Cooperative CO 2 adsorption mechanism in a perfluorinated Ce IV -based metal organic framework

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2023-03, Vol.11 (11), p.5568-5583
• Main Authors: Cavallo, Margherita, Atzori, Cesare, Signorile, Matteo, Costantino, Ferdinando, Venturi, Diletta Morelli, Koutsianos, Athanasios, Lomachenko, Kirill A, Calucci, Lucia, Martini, Francesca, Giovanelli, Andrea, Geppi, Marco, Crocellà, Valentina, Taddei, Marco
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/D2TA09746J

Adsorbents able to uptake large amounts of gases within a narrow range of pressure, , phase-change adsorbents, are emerging as highly interesting systems to achieve excellent gas separation performances with little energy input for regeneration. A recently discovered phase-change metal-organic framework (MOF) adsorbent is F4_MIL-140A(Ce), based on Ce and tetrafluoroterephthalate. This MOF displays a non-hysteretic step-shaped CO adsorption isotherm, reaching saturation in conditions of temperature and pressure compatible with real life application in post-combustion carbon capture, biogas upgrading and acetylene purification. Such peculiar behaviour is responsible for the exceptional CO /N selectivity and reverse CO /C H selectivity of F4_MIL-140A(Ce). Here, we combine data obtained from a wide pool of characterisation techniques - namely gas sorption analysis, infrared spectroscopy, powder X-ray diffraction, 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 unique cooperative CO adsorption mechanism in F4_MIL-140A(Ce). Such mechanism involves the concerted rotation of perfluorinated aromatic rings when a threshold partial pressure of CO is reached, opening the gate towards an adsorption site where CO interacts with both open metal sites and the fluorine atoms of the linker.