Shedding Light on the Lewis Acid Catalysis in Organic Transformations Using a Zn-MOF Microflower and Its ZnO Nanorod

The Lewis acidic nature of both {[Zn-4(mu(3)-OH)(2)(D-2,4-cbs)(2)(H2O)(4)]center dot 5H(2)O}n (Zn-CBS) and its ZnO nanostructures (ZnO_1, 3D microflower; ZnO_2, 3D polyhedron; and ZnO_3, 1D nanorod) was explored for the comparative study of the C-C and C-N bond forming reactions, such as Knoevenagel condensation, Friedel-Crafts alkylation and Strecker reaction, with various substrates. Notably, the nanorod (ZnO_3) is found to be an exceptionally efficient heterogeneous catalyst in comparison to its parent Zn-CBS for the Knoevenagel condensation reaction showing 100% conversion in 15 min with only 2 mol% catalyst in methanol at 25 degrees C. Similar catalytic results were obtained in the multicomponent Strecker reaction where ZnO_3 showed an enhanced catalytic activity in water as compared to Zn-CBS. However, for the Friedel-Crafts alkylation reaction, Zn-CBS was better than ZnO_3. These highly efficient catalysts are recyclable for three consecutive runs without any notable change in the catalytic activity. Their mechanism of action for all three reactions is also explained. [GRAPHICS] .

Automated summary

This study explores the Lewis acidic nature of a coordination polymer and its nanostructures, and finds that 1D nanorods exhibit exceptional catalytic activity in Knoevenagel condensation and Strecker reactions, while the coordination polymer is more suitable for Friedel-Crafts alkylation reaction. These catalysts are highly efficient and recyclable.