Development of in situ polymerized amines into mesoporous silica for direct air CO2 capture

• CO2 adsorption was studied on in-situ polymerized amine into mesoporous silica. • Kinetics of adsorption of CO2 at different relative humidity values was analyzed. • The material showed a high CO2 uptake at ultralow concentration of 400 ppm. • The maximum CO2 uptake was obtained at 25 °C and 65% relative humidity. • The sorbent showed good stability and complete regenerability after ten cycles. Direct air CO 2 capture (DAC) is inevitable to achieve negative emissions and lower CO 2 concentration in the atmosphere. The use of class III supported amine materials has shown great potential as effective materials for CO 2 capture from both flue gas and low concentrations of CO 2 . In this work, a linear polyethylene amine tethered to mesoporous silica foam was synthesized by controlled in situ cationic ring opening polymerization of 2-methyl-2-oxazoline. The sorbent was characterized based on porosity, FTIR, elemental analysis, and surface morphology. The CO 2 capture performance at different temperatures was measured using a volumetric method, whereas the dynamic breakthrough analysis (DBA) technique was evaluated using simulated air of 400 ppm CO 2 at different temperatures and relative humidities. The CO 2 adsorption isotherms were studied in the temperature range from 5 to 80 °C and were fitted using different isotherm models. To evaluate the effects of moisture on the CO 2 capture performance, breakthrough experiments were performed using 400 ppm CO 2 at various relative humidities (0–65%). It was found that the CO 2 uptake calculated from the breakthrough experiment is enhanced at higher moisture contents and decreases at higher temperatures. The maximum CO 2 uptake was 1.50 mmol/g at 25 °C and 65% RH. The CO 2 adsorption kinetics of the sorbent was found to follow the Avrami model, whereas the dual site Langmuir model was found to be the best fit for the adsorption isotherms. The developed sorbent exhibited a stable cyclic performance and retained its initial CO 2 uptake during 10 consecutive cycles. This study demonstrates that in situ polymerization of amines into porous supports is a viable route for designing sorbents with high CO 2 adsorption performance for DAC applications.