Pseudosymmetry in ammonium [(carboxymethyl)sulfanyl]acetate

The structure of the title compound, NH₄⁺·C₄H₅O₄S⁻, is composed of mono­carboxyl­ate anions of [(carboxymethyl)sulfanyl]acetic acid linked into infinite chains via strong O—H⋯O⁻ hydrogen bonds. The three‐dimensional structure is completed by the ammonium cations, which interlink neighbouring chains via N—H⋯O hydrogen bonds. Solution and refinement in the true space group Pn led to an unambiguous position for the single carboxyl H atom. In the higher symmetry space group P2/n, the carboxylate anion would be located on a twofold axis.     

Solvent‐Induced Control over Breathing Behavior in Flexible Metal–Organic Frameworks for Natural‐Gas Delivery

Finding appropriate stimuli for controlling the breathing behavior of flexible metal–organic frameworks (MOFs) is highly challenging. Herein, we report the solvent‐induced changes in the particle size and stability of different breathing phases of the MIL‐53 series, a group of flexible MOFs. A water/dimethylformamide (DMF) ratio is tuned to synthesize members of the MIL‐53 series which have different behaviors. The breathing is explored by high‐pressure methane sorption tests. Increasing DMF concentration decreases MOF particle size and increases the stability of the porous phases, boosting the 5.8–65 bar sorption difference of methane, which is required for natural‐gas delivery.     

Highly Selective Removal of Perfluorinated Contaminants by Adsorption on All‐Silica Zeolite Beta

Perfluorinated alkylated substances (PFASs) are widely used in industrial and commercial applications, leading to a widespread occurrence of these persistent and harmful contaminants in our environment. Removal of these compounds from surface and waste waters is being mandated by European and U.S. governments. Currently, there are no treatment techniques available that lower the concentrations of these compounds for large water bodies in a cost‐ and energy‐efficient way. We hereby propose a hydrophobic, all‐silica zeolite Beta material that is a highly selective and high‐capacity adsorbent for PFASs, even in the presence of organic competitors. Advanced characterization data demonstrate that the adsorption process is driven by a very negative adsorption enthalpy and favorable steric factors.     

Molecular simulations of confined liquids: an alternative to the grand canonical Monte Carlo simulations

Commonly, the confinement effects are studied from the grand canonical Monte Carlo (GCMC) simulations from the computation of the density of liquid in the confined phase. The GCMC modeling and chemical potential (μ) calculations are based on the insertion/deletion of the real and ghost particle, respectively. At high density, i.e., at high pressure or low temperature, the insertions fail from the Widom insertions while the performing methods as expanded method or perturbation approach are not efficient to treat the large and complex molecules. To overcome this problem we use a simple and efficient method to compute the liquid's density in the confined medium. This method does not require the precalculation of μ and is an alternative to the GCMC simulations. From the isothermal-isosurface-isobaric statistical ensemble we consider the explicit framework/liquid external interface to model an explicit liquid's reservoir. In this procedure only the liquid molecules undergo the volume changes while the volume of the framework is kept constant. Therefore, this method is described in the Np(n)AV(f)T statistical ensemble, where N is the number of particles, p(n) is the normal pressure, V(f) is the volume of framework, A is the surface of the solid/fluid interface, and T is the temperature. This approach is applied and validated from the computation of the density of the methanol and water confined in the mesoporous cylindrical silica nanopores and the MIL-53(Cr) metal organic framework type, respectively.     

Functionalizing porous zirconium terephthalate UiO-66(Zr) for natural gas upgrading: a computational exploration

The ligand functionalization effect on the CO(2)/CH(4) separation performance of the MOF type UiO-66(Zr) was explored computationally. The -SO(3)H and -CO(2)H functionalized forms show the highest selectivity, good working capacity and medium ranged CO(2) adsorption enthalpy that make these materials very promising for physisorption-based processes.     

Thermo‐Responsive MOF/Polymer Composites for Temperature‐Mediated Water Capture and Release

We report an in situ polymerization strategy to incorporate a thermo‐responsive polymer, poly(N‐isopropylacrylamide) (PNIPAM), with controlled loadings into the cavity of a mesoporous metal–organic framework (MOF), MIL‐101(Cr). The resulting MOF/polymer composites exhibit an unprecedented temperature‐triggered water capture and release behavior originating from the thermo‐responsive phase transition of the PNIPAM component. This result sheds light on the development of stimuli‐responsive porous adsorbent materials for water capture and heat transfer applications under relatively mild operating conditions.