Propanediamine-based absorbents with functionalized hydroxypropyl for efficient CO₂ capture via intramolecular synergy

Chemical absorption is currently the dominant industrialized technology for CO₂ capture. The development and application of efficient and energy-saving absorbents are crucial for the advancement of chemical absorption of CO₂. This study presents a novel propanediamine-based absorbent, N-(2-hydroxypropyl)-N-methyl-1,3-propanediamine (HPMAPA), achieved by functionalizing the secondary amine of N-methyl-1,3-propanediamine (MAPA) with hydroxypropyl group. Experimental results demonstrated that, compared to MAPA, HPMAPA exhibited improved stability, a 42% enhancement in cyclic CO₂ absorption capacity, and a 20% reduction in regeneration energy consumption, lowering it to 2.33 GJ·t⁻¹ CO₂. The structure–activity relationship of HPMAPA for CO₂ capture was revealed through structural deconstruction of HPMAPA. Moreover, the effect of intramolecular hydroxypropyl on the CO₂ capture performance of HPMAPA and the corresponding CO₂ capture mechanism were elucidated by density functional theory (DFT) calculations and quantitative NMR analysis. Such a newly developed propanediamine-based absorbent, with its efficient CO₂ capture performance, shows great potential for industrial applications.