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Innovative crystal's got plenty o' nuthin'.



For years, chemists have fantasized about molecular scaffolds that would catalyze the tricky chemistry that enzymes foster. The structures would provide a framework for assembling and dissecting dis·sect  
tr.v. dis·sect·ed, dis·sect·ing, dis·sects
1. To cut apart or separate (tissue), especially for anatomical study.

2.
 organic molecules. Toward this goal, researchers have attempted to make gauzy crystals that are themselves organic.

Scientists repeatedly succeeded in precipitating porous crystals from carboniferous broths, but when removed and dried, the crystals always collapsed.

Now, research teams at the University of Michigan (body, education) University of Michigan - A large cosmopolitan university in the Midwest USA. Over 50000 students are enrolled at the University of Michigan's three campuses. The students come from 50 states and over 100 foreign countries.  in Ann Arbor Ann Arbor, city (1990 pop. 109,592), seat of Washtenaw co., S Mich., on the Huron River; inc. 1851. It is a research and educational center, with a large number of government and industrial research and development firms, many in high-technology fields such as  and Arizona State University Arizona State University, at Tempe; coeducational; opened 1886 as a normal school, became 1925 Tempe State Teachers College, renamed 1945 Arizona State College at Tempe. Its present name was adopted in 1958.  in Tempe have engineered a new crystal architecture, which they describe in the Nov. 18 NATURE. Their prototype material, called MOF-5, remains steady as a rock even when bone dry and heated to 300 [degrees] C.

"I think many people wouldn't even have believed this was possible," comments Stephen Lee, a materials scientist at Cornell University.

The innovation is in the joinery joinery, craft of assembling exposed woodwork in the interiors of buildings. Where carpentry refers to the rougher, simpler, and primarily structural elements of wood assembling, joinery has to do with difficult surfaces and curvatures, such as those of spiral . Earlier organic scaffolds obliged solitary atoms to hold several struts at once, a situation that stretched their capabilities.

For MOF-5, however, Arizona's Hailian Li and his coworkers joined struts using a rugged, 23-atom cluster borrowed from the toolshed tool·shed  
n.
A small building in which tools are kept.

Noun 1. toolshed - a shed for storing tools
toolhouse

shed - an outbuilding with a single story; used for shelter or storage
 of inorganic chemistry inorganic chemistry, the study of all the elements and their compounds with the exception of carbon and its compounds, which fall under the category of organic chemistry. . Around an internal structure of zinc and oxygen atoms, each cluster presents six exposed carbon atoms--four in a plane, with one above and one below. The carbons serve as fastening points for organic struts--in this case, benzene molecules.

Chemists know the value of porous crystals from the many uses of zeolites, naturally occurring minerals that scientists have reproduced and improvised upon in the lab (SN: 3/2/96, p. 135). These inorganic molecular sieves figure centrally in oil refining and in the separation of gases like nitrogen and oxygen.

By constraining the orientations with which two molecules can combine, the myriad identical pockets in these crystals can coax a pool of pure product from a reaction that would otherwise produce a stew or nothing at all.

Engineering such sieves for specific uses poses a challenge: It's hard to predict how inorganic elements will link up. However, fashioning carbon structures is a snap, Lee says. The properties of MOF-5's cavities will be easy to adapt by ornamenting its braces. "You can put anything on a benzene ring benzene ring
n.
The hexagonal ring structure in the benzene molecule and its substitutional derivatives, each vertex of which is occupied and distinguished by a carbon atom.


benzene ring,
n See aromatic ring.
," says Lee. Longer struts should be possible, too.

Chemists eagerly anticipate creating such frameworks to order. MOF-5 and its progeny promise other advantages over their inorganic forebears, as well. MOF-5 is lighter and more porous than any inorganic sieve yet made, its inventors say, and has about six times the interior surface area of its closest competitor.

Porous materials can swallow voluminous quantities of gases like methane and hydrogen, potentially making them into easily transportable alternatives to gasoline. Since the amount of methane that fits into different zeolites is proportional to their internal surface area, MOF-5 or related materials may make such fuels more practical, the researchers say.

Although 60 percent of MOF-5 is empty space, there seems little risk that chemists' enthusiasm is much ado about nothing Much Ado About Nothing is a comedy by William Shakespeare. First published in 1600, it was likely first performed in the winter of 1598-1599,[1] and it remains one of Shakespeare's most enduring plays on stage. .
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Title Annotation:new crystal architecture devised using organic material called MOF-5
Author:Baker, O.
Publication:Science News
Article Type:Brief Article
Date:Nov 20, 1999
Words:484
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