Tuning Morphology and Activity of Three-Dimensionally Ordered Mesoporous Oxide Catalysts By Templated Solvothermal Synthesis

Realization of efficient and highly-selective liquid-phase catalytic conversion of bulky organic molecules (e.g., biorefinery, environmental remediation) demands the development of next-generation catalysts with ordered and tunable meso- or hierarchical-porosity in order to simultaneously meet demands on stability in the face of possible high-temperature aqueous phase processing and reduction of mass transport limitations. In this talk, we will discuss a hierarchical templating strategy enabling realization of high-surface area, large-pore volume metal oxide materials (e.g., TiO₂, ZrO₂) with three-dimensionally ordered mesoporosity.  The approach relies on the facile synthesis and template-free assembly of monodisperse, size-tunable (ca. ≥ 10 nm) silica nanoparticles into 3D-ordered colloidal crystals, and their replication via solvothermal nucleation and crystal growth of the desired metal oxide within the 3D-interconnected template pore topology.  We will demonstrate how this solvothermal processing results in sub-micron, spherical 3DOm titania materials. 

In an effort to establish critical synthesis-structure-function relations for these materials, we will discuss a comprehensive study that elucidates the role that the template and the solvent (e.g., primary, secondary, tertiary alcohols) employed during material synthesis play in modulating particle size, crystal nucleation and growth, pore volume, and the dominant crystal faceting of the synthetic 3DOm metal oxides.  Studies comparing the intrinsic kinetics associated with the synthetic 3DOm titania materials for biomass derivative conversion (e.g., glucose-to-fructose isomerization as well as fructose dehydration to HMF) and photocatalytic decomposition of ‘bulky’ surrogate molecules (e.g., methylene blue) help establish structure-function relations enabling tunability and optimization of catalytic activity with judicious choice of the solvent employed during the materials synthesis process.