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Atomic Level Control over Surface Species via a Molecular Precursor Approach: Isolated Cu(I) Sites and Cu Nanoparticles Supported on Mesoporous Silica

2004; American Chemical Society; Volume: 126; Issue: 35 Linguagem: Inglês

10.1021/ja048701+

1943-2984

Kyle L. Fujdala, Ian J. Drake, Alexis T. Bell, T. Don Tilley,

Electrocatalysts for Energy Conversion

A nonaqueous molecular precursor grafting approach was employed for the generation of well-defined surface structures featuring Cu on a mesoporous silica support. X-ray absorption measurements (XANES and EXAFS) were used to determine that [CuOSi(OtBu)3]4 provided 100% isolated Cu(I) sites upon grafting (without thermal treatment), whereas [CuOtBu]4 gave isolated species with most of the original Cu-O-Cu linkages intact, but in a more relaxed straight chain form. Upon heating under inert conditions, the vast majority of Cu in the materials from [CuOSi(OtBu)3]4 remained as isolated Cu(I) sites (up to 88% isolation), with significant stabilization provided from the -OSi(OtBu)3 ligands. In stark contrast, approximately 100% of the Cu in the materials generated from [CuOtBu]4 was readily reduced upon heating, forming isolated Cu metal particles with an average diameter of 0.7 nm.