Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

NewcCompetition for MOFs: Scientists make stronger COFs

02.08.2018

Berkeley Lab researchers find a way to better 'weld' covalent organic frameworks together

Hollow molecular structures known as COFs (covalent organic frameworks), which could serve as selective filters or containers for other substances and have many other potential uses, also tend to suffer from an inherent problem: It's difficult to keep a network of COFs connected in harsh chemical environments.


At left is the simulated 3D molecular structure of a covalent organic framework, and at right is a modified framework. The yellow spheres in the structure on the left indicate a pore diameter of 2.9 nanometers, and the cyan spheres in the structure on the right indicate a pore diameter of 2.6 nanometers.

Credit: Berkeley Lab


These high-resolution transmission electron microscopy images, produced at Berkeley Lab's Molecular Foundry, show a sheet of covalent organic frameworks (COFs) at the nanoscale (top row), and a sheet of chemically modified COFs (bottom row).

Credit: Berkeley Lab

The conventional chemistry for linking building blocks into 2D COF sheets or 3D COF frameworks is reversible. This reversibility makes the connections within COFs weak and unstable in some chemical environments, limiting the practical applications of these COF materials.

Now, a team at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has used a chemical process discovered decades ago to make the linkages between COFs much more sturdy, and to give the COFs new characteristics that could expand their applications.

"It's like a 'weaving' and welding approach," said Yi Liu, a staff scientist at Berkeley Lab's Molecular Foundry. Liu led a team that found out how to strengthen the weakest links binding COFs.

This one simple chemical approach targets a chemical reaction to the area of these weak links, forming resilient bonds that were shown to hold up - like a strong weld - to harsh chemical environments during experiments.

The team's findings are detailed in a study, reported Tuesday in the journal Nature Communications, that details how the technique works.

"Here we show that these bonds are exceptionally stable to a variety of chemicals. We've tried harsh conditions and it still sustains these bonds," Liu said. "This beats everything reported in the literature."

The chemical transformation, he noted, makes the bonds between COFs more useful by changing their electronic and optical (light-based) properties, for example. "They can transfer electrons more easily after the reaction," he said, so that 2D layers of these strongly bound COFs behave more like graphene, another exotic 2D material that exhibits special electronic and optical properties.

Xinle Li, a postdoctoral fellow at the Molecular Foundry and the study's lead author, said, "We gave that reaction process, first reported in the 1960s, a new life. We applied it to COFs for the first time."

COFs have been heavily studied because they are highly tunable and can be composed entirely of light elements like carbon, hydrogen, nitrogen, and oxygen - unlike structures known as MOFs (metal-organic frameworks) that contain heavier elements. Scientists can make COFs with different pore sizes that can impact their function, changing what can pass through them or what can be contained within these pores.

This could make the COF-based materials useful in systems that filter unwanted chemicals from water, for example, reduce carbon dioxide into other value-added chemical forms, or serve as highly efficient facilitators for other types of chemical processes.

An important aspect of the study was the use of advanced imaging techniques, such as high-resolution transmission electron microscopy (HRTEM) at the Molecular Foundry to see the structure of the bound COFs, Liu and Li said.

The researchers said the images obtained, which clearly show the honeycomb-like lattice of 2D COFs, are among the best images yet of COFs, confirming the chemical changes in the COFs down to a fraction of a nanometer (a nanometer is 1 billionth of a meter).

"Before and after the reaction, the pore size changes by about 0.3 nanometer, Liu said. "You can see these differences before and after the reaction."

To carry out the chemical modification reaction, the researchers placed the COFs in a liquid solution that was heated to about 230 degrees Fahrenheit, and then stirred it up.

Researchers said it should be possible to scale up the amount of the COF-based materials, and the team has already experimented with using COF sheets with other material layers to customize the function of the combined material.

The team plans to test how to better automate the production of these COF materials, and will also pursue ways to make the reaction process more efficient. The team will explore theories to help understand and improve upon the COF-altering chemistry.

"We want to make this chemical modification process even faster and better," Li said. "We hope we can make the reaction conditions milder, and further increase the chemical stability and functionality of COFs."

The team's work is one of the first published efforts of a new program at the Molecular Foundry aiming to advance "combinatorial nanoscience" that is focused on using high throughput processes, in combination with theory and imaging technology, to create and study nanostructures that are components in new materials with enhanced properties.

###

The Molecular Foundry is a DOE Office of Science User Facility.

The study is co-authored by other Molecular Foundry researchers, and also had participation from Molecular Foundry users from South China Normal University and Zhejiang University in China. This work was supported by the U.S. Department of Energy's Office of Basic Energy Sciences and the National Nature Science Foundation of China.

Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel Prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit http://www.lbl.gov.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov.

Media Contact

Glenn Roberts Jr.
geroberts@lbl.gov
510-486-5582

 @BerkeleyLab

http://www.lbl.gov 

Glenn Roberts Jr. | EurekAlert!
Further information:
https://newscenter.lbl.gov/2018/08/01/new-competition-for-mofs-scientists-make-stronger-cofs/
http://dx.doi.org/10.1038/s41467-018-05462-4

Further reports about: COFs Molecular bonds chemical modification covalent organic frameworks

More articles from Materials Sciences:

nachricht A new paradigm of material identification based on graph theory
17.06.2019 | Science China Press

nachricht Electron beam strengthens recyclable nanocomposite
17.06.2019 | Kanazawa University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The hidden structure of the periodic system

The well-known representation of chemical elements is just one example of how objects can be arranged and classified

The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...

Im Focus: MPSD team discovers light-induced ferroelectricity in strontium titanate

Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.

Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...

Im Focus: Determining the Earth’s gravity field more accurately than ever before

Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.

The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...

Im Focus: Tube anemone has the largest animal mitochondrial genome ever sequenced

Discovery by Brazilian and US researchers could change the classification of two species, which appear more akin to jellyfish than was thought.

The tube anemone Isarachnanthus nocturnus is only 15 cm long but has the largest mitochondrial genome of any animal sequenced to date, with 80,923 base pairs....

Im Focus: Tiny light box opens new doors into the nanoworld

Researchers at Chalmers University of Technology, Sweden, have discovered a completely new way of capturing, amplifying and linking light to matter at the nanolevel. Using a tiny box, built from stacked atomically thin material, they have succeeded in creating a type of feedback loop in which light and matter become one. The discovery, which was recently published in Nature Nanotechnology, opens up new possibilities in the world of nanophotonics.

Photonics is concerned with various means of using light. Fibre-optic communication is an example of photonics, as is the technology behind photodetectors and...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

 
Latest News

Novel communications architecture for future ultra-high speed wireless networks

17.06.2019 | Information Technology

Climate Change in West Africa

17.06.2019 | Earth Sciences

Robotic fish to replace animal testing

17.06.2019 | Ecology, The Environment and Conservation

VideoLinks
Science & Research
Overview of more VideoLinks >>>