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

Lookup NU author(s): Alexandra Longcake, Dr Michael HallORCiD, Professor Mike ProbertORCiD



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


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.

Publication metadata

Author(s): Zhu Q, Wei L, Zhao C, Qu H, Liu B, Fellowes T, Yang S, Longcake A, Hall MJ, Probert MR, Zhao Y, Cooper AI, Little MA

Publication type: Article

Publication status: Published

Journal: Journal of the American Chemical Society

Year: 2023

Volume: 145

Issue: 42

Pages: 23352-23360

Print publication date: 25/10/2023

Online publication date: 12/10/2023

Acceptance date: 12/10/2023

Date deposited: 27/10/2023

ISSN (print): 0002-7863

ISSN (electronic): 1520-5126

Publisher: American Chemical Society


DOI: 10.1021/jacs.3c09246


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