. P. Arrieta, J. I. Martı́nez,
M. M. Ramos, F. Zamora, E. Lorenzo and J. L. Segura, Chem.
Commun., 2019, 56, 1267–1270.
19 W. Yu, S. Gu, Y. Fu, S. Xiong, C. Pan, Y. Liu and G. Yu, J.
Catal., 2018, 362, 1–9.
20 G. Jiang, L. Zhang, W. Zou, W. Zhang, X. Wang, H. Song,Z. Cui and L. Du, Chin. J. Catal., 2022, 43, 1042–1048.
21 J. Liu, C. Wang, Y. Song, S. Zhang, Z. Zhang, L. He and
M. Du, J. Colloid Interface Sci., 2021, 591, 253–263.
22 T. Boruah, S. K. Das, G. Kumar, S. Mondal and R. S. Dey,
Chem. Commun., 2022, 58, 5506–5509.
23 J. Liu, Y. Hu and J. Cao, Catal. Commun., 2015, 66, 91–94.
24 S. Ren, R. Dawson, A. Laybourn, J. Jiang, Y. Khimyak,
D. J. Adams and A. I. Cooper, Polym. Chem., 2012, 3, 928–934.
25 J. W. Colson and W. R. Dichtel, Nat. Chem., 2013, 5, 453–465.
26 V. Nicolosi, M. Chhowalla, M. G. Kanatzidis, M. S. Strano
and J. N. Coleman, Science, 2013, 340, 1226419.
27 (a) X. Zhuang, Y. Mai, D. Wu, F. Zhang and X. Feng, Adv.
Mater., 2015, 27, 403–427; (b) L. Niu, J. N. Coleman,
H. Zhang, H. Shin, M. Chhowalla and Z. Zheng, Small,2016, 12, 272–293.
28 P. Peng, L. Shi, F. Huo, S. Zhang, C. Mi, Y. Cheng and
Z. Xiang, ACS Nano, 2019, 13, 878–884.

© 2023 The Author(s). Published by the Royal Society of Chemistry

RSC Advances
29 S. Haldar, K. Roy, R. Kushwaha, S. Ogale andR. Vaidhyanathan, Adv. Energy Mater., 2019, 9, 1902428.
30 Y. Ishijima, M. Okaniwa, Y. Oaki and H. Imai, Chem. Sci.,
2017, 8, 647–653.
31 Y. Zhu, M. Qiao, W. Peng, Y. Li, G. Zhang, F. Zhang, Y. Li and
X. Fan, J. Mater. Chem. A, 2017, 5, 9272–9278.
32 J. Liu, M. Liu, X. Wang, K. Wang, S. Jin and B. Tan, Adv.
Mater. Interfaces, 2021, 8, 2100374.
33 J. Liu, P. Lyu, Y. Zhang, P. Nachtigall and Y. Xu, Adv. Mater.,
2018, 30, 1705401.
34 M.-S. Kim, C. S. Phang, Y. K. Jeong and J. K. Park, Polym.
Chem., 2017, 8, 5655–5659.
35 H. Liu, Q. Li, Y. Zhu, M. Zhang, R. Liu, X. Li, X. Kang, Z. Li
and S. Qiao, J. Mater. Chem. C, 2017, 6, 722–725.
36 H. Zhang, W. Sun, X. Chen and Y. Wang, ACS Nano, 2019, 13,14252–14261.
37 S. Yano, K. Sato, J. Suzuki, H. Imai and Y. Oaki, Commun.
Chem., 2019, 2, 97.
38 S. Ren, M. J. Bojdys, R. Dawson, A. Laybourn, Y. Z. Khimyak,
D. J. Adams and A. I. Cooper, Adv. Mater., 2012, 24, 2357–
2361.
39 S. Yu, J. Mahmood, H. Noh, J. Seo, S. Jung, S. Shin, Y. Im,
I. Jeon and J. Baek, Angew. Chem., Int. Ed., 2018, 57, 8438–
8442.
40 N. E. Jackson, B. M. Savoie, K. L. Kohlstedt, M. O. de la Cruz,
G. C. Schatz, L. X. Chen and M. A. Ratner, J. Am. Chem. Soc.,
2013, 135, 10475–10483.
41 D. Guo, R. Shibuya, C. Akiba, S. Saji, T. Kondo and
J. Nakamura, Science, 2016, 351, 361–365.
42 S. Navalon, A. Dhakshinamoorthy, M. Alvaro, M. Antonietti
and H. Garcı́a, Chem. Soc. Rev., 2017, 46, 4501–4529.

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