Modulated synthesis of N-doped porous carbons via rational design of the poly(ionic liquid) precursors towards efficient CO₂ separation

A ternary copolymerized poly(ionic liquid) of bis-imidazolium-based ionic liquid and crosslinking agents (divinylbenzene (DVB), N, N′-methylene bisacrylamide (MBA)) was rationally designed as versatile precursor to synthesize nitrogen-doped porous carbons by self-templating method for efficient CO₂ separation. The ionic liquid monomer and MBA could serve as nitrogen sources to enhance the surface polarity through in-situ doping, while the self-decomposed functional groups (especially -CONH-) along with halogen anions could promote the formation of pores during carbonization. By adjusting the molar ratio of ionic liquid to DVB and MBA, carbonization temperature and activator dosage (KOH), the obtained CVDM_0.5-700 (0.5:1:1, 700 °C, 2 mol/L) owned a considerable specific surface area (1835 m²/g), plentiful (ultra)micropores and moderate nitrogen content (3.05 wt%). The strong van der Waals force arising from ultra-micropores (d<0.7 nm) within a narrow distribution improved the ability to capture CO₂ and the abundant CO₂-philic N species further strengthened the binding interactions. Consequently, CVDM_0.5-700 was endowed with satisfactory CO₂ uptake capacity (4.11 mmol/g), desirable CO₂/N₂ (15%/85%) adsorption selectivity (23.6) and excellent cyclic stability at 25 °C and normal pressure. This work provided a new pathway for the modulated fabrication of heteroatoms-doped porous carbon materials by precise design of poly(ionic liquid)-based precursors for appealing applications.