Unconventional mechanical and thermal behaviours of MOF CALF-20

D Fan and S Naskar and G Maurin, NATURE COMMUNICATIONS, 15, 3251 (2024).

DOI: 10.1038/s41467-024-47695-6

CALF-20 was recently identified as a benchmark sorbent for CO2 capture at the industrial scale, however comprehensive atomistic insight into its mechanical/thermal properties under working conditions is still lacking. In this study, we developed a general-purpose machine-learned potential (MLP) for the CALF-20 MOF framework that predicts the thermodynamic and mechanical properties of the structure at finite temperatures within first-principles accuracy. Interestingly, CALF-20 was demonstrated to exhibit both negative area compression and negative thermal expansion. Most strikingly, upon application of the tensile strain along the 001 direction, CALF-20 was shown to display a distinct two-step elastic deformation behaviour, unlike typical MOFs that undergo plastic deformation after elasticity. Furthermore, this MOF was shown to exhibit a fracture strain of up to 27% along the 001 direction at room temperature comparable to that of MOF glasses. These abnormal thermal and mechanical properties make CALF-20 as attractive material for flexible and stretchable electronics and sensors. CALF-20 MOF is considered a benchmark sorbent for industrial scale CO2 capture. Here authors use machine-learning potential simulations to show that CALF-20 exhibits anomalous structural responses to temperature and strain stimuli, with potential applications in mechanical/thermal sensing.

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