Imidazolium-Based Copoly(Ionic Liquid) Membranes for CO₂/N₂ Separation

Abstract

The development of efficient carbon dioxide capture and separation technologies is at the fore front of the priorities in the climate change policies. Poly(ionic liquid)s (PILs) have been emerging as extremely promising materials for the fabrication of membranes for CO 2 separation. This work is a step forward to evaluate the performance of PIL-based copolymers in the preparation of membranes for CO 2 /N 2 separation. In particular, imidazolium-based homo and copolymers were synthesized by RAFT co-polymerization of different imidazolium salts and characterized by nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) analysis. The membrane forming ability of the synthesized PILs, as well as the influence of different side chain groups (ethyl, pentyl, benzyl and napthyl) at imidazolium ring, were evaluated using the solvent casting technique. In order to improve membrane forming ability and CO 2 separation performance, different amounts of free ionic liquid (IL), [C 2 mim][NTf 2 ], were added into the synthesized homo and copolymers, and PIL-IL composite membranes were prepared. The CO 2 and N 2 permeation properties of the obtained free standing PIL-IL membranes were measured at 20 º C and 100 kPa and the results obtained compared through the Robeson plot.

Top-Down Polyelectrolytes for Membrane-Based Post-Combustion CO2 Capture

“…Polyelectrolytes have started gaining broad attention of the membrane community since the first publications emerged in the end of the last century. Later the unprecedented success of the ionic liquids (IL) have shifted the interest towards the monomer polymerisation approach with polymerisable ionic liquids (PILs) coming to the front line of the research on CO 2 capture from flue gas (Figure 2a) [33][34][35][36][37]. This interest arose following the reports of high CO 2 sorption capacities of IL and desire to improve long-term stability performance of IL membranes through combining the polymer chain flexibility and robustness with the physico-chemical potential of IL.…”

MOF‐Directed Synthesis of Crystalline Ionic Liquids with Enhanced Proton Conduction

“…[19d] Although, when temperature is increased from À40 to 80 8 8C, the conductivity of IL 1 sharply increases by 5orders of magnitude.At808 8C, the conductivity of IL 1 MOF is 1.89 10 À2 Scm À1 ,w hich is still 2o rders of magnitude higher than that of IL 1 .M eanwhile,f rom À40 to 80 8 8C, IL 1 MOF also has 1-2 orders of magnitude higher conductivity than IL 2 .U ntil now,t he surveyed solid IL derivatives were all reported with lower conductivities than their counterpart bulk ILs at room temperature (Figure 2d and Table S6), and this phenomenon becomes more pronounced when increasing temperature. [5,6,11,15] Interestingly, the conductivity of IL 1 MOF is unexpectedly higher than these of IL 1 and IL 2 in the whole measured temperature range (Figure 2a and b). Meanwhile, IL 1 MOF also exhibits the highest conductivities from 30 to 80 8 8Cw hen compared to other MOF-based anhydrous proton conductors (see Table S7 and Figure S14).…”

“…d) Survey of reported bulk ILs (balls), their derivatives and this work (* *IL 1 ,N NIL 1 MOF, * *IL 2 ,~IL 2 @MOF)around room temperature. Derivatives with same parent IL are shown as the same color and aligned at the same horizontalc oordinate (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). The ordinate axis is the lgs (ILs derivative) /s ILs for clarity.D ashed line along the bulk ILs (balls) indicates aconductivity limitation of normal IL derivatives (see Table S6 and Ref.…”

“…Ionic liquids (ILs) are atype of liquid salt that melts near or below room temperature.T hey have been widely used as safe and promising electrolytes in supercapacitors,secondary batteries,f ull cells and dye-sensitized solar cells etc. [4] Compared to the classic ILs,t he developed solid IL derivatives,i ncluding the liquid crystals of semi-rigid poly(ionic liquid)s [5] and the ILs@support systems with ILs confined within nano pore/region of supports (carbon nanotubes,silica, ceramic,(bio)polymer etc.) [6] (Scheme 1), possess significantly enhanced mechanical properties required for practical applications and relative ordered structures in short-range.…”

“…[6] (Scheme 1), possess significantly enhanced mechanical properties required for practical applications and relative ordered structures in short-range. However,t hey suffer from significantly lower conductivity than their counterpart bulk ILs [5][6][7] due to the reduced ion content in the ILs@support systems and absent long-range ordered structure even in liquid-crystal ILs (i.e.Random ILs, Scheme 1). Although solid IL derivatives are proposed as as uperior choice for optimizing the manufacture,s afety and cost of the various electrical devices,t heir conductivities generally cannot meet the practical needs ( % 10 À3 Scm À1 )o f applications at room temperature or lower.…”