Selective Adsorption of Oxygen from Humid Air in a Metal-Organic Framework with Trigonal Pyramidal Copper(I) Sites

Kurtis M Carsch; Adrian J Huang; Matthew N Dods; Surya T Parker; Rachel C Rohde; Henry Z H Jiang; Yuto Yabuuchi; Sarah L Karstens; Hyunchul Kwon; Romit Chakraborty; Karen C Bustillo; Katie R Meihaus; Hiroyasu Furukawa; Andrew M Minor; Martin Head-Gordon; Jeffrey R Long

doi:10.1021/jacs.3c10753

Selective Adsorption of Oxygen from Humid Air in a Metal-Organic Framework with Trigonal Pyramidal Copper(I) Sites

J Am Chem Soc. 2024 Feb 7;146(5):3160-3170. doi: 10.1021/jacs.3c10753. Epub 2024 Jan 26.

Authors

Kurtis M Carsch^{1

2}, Adrian J Huang^{1

2}, Matthew N Dods^{1

3}, Surya T Parker³, Rachel C Rohde^{1

2}, Henry Z H Jiang^{1

2

4}, Yuto Yabuuchi^{1

2

4}, Sarah L Karstens^{1

2}, Hyunchul Kwon^{1

2}, Romit Chakraborty^{2

4}, Karen C Bustillo⁵, Katie R Meihaus^{1

2}, Hiroyasu Furukawa^{1

2

4}, Andrew M Minor^{5

6}, Martin Head-Gordon^{1

2

4}, Jeffrey R Long^{1

2

3

4}

Affiliations

¹ Institute for Decarbonization Materials, University of California, Berkeley, Berkeley, California 94720, United States.
² Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.
³ Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, California 94720, United States.
⁴ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
⁵ National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
⁶ Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, California 94720, United States.

Abstract

High or enriched-purity O₂ is used in numerous industries and is predominantly produced from the cryogenic distillation of air, an extremely capital- and energy-intensive process. There is significant interest in the development of new approaches for O₂-selective air separations, including the use of metal-organic frameworks featuring coordinatively unsaturated metal sites that can selectively bind O₂ over N₂ via electron transfer. However, most of these materials exhibit appreciable and/or reversible O₂ uptake only at low temperatures, and their open metal sites are also potential strong binding sites for the water present in air. Here, we study the framework Cu^I-MFU-4l (Cu_xZn_5-xCl_4-x(btdd)₃; H₂btdd = bis(1H-1,2,3-triazolo[4,5-b],[4',5'-i])dibenzo[1,4]dioxin), which binds O₂ reversibly at ambient temperature. We develop an optimized synthesis for the material to access a high density of trigonal pyramidal Cu^I sites, and we show that this material reversibly captures O₂ from air at 25 °C, even in the presence of water. When exposed to air up to 100% relative humidity, Cu^I-MFU-4l retains a constant O₂ capacity over the course of repeated cycling under dynamic breakthrough conditions. While this material simultaneously adsorbs N₂, differences in O₂ and N₂ desorption kinetics allow for the isolation of high-purity O₂ (>99%) under relatively mild regeneration conditions. Spectroscopic, magnetic, and computational analyses reveal that O₂ binds to the copper(I) sites to form copper(II)-superoxide moieties that exhibit temperature-dependent side-on and end-on binding modes. Overall, these results suggest that Cu^I-MFU-4l is a promising material for the separation of O₂ from ambient air, even without dehumidification.