Differentiation of Chemisorption and Physisorption of Carbon Dioxide on Imidazolium-type Poly(ionic liquid) Brushes

Amine-functionalized imidazolium-based poly(ionic liquid) brushes on mesoporous silica were synthesized via “grafting through” technique and were applied as model sorbents to understand physisorption and chemisorption of carbon dioxide molecules. The experimental results reveal that the total adsorption capacity of model sorbents derived from temperature programmed desorption (TPD) approach reaches 1.72 mmol·g −1 that is much higher than the sum of adsorption capacity of bare mesoporous silica and free polymers at 25 °C under carbon dioxide partial pressure of 0.2 bar. The proposed physical adsorption and chemical adsorption of carbon dioxide molecules in TPD response curves were validated by volumetric desorption measurement. It is also observed that physical adsorption is completely reversible and chemical adsorption is irreversible. The results demonstrate that the temperature programmed desorption technique is an effective approach to differentiate chemisorption and physisorption of gaseous species on solid sorbents, which is beneficial for understanding of adsorption mechanism and materials design.