▎ 摘　　要

Graphene oxide (GO)-based membranes have attracted extensive attention in water purification but still face great challenge due to their poor service life. To overcome this issue, weakly oxidized graphene nanosheets have been chemically exfoliated from natural graphite via a newly-developed strategy for preparing layer-tunable graphene. When an 80 mu m-thick graphene membrane is assembled from the graphene nanosheets with an average layer number of 3, it exhibits a high rejection rate of 99.9 % for Rhodamine B and a water flux of up to 3452.6 L m- 2 h-1 bar-1. This should be ascribed to the unique hierarchically nanochannel structure within the membrane. This finding may provide a new insight into the design and fabrication of the thick membrane having excellent sieving performance. Furthermore, the rejection rate of RB can be maintained at 99.9 % even after 24 cycles of filtrations, demonstrating a superior service performance for the membrane.