Rapid and high-capacity absorption of SO₂ by deep eutectic solvents bound to tertiary amine sites

Rapid and efficient absorption of SO2 by deep eutectic solvents (DESs) is highly desirable but extremely chal-lenging. In this work, novel DESs bound to several tertiary amine sites were synthesized by mixing methylated polyethyleneimine (mPEI) and tris(2-(2-methoxyethoxy)ethyl)amine (TDA) at different mass ratios (2:1, 1:1, and 1:2). The synthesized DESs with low viscosity achieved efficient SO2 absorption. In particular, excellent ab-sorption capacities were achieved within a short period (0.44 g.xe213; 1 at 0.5 min and 0.75 gxe213; 1 at 1.0 min) by mPEI-TDA (1:2) at 293 K and 1 bar. The uptake results are superior to those of most DESs and ILs in the current literature. Furthermore, mPEI-TDA (1:2) had an excellent SO2/CO2 selectivity up to 89.1 at 293 K and 1 bar. Moreover, the SO2 absorption achieved using DESs is highly reversible since the absorption capacity did not decrease significantly even after 10 cycles (absorption at 293 K and 1 bar, desorption at 353 K and 0.1 kPa under vacuum for 2 h). Overall, this work indicates that designing a DES containing several tertiary amine sites with low viscosity can be an effective method for realizing fast and efficient desulfurization of flue gas.