A series of highly ordered, super-microporus, lamellar silicas prepared by nanocasting with ionic liquids

This paper reports a novel preparation of highly ordered monolithic super-microporous lamellar silica with a series of ionic liquids (ILs), 1-alkyl-3-methylimidazolium chloride, as templates via a nanocasting technique. The results show that the silica walls of the formed ordered, super-microporous, lamellar mesostructure were arranged parallel to each other, displaying a very regular structure with ca. 1.2-1.5 nm in pore diameter (in the supermicroporous regime), which changed with the chain lengths of the employed templates. Atomic force microscopy and polarized optical microscopy provide direct evidence for the confirmation of the highly ordered and aligned lamellar phase structures of the synthesized monolithic silica. Transmission electron microscopy and low-angle X-ray scattering demonstrate that the ordered, lamellar nanostructure of the prepared super-microporous silica displays no collapse after removal of the template. The formation of potentially two-dimensional crystals of the ILs between the neighboring silica walls by interdigitation of the alkyl chains of the lLs spatially parallel to the imidazole plane is proposed for the templated-formation of the ordered, lamellar super-micropores. The temperature of the sol-gel reaction has been found to have great influences on the molecular spatial aggregates of the ILs, further affecting the pore mesostructure formed.