Synthesis and Characterization of Insoluble Vanadium-containing Keggin-type Phosphomolybdates with <em>n</em>Bu₄N⁺ Counterion: Recyclable Catalysts for 5-Hydroxymethylfurfural Oxidation

Mixed nBu4N+-substituted phosphomolybdovanadates of (nBu4N)2.5+xH0.5PMo12-xVxO40 (x = 1–4) gross composition have been prepared by a promising ecological method and investigated as catalysts for the transformation of 5-hydroxymethylfurfural. It has been shown that activation of vanadium(V) atoms in V2O5 using the H2O2-affected approach followed by their insertion into a Mo-containing framework provides a waste-free synthesis of mixed heteropoly anions. The resulting solids have been characterized by XRD, IR, ICP-AES, N2 adsorption-desorption, and TGA methods to estimate their structural and textural characteristics. The catalysts exhibit significant activity and good reusability (at least five times) in the oxidation of a biomass-derived precursor to produce 2,5-diformylfuran in yield above 90%.