Guanidine-embedded poly(ionic liquid) as a versatile precursor for self-templated synthesis of nitrogen-doped carbons: Tailoring the microstructure for enhanced CO2 capture

A series of N-doped carbons coupled with ultra-micropores were synthesized through a self-templated strategy by employing the guanidine-embedded poly(ionic liquid) as the versatile precursor. The crosslinking agent (N,N’-methylene bisacrylamide (MBA)) and the ionic liquid monomer (1-(4-vinylbenzyl)-tetramethylguanidinium chloride) distributed in the polymeric frameworks exerted the functions of not only the pore-forming agents, but also the nitrogen sources during pyrolysis. With the cooperation of these two components, the derived carbon materials were endowed with well-developed microporosity and evenly-dispersed nitrogen species. Besides, the divinylbenzene (DVB) was also an indispensable moiety to maintain the skeleton stability in the initial heating stage. Inspiringly, when the carbonization temperature and amount of KOH activator were selected as 700 °C and 2 mol/L, a large specific surface area of 1606.1 m2/g, a high ultra-micropore (<0.7 nm) content of 0.4314 cm3/g along with abundant pyrrolic-N sites were attained, contributing to the appealing performance for CO2 capture. The adsorption capacity of the CTMG-700 achieved 3.95 mmol/g, and the selectivity toward CO2/N2 mixture (VCO2/VN2 = 15/85) was 20.4 at 25 °C and 1 bar. This strong affinity for CO2 molecules was credited to the superposition of van der Waals’ force inside narrow ultra-micropores as well as the hydrogen-bonding and acid-base interactions originated from pyrrolic-N. In addition, the CTMG-700 also demonstrated satisfactory cyclic adsorption performance under mild regeneration conditions. The present work was intended to uncover a new strategy to construct advanced carbonaceous materials via tailoring the microstructure of poly(ionic liquid)-based precursors for gas separation or specific applications.