A Review on Adsorption in Nanoporous Adsorbents for Gas Decontamination: Space Applications and Beyond

Abstract

This technical report presents the state of the art of experiments and molecular simulations on the adsorption of different molecule types into nanoporous adsorbents in the context of gas decontamination. While this review is primarily focused on vacuum decontamination for space applications, we consider the entire pressure range─from ultralow gas pressures to large gas pressures including pressures near saturating vapor pressures─to also cover gas decontamination relevant to other applications. In more detail, we consider the adsorption and trapping of molecules ranging from water, hydrocarbons, and siloxanes within existing materials such as active carbons, zeolites, mesoporous silicas, and metal organic frameworks. We first provide a short introduction to available experimental and molecular simulations methods that allow probing contaminant adsorption using nanoporous materials. Then, we discuss experimental and molecular simulation works by identifying simple essential parameters─the so-called descriptors─that allow describing and predicting the vapor pressure at which half pore filling occurs. In this report, we also present available theoretical frameworks which allow capturing gas adsorption in nanoporous solids. By restricting the discussion to physical models which are based on rigorous thermodynamic treatments, we identify available strategies that provide a consistent description of adsorption data as a function of relevant variables such as temperature, pressure, etc. In this context, we also provide thermodynamic schemes such as Derjaguin’s adsorption model and Polanyi’s adsorption potential theory which provide reliable strategies to describe and extrapolate adsorption under various thermodynamic conditions.