Conversely, the presence of protons in the 8MR enhances C2H4 diffusion. Substituting some protons in 8MRs containing two Si atoms with Li + ions-which preferentially occupy stable positions in 6MRs-further amplifies the disparity in activation energy barriers between C2H4 and C2H6 diffusion. This aligns with the observed improvement in separation performance as the material transitions from H-SAPO-RHO to Li-2-SAPO-RHO. However, excessive replacement of protons in the 8MR with Li + ions decreases selectivity. This is attributed to the effects of Li + ions in both 6MR and 8MR positions (Fig. ). In such cases, the activation energy barriers for C2H4 and C2H6 diffusion become more comparable, consistent with the separation behavior observed in the Li-3-SAPO-RHO sample.