H2O2-based selective oxidations by divanadium-substituted polyoxotungstate supported on nitrogen-doped carbon nanomaterials

• Published in: Catalysis today 2020-09, Vol.354, p.196-203
• Main Authors: Evtushok, Vasiliy Yu, Podyacheva, Olga Yu, Suboch, Arina N., Maksimchuk, Nataliya V., Stonkus, Olga A., Kibis, Lidiya S., Kholdeeva, Oxana A.
• Format: Article
• Language: English
• Subjects: Hydrogen peroxide; N-doped carbon nanofibers; N-doped carbon nanotubes; Polyoxometalates; Selective oxidation
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2019.03.060

[Display omitted] •N-doped carbon nanomaterials are prospective supports for immobilization of polyoxometalates.•A divanadium-substituted phosphotungstate PV2 supported on N-CNMs retains its structure.•The presence of N in N-CNMs ensures strong binding and quasi-molecular dispersion of PV2.•PV2/N-CNMs are truly heterogeneous and recyclable catalysts for selective oxidations with H2O2. In this work, we present a new methodology for the preparation of highly active, selective, leaching-tolerant and recyclable catalysts on the basis of polyoxometalates (POM) and nitrogen-doped carbon nanomaterials. A divanadium-substituted γ-Keggin phosphotungstate [γ-PW10O38V2(μ-O)(μ−OH)]4− (PV2), was immobilized on two types of supports – N-doped carbon nanofibers (N-CNFs) having herring-bone packing of graphite layers and bamboo-like N-doped carbon nanotubes (N-CNTs). Two series of catalysts have been prepared and characterized by elemental analysis, N2 adsorption, TEM, XPS and FTIR techniques. Their catalytic performance was assessed in the liquid-phase selective oxidation of two representative organic substrates, 2,3,6-trimethylphenol and cyclohexene, with aqueous H2O2 as the green oxidant. The presence of nitrogen in the supports ensures strong binding and quasi-molecular dispersion of POM on the carbon surface, which is crucial for the catalytic performance and catalyst stability. The catalysts reveal truly heterogeneous nature of the catalysis and can be easily recovered and reused without loss of the catalytic performance. The morphology of the support has a significant impact on the catalytic performance: the supported PV2 catalysts prepared using N-CNTs are more active and, in general, more selective than the catalysts prepared with N-CNFs.