Tuning redox activity in metal–organic frameworks: From structure to application

• Investigation about the originality of redox activity in metal–organic frameworks (MOFs) based on structure-application approach. • Structural investigation of redox active MOFs based on linkers, inorganic nodes, coordination bonds and guests. • Discussion about strategies for the synthesis of redox active MOFs. • Discussion about common pathways and mechanisms of charge transportation and redox activity in MOFs. • Illustration of utilization of redox active MOFs in both conventional and novel applications using evident characterizations and simulations. Among the various characteristics of metal–organic frameworks (MOFs), redox activity, the ability to store or release electrons is a vital property for functional MOFs in applications like catalysis, energy storage, conductivity, sensing and magnetism. MOFs with redox activity, called redox active MOFs (RAMOFs), can be developed through insertion of redox active sites into the framework. Benefit from the multiple building blocks of MOFs, unlimited availability is reached for inserting the redox active sites: ligands, metal ions or clusters, coordination sites and trapped guests. Careful selection and arrangement of one or more redox sites above will endow superior functionality to RAMOFs. Motivated by these advantages, here we provide a comprehensive overview of RAMOFs. First, the design and construction principles of reported RAMOFs are summarized and classified. Through transformation pathway of electrons, we differentiate them as inter-system RAMOFs and inner-system RAMOFs, examining how the unique chemical properties and electronic configuration contribute to the host–guest interaction or host–host interaction. Afterwards, typical applications like gas separation, catalysis, sensing, luminescence, energy storage and conductive materials are displayed to illustrate the structure–function relationships. Finally, an outlook for future development and potential challenges of RAMOFs, including the highly interdisciplinary chemical, physical, optical, and electrical approaches, is proposed.