Nickel substituted polyoxometalates in layered double hydroxides as metal-based nanomaterial of POM-LDH for green catalysis effects.

Three nickel substituted Keggin-type polyoxometalates, α-[SiW 9 O 37 {Ni(H 2 O)} 3 ] -10 (denoted as SiW 9 Ni 3 ), was intercalated into Zn 3 Al based Layered Double Hydroxide (Zn 3 Al-LDH) by the selective ion-exchange technique. The as-synthesized nanocomposite, SiW 9 Ni 3 @Zn 3 Al, was used as heterogeneous nanoreactor to promote the synthesis of drug-like aminoimidazopyridine small molecule skeletons via the well-known Ugi-type Groebke-Blackburn-Bienaymé reaction (GBB 3-CRs) in the absence of any acid/additive and under mild and solvent-free conditions. A synergistic catalytic effect between SiW 9 Ni 3 polyoxometalate and Zn 3 Al-LDH precursors is evidenced by a higher catalytic property of the SiW 9 Ni 3 @Zn 3 Al composite compared to the individual constituents separately. Lewis/Bronsted acidity of the SiW 9 Ni 3 polyoxometalate and Zn 3 Al-LDH precursors appear to be essential for the catalytic performance of the composite. Furthermore, the catalytic performance of SiW 9 Ni 3 @Zn 3 Al was also tested in GBB 3-CRs synthesis of amino imidazothiazole under mild and solvent-free conditions.