Immobilization induced molecular compression of ionic liquid in ordered mesoporous matrix

Abstract

In this work, ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide ([EMIM] [FSI]) has been immobilized into ordered mesoporous silica MCM-41 by a physical imbibition process. Transmission electron microscopy confirms the filling of mesopores of MCM-41. The effect of IL content in MCM-41 was probed in terms of thermal stability, chemical interactions, and dielectric properties. N 2 -sorption results indicate the compression of the IL in the nanopores of MCM-41, which contributes to an increase of the melting point probed by differential scanning calorimetry. The quantum chemical calculations confirmed that the ion-ion interaction in ion-pairs of IL were preferred over the hydrogen bonding interaction in the presence of SiO 2 molecules, and these interactions probably compress the molecular size in the nanopores of Strong interactions between IL and porous MCM-41 were suggested as the mechanism of this immobilization, which was characterized by FTIR and dielectric spectroscopy.

Dynamics of Ionic Liquids in Confinement by Means of NMR Relaxometry—EMIM-FSI in a Silica Matrix as an Example

“…The confined system was prepared following the vacuum-assisted physical imbibition process described in detail in [ 30 , 31 ]. The nitrogen-sorption measurement was performed for the determination of the pore parameters and this sample showed a type IV isotherm, characteristic of mesoporous nature [ 31 ]. The confined system was prepared following the procedure described in [ 30 , 31 ].…”

“…The nitrogen-sorption measurement was performed for the determination of the pore parameters and this sample showed a type IV isotherm, characteristic of mesoporous nature [ 31 ]. The confined system was prepared following the procedure described in [ 30 , 31 ]. MCM-41 has a mesoporous structure with cylindrical pores and the measured average pore diameter in it is of about 3.5 nm.…”

Ionic liquids under nanoscale confinement

“…In the specific case of the ILs (and also other liquids, as reported for cyclohexane in Ref [66]), the surface energy difference can change sign, and the freezing temperature can be higher, leading to solidification of the IL inside the pores at room temperature. The increase of the melting temperature was inferred by force measurements on ILs squeezed between either insulating and metallic surfaces [31,67] or spontaneously intercalated between mica sheets upon drop-casting deposition [68]; direct differential scanning calorimetry measurements revealed this effect for ILs inside multiwalled carbon nanotubes [29] and into ordered mesoporous silica [69].…”

Development of mesoporous polysaccharide/sol-gel composites with two different templating agents: Surfactants and choline chloride-based deep eutectic solvents

“…This would expectedly increase considerably the capacity of the sorbents and eventually also the binding strength. In addition, mesoporosity is of high importance in other specific areas such as in optics, catalysis, drug delivery systems, coatings, cosmetics, bio-separation, diagnostics, gas-separation and nanotechnology [7]. Initially, we attempted the most common approach of mesoporous templating in sol-gel processes which makes use of surfactants, such as primary amines and quaternary ammonium ions [8][9][10][11][12][13][14].…”