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Controllable Assembly of Vanadium-Containing Polyoxoniobate-Based Materials and Their Electrocatalytic Activity for Selective Benzyl Alcohol Oxidation

During the controllable synthesis of two vanadium-containing Keggin-type polyoxoniobates (PONbs), [Ni(en)(2)](5)[PNb(12)O(40)(VO)(5)](OH)(5)·18H(2)O (1) and [Ni(en)(3)](5)[PNb(12)O(40)(VO)(2)]∙17H(2)O (2, en = ethylenediamine) are realized by changing the vanadium source and hydrothermal temperature...

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Detalles Bibliográficos
Autores principales: Li, Xiaoxia, Zhen, Ni, Liu, Chengpeng, Zhang, Di, Dong, Jing, Chi, Yingnan, Hu, Changwen
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9101498/
https://www.ncbi.nlm.nih.gov/pubmed/35566213
http://dx.doi.org/10.3390/molecules27092862
Descripción
Sumario:During the controllable synthesis of two vanadium-containing Keggin-type polyoxoniobates (PONbs), [Ni(en)(2)](5)[PNb(12)O(40)(VO)(5)](OH)(5)·18H(2)O (1) and [Ni(en)(3)](5)[PNb(12)O(40)(VO)(2)]∙17H(2)O (2, en = ethylenediamine) are realized by changing the vanadium source and hydrothermal temperature. Compounds 1 and 2 have been thoroughly characterized by single-crystal X-ray diffraction analysis, FT-IR spectra, X-ray photoelectron spectrum (XPS), powder X-ray diffraction (PXRD), etc. Compound 1 contains a penta-capped Keggin-type polyoxoniobate {PNb(12)O(40)(VO)(5)}, which is connected by adjacent [Ni(en)(2)](2+) units into a three-dimensional (3D) organic-inorganic framework, representing the first nickel complexes connected vanadoniobate-based 3D material. Compound 2 is a discrete di-capped Keggin-type polyoxoniobate {PNb(12)O(40)(VO)(2)} with [Ni(en)(3)](2+) units as counter cations. Compounds 1 and 2 have poor solubility in common solvents and can keep stable in the pH range of 4 to 14. Notably, both 1 and 2 as electrode materials are active for the selective oxidation of benzyl alcohol to benzaldehyde. Under ambient conditions without adding an alkaline additive, compound 1 as a noble metal free electrocatalyst can achieve 92% conversion of benzyl alcohol, giving a Faraday efficiency of 93%; comparatively, 2 converted 79% of the substrate with a Faraday efficiency of 84%. The control experiments indicate that both the alkaline polyoxoniobate cluster and the capped vanadium atoms play an important role during the electrocatalytic oxidation process.