Capsules with polyurea shells and ionic liquid cores for CO₂ capture

Abstract

Many ionic liquids (ILs) have good solubilities of CO 2 but the high viscosity of ILs makes them cumbersome and kinetically limits gas uptake. Encapsulation of ILs is an effective approach to overcoming these limitations. In capsules with a core of IL, the chemical composition of the shell impacts performance.Here, we report the preparation of capsules with a core of the IL [Bmim][PF 6 ] and polymer composite shell, then evaluate how the identity of the polymer impacts CO 2 uptake. IL-in-oil Pickering emulsions stabilized by nanosheets are used, with capsules formed by interfacial polymerization between different diamines and diisocyanates (e.g., shells are polyurea and nanosheets). The capsules contain 60-80 wt% IL and the composition was verified using Fourier transform infrared spectroscopy. Optical microscopy, scanning electron microscopy, and particle sizing data showed spherical, discrete capsules with 50-125 μm in diameter. All capsules are stable up to 250 C. Brunauer-Emmett-Teller analysis of CO 2 gas uptake data showed that different polymer compositions led to different CO 2 uptake properties, with capacity ranging from 0.065 to 0.025 moles of CO 2 /kg sorbent at 760 torr and 20 C. This work demonstrates that the polymer identity of the shell impacts gas uptake properties and supports that shell composition can tailor performance.

First Measurements of the Sorption of Difluoromethane and Pentafluoroethane in Encapsulated Ionic Liquids

“…ILs ([C 4 C 1 im]­[PF 6 ], [C 6 C 1 im]­[Cl], and [C 2 C 1 im]­[Tf 2 N]) were encapsulated by interfacial polymerization in a IL-in-oil or IL-in-water Pickering emulsion template via a previously reported procedure. , For the IL-in-oil system, 1 mL of IL ([C 4 C 1 im]­[PF 6 ] or [C 6 C 1 im]­[Cl]) was added to a 20 mL vial, followed by 1.3 mmol of ethylenediamine, and 5 mL of C 18 -GO stock solution. This mixture was emulsified using a handheld emulsifier (model number 985 370 from BioSpec Products, Inc.) for three consecutive cycles of 20 s of emulsification followed by a 5 s pause.…”

“…The resulting C 18 -GO was isolated via centrifugation, washed thrice with octane (4500 rpm, 15 min), and dispersed in 50 mL of octane to a concentration of 2 mg/mL. 61,62 For the IL-in-oil system, 1 mL of IL ([C 4 C 1 im][PF 6 ] or [C 6 C 1 im][Cl]) was added to a 20 mL vial, followed by 1.3 mmol of ethylenediamine, and 5 mL of C 18 -GO stock solution. This mixture was emulsified using a handheld emulsifier (model number 985 370 from BioSpec Products, Inc.) for three consecutive cycles of 20 s of emulsification followed by a 5 s pause.…”

Pickering Emulsions as Templates for Architecting Composite Structures

“…44 A single-step encapsulation of IL can be realized by interfacial step growth polymerization in an emulsion, provided orthogonal solubility of two monomers. 45 For example, a GOstabilized emulsion can be prepared with ethylenediamine in the continuous water phase and hexamethylene diisocyanate in droplets of an IL, such that interfacial polymerization yields capsules with a core of the IL and composite shell of nanosheets and polyurea. 46 This approach was used to encapsulate the generic IL [BMIM][BF 4 ] and give capsules with applications in CO 2 uptake and separations.…”

Wettability-tuned silica particles for emulsion-templated microcapsules

“…Per a previously reported procedure, 11 approximately 20 mg of the [BMIM][PF 6 ] microcapsules were added to a vial containing a 0.039 M solution of mesitylene (internal standard) in acetone-d 6 .…”

“…7 Most commonly, encapsulation may be accomplished via hard-template approach, wherein a polymer shell is grown around a sacrificial core (e.g., layer-by-layer assembly atop a silica particle), 8 or via soft-template approach, which utilizes a stable biphasic system (e.g., interfacial polymerization in emulsions). 9 Both cases enable the handling of fluids as solid powders, which facilitates their use in specialized applications like direct air capture of CO 2 , 10,11 contaminant removal, 9,12 and targeted drug delivery. 13,14 The emulsion-based approach for encapsulation has garnered increased attention over the past several decades.…”