resumo
A Co/Al layered double hydroxide material was synthesized in both bulk and exfoliated (colloidal) forms. Anion exchange with methionine allowed immobilization of Au nanoparticles previously prepared by a biomimetic method using an anti-oxidant tea aqueous extract to reduce the Au salt solution. The catalytic performance of bulk and exfoliated clays Au-hybrid materials was assessed in aerobic olefin epoxidation. Both catalysts were very active towards the epoxide products and with very interesting substrate conversion levels after 80 h reaction time. The Au-exfoliated material, where the nanosheets work as large ligands, yielded higher product stereoselectivity in the case of limonene epoxidation. This arises from a confined environment around the Au nanoparticles wrapped by the clay nanosheets modulating access to the catalytic active centres by reagents. Mechanistic assessment was also accomplished for styrene oxidation by DFT methods.
palavras-chave
SUPPORTED GOLD NANOPARTICLES; SELECTIVE OXIDATION; NANOCLUSTERS; REDUCTION; NANOCATALYST; ALCOHOLS; INSIGHT; OXIDE
categoria
Chemistry; Environmental Sciences & Ecology
autores
Leandro, SR; Fernandes, CI; Viana, AS; Mourato, AC; Vaz, PD; Nunes, CD
nossos autores
Pedro Miguel Duarte Vaz
Colaboradoragradecimentos
The authors would like to acknowledge Fundacao para a Ciencia e a Tecnologia (FCT), Portugal for financial support (project UID/MULTI/00612/2013). CIF (SFRH/BD/81029/2011) and AM (SFRH/BPD/35036/2007) also acknowledge FCT for financial support. G09 calculations were made possible due to the computing resources provided by STFC Scientific Computing Department's SCARF cluster. We also thank the reviewers for raising pertinent questions that contributed largely to improve this manuscript.