Organic-inorganic layered phosphonates

Tetravalent metal phosphonates (MELS ) are layered compounds that can be considered organic/inorganic polymers. The organic functionality provided by the phosphonate largely determines the surface chemistry of these materials. Choosing phosphonates with an arylsulfonic acid function produces materials that are effective as acid catalysts. This paper describes synthetic procedures used to prepare arylsulfonic acid MELS and methods to increase and stabilize their surface area, porosity, and swelling properties. Acid catalysis by MELS is exemplified by the synthesis of methyl tertiary butyl ether. 

In heterogeneous catalysts, the tailored and pillared cavity is an essential property as it enables the movement of reactants to inner catalytic sites. The mass transfer of reactants and products inside the pores is mainly influenced by the interaction of the internal walls of the channel with organic molecules, and can consequently be controlled by the difference in polarities. To ensure such properties, anchored ruthenium hybrid zirconium phosphate-phosphonates coated with hydrophobic linear double-stranded polystyrene over the inner surface of the Zr layers were prepared by the first complexation of Ru and then molding of inorganic backbone method, and used as the catalyst in the ATH of o-, m- and p-substituted acetophenones (Fig. 42) [121]. This catalyst showed good catalytic activity and enantioselectivity (73.6-95.6 % ees) in the aqueous reduction with FA-TEA as the hydrogen donor, and could retain its catalytic properties after five runs in the case of acetophenone. 

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