Insertion of Ionic Liquid into Silica Nanopores for Increased Catalytic Performance

The confinement of ionic liquids in nanoporous materials has been of recent interest for use as tunable microenvironments for catalysis. Ionic liquids 1-(3-trimethoxysilylpropyl)-3-methylimidazolium chloride) and (1-(3-trimethoxysilylpropyl)-3-methylimidazolium chloride) were loaded into orthogonally oriented hexagonally close packed cylindrical silica pores via soaking and tethering methods respectively. In the first method, porous silica films were soaked in a 10 wt.% ionic liquid solution then vacuum dried. Tethering was performed by submerging the silica film in an ionic liquid and chloroform solution and refluxing at 60 â—¦C for 26 hours. FTIR was performed on soaked films that underwent a second step of soaking in deionized water. Through FTIR we showed that the ionic liquid is not easily washed from the silica surface in an aqueous environment. Electrical impedance spectroscopy showed a large increase in the resistance of silica films loaded with ionic liquid via soaking in comparison to silica films without ionic liquid. Films loaded with ionic liquid through tethering showed a much lower increase in resistance. This lower electrical resistance achieved through tethering may indicate better transport through the silica pores due to special structuring of the ionic liquid. This may be useful in applications using these films as micro-environments for catalysis.