Researchers Develop “Molecular Nanovalves” for Gas Storage in Metal Organic Frameworks; Potential for H2 Storage
02 February 2008
Researchers at the University of Calgary (Canada) have developed a new process for capturing and storing gas in metal organic frameworks based on the use of “molecular nanovalves”. The new method of gas storage could yield benefits for capturing, storing and transporting gases more safely and efficiently.
Using the orderly crystal structure of a barium organotrisulfonate, the researchers developed a unique open-channel material that shifts structure to form closed pores in the solid when dehydrated. This occurs through multiple single-crystal to single-crystal transformations. The gas composing the atmosphere during dehydration becomes trapped in the resulting air-tight chambers. On rehydration, the pores open to release the trapped gas.
George Shimizu, David Cramb, Brett Chandler and colleagues from the National Research Council describe their invention of “molecular nanovalves” in a paper published in the current online version of the journal Nature Materials. 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.
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.
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.
—George Shimizu
The 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 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 in Alberta.
—David Cramb
Resources
Brett D. Chandler, et. al. “Mechanical gas capture and release in a network solid via multiple single-crystalline transformations” Nature Materials Published online: 20 January 2008 | doi:10.1038/nmat2101
What about storing methane? If we could figure out a (commercially viable) to use methane in vehicles it would be a huge step forward to sustainability.
Somehow I doubt that this material will ever be used for storing hydrogen. You'd still have the tunneling problem...
Perhaps this material could be used as a unique gas filter. Opening and closing the "valves" rapidly might allow some gases in (through) while keeping others out. I'm thinking that perhaps it would be better (cheaper) than a zeolite filter.
Posted by: GreenPlease | 02 February 2008 at 05:54 PM
@ GreenPlease -
the article doesn't specify which gases could be trapped, presumably because the team hasn't verified the mechanism for specific gases yet. Note that while hydrogen atoms can tunnel through most materials, hydrogen molecules cannot. I do agree that for mobile applications at least, the focus of gas storage systems ought to be on methane instead. However, the researchers may be looking at stationary applications first, and rightly so.
Also, I don't get the impression this is intended as a filter, though perhaps it could be used that way in batch operation.
Posted by: Rafael Seidl | 03 February 2008 at 11:21 AM
Its a good beginning, but its not going to help fuel cell cars very much. storing gas at high densities still takes an incredibly large volume. If they can work it out to store it at high pressures then they have something.
Posted by: fred | 03 February 2008 at 11:57 AM
@Rafael
I envisioned using the "nano valves" as a sort of filter by the following method
-The "valves" have a (nearly) constant size
-By pulsing the valves open and closed, the valve size could effectively be reduced (just theory on my part, an aperture effect if you will...). Shorter pulses decrease the size, longer pulses increase the size. The effective change of size would allow some gases in and keep others out.
-The valves (crystalline structure) would have to be arranged in a very thin film.
-In retrospect, this was blue sky. Your assessment of this being limited to batch operations is probably correct.
Posted by: GreenPlease | 03 February 2008 at 08:59 PM