Efficient Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran over Fe2O3-Promoted MnO2 Catalyst

It is challenging to effectively convert 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF), a flexible biobased building-block, over non-noble metal catalysts. In this contribution, Mn–Fe oxides were prepared and served as highly active catalysts for the selective oxidation of HMF to DFF. Among Mn–Fe oxides with varied Mn–Fe molar ratios, Mn6Fe1Ox showed the best catalytic activity and offered HMF conversion up to 97% with a DFF selectivity of 98% (110 °C, 5 h, and 1.5 MPa O2). It is revealed that the introduction of α-Fe2O3 resulted in significant enhancement in the amount of catalytic active sites (Mn4+–O2– pairs) and their activity in Mn6Fe1Ox for the dehydrogenation of HMF to DFF. Mn6Fe1Ox also was a robust catalyst that could be successively used at least six times without substantial loss in its catalytic activity. Furthermore, a facile two-step process for the conversion of fructose to DFF with a yield up to 80% was developed by the integration of dehydration and oxidation over Amberlyst-15 and Mn6Fe1Ox, respectively.