Abstract
sp2-carbon-linked covalent organic frameworks (sp2c-COFs) are crystalline porous polymers with repeat organic units linked by sp2 carbons, and have attracted increasing interest due to their robust skeleton and tunable semiconducting properties. Single-crystalline sp2c-COFs with well-defined structures can represent an ideal platform for investigating fundamental physics properties and device performance. However, the robust olefin bonds inhibit the reversible-reaction-based crystal self-correction, thus yielding polycrystalline or amorphous polymers. Here we report an imine-to-olefin transformation strategy to form single-crystal sp2c-COFs. The isolated single crystals display rectangular nanotube-like domains with sizes up to approximately 24 μm × 0.8 μm × 0.8 μm, and permanent pore distribution around 1.1 nm. The highly conjugated olefin linkage endows the crystals with enhanced electronic connectivity which determines a remarkable room-temperature metal-free ferromagnetism (8.6 × 10−3 emu g−1). Our protocol is robust and generally applicable for the synthesis of single-crystalline sp2c-COFs for future spin-electron devices.
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Data availability
The data supporting the findings of this study are available in the article and its Supplementary Information. Crystallographic data for the sc-COFs in this article have been deposited at the Cambridge Crystallographic Data Centre (CCDC) (CCDC 2340230 for sc-sp2c-COF-1, CCDC 2370333 for sc-sp2c-COF-2 and CCDC 2340227 for COF-303). Source data are provided with this paper.
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Acknowledgements
T.Z. acknowledges the National Natural Science Foundation of China (grant number 52322316), the Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang (grant number 2021R01005) and the Key Research and Development Program of Ningbo (2022ZDYF020023). Z.Z acknowledges the National Natural Science Foundation of China (grant number 22371146). S.X. and P.S. acknowledge financial support from the Interdisciplinary Thematic Institute SysChem via the IdEx Unistra (ANR-10-IDEX-0002) within the program Investissement d’Avenir program, the Foundation Jean-Marie Lehn and the Institut Universitaire de France (IUF). We thank W. Wang for valuable discussion.
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Contributions
T.Z. initiated the project. T.Z. and S.L. designed the experiments. S.L. performed the COF syntheses, chemical structure characterizations, crystal structure characterizations and magnetization experiments. E.L., T.W. and Z.Z performed the single-crystal analysis. H.Y. and J.H. performed the SEM characterization and schematic drawing. Y.Z. performed the 13C ssNMR experiments. T.Z., S.X., P.S., Q.X and S.L. wrote the paper.
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T.Z. and S.L. have applied for a patent for the imine-to-olefin transformation strategy (CN 202410295514.8). The other authors declare no competing interests.
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Supplementary Information
Supplementary Figs. 1–39 and Tables 1–6.
Supplementary Data 1
Crystallographic data for COF-303 (CCDC 2340227).
Supplementary Data 2
Crystallographic data for sc-sp2c-COF-1 (CCDC 2340230).
Supplementary Data 3
Crystallographic data for sc-sp2c-COF-2 (CCDC 2370333).
Source data
Source Data Fig. 1
Statistical source data for Fig. 1.
Source Data Fig. 2
Statistical source data for Fig. 2.
Source Data Fig. 3
Statistical source data for Fig. 3.
Source Data Fig. 4
Statistical source data for Fig. 4.
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Li, S., Xu, S., Lin, E. et al. Synthesis of single-crystalline sp2-carbon-linked covalent organic frameworks through imine-to-olefin transformation. Nat. Chem. 17, 226–232 (2025). https://doi.org/10.1038/s41557-024-01690-y
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DOI: https://doi.org/10.1038/s41557-024-01690-y
