Structural engineering of M-X4 moiety in conductive π-d metal-organic frameworks for electrochemical energy storage systems

Recently, conductive π-d metal-organic frameworks, featuring π-electron-rich organic linkers coordinated with d-orbital metal nodes, have emerged as potential materials for electrochemical energy storage systems, primarily owing to their exceptional electronic properties, enabling efficient charge delocalization and high conductivity, bridging the gap between traditional porous materials and conductive systems and offering a synergistic optimization of charge storage and ion transport capabilities. Nevertheless, significant challenges remain, including limited intrinsic conductivity, complex and labor-intensive synthesis processes, and structural instability. This review provides an in-depth overview of the recent advancements in the structural engineering of M-X 4 moiety in conductive π-d metal-organic frameworks for electrochemical energy storage systems, highlights the structural engineering of the M-X 4 coordination moiety as a central strategy to modulate electronic coupling, coordination geometry, and π-d conjugation pathways, meanwhile, examines how metal node and linker selection, M-X 4 coordination modulation, and linker functionalization (-OH, -NH 2 , -SH) influence charge transport and electrochemical performance. Moreover, advanced in-situ characterization and design strategies are discussed to reveal structure-property relationships. Furthermore, key challenges and future opportunities are also explored, emphasizing the potential of π-d MOFs in next-generation energy storage technologies.