Creation of “Intercalation Catalysts” by Use of Anion Exchangeable Layered Inorganic Hydroxides

Abstract

By use of anion-exchangeable ability of layered Ni-Zn hydroxy double salt (NiZn), unstable anionic transition metal complexes such as [Pd(OH) 4 ] 2− , [(D-val)Pd(OH) 2 ] − , or [Rh(OH) 6 ] 3− are able to be intercalated into NiZn interlayer under mild reaction conditions. Catalytically active species in interlayer are stabilized by the strong electrostatic interaction between the NiZn host and the guest anion. Furthermore, Brønsted basic anions such as PO 43− or OH − were also able to be integrated into NiZn interlayer. These “intercalation catalysts” promote various liquid phase reactions more effectively. The CuO-CuAl 2 O 4 nanocomposite synthesized by high temperature calcination (1073 K) of Cu-Al layered double hydroxide (CuAl LDH) acted as an effective heterogeneous catalyst for selective hydrogenation of carbonyl compounds with formic acid as a hydrogen donor and acceptorless dehydrogenation of various alcohols. The catalytically active Cu 0 species was formed by in situ reduction. The catalytic activity strongly depended on the Cu/Al ratio in preparation.