Computational Modeling of Adsorption of Complex Molecules in Metal-Organic Frameworks

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AGRAWAL-DISSERTATION-2019.pdf (7.02 MB)
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Agrawal, Mayank
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School of Chemical and Biomolecular Engineering
School established in 1901 as the School of Chemical Engineering; in 2003, renamed School of Chemical and Biomolecular Engineering
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http://hdl.handle.net/1853/64034
Abstract
Metal-organic frameworks (MOFs) are nanoporous materials that have organic parts connected to metal nodes constructing a crystalline structures. MOFs are intrinsically flexible in nature, however, general practices in computational studies of MOFs assume the structure to be rigid during simulations. In this thesis, we focus on the effects of framework flexibility in MOFs on their adsorption properties. We first divided the flexibility in MOFs into two categories: flexibility with constant volume (ΔV=0) and flexibility with volume change (ΔV≠0). We then demonstrated that flexibility with ΔV=0 in MOFs can affect their adsorption at dilute loadings and multicomponent adsorption significantly but have negligible effects on the single component adsorption at high loadings. Following this work, we studied MIL-53, a MOF that show the flexibility ΔV≠0 and concluded that the flexibility with ΔV≠0 can significantly affect even the single component adsorption in MOFs. In the second half of the thesis, we focused on the adsorption and diffusion properties of chemical warfare agents (CWAs) and their simulants in MOFs. We compared the Henry constants of two CWAs, sarin and soman, with their simulants to study whether the available simulants are accurately able to mimic the CWAs’ adsorption properties. We then extended this study to calculate diffusion coefficients of CWAs and simulants. Our results showed that dimethyl-methylphosphonate (DMMP) is the best simulant available to mimic adsorption and diffusion properties of sarin while dimethyl nitrophenylphosphonate (DMNP) is the closest simulant to predit soman’s adsorption properties. Finally, we performed a literature meta-analysis to assess the frequency of replicate materials synthesis and found that less than 12% of MOFs have been replicated in a published report. The methodology and the findings of this thesis advance the scientific knowledge on adsorption and diffusion in nanoporous materials and suggest ways how the research community can improve replicability of these materials.
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2019-11-01
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