Sorption of bulky aromatic molecules into zeolite NaX

Abstract The bulky molecules 1,3,5-tri- t -butylbenzene and 2,4,6-tribromo-1,3,5-triethylbenzene have been sorbed at 180°C into zeolite NaX and the resulting inclusion compounds characterised. The molecules have minimum diameters of approximately 0.90 nm and 0.95 nm respectively; this significantly exceeds the nominal 0.74 nm pore openings of NaX. The sorption of these molecules into NaX demonstrates the high degree of flexibility which can be shown by zeolite frameworks as well as sorbate molecules. Thermogravimetric and NMR spectroscopic data show the presence of the molecules in the samples, whereas X-ray diffraction indicates expansion of the zeolite framework to accommodate the molecules. Each super-cage can accommodate approximately one molecule, which has restricted mobility in the zeolite pore system. Treatment of the inclusion compounds at 180°C under vacuum resulted in the removal of only negligible quantities of sorbate and no fragmentation products were detected, indicating that the molecules remain intact.