Soft Hydrogen-Bonded Organic Frameworks Constructed Using a Flexible Organic Cage Hinge

Qiang Zhu, Lei Wei, Chengxi Zhao, Hang Qu, Bowen Liu, Thomas Fellowes, Siyuan Yang, Alexandra Longcake, Michael J. Hall, Michael R. Probert, Yingbo Zhao, Andrew I. Cooper*, Marc A. Little*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)
26 Downloads (Pure)


Soft porous crystals combine flexibility and porosity, allowing them to respond structurally to external physical and chemical environments. However, striking the right balance between flexibility and sufficient rigidity for porosity is challenging, particularly for molecular crystals formed by using weak intermolecular interactions. Here, we report a flexible oxygen-bridged prismatic organic cage molecule, Cage-6-COOH, which has three pillars that exhibit “hinge-like” rotational motion in the solid state. Cage-6-COOH can form a range of hydrogen-bonded organic frameworks (HOFs) where the “hinge” can accommodate a remarkable 67° dihedral angle range between neighboring units. This stems both from flexibility in the noncovalent hydrogen-bonding motifs in the HOFs and the molecular flexibility in the oxygen-linked cage hinge itself. The range of structures for Cage-6-COOH includes two topologically complex interpenetrated HOFs, CageHOF-2α and CageHOF-2β. CageHOF-2α is nonporous, while CageHOF-2β has permanent porosity and a surface area of 458 m2 g–1. The flexibility of Cage-6-COOH allows this molecule to rapidly transform from a low-crystallinity solid into the two crystalline interpenetrated HOFs, CageHOF-2α and CageHOF-2β, under mild conditions simply by using acetonitrile or ethanol vapor, respectively. This self-healing behavior was selective, with the CageHOF-2β structure exhibiting structural memory behavior.
Original languageEnglish
Pages (from-to)23352–23360
Number of pages9
JournalJournal of the American Chemical Society
Issue number42
Early online date12 Oct 2023
Publication statusPublished - 25 Oct 2023


  • porous materials
  • materials chemistry
  • X-ray crystallography
  • flexible materials
  • computational modelling
  • in-situ diffraction
  • vapour sorption
  • automation
  • gas sorption

ASJC Scopus subject areas

  • Materials Chemistry


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