Structural study of the silicalite (MFI)/tetrachlorethylene (TCET) host–guest system by X-ray powder diffraction and 29Si NMR. Locations of the TCET molecules at low and high pore-fillings

Abstract

Investigations on the silicalite (MFI)/tetrachlorethylene (TCET) system by X-ray powder diffraction show the existence of two sorbent/sorbate complexes, corresponding to four and eight molecules per unit-cell pore-fillings. Both phases present an orthorhombic symmetry and 29Si NMR shows that their space groups are Pnma and P212121 respectively. Crystal structure refinements using the Rietveld method show that at lower pore-fillings only one adsorbed species occupies the channel–intersections of the MFI topology. At higher loadings, a second tetraethylene species resides in the zigzag channels.