CuII- and CoII-Based MOFs: {[La2Cu3(µ-H2O)(ODA)6(H2O)3]·3H2O}n and {[La2Co3(ODA)6(H2O)6]·12H2O}n. The Relevance of Physicochemical Properties on the Catalytic Aerobic Oxidation of Cyclohexene

Abstract

The aerobic oxidation of cyclohexene was done using the heterometallic metalorganic 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 bettercatalytic performance than that of LaCuODA (conversion 85% and 67%). The structures of bothcatalysts were very similar, showing channels running along the c axis. The physicochemical propertiesof both MOFs were determined to understand the catalytic performance. The Langmuir surface areaof LaCoODA was shown to be greater than that of LaCuODA, while the acid strength and acid siteswere greater for LaCuODA. On the other hand, the redox potential of the active sites was relatedto CoII/CoIII in LaCoODA and CuII/CuIin LaCuODA. Therefore, it is concluded that the Langmuirsurface area and the redox potentials were more important than the acid strength and acid sites of thestudied MOFs, in terms of the referred catalytic performance. Finally, the reaction conditions werealso 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.