CO₂ adsorption by dendrimers bound to mesoporous substrates

Chemical absorption, by amine solvents has long been used by industry for acid gas removal. Amine-based chemical solvents absorb CO₂ very selectively. However, regeneration of the solvents is energy-intensive and is also plagued by the generation of corrosive by-products. Recently, solid adsorbents based on amine functionalized substrates have been proposed as a possible means of overcoming these limitations via the Pressure Swing Adsorption (PSA) process. This paper reports an investigation of CO₂ adsorption efficiencies for a stepwise growth series of amine terminated melamine-based dendrimers that have been iteratively grown (generations 0 to 4) within the channels of mesocelluar siliceous foam (MCF). The CO₂ adsorption efficiencies of the materials were determined from thermogravimetric analysis (TGA). Heats of CO₂ adsorption, measured by differential thermal analysis (DTA), are in the range of 30 - 55 kJ.mol^-1 and are substantially higher than for underivatised MCF (13 kJ.mol^-1). This suggests that some chemisorption interactions take place during adsorption. The heats of adsorption are considerably less than those reported for amine solvents, suggesting that, with these materials, the energy requirement for sorbent regeneration will be lower.