Self-Assembled Facilitated Transport Membranes with Tunable Carrier Distribution for Ethylene/Ethane Separation

Facilitated transport membranes (FTMs) are a forward-looking technology and have triggered revolutions in many energy-intensive gas separations. However, the precise manipulation of carrier distribution within FTMs, as well as the visualization of membrane structure at the nanoscale, has never been reported. Herein, FTMs are constructed with tunable carrier distribution by a facile ion/molecule self-assembly of protic ionic liquid crystal salts (PILSs), polyol, and ethylene-transport carrier for highly efficient sub-angstrom scale ethylene/ethane (0.416nm/0.443nm) separation. The elaborate regulation of non-covalent interactions by optimizing the ion/molecule compositions within membrane confers the bi-continuous nanostructure of FTMs, resulting in the formation of successive carrier wires and enormous 3D interconnected ethylene transport pathways, which is verified and visualized by molecular dynamics simulations and synchronous small- and wide-angle X-ray scattering (SWAXS). The as-designed FTMs manifest simultaneously super-high selectivity, excellent ethylene permeance, and robust long-term stability, which exceeds previously reported ethylene/ethane separation membranes. This study clearly draws the first picture of carrier distribution within FTMs, and deep insight into membrane structure will shed light on the design of high-performance separation membranes for energy-intensive gas separations.