Design of biomass-based N, S co-doped porous carbon via a straightforward post-treatment strategy for enhanced CO2 capture performance

Biomass-based adsorbents are considered to have great potential for CO2 capture due to their low cost, high efficiency and exceptional sustainability. The aim of this work is to design a simple method for preparing biomass-based adsor-bents with abundant active sites and large numbers of narrow micropores, so as to enhance CO2 capture performance. Herein, N, S co-doped porous carbon (NSPC) was created utilizing walnut shell-based microporous carbon (WSMC) as the main framework and thiourea as N/S dopant through physical grinding and post-treatment process at a moderate temperature without any other reagents and steps. By altering the post-treatment parameters, a series of porous car -bons with varying physico-chemical properties were prepared to discuss the roles of microporosity and N/S functional groups in CO2 adsorption. NSPC with narrow micropore volume of 0.74 cm3 g-1, N content of 4.89 % and S contents of 0.71 % demonstrated the highest CO2 adsorption capacity of 7.26 (0 degrees C) and 5.51 mmol g-1 (25 degrees C) at 1 bar. Mean-while, a good selectivity of binary gas mixture CO2/N2 (15/85) of 29.72 and outstanding recyclability after ten cycles of almost 100 % adsorption capacity retention were achieved. The proposed post-treatment method was beneficial in maintaining the narrow micropores and forming N/S active sites, which together improve the CO2 adsorption perfor-mance of NSPC. The novel NSPC displays amazing CO2 adsorption characteristics, and the practical, affordable synthetic approach exhibits significant potential to produce highly effective CO2 adsorbents on a broad scale.