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Selective incarceration of caesium ions by Venus flytrap action of a flexible framework sulfide


The selective capture of Cs+ from solution is relevant to the remediation of nuclear waste and remains a significant challenge. Here we describe a new framework composed of [(CH3)2NH2]+ and [Ga2Sb2S7]2− layers, which are perforated with holes. Shape selectivity couples with framework flexibility, allowing the compound to respond to the ion-exchange process. The size, shape and flexibility of the holes allow Cs+ ions in an aqueous solution to selectively pass through and enter the material via an ion-exchange process. Following capture, the structure dynamically closes its holes in a manner reminiscent of a Venus flytrap, which prevents the Cs+ ions from leaching out. This process has useful implications in the separation science of Cs as it relates to the clean-up of nuclear waste. The dynamic response we describe here provides important insights for designing new materials for the selective removal of difficult-to-capture ions.

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Figure 1: Structure of [(CH3)2NH2]2Ga2Sb2S7·H2O (I).
Figure 2: X-ray diffraction of ion-exchanged compound I.
Figure 3: The unit cell of Cs2Ga2Sb2S7 (II) obtained by complete ion exchange of the original dimethylammonium cations in I.
Figure 4: The comparison of the relative cation sites in between the layers of compounds I and II.


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This research was supported by National Science Foundation (DMR-0801855). This work made use of the ICP-OES (supported by National Science Foundation) at the Integrated Molecular Structure Education and Research Center (IMSERC) at Northwestern University. 

Author information




N.D. and M.G.K. conceived and designed the experiments, N.D. performed the experiments, N.D. and M.G.K. analysed the data and co-wrote the paper.

Corresponding author

Correspondence to Mercouri G. Kanatzidis.

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The authors declare no competing financial interests.

Supplementary information

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Supplementary information (PDF 296 kb)

Supplementary information

Crystallographic data for compound I (CIF 11 kb)

Supplementary information

Crystallographic data for compound II (CIF 19 kb)

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Ding, N., Kanatzidis, M. Selective incarceration of caesium ions by Venus flytrap action of a flexible framework sulfide. Nature Chem 2, 187–191 (2010).

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