Researcher:
Velioğlu, Sadiye

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Sadiye

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Velioğlu

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Velioğlu, Sadiye

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2018 - 20199

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    Tunable affinity separation enables ultrafast solvent permeation through layered double hydroxide membranes
    (Elsevier, 2019) Ang, Edison Huixiang; Chew, Jia Wei; Department of Chemical and Biological Engineering; Velioğlu, Sadiye; Researcher; Department of Chemical and Biological Engineering; College of Engineering; 200650
    Membranes are playing increasingly important roles in purification and separation processes due to inherent advantages like facile, low-cost and green compared to the traditional thermal-driven processes. To enhance permeability to further augment the feasibility of membrane-filtration, emerging two-dimensional (2D) materials are promising as building blocks for making organic solvent nanofiltration (OSN) membranes. The key novelty of this study is the demonstration that, by simply altering the divalent cation type in the layered double hydroxide (LDH) crystal structure, the physicochemical activities of the membranes can be significantly enhanced to allow for the permeation of solvent at an ultrafast rate. Results show that the micrometre-thick LDH laminate supported on a nylon substrate not only provided superb solutes rejection, but also enabled nanofiltration permeances in aqueous and organic solvents (namely, acetone) as high as 298 and 651 l m(-2) h(-1) bar(-1), respectively. Both experiments and simulations suggest that the superior performance originates from the interfacial interactions between the solvent and LDH.
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    An extensive comparative analysis of two MOF databases: high-throughput screening of computation-ready MOFs for CH4 and H2 adsorption
    (Royal Soc Chemistry, 2019) Erucar, Ilknur; N/A; N/A; N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Altıntaş, Çiğdem; Avcı, Gökay; Harman, Hilal Dağlar; Azar, Ayda Nemati Vesali; Velioğlu, Sadiye; Keskin, Seda; Researcher; PhD Student; PhD Student; PhD Student; Researcher; Faculty Member; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; N/A; 200650; 40548
    Computation-ready metal-organic framework (MOF) databases (DBs) have tremendous value since they provide directly useable crystal structures for molecular simulations. The currently available two DBs, the CoRE DB (computation-ready, experimental MOF database) and CSDSS DB (Cambridge Structural Database non-disordered MOF subset) have been widely used in high-throughput molecular simulations. These DBs were constructed using different methods for collecting MOFs, removing bound and unbound solvents, treating charge balancing ions, missing hydrogens and disordered atoms of MOFs. As a result of these methodological differences, some MOFs were reported under the same name but with different structural features in the two DBs. In this work, we first identified 3490 common MOFs of CoRE and CSDSS DBs and then performed molecular simulations to compute their CH4 and H-2 uptakes. We found that 387 MOFs result in different gas uptakes depending on from which DB their structures were taken and we identified them as problematic' MOFs. CH4/H-2 mixture adsorption simulations showed that adsorbent performances of problematic MOFs, such as selectivity and regenerability, also significantly change depending on the DB used and lead to large variations in the ranking of materials and identification of the top MOFs. Possible reasons of different structure modifications made by the two DBs were investigated in detail for problematic MOFs. We described five main cases to categorize the problematic MOFs and discussed what types of different modifications were performed by the two DBs in terms of removal of unbound and bound solvents, treatment of missing hydrogen atoms, charge balancing ions etc. with several examples in each case. With this categorization, we aimed to direct researchers to computation-ready MOFs that are the most consistent with their experimentally reported structures. We also provided the new computation-ready structures for 54 MOFs for which the correct structures were missing in both DBs. This extensive comparative analysis of the two DBs will clearly show how and why the DBs differently modified the same MOFs and guide the users to choose either of the computation-ready MOFs from the two DBs depending on their purpose of molecular simulations.
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    PublicationOpen Access
    Database for CO2 separation performances of MOFs based on computational materials screening
    (American Chemical Society (ACS), 2018) Eruçar, İlknur; Department of Chemical and Biological Engineering; Altıntaş, Çiğdem; Avcı, Gökay; Harman, Hilal Dağlar; Azar, Ayda Nemati Vesali; Velioğlu, Sadiye; Keskin, Seda; Researcher; Post Doctorate Student; Department of Chemical and Biological Engineering; College of Engineering; N/A; N/A; N/A; N/A; N/A; 40548
    Metal-organic frameworks (MOFs) are potential adsorbents for CO2 capture. Because thousands of MOFs exist, computational studies become very useful in identifying the top performing materials for target applications in a time-effective manner. In this study, molecular simulations were performed to screen the MOF database to identify the best materials for CO2 separation from flue gas (CO2/N-2) and landfill gas (CO2/CH4) under realistic operating conditions. We validated the accuracy of our computational approach by comparing the simulation results for the CO2 uptakes, CO2/N-2 and CO2/CH4 selectivities of various types of MOFs with the available experimental data. Binary CO2/N-2 and CO2/CH4 mixture adsorption data were then calculated for the entire MOF database. These data were then used to predict selectivity, working capacity, regenerability, and separation potential of MOFs. The top performing MOF adsorbents that can separate CO2/N-2 and CO2/CH4 with high performance were identified. Molecular simulations for the adsorption of a ternary CO2/N-2/CH4 mixture were performed for these top materials to provide a more realistic performance assessment of MOF adsorbents. The structure-performance analysis showed that MOFs with Delta Q(st)(0) > 30 kJ/mol, 3.8 angstrom < pore-limiting diameter < 5 angstrom, 5 angstrom < largest cavity diameter < 7.5 angstrom, 0.5 < phi < 0.75, surface area < 1000 m(2)/g, and rho > 1 g/cm(3) are the best candidates for selective separation of CO2 from flue gas and landfill gas. This information will be very useful to design novel MOFs exhibiting high CO2 separation potentials. Finally, an online, freely accessible database https://cosmoserc.ku.edu.tr was established, for the first time in the literature, which reports all of the computed adsorbent metrics of 3816 MOFs for CO2/N-2, CO2/CH4, and CO2/N-2/CH4 separations in addition to various structural properties of MOFs.
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    PublicationOpen Access
    Large-scale computational screening of MOF membranes and MOF-based polymer membranes for H2/N2 separations
    (American Chemical Society (ACS), 2019) Department of Chemical and Biological Engineering; Azar, Ayda Nemati Vesali; Velioğlu, Sadiye; Keskin, Seda; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; N/A; 200650; 40548
    Several thousands of metal organic frameworks (MOFs) have been reported to date, but the information on H-2/N-2 separation performances of MOF membranes is currently very limited in the literature. We report the first large-scale computational screening study that combines state-of-the-art molecular simulations, grand canonical Monte Carlo (GCMC) and molecular dynamics (MD), to predict H-2 permeability and H-2/N-2 selectivity of 3765 different types of MOF membranes. Results showed that MOF membranes offer very high H-2 permeabilities, 2.5 x 10(3) to 1.7 x 10(6) Barrer, and moderate H-2/N-2 membrane selectivities up to 7. The top 20 MOF membranes that exceed the polymeric membranes' upper bound for H-2/N-2 separation were identified based on the results of initial screening performed at infinite dilution condition. Molecular simulations were then carried out considering binary H-2/N-2 and quaternary H-2/N-2/CO2/CO mixtures to evaluate the separation performance of MOF membranes under industrial operating conditions. Lower H-2 permeabilities and higher N-2 permeabilities were obtained at binary mixture conditions compared to the ones obtained at infinite dilution due to the absence of multicomponent mixture effects in the latter. Structure performance relations of MOFs were also explored to provide molecular-level insights into the development of new MOF membranes that can offer both high H-2 permeability and high H-2/N-2 selectivity. Results showed that the most promising MOF membranes generally have large pore sizes (>6 A) as well as high surface areas (>3500 m(2)/g) and high pore volumes (>1 cm(3)/g). We finally examined H-2/N-2 separation potentials of the mixed matrix membranes (MMMs) in which the best MOF materials identified from our high-throughput screening were used as fillers in various polymers. Results showed that incorporation of MOFs into polymers almost doubles H-2 permeabilities and slightly enhances H-2/N-2 selectivities of polymer membranes, which can advance the current membrane technology for efficient H-2 purification.
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    PublicationOpen Access
    Simulation of H-2/CH4 mixture permeation through MOF membranes using non-equilibrium molecular dynamics
    (Royal Society of Chemistry (RSC), 2019) Department of Chemical and Biological Engineering; Keskin, Seda; Velioğlu, Sadiye; Faculty Member; Post Doctorate Student; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; 40548; N/A
    Grand canonical Monte Carlo (GCMC) simulations are widely used with equilibrium molecular dynamics (EMD) to predict gas adsorption and diffusion in single-crystals of metal-organic frameworks (MOFs). Adsorption and diffusion data obtained from these simulations are then combined to predict gas permeabilities and selectivities of MOF membranes. This GCMC + EMD approach is highly useful to screen a large number of MOFs for a target membrane-based gas separation process. External field nonequilibrium molecular dynamics (NEMD) simulations, on the other hand, can directly compute gas permeation by providing an accurate representation of MOF membranes but they are computationally demanding and require long simulation times. In this work, we performed NEMD simulations to investigate H-2/CH4 separation performances of MOF membranes. Both single-component and binary mixture permeabilities of H-2 and CH4 were computed using the NEMD approach and results were compared with the predictions of the GCMC + EMD approach and experimental measurements reported in the literature. Our results showed that there is a good agreement between NEMD simulations and experiments for the permeability and selectivity of MOF membranes. NEMD simulations provided the direct observation of the mass transfer resistances on the pore mouth of MOF membranes, which is neglected in the GCMC + EMD approach. Our results suggested that once the very large numbers of MOF materials were screened using the GCMC + EMD approach, more detailed NEMD calculations can be performed for the best membrane candidates to unlock the actual gas transport mechanism before the experimental fabrication of MOF membranes.
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    PublicationOpen Access
    Reply to comment on "database for CO2 separation performances of MOFs based on computational materials screening"
    (American Chemical Society (ACS), 2019) Department of Chemical and Biological Engineering; Altıntaş, Çiğdem; Velioğlu, Sadiye; Keskin, Seda; Researcher; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; N/A; 200650; 40548
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    PublicationOpen Access
    In silico design of MOFs with enhanced CO2 separation performances: role of metal sites
    (American Chemical Society (ACS), 2019) Department of Chemical and Biological Engineering; Avcı, Gökay; Velioğlu, Sadiye; Keskin, Seda; Post Doctorate Student; Faculty Member; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; N/A; 200650; 40548
    In this study, grand canonical Monte Carlo simulations were performed to investigate the impact of metal centers on CO2/H-2 mixture adsorption and separation performance of two different metal organic framework (MOF) series, M-HKUST-1 and M-HATGUF, where M represents different metals: Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Ru, and Zn. Results show that the type of metal site affects the CO2 and H-2 uptakes of MOFs, and as a result, adsorbent performance metrics of MOFs such as selectivity, working capacity, regenerability, and adsorbent performance score significantly vary depending on the metal type. Cr-HKUST-1 and Cd-HKUST-1 were identified to have 11% and 38% enhanced CO2/H-2 selectivities in addition to 27% and 60% enhanced adsorbent performance scores compared to original Cu-HKUST-1, respectively. CO2/H-2 selectivity of HATGUF was found to be almost doubled by changing the metal from Cu to Cd in addition to 142% increase in the adsorbent performance score of HATGUF. Our results revealed that changing the metal type of MOFs offers a great opportunity in the way of improving the CO2/H-2 separation performance of materials. Considering the very large number of available MOFs and metals, these results will be useful to design new MOFs by directing the selection of metals that will lead to high-performance adsorbents for CO2 capture.
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    PublicationOpen Access
    An extensive comparative analysis of two MOF databases: high-throughput screening of computation-ready MOFs for CH4 and H2 adsorption
    (Royal Society of Chemistry (RSC), 2019) Eruçar, İlknur; Department of Chemical and Biological Engineering; Keskin, Seda; Velioğlu, Sadiye; Altıntaş, Çiğdem; Avcı, Gökay; Harman, Hilal Dağlar; Azar, Ayda Nemati Vesali; Researcher; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; 40548; N/A; N/A; N/A; N/A; N/A
    Computation-ready metal–organic framework (MOF) databases (DBs) have tremendous value since they provide directly useable crystal structures for molecular simulations. The currently available two DBs, the CoRE DB (computation-ready, experimental MOF database) and CSDSS DB (Cambridge Structural Database non-disordered MOF subset) have been widely used in high-throughput molecular simulations. These DBs were constructed using different methods for collecting MOFs, removing bound and unbound solvents, treating charge balancing ions, missing hydrogens and disordered atoms of MOFs. As a result of these methodological differences, some MOFs were reported under the same name but with different structural features in the two DBs. In this work, we first identified 3490 common MOFs of CoRE and CSDSS DBs and then performed molecular simulations to compute their CH4 and H2 uptakes. We found that 387 MOFs result in different gas uptakes depending on from which DB their structures were taken and we identified them as ‘problematic’ MOFs. CH4/H2 mixture adsorption simulations showed that adsorbent performances of problematic MOFs, such as selectivity and regenerability, also significantly change depending on the DB used and lead to large variations in the ranking of materials and identification of the top MOFs. Possible reasons of different structure modifications made by the two DBs were investigated in detail for problematic MOFs. We described five main cases to categorize the problematic MOFs and discussed what types of different modifications were performed by the two DBs in terms of removal of unbound and bound solvents, treatment of missing hydrogen atoms, charge balancing ions etc. with several examples in each case. With this categorization, we aimed to direct researchers to computation-ready MOFs that are the most consistent with their experimentally reported structures. We also provided the new computation-ready structures for 54 MOFs for which the correct structures were missing in both DBs. This extensive comparative analysis of the two DBs will clearly show how and why the DBs differently modified the same MOFs and guide the users to choose either of the computation-ready MOFs from the two DBs depending on their purpose of molecular simulations.
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    PublicationOpen Access
    High-throughput screening of MOF adsorbents and membranes for H-2 purification and CO2 capture
    (American Chemical Society (ACS), 2018) Department of Chemical and Biological Engineering; Keskin, Seda; Avcı, Gökay; Velioğlu, Sadiye; Faculty Member; Post Doctorate Student; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; 40548; N/A; N/A
    Metal organic frameworks (MOFs) have emerged as great adsorbent and membrane candidates for separation of CO2/H-2 mixtures. The main challenge is the existence of thousands of MOFs, which requires computational screening methods to identify the best materials prior to experimental efforts. In this study, we performed high-throughput computational screening of MOFs to examine their adsorbent and membrane performances for CO2/H-2 separation. Grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations were used to compute various adsorbent and membrane performance metrics of 3857 MOFs. CO2/H-2 adsorption selectivities of MOFs at pressure swing adsorption (PSA) and vacuum swing adsorption (VSA) conditions were calculated to be in the range of 2.5-25 000 and 2.5-85 000, respectively, outperforming many zeolite adsorbents. Correlations between the ranking of MOF adsorbents at the PSA and VSA conditions were examined. H-2/CO2 selectivities and H-2 permeabilities of MOF membranes were computed as 2.1 X 10(-5)-6.3 and 230-1.7 X 10(6) Barrer, respectively. A high number of MOF membranes was identified to surpass the upper bound defined for gas permeabilities of MOFs. Structure performance relations revealed that MOFs with narrow pore sizes the best adsorbent materials for separation of CO2 from H-2, whereas MOFs with large pore sizes and high polymers due to high and low porosities are porosities are the best membrane materials for selective separation of H-2. Our results will guide the selection of MOF adsorbents and membranes for efficient H-2 purification and CO2 capture processes.