Figures show the patterns of the lead bromide and iodide 2D perovskites with n = 6, 10, and 16 perovskites after water treatment, compared to as-prepared batches. In general, for both series of samples, complete degradation of the materials is not found even after the immersion in water and sample recovery. However, the patterns show an improvement of structural stability by increasing the length of the hydrocarbon chain. In more detail, for the (CnH2n+1NH3)2PbI4 series, extra peaks are found for n=6 and 10, while the patterns before and after the water treatment are superimposable when n=16. For the bromide analogues, while significant differences are found when n=6, a nearly impressive similarity between the patterns before and after the water treatment is found for n=10 and 16. This difference in the