Gas can be mechanically trapped and stored at high densities without using high pressures, say researchers at the University of Calgary, Canada. They claim to have developed a material that could lead to safer and more efficient means of storing carbon dioxide or hydrogen. 

Using the crystal barium organotrisulfonate, the team has created molecular valves of about 0.5nm in diameter that open and shut when water and heat are applied. The structure transforms from an open-channel metal-organic framework into a series of air-tight chambers upon dehydration. This ‘can occur by heating to 400ºC for three hours or by letting it stand at room temperature for three months’, says George Shimizu, Professor of Chemistry at the University. Gases inside the chambers become locked in the closed pores. The cages then open upon immediate contact with water, releasing the gas. 

Researchers have successfully tested the material with oxygen, carbon dioxide, nitrogen and argon, which were retained in dry conditions for several weeks without leaking. Shimizu believes that the sealed storage could last indefinitely at ambient temperatures. The nanovalves can hold four to six molecules at one atmosphere, however, they are still too big and heavy to store the lightest gases – helium and hydrogen. ‘We are looking at several lighter elements, but this requires redesigning the organic part of the structure. [Such a] material is still a way away,’ says Shimizu.