Glycidyl Ether-Functionalized Poly(ethylenimine)-Impregnated Sorbents for CO₂ Capture from Ultradilute Sources

Carbon dioxide adsorbents based on branched poly(ethylenimine) (PEI) are prevalent in postcombustion CO2 capture as well as direct air capture (DAC) of CO2. In DAC, PEI-based sorbents offer good tolerance to ranging environmental conditions (temperature, relative humidity, etc.) but require moderate temperature swings for CO2 desorption and oxidize over extended cycling in oxidative environments, such as ambient air. In this work, the functionalization of branched PEI with epoxides and glycidyl ethers of varying chain lengths is demonstrated, and the CO2 sorption characteristics of the resulting alumina-supported sorbents are elucidated. In parallel, the oxidative stability of the sorbents is probed using short, intense oxidative treatments, followed by measurement of the retained CO2 sorption capacities after oxidation. Functionalization of PEI in all cases leads to improved oxidative stability with a modest impact on CO2 uptake performance, with noteworthy performance when using long-chain glycidyl ethers or epoxides. Glycidyl ether-functionalized PEIs, which contain an additional ether linkage as compared to the epoxide-functionalized samples, allow for lower regeneration temperatures, offering promise for practical use compared to pristine PEI and epoxide-PEI sorbents.