Sustainable CO₂ Capture: N,S-Codoped Porous Carbons Derived from Petroleum Coke with High Selectivity and Stability

CO₂ capture from the flue gas is a promising approach to mitigate global warming. However, regulating the carbon-based adsorbent in terms of textural and surface modification is still a challenge. To overcome this issue, the present study depicts the development of cost-effective and high-performance CO₂ adsorbents derived from petroleum coke, an industrial by-product, using a two-step process involving thiourea modification and KOH activation. A series of N,S-codoped porous carbons was synthesized by varying activation temperatures and KOH quantity. The optimized sample exhibited a high specific surface area of 1088 m²/g, a narrow micropore volume of 0.52 cm³/g, and considerable heteroatom doping (1.57 at.% nitrogen and 0.19 at.% sulfur). The as-prepared adsorbent achieved a CO₂ adsorption capacity of 3.69 and 5.08 mmol/g at 1 bar, 25 °C and 0 °C, respectively, along with a CO₂/N₂ selectivity of 17. Adsorption kinetics showed 90% of equilibrium uptake was achieved within 5 min, while cyclic studies revealed excellent stability with 97% capacity retention after five cycles. Thermodynamic analysis indicated moderate isosteric heat of adsorption (Q) values ranging from 18 to 47 kJ/mol, ensuring both strong adsorption and efficient desorption. These findings highlight the potential of petroleum coke-derived porous carbons for sustainable and efficient CO₂ capture applications.