Super-low energy consuming CO2 capture triggered by weak hydrogen bonds in solid-liquid phase separation

A novel nonaqueous solid-liquid biphasic solvent, diethylenetriamine (DETA)/dimethyl sulfoxide (DMSO), with considerable CO2 absorption capacity and extremely low regeneration heat, was proposed. After absorbing CO2, the precipitate exhibited a CO2 loading of 0.0070 mol g−1, which accounted for 96.9% of the captured CO2. Benefiting from the greatly reduced reaction heat, sensible heat, and latent heat, the estimated regeneration energy using DETA/DMSO biphasic solvent was reduced to 0.74 GJ t−1 CO2. The corresponding regeneration cost was 44.4 CNY·t−1 CO2, only 19.5% of 5 M MEA, and much lower than the reported biphasic solvents. Moreover, the DETA/DMSO absorbent had good absorption/desorption stability and large desorption efficiency (about 92%). In addition, the substances distribution and CO2 absorption mechanisms of DETA/DMSO were revealed. DETA-carbamate and protonated DETA were recognized as the major CO2 absorption products, while a small amount of carbamic acid rearranging from zwitterion could also exist stably in DMSO diluent. Because of the huge polarity difference of these species in CO2-loaded absorbent, high polarity DETA-CO2 products aggregated together due to weak hydrogen bonds and precipitated from the liquid phase. Overall, the DETA/DMSO biphasic solvent was proved to be a potential candidate for conventional MEA in sustainable CO2 capture.