Catalysts (May 2020)
Cu<sup>II</sup>- and Co<sup>II</sup>-Based MOFs: {[La<sub>2</sub>Cu<sub>3</sub>(µ-H<sub>2</sub>O)(ODA)<sub>6</sub>(H<sub>2</sub>O)<sub>3</sub>]∙3H<sub>2</sub>O}<sub>n</sub> and {[La<sub>2</sub>Co<sub>3</sub>(ODA)<sub>6</sub>(H<sub>2</sub>O)<sub>6</sub>]∙12H<sub>2</sub>O}<sub>n</sub>. The Relevance of Physicochemical Properties on the Catalytic Aerobic Oxidation of Cyclohexene
Abstract
The aerobic oxidation of cyclohexene was done using the heterometallic metal organic frameworks (MOFs) {[La2Cu3(μ-H2O)(ODA)6(H2O)3]⋅3H2O}n (LaCuODA)) (1) and {[La2Co3(ODA)6(H2O)6]∙12H2O}n (LaCoODA) (2) as catalysts, in solvent free conditions (ODA, oxydiacetic acid). After 24 h of reaction, the catalytic system showed that LaCoODA had a better catalytic performance than that of LaCuODA (conversion 85% and 67%). The structures of both catalysts were very similar, showing channels running along the c axis. The physicochemical properties of both MOFs were determined to understand the catalytic performance. The Langmuir surface area of LaCoODA was shown to be greater than that of LaCuODA, while the acid strength and acid sites were greater for LaCuODA. On the other hand, the redox potential of the active sites was related to CoII/CoIII in LaCoODA and CuII/CuI in LaCuODA. Therefore, it is concluded that the Langmuir surface area and the redox potentials were more important than the acid strength and acid sites of the studied MOFs, in terms of the referred catalytic performance. Finally, the reaction conditions were also shown to play an important role in the catalytic performance of the studied systems. Especially, the type of oxidant and the way to supply it to the reaction medium influenced the catalytic results.
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