Insight into the selective separation of CO₂ from biomass pyrolysis gas over metal-incorporated nitrogen-doped carbon materials: a first-principles study

The composition of biomass pyrolysis gas is complex, and the selective separation of its components is crucial for its further utilization. Metal-incorporated nitrogen-doped materials exhibit enormous potential, whereas the relevant adsorption mechanism is still unclear. Herein, 16 metal-incorporated nitrogen-doped carbon materials were designed based on the density functional theory calculation, and the adsorption mechanism of pyrolysis gas components H-2, CO, CO2, CH4, and C2H6 was explored. The results indicate that metal-incorporated nitrogen-doped carbon materials generally have better adsorption effects on CO and CO2 than on H-2, CH4, and C2H6. Transition metal Mo- and alkaline earth metal Mg- and Ca-incorporated nitrogen-doped carbon materials show the potential to separate CO and CO2. The mixed adsorption results of CO2 and CO further indicate that when the CO2 ratio is significantly higher than that of CO, the saturated adsorption of CO2 will precede that of CO. Overall, the three metal-incorporated nitrogen-doped carbon materials can selectively separate CO2, and the alkaline earth metal Mg-incorporated nitrogen-doped carbon material has the best performance. This study provides theoretical guidance for the design of carbon capture materials and lays the foundation for the efficient utilization of biomass pyrolysis gas.