KSEF RDE: Interfacially Controlled Incorporation of Transition Metal Oxides within Ordered Mesoporous Ceramics

We propose a new, rational method for the synthesis of ordered mesoporous ceramics (OMCs) incorporating isolated transition metal oxide (TMO) sites. Supported TMOs have numerous applications in catalysis,photocatalysis, sensors, and photovoltaics. However, traditional deposition methods such as incipient wetness or coprecipitation create ill-definedTMO clusters that may block the pores of the support, have only a small fraction of active centers, lose activity due to poor binding to the support, and leach out over time. Incorporating isolated, covalendy bound TMO sites will improve all aspects of the accessibilityand stability of the materials. We propose a rational, fundamentally based approach to preparing TMO-incorporated OMCs by using mixed surfactants to simultaneously template an ordered mesoporous structure and to covalendy attach TMO sites. The first step is to choose the surfactants. One surfactant is chosen that forms well-ordered phases with the support (e.g. silica)and a second is chosen with reactive ligands (e,g, amines, glycosides,or bipyridine) that localize the TMO precursor during co-assembly. The second step is to measure the phase diagram of the mixed surfactant system in water, with or without transition metals. In the third step, conditions giving a specific lyotropic liquid crystalline phase are used to prepare a TMOOMC material with the same nanoscale structure by a one-pot "nanocasting" procedure. Preliminary experiments show that the ternary phase diagram of mixed surfactants (e.g. glycoside and cationic) in water can be used to predict the pore structure of OMCs produced by nanocasting. Once materials are formed, catalytic and photovoltaic testing will be demonstrate the impact of TMO site isolation on activity. This simple, one-pot method provides control not only of pore size, shape and orientation through mesophases tuning, but also of the density, placement, and oxidation state of the TMO guest through choice of the complexing surfactant concentration and type. Keywords: nanotechnology, energy, materials synthesis, colloid science, catalysis