For example, microporous titanium silicate ETS-4 achieves sequential exclusion of C2H6, CH4, and N2 by progressively reducing pore aperture size with increasing dehydration temperature . Li + -exchanged low-silica zeolite X (Li-LSX) selectively adsorbs N2 over O2 due to stronger interaction between N2 and Li + ions in 4-membered rings (4MRs), making it highly effective for air separation . In another case, the small-pore Ge-containing zeolite ITQ-69 enables kinetic separation of C3H6 from C3H8 because C3H6 reaches thermodynamic equilibrium more quickly . Furthermore, low-silica CHA zeolites with larger cations exhibit enhanced "trapdoor" effects, improving CO2 selectivity in CO2/CH4 and CO2/N2 separations due to stronger interactions at 8MRs .