Application of a tailorable carbon molecular sieve to evaluate concepts for the molecular dimensions of gases

Molecular sieves have attracted considerable interest for gas separation applications due to their ability to discriminate substances by their molecule's size. To predict if a molecular sieve is suitable for a specific separation problem an accurate measure of the molecular sizes is called for. Furthermore, a high precision in estimations for molecular dimensions is needed for the characterization of materials using molecular probes. In this work, different popular concepts to estimate the size of a gas molecule, specifically Breck's kinetic diameter, the critical diameter and molecular dimensions by Webster (MIN-1) are discussed. These concepts are evaluated using a tailorable carbon molecular sieve. It is concluded, that the widely used kinetic diameter has some drawbacks to determine the accessibility of pores. Finally, recommendations for alternatives from existing literature are presented.