Core-shell nanocomposites with a catalytic metal-organic framework (MOF) shell are 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, and promoted the aerobic oxidation and magnetic recyclability of core-shell nanocomposite FeO@SiO@UiO-66. The FeO@SiO core is encapsulated by the in situ-grown UiO-66 shell, and the UiO-66 shell retains the porous structure and crystallinity of UiO-66 with abundant exposed Lewis acid sites. It shows high catalytic ability for the synthesis of various benzimidazoles through the acid-catalyzed condensation and aerobic oxidation with in situ oxygen. The FeO@SiO core provides magnetic recyclability of FeO@SiO@UiO-66, and maintains high catalytic ability and stability over six cycles.