(185n) Ultrathin Membranes Based on Single-Layer Graphene and Laminar Graphene Oxide for Molecular Separation

As the thinnest membrane, single-layer graphene is highly promising to achieve ultrafast molecular transport. One of the bottlenecks in realizing the potential of atom-thick single-layer graphene membrane for molecular-sieving is the difficulty in incorporating nanopores in graphene lattice, with a narrow pore-size-distribution at a high-enough pore-density. This is especially challenging for gas-sieving which requires an Å precision in the lattice-etching. We achieved this by developing a synergistic, partially-decoupled defect-nucleation and pore-expansion strategy. An O₂ plasma or room-temperature O₃ treatment based defect-nucleation and the subsequent high-temperature O₃ treatment based pore-expansion increased the density of H₂-sieving pores to ca. 2.1 x 10¹² cm^-2 while limiting the percentage of CH₄ permeating pores to 13-22 ppm. As a result, a record-high gas-mixture separation performance was achieved (H₂ permeance: 1340 - 6045 GPU; H₂/CH₄ separation factor: 15.6 – 25.1; H₂/C₃H₈ separation factor: 38.0-57.8).This pore-etching strategy is reproducible and scalable and will accelerate the development of single-layer-graphene-based energy-efficient membranes.

Compared with single-layer graphene, laminar membranes assembled from graphene oxide (GO) provide a more practical approach for separation application. However, for subnanometer-scale separations in aqueous environment, the implementation of excellent comprehensive performance in terms of flux, separation factor and stability remains a critical challenge. We achieved this by synergistically tuning the physical and chemical interlayer structures of GO membrane using a multifunctional structure-modulator, leading to the construction of robust water-selective transport highways. As a result, a superior water flux of 5936 g/m²âˆ™h, a remarkably high water/butanol separation factor of 3966 and an attractive long-term stability are achieved from an ultrathin (~30 nm) GO membrane, which exceeds the performance of state-of-the-art membranes for water/butanol separation. The synergistically tuning strategy proposed here is facile and reproducible, holding the great potential to produce high-efficiency GO and other 2D-material membranes for precise molecular separations in aqueous environment.