High-throughput gas separation by flexible metal-organic frameworks with fast gating and thermal management capabilities

Shotaro Hiraide; Yuta Sakanaka; Hiroshi Kajiro; Shogo Kawaguchi; Minoru T Miyahara; Hideki Tanaka

doi:10.1038/s41467-020-17625-3

High-throughput gas separation by flexible metal-organic frameworks with fast gating and thermal management capabilities

Nat Commun. 2020 Aug 3;11(1):3867. doi: 10.1038/s41467-020-17625-3.

Authors

Shotaro Hiraide¹, Yuta Sakanaka¹, Hiroshi Kajiro², Shogo Kawaguchi³, Minoru T Miyahara⁴, Hideki Tanaka⁵

Affiliations

¹ Department of Chemical Engineering, Kyoto University, Nishikyo, Kyoto, 615-8510, Japan.
² Nippon Steel Corporation, 20-1 Shintomi, Futtsu, Chiba, 293-8511, Japan.
³ Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, 1-1-1 Kouto, Sayo, Hyogo, 679-5198, Japan.
⁴ Department of Chemical Engineering, Kyoto University, Nishikyo, Kyoto, 615-8510, Japan. miyahara@cheme.kyoto-u.ac.jp.
⁵ Research Initiative for Supra-Materials (RISM), Shinshu University, 4-17-1 Wakasato, Nagano, 380-8553, Japan. htanaka@shinshu-u.ac.jp.

Abstract

Establishing new energy-saving systems for gas separation using porous materials is indispensable for ensuring a sustainable future. Herein, we show that ELM-11 ([Cu(BF₄)₂(4,4'-bipyridine)₂]_n), a member of flexible metal-organic frameworks (MOFs), exhibits rapid responsiveness to a gas feed and an 'intrinsic thermal management' capability originating from a structural deformation upon gas adsorption (gate-opening). These two characteristics are suitable for developing a pressure vacuum swing adsorption (PVSA) system with rapid operations. A combined experimental and theoretical study reveals that ELM-11 enables the high-throughput separation of CO₂ from a CO₂/CH₄ gas mixture through adiabatic operations, which are extreme conditions in rapid pressure vacuum swing adsorption. We also propose an operational solution to the 'slipping-off' problem, which is that the flexible MOFs cannot adsorb target molecules when the partial pressure of the target gas decreases below the gate-opening pressure. Furthermore, the superiority of our proposed system over conventional systems is demonstrated.