Jahn–Teller Effect in Mn ³⁺ Sites Enhances Mn/BiOI Catalyst Activity for Direct Oxidation of Fructose to Glyceric Acid

Glyceric acid is known as one of the most promising biobased hydroxyl carboxylic acids, but it has been reported only sparsely in the context of current sugar refinery. In this work, we demonstrated that the non-noble-based Mn/BiOI catalyst promoted fructose oxidation to glyceric acid in a base-free medium. The key finding is that the Jahn–Teller effect in the Mn3+ crystal field has induced local cooperative octahedral deformation within the lattice, leading to stabilized high-spin Mn3+ species with a t2g3eg1 configuration alongside low-spin Bi3+ species with a 6s1 configuration. The resulting electronic structure provides an optimal number of unpaired electrons in both Mn and Bi orbitals, thereby facilitating the activation of O2 into •O2– in an aqueous medium. Moreover, the electronic configuration facilitates interfacial charge transfer to fructose, enabling the n to σ* transition of the –C–OH group and ultimately triggering selective C–C bond cleavage. In line with this insight, the Mn/BiOI catalyst exhibits superior activity (TOF: 1537 h–1) and good glyceric acid selectivity (45.6%). The experimental results provide both a fundamental rationale and a technological pathway for achieving selective monosaccharide conversion to value-added carboxylic acids for commodity products.