Synthesizing ammonia, the key ingredient in fertilizer, is energy intensive and a significant contributor to greenhouse gas warming of the planet. Chemists designed and synthesized porous materials — metal-organic frameworks, or MOFs — that bind and release ammonia at more moderate pressures and temperatures than the standard Haber-Bosch process for making ammonia. The MOF doesn’t bind to any of the reactants, making capture and release of ammonia less energy intensive and greener.
Researchers have developed a system that can transform plastic waste and greenhouse gases into sustainable fuels and other valuable products — using just the energy from the Sun.
Researchers have invented a groundbreaking new catalyst technology that converts renewable materials like trees and corn to the key chemicals, acrylic acid, and acrylates used in paints, coatings, and superabsorbent polymers.
Dr. Veronica Mengqi Zhang joined Michigan State University (MSU) as the Organic Chemistry Laboratory Coordinator and has been working on implementing and refining the reformed laboratory curriculum towards cooperative learning and green chemistry. As a Green Chemistry Commitment (GCC) signer, MSU has prioritized green chemistry education and knowledge sharing for several years.
In this Q&A, Dr. Zhang shares her story about being part of the GCC community.
BASF plans to substantially increase its use of industrial biotechnology in the coming years as part of a strategy to combat high energy prices, drive down greenhouse gas emissions and environmental impact, and launch products with novel performance, Melanie Maas-Brunner, BASF’s chief technology officer, told journalists at a Nov. 17 briefing.
Does the secret to cleaner energy lie in a common household cleaner?
With its unmistakable smell and astringent nature, ammonia is used to combat household grime, from greasy stovetops to soap-scummed bathroom tiles. Now, a Johns Hopkins chemical and materials engineer thinks it may also hold the key to cleaner, more sustainable energy.
The three-year, $4.2 million project is funded by the U.S. Department of Energy and is part of its $540 million overall initiative aimed at supporting research and developing new technology to reduce carbon emissions and advance clean energy. Ammonia has potential as a liquid storage medium as it does not produce carbon dioxide when burned.
The 2022 Nobel prize in chemistry has been awarded to a trio for developing click chemistry, an environmentally friendly method for rapidly joining molecules to develop cancer treatments, create materials and illuminate the workings of cells.
Carolyn R. Bertozzi from Stanford University in the US, Morten Meldal from the University of Copenhagen in Denmark, and K. Barry Sharpless from Scripps Research, also in the US, will share the 10 million Swedish kronor (£808,554) award “for the development of click chemistry and bioorthogonal chemistry”.
Chemistry made the modern world, from drugs to synthetic materials, batteries to fuels, flat screens to fertilisers. Often these creations have caused environmental and medical problems, two obvious examples are plastic pollution and health problems associated with “forever chemicals”.
So today chemists are acutely aware of the need to consider the environment and ethical impact of their creations. This has driven scientists to carefully consider how to innovate in a green and sustainable way, while creating new compounds and materials to tackle the world’s challenges.
Building new molecules is hard. It often requires a multitude of sequential individual reactions, each one hampered by side reactions that reduce the purity of the sample. This increases the number and complexity of any further reaction steps, while producing harmful waste that needs careful and expensive disposal.
A solution to this problem was conceived by Barry Sharpless at the turn of the millennium. He coined the term “click chemistry”. It’s a concept in which molecules are simply, quickly, reliably and repeatedly joined together in much the same way as a seatbelt clips into its buckle. The idea was the chemical equivalent of the flat-pack wardrobe, while everyone else was building furniture from scratch.
Sharpless also stipulated that click reactions should be carried out in water, instead of harmful solvents commonly used by synthetic chemists to dissolve their reactants. This was a fabulous concept as it would allow quick, reliable and environmentally friendly molecule creation for new products.
But the challenge was making the chemical belts and buckles. The first example of click chemistry was devised by Morten Meldal in 2008 while working on a well studied reaction between two chemicals; azides and alkynes. These are frequently used to join chemicals together, however they normally produce a mucky mess of reactants. But when copper was added to the mix, the reaction produced one, incredibly stable product.
Click Chemistry. The Nobel Prize in Chemistry 2022. NobelPrize.org. Nobel Prize Outreach AB 2022. Wed. 5 Oct 2022.
The reaction became extremely popular as it allowed chemists to rapidly change the functionality of a chemical or material. A fibre could have the chemical buckle attached during manufacturing and later extra functionality could be added. The reaction made it easy to click in anti-bacterials, UV protective compounds, or substances that conduct electricity.
In 2004, Carolyn Bertozzi took click chemistry a step further by applying the principle to a biological problem. A common technique for studying the behaviour of molecules in a cell is to attach a fluorescent, glowing label which is clearly visible under a microscope. However, connecting the label to exactly the right part of the cell is tricky.
Bertozzi realised that click chemistry offered a solution. Unfortunately copper, used in Meldal’s original click chemistry method, is toxic to living things so it could not be directly applied to Bertozzi’s problem. Instead she came up with a technique that works without the copper. She attached the azide “buckle” to a sugar molecule. This gets absorbed to the cell, incorporated, and presented on the cell’s surface. A modified alkalyne (the clip) connected to a green fluoresent molecule then gets added to the cell where it clicks to the azide sugar. Then the cell can be easily tracked under a microscope.
Bioorthogonal chemistry illuminates the cell. CC BY-NC
Bertozzi’s technique has led to insights into how tumour cells evade our immune systems and helped develop methods to track cancerous cells. It has also helped to target radiotherapies directly to cancer cells, reducing the harm to nearby healthy cells.
Click chemistry is elegant and efficient. It has allowed chemicals to be joined together almost as smoothly as clicking together two blocks of Lego. Its simplicity has seen its uses spread rapidly through the field of chemistry with applications in pharmaceuticals, DNA sequencing and materials with added functionality (such as magnetic and electrical). There is little doubt the applications of the technique will expand and be applied to the world’s most pressing issues.
The 2022 Nobel Prize in chemistry was awarded to scientists Carolyn R. Bertozzi, Morten Meldal and K. Barry Sharpless for their development of click chemistry and bioorthogonal chemistry.
These techniques have been used in a number of sectors, including delivering treatments that can kill cancer cells without perturbing healthy cells as well as sustainably and quickly producing large amounts of polymers to build materials. One click chemistry-based drug is currently undergoing phase 2 clinical trials. Bertozzi is a scientific adviser of the company developing the drug.
We asked chemistry Ph.D. candidate Heyang (Peter) Zhang of the Lin Lab at the University at Buffalo to talk about how these techniques figure in his own research and how they have transformed his field and other industries.
1. How does click and bioorthogonal chemistry work?
Click chemistry, as the name suggests, is a way of building molecules like snapping Lego blocks together. It takes two molecules to click, so researchers refer to each one as click partners.
K. Barry Sharpless and Morten Meldal independently discovered that azide, a high-energy molecule with three nitrogens bonded together, and alkyne, a relatively inert and naturally rare molecule with two carbons triple-bonded together, are great click partners in the presence of a copper catalyst. They found that the copper catalyst can bring the two pieces together in an optimal arrangement that snaps them together. Prior to this technique, researchers did not have a way to quickly and precisely make new molecules under accessible conditions, like using water as a solvent at room temperature.
By combining an azide with a cyclooctyne, bioorthogonal chemistry allows researchers to join molecules quickly together without disturbing the rest of the cell. Cliu89/Wikimedia Commons
Chemical biologists quickly realized that click reactions can be a fantastic way to probe living systems like cells because they produce little to no toxic byproducts and can happen quickly. However, the copper catalyst is itself toxic to living systems.
Carolyn Bertozzi devised a workaround for this issue by removing the copper catalyst from the reaction. She did this by placing the alkyne into a ring structure, which drives the reaction forward using the ring strain produced from molecules forced into a cyclical shape. These bioorthogonal reactions, or reactions that happen “parallel” to the chemical environment of the cell, can occur in cells without perturbing their normal chemistry.
2. How do you use this chemistry in your work?
In an interview, Carolyn Bertozzi stated that the next steps for bioorthogonal chemistry are to find new reactions and applications for it. Our lab’s research focuses exactly on that.
My colleagues and I apply this technique to track molecules we are interested in as they naturally behave in a cell. In a living cell, we were able to add a probe to a receptor that plays a role in a number of cellular processes.
Carolyn Bertozzi is one of the winners of the 2022 Nobel Prize in chemistry.
To find new reactions, our lab has spent the last 15 years to push how fast bioorthogonal reactions can run. Speed is important because many molecules in living organisms are present in low concentrations, and using too much of the chemicals required for the reaction can be toxic for the cell. The faster the reaction, the fewer the unwanted side reactions.
We pioneered another way to achieve click and bioorthogonal reactions with even faster speed. Instead of using an azide and an alkyne like the Nobel Prize winners did originally, we used two other molecules that join together when a light is shined on them. With this technique, we are able to add molecules to the surface of a live cell in as little as 15 seconds. We can then observe how a particular structure on a cell functions in its natural environment, or detect how it changes when exposing it to drugs or other substances. Researchers can then more easily test how cells react to potential treatments.
Currently, we are working to develop a new method of triggering these reactions without light. We are actively working on using bioorthogonal chemistry to improve PET imaging to screen and monitor tumors.
3. Why are these techniques so important to your field?
Prior to click and bioorthogonal chemistry, there was no way of visualizing molecules in living cells in their natural state.
As an analogy, imagine you needed to find a specific dollar bill with the serial number 01234567. That would be a pretty daunting task. It would require you to go through every dollar you can get your hands on and verify whether the serial number is the one you are looking for.
Tracking molecules in our body is just as hard, if not more. Because biological environments are so complex, it was previously impossible to add a probe to just the molecule of interest without accidentally tagging something else, or worse, altering the normal chemistry of the cell. With bioorthogonal reactions, however, researchers can essentially add a GPS tracker to the molecule without affecting the rest of the cell.
An organic chemist by training, Anastas maintains an active research program at Yale University that spans chemistry, chemical engineering, environmental sciences, epidemiology, and related disciplines. He also codirects the Yale Center for Green Chemistry and Green Engineering.
Academia is only part of his story. He spent almost 20 years in government service, culminating in a 3-year appointment by former president Barack Obama to lead R&D at the US Environmental Protection Agency. He’s active in the business of chemistry, including holding founder, adviser, and board roles in start-ups such as the personal care ingredient maker P2 Science and the carbon dioxide-to-chemicals firm Air Company. He also has consulting contracts with Fortune 100 firms. As an advocate, he’s championed federal legislation encouraging the adoption of green chemistry principles in government-funded research.
On Sept. 1, Anastas and frequent collaborator John Warner received the August Wilhelm von Hofmann Commemorative Medal from Germany’s chemical society in recognition of the lasting impact of the pair’s 1998 book Green Chemistry: Theory and Practice, which laid out the 12 principles of green chemistry, and their subsequent work fleshing out those concepts. C&EN interviewed Anastas via video call in mid-July. This conversation was edited for length and clarity.
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