Labyrinthine transport of hydrocarbons through grafted laminar CdTe nanosheet membranes

Abstract

Here we report a concept for the construction of 2D membranes from crystalline flakes grafted with organic molecules, which assemble into a 2D structure with permeable double-layers between the flakes. Ultrathin selective layers (80–300 nm) of 1.2 nm thick CdTe nanoflakes grafted with a monolayer of oleic acid were deposited onto anodic alumina supports with different pore diameters (40–100 nm). The membranes possess a sorption type selectivity governed by the sorption of gas molecules on the oleic acid double-layers. The sorption capacity of the layers attained 13.5 mmol g⁻¹ (grafted) for butane, exceeding the sorption capacity of light hydrocarbons by an order of magnitude. The designed structures demonstrate ideal separation factors for a C₄H₁₀/CH₄ pair exceeding 40 and a mixed gas separation factor of 16 at butane permeance over 7.4 × 10⁻⁷ mol m⁻² Pa⁻¹ s⁻¹ (over 6 m³ (STP) m⁻² bar⁻¹ h⁻¹). Labyrinthine transport of hydrocarbons through the layers was confirmed using microstructural investigations and comparison of the transport characteristics with straight-channel membranes.