A Puckered Layered Silicate, KHSi2O5: Hydrolysis Products and Alkylammonium Intercalated Derivatives

The layered silicate KHSi2O5, its hydrolysis product, and its alkylammonium intercalates are of interest as starting materials for the preparation of heterogeneous catalysts. However, some of these materials are difficult to characterize due to low long-range order. Their short-range ordering was investigated through solid-state proton and Si-29 NMR spectroscopy (including proton cross-polarization of Si-29), in combination with IR spectroscopy, X-ray diffraction, weight loss, and surface area measurements. It is shown that stacking faults already exist in the parent KHSi2O5, together with very strong interlayer hydrogen bonding; on acid hydrolysis or alkylammonium intercalation, the structure undergoes considerable delamination, followed by reorientation of the layers and their partial condensation through the formation of siloxane bridges. Thus these reactions cannot be strictly considered as topotactic, contrary to what was previously believed.