Framework-to-Carbon Conversion Strategy for Nitrogen-Silicon Co-Doped Microporous Carbons with Superior Energy Storage Performance

Abstract

Developing heteroatom-doped porous carbons with tailored architecture is a promising strategy to enhance energy storage performance in next-generation supercapacitors. Herein, we report the design and synthesis of two nitrogen-silicon co-doped microporous carbons (NSi@C-1 and NSi@C-2) prepared from silicon-containing covalent triazine frameworks (Si-CTFs). These Si-CTFs frameworks were constructed through the condensation of 4,4′,4″,4‴silanetetrayltetrabenzaldehyde (Si-4CHO) with two different carboximidamide linkers, namely terephthalimidamide (TP-2NHNH 2 ) and [1′-biphenyl]-4,4′-dicarboximidamide (BP-2NHNH 2 ), resulting in tunable porosity and distinct structural architectures. The direct carbonization route enables uniform incorporation of N and Si heteroatoms within a hierarchical porous network, simultaneously improving electrical conductivity and redox activity. NSi@C-2, featuring an extended biphenyl linker, exhibited a higher surface area (732 m 2 g⁻ 1 ), larger pore volume (0.59 cm 3 g⁻ 1 ), and lower charge-transfer resistance (4.23 S cm⁻ 1 ) than NSi@C-1. Owing to these structural features, the material exhibits exceptional electrochemical properties, achieving a specific capacitance of 403 F g⁻¹ at 0.5 A g⁻ 1 and retaining 96.6% of its initial capacitance after 6000 charge-discharge cycles in the three-electrode system. A symmetric NSi@C-2-based supercapacitor device further delivered a high capacitance of 211 F g⁻¹, an impressive energy density of 152 Wh kg⁻¹ at a power density of 1037 W kg⁻¹, and exceptional cycling stability (93.84% retention after 4000 cycles). The synergistic effects of hierarchical porosity, extended π-π conjugation, and N-Si dual-doping collectively endow NSi@C-2 with superior ion diffusion, efficient electron transport, and abundant active sites. This study establishes a facile frameworkto-carbon conversion strategy for constructing multifunctional heteroatom-doped carbons with tunable porosity and electronic properties for advanced energy-storage applications.