Vacuum Maintenance Performance of MOF Adsorbents for Liquid-Hydrogen Storage Tanks

Liquid-hydrogen tank containers have received increasing attention for hydrogen storage and transportation applications owing to their high hydrogen storage density and relatively low system cost. However, maintaining a high vacuum environment of 10^-2 Pa in the interlayer of liquid-hydrogen containers remains challenging, with residual hydrogen contributing significantly to vacuum failure. Thus, high-performance, low-cost hydrogen adsorption materials and their corresponding vacuum maintenance mechanisms must be developed urgently. In this study, the adsorption characteristics of HKUST-1—a metal-organic framework—and its application mechanism in 40-foot (length: 12192 mm, width: 2438 mm, height: 2591 mm) liquid hydrogen tank containers were investigated. The results show that the self-synthesized HKUST-1, with a specific surface area of 1426 m²/g and a bimodal pore structure, exhibited excellent physical adsorption potential. The material demonstrated reversible hydrogen adsorption in the liquid-hydrogen temperature range and maintained effective adsorption at extremely low pressures, thus serving dual functions for both cryogenic and ambient-temperature adsorption. Dynamic vacuum model results reveal that using a small amount of HKUST-1 at the cold end of the interlayer reduced the required amounts of both cryogenic and ambient-temperature adsorbents, thereby effectively enhancing the physical adsorption of residual hydrogen and retarding the increase of H₂ partial pressure under extreme vacuum conditions. This study provides a new material solution for vacuum maintenance in liquid-hydrogen storage and transportation equipment, as well as offers valuable insights into the safety design and operation of liquid-hydrogen tank containers.