Three new molybdovanadates modified with different organic cations: Syntheses, Structure, efficient catalysis in the hydroxylation of benzene and oxidation of benzothiophene

Phenol, as an important industrial raw material, the traditional three-step method for preparing phenol has drawbacks such as numerous by-products and difficulties in oxidation. In this regard, we use nitrogen-containing cations that can make conjugated π electrons more active to assemble with Keggin-type polyoxometalates with excellent redox properties, which can not only enable Keggin-type polyoxometalates to obtain the catalytic performance of activated benzene rings, but also increase their stability in organic solvents. Therefore, we synthesized three zero-dimensional compounds ((C 10 H 10 N 2 ) 2 [HPMo VI 9 V V 3 O 40 (FeH 2 O) 0.5 ].1.5H 2 O ( 1 ), (C 7 H 10 N 4 ) 2 [H 3 PMo VI 8 V V 4 O 40 ] ( 2 ), (C 9 H 8 N) 3 [PMo VI 8 Mo V 4 V IV 2 O 42 ] ( 3 )) through simple hydrothermal and solvothermal methods using different nitrogen-containing cations and molybdovanadate. Structural analysis indicates that these three compounds are structurally similar, each consisting of its own molybdovanadate anion and protonated organic counter cations. The experiment demonstrated that compound 3 had a yield of 11.2 % and a selectivity of 93 % for phenol at 60°C. To further explore the oxidation performance of the compound, we selected different sulfides for oxidation experiments and found that it could completely oxidize sulfur-containing substances (such as BT) at 90°C. This indicates that the idea of combining molybdovanadate and nitrogen-containing organic cations has a promising application prospect in the benzene hydroxylation and Sulfur oxidation.