Au encapsulated into Al-MCM-41 mesoporous material: in situ synthesis and electronic structure

Abstract

Au supporting mesoporous material Al-MCM-41 composites were successfully prepared by encapsulation of the in situ synthesized gold nanoparticles into Al-MCM-41; herein palygorskite clay was used as the Si and Al sources and cetyltrimethylammonium bromide (CTAB) as the template and coupling agent. The obtained Al-MCM-41 possessed a well-defined two-dimensional hexagonal structure with a relative large specific surface area and pore size distribution of 3.9 nm, which was ideal to house very small Au nanoparticles (∼3 nm). Using this in situ encapsulation route, the highly ordered Al-MCM-41 was simultaneously generated with the gold nanoparticles incorporated into the pores and the Au³⁺ species well dispersed in the frameworks. The electronic structure and optical properties of Au/Al-MCM-41 were investigated in detail. The partial reduction of Au³⁺ species by incorporation of Al³⁺ from clay sources was confirmed by XPS results and DFT calculations, and the higher catalytic activities of Au/Al-MCM-41 over Au-MCM-41 were evaluated.