Selective Carbon Dioxide Capture Using Silica-Supported Polyaminals

The development of a stable CO₂ sequestration material is an urgent need for effective CO₂ capture applications. In this sense, the silica supported materials are envisaged as promising materials. In this work the synthesis of silica supported polyaminals (Si-PA-1 and Si-PA-2) by single step condensation is achieved and characterized by FT-IR and solid-state NMR spectral techniques. The surface morphology and crystallinity are studied using SEM and PXRD techniques. The BET surface of the Si-PA-1 and Si-PA-2 is around 155 m²/g which is demonstrated using N₂ adsorption. The CO₂ uptake for Si-PA-1 and Si-PA-2 are observed around 45 mg/g. The high selectivity of CO₂ over N₂ (180.6) and considerable selectivity of CO₂ over CH₄ (38.7) are observed. Two types of adsorption isotherm models (Langmuir and Freundlich model) are used to evaluate isotherm parameters. Thermodynamic parameters such as Gibb's free energy, change in enthalpy and entropy are calculated from Van't Hoff equation and these results suggest that the adsorption is spontaneous and exothermic process. The physical interaction between Si-PAs and CO₂ is confirmed by the heat of adsorption (37-22 KJ/mol) evaluated from Clausius–Clapeyron equation.