Due to the rising levels of atmospheric CO2, the development of energy efficient methods to separate CO2 from power plant emissions has become increasingly important. Toward this goal, the use of passive membrane systems has emerged as a particularly intriguing method due to multiple advantages such as their inexpensive and easily processable nature. Recently, reports by our group and others have discovered that siloxane-substituted, addition-type polynorbornenes show tremendous promise for the separation of CO2 from N2, as well as the separation of light hydrocarbons. In an effort to elucidate the origins of their notable gas separation performance, we have conducted a detailed structure-activity relationship to better understand the interplay between their siloxane-based structure and their CO2/N2 permeation performance. These materials were synthesized using the catalyst trans-[Ni(C6F5)2(SbPh3)2] and were successfully solution-cast into thin-film, defect-free polymer membranes. We observed that by increasing the concentration of certain comonomers that the membranes overall CO2/N2 selectivity could be increased substantially while CO2 permeability only decreased by a very small amount. Our data will demonstrate that this drastic increase in CO2 selectivity arises due to solubility selectivity, which is abnormal for most glassy polymer films, and defies the traditional “permeability/selectivity tradeoff.”

Enhancing the selectivity of addition-type polynorbornenes for post-combustion carbon dioxide sequestration

255th National Meeting (2018)

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