Noncryogenic Air Separation using Aluminum Formate Al(HCOO)3 (ALF)

Published

May 3, 2023

Author(s)

Dinesh Mullangi, Hayden Evans, Taner N. Yildirim, Yuxiang Wang, Zeyu Deng, Zhaoqiang Zhang, Thuc Mai, Fengxia Wei, John Wang, Angela R. Hight Walker, Craig Brown, Dan Zhao, Pieremanuele Canepa, Anthony K. Cheetham

Abstract

Separating oxygen from air to create oxygen-enriched gas streams is a process that is significant in both industrial and medical fields. However, the prominent technologies for creating oxygen-enriched gas streams are both energy and infrastructure intensive as they use cryogenic temperatures or materials that adsorb N₂ from air. The latter method is less efficient than methods that adsorb O₂ directly. Herein we show, via a combination of gas adsorption isotherms, gas breakthrough experiments, neutron and synchrotron X-ray powder diffraction, Raman spectroscopy, and computational studies, that the metal-organic framework, Al(HCOO)₃ (ALF), which is easily prepared at low-cost from commodity chemicals, exhibits substantial O₂ adsorption and excellent time-dependent O₂/N₂ selectivity in the range of 50 – 125 near dry ice/solvent (≈ 190 K) temperatures. The O₂ adsorption with ALF at ≈ 190 K and ≈ 0.21 bar (the partial pressure of O₂ in air) is ≈ 1.7 mmol/g, and at ice/salt temperatures (≈ 250 K), is ≈ 0.3 mmol/g. Though the kinetics for full adsorption of O₂ near 190 K are slower than at temperatures nearer 250 K, the kinetics for initial O₂ adsorption are fast, suggesting that O₂ separation using ALF with rapid temperature swings at ambient pressures is a potentially viable choice for low-cost air separation applications. We also present synthetic strategies for improving the kinetics of this family of compounds, namely via Al/Fe solid solutions. To the best of our knowledge, ALF has the highest O₂/N₂ sorption selectivity verified by coadsorption experiments among MOF adsorbents without open metal sites.

Citation

Journal of the American Chemical Society

Volume

145

Issue

17

Pub Type

Journals

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DOI Link

Keywords

Air separation, Metal-organic frameworks, Perovskites, Gas separations, ReO3-type structures

Citation

Mullangi, D. , Evans, H. , Yildirim, T. , Wang, Y. , Deng, Z. , Zhang, Z. , Mai, T. , Wei, F. , Wang, J. , Hight Walker, A. , Brown, C. , Zhao, D. , Canepa, P. and Cheetham, A. (2023), Noncryogenic Air Separation using Aluminum Formate Al(HCOO)₃ (ALF), Journal of the American Chemical Society, [online], https://dx.doi.org/10.1021/jacs.3c02100 (Accessed December 4, 2024)