(anatase/rutile) photocatalyst, and anatase photocatalysts modified with platinum (Pt) or metal oxide (CuOx, FeOx, or VOx) nanoparticles (NP) obtained in our previous work. Please note that the SAC-modified photocatalysts as well as all benchmark photocatalysts were optimized for the highest activity in terms of the co-catalyst loading and other process parameters (such as photocatalyst amount during the experiment; for details see the Supporting Information, Section 1.5, and Figures and), and the data obtained for the respective best-performing materials under optimized conditions are shown in Figure . Firstly, we investigated the photocatalytic activity in photodegradation of 2,4dichlorophenoxyacetic acid (2,4-D, herbicide) as a test pollutant under simulated solar irradiation. The initial degradation rates (Figure ) at SAC-modified a-TiO2-Cu SA , a-TiO2-Fe SA and a-TiO2(400)-V SA photocatalysts were higher by the factors of ~2.1, ~1.6, ~1.7, respectively, as compared to their unmodified counterparts. We note that the photocatalytic degradation of the 2,4-D test pollutant that we followed by changes in UV-Vis electronic absorption leads to its complete mineralization, as evident from the corresponding analyses of the total organic carbon content (TOC, Supporting Information, Figure ). Notably, except a-TiO2-Fe SA , the SAC-modified photocatalysts also exhibited significantly higher initial degradation rates than TiO2 materials modified by corresponding metal oxide nanoparticles. We assume that the beneficial effect of the SACs is mostly related to negligible parasitic light absorption by SACs as compared to corresponding metal oxide nanoparticles. Indeed, the electronic absorption spectra of SAC-modified samples obtained by diffuse reflectance spectroscopy show negligible differences to unmodified materials (Supporting Information, Figure ). The most drastic difference in activity is observed for a-TiO2(400)-V SA which shows an activity higher by the factor of ~6.5 than a material modified with VOx nanoparticles (a-TiO2(400)-VOx NP ), which we ascribe to the blocking effect of VOx nanoparticles for the UV light absorption by TiO2. The significant optical absorption of VOx nanoparticles makes itself apparent by an absorption shoulder down to >500 nm (see Supporting Information, Figure ), which is in contrast to isolated vanadate SACs that are known to absorb only below 320 nm. The vanadate-modified SAC photocatalyst (a-TiO2(400)-V SA ) exhibits the highest degradation rates of all studied materials, outperforming even platinized TiO2 and the commercial P25