Metal-organic frameworks (MOFs) often illuminated as crystal sponges are a key class of materials known to bear pores. These are openings on the nanoscale that can hoard gases which are typically troublesome to store and transport. A report by chemists from UCLA and South Korea suggests that the ‘ultimate porosity of a nano-material’ has now been achieved. This, they say is a world record for both porosity and the ability to capture CO2 in MOFs.
Porosity is alleged to be important in compacting huge amounts of gases into smaller volumes. It is also a significant characteristic in pulling in carbon dioxide and according to the scientists this finding could make way for comparatively cleaner energy. Moreover, it may also help to capture CO2 emissions much before they get to the atmospheric surface, leading to global warming and other environmental hazards.
“We are reporting the ultimate porosity of a nano-material; we believe this to be the upper limit or very near the upper limit for porosity in materials,” mentioned the paper’s senior author, Omar Yaghi, a UCLA professor of chemistry and biochemistry and a member of both the California NanoSystems Institute (CNSI) at UCLA and the UCLA–Department of Energy Institute of Genomics and Proteomics.
“Porosity is a way to do a lot with little,” added Yaghi, who holds UCLA’s Irving and Jean Stone Chair in Physical Sciences and directs the CNSI’s Center for Reticular Chemistry. “Instead of having only the outside surface of a particle, we drill small holes to dramatically increase the surface.”
Yaghi along with lead author Hiroyasu (Hiro) Furukawa, co-author Jaheon Kim and colleagues, reveals two materials that appear to break the porosity record by a very large margin. The first material is MOF-200, and the second is MOF-210. MOFs as per the new investigation are similar to scaffolds comprising of linked rods having nanoscale pores which sport just the correct dimensions needed for capturing CO2. With components that can be altered approximately as desired, these materials were invented by Yaghi in the early 1990s. His laboratory fabricated several hundred MOFs boasting of a range of properties and structures. MOFs are said to have held the record for highest porosity of any material since 1999. They can be tailored from affordable ingredients like zinc oxide and terephthalate. The former is a common additive in sunscreen while the latter exists in plastic soda bottles.
The key to making highly porous structures was uncovered by Yaghi and ever since, chemists seem to be in a race to attain surface areas for materials that may have the highest porosity. Reportedly Yaghi, Furukawa and Kim have now made MOFs that have double the porosity as against MOF-177 which had crossed past the earlier porosity record. Additionally, the new material is alleged to have thrice the porosity of MOF-5 and nearly 10 times the porosity of the most porous material before 1999. This should make these materials capable of housing approximately twice the amount of gas that they could in 2004.
“If I take a gram of MOF-200 and unravel it, it will cover many football fields, and that is the space you have for gases to assemble,” Yaghi further explained. “It’s like magic. Forty tons of MOFs is equal to the entire surface area of California.
He goes on to share, “This is only the beginning of MOFs because now we can see the platform of materials on which we can build. In science, achieving the limit by experiment is magnificent, and now we can test the properties of these materials for various applications. Requirements for making a viable material for carbon dioxide capture are high capacity and high selectivity. We reported before on how to get high selectivity for carbon dioxide; now we are showing how to get high capacity. The industrial applications are being deployed or, in certain cases, are in the process of being developed. Many companies are working on the development of MOFs.”
An accomplishment for CO2 storage capacity has also been reported by Yaghi, Furukawa and Kim in Science. This is believed to be mainly due to MOF-200 and MOF-210 taking up the highest amount of hydrogen, methane and carbon dioxide, by weight, ever. Around February this year, Yaghi accompanied by UCLA graduate student Hexiang Deng, Furukawa and UCLA colleagues also revealed their conception of a synthetic gene that had the ability to arrest CO2 emissions.
The new research adds to this space by apparently paving the path for creation of synthetic gene using MOF-200 and MOF-210. Thus, it should offer a larger surface area. A way to evacuate completely the solvent that would in other cases fill the holes was discovered by Hiro. Allowing access to the porosity, Yaghi suggests this to be quite like magic.
The research will be published July 23 in the print edition of the journal Science and is currently available in the journal’s advance online edition.