When fluids are confined in pores with dimensions in the nanoscale, their properties differ from the bulk mainly due to the solid-fluid interactions and the finite pore size. Understanding these phenomena is of fundamental interest in physics and is relevant for several practical applications. We, thus, propose to perform in-situ neutron diffraction measurements of adsobed CO2 on two model carbon samples (CMKs) having different pore sizes by using a novel high pressure adsorption apparatus in order to reveal both the transition temperature/pressure and the structural details of the confined phase. It is anticipated that the proposed experiment would allow us to map out the phase coexistence curves (solid-liquid, solid-gas, liquid-gas as well as the pertinent hysteresis loops) and make a step towards the development of a theoretical approach on the "thermodynamics of confinement¿.