Cobalt-Based ZIF Composite Membranes: In Situ Defect Engineering for Enhanced Water Stability and Gas Separation.

Porous coordination polymers with excellent molecular sieving ability, high dispersibility, and good compatibility with engineered polymer matrices hold promise for various industrial applications, such as gas separation and battery separators. Here, an in situ defect engineering approach is proposed for highly processable cobalt (Co)-based zeolitic imidazolate frameworks (ZIFs) with enhanced molecular sieving ability and water stability. By varying alkylamine (AA) modulators, the pore structures and textural properties of ZIFs can be fine-tuned.

Coarse-grained force field for ZIF-8: A study on adsorption, diffusion, and structural properties.

Metal-organic frameworks (MOFs) are revolutionizing a spectrum of industries, from groundbreaking gas storage solutions to transformative biological system applications. The intricate architecture of these materials necessitates the use of advanced computational techniques for a comprehensive understanding of their molecular structure and prediction of their physical properties. Coarse-grained (CG) simulations shine a spotlight on the often-neglected influences of defects, pressure effects, and spatial disorders on the performance of MOFs.

A systematic DFT study of structure and electronic properties of titanium dioxide.

DFT functionals are of paramount importance for an accurate electronic and structural description of transition metal systems. In this work, a systematic analysis using some well-known and commonly used DFT functionals is performed. A comparison of the structural and energetic parameters calculated with the available experimental data is made in order to find the adequate functional for an accurate description of the TiO bulk and surface of both anatase and rutile structures.

Unexpectedly High Propylene/Propane Separation Performance of Asymmetric Mixed-Matrix Membranes through Additive-Assisted ZIF-8 Filler Formation: Experimental and Computational Studies.

Zeolitic-imidazolate framework-8 (ZIF-8), composed of a zinc center tetrahedrally coordinated with 2-methylimidazolate linkers, has garnered extensive attention as a selective filler for propylene-selective mixed-matrix membranes (MMMs). Recently, we reported an innovative and scalable MMM fabrication approach, termed "phase-inversion in sync with MOF formation" (PIMOF), aimed at addressing the prevailing challenges in MMM processing. In this study, we intend to investigate the effect of additives, specifically sodium formate and 1,4-butanediol, on the modification of ZIF-8 filler formation within the polymer matrix in order to further improve the separation performance of the asymmetric MMMs prepared by the PIMOF.

Prediction of Adsorption and Diffusion of Shale Gas in Composite Pores Consisting of Kaolinite and Kerogen using Molecular Simulation.

Natural gas production from shale formations is one of the most recent and fast growing developments in the oil and gas industry. The accurate prediction of the adsorption and transport of shale gas is essential for estimating shale gas production capacity and improving existing extractions. To realistically represent heterogeneous shale formations, a composite pore model was built from a kaolinite slit mesopore hosting a kerogen matrix.

Mixed Solvent Electrolyte Solutions: A Review and Calculations with the eSAFT-VR Mie Equation of State.

In this work, mixed-solvent mean ionic activity coefficients (MIAC), vapor-liquid equilibrium (VLE), and liquid-liquid equilibrium (LLE) of electrolyte solutions have been addressed. An extended literature review of existing electrolyte activity coefficient models (eG) and electrolyte equations of state (eEoS) for modeling mixed solvent electrolyte systems is first presented, focusing on the details of the models in terms of physical and electrolyte terms, relative static permittivity, and parameterization. The analysis of this literature reveals that the property predictions can be ranked, from the easiest to the most difficult, in the following order: VLE, MIAC, and LLE.

Visceral Adiposity Independently Predicts Time to Flare in Inflammatory Bowel Disease but Body Mass Index Does Not.

Background: Obesity is associated with progression of inflammatory bowel disease (IBD). Visceral adiposity may be a more meaningful measure of obesity compared with traditional measures such as body mass index (BMI). This study compared visceral adiposity vs BMI as predictors of time to IBD flare among patients with Crohn's disease and ulcerative colitis.

Molecular Modeling of Double Retrograde Vaporization Using Monte Carlo Simulations and Equations of State.

Vapor-liquid equilibria of binary systems consisting of a low-boiling (i.e., more volatile) and a high-boiling compound may exhibit unexpected behavior near the critical point of the low-boiling compound.

The Contribution of the Ion-Ion and Ion-Solvent Interactions in a Molecular Thermodynamic Treatment of Electrolyte Solutions.

Developing molecular equations of state to treat electrolyte solutions is challenging due to the long-range nature of the Coulombic interactions. Seminal approaches commonly used are the mean spherical approximation (MSA) and the Debye-Hückel (DH) theory to account for ion-ion interactions and, often, the Born theory of solvation for ion-solvent interactions. We investigate the accuracy of the MSA and DH approaches using each to calculate the contribution of the ion-ion interactions to the chemical potential of NaCl in water, comparing these with newly computer-generated simulation data; the ion-ion contribution is isolated by selecting an appropriate primitive model with a Lennard-Jones force field to describe the solvent.

Phase equilibria molecular simulations of hydrogen hydrates via the direct phase coexistence approach.

We report the three-phase (hydrate-liquid water-vapor) equilibrium conditions of the hydrogen-water binary system calculated with molecular dynamics simulations via the direct phase coexistence approach. A significant improvement of ∼10.5 K is obtained in the current study, over earlier simulation attempts, by using a combination of modifications related to the hydrogen model that include (i) hydrogen Lennard-Jones parameters that are a function of temperature and (ii) the water-guest energy interaction parameters optimized further by using the Lorentz-Berthelot combining rules, based on an improved description of the solubility of hydrogen in water.

Acute Pancreatitis with Colonic Pseudo-obstruction in a Patient with COVID-19.

Angiotensin-converting enzyme 2 receptor, the receptor used by severe acute respiratory syndrome coronavirus-2 (COVID-19) to infect cells, is found not only on respiratory epithelium but also in the small bowel, large bowel, and pancreas. There have been rare reports of acute pancreatitis (AP) in COVID-19 patients without an obvious etiology other than the underlying viral syndrome. We present a patient who was admitted with COVID-19 and developed AP and colonic pseudo-obstruction.

Industrial Requirements for Thermodynamic and Transport Properties: 2020.

This paper reports the results of an investigation of industrial requirements for thermodynamic and transport properties carried out during the years 2019-2020. It is a follow-up of a similar investigation performed and published 10 years ago by the Working Party (WP) of Thermodynamics and Transport Properties of European Federation of Chemical Engineering (EFCE). The main goal was to investigate the advances in this area over the past 10 years, to identify the limitations that still exist, and to propose future R&D directions that will address the industrial needs.

Delayed Linker Addition (DLA) Synthesis for Hybrid SOD ZIFs with Unsubstituted Imidazolate Linkers for Propylene/Propane and n-Butane/i-Butane Separations.

We present a novel synthesis strategy termed delayed linker addition (DLA) to synthesize hybrid zeolitic-imidazolate frameworks containing unsubstituted imidazolate linkers (Im) with SOD topology (hereafter termed Im/ZIF-8). Im linker incorporation can create larger voids and apertures, which are important properties for gas storage and separation. To date, there have been only a handful of reports of Im linkers incorporated into ZIF-8 frameworks, typically requiring arduous and complicated post synthesis approaches.

Efavirenz as a psychotropic drug.

Objective: Antiretroviral drugs are the mainstay of treatment for human immunodeficiency virus (HIV) infection. Lifelong highly active antiretroviral therapy (HAART) is indicated to prevent disease progression to acquired immunodeficiency syndrome (AIDS). Efavirenz was a first-line component of HAART across the world for many years.

Kirkwood-Buff Integrals Using Molecular Simulation: Estimation of Surface Effects.

Kirkwood-Buff (KB) integrals provide a connection between microscopic properties and thermodynamic properties of multicomponent fluids. The estimation of KB integrals using molecular simulations of finite systems requires accounting for finite size effects. In the small system method, properties of finite subvolumes with different sizes embedded in a larger volume can be used to extrapolate to macroscopic thermodynamic properties.

Characterization of Long Linear and Branched Alkanes and Alcohols for Temperatures up to 573.15 K by Surface Light Scattering and Molecular Dynamics Simulations.

This work contributes to the characterization of long linear and branched alkanes and alcohols via the determination of their thermophysical properties up to temperatures of 573.15 K. For this, experimental techniques including surface light scattering (SLS) and molecular dynamics (MD) simulations were used under equilibrium conditions to analyze the influences of chain length, branching, and hydroxylation on liquid density, liquid viscosity, and surface tension.

Defining New Limits in Gas Separations Using Modified ZIF Systems.

Zeolitic-imidazolate frameworks (ZIFs) are candidate materials for the next generation of membranes for cheaper, "greener" separations. More than a decade after ZIF introduction, the high propylene/propane selectivity of ZIF-8 and ZIF-67 is the only example of ZIF membranes with remarkable selectivity efficiency despite their numerous advantages over other families of materials. Herein, we demonstrate the effectiveness of molecular-scale modification in the design of new ZIF materials useful for the separation of important and highly challenging mixtures such as He/CH, H/CH, O/N, CO/CH, and CO/N.

Quantifying Pore Width Effects on Diffusivity via a Novel 3D Stochastic Approach with Input from Atomistic Molecular Dynamics Simulations.

The increased production of unconventional hydrocarbons emphasizes the need to understand the transport of fluids through narrow pores. Although it is well-known that confinement affects fluids structure and transport, it is not yet possible to quantitatively predict properties such as diffusivity as a function of pore width in the range of 1-50 nm. Such pores are commonly found not only in shale rocks but also in a wide range of engineering materials, including catalysts.

Molecular Dynamics Simulation of Pure -Alkanes and Their Mixtures at Elevated Temperatures Using Atomistic and Coarse-Grained Force Fields.

The properties of higher -alkanes and their mixtures is a topic of significant interest for the oil and chemical industry. However, the experimental data at high temperatures are scarce. The present study focuses on simulating -dodecane, -octacosane, their binary mixture at a -dodecane mole fraction of 0.

Monte Carlo simulations of the separation of a binary gas mixture (CH + CO) using hydrates.

The current study employs Grand Canonical Monte Carlo simulations in order to calculate the process efficiency of separating CH4 + CO2 gas mixtures by utilizing structure sI clathrate hydrates. The temperature and pressure conditions examined in the current study resemble those used in industry. The simulation results are compared with experimental measurements and very good agreement is found.

On the Efficient Separation of Gas Mixtures with the Mixed-Linker Zeolitic-Imidazolate Framework-7-8.

A recently reported modification of the zeolitic-imidazolate framework-8 (ZIF-8) with partial replacement of the 2-methylimidazolate (mIm) linker with benzimidazolate (bIm), namely ZIF-7-8, is investigated with molecular simulations using a first-time reported force field. The size of the ZIF-7-8 aperture, which governs the gas-separation efficiency of this material and which has not been estimated before for this modification, is smaller than that of the original ZIF-8. The diffusivities of CO, N, and CH estimated through transition state theory calculations result in remarkably high diffusion selectivities for CO/CH and CO/N mixtures.

Tailoring the gas separation efficiency of metal organic framework ZIF-8 through metal substitution: a computational study.

The influence of a zeolitic imidazolate framework (ZIF)'s metal identity on its gas separation performance is studied extensively through molecular simulations for a variety of gases. ZIF-8 is used as the original framework for alterations of different metal substitutes of the Zn metal. ZIF-8 consists of cages connected by narrow apertures that exhibit flexibility through "swelling", allowing for relatively large penetrants to diffuse.

Two-body perturbation theory versus first order perturbation theory: A comparison based on the square-well fluid.

We show that the Zwanzig first-order perturbation theory can be obtained directly from a truncated Taylor series expansion of a two-body perturbation theory and that such truncation provides a more accurate prediction of thermodynamic properties than the full two-body perturbation theory. This unexpected result is explained by the quality of the resulting approximation for the fluid radial distribution function. We prove that the first-order and the two-body perturbation theories are based on different approximations for the fluid radial distribution function.