CO2-selective transport in PEGDA facilitated transport membranes post-functionalized using click chemistry

Abstract

A new synthetic strategy to post-functionalize PEGDA membranes using active ester click chemistry was used to study the effects of Lewis base ligand grafting density and basicity on facilitated CO₂ transport and separation. Increasing imidazole ligand content from 0 mol% to 60 mol% causes both CO₂ and N₂ permeabilities to drop by 90+% due to a decrease in gas diffusivities. These diffusivities decrease due to increased chain stiffness from the substitution of flexible PEG groups with stiffer acrylamides. Increasing Lewis basicity of grafted ligands appears to hinder CO₂ diffusion due to stronger interactions between the base and CO₂ resulting in a 60 % decrease in permeability. This decrease in permeability is accompanied by apparent CO₂ chemisorption in piperazine (secondary amine) containing samples and a simultaneous decrease in CO₂ diffusion likely due to immobilization of some CO₂ as carbamate. These findings allow for better understanding of how nitrogenous Lewis base ligands impact CO₂ separations in low T_g copolymer membranes.