A research group led by Distinguished Professor Susumu Kitagawa, Assistant Professor Ken-ichi Otake and Postdoctoral Researcher Yifan Gu (currently Professor at Tongji University, China) of the Institute for Integrated Cell-Material Sciences (iCeMS) at Kyoto University, in collaboration with a research group at Tongji University, has successfully developed a flexible porous material that opens gates and adsorbs only CO2 among various gas molecules. The research was published in Nature Communications.
A flexible porous coordination polymer/metal-organic framework (PCP/MOF) is a crystalline porous material composed of organic molecules and metal ions that are regularly arranged to form numerous small pores. Notably, Kitagawa Laboratory was the first in the world to develop flexible PCP/MOFs, which can flexibly change their structure in response to gas adsorption. However, gas separation using gate-opening behavior is limited by the fact that gases other than the target gas molecules are likely to be co-adsorbed. The research group synthesized a new flexible PCP/MOF using cobalt ions, di(4-pyridyl)glycol, and pyridinedicarboxylic acid.
This flexible PCP/MOF has an interdigitated 2D sheet-layer structure in which two-dimensional sheets composed of cobalt ions and carboxylic acid ions linked by these ions are alternatively displaced. Observation of the pores of this interdigitated structure revealed that the pockets serving as gas adsorption sites are separated from each other prior to gas adsorption, resulting in a corrugated porous structure. In such an interdigitated structure, only gases with adsorption energies exceeding the interactions between the sheets exhibit adsorption behavior. However, if their barrier energy for passing through the channels is sufficiently high, the gas molecules cannot pass through the channels and adsorption is prevented.
The combined action of these mechanisms demonstrated, for the first time, that only CO2 can be separated among nine similar gases, including N2, CH4, CO, O2, H2, Ar, C2H2, C2H4, and C2H6. The clarification of the mechanism and design guidelines for the selective adsorption of CO2, both of which were previously unexplored, is expected to lead to the development of various materials with similar properties and their application in addressing challenging problems such as the separation and purification of various gases.
Journal Information
Publication: Nature Communications
Title: Soft corrugated channel with synergistic exclusive discrimination gating for CO2 recognition in gas mixture
DOI: 10.1038/s41467-023-39470-w
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