Preparation of Siloxane-Based Microporous Crystals from Hydrogen-Bonded Molecular Crystals of Cage Siloxanes.

Controlled assembly of siloxane-based building blocks provides a rational approach toward designed architectures of silica-based porous materials. Here, a non-hydrothermal method to prepare microporous crystals from cage-type oligosiloxanes is reported. The crystals formation occurs through an ordered assembly assisted by hydrogen bonds and subsequent intermolecular connection by silylation. Cage siloxanes with a double-four ring (D4R) structure were modified with dimethylsilanol groups. Intermolecular hydrogen bonding of the dimethylsilanol groups led to the formation of a pillared-layer structure consisting of D4R units. A new crystalline microporous material retaining the original ordered arrangement was realized by bridging adjacent cages within the crystals by direct silylation of the silanol groups with trichlorosilane. The use of this silylating agent created microporous crystals containing Si-H groups, proving the advantages of the proposed concept.