Kyoto, Japan — In a recent study published in Nature Communications in April, then Cambridge University group leader and current Kyoto University Institute for Integrated Cell-Material Sciences (iCeMS) visiting associate professor, Dr. Easan Sivaniah, reported a method for modifying small porous membrane materials to achieve highly efficient gas separation. This method could be important for carrying out energy and environmental processes, such as gas purification, on an industrial scale.

Conventional polymer membranes are relatively dense forming a significant barrier for gases to pass through them. Although this allows the membrane the opportunity to separate gases such as carbon dioxide and nitrogen through differential chemical interactions with the polymer, it requires a significant amount of energy or pumping pressure to push the gas through the membrane. The Sivaniah group has been working with PIMs (polymers of intrinsic microporosity) that, through poor chain packing, have large effective pore sizes (~1.5nm) allowing gases to pass through these membranes easily but with an inefficient separation of different gases. In other words, the same open structures of PIMs that increase energy efficiency reduce selection efficiency. To get around this issue, Sivaniah used ultraviolet light to activate reactive ozone (three molecules of oxygen) near the surface of the material, which in turn broke down the structure of the PIM. As a result, the PIM’s surface becomes tightly packed into thin membranous sheets with strong selectivity whilst the overall membrane retains its high permeability. As a result the combined gas separation properties (good permeablity and selectivity) rose dramatically.

The researchers are hoping that this technique can be advantageous over existing processes that use large amounts of energy for gas separation such as distillation. Moreover, the method may be expanded to other applications like surface coating. Sivaniah is planning to continue his research at Kyoto University iCeMS as an associate professor from July.

by Peter Gee, public relations URA (university research adnimistrator)

Publication Information
Photo-oxidative enhancement of polymeric molecular sieve membranes