期刊
MOLECULES
卷 25, 期 23, 页码 -出版社
MDPI
DOI: 10.3390/molecules25235756
关键词
gold nanoclusters; gold atoms; cyclohexene; oxidation; XPS; SBA-15; functionalization; aminopropyl; rosemary oil; allylic oxidation
资金
- Spanish Ministerio de Ciencia e Innovacion [MAT2016-77496-R]
- Consejo Superior de Investigaciones Cientificas [2019AEP076]
- Ministerio de Ciencia e Innovacion through the Ramon y Cajal program [RYC2018-024561-I]
- Gobierno de Aragon [DGA E13_20R]
- National Natural Science Foundation of China [NFSC-21850410448, NSFC-21835002]
- Centre for High-resolution Electron Microscopy (ChEM) - SPST of ShanghaiTech University [EM02161943]
Gold nanoclusters and isolated gold atoms have been produced in a two-liquid phase procedure that involves a solution of gold in aqua regia and rosemary essential oil as organic layer. These gold entities have been immobilized on the ordered mesoporous silica material SBA-15 functionalized with different amounts of aminopropyl groups. The resulting materials have been characterized by XRD, N-2 adsorption, chemical analysis, TGA, Si-29 MAS NMR, C-13 CP/MAS NMR, UV-vis spectroscopy, XPS, and STEM. The Au-containing materials retain the ordering and porosity of the pristine support. Gold content varies in the range of 0.07-0.7 wt% as a function of the specific immobilization conditions, while STEM evidences the presence of isolated gold atoms. XPS shows a shift of the Au 4f BE toward values lower than those of metallic gold. The catalytic activity in the oxidation of cyclohexene with molecular oxygen at atmospheric pressure parallels the Au content of the aminopropyl-SBA-15 supports. This activity is higher than that of analogous Au entities immobilized on SBA-15 functionalized with thiol or sulfonate groups, the activity decreasing in the order Au-NH2 > Au-SO3- > Au-SH. This behavior has been attributed to differences in the interaction strength between the functional group and the Au entities, which is optimum for the aminopropyl groups.
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