Photocatalytic de-NOx results using the visible white LED lamp are shown in Figure S9.Specimens showed themselves to be photocatalytically active even using a lamp with no UV componentalthough less active than with the solar lamp. Activity under visible light illumination might be explained by the mineralogical composition of the specimens: they are indeed composed of anatase and rutile TiO2 polymorphs (see Table S1). Anatase and rutile nanoparticles when inform of a heterojunction are capable of absorbing visible light, and thus enable photocatalytic activity under visible light illumination [40].