Figure 1. Host system under study.

(a) Graphic representation of a single crystal of type ZSM-58 (ZSM=Zeolite Socony Mobil). An electron micrograph is presented in b, revealing the hexagonal prism shaped crystal habit of these zeolites (diameter of about 34 μm). (c) shows the framework of ZSM-58 (yellow sticks) as well as the pore structure (surface coloured in blue), referred to as structure type DDR (Deca-dodecasil 3R)56. Cages and windows have diameters of 0.77 nm and 0.36 to 0.44 nm, forming a hexagonally symmetric two-dimensional pore system. In both b and c, the c axis is aligned perpendicular to the plane of the paper (a–b plane). Mass transport occurs exclusively in this plane as the window size in the c direction (0.26 nm) is too narrow for guest molecules to pass through.