Size-matched polyoxometalate encapsulated in UiO-66(Zr): an extraordinary catalyst with double active sites for the highly efficient ultra-deep oxidative desulfurization of fuel oil

In this study, for the first time, we selected a size-matched polyoxometalate α-Mo8O26, and successfully prepared Mo8-UiO-66(Zr) as a catalyst with double active sites for extractive and catalytic oxidative desulfurization systems (ECODS). UiO-66(Zr) can encapsulate Mo8O26 in the cage and avoid its leaching, while the sulfur compounds can also enter the cage to approach the sites. As a result, in the presence of H2O2 as an oxidant, the catalyst exhibited extraordinary oxidative desulfurization performance towards benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT). It only takes 10 min for the desulfurization efficiency to reach 100%. The catalyst can be reused for at least 4 times without significant loss in the desulfurization activity. Also, the possible reaction mechanisms of the catalytic oxidation process have also been proposed.