Hydrothermal synthesis of nitrogen-doped ordered mesoporous carbon <i>via</i> lysine-assisted self-assembly for efficient CO₂ capture

Abstract

Nitrogen-doped ordered mesoporous carbons (NOMCs) were synthesized by single-step hydrothermal self-assembly using F127 as a soft template, hexamine as a formaldehyde source, l-lysine as a polymerization catalyst, and 3-aminophenol as both carbon and nitrogen sources. The microstructure of the NOMCs was characterized by XRD, N₂ adsorption/desorption, TEM, FTIR, and XPS. The results indicated that the obtained NOMCs exhibited a large specific surface area, uniform pore size distribution and highly ordered 2-D hexagonal mesostructure (<i>P</i>6<i>mm</i>). Besides, the nitrogen was uniformly doped into the carbon framework in the form of various nitrogen species. The adsorption isotherms of CO₂ and N₂ were also determined and could be well fitted by a DSL model. The capture capacity of CO₂ was affected by both the nitrogen content and mesostructure of the adsorbents. Overall, NOMC-L-0.5 displayed excellent CO₂ capture capacity (0 °C, 3.32 mmol g^-1; 25 °C, 2.50 mmol g^-1), and still demonstrated great regenerability with only 2% loss after several CO₂ adsorption/desorption cycles. Moreover, the CO₂/N₂ selectivity calculated by IAST was as high as 43.2 at 25 °C in a typical composition of flue gas (binary mixtures with 15% CO₂). The superior adsorption performance enables NOMCs to be a promising CO₂ adsorbent in practical applications.