Design strategy of polyamine for CO2 absorption guided by a novel descriptor of hydrogen bond strength

Abstract

Mixed amine solutions have been proposed as a promising method for improving the efficiency of CO2 adsorption. However, the process of experimentally screening the performance of different amine pairings can be labor-intensive. Here, a novel descriptor was proposed for the proton transfer energy barrier (Eb) to accelerate this process. The Eb of the proton transfer process was calculated using density functional theory (DFT) for 42 mixed systems. The independent gradient model based on Hirshfeld partition (IGMH) found the N–H⋯N type hydrogen bond (HB) is the dominant factor for the interactions. Based on the Atoms-In-Molecules (AIM) approach, the stronger the hydrogen bond, the lower the Eb of the proton transfer process. Three descriptors were identified (electron density (ρ-BCP), energy density (E(r)), and the electron localization function (ELF)) for linking the energy barrier to the strength of HBs. Surprisingly, this descriptor can also be applicable to tri-mixed amine systems, with a high square of the correlation coefficient (R2 > 0.8). Using this descriptor, the Eb of the proton transfer process for the quaternary mixed amines system was successfully predicted. We successfully build the relationship between the hydrogen bond strength and the reaction energy barrier, providing theoretical guidance for the design of mixed amines.