Construction of a hierarchical carbon nanotube/MXene membrane with distinct fusiform channels for efficient molecular separation

Two-dimensional (2D) lamellar membranes have shown great potential in efficient molecular separations. However, the development of membranes with both high permeability and selectivity using traditional single-spacing channels is still challenging. In this study, a high-performance heterostructured membrane with fusiform transport channels using carbon nanotubes as spacing tailors among MXene layers is explored, where the combination of narrow gate for blocking the guest molecules and wide slit-like pathway for fast permeation are constructed. Based on the synergistic effects of hierarchical transport channels, a high rejection for molecules larger than 1 nm and ultrahigh water permeation (1270 L m(-2) h(-1) bar(-1), which is about 3.4 times that of a pure MXene membrane) are achieved. Furthermore, molecular dynamics simulations reveal that water molecules transport with an ordered alignment within the confined channels, facilitating the fast diffusion and transport of aggregates. This facile and scalable approach of constructing hierarchical channels in 2D membranes can demonstrate the potential for accelerating transport and separation processes.