The local environment of zirconium in Zr-silicalite with MEL structure has been studied using the EXAFS technique, The structural parameters indicate the presence of tetrahedrally coordinated, isolated zirconium sites with Si-O-Zr linkages. The experimental results support the location of Zr4+ ions at edge- or corner-sharing positions (N(Zr-O) = 3.9 and N(Zr-Si) = 1.2), rather than in regular substitutional positions. The isolated Zr4+ ions could be reduced to the Zr3+ State on treatment with Hz followed by UV irradiation. The ESR spectra of reduced Zr-silicalite samples of both MFI and MEL structures reveal a distorted tetrahedral geometry around Zr3+ and a d(x2-y2) orbital ground state. The ESR results are consistent with EXAFS findings. The role of these active Zr species in the selective oxidation of phenol is investigated by ESR after interaction of the samples with aqueous H2O2. The formation of a Zr4+-O-2(-.) radical species, and the variation in the g parameter under the influence of solvents such as water, acetonitrile, and methanol are reported. The results confirm the role of Zr4+ as active centers. The coordination of solvent molecules around Zr centers affects the catalytic activity to different extents, in agreement with the difference in ESR signal intensity of the radical species. These isolated active sites are responsible for the formation of superoxide/hydroperoxide species through which the oxygen is transferred to the substrate in the hydroxylation of phenol.