Materials with Hierarchical Porosity Enhance the Stability of Infused Ionic Liquid Films

Abstract

Defined surface functionalities can control the properties of a material. The layer-by-layer method is an experimentally simple yet very versatile method to coat a surface with nanoscale precision. The method is widely used to either control the chemical properties of the surface via the introduction of functional moieties bound to the polymer or create nanoscale surface topographies if one polymeric species is replaced by a colloidal dispersion. Such roughness can enhance the stability of a liquid film on top of the surface by capillary adhesion. Here, we investigate whether a similar effect allows an increased retention of liquid films within a porous surface and thus potentially increases the stability of ionic liquid films infused within a porous matrix in the supported ionic liquid-phase catalysis. The complex geometry of the porous material, long diffusion pathways, and small sizes of necks connecting individual pores all contribute to difficulties to reliably coat the required porous materials. We optimize the coating process to ensure uniform surface functionalization via two steps. Diffusion limitations are overcome by force-wetting the pores, which transports the functional species convectively into the materials. Electrostatic repulsion, which can limit pore accessibility, is mitigated by the addition of electrolytes to screen charges. We introduce nanoscale topography in microscale porous SiC monoliths to enhance the retention of an ionic liquid film. We use γ-Al 2 O 3 to coat monoliths and test the retention of 1-butyl-2,3-dimethylimidazolium chloride under exposure to a continuous gas stream, a setup commonly used in the water-gas shift reaction. Our study showcases that a hierarchical topography can improve the stability of impregnated ionic liquid films, with a potential advantage of improved supported ionic liquid-phase catalysis.

From Sticky to Slippery: Self-Functionalizing Lubricants for In Situ Fabrication of Liquid-Infused Surfaces

“…As lubricants, beside silicone oil, we chose hexadecane, olive oil, and a phosphonium-based ionic liquid, tributylmethyl­phosphosphonium bis­(trifluoro­methylsulfonyl)­imide [TBMP]­[NTf 2 ], as representative examples of conventional hydrocarbon oils, natural oils, and ionic liquids (Figure ). The latter can be important for the design of repellent surfaces with long-term stability at elevated temperatures, and in the context of supported ionic liquid catalysis (SILP). − The structural formula of olive oil, which is composed of multiple fatty acids, is simplified to oleic acid in Figure . As reactive species, we chose available molecules with a chemical structure matching that of the lubricant, but containing amino, thiol, or acid chloride groups.…”

Nature-inspired functional porous materials for low-concentration biomarker detection

“…For this specific application, the main goal is to obtain IOs with the most regular morphology achievable, and with a neck size that allows sufficient flow of substances for subsequential functionalization steps, taking into consideration the challenge of diffusion in IOs. 54 Note that as no photonic effect is exploited, the pore size is not limited to dimensions that would interact with light to form structural color, which is a common design criteria for IOs. 10,55 IOs with 350 nm pores showed the lowest number of cracks, the highest pore connectivity, and the highest surface-to-volume ratio at a fixed number of layers to enable comparison.…”

Preparation and Surface Functionalization of a Tunable Porous System Featuring Stacked Spheres in Cylindrical Pores

“…The sacrificial polystyrene (PS) spheres used in this study were prepared following the protocol reported in the literature. [ 28,29 ]…”

“…The sacrificial polystyrene (PS) spheres used in this study were prepared following the protocol reported in the literature. [28,29] Anodization of aluminum into ordered pores: The generation of the tunable ordered porous system follows the standard two-step anodization procedure described in the literature. [30] A homemade setup was used to anodize four circular aluminum plates of 2.2 cm diameter, held by Orings underneath a polyvinyl chloride beaker.…”