TiN doped Ni–Co bimetal organic framework based-composite phase change material with enhanced photothermal conversion performance

Shape stability and excellent photothermal conversion performance are critical for composite PCMs in the field of solar energy utilization. This study prepares a nickel and cobalt-based bimetal organic framework (Ni–Co-BTC) which is further employed as the supporting material for 1-octadecanol (OD). The flower-like Ni–Co-BTC with an interconnected network exhibits large specific surface area, pore volume, and appropriate pore size distribution, which is conducive to the encapsulation of OD (up to 70 wt%). In addition, TiN nanoparticles are added to enhance the photothermal conversion performance of composite PCM. Therefore, the obtained OD/Ni–Co-BTC/TiN composite PCM exhibits considerable thermal energy storage capacity (145.8 J/g) and remarkable photothermal energy conversion efficiency (up to 97.75%). Furthermore, the composite PCM has outstanding thermal stability and reliability, and the phase change enthalpy is reduced by only 1.7% after 100 cycles. Accordingly, the composite PCM shows a promising application potential in solar energy harvesting, conversion and storage.