Semiconducting Crystalline Two-Dimensional Polyimide Nanosheets with Superior Sodium Storage Properties

The efficient synthesis of crystalline two-dimensional polymers (2DPs) with designed structures and properties is highly desired but remains a considerable challenge. Herein, we report the synthesis of two-dimensional polyimide (2DPI) nanosheets via hydrogen-bond-induced preorganization and subsequent imidization reaction. The formed intermolecular hydrogen bonds can significantly improve the internal order and in-plane periodicity of 2DPI. The crystalline few-layer 2DPI nanosheets are micrometer-size, solvent dispersible, and thermally stable. Interestingly, the 2DPI with π-conjugation shows a favorable bandgap of 2.2 eV and can function as a p-type semiconducting layer in field-effect transistor devices with an appreciable mobility of 4.3 × 10^-3 cm² V^-1 s^-1. Furthermore, when explored as a polymeric anode for sodium-ion batteries, the 2DPI exhibits ultrahigh capacity (312 mAh g^-1 at 0.1 A g^-1), impressive rate capability (137 mAh g^-1 at 10.0 A g^-1), and excellent cycling stability (95% capacity retention after 1100 cycles) due to its robust 2D conjugated porous structure, outperforming most organic/polymeric anodes ever reported. This work provides a versatile strategy for synthesizing 2DP nanosheets with promising electronics and energy-related applications.