Researcher:
Kadıoğlu, Özge

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Master Student

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Özge

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Kadıoğlu

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Kadıoğlu, Özge

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    Publication
    Efficient separation of helium from methane using MOF membranes
    (Elsevier, 2018) N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Kadıoğlu, Özge; Keskin, Seda; Master Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 40548
    Traditional separation methods of helium recovery are energy intensive and economically disadvantageous. Considering the potential deficit of helium, it is very important to develop efficient technologies for helium recovery from natural gas sources. Metal organic frameworks (MOFs) have emerged as strong alternatives to traditional membrane materials due to their wide range of pore sizes, permanent porosities, and high surface areas. Only a small number of MOF membranes has been fabricated and experimentally tested for He/CH4 separations. In this study, we performed the first large-scale computational study to predict He/CH4 separation performances of various MOF membranes. First, we compared predictions of our molecular simulations with the experimentally available data for He permeability of several MOF membranes. Motivated from the good agreement between experiments and simulations, we examined 139 different MOF membranes for He/CH4 separation. Selectivity and permeability of the MOF membranes were compared with those of traditional polymer and zeolite membranes. A significant number of MOF membranes was identified to exceed the Robeson’s upper bound due to their high gas selectivities and permeabilities. We also compared ideal and mixture selectivities of MOF membranes performing molecular simulations both for single-component gases, He and CH4, and binary gas mixtures of He/CH4. Results showed that selectivities and permeabilities of MOF membranes calculated using the single-component gas data can significantly overestimate the ones calculated using the mixture data. Results of this study will be useful to guide the experiments fo
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    PublicationOpen Access
    Evaluating charge equilibration methods to generate electrostatic fields in nanoporous materials
    (American Chemical Society (ACS), 2019) Ongari, Daniele; Boyd, Peter G.; Mace, Amber K.; Smit, Berend; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Keskin, Seda; Kadıoğlu, Özge; Faculty Member; Graduate School of Sciences and Engineering; 40548; N/A
    Charge equilibration (Qeq) methods can estimate the electrostatic potential of molecules and periodic frameworks by assigning point charges to each atom, using only a small fraction of the resources needed to compute density functional (DFT)-derived charges. This makes possible, for example, the computational screening of thousands of microporous structures to assess their performance for the adsorption of polar molecules. Recently, different variants of the original Qeq scheme were proposed to improve the quality of the computed point charges. One focus of this research was to improve the gas adsorption predictions in metal-organic frameworks (MOFs), for which many different structures are available. In this work, we review the evolution of the method from the original Qeq scheme, understanding the role of the different modifications on the final output. We evaluated the result of combining different protocols and set of parameters, by comparing the Qeq charges with high quality DFT-derived DDEC charges for 2338 MOF structures. We focused on the systematic errors that are attributable to specific atom types to quantify the final precision that one can expect from Qeq methods in the context of gas adsorption where the electrostatic potential plays a significant role, namely, CO2 and H2S adsorption. In conclusion, both the type of algorithm and the input parameters have a large impact on the resulting charges, and we draw some guidelines to help the user to choose the proper combination of the two for obtaining a meaningful set of charges. We show that, considering this set of MOFs, the accuracy of the original Qeq scheme is often still comparable with the most recent variants, even if it clearly fails in the presence of certain atom types, such as alkali metals.