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Thermogravimetric Analysis of Moisture in Natural and Thermally Treated Clay Materials. MATERIALS (BASEL, SWITZERLAND) 2024; 17:2231. [PMID: 38793298 PMCID: PMC11123035 DOI: 10.3390/ma17102231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2024] [Revised: 04/30/2024] [Accepted: 05/07/2024] [Indexed: 05/26/2024]
Abstract
Clays are a class of porous materials; their surfaces are naturally covered by moisture. Weak thermal treatment may be considered practical to remove the water molecules, changing the surface properties and making the micro- and/or mesoporosities accessible to interact with other molecules. Herein, a modulated thermogravimetric analysis (MTGA) study of the moisture behavior on the structures of five, both fibrous and laminar, clay minerals is reported. The effect of the thermal treatment at 150 °C, which provokes the release of weakly adsorbed water molecules, was also investigated. The activation energies for the removal of the adsorbed water (Ea) were calculated, and they were found to be higher, namely, from 160 to 190 kJ mol-1, for fibrous clay minerals compared to lamellar structures, ranging in this latter case from 80 to 100 kJ mol-1. The thermal treatment enhances the rehydration in Na-montmorillonite, stevensite, and sepiolite structures with a decrease in the energy required to remove it, while Ea increases significantly in palygorskite (from 164 to 273 kJ mol-1). As a proof of concept, the MTGA results are statistically correlated, together with a full characterization of the physico-chemical properties of the five clay minerals, with the adsorption of two molecules, i.e., aflatoxin B1 (AFB1) and β-carotene. Herein, the amount of adsorbed molecules ranges from 12 to 97% for the former and from 22 to 35% for the latter, depending on the particular clay. The Ea was correlated with AFB1 adsorption with a Spearman score of -0.9. When the adsorbed water is forcibly removed, e.g., under vacuum conditions and high temperatures, the structure becomes the most important, decreasing the Spearman score between β-carotene and Ea to -0.6.
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Data-Driven Experimental Design of Rheological Clay–Polymer Composites. Ind Eng Chem Res 2022. [DOI: 10.1021/acs.iecr.2c00936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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3
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High-Performance Mg-Li Hybrid Batteries Based on Pseudocapacitive Anatase Ti 1-x Co x O 2-y Nanosheet Cathodes. CHEMSUSCHEM 2022; 15:e202102562. [PMID: 35060341 DOI: 10.1002/cssc.202102562] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 01/17/2022] [Indexed: 06/14/2023]
Abstract
Despite the proposed safety, performance, and cost advantages, practical implementation of Mg-Li hybrid batteries is limited due to the unavailability of reliable cathodes compatible with the dual-ion system. Herein, a high-performance Mg-Li dual ion battery based upon cobalt-doped TiO2 cathode was developed. Extremely pseudocapacitance-type Ti1-x Cox O2-y nanosheets consist of an optimum 3.57 % Co-atoms. This defective cathode delivered exceptional pseudocapacitance (maximum of 93 %), specific capacities (386 mAh g-1 at 25 mA g-1 ), rate performance (191 mAh g-1 at 1 A g-1 ), cyclability (3000 cycles at 1 A g-1 ), and coulombic efficiency (≈100 %) and fast charging (≈11 min). This performance was superior to the TiO2 -based Mg-Li dual-ion battery cathodes reported earlier. Mechanistic studies revealed dual-ion intercalation pseudocapacitance with negligible structural changes. Excellent electrochemical performance of the cation-doped TiO2 cathode was credited to the rapid pseudocapacitance-type Mg/Li-ion diffusion through the disorder generated by lattice distortions and oxygen vacancies. Ultrathin nature, large surface area, 2D morphology, and mesoporosity also contributed as secondary factors facilitating superior electrode-electrolyte interfacial kinetics. The demonstrated method of pseudocapacitance-type Mg-Li dual-ion intercalation by introducing lattice distortions/oxygen vacancies through selective doping can be utilized for the development of several other potential electrodes for high-performance Mg-Li dual-ion batteries.
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Machine-learning-accelerated multimodal characterization and multiobjective design optimization of natural porous materials. Chem Sci 2021; 12:9309-9317. [PMID: 34349900 PMCID: PMC8278955 DOI: 10.1039/d1sc00816a] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 06/01/2021] [Indexed: 12/02/2022] Open
Abstract
Natural porous materials such as nanoporous clays are used as green and low-cost adsorbents and catalysts. The key factors determining their performance in these applications are the pore morphology and surface activity, which are typically represented by properties such as specific surface area, pore volume, micropore content and pH. The latter may be modified and tuned to specific applications through material processing and/or chemical treatment. Characterization of the material, raw or processed, is typically performed experimentally, which can become costly especially in the context of tuning of the properties towards specific application requirements and needing numerous experiments. In this work, we present an application of tree-based machine learning methods trained on experimental datasets to accelerate the characterization of natural porous materials. The resulting models allow reliable prediction of the outcomes of experimental characterization of processed materials (R 2 from 0.78 to 0.99) as well as identification of key factors contributing to those properties through feature importance analysis. Furthermore, the high throughput of the models enables exploration of processing parameter-property correlations and multiobjective optimization of prototype materials towards specific applications. We have applied these methodologies to pinpoint and rationalize optimal processing conditions for clays exploitable in acid catalysis. One of such identified materials was synthesized and tested revealing appreciable acid character improvement with respect to the pristine material. Specifically, it achieved 79% removal of chlorophyll-a in acid catalyzed degradation.
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Machine learning using host/guest energy histograms to predict adsorption in metal-organic frameworks: Application to short alkanes and Xe/Kr mixtures. J Chem Phys 2021; 155:014701. [PMID: 34241399 DOI: 10.1063/5.0050823] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A machine learning (ML) methodology that uses a histogram of interaction energies has been applied to predict gas adsorption in metal-organic frameworks (MOFs) using results from atomistic grand canonical Monte Carlo (GCMC) simulations as training and test data. In this work, the method is first extended to binary mixtures of spherical species, in particular, Xe and Kr. In addition, it is shown that single-component adsorption of ethane and propane can be predicted in good agreement with GCMC simulation using a histogram of the adsorption energies felt by a methyl probe in conjunction with the random forest ML method. The results for propane can be improved by including a small number of MOF textural properties as descriptors. We also discuss the most significant features, which provides physical insight into the most beneficial adsorption energy sites for a given application.
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Fast and Accurate Machine Learning Strategy for Calculating Partial Atomic Charges in Metal-Organic Frameworks. J Chem Theory Comput 2021; 17:3052-3064. [PMID: 33739834 DOI: 10.1021/acs.jctc.0c01229] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Computational high-throughput screening using molecular simulations is a powerful tool for identifying top-performing metal-organic frameworks (MOFs) for gas storage and separation applications. Accurate partial atomic charges are often required to model the electrostatic interactions between the MOF and the adsorbate, especially when the adsorption involves molecules with dipole or quadrupole moments such as water and CO2. Although ab initio methods can be used to calculate accurate partial atomic charges, these methods are impractical for screening large material databases because of the high computational cost. We developed a random forest machine learning model to predict the partial atomic charges in MOFs using a small yet meaningful set of features that represent both the elemental properties and the local environment of each atom. The model was trained and tested on a collection of about 320 000 density-derived electrostatic and chemical (DDEC) atomic charges calculated on a subset of the Computation-Ready Experimental Metal-Organic Framework (CoRE MOF-2019) database and separately on charge model 5 (CM5) charges. The model predicts accurate atomic charges for MOFs at a fraction of the computational cost of periodic density functional theory (DFT) and is found to be transferable to other porous molecular crystals and zeolites. A strong correlation is observed between the partial atomic charge and the average electronegativity difference between the central atom and its bonded neighbors.
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Abstract
Our data-mining of crystalline molecular materials reveals the correlations between the molecular and crystalline porosity.
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Simultaneous Improvement of Mechanical and Fire-Safety Properties of Polymer Composites with Phosphonate-Loaded MOF Additives. ACS APPLIED MATERIALS & INTERFACES 2019; 11:20325-20332. [PMID: 31042349 DOI: 10.1021/acsami.9b02357] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Flame-retardant (FR) additives are commonly used to improve the fire safety of synthetic polymers, which are widely employed in manufactured consumer goods. Incorporation of an FR in a polymer typically leads to deterioration of its mechanical properties. It also manifests itself in non-negligible volatile organic compound (VOC) release, which in turn increases environmental risks carried by both the application and disposal of the corresponding consumer goods. Herein, we present a hierarchical strategy for the design of composite materials, which ensures simultaneous improvement of both mechanical and fire-safety properties of polymers while limiting the VOC release. Our strategy employs porous metal-organic framework (MOF) particles to provide a multifunctional interface between the FR molecules and the polymer. Specifically, we demonstrate that the particles of environmentally friendly HKUST-1 MOF can be infused by a modern FR-dimethyl methylphosphonate (DMMP)-and then embedded into widely used unsaturated polyesters. The DMMP-HKUST-1 additive endows the resulting composite material with improved processability, flame retardancy, and mechanical properties. Single-crystal X-ray diffraction, thermogravimetric analysis, and computational modeling of the additive suggest the complete pore filling of HKUST-1 with DMMP molecules being bound to the open metal sites of the MOF.
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9
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High-throughput assessment of hypothetical zeolite materials for their synthesizeability and industrial deployability. ACTA ACUST UNITED AC 2019. [DOI: 10.1515/zkri-2018-2155] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Abstract
Zeolites are important microporous framework materials, where 200+ structures are known to exist and many millions so-called hypothetical materials can be computationally created. Here, we screen the “Deem” database of hypothetical zeolite structures to find experimentally feasible and industrially relevant materials. We use established and existing criteria and structure descriptors (lattice energy, local interatomic distances, TTT angles), and we develop new criteria which are based on 5-th neighbor distances to T-atoms, tetrahedral order parameters (or, tetrahedrality), and porosity and channel dimensionality. Our filter funnel for screening the most attractive zeolite materials that we construct consists of nine different types of criteria and a total of 53 subcriteria. The funnel reduces the pool of candidate materials from initially >300,000 to 70 and 33, respectively, depending on the channel dimensionality constraint applied (2- and 3-dimensional vs. only 3-dimensional channels). We find that it is critically important to define longer range and more stringent criteria such as the new 5-th neighbor distances to T-atoms and the tetrahedrality descriptor in order to succeed in reducing the huge pool of candidates to a manageable number. Apart from four experimentally achieved structures (BEC, BOG, ISV, SSF), all other candidates are hypothetical frameworks, thus, representing most valuable targets for synthesis and application. Detailed analysis of the screening data allowed us to also propose an exciting future direction how such screening studies as ours could be improved and how framework generating algorithms could be competitively optimized.
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Capturing chemical intuition in synthesis of metal-organic frameworks. Nat Commun 2019; 10:539. [PMID: 30710082 PMCID: PMC6358622 DOI: 10.1038/s41467-019-08483-9] [Citation(s) in RCA: 93] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 01/07/2019] [Indexed: 12/21/2022] Open
Abstract
We report a methodology using machine learning to capture chemical intuition from a set of (partially) failed attempts to synthesize a metal-organic framework. We define chemical intuition as the collection of unwritten guidelines used by synthetic chemists to find the right synthesis conditions. As (partially) failed experiments usually remain unreported, we have reconstructed a typical track of failed experiments in a successful search for finding the optimal synthesis conditions that yields HKUST-1 with the highest surface area reported to date. We illustrate the importance of quantifying this chemical intuition for the synthesis of novel materials. Synthetic chemists develop a "chemical intuition" over years of experience in the lab. Here the authors combine machine learning of (partially) failed experiments with robotic synthesis to capture this intuition used in searching for the optimal synthesis conditions of metal-organic frameworks.
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Abstract
The emerging advanced porous materials, e.g. extended framework materials and porous molecular materials, offer an unprecedented level of control of their structure and function. The enormous possibilities for tuning these materials by changing their building blocks mean that, in principle, optimally performing materials for a variety of applications can be systematically designed. However, the process of finding a set of optimal structures for a given application requires computational high-throughput tools to analyze and sieve through many candidate materials. In particular, in the case of porous molecular materials, the analysis and selection of a molecule is one of the key aspects as the structure of the molecule determines the structure of the resulting material, and very often the porosity of the molecule significantly contributes to the porous properties of the resulting material. In this work, we introduce definitions and algorithms to characterize porosity at the molecular level, along with a software implementation of these algorithms. We demonstrate applications of the software tool in the discovery and characterization of porous molecules among ca. 94 million molecules currently enlisted in the PubChem database.
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12
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13
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Cutting Materials in Half: A Graph Theory Approach for Generating Crystal Surfaces and Its Prediction of 2D Zeolites. ACS CENTRAL SCIENCE 2018. [PMID: 29532024 PMCID: PMC5832999 DOI: 10.1021/acscentsci.7b00555] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Scientific interest in two-dimensional (2D) materials, ranging from graphene and other single layer materials to atomically thin crystals, is quickly increasing for a large variety of technological applications. While in silico design approaches have made a large impact in the study of 3D crystals, algorithms designed to discover atomically thin 2D materials from their parent 3D materials are by comparison more sparse. We hypothesize that determining how to cut a 3D material in half (i.e., which Miller surface is formed) by severing a minimal number of bonds or a minimal amount of total bond energy per unit area can yield insight into preferred crystal faces. We answer this question by implementing a graph theory technique to mathematically formalize the enumeration of minimum cut surfaces of crystals. While the algorithm is generally applicable to different classes of materials, we focus on zeolitic materials due to their diverse structural topology and because 2D zeolites have promising catalytic and separation performance compared to their 3D counterparts. We report here a simple descriptor based only on structural information that predicts whether a zeolite is likely to be synthesizable in the 2D form and correctly identifies the expressed surface in known layered 2D zeolites. The discovery of this descriptor allows us to highlight other zeolites that may also be synthesized in the 2D form that have not been experimentally realized yet. Finally, our method is general since the mathematical formalism can be applied to find the minimum cut surfaces of other crystallographic materials such as metal-organic frameworks, covalent-organic frameworks, zeolitic-imidazolate frameworks, metal oxides, etc.
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Electrostatic Estimation of Intercalant Jump-Diffusion Barriers Using Finite-Size Ion Models. J Phys Chem Lett 2018; 9:628-634. [PMID: 29320200 DOI: 10.1021/acs.jpclett.7b03199] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We report on a scheme for estimating intercalant jump-diffusion barriers that are typically obtained from demanding density functional theory-nudged elastic band calculations. The key idea is to relax a chain of states in the field of the electrostatic potential that is averaged over a spherical volume using different finite-size ion models. For magnesium migrating in typical intercalation materials such as transition-metal oxides, we find that the optimal model is a relatively large shell. This data-driven result parallels typical assumptions made in models based on Onsager's reaction field theory to quantitatively estimate electrostatic solvent effects. Because of its efficiency, our potential of electrostatics-finite ion size (PfEFIS) barrier estimation scheme will enable rapid identification of materials with good ionic mobility.
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Accurate Characterization of the Pore Volume in Microporous Crystalline Materials. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:14529-14538. [PMID: 28636815 PMCID: PMC5745516 DOI: 10.1021/acs.langmuir.7b01682] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 06/20/2017] [Indexed: 05/19/2023]
Abstract
Pore volume is one of the main properties for the characterization of microporous crystals. It is experimentally measurable, and it can also be obtained from the refined unit cell by a number of computational techniques. In this work, we assess the accuracy and the discrepancies between the different computational methods which are commonly used for this purpose, i.e, geometric, helium, and probe center pore volumes, by studying a database of more than 5000 frameworks. We developed a new technique to fully characterize the internal void of a microporous material and to compute the probe-accessible and -occupiable pore volume. We show that, unlike the other definitions of pore volume, the occupiable pore volume can be directly related to the experimentally measured pore volumes from nitrogen isotherms.
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Computationally-Guided Synthetic Control over Pore Size in Isostructural Porous Organic Cages. ACS CENTRAL SCIENCE 2017; 3:734-742. [PMID: 28776015 PMCID: PMC5532722 DOI: 10.1021/acscentsci.7b00145] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Indexed: 05/28/2023]
Abstract
The physical properties of 3-D porous solids are defined by their molecular geometry. Hence, precise control of pore size, pore shape, and pore connectivity are needed to tailor them for specific applications. However, for porous molecular crystals, the modification of pore size by adding pore-blocking groups can also affect crystal packing in an unpredictable way. This precludes strategies adopted for isoreticular metal-organic frameworks, where addition of a small group, such as a methyl group, does not affect the basic framework topology. Here, we narrow the pore size of a cage molecule, CC3, in a systematic way by introducing methyl groups into the cage windows. Computational crystal structure prediction was used to anticipate the packing preferences of two homochiral methylated cages, CC14-R and CC15-R, and to assess the structure-energy landscape of a CC15-R/CC3-S cocrystal, designed such that both component cages could be directed to pack with a 3-D, interconnected pore structure. The experimental gas sorption properties of these three cage systems agree well with physical properties predicted by computational energy-structure-function maps.
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17
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Xenon Recovery at Room Temperature using Metal-Organic Frameworks. Chemistry 2017; 23:10758-10762. [PMID: 28612499 DOI: 10.1002/chem.201702668] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Indexed: 11/10/2022]
Abstract
Xenon is known to be a very efficient anesthetic gas, but its cost prohibits the wider use in medical industry and other potential applications. It has been shown that Xe recovery and recycling from anesthetic gas mixtures can significantly reduce its cost as anesthetic. The current technology uses series of adsorbent columns followed by low-temperature distillation to recover Xe; this method is expensive to use in medical facilities. Herein, we propose a much simpler and more efficient system to recover and recycle Xe from exhaled anesthetic gas mixtures at room temperature using metal-organic frameworks (MOFs). Among the MOFs tested, PCN-12 exhibits unprecedented performance with high Xe capacity and Xe/O2 , Xe/N2 and Xe/CO2 selectivity at room temperature. The in situ synchrotron measurements suggest that Xe is occupies the small pockets of PCN-12 compared to unsaturated metal centers (UMCs). Computational modeling of adsorption further supports our experimental observation of Xe binding sites in PCN-12.
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Materials Genome in Action: Identifying the Performance Limits of Physical Hydrogen Storage. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2017; 29:2844-2854. [PMID: 28413259 PMCID: PMC5390509 DOI: 10.1021/acs.chemmater.6b04933] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 03/06/2017] [Indexed: 05/29/2023]
Abstract
The Materials Genome is in action: the molecular codes for millions of materials have been sequenced, predictive models have been developed, and now the challenge of hydrogen storage is targeted. Renewably generated hydrogen is an attractive transportation fuel with zero carbon emissions, but its storage remains a significant challenge. Nanoporous adsorbents have shown promising physical adsorption of hydrogen approaching targeted capacities, but the scope of studies has remained limited. Here the Nanoporous Materials Genome, containing over 850 000 materials, is analyzed with a variety of computational tools to explore the limits of hydrogen storage. Optimal features that maximize net capacity at room temperature include pore sizes of around 6 Å and void fractions of 0.1, while at cryogenic temperatures pore sizes of 10 Å and void fractions of 0.5 are optimal. Our top candidates are found to be commercially attractive as "cryo-adsorbents", with promising storage capacities at 77 K and 100 bar with 30% enhancement to 40 g/L, a promising alternative to liquefaction at 20 K and compression at 700 bar.
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Abstract
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For applications of metal–organic
frameworks (MOFs) such
as gas storage and separation, flexibility is often seen as a parameter
that can tune material performance. In this work we aim to determine
the optimal flexibility for the shape selective separation of similarly
sized molecules (e.g., Xe/Kr mixtures). To obtain systematic insight
into how the flexibility impacts this type of separation, we develop
a simple analytical model that predicts a material’s Henry
regime adsorption and selectivity as a function of flexibility. We
elucidate the complex dependence of selectivity on a framework’s
intrinsic flexibility whereby performance is either improved or reduced
with increasing flexibility, depending on the material’s pore
size characteristics. However, the selectivity of a material with
the pore size and chemistry that already maximizes selectivity in
the rigid approximation is continuously diminished with increasing
flexibility, demonstrating that the globally optimal separation exists
within an entirely rigid pore. Molecular simulations show that our
simple model predicts performance trends that are observed when screening
the adsorption behavior of flexible MOFs. These flexible simulations
provide better agreement with experimental adsorption data in a high-performance
material that is not captured when modeling this framework as rigid,
an approximation typically made in high-throughput screening studies.
We conclude that, for shape selective adsorption applications, the globally optimal material will have the optimal pore size/chemistry and minimal intrinsic flexibility even though other nonoptimal
materials’ selectivity can actually be improved by flexibility.
Equally important, we find that flexible simulations can be critical
for correctly modeling adsorption in these types of systems.
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Modeling adsorption of brominated, chlorinated and mixed bromo/chloro-dibenzo- p-dioxins on C 60 fullerene using Nano-QSPR. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2017; 8:752-761. [PMID: 28487818 PMCID: PMC5389196 DOI: 10.3762/bjnano.8.78] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 03/14/2017] [Indexed: 06/07/2023]
Abstract
Many technological implementations in the field of nanotechnology have involved carbon nanomaterials, including fullerenes such as the buckminsterfullerene, C60. The unprecedented properties of such organic nanomaterials (in particular their large surface area) gained extensive attention for their potential use as organic pollutant sorbents. Sorption interactions can be very hazardous and useful at the same time. This work investigates the influence of halogenation by bromine and/or chlorine in dibenzo-p-dioxins on their sorption ability on the C60 fullerene surface. Halogenated dibenzo-p-dioxins (PXDDs, where X = Br or Cl) are ever-present in the environment and accidently produced in many technological processes in only approximately known quantities. If all combinatorial Br and/or Cl dioxin substitution possibilities are present in the environment, the experimental characterization and investigation of sorbent effectiveness is more than difficult. In this work, we have developed a quantitative structure-property relationship (QSPR) model (R2 = 0.998), predicting the adsorption energy [kcal/mol] for 1,701 PXDDs adsorbed on C60 (PXDD@C60). Based on the QSPR model reported herein, we concluded that the lowest energy PXDD@C60 complexes are those that the World Health Organization (WHO) considers to be less dangerous with respect to the aryl hydrocarbon receptor (AhR) toxicity mechanism. Therefore, the effectiveness of fullerenes as sorbent agents may be underestimated as sorption could be less effective for toxic congeners than previously believed.
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Impact of the strength and spatial distribution of adsorption sites on methane deliverable capacity in nanoporous materials. Chem Eng Sci 2017. [DOI: 10.1016/j.ces.2016.02.030] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Rational Design of a Low-Cost, High-Performance Metal-Organic Framework for Hydrogen Storage and Carbon Capture. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2017; 121:1171-1181. [PMID: 28127415 PMCID: PMC5253711 DOI: 10.1021/acs.jpcc.6b10363] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 12/16/2016] [Indexed: 06/06/2023]
Abstract
We present the in silico design of a MOF-74 analogue, hereon known as M2(DHFUMA) [M = Mg, Fe, Co, Ni, Zn], with enhanced small-molecule adsorption properties over the original M2(DOBDC) series. Constructed from 2,3-dihydroxyfumarate (DHFUMA), an aliphatic ligand which is smaller than the aromatic 2,5-dioxidobenzene-1,4-dicarboxylate (DOBDC), the M2(DHFUMA) framework has a reduced channel diameter, resulting in higher volumetric density of open metal sites and significantly improved volumetric hydrogen (H2) storage potential. Furthermore, the reduced distance between two adjacent open metal sites in the pore channel leads to a CO2 binding mode of one molecule per two adjacent metals with markedly stronger binding energetics. Through dispersion-corrected density functional theory (DFT) calculations of guest-framework interactions and classical simulation of the adsorption behavior of binary CO2:H2O mixtures, we theoretically predict the M2(DHFUMA) series as an improved alternative for carbon capture over the M2(DOBDC) series when adsorbing from wet flue gas streams. The improved CO2 uptake and humidity tolerance in our simulations is tunable based upon metal selection and adsorption temperature which, combined with the significantly reduced ligand expense, elevates this material's potential for CO2 capture and H2 storage. The dynamical and elastic stabilities of Mg2(DHFUMA) were verified by hybrid DFT calculations, demonstrating its significant potential for experimental synthesis.
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Abstract
A chemical modification of a molecular belt (M1) renders the molecule (M2) into a stable supramolecular nanotube porous crystal.
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In silico design and screening of hypothetical MOF-74 analogs and their experimental synthesis. Chem Sci 2016; 7:6263-6272. [PMID: 30034767 PMCID: PMC6024208 DOI: 10.1039/c6sc01477a] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 06/21/2016] [Indexed: 12/26/2022] Open
Abstract
We present the in silico design of MOFs exhibiting 1-dimensional rod topologies by enumerating MOF-74-type analogs based on the PubChem Compounds database. We simulate the adsorption behavior of CO2 in the generated analogs and experimentally validate a novel MOF-74 analog, Mg2(olsalazine).
In this work we present the in silico design of metal-organic frameworks (MOFs) exhibiting 1-dimensional rod topologies. We introduce an algorithm for construction of this family of MOF topologies, and illustrate its application for enumerating MOF-74-type analogs. Furthermore, we perform a broad search for new linkers that satisfy the topological requirements of MOF-74 and consider the largest database of known chemical space for organic compounds, the PubChem database. Our in silico crystal assembly, when combined with dispersion-corrected density functional theory (DFT) calculations, is demonstrated to generate a hypothetical library of open-metal site containing MOF-74 analogs in the 1-D rod topology from which we can simulate the adsorption behavior of CO2. We finally conclude that these hypothetical structures have synthesizable potential through computational identification and experimental validation of a novel MOF-74 analog, Mg2(olsalazine).
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Metal-organic framework with optimally selective xenon adsorption and separation. Nat Commun 2016; 7:ncomms11831. [PMID: 27291101 PMCID: PMC4909987 DOI: 10.1038/ncomms11831] [Citation(s) in RCA: 202] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 05/04/2016] [Indexed: 12/22/2022] Open
Abstract
Nuclear energy is among the most viable alternatives to our current fossil fuel-based energy economy. The mass deployment of nuclear energy as a low-emissions source requires the reprocessing of used nuclear fuel to recover fissile materials and mitigate radioactive waste. A major concern with reprocessing used nuclear fuel is the release of volatile radionuclides such as xenon and krypton that evolve into reprocessing facility off-gas in parts per million concentrations. The existing technology to remove these radioactive noble gases is a costly cryogenic distillation; alternatively, porous materials such as metal–organic frameworks have demonstrated the ability to selectively adsorb xenon and krypton at ambient conditions. Here we carry out a high-throughput computational screening of large databases of metal–organic frameworks and identify SBMOF-1 as the most selective for xenon. We affirm this prediction and report that SBMOF-1 exhibits by far the highest reported xenon adsorption capacity and a remarkable Xe/Kr selectivity under conditions pertinent to nuclear fuel reprocessing. Increased nuclear energy usage requires the reprocessing of used nuclear fuel to recover radioactive waste, including xenon. Here, the authors perform high-throughput computational screening to identify a metal-organic framework with high xenon selectivity, and demonstrate this with performance analysis.
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Towards accurate porosity descriptors based on guest-host interactions. J Mol Graph Model 2016; 66:91-8. [PMID: 27054971 DOI: 10.1016/j.jmgm.2016.03.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 03/23/2016] [Accepted: 03/23/2016] [Indexed: 10/22/2022]
Abstract
For nanoporous materials at the characterization level, geometry-based approaches have become the methods of choice to provide information, often encoded in numerical descriptors, about the pores and the channels of a porous material. Examples of most common descriptors of the latter are pore limiting diameters, accessible surface area and accessible volume. The geometry-based methods exploit hard-sphere approximation for atoms, which (1) reduces costly computations of the interatomic interactions between the probe guest molecule and the porous material framework atoms, (2) effectively exploit applied mathematics methods such as Voronoi decomposition to represent and characterize porosity. In this work, we revisit and quantify the shortcoming of the geometry-based approaches. To do so, we have developed a series of algorithms to calculate pore descriptors such as void fraction, accessible surface area, pore limiting diameters (largest included sphere, and largest free sphere) based on a classical force field model of interactions between the guest and the framework atoms. Our resulting energy-based methods are tested on diverse sets of metal-organic frameworks and zeolite structures and comparisons against results obtained from geometric-based method indicate deviations in the cases for structures with small pore sizes. The method provides both high accuracy and performance making it suitable when screening a large database of materials.
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In silico prediction of MOFs with high deliverable capacity or internal surface area. Phys Chem Chem Phys 2016; 17:11962-73. [PMID: 25716343 DOI: 10.1039/c5cp00002e] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Metal-organic frameworks (MOFs) offer unprecedented atom-scale design and structural tunability, largely due to the vast number of possible organic linkers which can be utilized in their assembly. Exploration of this space of linkers allows identification of ranges of achievable material properties as well as discovery of optimal materials for a given application. Experimental exploration of the linker space has to date been quite limited due to the cost and complexity of synthesis, while high-throughput computational studies have mainly explored MOF materials based on known or readily available linkers. Here an evolutionary algorithm for de novo design of organic linkers for metal-organic frameworks is used to predict MOFs with either high methane deliverable capacity or methane accessible surface area. Known chemical reactions are applied in silico to a population of linkers to discover these MOFs. Through this design strategy, MOF candidates are found in the ten symmetric networks acs, cds, dia, hxg, lvt, nbo, pcu, rhr, sod, and tbo. The correlation between deliverable capacities and surface area is network dependent.
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Comparing gas separation performance between all known zeolites and their zeolitic imidazolate framework counterparts. Dalton Trans 2016; 45:216-25. [DOI: 10.1039/c5dt04012d] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Candidate structures for environmental and industrial gas separations. No correlation between zeolites and their respective Zeolitic Imidazolate framework counterparts.
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Understanding Small-Molecule Interactions in Metal-Organic Frameworks: Coupling Experiment with Theory. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:5785-5796. [PMID: 26033176 DOI: 10.1002/adma.201500966] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 04/29/2015] [Indexed: 06/04/2023]
Abstract
Metal-organic frameworks (MOFs) have gained much attention as next-generation porous media for various applications, especially gas separation/storage, and catalysis. New MOFs are regularly reported; however, to develop better materials in a timely manner for specific applications, the interactions between guest molecules and the internal surface of the framework must first be understood. A combined experimental and theoretical approach is presented, which proves essential for the elucidation of small-molecule interactions in a model MOF system known as M2 (dobdc) (dobdc(4-) = 2,5-dioxido-1,4-benzenedicarboxylate; M = Mg, Mn, Fe, Co, Ni, Cu, or Zn), a material whose adsorption properties can be readily tuned via chemical substitution. It is additionally shown that the study of extensive families like this one can provide a platform to test the efficacy and accuracy of developing computational methodologies in slightly varying chemical environments, a task that is necessary for their evolution into viable, robust tools for screening large numbers of materials.
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Systematic Tuning and Multifunctionalization of Covalent Organic Polymers for Enhanced Carbon Capture. J Am Chem Soc 2015; 137:13301-7. [DOI: 10.1021/jacs.5b06266] [Citation(s) in RCA: 179] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Erratum: Corrigendum: Kinetically tuned dimensional augmentation as a versatile synthetic route towards robust metal–organic frameworks. Nat Commun 2015; 6:6106. [DOI: 10.1038/ncomms7106] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Abstract
Computational search of structure database for CO2 reduction catalysts using molecular simulation and machine learning.
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Branched isomeric 1,2,3-triazolium-based ionic liquids: new insight into structure–property relationships. Phys Chem Chem Phys 2015; 17:29834-43. [DOI: 10.1039/c5cp04756k] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Series of branched isomeric 1,2,3-triazolium-based ionic liquids (ILs) were synthesized and characterized. The effect of branching on thermal and physical properties is investigated.
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Kinetically tuned dimensional augmentation as a versatile synthetic route towards robust metal–organic frameworks. Nat Commun 2014; 5:5723. [DOI: 10.1038/ncomms6723] [Citation(s) in RCA: 270] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 10/31/2014] [Indexed: 01/07/2023] Open
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Toward a Materials Genome Approach for Ionic Liquids: Synthesis Guided by Ab Initio Property Maps. J Phys Chem B 2014; 118:13609-20. [DOI: 10.1021/jp506972w] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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Exploring frontiers of crystalline porous materials. Acta Crystallogr A Found Adv 2014. [DOI: 10.1107/s205327331408379x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023] Open
Abstract
We present a computational framework for the rapid identification and characterization of high surface area materials from within the vast chemical space of crystalline porous materials such as metal-organic frameworks (MOFs) or covalent organic frameworks (COFs). MOFs and COFs have been the subject of intense research interest due largely to their highly tunable structural properties and record-breaking internal surface areas; gravimetric surface area is one of the most addressed properties of porous materials, and has seen improvement by approximately a factor of twenty since the first reports. However, the design of MOFs with optimum chemical and geometrical properties remains a great challenge, due to the vast combinatorial space of building blocks and topologies in which they can be arranged. Efforts to identify high-performance materials have involved trial-and-error, observation-based design, computational enumeration and screening of large combinatorial libraries as well as optimization-based approaches. In our presentation, we will give an overview of techniques under development in our group, in particular, algorithms for 3D structure model assembly and material characterization. We will also present how these tools can be employed in both enumeration and optimization-based discovery of novel materials.
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Abstract
Methane can be an alternative fuel for vehicular usage provided that new porous materials are developed for its efficient adsorption-based storage. Herein, we search for materials for this application within the family of diamond analogues. We used density functional theory to investigate structures in which tetrahedral C atoms of diamond are separated by -CC- or -BN- groups, as well as ones involving substitution of tetrahedral C atoms with Si and Ge atoms. The adsorptive and diffusive properties of methane are studied using classical molecular simulations. Our results suggest that the all-carbon structure has the highest volumetric methane uptake of 280 VSTP/V at p = 35 bar and T = 298 K. However, it suffers from limited methane diffusion. Alternatively, the considered Si and Ge-containing analogies have fast diffusive properties but their adsorption is lower, ca. 172-179 VSTP/V, at the same conditions.
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Communication: Remarkable electrophilicity of the oxalic acid monomer: An anion photoelectron spectroscopy and theoretical study. J Chem Phys 2014; 140:221103. [DOI: 10.1063/1.4882655] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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In silico design of porous polymer networks: high-throughput screening for methane storage materials. J Am Chem Soc 2014; 136:5006-22. [PMID: 24611543 DOI: 10.1021/ja4123939] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Porous polymer networks (PPNs) are a class of advanced porous materials that combine the advantages of cheap and stable polymers with the high surface areas and tunable chemistry of metal-organic frameworks. They are of particular interest for gas separation or storage applications, for instance, as methane adsorbents for a vehicular natural gas tank or other portable applications. PPNs are self-assembled from distinct building units; here, we utilize commercially available chemical fragments and two experimentally known synthetic routes to design in silico a large database of synthetically realistic PPN materials. All structures from our database of 18,000 materials have been relaxed with semiempirical electronic structure methods and characterized with Grand-canonical Monte Carlo simulations for methane uptake and deliverable (working) capacity. A number of novel structure-property relationships that govern methane storage performance were identified. The relationships are translated into experimental guidelines to realize the ideal PPN structure. We found that cooperative methane-methane attractions were present in all of the best-performing materials, highlighting the importance of guest interaction in the design of optimal materials for methane storage.
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Zeolite screening for the separation of gas mixtures containing SO2, CO2and CO. Phys Chem Chem Phys 2014; 16:19884-93. [DOI: 10.1039/c4cp00109e] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Abstract
In this work, we address the question of which thermodynamic factors determine the deliverable capacity of methane in nanoporous materials. The deliverable capacity is one of the key factors that determines the performance of a material for methane storage in automotive fuel tanks. To obtain insights into how the molecular characteristics of a material are related to the deliverable capacity, we developed several statistical thermodynamic models. The predictions of these models are compared with the classical thermodynamics approach of Bhatia and Myers [Bhatia and Myers, Langmuir, 2005, 22, 1688] and with the results of molecular simulations in which we screen the International Zeolite Association (IZA) structure database and a hypothetical zeolite database of over 100,000 structures. Both the simulations and our models do not support the rule of thumb that, for methane storage, one should aim for an optimal heat of adsorption of 18.8 kJ mol(-1). Instead, our models show that one can identify an optimal heat of adsorption, but that this optimal heat of adsorption depends on the structure of the material and can range from 8 to 23 kJ mol(-1). The different models we have developed are aimed to determine how this optimal heat of adsorption is related to the molecular structure of the material.
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Molecular Dynamics Simulations of Gas Selectivity in Amorphous Porous Molecular Solids. J Am Chem Soc 2013; 135:17818-30. [DOI: 10.1021/ja407374k] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Discovery of Most Stable Structures of Neutral and Anionic Phenylalanine through Automated Scanning of Tautomeric and Conformational Spaces. J Chem Theory Comput 2013; 9:4374-81. [PMID: 26589154 DOI: 10.1021/ct400531a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We have developed a software tool for combinatorial generation of tautomers and conformers of small molecules. We have demonstrated it by performing a systematic search for the most stable structures of neutral and anionic phenylalanine (Phe) using electronic structure methods. For the neutral canonical tautomer we found out that the conformers with and without the intramolecular (O)H···NH2 hydrogen bond are similarly stable, within the error bars of our method. A unique IR signature of the conformer without the hydrogen bond has been identified. We also considered anions of Phe, both valence type and dipole-bound. We have found out that tautomers resulting from proton transfer from the carboxylic OH to the phenyl ring do support valence anions that are vertically strongly bound, with electron vertical detachment energies (VDE) in a range of 3.2-3.5 eV. The most stable conformer of these valence anions remains adiabatically unbound with respect to the canonical neutral by only 2.17 kcal/mol at the CCSD(T)/aug-cc-pVDZ level. On the basis of our past experience with valence anions of nucleic acid bases, we suggest that the valence anions of Phe identified in this report can be observed experimentally. The most stable conformer of canonical Phe is characterized by an adiabatic electron affinity of 53 meV (a dipole-bound state).
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Understanding the effect of side groups in ionic liquids on carbon-capture properties: a combined experimental and theoretical effort. Phys Chem Chem Phys 2013; 15:3264-72. [DOI: 10.1039/c3cp43923b] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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