Terahertz Signatures of the Methane Replacement Reaction in Hydroquinone Clathrates.

We report a comprehensive experimental and computational study into low-frequency vibrational dynamics of hydroquinone clathrate during gas loading, in order to monitor replacement of carbon dioxide with methane in its atomic-level pores. We used terahertz time-domain spectroscopy, because terahertz modes are highly sensitive to the identity and structure of enclathrated guest molecules. Through simulations, we determined that the replacement reaction is not completed.

Terahertz Spectroscopy Unambiguously Determines the Orientation of Guest Water Molecules in a Structurally Elusive Metal-Organic Framework.

Porous materials, particularly metal-organic frameworks (MOFs), hold great promise for advanced applications. MIL-53(Al) is an exceptionally well-studied MOF that exhibits a phase transition upon guest capture─in this case, water─resulting in a dramatic change in the pore volume. Despite extensive studies, the structure of the water-loaded narrow-pore phase, MIL-53(Al)-, remains controversial, particularly with respect to the positions of the adsorbed water molecules.