In the bottom part of Figure , the pattern of Cs2AgBiCl6 double perovskite is reported (with a sketch of its crystal structure in Figure ), displaying a cubic symmetry with Fm3̅ m space group (#225) and a lattice parameter of 10.7761(2) Å, in agreement with previous results. Figure shows a comparison between experimental and calculated pattern for Cs2AgBiCl6. At the top of Figure , the X-ray pattern of pure g-C3N4 nanosheets is reported showing the typical broad peaks around 13° and 28° corresponding to the (100) and ( ) reflections. The patterns of the composites (cfr. Figure ) are dominated by perovskite reflections at high wt% of Cs2AgBiCl6 and the reflections of g-C3N4 start to be evident around 50 wt%. Also, at 10 wt% of perovskite its pattern is still clearly detectable, due to its high scattering power with respect to g-C3N4. Morphological inspection of Cs2AgBiCl6, g-C3N4, and selected composites has been carried out by Scanning Electron Microscopy (SEM) and the results are reported in Figure . g-C3N4 nanosheets have been also characterized by Transmission Electron Microscopy (TEM) and representative images showing their nanostructure are shown in Figure .