Nanocomposites of cobalt oxide on mesoporous silica support (Co/MCM41) have been synthesized by supercritical fluid reactive deposition (SCFRD) using cobaltocene (CoCp2) as precursor. The study of adsorption isotherm for CoCp2 on MCM41 at 70 degrees C and 11 MPa has revealed an unfavourable adsorbate-adsorbent system with a maximum load of 43 mgCo/gMCM41. Thus, an in situ thermal decomposition of precursor is necessary to obtain higher loadings of active phase. The modelling of the SCFRD process reveals that dissolution is very fast compared to the adsorption of cobaltocene on MCM41, and that Co content is maximum after 1 h of decomposition at 200 degrees C and 14 MPa. The composite material with 4.3 wt.% Co has a BET surface area of 1034 m(2) g(-1), a pore size of 3.9 nm and metal nanoparticles of 20-30 nm. This load can be increased by successive batches of 1 h. (C) 2015 Elsevier B.V. All rights reserved.