Recent development of magnetic nanomaterial-supported M(Salen) composites as recyclable heterogeneous catalysts

Abstract

Metal complexes of Salen-type ligands [M(Salen)] were widely used as catalysts with high activity for coupling reactions, addition reactions and epoxidation reactions. However, homogeneous catalysts based on M(Salen) complexes are difficult to separate and recover. Therefore, it is of great significance to find suitable supports to support M(Salen) complexes and obtain composites as separable and recyclable heterogeneous catalysts. Magnetic nanomaterials, which is widely researched as an inorganic nanosupports, are advantageous for the preparation of supported M(Salen) catalysts due to their characteristics of magnetic separation, good chemical stability and easy functionalization. In this review, research works on many types of the magnetic nanomaterial-supported M(Salen) catalysts, especially their preparations and applications as heterogeneous catalysts are discussed in detail. In addition, the advantages and disadvantages of different magnetic nanomaterials-supported M(Salen) composites are described, and some recommendations and references are provided for structure design of magnetic nanomaterial-supported M(Salen) catalyst with improved magnetic separation and catalytic efficiency. At last, limitations of magnetic nanomaterial-supported M(Salen), including structural instability, tedious multistep reactions and difficulty in industrial production, are discussed and their applications as heterogeneous catalysts are prospected.