Enhancing CO₂ Uptake of Molecular Basket Sorbents with Polymer Modifiers for H₂ Purification

The development of cost-effective, high-performance sorbents for CO2 capture in hydrogen purification remains a critical challenge, particularly under industrial conditions of ultralow CO2 concentrations and ambient temperatures. This study systematically investigates polyethylenimine (PEI)-impregnated SiO2 and SBA-15 sorbents, with a focus on enhancing CO2 uptake and kinetics through polyethylene glycol (PEG) incorporation. Although PEI-SBA-15 sorbents showed higher static and dynamic CO2 uptakes compared to PEI-SiO2 sorbents, its diffusion barrier lowers the adsorption rate in the flow system. The poly(ethylene glycol) (PEG) polymers were introduced to PEI-SiO2 to improve the mass transfer of CO2 in PEI clusters. The low PEI loading was found to be beneficial to CO2 adsorption on SiO2, resulting in superior CO2 uptakes and a lower diffusion barrier than PEI-SBA-15 sorbents. The characterization was conducted to uncover physical and chemical properties. The breakthrough experiments of PEI-30-SiO2 with PEG derivates confirmed that the O in the skeleton of PEG played an important role in the interaction between PEI and PEG rather than terminal OH groups. This work also demonstrated the CO2 desorption and stability of PEG-modified PEI-SiO2 sorbents in H2.