Role of heteroatoms (nitrogen and sulfur)-dual doped corn-starch based porous carbons for selective CO₂ adsorption and separation

Herein, we have produced two series of novel materials including heteroatoms-doped (thiourea-modified) and heteroatoms-deprived microporous carbons using three different potassium salts activators (KOH, K₂CO₃, K₂C₂O₄). The experimental results reveal that thiourea-modified KOH activated sample exhibit excellent textural features (specific surface area∼1795 m²/g, micropore volume∼0.82 cm³/g) but at the expense of a reduced heteroatom content. However, sample prepared with K₂C₂O₄ exhibited a comparable specific surface area (∼1747 m²/g), enough population of narrow micropores (<1.0 nm), the highest micropore volume (0.93 cm³/g) and a high nitrogen (4.6 at. %) and sulfur content (2.3 at. %). Therefore, the optimized sample, STO, exhibits remarkable CO₂ adsorption (269.61 mg/g at 0 °C and 1 bar), excellent IAST CO₂/N₂ selectivity (73), high isosteric heat of adsorption (39.3 kJ/mol) and high cyclic stability, surpassing the CO₂ adsorption/separation performance of most of the biomass-derived carbons. Herein, for the first time, a comprehensive study on potassium salts activation, in comparison with the conventionally practiced KOH activation, is presented. Concluding, the experimental results unveiled K₂C₂O₄ as a more competitive and less corrosive potassium salt activating agent by virtue of its ability to fabricate N, S dual-doped highly porous carbons for efficient CO₂ adsorption and separation.