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.