The free energy profile for C2H4 diffusion (Fig. ) shows a pronounced asymmetry. The barrier for crossing the proton-containing window dropped to 59 kJ/mol, much lower than the 81 kJ/mol observed for an 8MR without a proton (e.g., in AlPO). This reduction, as summarized in Table , highlights the critical role of protons in promoting C2H4 diffusion through the framework. and Fig. and). This modest increase likely arises from reduced framework flexibility in Li-SAPO-RHO. In this configuration, both C2H4 and C2H6 diffuse through the 8MR windows with minimal interaction with the Li + ions in the 6MRs (fig. for C2H6 and fig. ).