Selectively dissolving CO2 in highly fluorinated non-porous crystalline materials

Vitórica-Yrezábal, Iñigo and McAnally, Craig and Fletcher, Ashleigh and Warren, Mark and Hill, Adrian and Thompson, Stephen and Quinn, Martin and Mottley, Sam and Mottley, Stephen and Brammer, Lee (2024) Selectively dissolving CO2 in highly fluorinated non-porous crystalline materials. Other. ChemRxiv. (https://doi.org/10.26434/chemrxiv-2024-sc3fd)

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Abstract

Separation of CO2 from gas mixtures is important is specific applications such as purification of CH4 gas and blue hy-drogen production and more generally in the separation and processing of greenhouse effect gases to mitigate the hazardous effects of global warming. Herein, we report the selective CO2 sorption by a family of isoreticular, flexible silver coordination polymers (AgCPs) that are ostensibly non-porous but exhibit latent porosity to CO2 above a gate pressure, through a mechanism akin to dissolution in fluoroalkanes. The CO2 sorption properties are rationally modified by changing the length of the perfluorocarboxylate ligands. The AgCPs show an absence of CH4 adsorption due to the lack of pores and channels in their structure and the failure of the dissolution mechanism due to alkane-perfluoroalkane immiscibility. In situ single-crystal and powder X-ray diffraction enable the direct visualization of the binding domains of adsorbed CO2 molecules as well as the associated structural changes of the AgCPs and confirming the gating of CO2 uptake. The deployment of perfluoroalkylcarboxylate ligands combined with the flexibility of the silver(I) coordination sphere to generate highly fluorinated but mobile regions of the crystals plays an integral role in the selective sorption of CO2 over CH4.

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