A Phosphine‐Amine‐Linked Covalent Organic Framework with Staggered Stacking Structure for Lithium‐Ion Conduction

Abstract

AbstractIn‐plane ionic conduction over two‐dimensional (2D) materials is desirable for flexible electronics. Exfoliating 2D covalent organic frameworks (COFs) towards a few layers is highly anticipated, whereas most examples remain robust via π‐stacking against the interlayered dislocation. Herein, we synthesize a phosphine‐amine‐linked 2D COF by a nucleophilic substitution reaction of phosphazene with amines. The synthesized COF is crystalline, and stacks in an AB‐staggered fashion, wherein the AB dual layers are interlocked by embedding P−Cl bonds from one to another layer, and the non‐interlocked layers are readily delaminated. Therefore, in situ post‐quaternization over phosphazene can improve the ionization of backbones, accompanied by layered exfoliation. The ultrathin nanosheets can decouple lithium salts for fast solid‐state ion transport, achieving a high conductivity and low activation energy. Our findings explore the P−N substitution reaction for COF crystallization and demonstrate that the staggered stacking 2D COFs are readily exfoliated for designing solid electrolytes.