Measurement of sorption equilibria under isosteric conditions: The principles, advantages and limitations

The development of the sorption-isosteric method (SIM) with minimum dead volume for a direct measurement of sorption heats is reviewed. Advantages and limitations of the technique are illustrated by concentration dependencies of the isosteric sorption heat for a series of gas–nanoporous-sorbent systems, several of which are discussed in the light of molecular simulation results. The technique is useful and effective in obtaining highly accurate thermodynamic data for sorption of gases by nanoporous materials. These properties are accessible as functions of sorption-phase concentration up to its saturation value. They serve for a calculation of sorption equilibria over wide ranges of temperature and pressure irrespective of phase transitions that may occur in the system.