Nano-encapsulated solvent via pickering emulsion in NaOH aqueous solution for indoor CO₂ capture

Considering the limitations of indoor ventilation owing to air pollution, CO₂ concentration rises rapidly to 3000 ppm, which is a level that can affect human health. It is essential to develop materials to reduce naturally occurring CO₂ in the buildings. Herein, a nano-encapsulated solvent (NES) via Pickering emulsion is proposed for indoor CO₂ capture. NaOH aqueous solution is wrapped with hydrophobic surface-functionalized SiO₂ (HS-SiO₂) nanoparticles, and the corrosiveness of NaOH is not caused by HS-SiO₂ wall. CO₂ capture capacity of NES-NaOH is evaluated as 7.57 mmol-CO₂/g-solvent which is the highest compared to other solvents including metal-organic frameworks (MOFs); it exhibits excellent structural stability in terms of temperature, time, moisture, and CO₂ reaction. NES-NaOH presents high selectivity toward CO₂ molecules due to the characteristics of NaOH with high gas permeability of macroporous silica wall and it is dispersed in a silicone oil harmless to human body. It is concluded that NES-NaOH can be successfully applied to air purifier filter to control the CO₂ concentration in buildings.