Study on CO2 capture performance and regeneration enhancement of ionic liquid/deep eutectic solvent composite absorbents

In this study, composite carbon dioxide (CO 2 ) absorbents were developed following a transferable design strategy involving a polyamine-rich ionic liquid (IL) scaffold, microstructure control via synthesis pathway, and optional nanofluid construction to tailor transport properties. Specifically, absorbents based on [TEPA·Lys] IL and deep eutectic solvents (DESs) were prepared. The effects of mass ratio, temperature, and other factors on absorption/regeneration performance were investigated. The results showed that the composite absorbent of [TEPA·Lys] and [EG/ChCl] with a mass ratio of 4:6 exhibited the optimal performance. At 298.15 K, the absorption capacity reached 102.55 mg CO 2 /g absorbent. However, the [TEPA·Lys][EG/ChCl] absorbent exhibited suboptimal cyclic regeneration performance. In order to seek effective ways of regeneration enhancement, the methods of altering the synthesis sequence and adding nanoparticles have been explored. The synthesis of [TEPA·Lys]@ChCl+EG showed relatively stable regeneration performance under optimal conditions. The results of density functional theory (DFT) calculations showed that [TEPA·Lys][EG/ChCl] has stronger CO 2 binding energy and lower absorption energy barrier, which is beneficial to the initial absorption. The [TEPA·Lys]@ChCl+EG has a lower desorption energy barrier, which is conducive to regeneration. As for the performance of nanofluids, it was found that the addition of 0.05 wt% carbon nanotubes (CNTs) can increase the absorption capacity of [TEPA·Lys][EG/ChCl] by 5.2 %, but the degree of regeneration enhancement was lower than the effect of synthesis sequence. This study provides experimental and theoretical insights for developing effective regeneration enhancement approaches for CO 2 absorbents.