Two-dimensional MOF-based materials: Preparations and applications as electrodes in Li-ion batteries

Two-dimensional (2D) metal-organic frameworks (MOFs) are rapidly emerging as a unique class of mushrooming family of 2D materials offering distinctive features, such as hierarchical porosity, extensive surface area, easily available active sites, and versatile, adaptable structures. These promising characteristics have positioned them as highly appealing alternatives for a wide range of applications in energy storage technologies, including lithium batteries. Nevertheless, the poor conductivity and limited stability of 2D MOFs have limited their real applications in electrochemical energy storage. These limitations have therefore warranted ongoing research to enhance the performance of 2D MOFs. Given the significance of 2D MOF-based materials as an emerging class of advanced materials, a multitude of strategy has been devised to address these challenges such as synthesizing 2D conductive MOFs and derivatives along with 2D MOF hybridization. One promising approach involves the use of 2D MOF derivatives, including transition metal oxides, which due to their abundant unsaturated active metal sites and shorter diffusion paths, offer superior electrochemical performance. Additionally, by combining pristine 2D MOFs with other materials, hybrid 2D MOF materials can be created. These hybrids, with their enhanced stability and conductivity, can be directly utilized as active materials in lithium batteries. In the present review, we categorize 2D MOF-based materials into three distinct groups: pristine 2D MOFs, 2D MOF-derived materials, and 2D MOF hybrid materials. The synthesis methods for each group, along with their specific applications as electrode materials in lithium-ion batteries, are discussed in detail. This comprehensive review provides insights into the potential of 2D MOFs while highlighting the opportunities and challenges that are present in this evolving field.