On the relationship between unit cells and channel systems in high silica zeolites with the "butterfly" projection

Abstract

Zeolites are crystalline aluminosilicate frame-work materials with corner sharing TO4 (T = Al, Si) tet-rahedra forming well-defined pores and channels. Many zeolites are built from similar building units (i.e., isolated units, chains or layers), which are connected in different ways to form a variety of topologies. We have identified ten zeolite frameworks that share the same two-dimensional “butterfly” net containing 5-, 6- and 10-rings: *MRE, FER, MEL, SZR, MFS, MFI, TUN, IMF, BOG and TON. Different orientations of the TO4 tetrahedra within the layer lead to different connectivities between neighboring layers. Some layers are corrugated and some are flat, resulting in differ-ent channel systems parallel to the layer. We found some interesting relationships between the unit cell parameters and this channel system that allow the size of the chan-nels and their directions to be deduced from the unit cell dimensions. This may facilitate the prediction of new members of this zeolite family. In addition, other zeolites containing the “butterfly” layers are also discussed.