CO 2 Aggregation on Monoethanolamine: Observations from Rotational Spectroscopy.

The initial stages of the gas-phase nucleation between CO 2 and monoethanolamine were investigated via broadband rotational spectroscopy with the aid of extensive theoretical structure sampling. Sub-nanometer-scale aggregation patterns of monoethanolamine-(CO 2 ) n , n=1-4, were identified. An interesting competition between the monoethanolamine intramolecular hydrogen bond and the intermolecular interactions between monoethanolamine and CO 2 upon cluster growth was discovered, revealing an intriguing CO 2 binding priority to the hydroxyl group over the amine group. These findings are in sharp contrast to the general results for aqueous solutions. In the quinary complex, a cap-like CO 2 tetramer was observed cooperatively surrounding the monoethanolamine. As the cluster approaches the critical size of new particle formation, the contribution of CO 2 self-assembly to the overall stability increases.