Adsorbents able to uptake large amounts of gases within a narrow range of pressure, i.e., phase-change adsorbents, are emerging as highly interesting systems to achieve excellent gas separation performances with little energy input for regeneration. A recently discovered metal-organic framework based on CeIV and tetrafluoroterephthalate, dubbed F4_MIL-140A(Ce), displays a step-shaped CO2 adsorption isotherm, reaching saturation in conditions of temperature and pressure compatible with real life application in post-combustion carbon capture. Here, we combine data obtained from a wide pool of characterisation techniques – namely gas sorption analysis, in situ infrared spectroscopy, in situ powder X-ray diffraction, in situ X-ray absorption spectroscopy, multinuclear solid state nuclear magnetic resonance spectroscopy and adsorption microcalorimetry - with periodic density functional theory simulations, to provide evidence for the existence of a cooperative CO2 adsorption mechanism that involves concerted rotation of perfluorinated aromatic rings and interaction with open metal sites.
Detailed experimental procedures. Additional figures, tables and discussion.
Adsorption isotherms in .aif format