Single Crystals of a Two‐Dimensional Interpenetrated Covalent Organic Framework for Stabilizing Lithium Metal Anodes

ABSTRACT Constructing interpenetrated two‐dimensional (2D) organic covalent frameworks remains a significant challenge. Herein, single crystals of a novel crystalline covalent organic polymer ( CityU‐64 ) were synthesized, featuring an unusual twofold interpenetrated 2D architecture assembled from a tetrahedral ligand and linear linker through dative boron←nitrogen (B ← N) bonds. Single‐crystal X‐ray diffraction analysis reveals that two identical frameworks interpenetrate within the same plane to form an interlocked 2D layer. Furthermore, adjacent layers exhibit inter‐layer interdigitation, generating a hierarchically reinforced architecture with enhanced stability. The synergistic combination of intra‐layer interpenetration and inter‐layer interdigitation endows CityU‐64 with remarkable structural and chemical stability. Besides, the ether oxygen sites within the framework provide lithiophilic interactions that facilitate homogeneous lithium‐ion flux and uniform lithium deposition. Benefiting from these characteristics, CityU‐64 was employed as an artificial solid‐electrolyte interphase (ASEI) for lithium metal anodes. The modified lithium anode exhibits significantly improved electrochemical performance.