Highly Selective and Tunable CO₂/N₂ Separation Performance in Ammonium-Based Organic Ionic Plastic Crystal Composite Membranes with Self-Healing Properties

Abstract

An advancement in light gas separation performance is realized by using organic ionic plastic crystal (OIPC)-based composites. In this work, a composite membrane is synthesized from tetraethylammonium bis­(fluoro­sulfonyl)­imide ([N2222]­[FSI]) and poly­(vinylidene fluoride-co-hexafluoro­propylene) (PVDF-HFP) for the first time and tested under different thermal conditions to investigate the performance in different solid phases. The composite demonstrates tunable performance within a small range of temperatures and enhanced CO2 solubility upon annealing, reaching a CO2 permeability of ∼130 barrer with a remarkable CO2/N2 selectivity of α ≈ 70 at 55 °C. The thermophysical properties of the composite reveal a strong dependency between the structure and the overall gas separation performance. Higher homogeneity in the [N2222]­[FSI]:PVDF-HFP mixture is concluded to hinder OIPC crystallinity and enhance interfacial disorder, boosting CO2 solubility and ionic conductivity and concomitantly providing good mechanical support. Additionally, self-healing behavior is observed in the composite, which makes it more attractive for practical applications. These results provide valuable insights into the advanced design of more selective and durable OIPC-based composite membranes for light gas separation.

Thermal, structural and dynamic properties of ionic liquids and organic ionic plastic crystals with a small ether-functionalised cation

“…Diverse thermal, physical and transport properties were observed for each material, with a notable dependence on the nature of the anion as well as strong influence from the ether-functionality. These systems expand the library of potential solid-state and liquid electrolytes, not only for alkali metal battery applications but also in applications such as CO 2 capture, 112 gas separation, 113,114 solid-state supercapacitors 115 and as potential binders in electrode materials. 116,117…”

Vacuum-Assisted Self-Healing Amphiphilic Copolymer Membranes for Gas Separation

“…Among the currently available self-healing chemistry, − hydrogen bonds-based self-healing is one of the popular alternatives and has been widely applied due to its distinct chemical structures . Despite their potential, there have been limited reports on the use of self-healing polymers based on hydrogen-bonding interaction in membrane gas separation. − Most of the membrane healing mechanisms require the involvement of external stimuli (i.e., heat, light, pressure, solvent, etc.) and occur under atmospheric conditions, meaning the gas separation processes are excluded.…”

“…This is caused by the poor intrinsic self-healing ability of the membranes at room temperature and further suffering from unaccustomed or extreme environments during gas separation tests. In addition, some of the healable membrane production failed to achieve the desired gas separation performances. ,− …”

Simulation studies on the dynamic heterogeneity of organic ionic plastic crystals

“…Thanks to the diversity, OIPCs have been used for various purposes such as lithium and sodium batteries, [6][7][8][9][10] dyesensitized solar cells, 11,12 fuel cells, 13,14 or gas separation membranes. 15,16 However, it is hard to understand how OIPCs can show high ionic conductivity in (extremely viscous) solid states. Therefore, it has been an issue of interest to understand the transport mechanism of ions in OIPCs.…”

“…For example, novel OIPCs have been reported and investigated recently, for example, dication‐based 3,4 and camphorsulfonate‐based 5 OIPCs. Thanks to the diversity, OIPCs have been used for various purposes such as lithium and sodium batteries, 6–10 dye‐sensitized solar cells, 11,12 fuel cells, 13,14 or gas separation membranes 15,16 . However, it is hard to understand how OIPCs can show high ionic conductivity in (extremely viscous) solid states.…”