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Unravelling Terahertz Vibrations in Metal - Organic Frameworks (MOFs)

Unravelling Terahertz Vibrations in Metal-Organic Frameworks (MOFs) [2014]



Metal-organic frameworks (MOFs) are a promising new class of next-generation materials. With nanoscale cage-like structures featuring exceedingly large internal surface areas, MOFs can be used to capture and store molecules, giving them a wide range of potential applications from gas storage and capturing CO2 to microelectronics, drug encapsulation and use in sensors. In order to turn potential into reality, it’s necessary to understand their physical structure at a fundamental level, and how this determines their properties on the macroscopic scale. In our recent PRL paper, we used a combination of inelastic neutron scattering and synchrotron radiation far-infrared absorption spectroscopy, in conjunction with density functional theory (DFT), to examine low-frequency terahertz (THz) vibrations in three prototypal ZIF materials (an important subset of MOFs). Using this combination of techniques, the team discovered that such vibrations are intrinsically linked to observed physical phenomena in the ZIFs. For example pore breathing, where the cage structure opens and closes, and gate opening, where the material undergoes a step change in the amount of molecules it is able to capture, can be linked back to THz vibrational modes and the underpinning collective lattice dynamics.