Effect of Chain Topology of Polyethylenimine on Physisorption and Chemisorption of Carbon Dioxide

Polyethylenimine (PEI) is a promising candidate for CO2 capture. In this work, the physisorption and chemisorption of CO2 on various low‐molecular‐weight PEIs are investigated to identify the effect of chain architecture on sorption. The reliability of theoretical calculations are partially supported by our experimental measurements. Physisorption is calculated independently by the reference interaction‐site model integral equation theory; chemisorption is distinguished from the total sorption given by the quantum density functional theory. It is shown that, as the chain length increases, both chemisorption and physisorption drop off nonlinearly, but the decay amplitude of chemisorption is more apparent. Conversely, as the amine group approaches the central triamine unit of each oligomer, the sorption capacity decreases, affecting the sorption equilibrium in a complex way. This arises from the cooperative contribution of an increased steric effect and renormalized electronic distribution. Absorbing stuff: The CO2 sorption capacity of sites in a polyethylenimine chain varies. As the polymer chain length increases, both physisorption and chemisorption capacities per unit decline, and the drop ratio of chemisorption is more apparent than that of physisorption.