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

• Published in: Journal of the American Chemical Society 2004-09, Vol.126 (35), p.10864-10866
• Main Authors: Fujdala, Kyle L, Drake, Ian J, Bell, Alexis T, Tilley, T. Don
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts: preparations and properties; Chemistry; Exact sciences and technology; General and physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja048701+

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, ∼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.