Glucose-driven synthesis of N-doped porous carbon from sludge for CO2 removal in biomass syngas

Sewage sludge (SS), as a common solid waste with large production and rich organic nitrogen, has the potential to synthesize N-doped carbon (N-C) for CO 2 adsorption. In this paper, A novel synthesis method of N-C CO 2 adsorbent from SS by structural regulation of glucose (Glc) and further activating with K 2 CO 3 was proposed. Besides, the influence mechanism of N-doping form and content on CO 2 absorption capacity of N-C was studied by density functional theory calculations (DFT). Results showed that Glc had the effect of promoting the formation of internal mesoporous structure and adjusting pyrrole-N (N-5) structure into quaternary-N (N-Q) structure. The N-C prepared with feedstock mixing sludge, Glc and K 2 CO 3 powder (mass ratio of SS/Glc/K 2 CO 3  = 3:1:4) at 800 °C showed the highest CO 2 adsorption capacity (3.00 mmol/g at 25 °C and 1 bar) and superior CO 2 selectivity for CO 2 /CO/CH 4 under continuous flow. Theoretical calculations identified a nitrogen-doping threshold effect, where elevated nitrogen content strengthened pyridine-N (N-6) induction effects to enhance localized polarity for CO 2 adsorption. Conversely, lower doping levels amplify conjugation effects via N-5 prevalence, significantly improving adsorption capacity. This dual mechanism demonstrates that N-6 configurations optimize local polarity at high doping ratios, while N-5 architectures maximize electron delocalization efficiency at reduced nitrogen concentrations.