Traditionally, catalysts have been formed by synthesis of small metal domains within mesoporous materials. We are demonstrating that pre-synthesized nanocrystals, with controlled properties, may be infused into ordered mesoporous materials by tuning the interactions of the nanocrystals with the pore walls. The decoupling of the nanocrystal synthesis step and the infusion step, leads to exquisite control of the nanocrystal size, morphology, properties and dispersibility within the pores. These composite materials are being investigated in a variety of applications in catalysis and optoelectronics. Novel supported catalysts are being produced to improve turnover numbers and selectivities for various chemical reactions.

Iridium nanoparticles stabilized with tetraoctylammonium bromide ligands have been infused within mesoporous silica using supercritical CO₂. The objective was to identify a ligand with sufficiently weak binding to the nanoparticle surface, such that it becomes unnecessary to pre-treat the catalyst at high temperature to remove the ligand. The nanoparticles are highly dispersed as observed by TEM and show high catalytic activity for 1-decene hydrogenation. Supercritical CO₂ enhances the van der Waals attraction between silica surface and nanoparticle, enhancing their adsorption on the surface and hence driving higher loadings. Iridium loadings of 1.3 wt% within mesoporous silica have been obtained. The supported catalyst does not require any pre-treatment for activation as the ligands bind weakly to the iridium surface and are readily desorbed from the nanoparticle surface during synthesis step. The catalyst did not show any enhancement of the activity when pre-treated under high temperatures or when annealed in supercritical CO₂ and was twice as active as commercial Pd-Al2O3 catalysts. The catalysts are stable even after the reaction and are robust after high temperature treatment. The exquisite control over the size and morphology of the nanoparticles within the support achieved with the decoupling of the synthesis step and the infusion step, allows the catalyst to be potentially used in shape selective catalysis.