Negative cooperativity upon hydrogen bond-stabilized O2 adsorption in a redox-active metal–organic framework
Julia Oktawiec, Henry Z. H. Jiang, Jenny G. Vitillo, Douglas A. Reed, Lucy E. Darago, Benjamin A. Trump, Varinia Bernales, Harriet Li, Kristen A. Colwell, Hiroyasu Furukawa, Craig M. Brown, Laura Gagliardi, Jeffrey R. Long
Abstract
Abstract The design of stable adsorbents capable of selectively capturing dioxygen with a high reversible capacity is a crucial goal in functional materials development. Drawing inspiration from biological O 2 carriers, we demonstrate that coupling metal-based electron transfer with secondary coordination sphere effects in the metal–organic framework Co 2 (OH) 2 (bbta) (H 2 bbta = 1 H ,5 H -benzo(1,2- d: 4,5- d ′)bistriazole) leads to strong and reversible adsorption of O 2 . In particular, moderate-strength hydrogen bonding stabilizes a cobalt(III)-superoxo species formed upon O 2 adsorption. Notably, O 2 -binding in this material weakens as a function of loading, as a result of negative cooperativity arising from electronic effects within the extended framework lattice. This unprecedented behavior extends the tunable properties that can be used to design metal–organic frameworks for adsorption-based applications.