A series of rare-earth phosphine-oxygen complexes containing [PW12O40]3− with highly efficient photocatalytic degradation of MB

Abstract

Metal–organic–inorganic polyacid complexes, as a class of innovative materials combining the properties of metal–organic compounds and inorganic polyacids, have shown great potential and prospects in environmental protection in recent years, especially in the field of photocatalytic degradation of dye wastewater. With their unique structures, good stability and efficient catalytic properties, these complexes have become a hot spot for researchers. In this study, we synthesized a series of metal–organic–inorganic polyacid complexes with novel structures and excellent properties. In this study, rare earth chloride, tetraisopropyl ethylene diphosphate and phosphotungstic acid were used as raw materials. A series of metal–organic–inorganic polyoxometalate complex catalysts with novel structure and excellent properties were synthesized by heating and stirring in a water and acetonitrile mixture. In order to comprehensively analyse the structures and properties of these new catalysts, we employed various characterisation tools, including single crystal X-ray diffraction (SCXRD) to accurately determine the crystal structures of the complexes and reveal their atomic level arrangements; Fourier transform infrared spectroscopy (FT-IR) to confirm the presence of functional groups and the vibrational modes of the chemical bonding; thermogravimetric analysis (TGA) to evaluate the catalysts' thermal stabilities; powder X-ray diffraction (PXRD) to verify the phase purity and crystallinity of the catalysts; ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) to reveal the light-absorption properties of the catalysts; and terahertz (THz) spectroscopy, which provides a unique perspective to understand the electromagnetic response of the catalysts at specific frequencies. Further, we also investigated the photocatalytic degradation performance of the complexes of this system as catalysts in water-soluble dye (methylene blue). Under UV irradiation, all the 11 samples prepared showed similar and efficient photocatalytic activity for the degradation of MB, with degradation efficiencies of 98.48–99.78% within 65 min. The great potential of this system catalyst in dye wastewater treatment was fully demonstrated. Finally, in order to reveal the photocatalytic degradation mechanism, we systematically explored the role of each active species in the photocatalytic degradation process by adding different types of active substance scavengers into the reaction system.