Enhanced Basicity of MnOx‐Supported Ru for the Selective Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Furandicarboxylic Acid

Abstract The present study focused on developing a stable basic MnOx support for Ru (RuMn) for the efficient oxidation of 5‐hydroxymethylfurfural (HMF) to 2,5‐furandicarboxylic acid (FDCA) in water in the absence of an external base. A series of MnOx supports, synthesized via hydrothermal approach using urea as precipitant, was prepared by thermal treatment at various temperatures (300–800 °C) before doping with Ru. The RuMn‐2 (1 wt % Ru, MnOx calcined at 400 °C) possessed a large number of basic sites (1.72 mmol g −1 ) based on CO 2 temperature‐programmed desorption analysis, affording an FDCA yield of 87 % with a turnover frequency of 22 h −1 . Transmission electron microscopy energy‐dispersive X‐ray spectroscopy elemental mapping of RuMn‐2 showed a high dispersion of Ru over the surface of MnOx, contributing to the efficient HMF oxidation. Moreover, X‐ray diffraction, X‐ray photoelectron spectroscopy, and H 2 temperature‐programmed reduction indicated that the predominant MnO 2 phase (ϵ‐MnO 2 ) played a vital role in HMF oxidation. RuMn‐2 was recyclable for up to four runs without significant loss in the activity and retained its structural integrity.