Zeolites and mesoporous materials were systematically modified by ion exchange and impregnation with hygroscopic salts to improve their storage capacity in thermochemical storage of heat. The sorption properties of those potential storage materials against water were investigated with physico-chemical methods such as thermogravimetry, differential scanning calorimetry, microcalorimetry and isotherm measurements confirming the improvement of the storage properties. Selected materials were pelleted and investigated in a lab-scaled storage to prove the performance of the modified storage materials. Two zeolite based materials with a charging temperature of approximately 450 K but a high temperature lift and an improved storage density of up to 576 kJ/L were found. Impregnated mesoporous materials show a much lower temperature lift, however, they offer a potential storage density of about 864 kJ/L at a charging temperature of about 390 K. (C) 2003 Elsevier Ltd. All rights reserved.