Sulfur Conversion to Donor‐Acceptor Ladder Polymer Networks through Mechanochemical Nucleophilic Aromatic Substitution for Efficient CO2 Photoreduction

Abstract

The development of synthetic methods capable of converting elemental sulfur into conjugated porous sulfur‐rich polymers remains a great challenge, although direct utilization of this readily available feedstock can significantly enrich its uses and circumvent environmental problems during sulfur storage. We report herein mechanochemical (MC) nucleophilic aromatic substitution (SNAr) that enables sulfur conversion into thianthrene‐bridged porous ladder polymer networks with dense donor‐acceptor (D−A) molecular junctions. We demonstrate that the key lies in the generation of bent thianthrene units through a solid‐state ball‐milling condensation reaction between 1,2‐dihaloarenes and elemental sulfur. We also show that the assembling of D−A structural motifs into porous networks affords efficient visible‐light‐driven photocatalytic reduction of carbon dioxide (CO2) with water (H2O) vapor, in the absence of any additional photosensitizer, sacrificial agents or cocatalysts. Exceptional photoinduced charge separation along with boosted exciton dissociation results in a high‐performance of carbon monoxide (CO) production rate of 306.1 μmol g⁻¹ h⁻¹ with near 100 % CO selectivity, which is accompanied by H2O oxidation to O2, as confirmed by both experimental and theoretical results. We anticipate this novel MC SNAr approach will advance processing techniques for direct sulfur utilization and facilitate new possibilities for the synthesis of D−A ladder polymer networks with promising potential in photocatalysis.

Full text

Sustainable Chemistry
Sulfur Conversion to Donor-Acceptor Ladder Polymer Networks
through Mechanochemical Nucleophilic Aromatic Substitution for
Efficient CO2Photoreduction
Na Yang+, Zi-Jian Zhou+, Xiang Zhu,* Jiwei Wu, Yifan Zhang, Tao Wang, Xin-Ping Wu,*
Chengcheng Tian,* Xia Jiang, and Sheng Dai*
Abstract: The development of synthetic methods capable of converting elemental sulfur into conjugated porous sulfur-
rich polymers remains a great challenge, although direct utilization of this readily available feedstock can significantly
enrich its uses and circumvent environmental problems during sulfur storage. We report herein mechanochemical (MC)
nucleophilic aromatic substitution (SNAr) that enables sulfur conversion into thianthrene-bridged porous ladder polymer
networks with dense donor-acceptor (DA) molecular junctions. We demonstrate that the key lies in the generation of
bent thianthrene units through a solid-state ball-milling condensation reaction between 1,2-dihaloarenes and elemental
sulfur. We also show that the assembling of DA structural motifs into porous networks affords efficient visible-light-
driven photocatalytic reduction of carbon dioxide (CO2) with water (H2O) vapor, in the absence of any additional
photosensitizer, sacrificial agents or cocatalysts. Exceptional photoinduced charge separation along with boosted exciton
dissociation results in a high-performance of carbon monoxide (CO) production rate of 306.1 μmolg1h1with near
100% CO selectivity, which is accompanied by H2O oxidation to O2, as confirmed by both experimental and theoretical
results. We anticipate this novel MC SNAr approach will advance processing techniques for direct sulfur utilization and
facilitate new possibilities for the synthesis of DA ladder polymer networks with promising potential in photocatalysis.
Elemental sulfur (S8), as a by-product of the petroleum
refine industry, is an abundant and cheap source on earth
but has limited uses, of which a major application is the
production of sulfuric acid.[1–2] Hence, the interest in efficient
utilization of this readily available feedstock, driven by the
potential promise in tackling safety and environmental
issues during sulfur storage,[3] has inspired an extensive
search for synthetic approaches that are capable of produc-
ing versatile sulfur-rich polymers.[4–6] Despite significant
progresses, straightforward and sustainable conversion of
sulfur is challenge, mainly owing to its poor solubility in
organic solvents and toxicity to free radical initiators or
transition metal catalysts.[7] Thus far, only a handful of
methodologies have been developed, such as inverse
vulcanization[8–11] and multicomponent polymerizations.[12–15]
Nevertheless, the vast majority of the resultant sulfur-rich
polymers lack sufficient π-conjugation within polymeric
architectures and exhibit negligible porous properties, which
significantly restrict their catalytic application potential, for
example artificial photosynthesis. In this regard, the devel-
opment of a facile strategy that gives rise to sulfur-rich π-
conjugated polymers with permanent porosities from ele-
mental sulfur is of great interest, importance and urgency.
Herein, for the first time, we report a mechanochemical
(MC)-assisted synthetic approach for direct conversion of
elemental sulfur into a new type of thianthrene-bridged
donor-acceptor (DA) porous ladder polymer networks.
The key of our success lies in the development of MC
nucleophilic aromatic substitution (SNAr) that enables a
solid-state condensation reaction between elemental sulfur
and 1,2-dihaloarenes toward the production of bent thian-
threne units, which can be further extended to build ladder
polymer networks with rich porosities and dense DA
molecular junctions. Ladder polymers, whose backbones
consist of periodic repeated rings with adjacent rings having
two or more atoms in common, provokes much recent
interest, since inherent restriction of bond rotations limits
[*] N. Yang,+X. Zhu, J. Wu, X. Jiang
School of Carbon Neutrality Future Technology, Sichuan University,
Chengdu 610065, China
E-mail: xiang_zhu@scu.edu.cn
C. Tian
School of Resources and Environment Engineering, East China
University of Science and Technology, Shanghai, 200237, China
E-mail: cctian@ecust.edu.cn
Z.-J. Zhou,+X.-P. Wu
State Key Laboratory of Green Chemical Engineering and Industrial
Catalysis, Centre for Computational Chemistry and Research
Institute of Industrial Catalysis, School of Chemistry and Molecular
Engineering, East China University of Science and Technology,
Shanghai, 200237, China
E-mail: xpwu@ecust.edu.cn
Y. Zhang
School of Environmental and Chemical Engineering, Shanghai
University, Shanghai 200444, China
T. Wang, S. Dai
Chemical Sciences Division, Oak Ridge National Laboratory, Oak
Ridge, TN 37831, USA
E-mail: dais@ornl.gov
[+] These authors contributed equally to this work
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How to cite: Angew. Chem. Int. Ed. 2025, e202419108
doi.org/10.1002/anie.202419108
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