Vibrational Modes and Terahertz Phenomena of the Large-CageZeolitic Imidazolate Framework-71 br

The zeolitic imidazole framework ZIF-71 has the potential to outperform otherwell-studied metal-organic frameworks due to its intrinsic hydrophobicity and relatively largepore size. However, a detailed description of its complex physical phenomena and structuraldynamics has been lacking thus far. Herein, we report the complete assignment of the vibrationalmodes of ZIF-71 using high-resolution inelastic neutron scattering measurements andsynchrotron radiation infrared spectroscopy, corroborated by density functional theory (DFT)calculations. With its 816 atoms per unit cell, ZIF-71 is the largest system yet for whichfrequency calculations have been accomplished employing the CRYSTAL17 DFT code. Wediscover low-energy terahertz dynamics such as gate-opening and shearing modes that arecentral to the functions and stability of the ZIF-71 framework structure. Nanoscale analyticalmethods based on atomic force microscopy (near-field infrared spectroscopy and AFMnanoindentation) further unravel the local chemical and mechanical properties of ZIF-71 singlecrystals.