Heteroatom-N,S co-doped porous carbons derived from waste biomass as bifunctional materials for enhanced CO2 adsorption and conversion

Biochar, a sustainable porous material, can be modified by doping heteroatomic active sites into the skeleton to make it equip specific properties. In this work, a series of N,S co-doped porous carbons were prepared by two-step carbonization method, using waste distiller's grains as raw material and thiourea as N and S source. The effects of activation temperature, activator dosage, and thiourea dosage on the structure and CO2 uptake of porous carbons were investigated, respectively. The results showed that the prepared N,S co-doped porous carbon with the high CO2 adsorption capacity was due to abundant micropores and the high specific surface area. Notably, NSAC-(1:1)550(1) exhibited the highest CO2 uptake of 7.02 mmol·g−1 at 273.15 K and 1 bar, which was higher than that of the same type of biochar adsorbent reported in the literature. More importantly, these N,S co-doped porous carbons can also be used as a recyclable promoter for the cycloaddition of CO2 with epoxide, affording the cyclic carbonates with up to 99 % yield under solvent-free conditions. This study provides a sustainable scheme for the development of low-cost bifunctional carbon materials to achieve efficient CO2 capture and conversion.