Natural and Mathematical Sciences

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Open Access
Accelerating discovery of COFs for CO2 capture and H2 purification using structurally guided computational screening
(Elsevier, 2022-01-01) Aksu, G. O.; Fındıkçı, İlknur Eruçar; Haslak, Z. P.; Keskin, S.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
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.
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Biocompatible MOFs for storage and separation of O2: A molecular simulation study
(American Chemical Society, 2019-02-27) Gülçay, Ezgi; Fındıkçı, İlknur Eruçar; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar; Gülçay, Ezgi
Metal organic frameworks (MOFs) are great candidates for capturing 02 due to their highly porous structures and tunable physical and chemical properties. In this study, we assessed the performance of 1525 biocompatible MOFs which have endogenous linkers and nontoxic metal centers for adsorption-based and membrane-based O-2 separation and also for high-pressure O-2 storage. We initially computed Henry's constants of O-2 and N-2 at zero coverage and 298 K by performing Grand Canonical Monte Carlo (GCMC) simulations and estimated infinite dilution adsorption selectivities for O-2/N-2 mixture. We performed binary mixture GCMC simulations for the top 15 candidates at various pressures and 298 K and compared mixture adsorption selectivities with those obtained from infinite dilution. We then estimated O-2 working capacities of 315 biocompatible MOFs obtained at 298 K and 140 bar for storage and 5 bar for release pressures. Our results showed that 15 biocompatible MOFs outperform gravimetric O-2 working capacities of the traditional adsorbent materials such as activated carbon and NaX and some common MOFs such as NU-125 and UMCM-152 at 298 K. We finally calculated O-2 and N-2 permeabilities and membrane selectivities of 45 promising MOF candidates for O-2/N-2 separation. Seventeen biocompatible MOF membranes were identified to exceed the Robeson's upper bound established for polymers. This computational study will be useful to identify the promising biocompatible MOFs for storage and separation of O-2. The bio-MOF library constructed in this study will also guide both experimental and computational studies for design and development of biocompatible MOFs for various medical applications.
Open Access
Cationic metal-organic frameworks synthesized from cyclotetraphosphazene linkers with flexible tentacles
(American Chemical Society, 2022-12-07) Davarcı, D.; Fındıkçı, İlknur Eruçar; Yücesan, G.; Zorlu, Y.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
Metal-organic frameworks (MOFs) based on group 12 metals, namely, [Zn2(O3PyCP)Cl4] (Zn-O3PyCp), [Cd(O3PyCP)(NO3)2].H2O (Cd-O3PyCp), and [Hg(O3PyCP)Cl2] (Hg-O3PyCp), were synthesized using a novel flexible molecular building block, octakis(3-pyridyloxy)cyclotetraphosphazene (O3PyCP), and group 12 metal salts (ZnCl2, Cd(NO3)2.6H2O, and HgCl2). The crystals of each of the cationic frameworks were structurally characterized by single-crystal X-ray diffraction, Fourier transform infrared, and thermogravimetric analysis. Because of the flexibility of the O3PyCP building block, we were able to observe three distinct cationic frameworks with group 12 metal ions. We performed the atomically detailed simulations to compute H2 adsorption isotherms of the resulting frameworks at a pressure range of 0-1 bar at 77 K. Zn-O3PyCp exhibits the highest H2 uptake capacity (58.42 cm3 STP/g).
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Combining tensile test results with atomistic predictions of elastic modulus of graphene/polyamide-6,6 nanocomposites
(Elsevier, 2023-06) Batyrov, Merdan; Dericiler, K.; Palabıyık, Büşra Akkoca; Okan, B. S.; Öztürk, Hande; Fındıkçı, İlknur Eruçar; Mechanical Engineering; KAYMAKSÜT, Hande Öztürk; FINDIKÇI, Ilknur Eruçar; Batyrov, Merdan; Palabıyık, Büşra Akkoca
In this work, we combined tensile test results with atomistic simulations to investigate the effect of filler parameters including distribution, stacking, loading and lateral graphene size on elastic moduli of graphene/PA-6,6 nanocomposites. Stacked and randomly distributed atomistic models were adapted in Molecular Dynamics (MD) simulations to establish the limits of stiffness enhancement in graphene reinforced PA-6,6 nanocomposites with loading ratios changing from 0 to 1 wt%. Experimental results showed that incorporating of 0.3–0.4 wt% graphene loading improved the elastic modulus of the neat polymer by 41.7%−43.5%. While the test sample behaved close to the computational results of the stacked atomistic model at low graphene loadings up to 0.4 wt%, it overshot the predictions of the randomly distributed model at all considered loadings up to 1 wt%. Elastic moduli of graphene-based PA-6,6 nanocomposites increased linearly with graphene loading in the stacked model, however, no such relation was detected in the randomly distributed model. The lower stiffness enhancement provided by the randomly distributed model compared to the stacked model was revealed as the small lateral size of graphene plates in PA-6,6 matrix. As the graphene size increased, the elastic modulus of the graphene dramatically increased, directly improving the elastic modulus of the nanocomposite. The developed computational approach is highly useful to estimate the boundaries of stiffness enhancement provided by graphene dispersions in macroscale nanocomposite samples.
Open Access
Computational investigation of dual filler-incorporated polymer membranes for efficient CO2 and H2 separation: MOF/COF/Polymer mixed matrix membranes
(American Chemical Society, 2023-01-26) Aydın, S.; Altintas, C.; Fındıkçı, İlknur Eruçar; Keskin, S.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
Mixed matrix membranes (MMMs) composed of two different fillers such as metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) embedded into polymers provide enhanced gas separation performance. Since it is not possible to experimentally consider all possible combinations of MOFs, COFs, and polymers, developing computational methods is urgent to identify the best performing MOF-COF pairs to be used as dual fillers in polymer membranes for target gas separations. With this motivation, we combined molecular simulations of gas adsorption and diffusion in MOFs and COFs with theoretical permeation models to calculate H2, N2, CH4, and CO2 permeabilities of almost a million types of MOF/COF/polymer MMMs. We focused on COF/polymer MMMs located below the upper bound due to their low gas selectivity for five industrially important gas separations, CO2/N2, CO2/CH4, H2/N2, H2/CH4, and H2/CO2. We further investigated whether these MMMs could exceed the upper bound when a second type of filler, a MOF, was introduced into the polymer. Many MOF/COF/polymer MMMs were found to exceed the upper bounds showing the promise of using two different fillers in polymers. Results showed that for polymers having a relatively high gas permeability (≥104 barrer) but low selectivity (≤2.5) such as PTMSP, addition of the MOF as the second filler can have a dramatic effect on the final gas permeability and selectivity of the MMM. Property-performance relations were analyzed to understand how the structural and chemical properties of the fillers affect the permeability of the resulting MMMs, and MOFs having Zn, Cu, and Cd metals were found to lead to the highest increase in gas permeability of MMMs. This work highlights the significant potential of using COF and MOF fillers in MMMs to achieve better gas separation performances than MMMs with one type of filler, especially for H2 purification and CO2 capture applications.
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Computational investigation of metal organic frameworks for storage and delivery of anticancer drugs
(Royal Society of Chemistry, 2017-08-14) Fındıkçı, İlknur Eruçar; Keskin, S.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
Metal organic frameworks (MOFs) have been recently used in biomedical applications such as drug storage and drug delivery due to their large surface areas, high pore volumes, and tunable physical and chemical characteristics. In this study, we investigated MOF-74 materials for efficient storage and delivery of two anticancer drug molecules, methotrexate (MTX) and 5-fluorouracil (5-FU). We initially compared the results of our molecular simulations with the available experimental data for the MTX and 5-FU uptakes of various MOFs. Motivated by the good agreement between experiments and simulations, we computed MTX and 5-FU uptakes in 10 different MOF-74 materials having various physical and chemical properties. At low fugacity, MTX adsorption is favored over 5-FU since MTX has stronger interactions with the MOFs whereas at high fugacity, 5-FU adsorption is favored over MTX due to the entropic effects. Our results showed that MOF-74 materials outperform the MTX and 5-FU storage capacities of traditional materials such as polymeric nanoparticles and two dimensional layered nanomaterials. We also examined the diffusion of drug molecules in MOFs considering both single-component and mixture transport for the first time in the literature. Both drug molecules diffuse slowly in MOFs suggesting that MOF-74 materials are strong alternatives to traditional porous materials for delivery of MTX and 5-FU. This computational study will be useful to effectively identify the most promising MOFs for target drug delivery applications prior to experiments. Our results will also guide the experiments for the design and development of MOFs as anticancer drug carrier systems.
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Computational investigations of Bio-MOF membranes for uremic toxin separation
(Elsevier, 2022-01-15) Palabıyık, Büşra Akkoca; Batyrov, Merdan; Fındıkçı, İlknur Eruçar; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar; Palabıyık, Büşra Akkoca; Batyrov, Merdan
Developing new and efficient methods as an alternative to hemodialysis is important due to the challenges associated with poor efficiency of membranes and long dialysis sessions. Recently, metal organic frameworks (MOFs) have attracted interest in the membrane community due to their tunable physical and chemical properties. However, their potential in uremic toxin separations is still unknown and it is not practical to test each synthesized MOF for uremic toxin separations. The main objective of this study is to computationally assess membrane-based uremic toxin separation performances of 60 bio-compatible MOFs (bio-MOFs). Combining grand canonical Monte Carlo (GCMC) and equilibrium molecular dynamics (EMD) simulations, we predicted urea, creatinine, and water permeabilities of bio-MOFs and their membrane selectivities for urea/water and creatinine/water separations. Results showed that OREZES, a carboxylate-based MOF exhibited the highest membrane selectivity (347.94) for urea/water separation whereas BEPPIX, an amino-based MOF gave the highest creatinine/water selectivity (1.5 × 105) at infinite dilution and 310 K. Guest-guest and host–guest interaction energies for uremic toxins were also computed during EMD simulations and van der Waals interactions were found to be much stronger than the coulombic interactions. We finally examined the effect of MOF's flexibility on the predicted membrane performance and membrane selectivities of bio-MOFs for urea/water separation significantly enhanced when the structural flexibility was considered in simulations. Our results will be a guide for further studies to design novel bio-MOF membranes for uremic toxin separations.
Open Access
Computational screening of covalent organic frameworks for hydrogen storage
(Turkish Chemical Society, 2020) Gülçay, Ezgi; Fındıkçı, İlknur Eruçar; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar; Gülçay, Ezgi
Covalent Organic Frameworks (COFs) have been considered as promising materials for gas storage applications due to their highly porous structures and tunable characteristics. In this work, high-throughput molecular simulations were performed to screen the recent Computation-Ready Experimental COF Database (CoRE-COF) for H2 storage a first time in the literature. Predictions for H2 uptakes were first compared with the experimental data of several COFs. Motivated from the good agreement between simulations and experiments, we performed Grand Canonical Monte Carlo (GCMC) simulations to compute volumetric H2 uptakes of 296 COFs at various temperatures and pressures and identified the best candidates which exhibit a superior performance for H2 storage. COFs outperformed several well-known MOFs such as HKUST-1, NU-125, NU-1000 series, NOTT-112 and UiO-67 at 100bar/77K adsorption and 5bar/160K desorption conditions. We also examined the effect of Feynman-Hibbs correction on simulated H2 isotherms and H2 working capacities of COFs to consider quantum effects at low temperatures. Results showed that the Feynman-Hibbs corrections do not affect the ranking of materials based on H2 working capacities, but slightly affect the predictions of H2 adsorption isotherms. We finally examined the structure-performance relations and showed that density and porosity are highly correlated with the volumetric H2 working capacities of COFs. Results of this study will be highly useful in guiding future research and focusing experimental efforts on the best COF adsorbents identified in this study.
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Computational screening of MOFs for CO2 capture
(Springer, 2021-03-30) Altıntaş, Ç.; Fındıkçı, İlknur Eruçar; Keskin, S.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
The capture of CO2 (carbon dioxide) is an urgent environmental issue due to global warming. Adsorption-based CO2 capture using a new family of porous materials, metal-organic frameworks (MOFs), has been considered as a promising alternative to conventional methods. The rapid increase in the number of synthesized MOFs offers various materials for efficient CO2 capture, but assessing the performance of each MOF material using purely experimental methods is challenging. Recent progress in computational tools, high-throughput molecular simulations, and machine learning algorithms provide great opportunities for effective computational screening of MOFs with the aim of identifying the most promising adsorbents for CO2 capture prior to experimental studies. In this chapter, we focused on the recent advances in high-throughput screening of MOFs for CO2 capture and separation. We first reviewed the details of molecular simulation methods to compute CO2 adsorption properties of MOFs and adsorbent performance evaluation metrics that have been used to assess the CO2 separation potential of MOFs. Large-scale computational screening studies and quantitative structure-performance relationships obtained from molecular simulations were then discussed. Finally, opportunities and challenges of using computational tools to reveal the potential of MOFs for CO2 capture and separation were addressed.
Open Access
Database for CO2 separation performances of MOFs based on computational materials screening
(American Chemical Society, 2018-05-23) Altintas, C.; Avci, G.; Daglar, H.; Azar, A. N. V.; Velioglu, S.; Fındıkçı, İlknur Eruçar; Keskin, S.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
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.
Open Access
Do new MOFs perform better for CO2 capture and H2 purification? Computational screening of the updated MOF database
(ACS Publications, 2020-09-16) Avcı, G.; Fındıkçı, İlknur Eruçar; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
High-throughput computational screening of metal organic frameworks (MOFs) enables the discovery of new promising materials for CO2 capture and H2 purification. The number of synthesized MOFs is increasing very rapidly, and computation-ready, experimental MOF databases are being updated. Screening the most recent MOF database is essential to identify the best performing materials among several thousands. In this work, we performed molecular simulations of the most recent MOF database and described both the adsorbent and membrane-based separation performances of 10 221 MOFs for CO2 capture and H2 purification. The best materials identified for pressure swing adsorption, vacuum swing adsorption, and temperature swing adsorption processes outperformed commercial zeolites and previously studied MOFs in terms of CO2 selectivity and adsorbent performance score. We then discussed the applicability of Ideal Adsorbed Solution Theory (IAST), effects of inaccessible local pores and catenation in the frameworks and the presence of impurities in CO2/H2 mixture on the adsorbent performance metrics of MOFs. Very large numbers of MOF membranes were found to outperform traditional polymer and porous membranes in terms of H2 permeability. Our results show that MOFs that are recently added into the updated MOF database have higher CO2/H2 separation potentials than the previously reported MOFs. MOFs with small pores were identified as potential adsorbents for selective capture of CO2 from H2, whereas MOFs with high porosities were the promising membranes for selective separation of H2 from CO2. This study reveals the importance of enriching the number of MOFs in high-throughput computational screening studies for the discovery of new promising materials for CO2/H2 separation.
Open Access
Effect of metal–organic framework (MOF) database selection on the assessment of gas storage and separation potentials of MOFs
(Wiley, 2021-03-29) Dağlar, H.; Gulbalkan, H. C.; Avcı, G.; Aksu, G. O.; Altundal, O. F.; Altintas, C.; Fındıkçı, İlknur Eruçar; Keskin, S.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
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.
Open Access
Exploring covalent organic frameworks for H2S+CO2 separation from natural gas using efficient computational approaches
(Elsevier, 2022-08) Aksu, G. Ö.; Fındıkçı, İlknur Eruçar; Haslak, Z. P.; Keskin, S.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
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.
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, 2019-04-28) Altintas, C.; Avci, G.; Daglar, H.; Azar, A. N. V.; Fındıkçı, İlknur Eruçar; Velioglu, S.; Keskin, S.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
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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Facile synthesis of 2D Zn(II) coordination polymer and its crystal structure, selective removal of methylene blue and molecular simulations
(Elsevier, 2017) Sezer, G. G.; Yeşilel, O. Z.; Şahin, O.; Arslanoğlu, H.; Fındıkçı, İlknur Eruçar; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
A new coordination polymer {[Zn(μ3-ppda)(H2O)(μ-bpa)Zn(μ-ppda)(μ-bpa)]·4H2O}n (1) (ppda = 1,4-phenylenediacetate, bpa = 1,2-bis(4-pyridyl)ethane) has been synthesized by microwave-assisted reaction and characterized by elemental analysis, IR spectroscopy, single-crystal and powder X-ray diffractions. The asymmetric unit of 1 consists of two Zn(II) ions, two bpa ligands, two ppda ligands, one coordinated and four non-coordinated water molecules. In 1, ppda2− anions are linked the adjacent Zn(II) centers to generate 1D double-stranded chains. These chains are connected into 2D sheets by the bridging bpa ligands. Atomically detailed modeling was performed to compute single and binary component adsorption isotherms of H2, CO2, CH4 and N2 in complex 1. Results showed that 1 exhibits a high adsorption selectivity towards CO2 due to its high affinity for CO2. Results of this study will be helpful to guide the microwave-assisted reaction of coordination polymers to design promising adsorbents for gas storage and gas separation applications. The luminescent property of 1 and the selective removal of dyes in 1 have been also discussed. Results showed that 1 can be a potential candidate for luminescence applications and can selectively adsorb methylene blue (MB) dye molecules.
Open Access
Flux melting of metal–organic frameworks
(Royal Society of Chemistry, 2019-03-28) Longley, L.; Collins, S. M.; Li, S. C.; Smales, G. L.; Fındıkçı, İlknur Eruçar; Qiao, A.; Hou, J.; Doherty, C. M.; Thornton, A. W.; Hill, A. J.; Yu, X.; Terrill, N. J.; Smith, A. J.; Cohen, S. M.; Midgley, P. A.; Keen, D. A.; Telfer, S. G.; Bennett, T. D.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
Recent demonstrations of melting in the metal-organic framework (MOF) family have created interest in the interfacial domain between inorganic glasses and amorphous organic polymers. The chemical and physical behaviour of porous hybrid liquids and glasses is of particular interest, though opportunities are limited by the inaccessible melting temperatures of many MOFs. Here, we show that the processing technique of flux melting, borrowed' from the inorganic domain, may be applied in order to melt ZIF-8, a material which does not possess an accessible liquid state in the pure form. Effectively, we employ the high-temperature liquid state of one MOF as a solvent for a secondary, non-melting MOF component. Differential scanning calorimetry, small- and wide-angle X-ray scattering, electron microscopy and X-ray total scattering techniques are used to show the flux melting of the crystalline component within the liquid. Gas adsorption and positron annihilation lifetime spectroscopy measurements show that this results in enhanced, accessible porosity to a range of guest molecules in the resultant flux melted MOF glass.
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High-throughput computational screening of the metal organic framework database for CH4/H-2 separations
(American Chemical Society, 2018-01) Fındıkçı, İlknur Eruçar; Altıntaş, Ç.; Keskin, S.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
Metal organic frameworks (MOFs) have been considered as one of the most exciting porous materials discovered in the last decade. Large surface areas, high pore volumes, and tailorable pore sizes make MOFs highly promising in a variety of applications, mainly in gas separations. The number of MOFs has been increasing very rapidly, and experimental identification of materials exhibiting high gas separation potential is simply impractical. High throughput computational screening studies in which thousands of MOFs are evaluated to identify the best candidates for target gas separation is crucial in directing experimental efforts to the most useful materials. In this work, we used molecular simulations to screen the most complete and recent collection of MOFs from the Cambridge Structural Database to unlock their CH4/H-2 separation performances. This is the first study in the literature, which examines the potential of all existing MOFs for adsorption-based CH4/H-2 separation. MOFs (4350) were ranked based on several adsorbent evaluation metrics including selectivity, working capacity, adsorbent performance score, sorbent selection parameter, and regenerability. A large number of MOFs were identified to have extraordinarily large CH4/H-2 selectivities compared to traditional adsorbents such as zeolites and activated carbons. We examined the relations between structural properties of MOFs such as pore sizes, porosities, and surface areas and their selectivities. Correlations between the heat of adsorption, adsorbility, metal type of MOFs, and selectivities were also studied. On the basis of these relations, a simple mathematical model that can predict the CH4/H-2 selectivity of MOFs was suggested, which will be very useful in guiding the design and development of new MOFs with extraordinarily high CH4/H-2 separation performances.
Open Access
High-throughput molecular simulations of metal organic frameworks for co2 separation: opportunities and challenges
(Frontiers Media, 2018-02-02) Fındıkçı, İlknur Eruçar; Keskin, S.; Mechanical Engineering; Cao, D.; FINDIKÇI, Ilknur Eruçar
Metal organic frameworks (MOFs) have emerged as great alternatives to traditional nanoporous materials for CO2 separation applications. MOFs are porous materials that are formed by self-assembly of transition metals and organic ligands. The most important advantage of MOFs over well-known porous materials is the possibility to generate multiple materials with varying structural properties and chemical functionalities by changing the combination of metal centers and organic linkers during the synthesis. This leads to a large diversity of materials with various pore sizes and shapes that can be efficiently used for CO2 separations. Since the number of synthesized MOFs has already reached to several thousand, experimental investigation of each MOF at the lab-scale is not practical. High-throughput computational screening of MOFs is a great opportunity to identify the best materials for CO2 separation and to gain molecular-level insights into the structure-performance relationships. This type of knowledge can be used to design new materials with the desired structural features that can lead to extraordinarily high CO2 selectivities. In this mini-review, we focused on developments in high-throughput molecular simulations of MOFs for CO2 separations. After reviewing the current studies on this topic, we discussed the opportunities and challenges in the field and addressed the potential future developments.
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Hydrothermal synthesis and characterization of two dimensional coordination polymers with 2,2′-dimethylglutarate and 1,2-bis(imidazol-1-ylmethyl)benzene
(Elsevier, 2019-03-24) Yaman, P. K.; Erer, H.; Arici, M.; Fındıkçı, İlknur Eruçar; Yesilel, O. Z.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
The hydrothermal reactions of some metal ions with 2,2'-dimethylglutaric acid (22dmgH(2)) and 1,2-bis(imidazol-1-ylmethyl)benzene (obix) newly afford four coordination polymers are called, {[Co-2 (mu-22dmg)(2)(mu-obix)(2)]center dot 1.5H(2)O}(n) (1), {[Cu(mu-22dmg)(mu-obix)]center dot H2O}(n) (2), {[Zn-2(mu-22dmg)(2)(mu-obix)(2)]center dot 2H(2)O}(n) (3) and [Cd-2(mu-22dmg)(2)(mu-obix)(2)(H2O)](n) (4). All of the complexes were characterized by elemental analysis, IR spectra, single crystal X- ray diffraction, powder X-ray diffraction (PXRD), and thermal analysis techniques. Furthermore, photoluminescence and topological properties were studied. The X-ray single crystal study shows that complexes 1, 3 and 4 display 3-fold parallel interpenetrating networks with hcb topology showing an unusual 2D + 2D + 2D -> 2D structures. Topological analysis reveals that complex 2 has an uninodal 4-c net sql topology with the point symbol of 4(4).6(2). Atomically-detailed simulations were finally performed to compute hydrogen (H-2) uptake in these complexes at 77 K.
Open Access
Metal-organic framework glasses with permanent accessible porosity
(Nature Publishing Group, 2018-11-28) Zhou, C.; Longley, L.; Krajnc, A.; Smales, G. J.; Qiao, A.; Fındıkçı, İlknur Eruçar; Doherty, C. M.; Thornton, A. W.; Hill, A. J.; Ashling, C. W.; Qazvini, O. T.; Lee, S. J.; Chater, P. A.; Terrill, N. J.; Smith, A. J.; Yue, Y.; Mali, G.; Keen, D. A.; Telfer, S. G.; Bennett, T. D.; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar
To date, only several microporous, and even fewer nanoporous, glasses have been produced, always via post synthesis acid treatment of phase separated dense materials, e.g. Vycor glass. In contrast, high internal surface areas are readily achieved in crystalline materials, such as metal-organic frameworks (MOFs). It has recently been discovered that a new family of melt quenched glasses can be produced from MOFs, though they have thus far lacked the accessible and intrinsic porosity of their crystalline precursors. Here, we report the first glasses that are permanently and reversibly porous toward incoming gases, without post-synthetic treatment. We characterize the structure of these glasses using a range of experimental techniques, and demonstrate pores in the range of 4 – 8 Å. The discovery of MOF glasses with permanent accessible porosity reveals a new category of porous glass materials that are elevated beyond conventional inorganic and organic porous glasses by their diversity and tunability.

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