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

Three nickel substituted Keggin-type polyoxometalates, alpha-[SiW9O37{Ni(H2O)}(3)](-10) (denoted as SiW9Ni3), was intercalated into Zn3Al based Layered Double Hydroxide (Zn3Al-LDH) by the selective ion-exchange technique. The as-synthesized nanocomposite, SiW9Ni3@Zn3Al, was used as heterogeneous nanoreactor to promote the synthesis of drug-like aminoimidazopyridine small molecule skeletons via the well-known Ugi-type Groebke-Blackburn-Bienayme reaction (GBB 3-CRs) in the absence of any acid/additive and under mild and solvent-free conditions. A synergistic catalytic effect between SiW9Ni3 polyoxometalate and Zn3Al-LDH precursors is evidenced by a higher catalytic property of the SiW9Ni3@Zn3Al composite compared to the individual constituents separately. Lewis/Bronsted acidity of the SiW9Ni3 polyoxometalate and Zn3Al-LDH precursors appear to be essential for the catalytic performance of the composite. Furthermore, the catalytic performance of SiW9Ni3@Zn3Al was also tested in GBB 3-CRs synthesis of amino imidazothiazole under mild and solvent-free conditions.

Automated summary

Three nickel substituted Keggin-type polyoxometalates (SiW9Ni3) were selectively intercalated into Zn3Al based Layered Double Hydroxide (Zn3Al-LDH) using ion-exchange technique. The resulting nanocomposite, SiW9Ni3@Zn3Al, acted as a heterogeneous nanoreactor for the synthesis of drug-like aminoimidazopyridine small molecules via Ugi-type Groebke-Blackburn-Bienayme reaction (GBB 3-CRs) without any acid/additive under mild and solvent-free conditions. The catalytic property of SiW9Ni3@Zn3Al was enhanced compared to the individual components, indicating a synergistic catalytic effect between SiW9Ni3 polyoxometalate and Zn3Al-LDH precursors. The Lewis/Bronsted acidity of SiW9Ni3 polyoxometalate and Zn3Al-LDH precursors played essential roles in the catalytic performance of the composite.