Heterostructured graphene oxide membranes with tunable water-capture coatings for highly selective water permeation

Graphene oxide (GO) laminar membranes with fast water-transport nanochannels hold great promise for water-selective molecular separations, but the water-capture ability of membrane surfaces limits the separation performance. Herein, we engineered water-capture coatings on GO laminar membranes using structurally tunable tannic acid (TA) nanoaggregates as building blocks via a bottom-up method, acquiring heterostructured GO membranes for alcohol dehydration. The abundant oxygenated functional groups of TA coatings captured water from alcohol aqueous solutions and enhanced the surface water-capture capacity by up to 309%. We manipulated the surface water-capture ability by regulating the aggregation structure and the subsequent assembly process of the TA nanoaggregates. By virtue of the synergistic effect of the enhanced surface water-capture ability and fast water-transport GO nanochannels, the optimized heterostructured GO membrane exhibited high permeation flux of 9988 g m−2 h−1 and a superior separation factor of 4424 for n-butanol dehydration. This study provides a novel avenue to high-performance GO membranes with rationally designed heterostructures.