ABSTRACT
Colloidal deposition of gold nanoparticles (Au NPs) onto NH2-UiO-66 nanocrystals has been demonstrated with the resulting hybrid catalyst proving robust and versatile for one-pot, heterogeneous conversions involving the selective oxidation of primary alcohols in tandem with Knoevenagel condensation reactions. Within these systems, structure-property correlations have been established to confirm that the active sites for the oxidation and condensation reactions are intrinsically correlated with the Au NPs and pendant amine groups respectively.
ABSTRACT
Highly active and selective aerobic oxidation of KA-oil to cyclohexanone (precursor for adipic acid and É-caprolactam) has been achieved in high yields using continuous-flow chemistry by utilizing uncapped noble-metal (Au, Pt & Pd) nanoparticle catalysts. These are prepared using a one-step in situ methodology, within three-dimensional porous molecular architectures, to afford robust heterogeneous catalysts. Detailed spectroscopic characterization of the nature of the active sites at the molecular level, coupled with aberration-corrected scanning transmission electron microscopy, reveals that the synthetic methodology and associated activation procedures play a vital role in regulating the morphology, shape and size of the metal nanoparticles. These active centers have a profound influence on the activation of molecular oxygen for selective catalytic oxidations.
Subject(s)
Metal Nanoparticles/chemistry , Oils/chemistry , Platinum/chemistry , Aerobiosis , Cyclohexanes/chemistry , Oxidation-ReductionABSTRACT
By using platinum nanoparticle catalysts that are generated in situ by extrusion from a porous copper chlorophosphate framework, the role of oxidants in the selective oxidation of benzyl alcohol to benzaldehyde was evaluated, with a view to establishing structure-property relationships. With a detailed study of the kinetic properties of the oxidation reaction, it has been determined that the aerobic oxidation pathways progress with lower levels of product selectivity and higher activation energies (72.4â kJ mol-1 ) than the peroxide-based ones (23.6â kJ mol-1 ); affording valuable insights in the design of solid catalysts for selective oxidation reactions. Furthermore, through the use of X-ray absorption spectroscopy, the effect of calcination temperature on the degree of extrusion and its influence on nanoparticle formation have been evaluated, leading to the establishment of structure-activity correlations between the observed activation energies and the proportion of nanoparticle species generated.
ABSTRACT
The frontispiece shows a novel inâ situ method of generating metal nanoparticles within porous molecular frameworks, thereby affording highly active and selective single-site heterogeneous catalysts for industrially significant aerobic oxidations. The Communication on pageâ 1226 by Robert Raja and Andy Hor etâ al. highlights the importance of spectroscopic and kinetic studies in establishing structureproperty correlations that are fundamental in the design of sustainable heterogeneous catalysts.
ABSTRACT
A novel method for the in situ generation of catalytically active small metal nanoparticles, by anion extrusion on a parent porous copper chloropyrophosphate framework, has been developed to generate gold, platinum and palladium nanoparticles for sustainable catalytic oxidations using molecular oxygen as the oxidant. Transmission electron microscopy coupled with detailed structural and physico-chemical characterisation, in combination with in-depth kinetic analysis have afforded profound insights into the nature of the active site for facilitating structure-property correlations.
