An anomalous anion transfer order in graphene oxide membranes induced by anion-π interactions.

Selective transport of anions across membranes has become an important goal in chemistry and biology. Here, we found an anomalous anion transfer order within the graphene oxide membrane: Cl - > Br - > F - > I - . This is at odds with the conventional ranking of the transfer order, which usually decreases as the radii of the anions increase, i.e. , F - > Cl - > Br - > I - . The abnormal transportation of F - can be ascribed to the strong anion-π interactions between F - and graphene oxide sheets. Such unexpectedly strong anion-π interaction resulted in the lower movement of F - in the graphene oxide membrane and caused the anomalous anion transfer order. Our findings not only provide experimental evidence of anion-π interactions, but also improve our understanding of anion-π interactions in the selective transport of anions across a two-dimensional membrane.