1, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
3, University of California, Riverside, Riverside, California, United States
Most of the world’s energy is presently derived from the burning of fossil fuels, which releases vast quantities of carbon dioxide (CO2) into the environment and results in undesirable climate change. Practical and cost-efficient methods of CO2 separation and capture would thus solve one of the most challenging problems today. This presentation summarizes our efforts on the development of novel polymer membranes functionalized with CO2-philic groups for high flux CO2 separation. Our strategy focuses on tuning solubility selectivity in addition to diffusivity selectivity for achieving high permeability membranes combined with good selectivity. Various synthetic techniques including ROMP, thiol-ene click reaction, and post functionalization were used and the careful design permits to prepare well-defined novel high permeable polymers containing CO2-philic groups. This study demonstrated the addition of CO2-philic groups (e.g. amidoxime and PEO) significantly increased the solubility selectivity of CO2 over N2. The membrane performance is also highly dependent on the balance of gas/functional group interaction, intra/inter- molecular interaction (H-bonding etc.) of membrane, packing, and polymer dynamics (degree of crosslinking). Tuning the balance of the interaction and dynamics enables to achieve the CO2 separation performance over the Robeson upper bound, e.g. CO2 permeability 6800 Barrer and CO2/N2 selectivity 19, or CO2 permeability 820 Barrer and CO2/N2 selectivity 39. The structure-property relationships especially on CO2 uptake, CO2 and N2 permeability, CO2/N2 selectivity to the polymer structure, as well as the effort on the selective layer coating will be discussed. Moreover, the other gas pair separation such as CO2/CH4, He/CH4 and He/N2 via tailoring solubility selectivity and diffusivity selectivity will also be discussed. Our membranes are rubbery-based and thus have no ageing issues, in contrast to glassy membranes.