Rationally designing mixed Cu–(μ-O)–M (M = Cu, Ag, Zn, Au) centers over zeolite materials with high catalytic activity towards methane activation

Abstract

The direct conversion of methane to methanol on [Cu(μ-O)M]²⁺ (M = Cu, Ag, Zn, Au) bimetal centers in ZSM-5 zeolite is investigated using periodic density functional theory for the first time. Some conclusions are drawn: (1) methane activation on [Cu(μ-O)M]²⁺ (M = Cu, Ag, Zn, Au) in the ZSM-5 zeolite proceeds through radical-like transition states, and the ability for CH₄ activation decreases in the sequence [Cu(μ-O)Ag]²⁺ > [Cu(μ-O)Au]²⁺ > [Cu(μ-O)Cu]²⁺ > [Cu(μ-O)Zn]²⁺. (2) There are two factors that can dramatically enhance C–H bond activation: a greater spin density and a less negative charge of the μ-O atom. (3) The angles ∠CuOM play a minor role in the reactivity difference among [CuOM]²⁺–ZSM-5 (M = Cu, Ag, Zn, Au). Our findings will provide insight into methane activation for designing highly effective catalysts applied in industrial processes.