Date/Time: 04-23-2019 - Tuesday - 05:00 PM - 07:00 PM
Stefan Kaskel1 2

1, Fraunhofer IWS, Dresden, , Germany
2, TU Dresden, Dresden, , Germany

Metal-Organic Frameworks with surface areas exceeding 5000 m2/g are promising materials for gas storage and sensing applications. Ultrahigh porosity gives rise to new counterintuitive phenomena such as flexing, gating, breathing and negative gas adsorption (NGA). The switching mechanism of structural transformation in flexible crystalline frameworks involves huge cell volume changes exceeding 200 %. Parallelized diffraction-adsorption instrumentation (in situ analysis) at temperatures ranging from 60 – 300 K connected to a high resolution adsorption instrument (0.01 Pa – 100 kPa) is an enabling technique to shine light on the structural transformations via Rietveld refinement of intermediary phases using synchrotron X-ray powder diffraction. Molecular simulations complement the findings and provide means for rationalizing the energetics along the adsorption pathway. The interplay of customized syntheses, in situ X-ray and NMR characterization of dynamics, and simulation gives detailed insights into switching mechanisms and their kinetic barriers. Switchable MOFs show great potential as threshold sensors, gas storage materials, or highly selective adsorbents. An in depth understanding of switching phenomena may enable the highly selective recognition of small molecules in biomimetic devices in future.

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