This is a proof of concept that represents an entirely new way of storing gas, not just improving on a method that already exists. We have come up with a material that mechanically traps gas at high densities without having to use high pressures, which require special storage tanks and generate safety concerns. - George Shimizu, professor of Chemistry at University of CalgaryThe "molecular nanovalves" are based on the orderly crystal structure of a barium organotrisulfonate. The researchers developed a unique solid structure with this material that is able to convert from a series of open channels to a collection of air-tight chambers. The transition happens quickly and is controlled simply by heating the material to close the nanovalves, then adding water to the substance to re-open them and release the trapped gas.
Metal–organic frameworks have demonstrated functionality stemming from both robustness and pliancy and as such, offer promise for a broad range of new materials. The flexible aspect of some of these solids is intriguing for so-called 'smart' materials in that they could structurally respond to an external stimulus.
It is on the basis of such a stimulus-responsive framework that the gas capture device was developed: an open-channel metal–organic framework that, on dehydration, shifts structure to form closed pores in the solid. This occurs through multiple single-crystal-to-single-crystal transformations such that snapshots of the mechanism of solid-state conversion can be obtained.
Notably, the gas composing the atmosphere during dehydration becomes trapped in the closed pores. On rehydration, the pores open to release the trapped gas. For this reason, the new material represents a thermally robust and porous material that is capable of dynamically capturing and releasing gas in a controlled manner:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: biogas :: biohydrogen :: gas capture :: gas storage :: greenhouse gas ::
The researchers from the University of Calgary and the Steacie Institute for Molecular Sciences (National Research Council of Canada) say it represents a novel method of gas storage that could yield benefits for capturing, storing and transporting a range of important gases more safely and efficiently.
The paper includes video footage of the process taking place under a microscope, showing gas bubbles escaping from the crystals with the introduction of water.
The process is highly controllable and because we're not breaking any strong chemical bonds, the material is completely recyclable and can be used indefinitely. - ShimizuThe team intends to continue developing the nanovalve concept by trying to create similar structures using lighter chemicals such as sodium and lithium and structures that are capable of capturing the lightest and smallest of all gases - hydrogen and helium.
These materials could help push forward the development of hydrogen fuel cells and the creation of filters to catch and store gases like CO2 or hydrogen sulfide from industrial operations, says co-author David Cramb.
Capturing and storing (or transforming) greenhouse gases from industrial operations is becoming increasingly important for a transition towards a future low-carbon world. For biofuels in particular, capturing CO2 from the production process is important to improve the greenhouse gas balance of the fuel. The new gas capture technique also has potential applications in capturing and storing biomethane, a fuel obtained from the anaerobic digestion of organic waste.
Brett D. Chandler, Gary D. Enright, Konstantin A. Udachin, Shane Pawsey, John A. Ripmeester, David T. Cramb & George K. H. Shimizu, "Mechanical gas capture and release in a network solid via multiple single-crystalline transformations", Nature Materials, advance online publication Published online: 20 January 2008, doi:10.1038/nmat2101.
University of Calgary: Rounding up gases, nano style - February 1, 2008.