Abstract The energy penalties associated with the liquid amines carbon dioxide absorption are huge which could be minimised by using materials based carbon capture adsorption. A facile one-step approach for the preparation of activated porous carbon spheres through direct carbonization of d -glucose with a novel non-corrosive chemical, potassium acetate for carbon dioxide capture is presented here. The amount of potassium acetate is varied to control the chemical structure, morphology, porosity and textural features. The potassium acetate/ d -glucose impregnation ratio of 3 is optimum condition for obtaining activated porous carbon spheres with high specific surface area (1917 m2 g−1), spherical morphology, and specific pore volume (0.85 cm3 g−1). The activated porous carbon spheres prepared using different glucose to potassium acetate ratios are employed as carbon dioxide adsorbents. Among all, activated porous carbon spheres prepared with the potassium acetate/ d -glucose of 3 registers the best performance and exhibits carbon dioxide adsorption capacities of 1.96 and 6.62 mmol g−1 at 0 °C/0.15 bar and 0 °C/1 bar. It also shows impressive carbon dioxide adsorption at 0 °C/30 bar (20.08 mmol g−1) and 25 °C/30 bar (14.08 mmol g−1). This performance is attributed to highly developed porous structure of the optimized material. Low isosteric heat of adsorption (24.8–23.04 kJ mol−1) means physisorption which suggests lower energy penalties for material regeneration. A non-complicated synthesis and high carbon dioxide capture demonstrate the importance of this work. This synthesis strategy may be utilized to prepare porous carbons from other precursors which could find potential in energy-related applications.