Tartaric acid is an important industrial building block in the food and polymer industry. However, green manufacture of tartaric acid remains a grand challenge in this area. To date, chemical synthesis from nitric acid-facilitated glucose oxidation leads to only <10% yield with significant toxics as byproducts. We reported a one-pot aqueous-phase oxidation of glucose and gluconic acid using bimetallic AuPt/TiO2 catalysts in the presence of molecular O2, with ∼50% yield toward tartaric acid at 110 °C and 2 MPa. Structural characterization and density functional theory (DFT) calculation reveal that the lattice mismatch between fcc Pt and bcc Au induces the formation of twinned boundaries in nanoclusters and Jahn–Teller distortion in an electronic field. Such structural and electronic reconfiguration leads to enhanced σ-activation of the C–H bond competing with π–π electronic sharing of the CO bond on the catalyst surface. As a result, both C–H (oxidation) and C–C (decarboxylation) bond cleavage reactions synergistically occur on the surface of bimetallic AuPt/TiO2 catalysts. Therefore, glucose and gluconic acid can be efficiently transformed into tartaric acid in a base-free medium. Lattice distortion-enhanced reconfiguration of the electronic field in Pt-based bimetallic nanocatalysts can be utilized in many other energy and environmental fields for catalyzing synergistic oxidation reactions.

Replacing fossil-derived tartaric acid (TA) with sugar-based TA provides a greener route for synthesizing bioplasticizers. However, the detailed mechanism involving C–H and C–C activation of sugar substrates in this area is still under debate. In this work, the plausible reaction mechanism for activation of −CHO (oxidation) and −COOH (decarboxylation) groups in glucose and gluconic acid molecules in the presence of bimetallic AuPt/TiO2 catalysts has been studied and revealed using the UV–vis technique. It is found that Pt and Au phases in bimetallic catalysts selectively promote C–H and C–C cleavage reactions through σ extraction (n−π*) and a π–π (π–π*) coordination mechanism, respectively. The Au2Pt2/TiO2 (Au/Pt: 1/1 atomic ratio) catalyst displays remarkable activity for primary conversion of glucose to gluconic acid (TOF ∼ 20,260 h–1 at 110 °C). Meanwhile, consecutive conversion of gluconic acid to TA can be selectively accelerated by the Au1Pt2/TiO2 (TOF: 3,159 h–1) catalyst. Thus, a record high TA production rate of 12.3 mol/h/molmetal was achieved in this work. Process design and the purification of product mixtures to obtain high quality TA were also proposed and validated at the laboratory scale. The outcome in this work will provide insights for aqueous phase oxidation for synthesis of various valuable sugar-derived carboxylic acids.