We have conducted ab initio Molecular Dynamics simulations of CO2-HF fluid mixture on its T = 3000 K isotherm in the pressure range 0-40 GPa. We predict the formation of new covalent bonds between carbon and fluorine atoms, and between oxygen and hydrogen atoms. As in the case of water (Maillet et al., J. Chem. Phys. 131 (2009) 084107), the dissociation of the HF molecule with pressure is seen as the precursor of this new chemistry at extreme environment. The CO2-HF mixture then exhibits a non-ideal behaviour as pressure increases. The appearance of new chemistry in the high pressure - high temperature regime could be a common feature in ionic liquids. (C) 2011 Elsevier B.V. All rights reserved.