Unsaturated Penta-Coordinated Mo5c5+ Sites Enabled Low-Temperature Oxidation of C-H Bonds in Ethers

Selective oxidation of C-H bonds under mild conditions is one of the most important and challenging issues in utilization of energy-related molecules. Molybdenum oxide nanostructures containing Mo5+ species are effective for these reactions, but the accurate identification of the structure of active Mo5+ species and the catalytic mechanism remain unclear. Herein, unsaturated penta-coordinated Mo5c5+ with a high fraction in MoOx fabricated by the hydrothermal method were identified as the active sites for low-temperature oxidation of dimethyl ether (DME) by the deep correlation of characterizations, density functional theory calculations, and activity results, giving a methyl formate selectivity of 96.3% and DME conversion of 12.5% at unreported 110 °C. Low-temperature electron spin resonance (ESR) and quasi in situ X-ray photoelectron spectra (XPS) with the designed experiments confirm that the Mo5c5+ species can be formed in situ. Molybdenum located at the pentachronic site is preferable to significantly promote the oxidation of the C-H bond in CH3O* at lower temperatures.

Atomically Mo-Doped SnO2-x for efficient nitrate electroreduction to ammonia

Electrochemical NO3--to-NH3 reduction (NO3RR) emerges as an appealing strategy to alleviate contaminated NO3- and generate valuable NH3 simultaneously. However, substantial research efforts are still needed to advance the development of efficient NO3RR catalysts. Herein, atomically Mo-doped SnO2-x with enriched O-vacancies (Mo-SnO2-x) is reported as a high-efficiency NO3RR catalyst, delivering the highest NH3-Faradaic efficiency of 95.5% with a corresponding NH3 yield rate of 5.3 mg h-1 cm-2 at -0.7 V (RHE). Experimental and theoretical investigations reveal that d-p coupled Mo-Sn pairs constructed on Mo-SnO2-x can synergistically enhance the electron transfer efficiency, activate the NO3- and reduce the protonation barrier of rate-determining step (*NO→*NOH), thereby drastically boosting the NO3RR kinetics and energetics.

Preparation of 2D Polyaniline/MoO3- x Superlattice Nanosheets via Intercalation-Induced Morphological Transformation for Efficient Chemodynamic Therapy

Organic intercalation of layered nanomaterials is an attractive strategy to fabricate organic/inorganic superlattices for a wide range of promising applications. However, the synthesis of 2D organic/inorganic superlattice nanosheets remains a big challenge. Herein, the preparation of 2D polyaniline/MoO_{3- x} (PANI/MoO_{3- x} ) superlattice nanosheets via intercalation-induced morphological transformation from MoO₃  nanobelts, as efficient Fenton-like reagents for chemodynamic therapy (CDT), is reported. Micrometer-long MoO₃  nanobelts are co-intercalated with Na⁺ /H₂ O followed by the guest exchange with aniline monomer for in situ polymerization to obtain PANI/MoO_{3- x} nanosheets. Intriguingly, the PANI intercalation can induce the morphological transformation from long MoO₃  nanobelts to 2D PANI/MoO_{3- x} nanosheets along with the partial reduction of Mo⁶⁺ to Mo⁵⁺ , and generation of rich oxygen vacancies. More importantly, thanks to the PANI intercalation-induced activation, the PANI/MoO_{3- x} nanosheets exhibit excellent Fenton-like catalytic activity for generation of hydroxyl radical (·OH) by decomposing H₂ O₂  compared with the MoO₃  nanobelts. It is speculated that the good conductivity of PANI can facilitate electron transport during the Fenton-like reaction, thereby enhancing the efficiency of CDT. Thus, the polyvinylpyrrolidone-modified PANI/MoO_{3- x} nanosheets can function as Fenton-like reagents for highly efficient CDT to kill cancer cells and eradicate tumors.

Selective oxidation conversion of methanol/dimethyl ether

As important platform compounds, methanol and dimethyl ether (DME) are vital bridges between the coal chemical, petrochemical and fine chemical industries. At present, the synthesis of methanol/DME has been industrialized, and the production capacity is much larger than the market demand. Therefore, the conversion of methanol/DME into more valuable chemicals is an important and significant topic. The synthesis of high value-added oxygenated chemicals and diesel oil additives from methanol/DME by an oxidation method has attracted substantial attention due to it being green and environmentally friendly and having good atom economy. In this feature article, we have summarized the recent advances in the synthesis of formaldehyde, methyl formate, dimethoxymethane, and polyoxymethylene dimethyl ethers, from the selective oxidation of methanol/DME, and further discussed the adsorption and activation of reactant molecules, selective cleavage of C-O, C-H or O-H bonds in methanol/DME molecules and the C-O chain growth in the target products. In the end, major challenges and future prospects are proposed from the viewpoint of catalyst design and application. It is expected that this feature article will provide theoretical guidance for the activation and cleavage of C-O, C-H, or O-H bonds in other small molecules of alcohol/ether as well as low-carbon alkanes, so as to synthesize high value-added chemicals.