ITQ-54: a multi-dimensional extra-large pore zeolite with 20 × 14 × 12-ring channels

Abstract

A multi-dimensional extra-large pore silicogermanate zeolite, named ITQ-54, has been synthesised by <i>in situ</i> decomposition of the <i>N</i>,<i>N</i>-dicyclohexylisoindolinium cation into the <i>N</i>-cyclohexylisoindolinium cation. Its structure was solved by 3D rotation electron diffraction (RED) from crystals of <i>ca.</i> 1 μm in size. The structure of ITQ-54 contains straight intersecting 20 × 14 × 12-ring channels along the three crystallographic axes and it is one of the few zeolites with extra-large channels in more than one direction. ITQ-54 has a framework density of 11.1 T atoms per 1000 ų, which is one of the lowest among the known zeolites. ITQ-54 was obtained together with GeO₂ as an impurity. A heavy liquid separation method was developed and successfully applied to remove this impurity from the zeolite. ITQ-54 is stable up to 600 °C and exhibits permanent porosity. The structure was further refined using powder X-ray diffraction (PXRD) data for both as-made and calcined samples.