Surface engineering of polymer membrane for air separation

Gas separation has been an important process in chemical industries. Polymer membranes have been widely developed for gas separation due to the main advantages such as light weight, low cost, and easy preparation procedure. However, a trade-off between permeability and selectivity of the polymer membrane becomes a significant hurdle for its application in gas separation. Moreover, in the case of air separation where the oxygen and nitrogen molecules have a very close diameter, a high selectivity is more difficult to be achieved. Therefore, numerous researches were directed to improve the performance of the polymer membrane. Surface modification is an attractive way to enhance the selectivity while maintaining the high permeability of the base membrane. This paper provides a review of surface modification of polymer membrane which aims to enhance the air separation performance. The discussion includes surface engineering strategies of polymer membrane and their performances in air separation. In the end, the conclusions and future directions are pointed out.