Influence of orientational disorder in the adsorbent on the structure and dynamics of the adsorbate: MD simulations of SO$_2$ in ZSM-22

Abstract

Structural and dynamical behavior of SO$_2$ molecules within ZSM22 is studied using MD simulations, to understand the influence of orientational disorder (OD) and intercrystalline spacing in ZSM22 as a function of adsorbate loading. Addition of inter-crystalline space provides connectivity of isolated pores in ZSM22 and is shown to suppress both translational and rotational motion of SO$_2$. We infer that geometry and dimensionality of the connecting space is an important factor in determining the effects of pore connectivity on the adsorbed species behavior. As a function of OD, decrease in self diffusion coefficient of SO$_2$ in ZSM22 is observed. An increase in rotational correlation time t and a decrease in libration angle with OD is observed, due to the restriction imposed on the orientational freedom of the adsorbate by an increase in OD. The behavior of SO$_2$ result from an interplay of guest-host interactions and the dimensionality and confinement geometry.