Synthesis of octahedral molecular sieves

A large number of families of manganese oxide octahedral molecular sieves (OMS) and their precursors, octahedral layered materials (OL), have been synthesized and characterized by various methods. The materials include OMS-1, OMS-2, and OL-1; they all use MnO 6 octahedra as the basic structural unit to form (3X3) tunnels, (2X2) tunnels, and layered structures, respectively. Different metal cations can incorporate into the OMS and OL structures through framework, tunnel, and interlayer substitutions. These materials can be synthesized by the reflux, hydrothermal, precipitation, calcination, ion-exchange, isomorphous substitution, and sol-gel methods. The materials have been characterized in detailed by a variety of techniques to study the structure, composition, stability, and morphology. This paper will discuss and review the different methods used to synthesize OMS and OL materials and the resultant changes in physical and chemical properties.