Activation Effect of Fullerene C60 on the Carbon Dioxide Absorption Performance of Amine-Rich Polypropylenimine Dendrimers

Converting amine-rich compounds into highly effective carbon dioxide (CO2) sorbents requires a better understanding and control of their properties. The reaction of fullerene C-60 with polyethyleneimine converts the polymer into a high-performance CO2 sorbent. In this study, experimental evidence is reported for the activation effect of C-60 on the amine moieties of the polymer. To do so, polypropylenimine (PPI) dendrimers that allowed for a systematic comparison of molecular composition and CO2 absorption were used. The addition of C-60 to PPI to form PPI-C-60 results in a reduction of the energy barrier of CO2 absorption, but also in a parallel decrease in the frequency of successful collisions between CO2 and PPI-C-60 due to a possible disruption of the hydrogen-bonding network of amino groups and bound water in PPI. This finding supports the existence of a non-affinity repulsive effect between hydrophobic C-60 and hydrophilic amines that forces them to be actively exposed to CO2.