EcoMnOx, a Biosourced Catalyst for Selective Aerobic Oxidative Cleavage of Activated 1,2-Diols

A novel catalyst, EcoMnOx, was prepared from waste biomass of Mn-hyperaccumulating plants. The valorization of this Mn-rich biomass is an alternative to its costly usual disposing and provides a new source of Mn. Extracted metal ions, including Mn ²⁺, were oxidized in mild conditions by H₂O₂/NaOH to afford EcoMnOx, as a polymetallic oxide material containing from 8.9 to 14.1 wt % Mn. Spectroscopic studies of this material revealed the presence of Mn layered mixed oxides, rich in Mn^IV along with Mn^III and Mn^II species. EcoMnOx catalytic properties were assessed in the aerobic oxidative cleavage of 1,2-diols, under atmospheric pressure of O₂ or air. With only 10 mol % Mn, up to complete conversions were obtained on activated benzylic and allylic diols, with excellent selectivity toward aldehydes or ketones (98-99%). Moreover, because of its heterogeneous nature, the catalyst can be removed easily by filtration, and reapplied for a minimum of six successive runs without any loss of activity. Finally, E-factor analysis showed the EcoMnOx generates 4 to 17 times less waste compared to classical reagents such as NaIO₄ and Pb(OAc)₄, respectively, highlighting the sustainable assets of this new heterogeneous catalyst.