In this article, the relationship between morphological characteristics and de/hydration performance was assessed on an innovative magnesium sulphate heptahydrate filled silicone composite foam for sorption thermal energy storage applications. Hydration and dehydration aspects of the foam were investigated by varying salt hydrate filler content. The composite foam showed a mixed open/closed cellular structure, whose morphology was dependent on the filler content present in the formulation. Low salt content foams (40 wt% and 50 wt% salt content) highlighted a predominantly open cell structure with a strong interconnection between bubbles. High salt content foams (60wt% and 70 wt% salt content) showed a structure for which the cellular interconnections were more limited. Compared to pure salt, it was evidenced that salt filled composite foams have a significant de/hydration capacity. The water/salt reaction is not hindered by the foaming process. Based on morphological and thermo-physical properties of the foam a simplified vapour diffusion flow process in composite foams was proposed. The present work was partially funded by PON “Ricerca e Competitività 2007-13” PON03PE_00206_2 S5 - Smart Small Scale Solar Systems. The work was partially funded by the Spanish government (ENE2015-64117-C5-1-R). The authors would like to thank the Catalan Government for the quality accreditation given to her research group (2017 SGR 1537). GREA is certified agent TECNIO in the category of technology developers from the Government of Catalonia.