Periodic mesoporous organosilica with a hexagonally pillared lamellar structure.

Ordered mesoporous materials (OMMs) with well-defined pore sizes (>2 nm) and pore geometries are important in various applications that require fast mass transfer or deal with large molecules. Extensive research has resulted in the discovery of OMMs with three types of mesostructures: (i) bi- or multicontinuous, (ii) columnar, and (iii) discontinuous (cagelike). However, another type, the pillared lamellar structure, which has long been sought and has been mathematically computed and known to exist in the research fields of surfactant and multiblock-copolymer mesophases, still remains a mesostructure that has not been observed in real OMMs for any specific symmetry. Herein, we report an unprecedented type of ordered mesoporous material with a hexagonally pillared lamellar (HPL) structure (P6(3)/mmc) that can be synthesized via a phase transformation from a lamellar mesophase by hydrothermal reaction in the presence of an organosilica precursor and a high concentration of a designed Gemini surfactant (Gem(16-3-16)) that has a large g value. The present GMO-HPL, which has an unique three-dimensional periodic structure with two-dimensionally connected pore channels running between the framework layers, provides a fascinating topological link between the lamellar and columnar (2D hexagonal) mesophases. It is unique in its application potential by making possible selective 2D diffusion in different directions.