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An elastic metal–organic crystal with a densely catenated backbone


What particular mechanical properties can be expected for materials composed of interlocked backbones has been a long-standing issue in materials science since the first reports on polycatenane and polyrotaxane in the 1970s1,2,3. Here we report a three-dimensional porous metal–organic crystal, which is exceptional in that its warps and wefts are connected only by catenation. This porous crystal is composed of a tetragonal lattice and dynamically changes its geometry upon guest molecule release, uptake and exchange, and also upon temperature variation even in a low temperature range. We indented4 the crystal along its a/b axes and obtained the Young’s moduli of 1.77 ± 0.16 GPa in N,N-dimethylformamide and 1.63 ± 0.13 GPa in tetrahydrofuran, which are the lowest among those reported so far for porous metal–organic crystals5. To our surprise, hydrostatic compression showed that this elastic porous crystal was the most deformable along its c axis, where 5% contraction occurred without structural deterioration upon compression up to 0.88 GPa. The crystal structure obtained at 0.46 GPa showed that the catenated macrocycles move translationally upon contraction. We anticipate our mechanically interlocked molecule-based design to be a starting point for the development of porous materials with exotic mechanical properties. For example, squeezable porous crystals that may address an essential difficulty in realizing both high abilities of guest uptake and release are on the horizon.

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Fig. 1: Crystal structure of CTNMOF at 25 °C with a space group of P4122.
Fig. 2: Guest-responsive properties of CTNMOF.
Fig. 3: Temperature- and guest-dependent structural transformations of CTNMOF.
Fig. 4: Elastic properties of CTNMOF.

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A part of this work was conducted at the Advanced Characterization Nanotechnology Platform of the University of Tokyo, supported by ‘Nanotechnology Platform’ of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. We thank K. Okitsu and K. Fukawa for technical assistance with SCXRD and PXRD, respectively; D. Hamane for discussions on high-pressure experiments; T. Uemura, N. Hosono and H. Taketomi for help with thermogravimetry/mass spectrometry measurements; S. Suginome for help with NMR spectral measurements and J.-S. M. Lee and K. Morishita for discussion on preparing the manuscript. T.A. acknowledges the Japan Society for the Promotion of Science (JSPS) for a JSPS Grant-In-Aid for Scientific Research (S) (18H05260) on ‘Innovative Functional Materials based on Multi-Scale Interfacial Molecular Science’. This work was also supported by JST, PRESTO (grant number JPMJPR20A5), Japan. H.S. is grateful for JSPS KAKENHI grant numbers 17H05357 (Coordination Asymmetry), 18H04501 (Soft Crystal) and 20H02705 (Scientific Research (B)). W.M. acknowledges the receipt of a JSPS Postdoctoral Fellowship for Research in Japan and JSPS KAKENHI grant number 20K15251.

Author information




W.M., H.S. and T.A. conceived the project, designed experiments and directed the research. W.M. performed and interpreted all of the experiments associated with molecular synthesis, crystal growth and structural characterization. H.S. performed the sorption experiments. S.K., W.M. and Y.I. designed nanoindentation experiments. S.K., T.I. and W.M. conducted nanoindentation experiments. K.K., W.M. and H.S. performed high-pressure experiments. J.P. and Y.H. conducted the computational studies. All authors contributed to the writing and editing of the manuscript.

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Correspondence to Takuzo Aida or Hiroshi Sato.

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Meng, W., Kondo, S., Ito, T. et al. An elastic metal–organic crystal with a densely catenated backbone. Nature 598, 298–303 (2021).

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