Ionic Liquid Mixtures for Direct Air Capture: High CO2 Permeation Driven by Superior CO2 Absorption with Lower Absolute Enthalpy.

This paper reports a series of liquid materials suitable for use as high-performance separation membranes in direct air capture. Upon mixing two ionic liquids (ILs), namely N-(2-aminoethyl)ethanolamine-based IL ([AEEA][X]) and 1-ethyl-3-methylimidazolium acetate ([emim][AcO]), the resulting mixtures with a specific range of their composition showed higher CO2 absorption rates, larger CO2 solubilities, and lower absolute enthalpies of CO2 absorption compared to those of single ILs. NMR spectroscopy of the IL mixture after exposure to 13CO2 allowed elucidation of the chemisorbed species, wherein [AEEA][X] reacts with CO2 to form CO2-[AEEA]+ complexes stabilized by hydrogen bonding with acetate anions. Supported IL membranes composed of [AEEA][X]/[emim][AcO] mixtures were then fabricated, and the membrane with a suitable mixing ratio showed a CO2 permeability of 25,983 Barrer and a CO2/N2 selectivity of 10,059 at 313.2 K and an applied CO2 partial pressure of 40 Pa without water vapor. These values are higher than those reported for known facilitated transport membranes.

Inkjet-printed lines with well-defined morphologies and low electrical resistance on repellent pore-structured polyimide films.

Polyimide films are the most promising substrates for use in printed electronics because of their high thermal stability. However, the high wettability of polyimide films by conductive inks often produces thin inkjet-printed lines with splashed and wavy boundaries, resulting in high electrical resistance of the lines. To overcome these disadvantages, we fabricated repellent pore structures composed of polyamideimide with high thermal stability on a polyimide film. Using this film, the inkjet-printed line thickness was increased without penetration of silver nanoparticles into the pore structures, thus resulting in very sharp edges without any splashing. This was because the repellent treatment restricted the spreading of the silver nanoparticles into the pore structures and the pore structures prevented ink splashing upon impact on the film. As a result, the electrical resistance of these lines decreased to one-fifth that of the lines on the pristine polyimide film. The inkjet printing of conductive inks onto repellent pore structures would contribute to the future of printed electronics because this technique enables printing closely packed line patterns while maintaining high conductivity within a limited space.