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

Abstract

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–LnW10 (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 Mg3Al–LnW10. Most importantly, the as-prepared Mg3Al–LnW10 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.