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Anionic silicate organic frameworks constructed from hexacoordinate silicon centres

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Crystalline frameworks composed of hexacoordinate silicon species have thus far only been observed in a few high pressure silicate phases. By implementing reversible Si–O chemistry for the crystallization of covalent organic frameworks, we demonstrate the simple one-pot synthesis of silicate organic frameworks based on octahedral dianionic SiO6 building units. Clear evidence of the hexacoordinate environment around the silicon atoms is given by 29Si nuclear magnetic resonance analysis. Characterization by high-resolution powder X-ray diffraction, density functional theory calculation and analysis of the pair-distribution function showed that those anionic frameworks—M2[Si(C16H10O4)1.5], where M = Li, Na, K and C16H10O4 is 9,10-dimethylanthracene-2,3,6,7-tetraolate—crystallize as two-dimensional hexagonal layers stabilized in a fully eclipsed stacking arrangement with pronounced disorder in the stacking direction. Permanent microporosity with high surface area (up to 1,276 m2 g−1) was evidenced by gas-sorption measurements. The negatively charged backbone balanced with extra-framework cations and the permanent microporosity are characteristics that are shared with zeolites.

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Figure 1: Synthesis of anionic silicate organic framework by reversible Si–O chemistry.
Figure 2: Physical characterization of the hexacoordinate state of silicon within the network and of the crystallinity of SiCOF.
Figure 3: Gas sorption analysis shows the high permanent microporosity of SiCOF upon guest removal.

Change history

  • 09 May 2017

    In the version of this Article originally published, the space group was incorrectly formatted in the third paragraph of page 4, and in the caption of Figure 2. Furthermore, the first sentence of the main text contained typographical errors and has been corrected to read: "In silicate materials, silicon sites almost exclusively adopt a tetrahedral coordination with respect to oxygen and reports of silicon containing hypercoordinate, that is, penta- or hexacoordinate silicon are very rare." Finally, the crystallographic data for the silicate organic framework was not present in the Supplementary Information when this Article was pushed live. These corrections have been made in all versions of the Article.


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We thank the European Research Council (ERC) for financial support within the project ORGZEO (Grant Number:278593). Support from the German Science Foundation within the Cluster of Excellence UniCat-Unifying concepts in catalysis is further acknowledged. M.J.B. thanks the Czech Science Foundation (GA CR) for junior grant funding (CAMs: 16-21151Y) and the European Research Council (ERC) for funding under the Starting Grant scheme (BEGMAT: 678462). M.J.B. further acknowledges the Charles University Centre of Advanced Materials (CUCAM) (OP VVV Excellent Research Teams, project number CZ.02.1.01/0.0/0.0/15_003/0000417). We thank Professor Holger Dobbek for his precious help, Professor Matthias Driess and Dr Matthias Thommes for fruitful discussions, and Mrs. Christina Eichenauer, Mrs. Maria Unterweger and Mr. Matthias Trunk for their assistance.

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Authors and Affiliations



J.R. and A.Th. conceived and designed the experiments. J.R. performed the experiments and carried out the structural characterizations. P.F. and A.Tr. carried out the DFT calculations. D.P. and M.U.S. performed the analysis of the pair-distribution function. A.N.F. collected the synchrotron X-ray diffraction data. M.J.B. refined the high-resolution PXRD data. All the authors interpreted the structures and contributed to the preparation of the manuscript.

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Correspondence to Jérôme Roeser or Arne Thomas.

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The authors declare no competing financial interests.

Supplementary information

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Crystallographic data generated for the SiCOF material (CIF 1 kb)

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Roeser, J., Prill, D., Bojdys, M. et al. Anionic silicate organic frameworks constructed from hexacoordinate silicon centres. Nature Chem 9, 977–982 (2017).

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