Rare earth ion-exchanged zeolites exhibit a tremendous enhancement of luminescence upon treatment with suitable organic complexing agents, as reported here. For Eu3+ exchanged zeolite X, the beta-diketone 1-thienyl-4,4,4-trifluoro- 1,3-butane-1,3-dione leads to the formation of intra-zeolite complexes. Fully coordinated complexes within the supercages may be obtained by the additional coordination of 1,10-phenanthroline (see Figure).