UHV Surface Science Investigations of Adsorption, Reaction and Diffusion in Ultra-thin Metal Organic Framework Films
Technical Report,15 Apr 2017,14 Jan 2018
University of Texas at Austin Austin United States
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Briefly, our goals were to grow ultrathin films of ZIF-8 and also attempt to grow HKUST-1 films under ultrahigh vacuum UHV conditions. Very little research utilizing surface science tools toward the study of MOFs has been performed previously and such studies could advance the field significantly. ZIF-8 ZIF-8 is a prototypical zeolitic MOF, in which zinc atoms are coordinated by organic imidazolate linkers, featuring large cavities which are interconnected by narrow windows that allow, in principle, molecular sieving. ZIF-8 has been examined extensively in the literature for separation through molecular sieving and adsorptive removal of specific molecules. In ZIF-8, zinc cations are coordinated to four 2-methylimidazolate ligands, resulting in a hybrid material with sodalite topology SOD which is chemically and thermally stable up to 500 deg C. The sodalite cages possess a pore diameter of 11.6 and the aperture between two cages is 3.4 . The positions of the metal centers in ZIF structures are quite rigid, but the imidazolate ligands can rotate flip around the M M axis, thereby modifying the size of the pore aperture. This flexibility of the ligands has led to gate opening effects in the adsorption of light hydrocarbons. This gate opening could be induced by gas adsorption or high pressure. Study of MOFs beyond ZIF-8 As stated earlier we will begin our investigations employing the ZIF-8 MOF since this framework has been heavily studied and we believe that we can gain valuable experience with this material. Together with our work on ZIF-8 we will also study the vacuum synthesis of other relevant MOFs, most particularly HKUST-1.
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