Solvent-free synthesis of N-containing polymers with high cross-linking degree to generate N-doped porous carbons for high-efficiency CO₂ capture

Nitrogen-containing polymers with high cross-linking degrees are attractive precursors for the preparation of N-doped porous carbons (NDPCs), while their synthesis in liquid phases is difficult. Moreover, the difference between liquid-phase synthesis and solvent-free synthesis has not been well clarified. Herein, a solvent-free strategy was employed for the synthesis of an N-containing polymer from 1,3,5-tris(chloromethyl)-2,4,6-trimethylbenzene and p-phenylenediamine (producing NUT-71-F) and compared thoroughly with the liquid-phase method. NUT-71-F exhibited obviously higher yield than the counterpart NUT-71-S produced in the solvent (70.8% vs. 49.8%) due to the greater crosslinking degree and different linkage ways. The NDPCs based on NUT-71-F presented higher yields, more developed porosities, and better CO₂ adsorption capacities in contrast to their analogues from NUT-71-S. The NUT-71-F-700 obtained from carbonization at 700 °C showed an excellent CO₂ uptake of 8.1 mmol/g at 273 K and 1 bar, which is apparently higher than NUT-71-S-700 (5.4 mmol/g) and various benchmarks.