The application of spontaneous flocculation for the preparation of lanthanide-containing polyoxometalates intercalated layered double hydroxides: highly efficient heterogeneous catalysts for cyanosilylation

The lanthanide-containing polyoxometalates (POMs) have been intercalated into layered double hydroxides (LDHs) successfully through the spontaneous flocculation method, resulting in the formation of new heterogeneous LDHs-POMs catalysts Mg3Al-LnW(10) (Ln = Eu, Tb and Dy). The synthetic method can prevent Mg2+/Al3+ cations leaching out of the LDHs during intercalation and successfully control the final Mg2+/Al3+ ratio in the corresponding (MgAl)-Al-3-LnW(10). Most importantly, the as-prepared Mg3Al-LnW(10) can be obtained without the formation of the impurity phase. The heterogeneous Mg3Al-EuW10 exhibits highly efficient catalytic reactivity for cyanosilylation of various aldehydes and ketones under solvent-free conditions. The Mg3Al-EuW10 can be easily recovered and reused for at least 10 times without obvious decrease of catalytic activity and the composition and the structure of the Mg3Al-EuW10 catalyst remain stable. Moreover, the Mg3Al-EuW10-catalyzed cyanosilylation of benzaldehyde and hexanal gives the highest TON of 119,950 and 119,906, respectively. (c) 2014 Elsevier B.V. All rights reserved.