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The dissertation describes research work on development of bimetallic heterogeneous catalysts for oxidation of organic compounds. Binuclear metal complexes are an interesting class of compounds due to their catalytic activity. The approach involves anchoring a triketone ligand to Cab-O-Sil via a linker. Specifically, silica gel was allowed to react with p-chloromethylphenyltrimethoxysilane followed by coupling with deprotonated triketone compounds. The viability of this approach was verified by performing the benzylation reaction of triketones with benzyl halides under basic conditions. The benzylation of 2,4,6-heptanetrione and 1,5-diphenyl-1,3,5-pentanetrione is achieved with benzyl bromide using n-tetrabutylammonium fluoride as base. These benzylation reaction conditions were used to attach the triketones to the surface-attached linker. Once the ligand is attached to the silica gel, the catalyst is formed by coordinating two copper(II) ions from solution to the deprotonated triketone. The coordination of copper(II) ions to the triketone was monitored using UV-vis spectroscopy. The modified silica gel is characterized by diffuse reflectance infrared Fourier spectroscopy (DRIFTS), and thermal gravimetric analysis (TGA) at the different stages of catalyst formation. All techniques indicated significant attachment of linker and triketone to the support. The oxidation of 3,5-di-tert-butyl catechol (DTBC) and benzyl alcohol was carried out under aerobic conditions using these catalysts. The kinetics of the DTBC oxidation and benzyl alcohol oxidation was studied using bimetallic and monometallic catalytic systems. The copper complexes of the triketone ligands were also evaluated as catalysts for the oxidation of DTBC. New bimetallic metal complexes with triketone ligands having a benzyl group were synthesized and characterized by high resolution mass spectroscopy and IR spectroscopy. In addition to a detailed description of the synthesis and characterization of new triketone compounds, and the heterogeneous catalyst systems, a comparison of the kinetics of the oxidation of DTBC using these catalysts will be discussed.

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Monometallic and bimetallic model catalysts on either refractory metal singlecrystals as planar surfaces or oxide supports as nano-size clusters have been systematically studied using X-ray photoemission spectroscopy (XPS), low energy ion scattering spectroscopy (LEIS), low energy electron diffraction (LEED), infrared reflection absorption spectroscopy (IRAS), and temperature programmed desorption (TPD) under ultra-high vacuum (UHV) conditions. Of particular interest in this investigation is the characterization of the surface composition, morphology, and electronic/geometric structure of the following catalysts: Au/TiOx, Au-Pd/Mo(110), Au- Pd/SiO2, Cu-Pd/Mo(110), and Sn/Pd(100). Structure-reactivity correlations during surface-alloy formation and adsorption-desorption processes were explained in terms of ensemble and ligand effects. Prospects of translating the accumulated atomic-level information into more efficient 'real world' catalysts were discussed.

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Yes / Bimetallic nanoparticles are of immense scientific and technological interest given the synergistic properties observed when two different metallic species are mixed at the nanoscale. This is particularly prevalent in catalysis, where bimetallic nanoparticles often exhibit improved catalytic activity and durability over their monometallic counterparts. Yet despite intense research efforts, little is understood regarding how to optimize bimetallic surface composition and structure synthetically using rational design principles. Recently, it has been demonstrated that peptide-enabled routes for nanoparticle synthesis result in materials with sequence-dependent catalytic properties, providing an opportunity for rational design through sequence manipulation. In this study, bimetallic PdAu nanoparticles are synthesized with a small set of peptides containing known Pd and Au binding motifs. The resulting nanoparticles were extensively characterized using high-resolution scanning transmission electron microscopy, X-ray absorption spectroscopy, and high-energy X-ray diffraction coupled to atomic pair distribution function analysis. Structural information obtained from synchrotron radiation methods was then used to generate model nanoparticle configurations using reverse Monte Carlo simulations, which illustrate sequence dependence in both surface structure and surface composition. Replica exchange with solute tempering molecular dynamics simulations were also used to predict the modes of peptide binding on monometallic surfaces, indicating that different sequences bind to the metal interfaces via different mechanisms. As a testbed reaction, electrocatalytic methanol oxidation experiments were performed, wherein differences in catalytic activity are clearly observed in materials with identical bimetallic composition. Taken together, this study indicates that peptides could be used to arrive at bimetallic surfaces with enhanced catalytic properties, which could be leveraged for rational bimetallic nanoparticle design using peptide-enabled approaches. / Air Force Office for Scientific Research (T.R.W., Grant No. FA9550-12-620 1-0226). S.P.E. and E.B.C. gratefully acknowledge financial support from the Army Research Office through a MURI award, W911NF-10-1-0520

With the dwindling availability of petroleum, focus has shifted to renewable energy sources such as lignocellulosic biomass. Cellulose and hemicellulose are highly utilized components of biomass, and on the other hand, lignin is a plentiful, under-utilized component of the lignocellulosic biomass. Hence, utilization of the lignin component is necessary for the realization of an economically sustainable biorefinery model. Once depolymerized, lignin has the potential to replace petroleum-derived molecules. Further, a catalyst is capable of selectively removing the oxygen atoms without hydrogenating the aromatic components would be valuable. Bimetallic phosphides and zeolites are capable of selectively cleaving CAROMATIC–O bonds from aromatic compounds. In the present study, the applications of a bimetallic phosphides (FeMoP, RuMoP and NiMoP) for CAROMATIC–O bond cleavage and hydrogenation of C=O and C=C bond in the aromatic model compounds (Phenol, furfural, cinnamaldehyde, and CO2) were examined. The Fe:Mo ratio was varied in FeX Mo2−X P catalysts (0.88 to 1.55) to investigate the effect of catalyst acidity and hydrogenolysis capability via first principle calculations. The most acidic material was most selective for phenol to benzene. Further, combination of different transition metals with phosphorus were tested for hydrogenolysis and hydrogenation mechanism of phenol. Additionally, composition effect in RuXMo2−XP (X = 0.8, 1.0 and 1.2) have investigated for furfural and cinnamaldehyde hydrogenation. It was found that tuning in metal combination and composition results in control of binding energy and activation energy barrier which tune the selectivity for desire reaction and reaction pathway. Alternatively, highly active MWW-zeolite nanosheets have recently been explored for depolymerization in lignin. First, binding strength of different lignin dimers (phenolic and non-phenolic) was studied in terms of binding energy and binding mode over different terminated zeolite surface as a function of temperature and solvent. The optimized binding structure of lignin dimers were further considered to study the hydrogenolysis pathways over Al- and Sn-substituted MWW zeolite nanosheets. Generally, it was found that fully hydroxyl terminated surface, phenolic dimers and higher temperature in methanol pro- motes higher binding energy. Moreover, Al-substituted zeolite nanosheet resulted in lowering activation energy barriers significantly to cleave β-O-4 Linkages in Lignin dimers.