A loosely stacked lamellar membrane of irregular MoS2 flakes for ultrahigh water and organics permeation

Abstract

Two-dimensional (2D) lamellar membranes with fast molecular transfer and precise sieving hold great promise for a wide range of separation applications. However, existing transfer channels are horizontally arrayed with long and tortuous in-plane paths, leading to high flow resistance and hence limited molecular permeance. Herein, we report a loosely stacked lamellar membrane with fastigiated channels using rigid and irregular molybdenum disulfide (MoS₂) flakes as building blocks. Through filtration, MoS₂ flakes stack in a disordered manner and construct hierarchical transfer channels: narrow gaps (∼1.8 nm) at the contacting edges of flakes and large cavities (∼8.3 nm) among stacked flakes. The large cavities work as low-barrier channels and result in ultrafast molecular permeation: over 1430 and 5000 L m⁻² h⁻¹ bar⁻¹ for water and organics, respectively. However, the narrow gaps afford excellent dye rejection: over 90% for dyes with a size of above 1.9 nm. Dynamic simulation demonstrates that the flow resistance of fastigiated channels is much lower than that of horizontal channels. Furthermore, the corresponding model equation is established for describing molecular transfer in such channels. In addition, the membrane exhibits adequate structural stability under ultrasonication and acid or alkali environments, guaranteeing potential for long-term operation.