Quantum Mechanical Interpretation of the Ultra-Low Energy Methyl-Rotation Dynamics in Porous Metal-Organic Frameworks Probed by Low-Frequency Vibrational Spectroscopy and ab initio Simulations

19 March 2018, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Understanding the nature of the interatomic interactions present within the pores of metal-organic frameworks
is critical in order to design and utilize advanced materials
with desirable applications. In ZIF-8 and its cobalt analogue
ZIF-67, the imidazolate methyl-groups, which point directly
into the void space, have been shown to freely rotate - even
down to cryogenic temperatures. Using a combination of ex-
perimental terahertz time-domain spectroscopy, low-frequency
Raman spectroscopy, and state-of-the-art ab initio simulations,
the methyl-rotor dynamics in ZIF-8 and ZIF-67 are fully charac-
terized within the context of a quantum-mechanical hindered-
rotor model. The results lend insight into the fundamental
origins of the experimentally observed methyl-rotor dynamics,
and provide valuable insight into the nature of the weak inter-
actions present within this important class of materials.


Density functional theory
Metal-organic frameworks
Low-frequency vibrational spectroscopy


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