Exploring the application of porous and ionic liquids for sustainable chemistry

Abstract

Porous liquids are a new class of materials, which have predominantly been investigated for their capacity to adsorb gases. However, these materials are expected to possess unusual combinations of characteristics, typically associated either with porous solids or with liquids, leading to, as yet, unexplored applications. This thesis explored the encapsulation of catalysts within porous liquids and their resulting catalytic activities. The encapsulation of metal nanoparticles within a Type I porous liquid was explored first. This involved the encapsulation of the nanoparticles within the hollow silica spheres before functionalisation with a corona-canopy to form the porous liquid. The methodology developed was successfully employed for the encapsulation of gold, platinum and palladium nanoparticles. The catalytic activity of the platinum nanoparticles encapsulated within the porous liquid was then investigated as a hydrogenation catalyst under mild conditions. The effect of each component of the porous liquid was explored in order to advance the understanding of the fundamental catalytic properties of porous liquids. Further exploring these systems, the immobilisation of a homogeneous catalyst within the cavities of the porous liquid was investigated. A palladium-based complex was covalently tethered to the silica spheres before functionalisation with the corona-canopy, immobilising this homogeneous catalyst within the porous liquid. This porous liquid system was successfully employed as a catalyst for Heck reactions. The final aspect of this thesis was to explore greener alternatives to the current methodologies for the synthesis of N,N,N-trimethyl chitosan, which has gained much interest for its prospective industrial and pharmaceutical applications. Conventional methods for the methylation of chitosan involve the use of highly toxic reagents. A method was developed for the single-step methylation using dimethyl carbonate, a green methylating agent.