Organically Pillared Micro- and Mesoporous Materials

There is currently a great deal of research activity dealing with the synthesis and characterization of inorganic micro- and mesoporous materials. This activity not only stems from their possible use as sorbents, catalysts, molecular sieves, and related applications but also is due to fascination for their varied forms and novel structures. A somewhat promising but less thoroughly investigated topic is that of organically pillared layered compounds where the pillars are covalently bonded to the layers. These compounds are the cross-linked metal phosphonates of the type Mz+4/z(O3P−R−PO3), where R is an alkyl or aryl group. Because of the great variety of R groups containing different functional groups that can be used, these compounds have great potential utility. That this has not been realized is mainly due to the inability to control the pore sizes. The chemistry of this group of compounds will be reviewed and the prognosis for the future indicated.