▎ 摘　　要

We herein report a facile preparation of graphene oxide (GO) membranes including three steps: (1) mild freeze-thaw exfoliation to get large GO nanosheets, (2) purification of exfoliated GO nanosheets through pH adjustment, and (3) spin coating to fabricate smooth GO membranes with uniformly aligned GO nanosheets. The fabricated GO membranes are subject to single gas permeation tests, with the obtained gas permeance in the order He > H-2 >> CH4 > CO2 > N-2 >> SF6, indicating a dominant molecular sieving separation mechanism. The H-2/CO2 mixed gas permeation tests reveal H-2 permeance up to 3.4 X 10(-7) mol/(m(2).s.Pa) and a H-2/CO2 separation factor up to 240, which are among the best of all the reported membranes for H-2/CO2 separation. The separation factor drops to 47 at a higher temperature of 120 degrees C, but the H-2 permeance is further increased to 6.7 X 10(-7) mol/(m(2).s.Pa), ensuring a higher gas separation throughput under higher temperatures. This study paves the way toward large-scale production and application of GO membranes as promising gas separation materials.