Pore wall of a mesoporous molecular sieve derived from kanemite

The pore diameters and pore wall thicknesses of the mesoporous molecular sieves FSM-16 derived from a layered silicate (kanemite) were estimated by X-ray diffraction, physisorption, transmission electron micrographs, ²⁹Si MAS NMR, and modeling and simulation. The XRD simulation with a simple model of a hexagonal array of cylinders gave reasonable values coinciding with those obtained by TEM and nitrogen adsorption, with some corrections. As-synthesized FSM-16 material had pore walls 0.4 nm thick, corresponding to the slightly less wrinkled single SiO₄ tetrahedral layer observed in the crystalline layered silicate minerals, and an apparent pore diameter of 4.2 nm. Surfactant-free FSM-16, formed by calcination and exchange for H⁺, had thicker pore walls of 0.8 and 0.9 nm corresponding to double SiO₄ tetrahedral layers and pore diameters of 3.4 and 3.7 nm.