Redox-Active Metal–Organic Frameworks as Electrode-Active Materials in Aqueous Rechargeable Batteries

Abstract Redox-active metal–organic frameworks (RAMOFs) are a class of metal–organic frameworks (MOFs) capable of charge storage through the redox reactions of their metal nodes or organic linkers. Their highly ordered network structures, connected by coordination bonds, prevent the dissolution of redox-active sites into the electrolyte. Consequently, RAMOFs have been investigated as electrode-active materials for rechargeable batteries using organic electrolytes, as they readily maintain their crystal structure. Moreover, the intrinsic porosity of RAMOFs is expected to facilitate electrolyte penetration and efficient ion transport, enabling high cyclability without structural collapse. However, as RAMOFs are constructed through coordination bonds, most are prone to structural collapse in water, which limits their application as electrode-active materials in aqueous electrolytes. In this spotlight article, we highlight recent advances in RAMOFs capable of charge storage in aqueous electrolytes, in particular, our recent works for charge storage in strongly acidic aqueous electrolytes, wherein most RAMOFs typically suffer severe structural degradation. Finally, we discuss the challenges and future development of RAMOFs as electrode-active materials for aqueous rechargeable batteries.