Similarities between the clathrasils DOH, DDR, MEP and MTN

Clathrasils are porous framework silicates with cage-like voids. Structural similarities between the clathrasils DOH, MTN, MEP, DD3H and DDR have been analyzed in the context of host/guest interaction and crystallization mechanism. A building unit consisting of 30 T atoms is used as common structural feature to give an alternative description of the well-known layers of [5(12)]- cages. The [5(12)]-layers, or Periodic Building Units (Per-BU's), are constructed from two 12-rings connected through a common 6-ring to form two half cages or a 12-ring double cup. These 'half-cages' are essentially the bottom of the large 'inter-layer' cages in the clathrasils. The rigorous derivation of all possible framework types and their cages based on these principles shows the richness of the concept and makes possible new strategies for the synthesis. The 'half-cages' are also possible candidates for precursors which might exist in solution in close contact with templating guest species initiating the nucleation of the crystals.