Applications of Metal–Organic Frameworks and Their Derivatives in Lithium–Sulfur Battery Separators: Advances and Prospectives Focusing on Cathode-Side Polysulfide Regulation

Metal–organic frameworks (MOFs) and their derivatives have emerged as promising candidates for separator engineering in lithium–sulfur batteries (LSBs). This is attributed to their structural tunability, high porosity, and chemical versatility. Despite their potential, challenges such as lithium polysulfide (LiPS) shuttling, sluggish redox kinetics, and poor interfacial stability still hinder the practical deployment of LSBs. This review examines recent advances in MOF- and MOF derivative-based materials for separator modification, focusing on design strategies, functional mechanisms, and electrochemical performance. Pristine MOFs are classified into the following three key structural tuning strategies: control of the pore microenvironment, engineering of metal sites, and enhancement of electrical conductivity. Meanwhile, MOF derivatives are examined using compositional categories to highlight their distinct chemical characteristics and catalytic functionalities for LiPS regulation. Key findings demonstrate that these materials can effectively suppress polysulfide migration, accelerate LiPS redox reactions, and improve lithium-ion transport across the separator. The review also identifies remaining challenges and suggests future perspectives for bridging material-level innovations with system-level applications. Overall, MOF-based separator materials represent a versatile and impactful approach for advancing the electrochemical performance and stability of next-generation LSBs.