The effect of B/N co-doping in lignin-derived carbon on CO2 sorption from flue gas

Since the extensive utilization of fossil fuels has led to a sharp increase in atmospheric CO 2 levels, controlling CO 2 emissions has garnered widespread attention. Carbon materials, as important CO 2 adsorbents, are often functionalized with heteroatoms such as N and B. However, the influence of B/N co-doping on CO 2 sorption remains unclear. In this study, a series of B/N co-doped lignin-derived carbons were synthesized via a one-pot pyrolysis using alkali lignin as the precursor and boric acid and glutamic acid as B and N dopants, respectively. The prepared samples were characterized using SEM, XPS, FTIR, and Raman spectroscopy. B/N co-doping enhanced the specific surface area, pore volume, and crystallinity of the carbon while introducing new surface functional groups such as BC 2 O and BCO 2 , without significantly altering the types or relative content of N-containing functional groups. The CO 2 adsorption capacity of B/N co-doped lignin-based carbon reached 1.72 mmol/g at 25 °C under 1 bar, which was 5.9 times higher than that of unmodified lignin-based carbon (0.25 mmol/g). Density functional theory (DFT) calculations revealed that B-containing functional groups enhanced the nucleophilicity of B and the electronegativity of surrounding atoms (especially O). N-containing functional groups, especially pyridinic-N (N-6) and pyrrolic-N (N-5), which have high adsorption energies, could avoid excess B oxidation and provide Lewis base sites for CO 2 sorption.