Urea-Modified Lignin-Derived Nitrogen-Doped Porous Carbon Materials: Synthesis and CO2 Adsorption Properties

Lignin has a high carbon content, but the production of porous carbon materials from it is challenging because of its complex structure and stable physicochemical properties. In this study, nitrogen-doped porous carbon materials are prepared by impregnating lignin with urea, using potassium hydroxide (KOH) as an activator. The physicochemical properties of the samples are investigated using various characterization methods. The results showed that the CO 2 adsorption capacity of the sample LUN-10-7, which has a urea solution concentration of 10% and an immersion time of 7 days, is 3.80 mmol g −1 at 1 bar and 298 K. The characterization results indicated that the abundant pore structure and excellent surface chemistry enhanced the sample's CO 2 adsorption performance. Additionally, the sample demonstrated high CO 2 /N 2 selectivity and cyclic stability, making it suitable for practical applications as an adsorbent.