Novel core-shell nanocomposite as an effective heterogeneous catalyst for synthesis of benzimidazoles.

The core-shell nanocomposite with catalytic metal-organic framework (MOF) shell is more effective and stable than bare MOF. We have successfully designed an effective heterogeneous catalyst for the synthesis of benzimidazole by integrating acidic catalytic activity, promoted aerobic oxidation and magnetic recyclability into core-shell nanocomposite Fe3O4@SiO2@UiO-66. Fe3O4@SiO2 core is encapsulated by the in-situ growing UiO-66 shell, and the UiO-66 shell retains the porous structure and crystallinity of UiO-66 with abundant exposed Lewis acid sites, which shows high catalytic ability for the synthesis of various benzimidazole through the acid-catalyzed condensation and aerobic oxidation with in-situ oxygen. The Fe3O4@SiO2 core provides magnetic recyclability of Fe3O4@SiO2@UiO-66, which maintains high catalytic ability and stability for 6 cycles.