Dual-bonded Polyethyleneimine Network with Electron-withdrawing Groups at α, β-sites for Ultra-stable and Low-energy CO₂ Capture in Harsh Environments

As an innovative approach to addressing climate change, significant efforts have been dedicated to the development of amine sorbents for CO₂ capture. However, the high energy requirements and limited lifespan of these sorbents, such as oxidative and water stability, pose significant challenges to their widespread commercial adoption. Moreover, the understanding of the relationship between adsorption energy and adsorption sites is not known. In this work, a dual-bond strategy was used to create novel secondary amine structures by a polyethyleneimine (PEI) network with electron-extracted (EE) amine sites at adjacent sites, thereby weakening the CO₂ binding energy while maintaining the binding ability. In-situ FT-IR and DFT demonstrated the oxygen-containing functional groups adjacent to the amino group withdraw electrons from the N atom, thereby reducing the CO₂ adsorption capacity of the secondary amine, resulting in lower regeneration energy consumption of 1.39 GJ·t-1-CO₂. In addition, the EE sorbents demonstrated remarkable performance with retention of over 90% of their working capacity after 100 cycles, even under harsh conditions containing 10% O₂ and 20% H₂O. DFT calculations were employed to clarify for the first time the mechanism that the oxygen functional group at the α-site hinders the formation of the urea structure, thereby being an antioxidant. These findings highlight the promising potential of such sorbents for deployment in various CO₂ emission scenarios, irrespective of environmental conditions.