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Synthesis of a crystalline two-dimensional [c2]daisy chain honeycomb network

Nature Synthesis volume 4, pages 922–930 (2025)Cite this article

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Abstract

Molecular daisy chains are mechanically bonded materials with unique properties and compelling structures. Despite the exploration of numerous daisy chain structures, the synthesis of a crystalline mechanically interlocked polymer comprising daisy chain units remains elusive because flexible linkers typically yield amorphous gels, while rigid structures lack processability. Here we combine supramolecular crystallization preorganization with post-insertion of mechanical bonds to address this limitation. We use a C3-symmetric tritopic monomer with ammonium moieties and oligoether arms to generate a preorganized supramolecular honeycomb-like crystalline network via complementary non-covalent interactions, in an aqueous environment. Subsequently, single-crystal-to-single-crystal transformation-directed thiol–ene click chemistry crosslinks terminal alkenes at the end of the oligoether arms using 1,2-ethanedithiol, covalently locking [c2]daisy chain linkages while preserving long-range order. This two-dimensional mechanically interlocked polymer can be exfoliated from its crystals to generate a multilayer counterpart exhibiting a 47-fold stiffness enhancement relative to its bulk parent. Moreover, the trilayer nanosheets preserve the structural integrity with the same hexagonal symmetry as the bulk parent. Our method enables the synthesis of a single-crystalline two-dimensional mechanically interlocked polymer from flexible monomers with precise synthetic control and unlocks the potential of developing mechanically interlocked materials.

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Fig. 1: Schematic representation of the formation of a 2D mechanically interlocked honeycomb network.
Fig. 2: The morphology and assembly process diagram of D1.
Fig. 3: Single-crystal X-ray (super)structures of D1.
Fig. 4: Synthesis and single-crystal X-ray (super)structures of D2.
Fig. 5: Mechanical property studies of exfoliated D2.
Fig. 6: Morphological studies for the exfoliated nanosheets of D2.

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Data availability

All data that support the findings of this study are available in the Article and Supplementary Information. Crystallographic data for the structures reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2300835 for D1 and CCDC 2300836 for D2. Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/. Source data are provided with this paper.

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Acknowledgements

We are grateful for financial support from the National Natural Science Foundation of China (22171232 and 21971211), the ‘Spearhead’ and ‘Leading Goose’ Research and Development Program of Zhejiang Province (2024SDXHDX0008), the Natural Science Foundation of Anhui Province (2108085MB31), the University Synergy Innovation Program of Anhui Province (GXXT-2021-064), the Excellent Research and Innovation Team Project of Anhui Province (2022AH010001) and Zhejiang Provincial Key Laboratory Construction Project. We extend our gratitude to Z. Chen and Z. Yang from the Instrumentation and Service Centers for Molecular Science and Physical Sciences, respectively at Westlake University for assistance with Raman and nanoindentation measurement as well as the data interpretation. The research was supported by Westlake University HPC Center. We also thank the staff at the SSRF BL17B1 beamline of the National Facility for Protein Science in Shanghai (NFPS), Shanghai Advanced Research Institute, CAS, for providing technical support with X-ray diffraction data collection and analysis.

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Author notes

  1. These authors contributed equally: Zheng-Bin Tang, Lifang Bian.

Authors and Affiliations

  1. Department of Chemistry, Zhejiang University, Hangzhou, China

    Zheng-Bin Tang

  2. Zhejiang Key Laboratory of Precise Synthesis of Functional Molecules, Department of Chemistry, School of Science, School of Engineering, Research Center for Industries of the Future, and Westlake Institute for Optoelectronics, Westlake University, and Westlake Institute for Advanced Study, Hangzhou, China

    Zheng-Bin Tang, Lifang Bian, Xiaohe Miao, Helei Gao, Lin Liu, Qike Jiang, Lijun Xu, Xiaorui Zheng & Zhichang Liu

  3. Institutes of Physical Science and Information Technology, Anhui University, Hefei, China

    Dengke Shen

  4. College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China

    Andrew C.-H. Sue

  5. International Institute for Sustainability with Knotted Chiral Meta Matter, Hiroshima University, Higashihiroshima, Japan

    Zhichang Liu

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Contributions

Z.L. conceived the idea. L.B., Z.-B.T. and Z.L. conducted experiments, analysed the results and prepared the Supplementary Information. X.M. and Z.-B.T. provided insightful discussions on X-ray diffraction measurement. Z.-B.T. and Z.L. wrote the manuscript. H.G. and L.X. carried out the HRESI-MS measurements. Z.-B.T. and H.G. performed the nanoindentation and Raman measurements. L.L. and X.Z. provided assistance with AFM measurements. Q.J. offered support with HRTEM measurement. D.S. and A.C.-H.S. discussed and revised the manuscript.

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Correspondence to Zhichang Liu.

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Nature Synthesis thanks the anonymous reviewers for their contribution to the peer review of this work. Primary Handling Editor: Alison Stoddart, in collaboration with the Nature Synthesis team.

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Supplementary information

Supplementary Information

Supplementary Scheme 1, Figs. 1–34, Tables 1 and 2, Refs. 1–8, Experimental details and X-ray crystallographic details.

Supplementary Data 1

Crystal data for D1, CCDC 2300835.

Supplementary Data 2

Crystal data for D2, CCDC 2300836.

Source data

Source Data Fig. 5

Height profiles and Young’s modulus of exfoliated D2 films.

Source Data Fig. 6

Height profiles of the exfoliated nanosheets of D2.

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Tang, ZB., Bian, L., Miao, X. et al. Synthesis of a crystalline two-dimensional [c2]daisy chain honeycomb network. Nat. Synth 4, 922–930 (2025). https://doi.org/10.1038/s44160-025-00791-x

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