Co-O-Mn electron interaction enhances the oxidation activity of Mn2O3

1.Catalyst Preparation DataA series of Mn₂O₃ and Co₃O₄-Mn₂O₃-x catalysts (x represents the theoretical loading of Co₃O₄) were prepared by the precipitation method. Solution A and Solution B were prepared. Solution A consisted of 50 wt.% manganese nitrate solution and different mass ratios of cobalt nitrate hexahydrate dissolved in 150 mL of deionized water (for the preparation of pure phase Mn₂O₃, Solution A contained only 50 wt.% manganese nitrate solution and 150 mL of deionized water). Solution B was ammonium bicarbonate dissolved in deionized water. Solution B was added dropwise into Solution A at a rate of 10 mL/min using a peristaltic pump at room temperature until the pH reached 7, followed by aging for 1 h. Subsequently, the precursor was collected by suction filtration and separation, washed five times with deionized water, and the obtained precipitate was dried in a vacuum oven at 60 °C for 12 h to obtain the precursor. The precursor was calcined in a muffle furnace at 600 °C for 4 h, and the resulting samples were named Co₃O₄-Mn₂O₃-x, where x represents the Co₃O₄ content.A reference catalyst, Co₃O₄/Mn₂O₃-5, was prepared by the impregnation method. 2 g of Mn₂O₃ was placed in a beaker, and Co₃O₄ was added to achieve a theoretical loading of 5 wt.% for the composite catalyst. A small amount of deionized water was added, and the mixture was ultrasonicated for 30 min. Finally, it was dried in a vacuum oven at 60 °C for 12 h and calcined in a muffle furnace at 600 °C for 4 h. The obtained sample was named Co₃O₄/Mn₂O₃-5.Co₃O₄+Mn₂O₃ was prepared by the physical mixing method. Co₃O₄ and Mn₂O₃ were physically mixed to achieve a Co₃O₄ content of 5 wt.%.2.Structural and Compositional Characterization DataX-ray Diffraction (XRD): A Bruker D8 ADVANCE diffractometer was used (Cu Kα, λ=1.54056 Å, 40 kV, 40 mA), with a scan range of 10°–80°, step size of 0.02°, and scanning speed of 4°/min. The original diffraction patterns of all samples were saved in .raw or .txt format. The Mn₂O₃ crystallite size was calculated using the Scherrer equation (Table 1, Table S3), taking the full width at half maximum of the strongest diffraction peak, with K=0.89.X-ray Photoelectron Spectroscopy (XPS): A Thermo Scientific K-Alpha⁺ spectrometer was used (Al Kα, 1486.7 eV). Peak fitting was performed using Avantage software, and binding energies were calibrated using the C 1s peak (284.8 eV). The Mn²⁺/Mn³⁺/Mn⁴⁺ ratios, Co²⁺/Co³⁺ ratios, and the ratio of adsorbed oxygen (Oₐdₛ) to lattice oxygen (Oₗₐₜₜ) were obtained from the Mn 2p, Mn 3s, Co 2p, and O 1s spectra, respectively (Table 1). The average oxidation state (AOS) of Mn was estimated from the Mn 3s multiplet splitting energy (ΔEₛ) using the empirical formula AOS = 8.956 – 1.126ΔE.Inductively Coupled Plasma Mass Spectrometry (ICP-MS): A PerkinElmer Avio 200 instrument was used to determine the actual Co and Mn contents in the catalysts. Data were recorded as mass fractions (wt.%) (Table 1, Table S3). Each sample was measured in triplicate, and the average value was taken, with a relative standard deviation of <3%.Temperature-Programmed Reduction (H₂-TPR): A JWGB HX-100 chemical adsorption analyzer was used. The sample amount was 30 mg. It was first pretreated in Ar at 120 °C for 1 h. After cooling, the gas was switched to 10% H₂/Ar (30 mL/min), and the temperature was raised to 600 °C at a rate of 10 °C/min. Series of curves were obtained at different heating rates (5, 7, 10, 12, 15 °C/min) (Figure 5B-D). The apparent activation energy of the reduction peak was calculated using the Kissinger equation, with the linear correlation coefficient R² for all fits being >0.98.Temperature-Programmed Oxidation (O₂-TPO): The same JWGB HX-100 instrument was used. The sample was pretreated in He at 120 °C for 1 h. After cooling, 5% O₂/He (30 mL/min) was introduced until the baseline stabilized, and then the temperature was raised to 650 °C at a rate of 10 °C/min. Variable heating rate experiments (5–15 °C/min) were conducted to obtain the shift in oxidation peak temperature, and the oxidation activation energy was calculated using the Kissinger equation (Figure 6D).Electron Paramagnetic Resonance (EPR): A Bruker EMXPlus EPR spectrometer from Germany was used. Samples were tested at room temperature to capture the characteristic signal corresponding to oxygen vacancies on the catalyst surface (Figure 7).Ammonia Temperature-Programmed Desorption (NH₃-TPD): Also performed on the JWGB HX-100. After ammonia adsorption, the sample was heated at a rate of 10 °C/min for desorption. The desorption signal was detected by TCD (Figure 8) to compare the density of surface acid sites.3.Catalytic Reaction Performance DataAll catalytic reactions were carried out in a 30 mL high-pressure reactor. The reaction conditions (temperature, pressure, time, stirring speed) and product analysis data were recorded in detail.Benzyl Alcohol Oxidation: Standard conditions: 50 mg catalyst, 2 mmol benzyl alcohol, 10 mL toluene, 1 MPa O₂, 110 °C, 1 h (Figure 2A)；Time curve: Sampling times ranged from 0.5 to 4 h (Figure 2B)；Intrinsic rate measurement: 5 mg catalyst, 20 min reaction, conversion <15% (Figure 2C)；Kinetic experiments: Activation energy was determined by varying the temperature (90–130 °C) (Figure 2D); reaction orders were determined by varying the oxygen partial pressure (0.2–1.0 MPa) and benzyl alcohol concentration (0.2–0.6 mol/L) (Figure 2E, F).Product Analysis: A gas chromatograph (HF-901A, FID detector, nitrogen carrier gas) with an FFAP column (30 m × 0.32 mm × 0.5 μm) was used. Injector temperature: 220 °C, detector temperature: 260 °C, column temperature: 180 °C. Benzyl alcohol and benzaldehyde were quantified using the internal standard method (n-heptane). Calibration factors were determined via standard curves. Each sample was injected in triplicate, and the carbon balance was consistently >95%.Universality Experiments: The reaction conditions and product distributions for the oxidation of furfural, 5-hydroxymethylfurfural (HMF), toluene, and cyclohexane are listed in Table S1. The analysis methods were similar to that for benzyl alcohol, using internal standards of n-heptane (for toluene, cyclohexane) or furoic acid (for HMF).Stability Test: The catalyst was recycled 5 times. After each reaction, it was washed, dried, and a small amount of lost catalyst was replenished. The reaction conditions were the same as the standard conditions (Figure S3).4.Data Summary TablesAll key data are organized in tabular form (Table 1, Table 2, Table S3), containing the following fields: Catalyst Name, Mn₂O₃ Crystallite Size (nm), Actual Co₃O₄ Content (wt.%), Mn²⁺/Mn³⁺/Mn⁴⁺ Ratio (%), Co³⁺/Co²⁺ Ratio (%), Oₐdₛ/(Oₐdₛ+Oₗₐₜₜ) (%), Benzyl Alcohol Conversion (%). Each row corresponds to a specific catalyst sample. The column headers in the tables clearly indicate the physical quantity and its unit. All percentages are either molar percentages or mass percentages.