Zinc-Substituted Polyoxotungstate@amino-MIL-101(Al) - An Efficient Catalyst for the Sustainable Desulfurization of Model and Real Diesels

The zinc-substituted polyoxotungstate [PW11Zn(H2O)O-39](5-) (PW11Zn) has been encapsulated within the aluminium(III) 2-aminoterephthalate NH2-MIL-101(Al) metal-organic framework (MOF) either directly through a one-pot microwave-assisted synthesis or by an impregnation method. The resultant composite materials were characterized by elemental analysis, powder X-ray diffraction, FTIR spectroscopy, and P-31 magic-angle spinning (MAS) NMR spectroscopy. The desulfurization of a model diesel containing three refractory organosulfur compounds (1-benzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiophene) was studied with the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate as an extractant, the PW11Zn@MOF composites as sulfoxidation catalysts, and aqueous H2O2 as an oxidant. The composite obtained by direct synthesis was the most efficient catalyst and led to almost complete desulfurization of the model diesel under mild conditions. Moreover, the solid catalyst could be recovered readily and recycled without significant loss of desulfurization performance. The application of this system to the treatment of a real diesel sample provided a very good sulfur removal of 83% when combined with liquid-liquid extraction.