A mu -Br-bridged dicopper(II) complex, namely [Cu-2(mu -Br)(2). 6H(2)O](ClO4)(2), has been prepared by metal ion grafting. A supported complex catalyst Cu-2(II)(mu -Br)(2)/SiO2 was prepared by modifying the silica surface with NaOEt and anchoring the dicopper(IT) complex precursor on the surface of the support. The structure of the complex catalyst has been characterized by elemental analysis, IR spectra and UV-VIS diffusion reflection spectra. Obtained data were compared with published data of the complex. TPD-MS and TPD-IR investigations indicated that CO2 and ethylene oxide (EO) can be chemisorbed on the surface of the catalyst reversibly in a bridged state and can be desorbed from the surface at 105 and 115 K, respectively. In the high temperature range of 450-573 K, another reversible absorption state for CO2 was also discovered. For EO, however, a decomposition absorption state was found which gave the dissociated species of CH4 and CO. TPSR-MS experiments have shown that CO2 and EO reacted on the surface effectively in the range of 343-413 K. An in situ IR method has been used to study the reactivity of the reactants on the surface of the catalyst, and the target product ethylene carbonate (EC) was detected in the range of 333-413 K. Catalytic experiments indicated that the one-way yield of EC is greater than 8.0% and that the selectivity of EC is greater than 82%. A synergic cyclization reaction pathway is proposed to account for the observed products.