Reversible sorption of nitrogen and xenon gas by the guest-free zeolite tris(o-phenylenedioxy)cyclotriphosphazene (TPP)

The sorption of nitrogen at 77 K and xenon at 298 K by the guest-free zeolite tris(o-phenylenedioxy)cyclotriphosphazene (TPP) was investigated. Xenon atoms show a remarkable affinity to the trigonal cavity of TPP by occupying about 90% of these sites at the pressure of about 100 kPa. Efficient sorption originates from a van der Waals type complex of xenon in the π-electron-rich environment given by the phenyl moieties of TPP. The interaction energy per site is in the order of 18 kJ mol−1. At partial loading a stabilizing effect of xenon on the thermal stability of the channel structure was observed. The solid state transformation from the pseudo-hexagonal TPP(Xe)0.2 structure to the non porous monoclinic form is described by a first-order kinetic.