In Situ Construction of Amide-Functionalized 2D Conjugated Metal-Organic Frameworks with Multiple Active Sites for High-Performance Potassium-Ion Batteries.

Abstract

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) represent a promising class of electrode materials for potassium-ion batteries (PIBs), attributed to their superior conductivity, large specific surface area, high charge carrier mobility, and tunable active sites. However, most reported 2D c-MOF-based cathode materials for PIBs usually encounter challenges, such as low specific capacity and inadequate cycling stability. In this context, we herein designed and synthesized a new hexahydroxy salicylamide ligand (6OH-HBB) via a straightforward two-step synthesis with a high yield of 93%, which was subsequently utilized to construct a 2D Cu-HBB-MOF with multiple active sites through an in situ metal coordination-induced planarization strategy. Thanks to its abundant active sites and large specific surface area, the Cu-HBB-MOF demonstrated an outstanding high initial capacity of 228.1 mA h g-1 at 0.2 A g-1, surpassing most reported porous material-based PIBs. Furthermore, even at 5.0 A g-1, the Cu-HBB-MOF exhibited a large reversible specific capacity of 103.6 mA h g-1 after 2500 cycles, simultaneously maintaining a low-capacity loss of only 0.011% per cycle and achieving a Coulombic efficiency up to 100%, demonstrating good long-term cycle stability. This work provides fundamental insights into engineering 2D c-MOFs with multisite functionality, charting a new course for developing high-performance MOF-based cathodes in next-generation energy storage systems.