Copper-Containing Polyoxometalate-Based Metal-Organic Frameworks as Highly Efficient Heterogeneous Catalysts toward Selective Oxidation of Alkylbenzenes

With a one-pot assembly method, two copper-containing Keggin-type polyoxometalate-based metal-organic frameworks (POMOFs), i.e., [Cu-6(I)(trz)(6){PW12O40}(2)] (HENU-2, HENU = Henan University; trz = 1,2,4- triazole) and [Cu-3(I)(trz)(3){PMo12O40}] (HENU-3), were successfully prepared and structurally characterized. These two compounds, which are generated by the extension of a crown-like {Cu-6(trz)(6)} macrocycle-based sandwich-type structural unit, possess identical noninterpenetration 3D frameworks except for the polyanions difference. Additionally, both of them are assessed as highly effective heterogeneous catalysts in facilitating the oxidation of alkylbenzenes to ketone products in the presence of tert-butyl hydroperoxide. Under optimized conditions, HENU-2 can achieve a 95.2% conversion of diphenylmethane in 20 h with a 100% selectivity toward benzophenone, and it was reused for three runs with constant high activity, which outperforms most POM-based catalysts for this catalytic reaction.