Nucleation of zeolitic imidazolate frameworks: from molecules to nanoparticles.

We have studied the clusters involved in the initial stages of nucleation of Zeolitic Imidazolate Frameworks, employing a wide range of computational techniques. In the pre-nucleating solution, the prevalent cluster is the ZnIm cluster (formed by a zinc cation, Zn, and four imidazolate anions, Im), although clusters such as ZnIm, ZnIm, ZnIm, ZnIm, ZnIm, or ZnIm have energies that are not much higher, so they would also be present in solution at appreciable quantities. All these species, except ZnIm, have a tetrahedrally coordinated Zn cation.

Incorporating zeolitic-imidazolate framework-8 nanoparticles into kidney scaffolds: a first step towards innovative renal therapies.

We demonstrate for the first time the potential of zeolitic-imidazolate framework-8 nanoparticles to be incorporated within a renal scaffold while retaining their ability to remove uremic toxins (mainly hydrophobic toxins like -cresol) under flow conditions. This work may pave the way for the future development of novel adsorbents for dialysis and/or artificial kidneys.

Unravelling the key factors in the chlorine-promoted epoxidation of ethylene over a silver-copper oxide nanocatalyst.

Ethylene oxide is one of the most important raw materials in the chemical industry, with an annual production close to 35 million metric tons. Despite its importance, to date, no metal has been found that can compete with the original silver bulk material catalyst discovered in 1931. Recently, a few copper and copper-silver based nanostructures have demonstrated remarkable selectivity and activity, especially when coupled with an industrial chlorine promoter.

COVID-19 and unpaid leave: Impacts of psychological contract breach on organizational distrust and turnover intention: Mediating role of emotional exhaustion.

This study examines the influence of COVID-19 on unpaid leave, the direct impacts of psychological contract breach on organizational distrust and turnover intention, and their indirect impact through emotional exhaustion. The study used partial least squares to analyze the data set of 238 questionnaires from hospitality establishments. Results indicate a significant direct positive impact of psychological contract breach on organizational distrust and favorable indirect effects through emotional exhaustion.

Bandgap Engineering in the Configurational Space of Solid Solutions via Machine Learning: (Mg,Zn)O Case Study.

Computer simulations of alloys' properties often require calculations in a large space of configurations in a supercell of the crystal structure. A common approach is to map density functional theory results into a simplified interaction model using so-called cluster expansions, which are linear on the cluster correlation functions. Alternative descriptors have not been sufficiently explored so far.

Role of Ionic Liquid [EMIM][SCN] in the Adsorption and Diffusion of Gases in Metal-Organic Frameworks.

We study the adsorption performance of metal-organic frameworks (MOFs) impregnated of ionic liquids (ILs). To this aim we calculated adsorption and diffusion of light gases (CO, CH, N) and their mixtures in hybrid composites using molecular simulations. The hybrid composites consist of 1-ethyl-3-methylimidazolium thiocyanate impregnated in IRMOF-1, HMOF-1, MIL-47, and MOF-1.

Fitting electron density as a physically sound basis for the development of interatomic potentials of complex alloys.

The development of new interatomic potentials to model metallic systems is a difficult task, due in part to the dependence between the parameters that describe the electron density and the short-range interactions. Parameter search methods are prone to false convergence. To solve this problem, we have developed a methodology for obtaining the electron density parameters independently of the short-range interactions, so that physically sound parameters can be obtained to describe the electron density, after which the short-range parameters can be fitted, thus reducing the complexity of the process and yielding better interatomic potentials.

Molecular Dynamics Analysis of Charge Transport in Ionic-Liquid Electrolytes Containing Added Salt with Mono, Di, and Trivalent Metal Cations.

Among many other applications, room-temperature ionic liquids (ILs) are used as electrolytes for storage and energy-conversion devices. In this work, we investigate, at the microscopic level, the structural and dynamical properties of 1-methyl-1-butyl-pyrrolidinium bis(trifluoromethanesulfonyl) imide [C PYR] [Tf N] IL-based electrolytes for metal-ion batteries. We carried out molecular dynamics simulations of electrolytes mainly composed of [C PYR] [Tf N] IL with the addition of M -[Tf N] metal salts (M=Li , Na , Ni , Zn , Co , Cd , and Al , n=1, 2, and 3) dissolved in the IL.

Selective sulfur dioxide adsorption on crystal defect sites on an isoreticular metal organic framework series.

The widespread emissions of toxic gases from fossil fuel combustion represent major welfare risks. Here we report the improvement of the selective sulfur dioxide capture from flue gas emissions of isoreticular nickel pyrazolate metal organic frameworks through the sequential introduction of missing-linker defects and extra-framework barium cations. The results and feasibility of the defect pore engineering carried out are quantified through a combination of dynamic adsorption experiments, X-ray diffraction, electron microscopy and density functional theory calculations.

Controlling Thermal Expansion: A Metal-Organic Frameworks Route.

Controlling thermal expansion is an important, not yet resolved, and challenging problem in materials research. A conceptual design is introduced here, for the first time, for the use of metal-organic frameworks (MOFs) as platforms for controlling thermal expansion devices that can operate in the negative, zero, and positive expansion regimes. A detailed computer simulation study, based on molecular dynamics, is presented to support the targeted application.

Electrochemical Reduction of Oxygen in Aprotic Ionic Liquids Containing Metal Cations: A Case Study on the Na-O system.

Metal-air batteries are intensively studied because of their high theoretical energy-storage capability. However, the fundamental science of electrodes, electrolytes, and reaction products still needs to be better understood. In this work, the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) was chosen to study the influence of a wide range of metal cations (M ) on the electrochemical behavior of oxygen.

On the ionophoric selectivity of nonactin and related macrotetrolide derivatives.

Nonactin and its analogs constitute a central class of macrocycles with an antibiotic activity closely related to their selective ionophoric behavior. In this study, we apply experimental and computational methods to revisit the specificity of cation binding and transport by three nactin variants differing in structural properties, such as the position of the ester linkages, the nature of the side groups, or the flexibility of the backbone. On the one hand, electrospray ionization mass spectrometry and infrared spectroscopy are employed to expose the selectivity of the liquid-liquid (water-chloroform) extraction of alkali cations by nonactin and to demonstrate that the cation complexes are partially hydrated in the organic phase.

Modelling a Linker Mix-and-Match Approach for Controlling the Optical Excitation Gaps and Band Alignment of Zeolitic Imidazolate Frameworks.

Tuning the electronic structure of metal-organic frameworks is the key to extending their functionality to the photocatalytic conversion of absorbed gases. Herein we discuss how the band edge positions in zeolitic imidazolate frameworks (ZIFs) can be tuned by mixing different imidazole-based linkers within the same structure. We present the band alignment for a number of known and hypothetical Zn-based ZIFs with respect to the vacuum level.

Critical Role of Dynamic Flexibility in Ge-Containing Zeolites: Impact on Diffusion.

Incorporation of germanium in zeolites is well known to confer static flexibility to their framework, by stabilizing the formation of small rings. In this work, we show that the flexibility associated to Ge atoms in zeolites goes beyond this static effect, manifesting also a clear dynamic nature, in the sense that it leads to enhanced molecular diffusion. Our study combines experimental and theoretical methods providing evidence for this effect, which has not been described previously, as well as a rationalization for it, based on atomistic grounds.

Quantum and Classical Molecular Dynamics of Ionic Liquid Electrolytes for Na/Li-based Batteries: Molecular Origins of the Conductivity Behavior.

Compositional effects on the charge-transport properties of electrolytes for batteries based on room-temperature ionic liquids (RTILs) are well-known. However, further understanding is required about the molecular origins of these effects, in particular regarding the replacement of Li by Na. In this work, we investigate the use of RTILs in batteries, by means of both classical molecular dynamics (MD), which provides information about structure and molecular transport, and ab initio molecular dynamics (AIMD), which provides information about structure.

Comparing gas separation performance between all known zeolites and their zeolitic imidazolate framework counterparts.

To find optimal porous materials for adsorption-based separations is a challenging task due to the extremely large number of possible pore topologies and compositions. New porous material classes such as Metal Organic Frameworks (MOFs) are emerging, and hope to replace traditionally used materials such as zeolites. Computational screening offers relatively fast searching for candidate structures as well as side-by-side comparisons between material families.

Binding Selectivity of Macrocycle Ionophores in Ionic Liquids versus Aqueous Solution and Solvent-free Conditions.

The understanding of supramolecular recognition in room-temperature ionic liquids (RTILs) is key to develop the full potential of these materials. In this work, we provide insights into the selectivity of the binding of alkali metal cations by standard cyclodextrin and calixarene macrocycles in RTILs. A direct laser desorption/ionization mass spectrometry approach is employed to determine the relative abundances of the inclusion complexes formed through competitive binding in RTIL solutions.

Thermostructural behaviour of Ni-Cr materials: modelling of bulk and nanoparticle systems.

The thermostructural properties of Ni-Cr materials, as bulk and nanoparticle (NP) systems, have been predicted with a newly developed interatomic potential, for Ni/Cr ratios from 100/0 to 60/40. The potential, which has been fitted using experimental data and further validated using Density Functional Theory (DFT), describes correctly the variation with temperature of lattice parameters and the coefficient of thermal expansion, from 100 K to 1000 K. Using this potential, we have performed Molecular Dynamics (MD) simulations on bulk Ni-Cr alloys of various compositions, for which no experimental data are available.

Study of peripheral stem cells mobilization as a treatment line of pediatric dilated cardiomyopathy.

Background: Mobilizing hematopoietic stem cells may be a promising intervention for the treatment of idiopathic dilated cardiomyopathy (IDCM) in infant and children. So the aim of the work is to evaluate the efficacy of granulocyte-colony stimulating factor (G-CSF) as a therapeutic modality in pediatric IDCM.

Methods: A randomized clinical trial was conducted on 40 pediatric patients with IDCM.

Multipodal coordination of a tetracarboxylic crown ether with NH4(+): a vibrational spectroscopy and computational study.

The elucidation of the structural requirements for molecular recognition by the crown ether (18-crown-6)-2,3,11,12-tetracarboxylic acid (18c6H(4)) and its cationic complexes constitutes a topic of current fundamental and practical interest in catalysis and analytical sciences. The flexibility of the central ether ring and its four carboxyl side arms poses important challenges to experimental and theoretical approaches. In this study, infrared action vibrational spectroscopy and quantum mechanical computations are employed to characterize the conformational structure of the isolated gas phase complex formed by the 18c6H(4) host with NH(4)(+) as guest.

Effect of air humidity on the removal of carbon tetrachloride from air using Cu-BTC metal-organic framework.

We have used interatomic potential-based simulations to study the removal of carbon tetrachloride from air at 298 K, using Cu-BTC metal organic framework. We have developed new sets of Lennard-Jones parameters that accurately describe the vapour-liquid equilibrium curves of carbon tetrachloride and the main components from air (oxygen, nitrogen, and argon). Using these parameters we performed Monte Carlo simulations for the following systems: (a) single component adsorption of carbon tetrachloride, oxygen, nitrogen, and argon molecules, (b) binary Ar/CCl(4), O(2)/CCl(4), and N(2)/CCl(4) mixtures with bulk gas compositions 99 : 1 and 99.

Crown ether complexes with H₃O⁺ and NH₄⁺: proton localization and proton bridge formation.

The complexes formed by crown ethers with hydronium and ammonium cations are of key relevance for the understanding of their supramolecular behavior in protic solvents. In this work, the complexes of the 15-crown-5 (15c5) and 18-crown-6 (18c6) ethers with H₃O⁺ and NH₄⁺ and their deuterated variants are investigated under isolated conditions. The study employs infrared multiple photon dissociation (IRMPD) vibrational spectroscopy and DFT B3LYP/6-31++G(d,p) calculations for conformational assignment.

On the performance of Cu-BTC metal organic framework for carbon tetrachloride gas removal.

The performance of Cu-BTC metal organic framework for carbon tetrachloride removal from air has been studied using molecular simulations. According to our results, this material shows extremely high adsorption selectivity in favour of carbon tetrachloride. We demonstrate that this selectivity can be further enhanced by selective blockage of the framework.

Gas-phase complexes of cyclic and linear polyethers with alkali cations.

The flexibility of polymer backbones constitutes one key aspect in their molecular recognition properties. This investigation characterizes the structure of the gas-phase complexes formed by the cyclic and linear polyethers with the heavier alkali metal cations. In particular, the cyclic 15-crown-5 ether (15c5), (OCH(2)CH(2))(5), and the polyethylene glycol linear chains PEG4 and PEG9, H(OCH(2)CH(2))(n=4,9)OH, are considered.