Mesoscopic Structure Facilitates Rapid CO Transport and Reactivity in CO Capture Solvents.

Mass transfer coefficients of CO are anomalously high in water-lean solvents as compared to aqueous amines. Such phenomena are intrinsic to the molecular and nanoscale structure of concentrated organic CO capture solvents. To decipher the connections, we performed in situ liquid time-of-flight secondary ionization mass spectroscopy on a representative water-lean solvent, 1-((1,3-Dimethylimidazolidin-2-ylidene)amino)propan-2-ol (IPADM-2-BOL). Two-dimensional (2D) and three-dimensional (3D) chemical mapping of the solvent revealed that IPADM-2-BOL exhibited a heterogeneous molecular structure with regions of CO-free solvent coexisting with clusters of zwitterionic carbonate ions. Chemical mapping were consistent with molecular dynamic simulation results, indicating CO diffusing through pockets and channels of unreacted solvent. The observed mesoscopic structure promotes and enhances the diffusion and reactivity of CO, likely prevalent in other water-lean solvents. This finding suggests that if the size, shape and orientation of the domains can be controlled, more efficient CO capture solvents could be developed to enhance mass-transfer and uptake kinetics.