In Situ Single-Crystal X-ray Diffraction Studies of Desorption and Sorption in a Flexible Nanoporous Molecular Framework Material

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Abstract
The subtle flexibility of the framework material Co(bpy)1.5(NO3)2·(guest) (bpy = 4,4‘-bipyridine) (1 · (guest)) is demonstrated quantitatively through in situ single-crystal X-ray diffraction measurements of guest desorption and sorption processes. Variable temperature unit cell determinations were employed to monitor the uptake and release of guest species, and full structural determinations have been carried out for the as-grown ethanol-loaded framework (1 · (EtOH)), for the empty host framework (1), and for each of the five introduced guests (methanol: 1 · (MeOH), acetone: 1 · (ACN), acetonitrile: 1 · (MeCN), tetrahydrofuran: 1 · (THF), dichloromethane: 1 · (DCM)). The framework consists of interdigitated two-dimensional bilayers of cobalt(II) centers bridged by bpy ligands, with one-dimensional pores that account for approximately 20% of the total volume. The sorption of guest species of varying size and shape has revealed the framework's ability to adapt to different guests through a range of different framework flexibilities.