Facile preparation of N-doped porous carbon from chitosan and NaNH2 for CO2 adsorption and conversion

Although N-doped porous carbon has been widely studied in CO2 capture and conversion, the preparation process of functionalized porous carbon is usually complicated and costly, which limits the large-scale industrial application of porous carbon. Here, we reported a straightforward method for the preparation of N-doped porous carbon using chitosan (CTS) and NaNH2 without any solvents. The structure of N-doped porous carbon was characterized by XRD, XPS, SEM, TEM and pore structure analysis, respectively. The developed pore structure and specific surface area of N-doped porous carbon are mainly due to the use of NaNH2 as both porogen and nitrogen source during carbonization. These prepared porous carbons are used to study the adsorption of CO2, SO2, H2S and CH4. The adsorption capacity of CO2 can reach 6.33 mmol·g−1 at 273.15 K and 100 kPa, which is significantly higher than that of carbon-based adsorbents reported in the literature. The thermodynamics and mechanism of CO2 adsorption are also discussed. The results suggest that the adsorption of CO2 by N-doped porous carbon is a physical adsorption process. In addition, a metal-free conversion of CO2 into formamides is also acquired using N-doped porous carbon as promoter, giving various corresponding formamides in moderate to excellent yields. As a result, the excellent CO2 uptake, high reactivity, low cost of precursor, and facile synthesis strategy prove that these chitosan-based N-doped porous carbons are a potential candidate for CO2 capture and conversion.