Gas adsorption and framework flexibility of CALF-20 explored via experiments and simulations
Rama Oktavian, Ruben Goeminne, Lawson T. Glasby, Ping Song, Racheal P. S. Huynh, Omid T. Qazvini, Omid Ghaffari Nik, Nima Masoumifard, Joan Cordiner, Pierre Hovington, Véronique Van Speybroeck, Peyman Z. Moghadam
Abstract
Abstract In 2021, Svante, in collaboration with BASF, reported successful scale up of CALF-20 production, a stable MOF with high capacity for post-combustion CO 2 capture which exhibits remarkable stability towards water. CALF-20’s success story in the MOF commercialisation space provides new thinking about appropriate structural and adsorptive metrics important for CO 2 capture. Here, we combine atomistic-level simulations with experiments to study adsorptive properties of CALF-20 and shed light on its flexible crystal structure. We compare measured and predicted CO 2 and water adsorption isotherms and explain the role of water-framework interactions and hydrogen bonding networks in CALF-20’s hydrophobic behaviour. Furthermore, regular and enhanced sampling molecular dynamics simulations are performed with both density-functional theory (DFT) and machine learning potentials (MLPs) trained to DFT energies and forces. From these simulations, the effects of adsorption-induced flexibility in CALF-20 are uncovered. We envisage this work would encourage development of other MOF materials useful for CO 2 capture applications in humid conditions.