Enhanced thermal stability and shape stabilization of n-octadecane via nano-confinement in a nickel-based metal-organic framework for thermal energy storage

This study demonstrates the significant improvement of thermal stability and shape stabilization of n- octadecane, an organic phase change material (PCM), through its nano-confinement within a nickel-based metal-organic framework (Ni-MOF). The Ni-MOF was produced via a solvothermal process and exhibited a high surface area of 1425 m²g −1 and a tailored pore size of 2.7 nm which is ideal for encapsulating the PCM. Wide-ranging characterization, including FTIR, XRD, DSC, BET, TGA, and SEM analyses were carried out. The BET result revealed a substantial decrease in surface area from 1425 m²g −1 to 251 m²g −1 which confirms the successful and complete infiltration of n- octadecane into the porous matrix of the MOF. The resulting shape-stabilized composite PCM exhibits a high latent heat of 200 J g −1 with a stable phase transition temperature of 29.5 °C. Crucially, thermogravimetric analysis (TGA) revealed a dramatic increase in thermal stability, with the onset of decomposition for the confined PCM shifting to temperatures above 200 °C, compared to ∼140 °C for pure n- octadecane. This is a direct consequence of the nano-confinement effect, which effectively prevents leakage and volatilization. By combining high energy storage density with moderate thermal and structural stability, this n- octadecane/Ni-MOF composite presents a highly promising material for sustainable thermal energy storage and conservation in buildings and other energy-intensive related applications.