Synthesis and characterization of (RPh3P)3[Bi3I12] (R = Me, Ph) iodobismuthate complexes for photocatalytic degradation of organic pollutants

Phosphonium iodobismuthates(III) (MePh3P)3[Bi3I12] (1) and (Ph4P)3[Bi3I12] (2) were prepared, and X-ray crystal structures were determined for both complexes. Photophysical behavior of both complexes was determined via diffuse reflectance spectroscopy and photoluminescence measurements. Photoluminescence results for complex 2 revealed room temperature emission, which has been rarely reported by bismuth compounds. Low-temperature luminescence scans further indicated a dramatic change in emission properties between the MePh3P+ and Ph4P+ complexes. Photodegradation studies using both ultraviolet and visible light were carried out to determine the light-absorbing capabilities of both complexes. Visible light-promoted degradation studies in the presence of catalytic amounts of 1 and 2 showed significant degradation of aqueous methylene blue and carbaryl solutions over a period of 1 h. The reported photoirradiation studies indicated the phosphonium iodobismuthate salts promote visible light harvesting and facilitate catalytic dye photosensitization. This sensitization allows for the degradation of organic pollutants in the presence of visible light and suggests coupling with fluorescence dyes is viable in photovoltaic applications.