Californian chemists have designed the world's lowest-density crystals for use in clean energy. These new materials, known as covalent organic frameworks (or COFs), have such a low density (0.17 grams per cubic centimeter) that a single gram could cover an area of 4,500 square meters. These COFs could be used to store hydrogen for use as a fuel or to use methane as an alternative fuel. They even could be used to "capture and store carbon dioxide from power plant smokestacks before it reaches the atmosphere."
The image below shows the crystal structure of COF-108. "Synthesized only from light elements (H,B,C,O) COF-108 is the lowest-density crystal ever produced (0.17 g/cm3)." (Credit: José L. Mendoza-Cortés, UCLA) Here is a link to a larger version of this picture that I've slightly reframed.
And below is a scanning electron microscope (SEM) image of COF-108 revealing a deformed spherical morphology. (Credit: Omar Yaghi's research team, UCLA)
Here are some details about COFs, which are the first crystalline porous organic networks.
"These are the first materials ever made in which the organic building blocks are linked by strong bonds to make covalent organic frameworks," Yaghi said. "The key is that COFs are composed of light elements, such as boron, carbon and oxygen, which provide thermal stability and great functionality." COF-108, the latest advance in reticular chemistry development, has a high surface area, with more than 4,500 meters per gram. "One gram, unraveled, could cover the surface area of approximately 30 tennis courts," Yaghi said.
This research work about COFs has been published in Science under the name "Designed Synthesis of 3D Covalent Organic Frameworks" (Volume 316, Number 5822, Pages 268-272, April 13, 2007). Here are two links to the abstract and to some supporting online material (PDF format, 76 pages, 2.86 MB), from which the bottom image in this post has been picked on page 61.
Sources: University of California at Los Angeles news release, April 12, 2007; and various websites
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