Developing porous, O2-selective adsorbents capable of extracting high-purity oxygen from air remains a significant challenge. We seek to address this challenge through the synthesis and tuning of redox-active metal–organic frameworks, with special focus on examining structure-property relationships that can inform their improvement. I will present our latest results in which we show that chemically reduced iron-pyrazolate metal–organic frameworks are capable of strong and selective adsorption of O2 over N2 at ambient (25 °C) or even elevated (200 °C) temperature, despite featuring coordinatively saturated iron centers. Through a suite of gas adsorption measurements, single-crystal X-ray diffraction, and numerous spectroscopic probes, we explore the mechanism of O2 adsorption in the one-dimensional triangular pores of these frameworks. We demonstrate that selective O2 uptake likely occurs as a result of outer-sphere electron transfer from the framework to form superoxide species, which are subsequently stabilized by intercalated alkali metal cations. The chemical reduction of a robust metal–organic framework to render it capable of binding O2 through an outer-sphere electron transfer mechanism thus represents an attractive and underexplored strategy for the design of next-generation O2 adsorbents.

Selective, high-temperature O2 adsorption in chemically reduced, redox-active iron-pyrazolate metal–organic frameworks

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.