Adsorption of CO2 on mechanochemically synthesized silicon oxycarbide composites

The present study explores the mechanochemical synthesis of porous silicon oxycarbide composites using commercial activated carbon and hydrated silica as precursors without additional functionalization, aiming to be used as effective adsorbents for carbon dioxide removal from gas streams. By adjusting the hydrated silica/activated carbon mass ratio, a set of materials were prepared with varying surface areas (256–662 m²/g), pore volumes (0.28–0.45 cm³/g), and surface functional groups concentrations (0.824–0.996 mmol/g). The optimal silicon oxycarbide composite (hydrated silica/activated carbon mass ratio of 1.5) demonstrated the CO₂ adsorption capacity of 3.41 mmol/g at 25 °C and 1 bar, which can be attributed to the composite’s well-developed porosity and high surface functionality. In addition, the adsorbent exhibited high CO₂/N₂ selectivity of 15.2 along with stable cycling performance. These findings indicate that mechanochemically synthesized silicon oxycarbide composites have a considerable potential in the field of CO₂ capture.