���Ҵ�ý�ƽ������

Shining new light on an old problem: Breaking down ‘Forever Chemicals’ and building the next generation of materials

DOI:

Using a new catalyst and visible light, researchers have developed a chemical “scalpel” to degrade persistent pollutants and enable new, more precise chemical reactions.��

The global challenge of “forever chemicals” has made the headlines for years. The carbon-fluorine (C–F) bond is one of the strongest in all of chemistry. For decades the sheer strength of the C–F bond has been a blessing and a curse. This incredible strength is what makes “forever chemicals”, like PFAS, so stable and useful in everything from non-stick pans to waterproof clothing but is also the reason that they are nearly impossible to break down. This has been a major contributor to the growing plastic waste crisis, and a key reasons for these compounds to be now known as one of the hardest pollutants to remove from the environment. A recent collaborative study, including RASEI Fellow Niels Damrauer, has a new solution for this problem. Development of a new catalyst that acts like a chemical scalpel, using blue light to precisely sever this famously inert bond. This approach not only offers a new way to degrade these persistent pollutants but also opens the door to using what were previously considered unreactive fluorinated molecules as building blocks for new chemical transformations and products.

This study is an illustrative example of a modern, collaborative approach to chemical innovation, as part of the NSF funded Center for Sustainable Photoredox Catalysis (SuPRCat). The research team came at the problem from two different angles: computational modeling and hands-on experimentation. The computational chemists first used powerful simulations to design and predict the behavior of a new organic catalyst. This helped them understand exactly how the catalyst could use low-energy, visible blue light to act as our "chemical scalpel," targeting and breaking the C–F bonds without the need for intense heat.

With this knowledge, the experimental chemists then created the catalyst in the lab. They showed that it could precisely snip the C-F bonds in a variety of molecules, demonstrating it was capable of both degrading persistent pollutants like PFAS and building new chemical structures that were previously difficult to construct.

The success of this research with a simple, abundant energy source like visible light shows that chemical reactions don’t have to be energy intensive. This research describes the power of precise, light-driven chemistry. By designing a catalyst that can target and activate some of the toughest bonds in chemistry, this team has not only revealed a potential path forward for degrading PFAS, but also demonstrated a new tool for chemists to build molecules in a cleaner and more energy efficient way.

A Chemical Blueprint for Turning Sunlight and Carbon Dioxide into Fuel

DOI:

Combining computational design and experimental research, scientists have engineered a well-aligned connection between two materials, creating a more efficient pathway for clean energy.��

The search to create carbon-neutral fuels from sunlight and carbon dioxide (CO₂) is one of the most exciting frontiers in sustainable energy. However, it is not enough to simply find a catalyst that can do the job, the real challenge lies in designing a system where all the components work in harmony. Imagine having two brilliant devices that are designed to work together, but they just can’t quite “talk” to each other. One is an incredible light sensitive material that captures sunlight, and the other is a special catalyst that can turn CO₂ into fuel. Previous research has found that when you bring these two components together their electronic energies were mismatched, causing poor ‘communication’ between the components, leading to the overall system being inefficient. Research led by��RASEI Fellow Nate Neale uses a combination of advanced computational modeling and sophisticated experimentation to engineer an aligned electronic “bridge” to better connect the two materials, revealing a more efficient communication pathway, and hence a more effective overall system.

To solve the energy mismatch between the components the team adopted a feedback loop between computational modeling and experimentation. Powerful computational tools enabled the design of a range of potential linking molecules to explore how they would influence the electronic coupling between the silicon nanocrystal (the solar panel) and the catalyst. This approach acted as a “chemical blueprint”, allowing them to predict which design would create the most well-aligned connection. The team then took these findings to the lab and synthesized the most promising candidates and tested their real-world performance, comparing them to the properties predicted by the models. The results confirmed the predications and demonstrated that a specific, directly bonded molecular bridge was the most effective design.

This work describes a foundational step in the search for fuels synthesized by light. By developing an approach for the fundamental challenge of aligning a solar collector and a CO₂ catalyst, the team has provided a critical design guideline for building more efficient and powerful devices in the future.��

��

Supercharging Chemistry: A jump forward in light-driven chemistry

DOI:

New collaborative research involving RASEI Fellow Niels Damrauer, addresses one of the ‘house of cards’ problems sometimes critical in photoredox catalysis.

Think about how you build a house of cards, every time you add a new card, there is a chance the whole thing will fall apart. This is a challenge often faced by chemists when they are trying to put together the components needed for a light-driven reaction. While this type of chemistry has huge potential in making the chemistry cleaner and more efficient, one of the features that can cause the whole thing to fall apart is a phenomenon called back electron transfer, where the desired chemical reaction is reversed, wasting energy and limiting the kinds of reaction that can be performed.

This collaborative team that includes RASEI Fellow Niels Damrauer from ���Ҵ�ý�ƽ������ and the groups of Garret Miyake and Robert Paton from Colorado State University in Fort Collins, has developed a new catalyst system that overcomes this fundamental obstacle. Published in a recent issue of Science, this work introduces a ‘super-reducing’ organic photoredox catalyst that, through preventing this backward reaction, opens the door to powerful new redox chemistries.

To better understand this discovery it is useful to think of the process like filling a bucket with water. In typical photoredox reactions, the bucket has a leak. As water is poured into the bucket (adding energy from light), some of it immediately drains out. This ‘leak’ is back electron transfer (BET), and it is especially problematic for complex and difficult reactions that require a lot of energy – it is like trying to fill a very leaky bucket with a very slow faucet.

The research collaboration, part of the National Science Foundation (NSF) funded Center for Chemical Innovation (CCI) Center for Sustainable Photoredox Catalysis (SuPRCat) took inspiration from nature to develop a solution for this problem. In photosynthesis plants use a process called proton-coupled electron transfer (PCET) to efficiently capture and store energy from sunlight, preventing energy loss. The team used a combination of sophisticated computational modeling and experimental investigation to design a catalyst that incorporates a similar mechanism. When the catalyst is energized by light it simultaneously transfers an electron to the target molecule and releases a proton (a hydrogen atom without its electron). This prevents the reaction from going backwards. This small change has a huge impact on how the reaction proceeds, it is essentially like patching the leak in the bucket as you pour the water in, ensuring that all the energy is used for the desired reaction.

As is often the case with research, the path to this discovery was not a straight line. The investigations initially focused on changing an existing catalyst framework. During these experiments they noticed that one of the new catalysts (PC40Me) was unexpectedly effective. The reduction of benzene is known to be a difficult transformation, but reactions catalyzed with PC40Me were possible. They found that under the reaction conditions PC40Me was transforming into a new chemical structure, and it was this new system that was efficient for the historically difficult reduction of benzene. Armed with this knowledge the team built new catalyst designs around the new structure, creating a more efficient catalyst (named PC8). PC8 is not only a ‘super reducer’ capable of reducing a broad range of aromatic compounds under mild conditions, it also proved to be extremely robust.

The key features of this work lies in its potential to be a new tool in how we design and build everything from pharmaceuticals to plastics. By providing a way to perform these difficult reduction reactions more efficiently and sustainably, this catalyst system has the potential to reduce waste and energy consumption. By opening the door to a transformation that has typically been thought of as difficult and un-efficient, it could act as an enabling technology in the synthesis of new classes of molecules that were previously out of reach.

This work highlights the power of collaboration. The combination of different tools and approaches that were required to complete this work would have been prohibitive for a single research group. By combining expertise the team were able to unravel this complex chemical puzzle, not only demonstrating a new transformation, but providing some design rules that can be used by future photocatalysis practitioners in reducing BET.��

Finding the On switch for more efficient light-driven chemistry

DOI:

Collaboration led by RASEI members Obadiah Reid and Garry Rumbles solves a long-standing puzzle in important organic chemical transformation.

In the world of organic chemistry, making new molecules, the building blocks for everything from advanced electronic materials to pharmaceuticals, is a bit like being a chef. Chemists are always looking to improve the recipe, to make it faster, cheaper, more efficient, and produce less waste. In recent years one of the most exciting new ‘cooking techniques’ is nickel photocatalysis, which uses abundant, low-cost nickel and the power of light to enable chemists to build complex molecules under mild conditions.

This technique has emerged as something of a game-changer in building molecules, but it comes with a significant puzzle. The nickel catalyst, as it is normally added to a reaction, is in a dormant state (called a ‘pre-catalyst’). To get the reaction moving, the catalyst needs to be ‘woken up’. For years, scientists were not sure what the wake-up call was. The activation from pre-catalyst to the functioning catalyst was something of a black box, with numerous theories for what was happening. This led to the assumption that each reaction was unique, and each reaction required its own individual and complicated startup sequence. This has often required a lot of work to find the right ‘On switch’.

This collaborative study, led by RASEI researchers Obadiah Reid and Garry Rumbles at the National Renewable Energy Laboratory (NREL), brings together expertise from the SLAC National Accelerator Laboratory, Brookhaven National Laboratory, Argonne National Laboratory and Northeastern University. Together, the scientists have identified key features of the transformation from pre-catalyst to active catalyst. In the report, just published in Nature Communications, the team shows that there is a universal ‘On switch’ to start these powerful reactions, and the key to this transformation is light.

Imagine a high-tech machine delivered in a locked crate. You know that once you get it out and get it running, it can do amazing things, but you don’t have the key. For years, chemists were essentially trying to pick the lock in different ways every time they wanted to use it. This study describes a universal key for getting the crate open.

It was found that light, either directly, or transferred from another light-absorbing molecule, provide a jolt of energy that breaks a bond in the nickel pre-catalyst structure. This process, which is called photolysis, activates the nickel complex, getting it ready to do the chemistry. This initial step is something that has previously been proposed but never fully proven.

The team brought together a sophisticated array of tools to effectively investigate this mechanism, including incredibly fast laser systems that can watch chemical changes happen in fractions of a second. This allowed them to witness the ‘unlocking’ process in real-time and identify the exact sequence of events. They observed that after the initial light-induced bond breaking, the catalyst can then interact with molecules in the surrounding solvent, forming a temporary ‘reservoir’ that holds the catalyst in a state ready for the main reaction.

Building this body of evidence and developing these findings required a significant team effort, bringing together scientists from across the country, from multiple national labs and universities. RASEI Scientists at ���Ҵ�ý�ƽ������ and NREL used advanced spectroscopy to track the catalyst’s behavior, while researchers at SLAC used high-powered X-rays to confirm changes in the structure of the nickel complex. This combination of knowledge and experience with cutting-edge instrumentation was essential in providing a complete understanding of these reactions begin.

Development of unified explanation for how one of the most important tools in an organic chemist’s toolbox is activated has important implications. Understanding this fundamental activation step allows chemists to move from guessing to designing. Not only does this support improvement in the activation of existing reactions, it also provides opportunities to design new transformations, all of which will streamline the manufacture of chemical commodities, such as pharmaceuticals and materials.

Scientists move microscopic solar chemical factories out of water to unlock new transformations

DOI:

Four RASEI Fellows work together to expand the potential applications of nanoparticle photocatalysts

We all understand the power of the sun. We feel it on a hot summer’s day, we see it harnessed in solar panels that power our homes and cities. Chemical photocatalysis develops approaches to shrink that ability to harness this energy down to a molecular scale, and uses this energy to power chemical reaction, to power the building of important organic molecules, the foundations of pharmaceuticals, materials, and clean fuels.

One of the technologies used to harness light on the molecular level are a class of particles called organic nanoparticles (oNPs). Think of them as tiny, solar-powered factories, expertly designed to capture light and use its energy to drive chemical reactions. The oNPs are made from readily available earth-abundant materials, offering a cheap, clean, and sustainable alternative to a range of more traditional chemical reactions, which can often rely on rare, expensive metals that are hard to get hold of and can produce significant waste.

However, the oNPs, for all their potential as chemical factories, do have one significant limitation, they can only be built and operated in water. This is a fundamental roadblock. While water is essential for life, it is often a very poor environment for performing chemical reactions and can be very detrimental for the complex and delicate sequence of chemical transformations required for producing valuable products. The full power of these nano-factories was, quite literally, stuck in the water.

To understand this challenge, imagine that you have designed the world’s most efficient and powerful engine. It is a true engineering breakthrough, but it comes with a major catch, it can only run while completely submerged in the ocean. This is fine if you want to get around in a submarine, or a boat, but you can’t put it into a car, or a plane, or a generator on land, where you need it most. The potential of this new innovation is trapped, unable to be used for countless valuable applications.

That is similar to the situation faced by the researchers, led by RASEI Fellows Stephen Barlow, Seth Marder, Obadiah Reid and Garry Rumbles. The oNPs were confined to water-based reaction media, in order to realize their full potential the team needed to find a way to move these delicate ‘nano-factories’ from water to the ‘dry-land’ of other chemical environments, known as non-aqueous solvents, without the oNPs collapsing or breaking down.

This study describes a solution that the team developed. They devised a multi-step process to gently coax the oNPs out of their native water environment and prepare them to operate in different chemical solvents.

The process they developed is analogous to making salad dressing in the kitchen. It begins by mixing the water containing the nanoparticles with an oily substance (in this study oleic acid) and shaking it. This creates an emulsion, where tiny droplets of water are suspended in the oil, much like a vinaigrette. During this process the oNPs leave the water and move into the oil, which wraps around them like a protective coating. Finally the water is gently remove, leaving the oNPs safely suspended in their new oily environment. The protective layer formed around them allows them to be seamlessly transferred to a range of new non-aqueous solvents, ready to get to work.

A key part of this study was demonstrating that the oNP ‘factories’ were still functional after their transfer to new solvent systems. Using a suite of tools the team were able to confirm that the transferred oNPs could still absorb light and perform the chemical reactions.

With these findings the potential of the oNPs can be explored and expanded. It reveals new opportunities, not only in putting together organic molecules, but also in the synthesis of clean fuels, such as hydrogen.����