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Publication Open Access A novel IL/MOF/polymer mixed matrix membrane having superior CO2/N2 selectivity(Elsevier, 2022) Department of Chemical and Biological Engineering; Habib, Nitasha; Durak, Özce; Zeeshan, Muhammad; Uzun, Alper; Keskin, Seda; PhD Student; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 59917; 40548In this work, we synthesized an ionic liquid (IL)/metal organic framework (MOF) composite, 1-ethyl-3-methylimidazolium acetate/copper-1,3,5-benzenetricarboxylate ([EMIM][OAc]/CuBTC) and used it as a filler in a polymer, Pebax, to fabricate novel IL/MOF/polymer mixed matrix membranes (MMMs). CuBTC/Pebax and [EMIM][OAc]/CuBTC/Pebax MMMs having different filler loadings of 10, 15, and 20 wt.% were prepared by solution casting method and characterized using various techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), and thermogravimetric analysis (TGA). Uniform dispersion of MOF and IL/MOF fillers in the MMMs was observed. Incorporation of IL/MOF composite into Pebax significantly improved CO2 permeability and CO2/N2 selectivity of the polymer by 2.5- and 5.5-times, respectively. Gas permeability measurements showed that the MMM having 15 wt.% IL/MOF loading exhibits significantly higher CO2 permeability of 335 Barrer and CO2/N2 selectivity of 176 than the Pebax membrane having CO2 permeability of 135 Barrer and CO2/N2 selectivity of 32. CO2/N2 selectivity of the [EMIM][OAc]/CuBTC/Pebax MMM with 15 wt.% [EMIM][OAc]/CuBTC filler loading was the highest among the selectivity values reported for other types of IL/MOF/polymer MMMs in the literature. All the CuBTC/Pebax MMMs and [EMIM][OAc]/CuBTC/Pebax MMMs that we fabricated in this work exceeded the Robeson's updated upper bound, showing the excellent potential of these novel membranes for CO2/N2 separation.Publication Open Access A novel method for PEGylation of chitosan nanoparticles through photopolymerization(Royal Society of Chemistry (RSC), 2019) Department of Chemical and Biological Engineering; Bozüyük, Uğur; Gökulu, İpek Simay; Doğan, Nihal Olcay; Kızılel, Seda; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; N/A; N/A; N/A; 28376An ultrafast and convenient method for PEGylation of chitosan nanoparticles has been established through a photopolymerization reaction between the acrylate groups of PEG and methacrylated-chitosan nanoparticles. The nanoparticle characteristics under physiological pH conditions were optimized through altered PEG chain length, concentration and duration of UV exposure. The method developed here has potential for clinical translation of chitosan nanoparticles. It also allows for the scalable and fast synthesis of nanoparticles with colloidal stability.Publication Open 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/AScreening 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.Publication Open Access Aerogels in drug delivery: from design to application(Elsevier, 2021) García-González, C. A.; Sosnik, A.; Kalmar, J.; De Marco, I.; Concheiro, A.; Alvarez-Lorenzo, C.; Department of Chemical and Biological Engineering; Erkey, Can; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; 29633Aerogels are the lightest processed solid materials on Earth and with the largest empty volume fraction in their structure. Composition versatility, modularity, and feasibility of industrial scale manufacturing are behind the fast emergence of aerogels in the drug delivery field. Compared to other 3D materials, the high porosity (interconnected mesopores) and high specific surface area of aerogels may allow faster loading of small-molecule drugs, less constrained access to inner regions of the matrix, and more efficient interactions of the biological milieu with the polymer matrix. Processing in supercritical CO2 medium for both aerogel production (drying) and drug loading (impregnation) has remarkable advantages such as absence of an oxidizing environment, clean manufacture, and easiness for the scale-up under good manufacturing practices. The aerogel solid skeleton dictates the chemical affinity to the different drugs, which in turn determines the loading efficiency and the release pattern. Aerogels can be used to increase the solubility of BCS Class II and IV drugs because the drug can be deposited in amorphous state onto the large surface area of the skeleton, which facilitates a rapid contact with the body fluids, dissolution, and release. Conversely, tuning the aerogel structure by functionalization with drug-binding moieties or stimuli-responsive components, application of coatings and incorporation of drug-loaded aerogels into other matrices may enable site-specific, stimuli-responsive, or prolonged drug release. The present review deals with last decade advances in aerogels for drug delivery. An special focus is paid first on the loading efficiency of active ingredients and release kinetics under biorelevant conditions. Subsequent sections deal with aerogels intended to address specific therapeutic demands. In addition to oral delivery, the physical properties of the aerogels appear to be very advantageous for mucosal administration routes, such as pulmonary, nasal, or transdermal. A specific section devoted to recent achievements in gene therapy and theranostics is also included. In the last section, scale up strategies and life cycle assessment are comprehensively addressed.Publication Open 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/AComputation-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.Publication Open Access An integrated computational-experimental hierarchical approach for the rational design of an IL/UiO-66 composite offering infinite CO2 selectivity(Wiley, 2022) Department of Chemical and Biological Engineering; Department of Chemistry; Zeeshan, Muhammad; Gülbalkan, Hasan Can; Durak, Özce; Haşlak, Zeynep Pınar; Ünal, Uğur; Keskin, Seda; Uzun, Alper; PhD Student; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Engineering; College of Sciences; Graduate School of Sciences and Engineering; N/A; N/A; N/A; N/A; 42079; 40548; 59917Owing to the possibility of generating theoretically unlimited numbers of ionic liquid (IL)-metal-organic framework (MOF) combinations, experimental studies on IL/MOF composites for gas separation applications are mostly conducted on a trial-and-error basis. To address this problem, an integrated computational-experimental hierarchical approach is presented for selecting the best IL-MOF combination for a target gas separation application. For this purpose, UiO-66 and pyrrolidinium-based ILs are chosen as the parent MOF and IL family, respectively, and three powerful computational tools, Conductor-like Screening Model for Realistic Solvents calculations, density functional theory calculations, and grand canonical Monte Carlo simulations, are integrated to identify the most promising IL-UiO-66 combination as 1-n-butyl-1-methylpyrrolidinium dicyanamide/UiO-66, [BMPyrr][DCA]/UiO-66. Then, this composite is synthesized, characterized in deep detail, and tested for CO2/N-2, CO2/CH4, and CH4/N-2 separations. Results demonstrate that [BMPyrr][DCA]/UiO-66 offers an extraordinary gas separation performance, with practically infinite CO2 and CH4 selectivities over N-2 at 15 degrees C and at low pressures. The integrated hierarchical approach proposed in this work paves the way for the rational design and development of novel IL/MOF composites offering exceptional performance for any desired gas separation application.Publication Open Access An opinion paper on aerogels for biomedical and environmental applications(Multidisciplinary Digital Publishing Institute (MDPI), 2019) Garcia-Gonzalez, Carlos A.; Budtova, Tatiana; Duraes, Luisa; Del Gaudio, Pasquale; Gurikov, Pavel; Koebel, Matthias; Liebner, Falk; Neagu, Monica; Smirnova, Irina; Department of Chemical and Biological Engineering; Erkey, Can; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; 29633Aerogels are a special class of nanostructured materials with very high porosity and tunable physicochemical properties. Although a few types of aerogels have already reached the market in construction materials, textiles and aerospace engineering, the full potential of aerogels is still to be assessed for other technology sectors. Based on current efforts to address the material supply chain by a circular economy approach and longevity as well as quality of life with biotechnological methods, environmental and life science applications are two emerging market opportunities where the use of aerogels needs to be further explored and evaluated in a multidisciplinary approach. In this opinion paper, the relevance of the topic is put into context and the corresponding current research efforts on aerogel technology are outlined. Furthermore, key challenges to be solved in order to create materials by design, reproducible process technology and society-centered solutions specifically for the two abovementioned technology sectors are analyzed. Overall, advances in aerogel technology can yield innovative and integrated solutions for environmental and life sciences which in turn can help improve both the welfare of population and to move towards cleaner and smarter supply chain solutions.Publication Open Access Analysis of correlations between energy and residue fluctuations in native proteins and determination of specific sites for binding(American Physical Society (APS), 2009) Haliloğlu, Turkan; Department of Chemical and Biological Engineering; Erman, Burak; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; 179997The Gaussian network model is used to derive the correlations between energy and residue fluctuations in native proteins. Residues are identified that respond strongly to energy fluctuations and that display correlations with the remaining residues of the protein at the highest modes. We postulate that these residues are located at specific sites for drug binding. We test the validity of this postulate on a data set of 33 structurally distinct proteins in the unbound state. Detailed results are presented for drug binding to the HIV protease.
Publication Metadata only Application of the numerical fractionation approach to the design of biofunctional PEG hydrogel membranes(Wiley-V C H Verlag Gmbh, 2012) N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Kızılel, Rıza; Kızılel, Seda; Researcher; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; College of Engineering; 114475; 28376A mathematical model is described for surface-initiated photopolymerization of PEG-DA forming crosslinked biofunctional PEG hydrogel membranes based on the NF technique. The model includes an additional monomer with biological functionality, which is a common experimental strategy for the design of ECM mimics in tissue engineering in order to direct signaling pathways, and considers concentration-dependent VP propagation and reaction diffusion termination. The influence of these features on the crosslink density of the soluble and gel phases, the progression through gelation, sol/gel fraction, and molecular weight distribution of biofunctional PEG hydrogel are studied using the NF model. This model may be useful for specific applications of tissue engineering.Publication Open Access Assessing CH4/N2 separation potential of MOFs, COFs, IL/MOF, MOF/Polymer, and COF/Polymer composites(Elsevier, 2022) Department of Chemical and Biological Engineering; Keskin, Seda; Uzun, Alper; Altıntaş, Çiğdem; Haşlak, Zeynep Pınar; Faculty Member; Researcher; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Engineering; Graduate School of Sciences and Engineering; 40548; 59917; N/A; N/ASeparating CH4/N2 mixture is challenging, and performance of the existing materials is still open to improvement. In this study, we examined both the adsorption- and membrane-based CH4/N2 separation performances of 5034 different materials, including metal organic frameworks (MOFs), covalent organic frameworks (COFs), ionic liquid (IL)/MOF composites, MOF/polymer composites, and COF/polymer composites by performing high-throughput computational screening and molecular simulations. The top performing adsorbents and membranes were identified by computing several performance evaluation metrics. Investigation of the interactions between the gas molecules, the IL, and the top MOF was performed by density functional theory (DFT) calculations. Results pointed out that the interactions between the gas molecules and the linker fragments of the MOF are stronger than their interactions with the IL. Thus, as the IL molecules are loaded into the selected top MOF, they occupy the adsorption sites of the gases, decreasing CH4 and N2 uptakes and increasing the CH4/N2 selectivity. Our results revealed that MOFs offer great potential for adsorption-based CH4/N2 separation, and IL incorporation into MOFs remarkably increases their CH4/N2 selectivities. More than 25% of MOF and 70% of the COF membranes surpassed Robeson's upper bound because of high N2 permeabilities and outperformed conventional polymeric membranes. N2 permeabilities and selectivities of MOF/polymer and COF/polymer composites were found to be significantly higher than those of pure polymers. Our results emphasize the promises of the design and development of new MOF and COF adsorbents, membranes, and their composites with ILs and polymers for efficient CH4/N2 separation.