Constructing CO₂ Transport Pathways In Polyelectrolyte Membranes For Enhanced CO₂ Separation Performance

Highly efficient CO₂ capture technology is of great important to mitigate the greenhouse effect and to solve energy gas purification.Membrane technology as an eco-friendly and energy-saving separation process shows great prospects in CO₂capture.In particular,facilitated transport membranes often exhibit outstanding CO₂separation performance due to the reversible chemical interaction between carriers and CO₂ molecules.Regulating the spatial distribution of CO₂-philic groups in facilitated transport membranes is expected to be a promising strategy to achieve the fast CO₂ transport pathways to further enhance the separation performance.This study aimed at constructing fast CO₂ transport pathways in polymer-based membrane.By regulating the chemical structure of polymer and fillers,a series of novel polyelectrolyte membranes with different structure of ionic cluster were designed and fabricated.The details were summarized as follows:Construction of CO₂ transport pathways by ionic clusters and gas separation performance intensification:based on the microphase separation of polyelectrolyte,quaternary ammonium functionalized polysulfone membranes with ionic clusters were fabricated.The size of ionic clusters and their connectivity were regulated by tuning the quaternization degree,achieving the construction of CO₂ transport pathways in membranes.Concentrated distribution of quaternary ammonium groups afforded interconnected CO₂ facilitated transport pathway in polymer matrix,enhancing the solubility-reaction mechanism.Quaternary ammonium functionalized polysulfone membrane with 45%quaternization degree showed high CO₂permeability of 1109 Barrer with CO₂/CH₄ selectivity of 30,surpassing the 2008Robeson upper bound.Construction of CO₂ transport pathways by POSS-induced ionic clusters and gas separation performance intensification:quaternary ammonium functionalized polysulfone membranes with ionic clusters were designed and fabricated by template etching method.Ionic clusters were induced by the electrostatic interaction between–O^-groups in Octa-TMAPOSS and-N⁺（CH₂CH₃）₃ groups in polymer matrix to realize the construction of CO₂ transport pathways.CO₂ solubility was enhanced by hydrated ionic clusters in membranes,and the hollow structures formed by template etching substantially improved the CO₂ diffusivity.Meanwhile,B（OH）₄^-as the countra-ion efficiently facilitated CO₂ transport through reversible chemical interaction,realizing the synergistic intensification of solubility-diffusivity-reaction multi-mechanism in membranes.At the optimal content of template,membrane showed excellent CO₂permeability of 1206 Barrer with CO₂/CH₄ selectivity of 40,which surpass the 2008Robeson upper bound.Construction of CO₂ transport pathways by cyclodextrin-induced ionic cluster network and gas separation performance intensification:hybrid membranes were prepared by introducing sulfobutyl ether-β-cyclodextrin into quaternary ammonium functionalized polysulfon.By the electrostatic interaction between sulfobutyl groups and ionic clusters,the three-dimensional ionic cluster network was induced to construct the interconnected pathways in polymer matrix.Hydrated ionic clusters enhanced CO₂ solubility in membranes and provided the continuous transport sites.Meanwhile,the hollow cylinder structure of cyclodextrin effectively increased the stable free volume fraction.Mix matrix membrane with 0.5%fillers showed high CO₂permeability of 1307 Barrer with CO₂/CH₄ selectivity of 39,which surpass the 2008Robeson upper bound.