Tag Archives: reticular chemistry

Centuries-old technique for constructing arched stone windows leads to new technique for nanoscale windows

An October 2, 2023 news item on phys.org announces research from Saudi Arabia,

A centuries-old technique for constructing arched stone windows has inspired a new way to form tailored nanoscale windows in porous functional materials called metal-organic frameworks (MOFs).

I very much appreciate the aesthetics of the illustration for the research,

Caption: KAUST researchers have developed a new approach to MOF design that offers multiple benefits to enhance MOF performance. Credit: © 2023 KAUST.

An October 2, 2023 King Abdullah University of Science & Technology (KAUST) press release (also on EurekAlert), which originated the news item, provides more technical details about the research, Note: A link has been removed,

The method uses a molecular version of an architectural arch-forming “centring formwork“ template to direct the formation of MOFs with pore windows of predetermined shape and size.[1]. New MOFs designed and made in this way range from narrow-windowed materials with gas separation potential to larger-windowed structures with potential medical applications due to their excellent oxygen-adsorption capacity.

“One of the most challenging goals in new structure design is the precise control of structure formation,” says Aleksandr Sapianik, a postdoc in the group of Mohamed Eddaoudi, who led the research. For reticular chemistry — the assembly of molecular building blocks into porous crystalline materials such as MOFs — the centering formwork concept might offer that precise control, the team realized.

The starting point of the research was a zeolite-like MOF (ZMOF), which usually features pentagonal windows framed by building blocks called supertetrahedra (ST). “Our goal was to control ST arrangement to change from this well-known topology to one not reported before with these building blocks,” Sapianik says.

The team developed centring structure-directing agents (cSDA) to control ST alignment and form ZMOF windows of new shapes and sizes. One set of cSDAs, designed to tighten the angle between adjoining ST units, created small windows. Another set, designed to expand the angle between ST units, gave larger windows.

“MOF pore size and volume are important parameters that affect their application,” says Marina Barsukova, a postdoc in Eddaoudi’s team. One large-windowed ZMOF the team designed, Fe-sod-ZMOF-320, showed the highest oxygen adsorption capacity of any MOF known. “This property is important in the medical and aerospace industries, where the high capacity would increase oxygen storage in a cylinder, or enable smaller cylinders for easier transport,” Barsukova says. The same ZMOFs also performed well for storage of methane and hydrogen, which are potential fuels. Other ZMOFs in the family with narrow windows showed potential for gas separation of molecular mixtures.

The cSDA concept offers multiple benefits enhancing MOF performance, says Vincent Guillerm, a research scientist in Eddaoudi’s group. “The cSDA partitions big windows into smaller ones, which our preliminary results suggest will be useful for chemical separations,” he says. “It also offers additional internal pore surface, which can help to improve gas storage, and reinforces the MOF framework, which should improve the material’s stability,” he adds.

“The centring approach we have developed is another powerful strategy in the repertoire of reticular chemistry, offering great potential for made-to-order MOFs for applications in energy security and environmental sustainability,” Eddaoudi says.

Here’s a link to and a citation for the paper,

Face-directed assembly of tailored isoreticular MOFs using centring structure-directing agents by Marina Barsukova, Aleksandr Sapianik, Vincent Guillerm, Aleksander Shkurenko, Aslam C. Shaikh, Prakash Parvatkar, Prashant M. Bhatt, Mickaele Bonneau, Abdulhadi Alhaji, Osama Shekhah, Salvador R. G. Balestra, Rocio Semino, Guillaume Maurin & Mohamed Eddaoudi. Nature Synthesis (2023) DOI: https://doi.org/10.1038/s44160-023-00401-8 Published: 02 October 2023

This paper is open access.

Weaving at the nanoscale

A Jan. 21, 2016 news item on ScienceDaily announces a brand new technique,

For the first time, scientists have been able to weave a material at molecular level. The research is led by University of California Berkeley, in cooperation with Stockholm University. …

A Jan. 21, 2016 Stockholm University press release, which originated the news item, provides more information,

Weaving is a well-known way of making fabric, but has until now never been used at the molecular level. Scientists have now been able to weave organic threads into a three-dimensional material, using copper as a template. The new material is a COF, covalent organic framework, and is named COF-505. The copper ions can be removed and added without changing the underlying structure, and at the same time the elasticity can be reversibly changed.

– It almost looks like a molecular version of the Vikings chain-armour. The material is very flexible, says Peter Oleynikov, researcher at the Department of Materials and Environmental Chemistry at Stockholm University.

COF’s are like MOF’s porous three-dimensional crystals with a very large internal surface that can adsorb and store enormous quantities of molecules. A potential application is capture and storage of carbon dioxide, or using COF’s as a catalyst to make useful molecules from carbon dioxide.

Complex structure determined in Stockholm

The research is led by Professor Omar Yaghi at University of California Berkeley. At Stockholm University Professor Osamu Terasaki, PhD Student Yanhang Ma and Researcher Peter Oleynikov have contributed to determine the structure of COF-505 at atomic level from a nano-crystal, using electron crystallography methods.

– It is a difficult, complicated structure and it was very demanding to resolve. We’ve spent lot of time and efforts on the structure solution. Now we know exactly where the copper is and we can also replace the metal. This opens up many possibilities to make other materials, says Yanhang Ma, PhD Student at the Department of Materials and Environmental Chemistry at Stockholm University.

Another of the collaborating institutions, US Department of Energy Lawrence Berkeley National Laboratory issued a Jan. 21, 2016 news release on EurekAlert, providing a different perspective and some additional details,

There are many different ways to make nanomaterials but weaving, the oldest and most enduring method of making fabrics, has not been one of them – until now. An international collaboration led by scientists at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley, has woven the first three-dimensional covalent organic frameworks (COFs) from helical organic threads. The woven COFs display significant advantages in structural flexibility, resiliency and reversibility over previous COFs – materials that are highly prized for their potential to capture and store carbon dioxide then convert it into valuable chemical products.

“Weaving in chemistry has been long sought after and is unknown in biology,” Yaghi says [Omar Yaghi, chemist who holds joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Chemistry Department and is the co-director of the Kavli Energy NanoScience Institute {Kavli-ENSI}]. “However, we have found a way of weaving organic threads that enables us to design and make complex two- and three-dimensional organic extended structures.”

COFs and their cousin materials, metal organic frameworks (MOFs), are porous three-dimensional crystals with extraordinarily large internal surface areas that can absorb and store enormous quantities of targeted molecules. Invented by Yaghi, COFs and MOFs consist of molecules (organics for COFs and metal-organics for MOFs) that are stitched into large and extended netlike frameworks whose structures are held together by strong chemical bonds. Such frameworks show great promise for, among other applications, carbon sequestration.

Through another technique developed by Yaghi, called “reticular chemistry,” these frameworks can also be embedded with catalysts to carry out desired functions: for example, reducing carbon dioxide into carbon monoxide, which serves as a primary building block for a wide range of chemical products including fuels, pharmaceuticals and plastics.

In this latest study, Yaghi and his collaborators used a copper(I) complex as a template for bringing threads of the organic compound “phenanthroline” into a woven pattern to produce an immine-based framework they dubbed COF-505. Through X-ray and electron diffraction characterizations, the researchers discovered that the copper(I) ions can be reversibly removed or restored to COF-505 without changing its woven structure. Demetalation of the COF resulted in a tenfold increase in its elasticity and remetalation restored the COF to its original stiffness.

“That our system can switch between two states of elasticity reversibly by a simple operation, the first such demonstration in an extended chemical structure, means that cycling between these states can be done repeatedly without degrading or altering the structure,” Yaghi says. “Based on these results, it is easy to imagine the creation of molecular cloths that combine unusual resiliency, strength, flexibility and chemical variability in one material.”

Yaghi says that MOFs can also be woven as can all structures based on netlike frameworks. In addition, these woven structures can also be made as nanoparticles or polymers, which means they can be fabricated into thin films and electronic devices.

“Our weaving technique allows long threads of covalently linked molecules to cross at regular intervals,” Yaghi says. “These crossings serve as points of registry, so that the threads have many degrees of freedom to move away from and back to such points without collapsing the overall structure, a boon to making materials with exceptional mechanical properties and dynamics.”

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This research was primarily supported by BASF (Germany) and King Abdulaziz City for Science and Technology (KACST).

It’s unusual that neither Stockholm University not the Lawrence Berkeley National Laboratory list all of the institutions involved. To get a sense of this international collaboration’s size, I’m going to list them,

  • 1Department of Chemistry, University of California, Berkeley, Materials Sciences Division, Lawrence Berkeley National Laboratory, and Kavli Energy NanoSciences Institute, Berkeley, CA 94720, USA.
  • 2Department of Materials and Environmental Chemistry, Stockholm University, SE-10691 Stockholm, Sweden.
  • 3Department of New Architectures in Materials Chemistry, Materials Science Institute of Madrid, Consejo Superior de Investigaciones Científicas, Madrid 28049, Spain.
  • 4Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan.
  • 5NSF Nanoscale Science and Engineering Center (NSEC), University of California at Berkeley, 3112 Etcheverry Hall, Berkeley, CA 94720, USA.
  • 6Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
  • 7King Abdulaziz City of Science and Technology, Post Office Box 6086, Riyadh 11442, Saudi Arabia.
  • 8Material Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
  • 9School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.

Given that some of the money came from a German company, I’m surprised not one German institution was involved.

Here’s a link to and citation for the paper,

Weaving of organic threads into a crystalline covalent organic framework by Yuzhong Liu, Yanhang Ma, Yingbo Zhao, Xixi Sun, Felipe Gándara, Hiroyasu Furukawa, Zheng Liu, Hanyu Zhu, Chenhui Zhu, Kazutomo Suenaga, Peter Oleynikov, Ahmad S. Alshammari, Xiang Zhang, Osamu Terasaki, Omar M. Yaghi. Science  22 Jan 2016: Vol. 351, Issue 6271, pp. 365-369 DOI: 10.1126/science.aad4011

This paper is behind a paywall.