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Constructing ambivalent imidazopyridinium-linked covalent organic frameworks

Nature Synthesis volume 1, pages 382–392 (2022)Cite this article

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Abstract

Covalent organic frameworks (COFs) are dynamic covalent porous organic materials synthesized from molecular organic building blocks. However, the chemical linkages used to construct COFs are limited by the dynamic bond formation needed to ensure crystallinity. Thus, there is a continual search for new, chemically stable linkages that tailor both the chemical properties and topologies of COFs. As opposed to electrophilic linkages used to construct COFs, nucleophilic linkages that can react with electron-deficient species are rare. Here we report the synthesis of picolinaldehyde-derived imine-linked COFs that can be transformed into imidazopyridinium-linked COFs (IP-COFs) with a Lieb-like lattice. IP-COFs serve as precursors to ambivalent N-heterocyclic carbenes that can dissociate disulfide bonds to form carbon–sulfur bonds. IP-COFs exhibit a vastly improved sulfur redox chemistry when used as cathode materials in lithium–sulfur batteries, as they achieve a rate performance of 540 mAh g−1 (10 C) and a high areal capacity of 6.2 mAh cm−2 with a high sulfur loading of 9 mg cm−2 and a low electrolyte-to-sulfur ratio of 6 µl mg−1. In addition, the ionicity of the linkages enables the cleavage of IP-COFs into highly crystalline flakes with well-defined fringes, as resolved by atomic force microscopy and transmission electron microscopy.

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Fig. 1: Design and construction of chemically ambivalent COFs.
Fig. 2: Synthesis of IP-COF-1 and IP-COF-2.
Fig. 3: Characterizations of Im-COF-1 and IP-COF-1.
Fig. 4: Microscopic structure characterization of IP-COFs by cryo-TEM.
Fig. 5: AFM study of IP-COF-1.
Fig. 6: Sulfur-reactive IP-COFs.
Fig. 7: Promoting sulfur redox chemistry via IP-COFs.
Fig. 8: Performance of Li-S batteries.

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Data availability

Crystallographic data for the structures reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2132342 (IP-model-1) and 2150060 (IP-model-2). 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. All other data supporting the findings of this study are available within the paper and its Supplementary Information. Data are also available from the corresponding author upon reasonable request.

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Acknowledgements

K.P.L. acknowledges the NRF-CRP grant ‘Two-Dimensional Covalent Organic Framework: Synthesis and Applications,’ grant no. NRF-CRP16-2015-02, funded by the National Research Foundation, Prime Minister’s Office, Singapore. U.M. acknowledges support from the Singapore Ministry of Education, grant no. MOE-MOET2EP10120-0004. J.L. acknowledges support from the National Natural Science Foundation of China (grant no. 11974156), the Guangdong International Science Collaboration Project (grant no. 2019A050510001), the Guangdong Innovative and Entrepreneurial Research Team Program (grant no. 2019ZT08C044), the Shenzhen Science and Technology Program (no. KQTD20190929173815000 and no. 20200925161102001), the Science, Technology and Innovation Commission of Shenzhen Municipality (no. ZDSYS20190902092905285). The TEM/scanning transmission electron microscopy characterization was performed at the Cryo-EM Center and Pico Center from SUSTech Core Research Facilities that receives support from the Presidential Fund and Development and Reform Commission of Shenzhen Municipality. We thank S. Garaj (National University of Singapore) for kindly allowing access to the Asylum Cypher ES AFM.

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Author notes

  1. These authors contributed equally: Xing Li, Kun Zhang.

Authors and Affiliations

  1. Department of Chemistry, National University of Singapore, Singapore, Singapore

    Xing Li, Kun Zhang, Yijia Yuan, Gaolei Zhan, Walter P. D. Wong, Fangzheng Chen, Hai-Sen Xu & Kian Ping Loh

  2. Department of Physics and Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen, China

    Gang Wang & Junhao Lin

  3. Department of Physics, National University of Singapore, Singapore, Singapore

    Tanmay Ghosh & Utkur Mirsaidov

  4. Centre for BioImaging Sciences, Department of Biological Sciences, National University of Singapore, Singapore, Singapore

    Tanmay Ghosh & Utkur Mirsaidov

  5. State Key Laboratory of Solidification Processing, Center for Nano Energy Materials, Northwestern Polytechnical University and Shaanxi Joint Laboratory of Graphene (NPU), Xi’an, P. R. China

    Keyu Xie

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Contributions

Under the supervision of K.P.L., X.L. conceived the project and designed the experiments. X.L. conducted the experiments and analysed the data. K.Z. performed the battery tests and analysed the results. G.W. measured the high-resolution TEM of the COFs under the supervision of J.L. Y.Y. helped to synthesize the COF building units, confirm the melting point and grow the single crystals of the COF model compounds. G.Z. performed the AFM measurements. T.G. measured the TEM images of COFs under the supervision of U.M. W.P.D.W. collected and resolved the single crystal data of the COF model compound. X.L. discussed the project with F.C. and H.-S.X. K.X. provided the battery testing platform during the revision of the manuscript. X.L. and K.P.L. co-wrote the manuscript.

Corresponding authors

Correspondence to Junhao Lin or Kian Ping Loh.

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

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Supplementary information

Supplementary Information

experimental details, Figs. 1–50 and Tables 1–5.

Supplementary Data 1

X-ray crystallographic data of IP-model-1.

Supplementary Data 2

X-ray crystallographic data of IP-model-2.

Source data

Source Data Fig. 3b

Solid-state UV-vis absorption of Im-COF-1 and IP-COF-1.

Source Data Fig. 3c

N2 sorption results for Im-COF-1 and IP-COF-1.

Source Data Fig. 5c

AFM profiles of IP-COF-1.

Source Data Fig. 8

Performance of Li-S batteries including battery cycling and rate capability.

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Li, X., Zhang, K., Wang, G. et al. Constructing ambivalent imidazopyridinium-linked covalent organic frameworks. Nat. Synth 1, 382–392 (2022). https://doi.org/10.1038/s44160-022-00071-y

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