Functionalized Polysilsesquioxane-Based Hybrid Silica Solid Amine Sorbents for the Regenerative Removal of CO₂ from Air

Functionalized polysilsesquioxane-based hybrid silica materials are presented as solid amine sorbents for direct CO₂ capture from air. The sorbent was synthesized from amine and vinyl functionalized alkoxysilanes by a simple, energy efficient, and cost-effective co-condensation method. The material, containing bound amine functionalities, was found to have a selective CO₂ capturing capacity of 1.68 mmol/g from atmospheric air with an adsorption half time of 50 min. This material also showed a maximum adsorption capacity of 2.28 mmol/g in pure CO₂ and 1.92 mmol/g in 10% CO₂. Desorption started at a temperature as low as 60 °C, and complete desorption occurred at 80 °C. The sorbent exhibited high recycling ability, and 100 cycles of adsorption/desorption were demonstrated in pure CO₂ and 50 cycles in ambient air without any loss in efficiency.