Construction and photo-thermal extraction catalytic oxidative desulfurization performance of Mo6–Ti-MOFs/g-C3N4 heterojunction catalysts

Abstract

Novel Lindqvist-type polyoxometalate (POM)-based catalysts Mo₆–NH₂-MIL-125/g-C₃N₄ have been synthesized via a solvent evaporation method and applied in the photo-thermal extraction catalytic oxidative desulfurization system (PTECODS). The structure, composition, and morphology of the catalysts were characterized using various techniques, including X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N₂ adsorption–desorption, UV-visible spectroscopy, and others. Mo₆ was uniformly dispersed and acted as an electron acceptor, effectively suppressing the recombination of electron–hole pairs under light irradiation. In PTECODS, with 0.03 g Mo₆–NH₂-MIL-125/g-C₃N₄ photocatalysts (Ti : Mo molar ratio of 1 : 0.5), an O/S ratio of 6 : 1, and [Bmim]PF₆ as the extraction agent, the conversion efficiency of DBT approached 100% within 60 min at 70 °C upon exposure to visible light irradiation. The synergistic interactions between Mo₆–NH₂-MIL-125 and g-C₃N₄ and also between photocatalysis and thermocatalysis contributed to the enhanced oxidative desulfurization performance. The catalysts could be recycled at least eight times without a noticeable decrease in catalytic activity. Finally, a thorough discussion of the potential mechanisms underlying the photo-thermal extraction catalytic oxidative desulfurization process is presented.