Force field for ZIF-8 flexible frameworks: atomistic simulation of adsorption, diffusion of pure gases as CH₄, H₂, CO₂ and N₂

Abstract

A full set of flexible force field parameters for ZIF-8, applied for its gas adsorption and diffusion, has been presented.

Theoretical model estimation of guest diffusion in metal–organic frameworks (MOFs)

“…Molecular dynamics (MD), based on classical mechanics, is the most widely applied tool for the production of trajectories of guests in the phase space and obtainment of measurable macroscopic properties like diffusion [1]. Although many accurate MD simulations have been reported the results mainly depend on the assumption of inter-and intra-molecular potentials [7][8][9]. A reasonable semi-empirical force field for MOF systems should represent both the stability and the flexibility of the framework, which in principle increases the difficulty of building a force field [7,[9][10][11][12][13].…”

O2 Adsorption on ZIF-8: Temperature Dependence of the Gate-Opening Transition

“…In adsorption isotherm measurements the occurrence of this structural transition is reflected by the appearance of an additional substep in the isotherms; the substep corresponds to sorption in the additional available space. 11,12,13 The presence of the substep has been reported for adsorption measurements at cryogenic temperatures using various sorbates (Ar, CO, N 2 and O 2 ). 13 The same structural transition was first identified as being present at room temperature in ZIF-8 when a pressure on the order of 1.4 GPa is applied to this material using a methanolethanol mixture as hydrostatic medium.…”

“…10 This stability results from greater strength of the bonds between the organic linkers and the metal centers in these materials. 11 The ZIF that has most frequently been the object of study is ZIF-8. ZIF-8 is commercially available.…”

Molecular Mechanism of Swing Effect in Zeolitic Imidazolate Framework ZIF‐8: Continuous Deformation upon Adsorption

“…Both experimentala nd theoretical works on ZIF-8 have noted ad iscrepancy between experimental resultso fg as adsorptiona nd diffusivity,a nd the values that could be predicted from molecular simulations in rigid structures or simple considerations comparing the ZIF-8 window size and the adsorbates' kineticd iameter. [24] This ability of molecules larger than the geometricw indow size to diffuse through the ZIF-8 framework was attributed to flexibility of the structure. [25] The best-documented evidence of this effect was the computational characterization of self and transport diffusion coefficients of methane, ethane, ethylene, propane, propylene, n-butane, and 1-butene, by the Sholl group.…”