Covalent organic frameworks for lithium–sulfur batteries: bridging synthesis, architecture, and electrochemical function

Covalent organic frameworks (COFs) have recently been recognized as adaptable platforms for tackling critical issues in lithium-sulfur (Li-S) batteries, such as polysulfide shuttling, slow redox reaction kinetics, and the formation of lithium dendrites. This review provides a systematic and critical overview of COF-based materials for Li-S batteries, with a unique emphasis on establishing explicit structure-activity relationships that govern their electrochemical performance. Beyond conventional COF designs, special attention is devoted to single-atom/metalated COFs, an emerging class of functionalized COFs that integrate atomically dispersed metal sites into COF skeletons, offering precise electronic modulation and enhanced electrocatalytic activity. The interplay between synthesis methodologies and their implications for COF quality and scalability is comprehensively examined. Furthermore, we establish a unified framework correlating the chemical structures (linkage types) and topological architectures (framework dimensionalities), as well as metal coordination environments in metalated COFs, with their distinct functionalities as sulfur hosts, separator modifiers, and anode protectors. By elucidating how specific structural motifs dictate polysulfide adsorption, catalytic conversion, ion transport, and lithium deposition behavior, this review aims to provide actionable design principles for developing next-generation COF materials. Finally, we outline critical challenges and future directions to guide the rational design of COFs toward practical high-energy-density and long-life Li-S batteries.