The crystallographic characterization of framework–guest interactions in metal–organic frameworks enables the location of guest binding sites and provides meaningful information on the nature of these interactions, allowing the correlation of structure with adsorption behavior. Herein, techniques developed for in situ single-crystal X-ray diffraction experiments on porous crystals have enabled the direct observation of CO2 adsorption in the open metal site of Fe3-xMxO clusters (X=0, 1, 2) in PCN-250. PCN-250 is a metal–organic framework that can possess trivalent and bivalent metals in the cluster.1 The single crystal samples were characterized before and after activation in N2 at 423 K and after CO2 adsorption. Interestingly, the CO2 binding is stronger to the bivalent metals than to the trivalent metals, indicating orbital interaction plays a bigger role in the gas-open metal site interaction than the static electric force. To the best of our knowledge, this work is the first single-crystal structure determination of a trivalent metal–CO2 interaction and the first crystallographically characterized open metal site for trivalent metals.

Probing open metal sites in high valence metal-organic frameworks by in-situ single crystal X-ray diffraction

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.