“Tai Chi” philosophy driven dual-network ionogel membrane comprised of ionic guests in a multifunctional host for propylene/propane separation

Abstract

Facilitated transport ionogel membranes have shown great prospects in propylene/propane separation due to the stability of carrier media, no leakage, and promising thermal/physical properties. In the present study, inspired by the Tai Chi philosophy of adjusting inorganic and organic features, a dual-network ionogel was made of multi-functional organosilane, [EMIM][TFSI] ionic liquid, AgBF4, and catalysts. An effective strategy, including solvent-free solvolytic sol-gel and epoxide ring-opening reaction, was proposed to keep the inorganic/organic balance and obtain ionogel films with high IL loading (up to 82%) and self-standing. The ionogels were characterized by a phase diagram, formation mechanism, FTIR, N2 adsorption-desorption isotherms, TGA, SEM, mechanical properties, and transport properties. The Multifunctional host induced the breaking of bondage between the components of IL electrolyte (AgBF4 and IL); thereby more free Ag+ ions become available for facilitating the olefin transport. A computational molecular approach was applied to better understand the possible interactions between the ionic guest and multifunctional host. Results indicate that the optimized ionogel not only has excellent transport properties (C3H6 permeability of 243.1 Barrer and C3H6/C3H8 selectivity of 20.2) but also has desirable mechanical and thermal properties. The synthesis of ionogel based on Tai Chi philosophy opens a new window for facilitated transport of gas separation membranes.