Polyethyleneimine intercalated into alkyl layer for superhydrophobic interface: low-energy and O₂ & H₂O-resistant CO₂ sorbent

The major challenge that solid amine sorbents face in practical large-scale applications is their susceptibility to degradation under humid and oxygen-containing conditions. This study developed a superhydrophobic alkyl-silica by co-hydrolyzing alkyl-silane and tetraethyl orthosilicate and then immobilizing polyethyleneimine as a CO₂ sorbent. By adjusting the chain length and density, the surface of the alkyl-silica has abundant alkyl chains, and the PEI molecules are intercalated into the surface alkyl layer. These alkyl chains effectively block the contact of O₂ and H₂O with the amine group, thereby selectively allowing the adsorption/desorption of CO₂ molecules through the alkyl layer. The results showed that the working capacity of PEI/alkyl-silica was maintained at 90% by oxidation treatment and 84% by rinsing treatment, respectively, exhibiting excellent stability compared to unprotected PEI/SiO₂. Meanwhile, the alkyl chain due to the steric hindrance effect weakens the interaction between CO₂ and amine and does not reduce its original working capacity. The energy consumption of PEI/alkyl-silica during regeneration was lowered to 1.24 GJ per t-CO₂. This interfacial building concept provides a new path for designing a long-term stable amine sorbent for cost-effective CO₂ capture by avoiding the contact of O₂ and H₂O with the amine.