We use molecular simulations to analyze the preferential adsorption sites of molecules that differ in size, shape, and polarizability in Cu-BTC metal organic framework. The cage system of the framework can be exploited to enhance adsorption of small gases. We find that nonpolar molecules adsorb preferentially in the small tetrahedral cages, whereas alcohols and water molecules adsorb close to the copper atoms in one of the big cages. Blocking potentially enhances selective adsorption and separation and we therefore investigate how to block these cages in a practical manner. We propose to use ionic liquids for it and we find that the addition of these components reduces the adsorption of polar molecules near the open metal centers. For this reason, the presence of ionic liquids reduces the attack of the molecules of water to the metallic centers improving the framework stability.

Deep eutectic solvents (DESs) are lately expanding their use to more demanding applications upon aqueous dilution thanks to the preservation of the most appealing properties of the original DESs while overcoming some of their most important drawbacks limiting their performance, like viscosity. Both experimental and theoretical works have studied this dilution regime, the so-called “water-in-DES” system, at near-to stoichiometric amounts to the original DES. Herein, we rather studied the high-dilution range of the “water-in-DES” system looking for enhanced performance because of the interesting properties (a further drop of viscosity) and cost (water is cheap) that it offers. In particular, we found that, in the “water-in-DES” system of a ternary DES composed of resorcinol, urea and choline chloride (e.g., RUChClnW, where n represents mol of water per mole of ternary DES), the tetrahedral structure of water was distorted as a consequence of its incorporation, as an additional hydrogen bond donor or hydrogen bond acceptor, into the hydrogen bond complexes formed among the original DES components . DSC confirmed the formation of a new eutectic, with a melting point below that of its respective components, the original ternary DES and water. This depression in the melting point was also observed in the same regime of reline and malicine aqueous dilutions, thus suggesting the universality of this simple procedure (i.e., water addition to reach the high-dilution range of the “water-in-DES” system) to obtain deeper eutectics eventually providing enhanced performances and lower cost.

We report a molecular simulation study aimed to ascertain the effect exerted in gas adsorption when room-temperature ionic liquids (RTILs) are added into the pores of the Cu-BTC metal-organic framework (MOF). Carbon dioxide, methane, nitrogen, and their mixtures are studied. We take into account the influence of the type of anion and the relative amount of RTILs used. It is observed that the presence of RTILs in the MOF pores enhances significantly CO2 adsorption at low pressures, whereas methane and nitrogen adsorption is unaffected.

Monte Carlo simulations were used to compute the solubility of the pure gases CO 2 , CH 4 , CO, H 2 , N 2 , and H 2 S in the ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [bmim][Tf 2 N]. Simulations in the osmotic ensemble were performed to compute absorption isotherms at a temperature of 333.15 K using the versatile continuous fractional component Monte Carlo (CFCMC) method. The predicted gas solubilities and Henry constants are in good agreement with the experimental data. The Monte Carlo simulations correctly predict the observed solubility trend, which obeys the following order: H 2 S > CO 2 > CH 4 > CO > N 2 > H 2 . Relevant separation selectivities for the precombustion process are calculated from the pure gas Henry constants and a comparison with experimental data is provided.

Halide perovskites make efficient solar cells but suffer from several stability issues. The characterization of these degradation processes is challenging because of the limited spatiotemporal resolution in experiments and the absence of efficient computational methods to study these reactive processes. Here, we present the first reactive force field for molecular dynamics simulations of the phase instability and the defect-induced degradation in CsPbI 3 . We find that the phase transitions are driven by the anharmonic fluctuations of the atoms in the perovskite lattice. At low temperatures, the Cs cations tend to move away from their preferential positions, resulting in worse contacts with the surrounding metal halide framework which initiates the conversion to a nonperovskite phase. Moreover, our simulations of defective structures reveal that, although both iodine vacancies and interstitials are mobile in the perovskite lattice, the vacancies have a detrimental effect on the stability, leading to the decomposition of perovskites to PbI 2 .