Atomic, electronic, and compositional structure of quaternary Cd x Zn y SδOγ semiconductor nanoparticles grown on synthesized mordenite-type zeolite (MOR) is discussed in this work. Semiconductor–MOR composites were synthesized using two different methods: by Cd2+-Zn2+-ion exchange with synthesized sodium-mordenite, and by direct synthesis of zinc/cadmium-mordenite through a variant of the sol–gel technique, both followed by sulfidation treatment in H2S flow. We show that Cd x Zn y SδOγ semiconductor nanoparticles grow strongly bonded, revealing a core–shell-type arrangement with a wide-open (a = 8.33 Å) cubic fcc structure, and constrained by the MOR surface structure. Because of the core–shell-type nanoparticles and their observed structural and optical properties, these photoactive composites are promising candidates for applications in the fields of photocatalysis and optoelectronics.