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Flexible metal-organic materials (FMOMs) with stepped isotherms can offer enhanced working capacity in storage applications such as adsorbed natural gas (ANG) storage. Unfortunately, whereas >1000 FMOMs are known, only a handful exhibit methane uptake of >150 cm 3 /cm 3 at 65 atm and 298 K, conditions relevant to ANG. Here, we report a double-walled 2-fold interpenetrated diamondoid ( dia ) network, X-dia-6-Ni, [Ni 2 L 4 (μ-H 2 O)] n , comprising a new azo linker ligand, L - ( L - = ( E )-3-(pyridin-4-yldiazenyl)benzoate) and 8-connected dinuclear molecular building blocks. X-dia-6-Ni exhibited gas (CO 2 , N 2 , CH 4 ) and liquid (C8 hydrocarbons)-induced reversible transformations between its activated narrow-pore β phase and γ , a large-pore phase with ca . 33% increase in unit cell volume. Single-crystal X-ray diffraction (SCXRD) studies of the as-synthesized phase α , β , and γ revealed that structural transformations were enabled by twisting of the azo moiety and/or deformation of the MBB. Further insight into these transformations was gained from variable temperature powder XRD and in situ variable pressure powder XRD. Low-temperature N 2 and CO 2 sorption revealed stepped Type F-II isotherms with saturation uptakes of 422 and 401 cm 3 /g, respectively. X-dia-6-Ni exhibited uptake of 200 cm 3 /cm 3 (65 atm, 298 K) and a high CH 4 working capacity of 166 cm 3 /cm 3 (5-65 bar, 298 K, 33 cycles), the third highest value yet reported for an FMOM and the highest value for an FMOM with a Type F-II isotherm.

Hybrid ultramicroporous materials (HUMs), metal-organic platforms that incorporate inorganic pillars, are a promising class of porous solids. A key area of interest for such materials is gas separation, where HUMs have already established benchmark performances. Thanks to their ready compositional modularity, we report the design and synthesis of a new HUM, GEFSIX-21-Cu , incorporating the ligand pypz (4-(3,5-dimethyl-1 H -pyrazol-4-yl)pyridine, 21 ) and GeF 6 2- pillaring anions. GEFSIX-21-Cu delivers on two fronts: first, it displays an exceptionally high C 2 H 2 adsorption capacity (≥5 mmol g -1 ) which is paired with low uptake of CO 2 (<2 mmol g -1 ), and, second, a low enthalpy of adsorption for C 2 H 2 ( ca . 32 kJ mol -1 ). This combination is rarely seen in the C 2 H 2 selective physisorbents reported thus far, and not observed in related isostructural HUMs featuring pypz and other pillaring anions. Dynamic column breakthrough experiments for 1:1 and 2:1 C 2 H 2 /CO 2 mixtures revealed GEFSIX-21-Cu to selectively separate C 2 H 2 from CO 2 , yielding ≥99.99% CO 2 effluent purities. Temperature-programmed desorption experiments revealed full sorbent regeneration in <35 min at 60 °C, reinforcing HUMs as potentially technologically relevant materials for strategic gas separations.

We report that linker ligand substitution involving just one atom induces a shape-memory effect in a flexible coordination network. Specifically, whereas SIFSIX-23-Cu, [Cu(SiF 6 )(L) 2 ] n , (L=1,4-bis(1-imidazolyl)benzene, SiF 6 2- =SIFSIX) has been previously reported to exhibit reversible switching between closed and open phases, the activated phase of SIFSIX-23-Cu N , [Cu(SiF 6 )(L N ) 2 ] n (L N =2,5-bis(1-imidazolyl)pyridine), transformed to a kinetically stable porous phase with strong affinity for CO 2 . As-synthesized SIFSIX-23-Cu N , α, transformed to less open, γ, and closed, β, phases during activation. β did not adsorb N 2 (77 K), rather it reverted to α induced by CO 2 at 195, 273 and 298 K. CO 2 desorption resulted in α', a shape-memory phase which subsequently exhibited type-I isotherms for N 2 (77 K) and CO 2 as well as strong performance for separation of CO 2 /N 2 (15/85) at 298 K and 1 bar driven by strong binding (Q st =45-51 kJ/mol) and excellent CO 2 /N 2 selectivity (up to 700). Interestingly, α' reverted to β after re-solvation/desolvation. Molecular simulations and density functional theory (DFT) calculations provide insight into the properties of SIFSIX-23-Cu N ., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Ultramicroporous materials can be highly effective at trace gas separations when they offer a high density of selective binding sites. Herein, we report that sql-NbOFFIVE-bpe-Cu , a new variant of a previously reported ultramicroporous square lattice, sql , topology material, sql-SIFSIX-bpe-Zn , can exist in two polymorphs. These polymorphs, sql-NbOFFIVE-bpe-Cu-AA ( AA ) and sql-NbOFFIVE-bpe-Cu-AB ( AB ), exhibit AAAA and ABAB packing of the sql layers, respectively. Whereas NbOFFIVE-bpe-Cu-AA ( AA ) is isostructural with sql-SIFSIX-bpe-Zn , each exhibiting intrinsic 1D channels, sql-NbOFFIVE-bpe-Cu-AB ( AB ) has two types of channels, the intrinsic channels and extrinsic channels between the sql networks. Gas and temperature induced transformations of the two polymorphs of sql-NbOFFIVE-bpe-Cu were investigated by pure gas sorption, single-crystal X-ray diffraction (SCXRD), variable temperature powder X-ray diffraction (VT-PXRD), and synchrotron PXRD. We observed that the extrinsic pore structure of AB resulted in properties with potential for selective C 3 H 4 /C 3 H 6 separation. Subsequent dynamic gas breakthrough measurements revealed exceptional experimental C 3 H 4 /C 3 H 6 selectivity (270) and a new benchmark for productivity (118 mmol g -1 ) of polymer grade C 3 H 6 (purity > 99.99%) from a 1:99 C 3 H 4 /C 3 H 6 mixture. Structural analysis, gas sorption studies, and gas adsorption kinetics enabled us to determine that a binding "sweet spot" for C 3 H 4 in the extrinsic pores is behind the benchmark separation performance. Density-functional theory (DFT) calculations and Canonical Monte Carlo (CMC) simulations provided further insight into the binding sites of C 3 H 4 and C 3 H 6 molecules within these two hybrid ultramicroporous materials, HUMs. These results highlight, to our knowledge for the first time, how pore engineering through the study of packing polymorphism in layered materials can dramatically change the separation performance of a physisorbent.

Coordination networks (CNs) that undergo gas-induced transformation from closed (nonporous) to open (porous) structures are of potential utility in gas storage applications, but their development is hindered by limited control over their switching mechanisms and pressures. In this work, we report two CNs, [Co(bimpy)(bdc)] n ( X-dia-4-Co ) and [Co(bimbz)(bdc)] n ( X-dia-5-Co ) (H 2 bdc = 1,4-benzendicarboxylic acid; bimpy = 2,5-bis(1H-imidazole-1-yl)pyridine; bimbz = 1,4-bis(1H-imidazole-1-yl)benzene), that both undergo transformation from closed to isostructural open phases involving at least a 27% increase in cell volume. Although X-dia-4-Co and X-dia-5-Co only differ from one another by one atom in their N -donor linkers (bimpy = pyridine, and bimbz = benzene), this results in different pore chemistry and switching mechanisms. Specifically, X-dia-4-Co exhibited a gradual phase transformation with a steady increase in the uptake when exposed to CO 2 , whereas X-dia-5-Co exhibited a sharp step (type F-IV isotherm) at P / P 0 ≈ 0.008 or P ≈ 3 bar (195 or 298 K, respectively). Single-crystal X-ray diffraction, in situ powder XRD, in situ IR, and modeling (density functional theory calculations, and canonical Monte Carlo simulations) studies provide insights into the nature of the switching mechanisms and enable attribution of pronounced differences in sorption properties to the changed pore chemistry.

In this study, dimensional, conformational and dynamic behaviors of a short-chain branched styrene/1-octene copolymer chain with different 1-octene percentages, i.e., 0, 2, 4 and 6%, in toluene are investigated at the temperature of 298.15 K via molecular dynamics simulation. The chain dimensions and flexibility in the solvent are evaluated by calculating the radius of gyration (R g ), end-to-end distance (0 >), surface area (A ch ), and volume (V ch ) of the copolymer chain. The mean square displacement (MSD) and diffusivity coefficient for each copolymer chain are measured to determine its dynamic behavior and mobility in aromatic media. To consider the effect of increasing the 1-octene co-monomer percentage on the copolymer chain affinity to the solvent molecules, the interaction energy (E int ) and Flory-Huggins (FH) interaction parameter are calculated for each equilibrated solution model. The simulation results indicate that the co-monomer level increment in the copolymer structure reduces the chain R g amount and its interaction with the solvent. The 0 > of the chain increases up to 4% co-monomer content, while further co-monomer content decreases the 0 > value. Additionally, the viscosity of the equilibrated dilute solutions is calculated via non-equilibrium molecular dynamics simulation (NEMD). Moreover, the steric hindrance of the copolymers and the solvent molecules capturing in the dilute solution is determined via radial distribution function (RDF) analysis. Helmholtz free energy and the system entropy changes are calculated to evaluate the tendency of the copolymer to the solvent molecules and its dilute solution irregularity, respectively. Graphical abstract The figure shows the variations trend of the poly(styrene-co-1-octene) chain dimensions in toluene aromatic solvent by increasing the 1-octene content (x), after the equilibration state. Red and blue colors represent the carbon atoms of the copolymer chain backbone and 1-octene side chains, respectively. The styrene rings and the hydrogen atoms of the chains were removed for better view.

The self-assembly behaviour of dual-responsive block copolymers and their ability to solubilize the anticancer drug doxorubicin (DOX) has been investigated using all-atom molecular dynamics (MD) simulations, MARTINI coarse-grained (CG) force field simulation and Scheutjens-Fleer self-consistent field (SCF) computations. These diblock copolymers, composed of poly{γ-2-[2-(2-methoxyethoxy)ethoxy]ethoxy-ε-caprolactone} (PMEEECL) and poly(β-amino ester) (PAE) are dual-responsive: the PMEEECL block is thermoresponsive (becomes insoluble above a certain temperature), while the PAE block is pH-responsive (becomes soluble below a certain pH). Three MEEECL 20 -AE M compositions with M = 5, 10, and 15, have been studied. All-atom MD simulations have been performed to calculate the coil-to-globule transition temperature ( T cg ) of these copolymers and finding appropriate CG mapping for both PMEEECL-PAE and DOX. The output of the MARTINI CG simulations is in agreement with SCF predictions. The results show that DOX is solubilized with high efficiency (75-80%) at different concentrations inside the PMEEECL-PAE micelles, although, interestingly, the loading efficiency is reduced by increasing the drug concentration. The non-bonded interaction energy and the RDF between DOX and water beads confirm this result. Finally, MD simulations and SCF computations reveal that the responsive behaviour of PMEEECL-PAE self-assembled structures take place at temperature and pH ranges appropriate for drug delivery., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Molecular characteristics of an atactic polystyrene (aPS) chain with different lengths in a theta solvent, cyclohexane at 307.65 K, were studied via molecular dynamics (MD) simulation. The interaction energy of the aPS dilute solution models and Flory-Huggins (FH) interaction parameter were calculated to investigate the effect of the chain molecular weight on its compatibility with the solvent molecules. The simulation results illustrated that increasing the chain length increased the interactions between the chain and the solvent molecules. The chain dimensions via calculating the radius of gyration (R g ) and end-to-end distance, 0 >, were measured. Mean square displacement (MSD) and diffusivity coefficient of the chains were calculated to determine their dynamic behavior. The results exhibited that two factors of the chain movability and size were important for the diffusion in oligomeric state. Additionally, viscosity of the resultant dilute solutions was calculated via nonequilibrium molecular dynamics simulation (NEMD). Moreover, the steric hindrance of the chains was determined by radial distribution function (RDF) analysis. The calculated characteristics of the chain and solution viscosity results showed a good agreement with experimental published works. Measurement of the potential field of cyclohexane-cyclohexane and aPS-cyclohexane pairs was also based on their potential field via quantum chemical calculations to determine the special orientation of the solvent molecules to each other and to the polymer segments, respectively. Graphical abstract (a) The equilibrated dilute solution model of polystyrene in cyclohexane at theta temperature (the red and yellow balls represent carbon and hydrogen atoms, respectively. The cyclohexane molecules are illustrated in line style in the box), (b) the electrostatic potential field around an optimized structure containing two cyclohexane molecules, and (c) around the sole cyclohexane molecule and polystyrene with two repeating units (carbon and hydrogen atoms are represented in green and yellow, respectively).

According to the critical role of drug delivery in the treatment of diseases of the central nervous system (CNS), the selection of a suitable carrier plays an important role in the greater effectiveness of drugs. Due to good biocompatibility, biodegradability and low toxicity of polymeric nanoparticles, especially poly(n-butylcyanoacrylate) (PBCA) and Chitosan, these nanoparticles are considered as efficient carriers in drug delivery to the brain. In order to investigate the compatibility of these two polymers with different degrees of polymerization versus a Tacrine unit as the most well known drug for the treatment of Alzheimer's disease, molecular dynamics simulation (MD) is used as a principal tool for studying molecular systems. Interaction energy of the polymer/Tacrine systems, the radius of gyration of the Chitosan and PBCA during the simulation time, solubility and Flory-Huggins interaction parameters has been calculated. According to the results, the Tacrine molecule exhibited higher compatibility with PBCA than Chitosan. Moreover, the interaction between the Tacrine molecules and PBCA nanoparticles became stronger by increasing the length of polymer chain while it was not observed as a regular trend for Chitosan/Tacrine systems. By using these MD simulations, it is possible to find the most appropriate polymer as an efficient drug carrier. We note that the methodology applied here for modeling the polymer/Tacrine system is not restricted to the specific formulations of Tacrine and Chitosan (or PBCA) in the current work and can be extended to various other traditional or new drugs and different polymer drug carriers., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In this study, interfacial adhesion between functionalized polyethylene (PE) surfaces and graphene were examined using molecular simulation. Various functional groups including amino, carboxy, hydroxy, cyano, isocyanato, oxo, and ethylamino were used to cover the PE surface with surface densities of 0.48, 1.30, and 4.84 groups per nm(2). The interfacial adhesion between the modified PE surfaces and the graphene was quantified via calculation of work of separation (Wsep), the amount of the required work to separate two surfaces without occurring any relaxation and diffusion phenomena. Insertion of the functional groups on the PE surface decreased the amount of Wsep, except for the oxo, amino, and higher densities of the carboxy groups. Increasing the surface group density enhanced the adhesion due to decreasing the surface atomic roughness and increasing the atomic density at the interface. In addition, the effect of surface group rearrangement was investigated via calculation of the work of adhesion (Wadh) while sufficient time had been devoted to relax the interface. The surface reorganization during the relaxation process significantly enhanced adhesion due to eliminating the surface roughness and increasing the surface atomic density.