Chemistry in confined space: a strategy for selective oxidation of hydrocarbons with high catalytic efficiencies and conversion yields under ambient conditions

Abstract

Selective catalytic oxidation of hydrocarbons is challenging. Here, we show how this chemistry could be accomplished for cyclohexane (C₆H₁₂) at room temperature with good turnover numbers, excellent catalytic efficiencies, high conversion yields and product selectivity, when the catalysis is mediated by a tricopper cluster complex immobilized in the nanochannels of mesoporous silica nanoparticles. The Cu^ICu^ICu^I tricopper cluster is activated by dioxygen (O₂) to mediate the hydrocarbon oxidation to cyclohexanol (C₆H₁₂O) and cyclohexanone (C₆H₁₀O) by a direct O-atom transfer mechanism and the turnover of the catalyst is driven by hydrogen peroxide (H₂O₂). The desired product is obtained by simply varying the experimental conditions. In the case of limiting H₂O₂, the catalytic efficiency can reach 96%. When H₂O₂ is in large excess, the conversion of C₆H₁₂ and selectivity to C₆H₁₀O can reach close to 100%. The nano-confined catalytic system leads to higher solubility of O₂ and thus to higher activity. The heterogeneous catalyst is robust and reusable after many cycles.