Metal-Covalent Organic Frameworks: Design Strategy, Structure Feature, and Applications in Energy Storage.

Metal-covalent organic frameworks (MCOFs), which can integrate the properties of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), exhibit high stability, adjustable pore structures, and catalytic activity of metal sites owing to the synergistic interaction between metal sites and covalent backbones. In this regard, MCOFs have gained significant attention as promising electrode materials, where metal ions (Mn+) function as molecular structure switches, providing MCOFs with diverse active sites and modifying their charge density by incorporating different Mn+, thereby imparting unique energy-storage properties to MCOFs. Furthermore, by optimizing the synthesis strategies of MCOFs, their topological and dimensional structures can be regulated to ensure the stability of the MCOFs. In the challenging landscape of energy storage, MCOFs have surpassed the performance limitations of traditional COFs. Through precise atomic-level control of metal sites and innovative design of dynamic covalent chemistry, they can significantly enhance the performance of batteries, achieving remarkable performance in lithium-ion batteries (LIBs), lithium-sulfur batteries, and other applications. This review systematically summarizes the research advancements of MCOFs in high-performance energy storage devices, including lithium-ion, Li-CO2, and Zn-ion batteries. In addition, it examines the synthesis strategies, structural regulation, and structural characteristics of MCOFs to address the challenges encountered in various energy storage devices.