Berlin 2015 – scientific programme

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DS: Fachverband Dünne Schichten

DS 26: Layer Properties: Electrical, Optical, and Mechanical Properties

DS 26.14: Talk

Wednesday, March 18, 2015, 18:30–18:45, H 2032

Real-time monitoring mof crystals *breathing* upon humidity guest loading — •Theodoros Baimpos, Buddha Ratna Shrestha, and Markus Valtiner — Department for Interface Chemistry and Surface Engineering, Max Planck Institut fur Eisenforschung GmbH, D-40237, Dusseldorf, Germany

Porous Metal-organic frameworks (MOFs) are 3D crystalline coordination polymers consisting of metal ions linked each other by organic ligands. One of their main applications is as membranes for gas mixtures separation/purification where the MOF crystal act as internal molecular sieve by permitting only in the smaller molecules to pass their pore and get adsorbed in the available adsorption sites, excluding the bigger ones. If the adsorption affects the size of the crystal (expansion or shrinkage) then the performance of the membrane is significantly affected. In this study we examine with with Surface Force Apparatus (SFA) and its high time resolution (500 msec) the effect of humidity adsorption on the size of HKUST-1 crystals. With SFA, even complicated series of swelling phenomena may be visible, real time, even with naked eye, monitored and recorded on a TV screen by watching the motion of the fringes of equal chromatic order (FECO). In particular for the case of HKUST-1 and the loading/unloading with humidity vapors, a complex deformation behavior (contraction-expansion-contraction-expansion) is noticed for first time, upon humidity loading which is attributed to the gradual filling of the 4 different kinds of adsorption sites found in the unit cell of the crystal.