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Oxidation of renewable polyol/sugar into formic acid using molecular O2 over heterogeneous catalysts is still challenging due to the insufficient activation of both O2 and organic substrates on coordination-saturated metal oxides. In this study, we develop a defective MnO2 catalyst through a coordination number reduction strategy to enhance the aerobic oxidation of various polyols/sugars to formic acid. Compared to common MnO2, the tri-coordinated Mn in the defective MnO2 catalyst displays the electronic reconstruction of surface oxygen charge state and rich surface oxygen vacancies. These oxygen vacancies create more Mnδ+ Lewis acid site together with nearby oxygen as Lewis base sites. This combined structure behaves much like Frustrated Lewis pairs, serving to facilitate the activation of O2, as well as C–C and C–H bonds. As a result, the defective MnO2 catalyst shows high catalytic activity (turnover frequency: 113.5 h−1) and formic acid yield (>80%) comparable to noble metal catalysts for glycerol oxidation. The catalytic system is further extended to the oxidation of other polyols/sugars to formic acid with excellent catalytic performance. This work develops defective MnO2 catalysts with Frustrated Lewis Pairs through a coordination number reduction strategy to enhance the aerobic oxidation of various polyols/sugars to formic acid. [ABSTRACT FROM AUTHOR]

Several typical pristine Pt/C and Au/C catalysts were investigated for glycerol oxidation to various C 1 -C 3 ketone/acid products via experiments, kinetics analysis, and DFT calculations. The higher metallic state and increased d electrons of Pt/C promote strong adsorption of OH– and enhance oxygen activation, leading to higher selectivity towards lactic acid by facilitating dehydration of C-OH in glyceraldehyde and promoting timely desorption of lactic acid species. Conversely, Au/C exhibits enhanced oxidative cleavage of the C-C bond in glyceric acid leading to increased production of glycolic acid products. Expanding to bimetallic catalysts, it was observed that catalysts with higher Au content exhibit enhanced selectivity towards the oxidation of glyceric acid to glycolic acid, while those with a higher Pt ratio demonstrate increased selectivity for the oxidation of glycerol to lactic acid. [Display omitted] • Several typical pristine Pt/C and Au/C catalysts were investigated for glycerol oxidation via kinetics analysis and DFT calculations. • Pt could facilitate dehydration of C-OH in glyceraldehyde and Au tends to strengthen oxidative cleavage of C-C bond in glyceric acid. • Higher Au content is beneficial to increase selectivity of glycolic acid, whereas higher Pt ratio enhances the selectivity of lactic acid. Fundamental understanding of heterogeneously catalytic aerobic oxidation of polyol is highly desirable for sustainable and efficient chemical synthesis. Herein, based on the purpose of exploring the selectivity of various carboxylic acids on Pt-Au catalysts with different ratios, we conducted a comprehensive investigation into the reaction pathways of glycerol oxidation over pristine Pt/C and Au/C catalysts via experiments, kinetics analysis and DFT calculations. Structural characterizations revealed that Pt/C exhibits a higher metallic state and more d electrons, thus tending to strongly adsorb OH– and promote oxygen activation. Conversely, the weak oxygen activation of Au/C could be attributed to fewer cationic high valence state and d electrons. Furthermore, the Langmuir-Hinshelwood kinetic model and DFT calculations indicate both catalysts exhibit obvious differences in product distribution. Specifically, Pt demonstrated higher selectivity towards lactic acid by facilitating dehydration of C-OH in glyceraldehyde and promoting timely desorption of lactic acid species. In contrast, Au displayed more glycolic acid products caused by strengthening oxidative cleavage of C-C bond in glyceric acid. Expanding to bimetallic catalysts, it was observed that catalysts with higher Au content exhibit enhanced selectivity towards the oxidation of glyceric acid to glycolic acid, while those with a higher Pt ratio demonstrate increased selectivity for the oxidation of glycerol to lactic acid. These findings provide valuable insights for guiding the design and optimization of this catalytic process to achieve targeted product generation. [ABSTRACT FROM AUTHOR]

Achieving efficient catalytic conversion over a heterogeneous catalyst with excellent resistance against leaching is still a grand challenge for sustainable chemical synthesis in aqueous solution. Herein, we devised a single‐atom Pt1/hydroxyapatite (HAP) catalyst via a simple hydrothermal strategy. Gratifyingly, this robust Pt1/HAP catalyst exhibits remarkable catalytic selectivity and catalyst stability for the selective oxidation of C2–C4 polyols to corresponding primary hydroxy acids. It is found that the Pt−(O−P) linkages with strong electron‐withdrawing function of PO43− (Pt1−OPO43− pair active site) not only realize the activation of the C−H bond, but also destabilize the transition state from adsorbed hydroxy acids toward the C−C cleavage, resulting in the sharply increased selectivity of hydroxy acids. Moreover, the strong PO43−‐coordination effect provides electrostatic stabilization for single‐atom Pt, ensuring the highly efficient catalysis of Pt1/HAP for over 160 hours with superior leaching resistance. [ABSTRACT FROM AUTHOR]

Three morphologies of ZnO [spherical (S), rod (R) and disk (D)] were synthesized and tested as supports for Au nanoparticles for the selective oxidation of glycerol, 1,2-propanediol, 1,2-butanediol, and isopropanol at their secondary hydroxyl group to produce the corresponding ketones. The Au-ZnO(0 0 1) interface exhibits a strong electron sink effect and abundant oxygen vacancies, greatly promoting the adsorption of O 2 and the adsorption and conversion of polyols at their secondary hydroxyl moiety. Moreover, the as-formed Auδ+-OH* site resulting from O 2 activation can efficiently extract the hydrogen of the C-H bond of the key RCHO*CH 2 OH intermediate on the Zn-O v site of ZnO(0 0 1) surfaces. Therefore, the Au/ZnO-D exhibits superior catalytic activity (turnover frequency >500h−1) and ketone selectivity (>80 %) than other catalysts with different ZnO facets exposed. [Display omitted] • Three morphologies of ZnO [spherical (S), rod (R) and disk (D)] were synthesized to support Au nanoparticles. • Au/ZnO-D exhibits superior catalytic activity and ketone selectivity. • Au-ZnO(0 0 1) interface exhibits a strong electron sink effect and abundant oxygen vacancies. • Auδ+-OH* site can efficiently extract the hydrogen of the C-H bond of the key RCHO*CH 2 OH intermediate. In-depth understanding and precise tuning of the crystal facet-dependent catalytic properties of supported catalysts are critical for polyol oxidation. Herein, we report a crystal-facet-dependent study of Au-ZnO interfaces for the selective promotion of the oxidation of various polyols and alcohols (glycerol, 1,2-propanediol, 1,2-butanediol, and isopropanol) at the secondary hydroxyl position to produce the corresponding ketones. Three facets of the zinc oxide support, ZnO(1 0 1), ZnO(1 0 0) and ZnO(0 0 1), associated with nanoparticles of various morphologies (spherical (S), rod (R) and disk (D), respectively), were found to induce different electronic local environments and surface oxygen vacancy contents at the Au-ZnO interface. In particular, the ZnO(0 0 1) facet dominating in the Au/ZnO-D nanoparticles can store more electrons from Au, and such electron sink effect, together with the generation of oxygen vacancies (Zn-O v), synergistically enhances the adsorption of O 2 and polyols at the secondary hydroxyl position. Moreover, it was determined that the as-formed Auδ+-OH* site resulting from O 2 activation can efficiently extract the hydrogen of the C-H bond of the key RCHO*CH 2 OH intermediate on the Zn-O v site of ZnO(0 0 1) surfaces. Consequently, the Au/ZnO-D catalyst exhibits unprecedented catalytic activity (turnover frequency >500 h−1) and ketone selectivity (>80 %) for glycerol oxidation. [ABSTRACT FROM AUTHOR]

Achieving efficient catalytic conversion over a heterogeneous catalyst with excellent resistance against leaching is still a grand challenge for sustainable chemical synthesis in aqueous solution. Herein, we devised a single‐atom Pt1/hydroxyapatite (HAP) catalyst via a simple hydrothermal strategy. Gratifyingly, this robust Pt1/HAP catalyst exhibits remarkable catalytic selectivity and catalyst stability for the selective oxidation of C2–C4 polyols to corresponding primary hydroxy acids. It is found that the Pt−(O−P) linkages with strong electron‐withdrawing function of PO43− (Pt1−OPO43− pair active site) not only realize the activation of the C−H bond, but also destabilize the transition state from adsorbed hydroxy acids toward the C−C cleavage, resulting in the sharply increased selectivity of hydroxy acids. Moreover, the strong PO43−‐coordination effect provides electrostatic stabilization for single‐atom Pt, ensuring the highly efficient catalysis of Pt1/HAP for over 160 hours with superior leaching resistance. [ABSTRACT FROM AUTHOR]