Solvent-Swing CO₂ Capture with Aralkylamines

The separation of neutralized acid/base into acid and base (retro-neutralization) requires external energy. Basic amines actively react with acidic CO₂ to form amine/CO₂ via neutralization. In contrast, CO₂ separation from amine/CO₂ requires external energy in the form of heat, pressure, light, or electricity. A common bottleneck of CO₂ capture is the large separation energy at the CO₂ release/concentration process. Here, it is shown that CO₂ selectively absorbed to aralkylamines is released when a solvent is added to the amines at room temperature without external energy input. CO₂ release is achieved by adding a highly volatile, low-boiling-point, inexpensive solvent rather than by applying external energy, as done in the past. Moreover, various solvents can be applied, and there is no correlation between the boiling point of the solvent and CO₂ release performance. This finding shows that amine/CO₂ solubility in solvents can cause retro-neutralization, which generates basic unreactive amines and spontaneously releases acidic CO₂. This research has the potential to serve as the basis for the next generation of CO₂ capture technology and to make a significant contribution to CO₂ reduction. These results show that retro-neutralization reactions previously considered to be energy intensive can be performed to yield acids and bases due to the solubility.