CO2 must be captured as swiftly and as efficiently as possible.
Metal–organic frameworks (MOFs) are one class of crystalline adsorbent materials that are believed to be of huge potential in CO₂ capture applications because of their advantages such as ultrahigh porosity, boundless chemical tunability, and surface functionality over traditional porous zeolites and activated carbon.
Importantly, MOFs have the largest surface areas of any known material: the size of two American football fields (115.2 ft²/ 5.4 m²)) in a single gram, offering plenty of space for “guest molecules” such as CO2 to get caught in millions of molecular cages. The “ZIF-8” MOF is already being used to capture and store toxic gases, and it is cheap and easy to synthesise.
MOFs are coming of age. Their numbers have been mushrooming at an unprecedented rate since Omar M. Yaghi, a Jordanian-American chemist uncovered their potential nearly 20 years before, and today the structures of over 6000 new MOFs are published each year.
Stuart James, chair of inorganic chemistry at Queen’s University Belfast in the UK and co-founder of MOF Technologies, secured US$ 87,500 to work along 14 partners from 8 countries to develop and demonstrate the performance of MOF.
Christopher Wilmer, Assistant Professor of Chemical and Petroleum Engineering at the University of Pittsburgh’s Swanson School of Engineering has collaborated with Jan Steckel, research scientist at the US Department of Energy’s National Energy Technology Laboratory, and Pittsburgh-based AECOM to develop a computational modeling method which may help to fast-track the identification and design of new carbon capture and storage materials such as MOF for use by the nation’s coal-fired power plants.
Scientists at the U.S. Department of Energy’s SLAC Laboratory and Stanford University have taken the first images of CO₂ molecules captured within a MOF. The images, made at the Stanford-SLAC Cryo-EM Facilities, show two configurations of the CO₂ molecule in its cage, in what scientists call a guest-host relationship; reveal that the cage expands slightly as the CO₂ enters; and zoom in on jagged edges where MOF particles may grow by adding more cages.(moftechnlogies.com)
Researchers at the Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Japan, along with colleagues at the University of Tokyo and Jiangsu Normal University in China have created an MOF they call a porous coordination polymer (PCP).
It has an organic component with a propeller-like as molecular structure, and as CO2 molecules approach the structure, they rotate and rearrange to permit CO2 trapping, resulting in slight changes to the molecular channels within the PCP. This allows it to act as molecular sieve that can recognize molecules by size and shape.
The PCP is also recyclable; the efficiency of the catalyst did not decrease even after 10 reaction cycles. After capturing the carbon, the converted material can be used to make polyurethane, a material with a wide variety of applications including clothing, domestic appliances, and packaging.
The researchers tested their material using X-ray structural analysis and found that it can selectively capture only CO2 molecules with ten times more efficiency than other PCPs thus opening up an avenue for future research into carbon capture materials.(icems.kyoto-u.ac.jp)
Bio-mimicking the precise ion selective filtering capabilities of a living cell, researchers at Monash University, CSIRO, the University of Melbourne with The University of Texas at Austin, have developed a synthetic MOF-based ion channel membrane that is precisely tuned, in both size and chemistry, to filter lithium ions in an ultra-fast, one-directional and highly selective manner.
This solution opens up the possibility to create a revolutionary filtering technology that could substantially change the way in which lithium-from-brine extraction is undertaken. Energy Exploration Technologies, Inc. (EnergyX) in Newark, California has executed a worldwide exclusive license to commercialise the technology. (monash.edu and energyx.com)
Simon Weston and a team at ExxonMobil, collaborating with Jeffrey Long, UC Berkeley professor of chemistry and of chemical and biomolecular engineering and senior faculty scientist at Lawrence Berkeley Lab, and his group in UC Berkeley’s Center for Gas Separations, have developed a new material that could capture more than 90% of CO2 emitted from industrial sources using low-temperature steam, requiring less energy for the overall carbon capture process.
Laboratory tests indicate the patent-pending materials—tetraamine-functionalized metal organic frameworks—capture carbon dioxide emissions up to six times more effectively than conventional amine-based carbon capture technology. Using less energy to capture and remove carbon, the material has the potential to reduce the cost of the technology and eventually support commercial applications.
This is the result of eight years’ R&D. Tetraamine molecules are added to a magnesium-based MOF to catalyze the formation of polymer chains of CO2 that could then be purged by flushing with a humid stream of carbon dioxide. By manipulating the structure of the metal organic framework material, the team of scientists and students demonstrated the ability to condense a surface area the size of a football field, into just one gram of mass—about the same as a paperclip—that acts as a sponge for CO2.
Additional research and development will be needed to progress this technology to a larger scale pilot and ultimately to industrial scale.
Discover Solution 270: Nature Urbaine
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