Gas separation mechanism of CO2 selective amidoxime-poly(1-trimethylsilyl-1-propyne) membranes

Abstract

Polymeric membranes for CO₂ separation have drawn significant attention in academia and industry. We prepared amidoxime-functionalized poly(1-trimethylsilyl-1-propyne) (AO-PTMSP) membranes through hydrosilylation and post-polymerization modification. Compared to neat PTMSP membranes, the AO-PTMSP membranes showed significant enhancements in CO₂/N₂ gas separation performance (CO₂ permeability ∼6000 Barrer; CO₂/N₂ selectivity ∼17). This systematic study provides clear guidelines on how to tune the CO₂-philicity within PTMSP matrices and the effects on gas selectivity. Key parameters for elucidating the gas transport mechanism were discussed based on CO₂ sorption measurements and fractional free volume estimates. The effect of the AO content on CO₂/N₂ selectivity was further examined by means of density functional theory calculations. Both experimental and theoretical data provide consistent results that conclusively show that CO₂/N₂ separation performance is enhanced by increased CO₂–polymer interactions.