Friday, November 5, 2021 at 10:00am to 11:00am
Metal-organic frameworks (MOFs) are an inexpensive yet efficient alternative to costly distillation methods currently used for industrial separation. However, most of the studies regarding MOFs involve a single component adsorption scheme which is not a likely scenario due to the presence of impurities and gas contamination. In this regard, investigating co-adsorption in MOFs becomes critically desirable. In that spirit, we combine ab initio calculations along with in situ IR spectroscopy to study co-adsorption in MOFs and unveil several interesting and unexpected properties. For example, in contrast to the widespread belief that strongly co-adsorbed species in nano-porous materials gravely effect their adsorption/separation performance towards weakly-bound target molecules, we report a novel discovery that proves the opposite. Specifically, we found that addition of tightly bound NH3 molecules in the prototypical metal-organic framework MOF-74 can dramatically enhance its selective adsorption of C2H2 over C2H4. We also investigated the co-adsorption of NH3 and H2O and noted an unexpected behavior. Although the binding of NH3 is stronger, an increasing concentration of H2O can displace the strongly bound NH3. Despite the great success of MOF-74 series, their practical applications for carbon capture are limited by the presence of H2O—the existence of which is inevitable. Fortunately, there is another class of porous materials called hybrid ultramicroporous materials (HUMs) which can perform exceptionally well even in the presence of water. However, the exact mechanism of their extraordinary performance is unknown. We unlocked this mechanism and found that their co-adsorption is “non-competitive”, and they are involved in a duet rather than a duel. Inspired by these interesting results, we also explored molecular transport in SIFSIX-3-Ni. Interestingly, we find an unusual—“sideways”—diffusion for H2O. This discovery might have the potential to be used for water desalination and thus warrants further investigations.
(1) Ullah, S. et al. ACS AMI 2021, 13, 36, 43661–43667.
Dr. Saif Ullah earned his PhD degree in physics from Federal University of Juiz de Fora, Brazil where he worked on theoretical characterization of various aspects of 2D materials, including electronic and optical properties of graphene and other 2D layered materials, vdW heterostructures, cathode materials for metal-ion batteries, Defects, and designing new materials. Currently, he is a postdoc in Prof. Thonhauser’s group working on theoretical aspect of guest-guest and guest-host interaction in MOFs. He has authored/co-authored more than 30 journal publications.
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