Ag-doped nano magnetic γ-Fe2O3@DA core–shell hollow spheres: an efficient and recoverable heterogeneous catalyst for A3 and KA2 coupling reactions and [3 + 2] cycloaddition

Abstract

An effective protocol for the fabrication of Ag-doped nano magnetic γ-Fe₂O₃@DA core–shell hollow spheres (h-Fe₂O₃@DA/Ag) by a simple hydrothermal method is demonstrated without any templates in the reaction system. The synthesized core–shell structure was successfully characterized in terms of the chemical composition, surface morphology, and magnetic properties using FT-IR, VSM, TGA, TEM, FE-SEM, EDS, and XRD patterns. The possible formation mechanism of this magnetic γ-Fe₂O₃@DA/Ag hollow sphere structure is described based on the experimental results. In addition, as a physical property, the apparent shell density was determined using the specific surface area (BET) and shell thickness (BJH). The important, novel and unique catalyst with a hollow structural character and strong magnetic behavior exhibited a high catalytic activity in the A³ and KA² coupling reactions and [3 + 2] cycloaddition for the synthesis of 1H-tetrazoles. Furthermore, the recovered catalyst of the reaction mixture was facilitated by a magnetic field and multiple recycling was carried out without any significant loss in the catalytic activity.