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Nanovalve Material Captures and Stores Gases
20 Feb, 2008 12:37 pm
In a different approach to gas storage, a Ph.D. student, Brett Chandler and two professors, George Shimizu and David Cramb, at University of Calgary along with the Functional Materials group at the National Research Council of Canada have developed a new material that has the ability to capture gas from the environment and store it in molecule-sized cages using so-called ?nanovalves.?
“Typically, gases interact with a solid by either chemically bonding to the surface or physically adsorbing on the surface,” says Shimizu. “A very stable interaction is desirable for stable storage but this is often accompanied by slow access to the gas. We have come up with a material that mechanically traps gas rather than chemisorbing or physisorbing it as the means of storage. This allows storage at high temperature and rapid access at low temperature.” The publication includes a real-time video that shows the bubbling from a crystal sample that accompanies addition of a drop of water.
The material can store many simple gases, such as carbon dioxide, methane, oxygen, and nitrogen. However, a highly appealing target, hydrogen, remains elusive as the gas is much smaller than those mentioned and leaks through the nanovalves. Shimizu says this was really a proof-of-concept and that the system offers many option for tweaking and improving performance.
Shimizu also points out that storing gases in molecularly porous solids is an immense research field with many active groups. The novelty of their work is the fact that the pores close in a gas tight manner and can be controllably re-opened. He goes on to say that from a basic science perspective, the behavior of the compound is exceptionally odd. “Solids that have holes in them need to be robust to support the void in the structure. This typically means they are also very rigid structures. The fact that this solid contains gas-tight pores that can close and open in a regular manner with good stability is incredible.” The regularity of the structural changes allowed for snapshots to be taken of the transformation by X-ray diffraction methods and also gave the researchers the exact dimensions of the molecular cages.
The researchers’ findings are published in the paper, “Mechanical gas capture and release in a network solid via multiple single-crystalline transformations,” by Brett D. Chandler, Gary D. Enright, Konstantin A. Udachin, Shane Pawsey, John A. Ripmeester, David T. Cramb, George K. H. Shimizu, in the January 20, 2008 online issue of Nature Materials.