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Silica Supported Molecular Palladium Catalyst for Selective Hydrodeoxygenation of Aromatic Compounds under Mild Conditions

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journal contribution
posted on 05.09.2019, 18:34 by Nicholas A. DeLucia, Amy Jystad, Katherine Vander Laan, John Meynard M. Tengco, Marco Caricato, Aaron K. Vannucci
The molecular complex chloro­(2,2′:6′,2″-terpyridine-4′-carboxylic acid)­palladium­(II) chloride was synthesized and was attached to the surface of amorphous silicon dioxide to generate a molecular/heterogeneous catalyst motif. This catalytic system exhibited excellent selectivity (>99%) for hydrodeoxygenation of oxygenated aromatics under mild reaction conditions. A kinetic analysis showed that this molecular/heterogeneous catalyst was an order of magnitude more active than analogous homogeneous catalysts. Characterization techniques such as XRD and solid-state NMR, in conjunction with ICP-MS, indicate that the molecular catalyst is present on the surface of SiO2 and the formation of unwanted metallic Pd nanoparticles can be avoided. Computational modeling shows the catalysts can adhere to the oxide surface through a hydrogen bonding interaction, via a Coulombic attraction between the charged molecule and the oxide surface, or through covalent bonding. Postreaction analysis of the surface-modified oxide catalysts confirmed prolonged molecular integrity of the catalyst and sustained binding of the catalyst to the oxide surface when nonpolar solvents were employed for reactions. These surface-attached molecular catalysts thus were recycled through multiple catalytic reactions.