Dual lattice oxygens in amorphous Zr-doped manganese oxide for highly efficient aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

Abstract

One hurdle in developing transition metal oxide (TMO) catalysts for aerobic oxidation reactions is their need for a low binding energy of the lattice oxygen (OL) to create active OL and a high OL binding energy to maintain structural stability during catalysis. In this work, we prepared amorphous Zr-doped manganese oxide (amor-Zr:MnOx) catalysts carrying dual lattice oxygens that can address such conflicting objectives in catalyst development. In the aerobic oxidation of 5-(hydroxymethyl)furfural (HMF), the amor-Zr0.2MnOx catalyst gave 99% selectivity for 2,5-furandicarboxylic acid (FDCA) and a high FDCA formation rate of 3600 µmolFDCA gcat−1 h−1 in 1 h. To the best of our knowledge, the aerobic oxidation performance of the amor-Zr0.2MnOx catalyst is superior to those of most Mn-based and related TMO-based catalysts under comparable conditions. Experimental and theoretical studies show that the OL in amor-Zr: MnOx can be divided into two groups. One group includes the more stable OL that strengthens the catalyst structure and prevents phase transition, while the other group includes the more reactive OL that improves catalyst activity through the strong adsorption/activation of O2 and helps regenerate OL during catalysis.