Solid absorption is regarded as an option to separate CO2 from high temperature gases. At present, suitable sorbents are limited to calcium or lithium containing oxides. Among the latter, lithium orthosilicate (Li4SiO4) might be preferred due to its high reactivity for CO2 absorption. Improved sorption properties are obtained by appropriate doping of Li4SiO4. Especially, doping of vacancies into the lattice of crystalline Li4SiO4 seems to be advantageous. This is concluded from sorption experiments of Al- and Fe-cloped Li4SiO4 that are presented in this article. In addition, a comparison to eutectic doping by use of potassium is provided. For the investigation of practical applicability, cyclic absorption/desorption was performed on selected samples. (c) 2006 Springer Science + Business Media, Inc.