aM2/n:Al2O3 :xSiO2 where M is a cation of valence ???n???, ???a??? has a value of about 0.90???0.2 and ???x??? has a value greater than 11, the composition characterized in that it has the framework structure of zeolite EMT, a cation equivalency of at least 0.7 and an oxygen adsorption capacity of at least 70% of its theoretical capacity as measured at 100 torr and 90??? K.