Researchers have discovered an efficient method of hydrogen storage by developing a material with high storage capacity, deliverability and structural robustness.

This is according to a study, Balancing volumetric and gravimetric capacity for hydrogen in supramolecular crystals, which was a collaborative effort involving teams from the USA, China and Australia.

“The storage of hydrogen is key to its applications. Developing adsorbent materials with high volumetric and gravimetric storage capacities, both essential for the efficient use of hydrogen as a fuel, is challenging,” researchers said. Due to the low volumetric density of hydrogen, it requires 700 bar compressed tanks for storage and transport, making it a costly exercise with associated safety concerns.

Research on hydrogen storage has progressed in developing storage methods that meet gravimetric targets and focus on the weight of the storage material. However, many of these materials have limited volumetric capacity, affecting space efficiency and subsequently impacting the driving range of fuel-cell vehicles.

In response to this problem, researchers developed a controlled catenation strategy in hydrogen-bonded organic frameworks, which aims to achieve higher volumetric capacity while balancing high gravimetric capacity.

According to the researchers, the potential for hydrogen storage in molecular crystals has not been deeply explored because it is challenging to achieve large surface areas and high stabilities at the same time. The stability of the material is then enhanced through catenation.

Catenation generally reduces surface areas and can create non-porous materials by obstructing surface areas so it has been avoided. However, the researchers in this study hypothesised that catenation could be controlled precisely to avoid the loss of accessible surface areas and create a robust material.

The design principle uses hydrogen bonding interactions instead of stacking to direct and define catenation. Subjected to high and low pressures, the catenated organic framework was found to successfully absorb and release hydrogen under both conditions.

“This research demonstrates the potential of supramolecular crystals as promising candidates for onboard hydrogen storage and highlights the potential of a directional catenation strategy in designing robust porous materials with balanced high volumetric and gravimetric surface areas for applications,” researchers concluded.