Advances of covalent organic frameworks based on magnetism: Classification, synthesis, properties, applications

• The magnetic covalent organic frameworks (MCOFs) are divided into three categories. • The main characteristics of MCOFs and different synthesis methods are introduced. • The application scope of MCOFs is comprehensively investigated. • The application mechanism of MCOFs in various aspects is explained reasonably. • The future development and challenges of MCOFs have been prospected. Magnetic nanoparticles (MNPs) possess outstanding rapid magnetic separation ability due to their excellent superparamagnetism and stability. Covalent organic frameworks (COFs) have the advantages of porous structure, large specific surface area, remarkable acid–base and thermal stability that can form novel magnetic nanocomposites with MNPs. The formed magnetic covalent organic frameworks (MCOFs) composite material owns high saturation magnetization and prominent chemical stability, which is the great potential material in the fields of environmental remediation and biological applications. Based on the current research results, firstly, this review further simplifies the classification according to the composition and functionalization of the composite: primitive MCOFs, functionalized MCOFs, composite of Fe/Co/Ni and its alloys with COFs. Secondly, several major characteristics and diverse synthesis methods of MCOFs composites are described. Thirdly, the applications of MCOFs in adsorption and enrichment detection, catalysis, sensing and biomedical aspect are reviewed in detail, and the mechanisms of these processes have been fully and reasonably explained. Finally, the future development and challenges of MCOFs composite materials have been prospected. This work aims to provide a theoretical basis for the synthesis and design of MCOFs composite materials in the future.