One of the most porous materials ever discovered

 The delivery of pharmaceuticals into the human body or the storage of voluminous quantities of gas molecules could now be better controlled, thanks to a study by University of Pittsburgh researchers. In a paper published online January 4 in Nature Communications, a team of chemists and colleagues from Pitt's Kenneth P. Dietrich School of Arts and Sciences and the Pitt School of Medicine and Northwestern and Durham universities have posed an alternative approach toward building porous materials.

Working with metal-organic frameworks -- crystalline compounds comprising metal- cluster vertices linked together by organic molecules to form one-, two-, or three-dimensional porous structures -- researchers addressed changing the size of the vertex (the metal cluster) rather than the length of the organic molecule links, which resulted in the largest metal organic framework pore volume reported to date.

"Think of this the way you imagine Tinkertoys®," said Nathaniel Rosi, principal investigator and assistant professor in Pitt's Department of Chemistry in the Dietrich School. "The metal clusters are your joints, and the organic molecules are your linkers. In order to build a highly open structure with lots of empty space, you can increase the linker length or you can increase the size of the joint. We developed chemistry to make large joints, or vertices, and showed that we could link these together to build a material with extraordinarily large pores for this class of materials.

"Essentially, we're like architects. We first make a blueprint for a target material, and we then select our building blocks for construction," added Rosi. "We develop methods for designing structures and controlling the assembly of these structures on a molecule-by- molecule basis."

Rosi and Jihyun An, who graduated with a PhD degree in chemistry from Pitt in 2011 and is lead author of the paper, said this new approach could have an impact on storing large quantities of gas such as carbon dioxide or methane, an important development for alternative energy, or large amounts of drug molecules, which could impact the drug-delivery field. Since joining Pitt five years ago, Rosi has developed a lab that includes students and postdoctoral researchers from various chemistry-related disciplines and focuses on new methods for materials' design and discovery.

The team's research has been supported by Pitt and the American Chemical Society Petroleum Research Fund.

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The above story is reprinted from materials provided by University of Pittsburgh.

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Journal Reference:

Jihyun An, Omar K. Farha, Joseph T. Hupp, Ehmke Pohl, Joanne I. Yeh, Nathaniel L. Rosi. Metal-adeninate vertices for the construction of an exceptionally porous metal-organic framework. Nature Communications, 2012; 3: 604 DOI: 10.1038/ncomms1618

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Researchers discover one of the most porous materials to date

Working with metal-organic frameworks—crystalline compounds comprising metal- cluster vertices linked together by organic molecules to form one-, two-, or three-dimensional porous structures—researchers addressed changing the size of the vertex (the metal cluster) rather than the length of the organic molecule links, which resulted in the largest metal organic framework pore volume reported to date.

"Think of this the way you imagine Tinkertoys®," said Nathaniel Rosi, principal investigator and assistant professor in Pitt's Department of Chemistry in the Dietrich School. "The metal clusters are your joints, and the organic molecules are your linkers. In order to build a highly open structure with lots of empty space, you can increase the linker length or you can increase the size of the joint. We developed chemistry to make large joints, or vertices, and showed that we could link these together to build a material with extraordinarily large pores for this class of materials.

"Essentially, we're like architects. We first make a blueprint for a target material, and we then select our building blocks for construction," added Rosi. "We develop methods for designing structures and controlling the assembly of these structures on a molecule-by- molecule basis."

Rosi and Jihyun An, who graduated with a PhD degree in chemistry from Pitt in 2011 and is lead author of the paper, said this new approach could have an impact on storing large quantities of gas such as carbon dioxide or methane, an important development for alternative energy, or large amounts of drug molecules, which could impact the drug-delivery field. Since joining Pitt five years ago, Rosi has developed a lab that includes students and postdoctoral researchers from various chemistry-related disciplines and focuses on new methods for materials' design and discovery.

Provided by University of Pittsburgh

Porous crystals for natural gas storage

A Northwestern University research team has developed a computational method that can save scientists and engineers valuable time in the discovery process. The new algorithm automatically generates and tests hypothetical metal-organic frameworks (MOFs), rapidly zeroing in on the most promising structures. These MOFs then can be synthesized and tested in the lab.

Using their method, the researchers quickly identified more than 300 different MOFs that are predicted to be better than any known material for methane (natural gas) storage. The researchers then synthesized one of the promising materials and found it beat the U.S. Department of Energy (DOE) natural gas storage target by 10 percent.

There already are 13 million vehicles on the road worldwide today that run on natural gas -- including many buses in the U.S. -- and this number is expected to increase sharply due to recent discoveries of natural gas reserves.

In addition to gas storage and vehicles that burn cleaner fuel, MOFs may lead to better drug-delivery, chemical sensors, carbon capture materials and catalysts. MOF candidates for these applications could be analyzed efficiently using the Northwestern method.

"When our understanding of materials synthesis approaches the point where we are able to make almost any material, the question arises: Which materials should we synthesize?" said Randall Q. Snurr, professor of chemical and biological engineering in the McCormick School of Engineering and Applied Science. Snurr led the research. "This paper presents a powerful method for answering this question for metal-organic frameworks, a new class of highly versatile materials."

The study will be published Nov. 6 by the journal Nature Chemistry. It also will appear as the cover story in the February print issue of the journal.

Christopher E. Wilmer, a graduate student in Snurr's lab and first author of the paper, developed the new algorithm; Omar K. Farha, research associate professor of chemistry in the Weinberg College of Arts and Sciences, and Joseph T. Hupp, professor of chemistry, led the synthesis efforts.

"Currently, researchers choose to create new materials based on their imagining how the atomic structures might look," Wilmer said. "The algorithm greatly accelerates this process by carrying out such 'thought experiments' on supercomputers."

The researchers were able to determine which of the millions of possible MOFs from a given library of 102 chemical building block components were the most promising candidates for natural-gas storage. In just 72 hours, the researchers generated more than 137,000 hypothetical MOF structures. This number is much larger than the total number of MOFs reported to date by all researchers combined (approximately 10,000 MOFs). The Northwestern team then winnowed that number down to the 300 most promising candidates for high-pressure, room-temperature methane storage.

In synthesizing the natural-gas storage MOF that beat the DOE storage target by 10 percent, the research team showed experimentally that the material's actual performance agreed with the predicted properties.

The new algorithm combines the chemical "intuition" that chemists use to imagine novel MOFs with sophisticated molecular simulations to evaluate MOFs for their efficacy in different applications. The algorithm could help remove the bottleneck in the discovery process, the researchers said.

Provided by Northwestern University (news : web)

Full to the brim with hydrogen: Porous form of magnesium borohydride can store hydrogen

Hydrogen could be one of the most important fuels in a new energy economy based on renewable resources. However, no ideal hydrogen storage material has yet been found. A team led by Yaroslav Filinchuk at the Université Catholique de Louvain, Belgium, and Torben R. Jensen at the University of Aarhus in Denmark has now introduced a new highly porous form of magnesium borohydride in the journal Angewandte Chemie. This material can store hydrogen in two ways: chemically bound and physically adsorbed.

The perfect hydrogen storage material must store hydrogen efficiently and securely in a small volume, and should release it on demand. It must be rapidly refillable under mild conditions, while being as light and inexpensive as possible. One approach to this is solid-state storage. In such systems, hydrogen can be chemically bound, as in borohydride compounds, or it can be adsorbed as a molecule into a nanoporous material, as in some metal–organic frameworks.

The researchers have now found a material that can do both. It is a new, highly porous form of magnesium borohydride—the first light-metal hydride that is porous like a metal–organic framework and is capable of storing molecular hydrogen.

Magnesium borohydride (Mg(BH4)2) is one of the most promising materials for chemical hydrogen storage because it releases hydrogen at relatively low temperatures and can hold a high proportion by weight (about 15 %) of hydrogen. Two forms of this compound, ? and ß, were previously known. The researchers have now made a third form, designated the ? form. Its pore volume comprises about 33 % of the structure, and its channels are wide enough to take up and store small gas molecules, such as nitrogen, dichloromethane, and most importantly hydrogen.

Interestingly, under high pressure this material converts into a nested, non-porous framework with a density that is nearly 80 % higher. This makes the ? form the second densest in hydrogen content and more than twice as dense as liquid hydrogen. Furthermore, this conversion results in a 44 % reduction in volume, which is the largest contraction yet observed for a hydride.

“A combination of the chemical (through covalent bonding) and physical (through adsorption in the pores) storage of hydrogen seems to be difficult in practical applications,” explains Filinchuk. “However, this research has a broader impact, as it reveals a new class of hydride-based porous solids for storage and separation of various gases.”

More information: Yaroslav Filinchuk, Porous and Dense Magnesium Borohydride Frameworks: Synthesis, Stability, and Reversible Absorption of Guest Species,

Shining new light on air pollutants using entangled porous frameworks

ScienceDaily (Jan. 26, 2011) — Certain types of pollution monitoring may soon become considerably easier. A group of researchers centered at Kyoto University has shown in a recent Nature Communications paper that a newly-formulated entangled framework of porous crystals (porous coordination polymers, or PCPs) can not only capture a variety of common air pollutants, but that the mixtures then glow in specific, easily-detected colors.

Lead author for the paper was Dr. Yohei Takashima.

Until now, chemical sensors have generally needed to be custom-designed to recognize specific compounds, and a separate transmission mechanism was required in order to "see" that a particular molecule had indeed been successfully captured.

"We have created what amount to be interlocking jungle-gyms, that move relative to each other and are therefore able to capture molecules of varying sizes," explained Dr. Shuhei Furukawa of Kyoto University's Institute for Integrated Cell-Material Sciences (iCeMS).

This naphthalenediimide-based PCP, known as NDI, expands and contracts to confine air-born volatile organic compounds (VOCs) such as benzene, toluene, xylene, anisole, and iodobenzene, which are common pollutants in the lower atmosphere.

"When exposed to ultraviolet light, the NDI-VOC interaction luminesces in an unusually wide range of colors, sufficiently intense to be observed even with the naked eye," elaborated iCeMS Professor and deputy director, Susumu Kitagawa.

These findings, including contributions from Dr. Virginia Martínez Martínez at the Universidad del País Vasco in Bilbao, open the door to the development of a new range of portable, solid-state pollution detectors, and possibly even new types of light sources.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Institute for Integrated Cell-Material Sciences, Kyoto University, via EurekAlert!, a service of AAAS.

Journal Reference:

Yohei Takashima, Virginia Martínez Martínez, Shuhei Furukawa, Mio Kondo, Satoru Shimomura, Hiromitsu Uehara, Masashi Nakahama, Kunihisa Sugimoto, Susumu Kitagawa. Molecular decoding using luminescence from an entangled porous framework. Nature Communications, 2011; 2 (1): 168 DOI: 10.1038/ncomms1170

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