Dynamic Microinterfacial Polymerization Enables Scalable Synthesis of Two‐Dimensional Polymer Sheets for Quasi‐Solid‐State Electrolytes in Sodium‐Metal Batteries

Organic two‐dimensional (2D) materials hold great potential in a broad range of applications. However, their practical utility is constrained by limited structural diversity and a lack of synthetic strategies. Herein, we report that simply stirring immiscible solutions of poly(propylene glycol)bis(2‐aminopropyl ether) and 1,3,5‐benzenetricarbonyl trichloride results in a dynamic microinterfacial polymerization that affords novel 2D polymer sheets (designated as PEO‐BTA). These sheets can be transformed to Na‐ion conducting materials via treatment with sodium hydride, followed by incorporation of a prototypical MOF, HKUST‐1, to obtain composite sheets (MOF@PEO‐BTA‐Na) that retain the structural integrity of the original 2D polymer sheets. The 2D composite sheets can be assembled into self‐supporting membranes and used as a quasi‐solid‐state electrolyte (QSSE) with a remarkably high ionic conductivity value of 2.80 × 10 −3 S cm −1 and a Na + transference number of 0.95. Consequently, the QSSE facilitates uniform Na plating in Na//Na and Na//Cu cells. Na//NaTi 2 (PO 4 ) 3 cells containing MOF@PEO‐BTA‐Na QSSE exhibit a high initial specific capacity (129.1 mAh g −1 at 0.5 C), superior rate capability (60.0 mAh g −1 at 20 C), and high‐capacity retention (92% after 1000 cycles at 1 C). This work establishes a new, scalable approach for synthesizing 2D organic sheets with promising applications in energy‐related areas.