Transition metal ion containing X and A zeolite microporous materials were examined for the photoionization of N-alkylphenothiazine (PCn) with 320 nm irradiation at room temperature. N-Alkylphenothiazine cation radicals were produced in these zeolitic materials and are characterized by electron spin resonance. Copper containing X zeolite serves as an efficient host for the formation and stabilization of methylphenothiazine cation radicals. For methylphenothiazine (PC1), the photoionization efficiency was found to decrease in the order Cu-X-PC1 > Ni-X-PC1 > Co-X-PC1 > H-X-PC1 > Cr-X-PC1 similar to Na-X-PC1 similar to Mn-X-PC1. The photoionization efficiency was found to depend on the nature and concentration of the metal ion.