What are the experimental conditions required to observe changes in zeolite topology using the VPT method?
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Experimental conditions required to observe changes in zeolite topology using the VPT method include exposing zeolite 13X to air with pressure ranging from 0 to 100 kPa to observe spin-conversion of o-Ps and associating longer lifetimes τ3 and τ4 with o-Ps annihilation in the β cage and supercage respectively . Additionally, for calcined zeolite 10X, measuring lifetime spectra at temperatures from 25 to 750 oC shows that with the desorption of water molecules from cages, the free volume of the zeolite becomes larger and Bronsted acids are observed in the β cage and supercage . Furthermore, in situ electron microscopy can be used to image the straight channels of zeolite ZSM-5 and observe subcell flexibility of the framework, with the opening pores stretching along the longest direction of confined molecules .
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