Researcher:
Aksu, Gökhan Önder

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PhD Student

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Gökhan Önder

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Aksu

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Aksu, Gökhan Önder

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2020 - 20235

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    Recent advances in computational modeling of MOFs: from molecular simulations to machine learning
    (Elsevier B.V., 2023) N/A; N/A; N/A; N/A; Department of Chemical and Biological Engineering; Demir, Hakan; Harman, Hilal Dağlar; Gülbalkan, Hasan Can; Aksu, Gökhan Önder; Keskin, Seda; Other; PhD Student; PhD Student; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; N/A; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; N/A; 40548
    The reticular chemistry of metal–organic frameworks (MOFs) allows for the generation of an almost boundless number of materials some of which can be a substitute for the traditionally used porous materials in various fields including gas storage and separation, catalysis, drug storage and delivery. The number of MOFs and their potential applications are growing so quickly that, when novel MOFs are synthesized, testing them for all possible applications is not practical. High-throughput computational screening approaches based on molecular simulations of materials have been widely used to investigate MOFs and identify the optimal MOFs for a specific application. Despite the growing computational resources, given the enormous MOF material space, computational identification of promising MOFs requires more efficient approaches in terms of time and effort. Leveraging data-driven science techniques can offer key benefits such as accelerated MOF design and discovery pathways via the establishment of machine learning (ML) models and interpretation of complex structure-performance relationships that can reach beyond expert intuition. In this review, we present key scientific breakthroughs that propelled computational modeling of MOFs and discuss the state-of-the-art approaches extending from molecular simulations to ML algorithms. Finally, we provide our perspective on the potential opportunities and challenges for the future of big data-driven MOF design and discovery. © 2023 The Authors
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    Exploring covalent organic frameworks for H2S+CO2 separation from natural gas using efficient computational approaches
    (Elsevier Sci Ltd, 2022) Erucar, Ilknur; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Aksu, Gökhan Önder; Haşlak, Zeynep Pınar; Keskin, Seda; PhD Student; Researcher; Faculty Member; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; 40548
    Covalent organic frameworks (COFs) are emerged as strong adsorbent candidates for industrial gas separation applications due to their highly porous structures. In this work, we explored H2S+CO2 capture potentials of synthesized and computer-generated COFs from a natural gas mixture using an efficient, multi-level computational screening approach. We computed the adsorption data of a six-component natural gas mixture, CH4/C2H6/ CO2/C3H8/H2S/H2O, for 580 synthesized COFs by performing Grand Canonical Monte Carlo (GCMC) simulations under industrially relevant conditions. H2S+CO2 selectivities and working capacities of COFs were computed to be 0.4-12.4 (0.2-8.5) and 0.01-5.36 (0.04-2.5) mol/kg at pressure-swing adsorption (vacuum-swing adsorption) condition. NPN-3 was identified as the best performing COF due to the competitive adsorption of H2S+CO2 over C2H6 and C3H8 as revealed by density functional theory (DFT) calculations. Structural (pore sizes, porosities, and topologies) and chemical properties (linker units and heats of gas adsorption) of the best-performing synthesized COFs were used to efficiently screen the very large number of hypothetical COFs (hypoCOFs). Results showed that isosteric heats of adsorption can be used to discover high performing hypoCOFs for H2S+CO2 separation from natural gas. Finally, we compared COFs, hypoCOFs, zeolites, carbon nanotubes, metal organic frameworks (MOFs) and concluded that several synthesized and computer-generated COFs can outperform traditional adsorbents in terms of H2S+CO2 selectivities. Our results provide molecular-level insights about the potential of COFs for natural gas purification and direct the design and development of new COF materials with high H2S+CO2 selectivities.
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    PublicationOpen Access
    Effect of MOF database selection on the assessment of gas storage and separation potentials of MOFs
    (Wiley, 2021) Eruçar, İlknur; Department of Chemical and Biological Engineering; N/A; Harman, Hilal Dağlar; Gülbalkan, Hasan Can; Aksu, Gökhan Önder; Altundal, Ömer Faruk; Altıntaş, Çiğdem; Avcı, Gökay; Keskin, Seda; Researcher; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; N/A; N/A; N/A; 40548
    Development of computation‐ready metal–organic framework databases (MOF DBs) has accelerated high‐throughput computational screening (HTCS) of materials to identify the best candidates for gas storage and separation. These DBs were constructed using structural curations to make MOFs directly usable for molecular simulations, which caused the same MOF to be reported with different structural features in different DBs. We examined thousands of common materials of the two recently updated, very widely used MOF DBs to reveal how structural discrepancies affect simulated CH4, H2, CO2 uptakes and CH4/H2 separation performances of MOFs. Results showed that DB selection has a significant effect on the calculated gas uptakes and ideal selectivities of materials at low pressure. A detailed analysis on the curated structures was provided to isolate the critical elements of MOFs determining the gas uptakes. Identification of the top‐performing materials for gas separation was shown to strongly depend on the DB used in simulations.
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    PublicationOpen Access
    Computational selection of high-performing covalent organic frameworks for adsorption and membrane-based CO2 /H2 separation
    (American Chemical Society (ACS), 2020) Department of Chemical and Biological Engineering; Keskin, Seda; Altıntaş, Çiğdem; Harman, Hilal Dağlar; Aksu, Gökhan Önder; Researcher; Department of Chemical and Biological Engineering; College of Engineering; Graduate School of Sciences and Engineering; 40548; N/A; N/A; N/A
    Covalent organic frameworks (COFs) have high potential in gas separation technologies because of their porous structures, large surface areas, and good stabilities. The number of synthesized COFs already reached several hundreds, but only a handful of materials were tested as adsorbents and/or membranes. We used a high-throughput computational screening approach to uncover adsorption-based and membrane-based CO2/H2 separation potentials of 288 COFs, representing the highest number of experimentally synthesized COFs studied to date for precombustion CO2 capture. Grand canonical Monte Carlo (GCMC) simulations were performed to assess CO2/H2 mixture separation performances of COFs for five different cyclic adsorption processes: pressure swing adsorption, vacuum swing adsorption, temperature swing adsorption (TSA), pressure−temperature swing adsorption (PTSA), and vacuum−temperature swing adsorption (VTSA). The results showed that many COFs outperform traditional zeolites in terms of CO2 selectivities and working capacities and PTSA is the best process leading to the highest adsorbent performance scores. Combining GCMC and molecular dynamics (MD) simulations, CO2 and H2 permeabilities and selectivities of COF membranes were calculated. The majority of COF membranes surpass Robeson’s upper bound because of their higher H2 permeabilities compared to polymers, indicating that the usage of COFs has enormous potential to replace current materials in membrane-based H2/CO2 separation processes. Performance analysis based on the structural properties showed that COFs with narrow pores [the largest cavity diameter (LCD) < 15 Å] and low porosities (ϕ < 0.75) are the top adsorbents for selective separation of CO2 from H2, whereas materials with large pores (LCD > 20 Å) and high porosities (ϕ > 0.85) are generally the best COF membranes for selective separation of H2 from CO2. These results will help to speed up the engineering of new COFs with desired structural properties to achieve high-performance CO2/H2 separations.
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    PublicationOpen Access
    Accelerating discovery of COFs for CO2 capture and H2 purification using structurally guided computational screening
    (Elsevier, 2022) Eruçar, İlknur; Department of Chemical and Biological Engineering; Keskin, Seda; Aksu, Gökhan Önder; Haşlak, Zeynep Pınar; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; Graduate School of Sciences and Engineering; 40548; N/A; N/A
    Screening of hypothetical covalent organic framework (hypoCOF) database enables to go beyond the current synthesized structures to design high-performance materials for CO2 separation. In this work, we followed a structurally guided computational screening approach to find the most promising candidates of hypoCOF adsorbents and membranes for CO2 capture and H2 purification. Grand canonical Monte Carlo (GCMC) simulations were used to evaluate CO2/H2 separation performance of 3184 hypoCOFs for pressure-swing adsorption (PSA) and vacuum-swing adsorption (VSA) processes. CO2/H2 adsorption selectivities and CO2 working capacities of hypoCOFs were calculated in the range of 6.13–742 (6.39–954) and 0.07–8.68 mol/kg (0.01–3.92 mol/kg), achieving higher values than those of experimentally synthesized COFs at PSA (VSA) conditions. Density functional theory (DFT) calculations revealed that the strength of hydrogen bonding between CO2 and the functional group of linkers is an important factor for determining the CO2 selectivity of hypoCOFs. The most predominant topologies and linker types were identified as bor and pts, linker91 (a triazine linker) and linker92 (a benzene linker) for the top-performing hypoCOF adsorbents, respectively. Molecular dynamics (MD) simulations of 794 hypoCOFs showed that they exceed the Robeson's upper bound by outperforming COF, zeolite, metal organic framework (MOF), and polymer membranes due to their high H2/CO2 selectivities, 2.66–6.14, and high H2 permeabilities, 9×105–4.5×106 Barrer. Results of this work will be useful to guide the synthesis of novel materials by providing molecular-level insights into the structural features of hypothetical COFs to achieve superior CO2 separation performance.