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【正文预览】
To capture the carbon dioxide generated by coal plants, chemical companies like Dow Chemical Co. and energy giants like Alstom SA have been betting big on liquid solvents like amine, a corrosive derivative of ammonia that has a thirst for binding with CO2.
Problem is, once the two are bound, they never want to part.
In an attempt to circumvent the huge energy demands needed to separate amines from CO2, which can take up to 25 percent of the energy generated by a coal plant, scientists -- many funded by the Department of Energy -- are developing a new generation of porous solids that can trap CO2 and then, almost as easily, let it go.
Such solids come in various forms: carbon derived from sugars and tattooed with microscopic holes; molecular sieves that sift and separate chemicals; and elaborate, Tinkertoy-like molecules that form massive skeletons capable of trapping and holding specific chemicals.
At the forefront of this last field is the laboratory of Omar Yaghi at the University of California, Los Angeles, which over the past decade has helped create a new realm of massive, crystalline molecules called metal organic frameworks. With an acronym that sounds like the name of a fuzzy rodent, different species of MOFs may become the basis for hydrogen fuel tanks, drug-delivery devices and CO2 scrubbers.
Now, the lab has created a new generation of MOFs that have close to the same storage capacity and preference for CO2 as amines do, while only weakly bonding with the molecule. The research will be published later this year; the lab\'s previous reports on the subject have appeared in Science and Nature.
To the naked eye, MOFs look "kind of like a rock," said Bo Wang, a researcher in Yaghi\'s lab. But at the molecular level, these seeming solids look like a massive series of circular cages, almost like a honeycomb or molecular sponge, he said.
Amines, once they have chemically reacted with CO2, must be cooked at 120 degrees Celsius for one to two hours before they let go of their load. According to Wang, it takes two minutes at 60 degrees Celsius for 1 gram of the new MOFs to drop their CO2 and be ready for further use.
The MOFs\' secret is that their frameworks -- which are built out of metal ion clusters connected by organic links -- are easily modified. Yaghi\'s lab has made thousands of different versions of the molecules, testing to see which had the proper shape to selectively admit CO2.
"The genius of the materials that Professor Yaghi has developed is their enormous capacity for CO2," said Joseph Hupp, a chemist at Northwestern University who has developed MOFs that separate CO2 from methane.
Carbon dioxide has a moment where its electrons are not distributed evenly among the molecule, called its quadropole moment, Hupp said. This signature is distinctive from many other gases and allows MOFs, through their arrangement of atoms, to be selective.
Hupp is uncertain that MOFs will easily be applied to the steamy industrial environment of the coal plant. "I think it\'s conceivable, but I\'m not so sure," he said.
Wang thinks he has a molecule that will be ready to scale up to industrial levels in an affordable way. Already, Yaghi\'s lab has partnered with the chemical giant BASF SE to mass-produce three simple MOFs, called Basolite, which are used to absorb a wide range of chemicals.
Once you have the recipe down, MOFs are simple to assemble, Wang said.
"It\'s easy as shake and bake," he said. You have these metals and organic linkers, and you "dump these into the solvent and cook it. And when it cools down you will see crystals. ... It\'s more like self-assembly."
为了"捕获"由火电厂所产生的二氧化碳，化工企业如陶氏化学公司和能源巨头阿尔斯通公司已大量投注液体溶剂例如胺，有腐蚀性的渴求与二氧化碳结合的氨水衍生物。
问题是，一旦它们绑在一起，他们就再也不想分开。
为了规避巨大的能源需求需要把胺和二氧化碳分离，这可能需要多达百分之二十五的燃煤发电厂所产生的能量和科学家-许多资金由能源部-正在开发的新一代多孔固体，几乎一样容易可以捕获二氧化碳，然后消失。
这种固体来来源于各种形式：碳来自糖类和微观洞的纹理; 过滤并且分离化学制品的分子筛; 进而详尽阐，形成大量的可以捕获和绑定框架的化学物质。
这最后领域的前沿是奥马尔亚吉在加州大学洛杉矶分校的实验室，在这过去十年中帮助建立了一个新的境界的大规模、称金属有机框架的水晶的分子或MOFs 。以这样的开头语听起来像一个模糊的啮齿类动物名称，不同品种的MOFs可能成为基础的氢燃料罐，给药装置和二氧化碳洗涤器。
