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PUBLIC RELEASE DATE:
27-Jan-2014

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Contact: Charlotte Hsu
chsu22@buffalo.edu
716-645-4655
University at Buffalo
@UBNewsSource

Swiss cheese crystal, or high-tech sponge?

The remarkable properties of a new, porous material could lead to advances in microscopic sponging

IMAGE: Created by chemists at the University at Buffalo and Penn State Hazleton, this sponge-like crystal contains many pores that change shape when exposed to ultraviolet (UV) light. In addition, the...

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BUFFALO, N.Y. -- The sponges of the future will do more than clean house.

Picture this, for example: Doctors use a tiny sponge to soak up a drug and deliver it directly to a tumor. Chemists at a manufacturing plant use another to trap and store unwanted gases.

These technologies are what University at Buffalo Assistant Professor of Chemistry Jason Benedict, PhD, had in mind when he led the design of a new material called UBMOF-1. The material -- a metal-organic framework, or "MOF" -- is a hole-filled crystal that could act as a sponge, capturing molecules of specific sizes and shapes in its pores.

Swiss cheese-like MOFs are not new, but Benedict's has a couple of remarkable qualities:

IMAGE: Created by chemists at the University at Buffalo and Penn State Hazleton, this sponge-like crystal contains many pores that change shape when exposed to ultraviolet light.

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Benedict's team reported on the creation of the UBMOF on Jan. 22 in the journal Chemical Communications. The paper's coauthors include chemists from UB and Penn State Hazleton.

"MOFs are like molecular sponges -- they're crystals that have pores," Benedict said.

"Typically, they are these passive materials: They're static. You synthesize them, and that's the end of the road," he added. "What we're trying to do is to take these passive materials and make them active, so that when you apply a stimulus like light, you can make them change their chemical properties, including the shape of their pores."

Benedict is a member of UB's New York State Center of Excellence in Materials Informatics, which the university launched in 2012 to advance the study of new materials that could improve life for future generations.

To force UBMOF-1 respond to ultraviolet light, Benedict and colleagues used some clever synthetic chemistry.

IMAGE: The crystal turns red after exposure to ultraviolet light.

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MOF crystals are made from two types of parts -- metal nodes and organic rods -- and the researchers attached a light-responsive chemical group called a diarylethene to the organic component of their material.

Diarylethene is special because it houses a ring of atoms that is normally open but shuts when exposed to ultraviolet light.

In the UBMOF, the diarylethene borders the crystal's pores, which means the pores change shape when the diarylethene does.

The next step in the research is to determine how, exactly, the structure of the holes is changing, and to see if there's a way to get the holes to revert to their original shape.

Rods containing diarylethene can be forced back into the "open" configuration with white light, but this tactic only works when the rods are alone. Once they're inserted into the crystal, the diarylethene rings stay stubbornly closed in the presence of white light.

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