The thermal decomposition of copper (11) acetylacetonate (Cu(I1)(acac)(2)) in supercritical carbon dioxide (scCO(2))was investigated via in situ UV-vis spectroscopy. Release of acetylacetone ligands from the central metal atom was observed as the initial step in the decomposition. The kinetics of the decomposition at 423-453 K and 15-25 MPa in scCO(2) were studied. The decomposition reaction generally followed the first-order kinetics. The reaction rate was slightly increased with an increase in the pressure, due to changes in the scCO(2) density. The activation energy of the decomposition was calculated as 60.3 kjmol(-1) at 15 MPa, 56.3 kjmol(-1) at 20 MPa and 52.4 kJmo1(-1) at 25 MPa, which are lower values than those observed in air and in vacuum. The pressure dependence of the activation energy of the decomposition reaction was clarified quantitatively for the first time, and revealed the energy conservation benefit of using scCO(2) as a process solvent for a variety of metal/metal oxide deposition process of nanomaterials. (C) 2016 Elsevier B.V. All rights reserved.