The aim of this work is to study the effect of CO 2 under pressure on hybrid inorganic–organic polymer electrolytes, by using broad band dielectric spectroscopy (BDS) in the frequency interval 40Hz–10MHz and in the temperature range of −80 to 120°C.Eleven inorganic–organic hybrid materials of the ORMOCERs type, with general formula {Al[O(CH 2 CH 2 O) 8.7 ] ρ /(LiClO 4 ) z } n were treated by applying CO 2 at 293K and 5MPa. The results demonstrated that the CO 2 treatment generally depressed the conductivity of about one order of magnitude. The decreased conductivity in treated complexes is explained in terms of a smaller anion-trapping ability of the Al centers. Residual CO 2 molecules are likely to inhibit the interaction of the perchlorate anions with Al centers within the structure. Segmental motion of the polymer chains plays a crucial role in the conductivity of investigated samples, while the ion-hopping phenomenon is the most important charge transfer mechanism both in the pristine and CO 2 treated materials.Equivalent conductivity studies have elucidated the different ionic species present at various salt concentrations and gave insight about the role of CO 2 in modifying the transport properties of the samples.