Transition metal oxides (Ti, V, Mo, Cr) incorporated within the framework of zeolites as well as transition metal ions (Cu + , Ag + , Pr 3 + ) exchanged within the zeolite cavities were found to exhibit high and unique photocatalytic activities for various reactions such as the decomposition of NO x (NO, N 2 O) into N 2 and O 2 or the reduction of CO 2 with H 2 O to produce CH 4 and CH 3 OH. Various in situ spectroscopic investigations of these catalytic systems using photoluminescence, X-ray absorption fine structure (XAFS) (X-ray absorption near edge structure (XANES) and Fourier transform of EXAFS (FT-EXAFS)), electron spin resonance (ESR), FT-IR, etc. revealed that the photo-excited states of these transition metal oxides or ions play a vital role in these photocatalytic reactions. The photocatalytic reactivity of these oxides and ions in their efficiency and selectivity were found to depend strongly on their local structures, which are controlled by the unique and restricted framework structures of zeolites.