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-[SiWO{Ni(HO)}] (denoted as SiWNi), was intercalated into ZnAl based Layered Double Hydroxide (ZnAl-LDH) by the selective ion-exchange technique. The as-synthesized nanocomposite, SiWNi@ZnAl, 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 SiWNi polyoxometalate and ZnAl-LDH precursors is evidenced by a higher catalytic property of the SiWNi@ZnAl composite compared to the individual constituents separately. Lewis/Bronsted acidity of the SiWNi polyoxometalate and ZnAl-LDH precursors appear to be essential for the catalytic performance of the composite. Furthermore, the catalytic performance of SiWNi@ZnAl was also tested in GBB 3-CRs synthesis of amino imidazothiazole under mild and solvent-free conditions.