Physisorption Hysteresis Loops and the Characterization of Nanoporous Materials

The classification of adsorption hysteresis loops recommended by the IUPAC in 1984 was based on experimental observations and the application of classical principles of pore filling (notably the use of the Kelvin equation for mesopore analysis). Recent molecular simulation and density functional (DFT) studies of the physisorption of gases by model pore structures have greatly improved our understanding of the mechanisms of hysteresis and it is therefore timely to revisit the IUPAC recommendations. In this review, we conclude that there is no immediate need to change the IUPAC classification of physisorption isotherms and hysteresis loops. However, in the light of recent advances, we are able to offer a revised…