Periodic mesoporous organosilica containing ionic bis-aryl-imidazolium entities: Heterogeneous precursors for silica-hybrid-supported NHC complexes

Abstract

The synthesis of periodic mesoporous organosilica incorporating ionic diarylimidazolium species was achieved by hydrolysis-polycondensation of a bis-silylated diarylimidazolium (Si-IMes-) precursor in the presence of non-ionic triblock copolymer as structure directing agents. Although hydrolysis polycondensation of the pure precursor gave materials with moderate porosity, highly porous solids were obtained by the addition of tetraethoxysilane (TEOS) to the sol solution. The architecture of the materials on a mesoscopic scale strongly depends on the TEOS/Si-IMes ratio in the sol. Materials with highly regular hexagonal symmetry were obtained using high molar excess of TEOS. The obtained PMO type materials incorporating diarylimidazolium substructures are promising heterogeneous precursors for the formation of silica hybrid supported N-heterocyclic carbene complexes and therefore have great potential in heterogeneous catalysis. © The Royal Society of Chemistry.