Ammonia plays an indispensable role in agriculture and industry, underpinning the manufacture of fertilizers critical to global food security. However, the Haber–Bosch process, which has been the cornerstone of industrial ammonia production for over a century, demands high temperatures and pressures, consuming vast amounts of fossil fuels and releasing copious greenhouse gases. The urgency to find cleaner, less energy-intensive methods has directed scientific attention toward alternative catalytic mechanisms, and the current study harnesses the transformative power of light to this end.

At the heart of this research lies the use of AuRu alloy nanoparticles designed with tunable compositions to optimize their catalytic efficacy. The unique plasmonic properties of gold facilitate intense light absorption and concentration, effectively channeling energy to the ruthenium sites where nitrogen activation occurs. This synergy enables the catalytic assembly to operate under much milder conditions than those required by conventional thermal activation, thus drastically lowering the energy input.

The synthesis rates achieved by these plasmonic AuRu catalysts reach approximately 60 micromoles of ammonia per gram of catalyst bed per hour. While modest compared to industrial scales, this rate represents a significant breakthrough given the benign reaction conditions: ambient temperature and atmospheric pressure. This development could potentially herald a future where ammonia production is decentralized and powered by renewable energy sources, dramatically reducing the carbon footprint of fertilizer manufacture.

In situ infrared spectroscopy was employed to probe the mechanistic underpinnings of this light-driven process. The spectroscopic data revealed that when illuminated, the AuRu catalysts accelerate hydrogenation steps of nitrogen-containing intermediates more effectively than under purely thermal conditions. This crucial observation underscores the distinctive pathways enabled by photo-excited electrons, differing fundamentally from the high-temperature pathways that dominate traditional Haber–Bosch catalysis.

Delving deeper, computational modeling illuminated the atomic-scale processes facilitated by plasmonic excitation. Contrary to the conventional wisdom that nitrogen activation requires cleavage of the robust N≡N triple bond prior to hydrogenation, the model suggests a more associative mechanism. Here, photo-excited electrons selectively activate nitrogen intermediates through successive hydrogenation steps without immediate nitrogen-nitrogen bond breaking. This pathway is reminiscent of the biological nitrogen fixation employed by nitrogenase enzymes in nature, offering a biomimetic pathway suited for synthetic catalytic systems.

A remarkable synergy emerges between light and molecular hydrogen, which together surmount the formidable energy barrier associated with nitrogen activation. Neither light nor hydrogen alone suffices to initiate ammonia synthesis under ambient conditions, highlighting the necessity of this collaborative dynamic. Such a tandem mechanism exemplifies how plasmonic photochemistry can unlock reaction pathways that circumvent traditional thermodynamic constraints, opening new frontiers in catalytic design.

The AuRu bimetallic catalyst platform also facilitates efficient desorption of nitrogen species, ensuring that reaction intermediates do not poison the catalytic surface – a common bottleneck in ammonia synthesis. This enhanced desorption capability contributes to sustained catalytic activity and improved turnover rates, signaling the practicality of this approach for longer-term operations.

Importantly, the utilization of visible light as an energy input source aligns with broader sustainability goals. Given the extensive availability of sunlight and advances in photonic materials, this discovery paves the way for ammonia synthesis driven by renewable energy. Consequently, distributed and decentralized ammonia production facilities could become a viable alternative to today’s centralized Haber–Bosch plants, thereby reducing transportation and infrastructure energy costs.

The implications of this work transcend ammonia synthesis alone, positioning plasmonic catalysis as a versatile tool in the broader landscape of chemical manufacturing. By demonstrating that light-mediated processes can facilitate challenging chemical transformations at mild conditions, this research renews interest in solar-to-chemical energy conversion technologies. Such technologies hold promise not only for fertilizers but also for a wide array of chemicals traditionally reliant on intensive thermal processes.

The marriage of experimental observation with advanced computational insight is a particular strength of this study, presenting a compelling narrative from macroscopic catalytic performance down to electronic dynamics at the nanoscale. This multidisciplinary approach exemplifies how complex energy landscapes in catalysis can be navigated with precision, enabling rational design of next-generation catalysts tailored for solar-driven chemistry.

Looking forward, further work is anticipated to optimize the catalyst composition and nanostructure to enhance ammonia production rates and robustness. Efforts to couple these plasmonic systems with light-harvesting devices or to integrate them in modular reactors powered by natural sunlight will be critical steps toward scalable implementation. Additionally, expanding the principles demonstrated here to other difficult chemical conversions could revolutionize the chemical industry’s sustainability footprint.

In summary, this pioneering study from Yuan and colleagues heralds a paradigm shift in ammonia synthesis by harnessing plasmonic light concentration and photochemical hydrogenation on AuRu catalysts. Operating at ambient conditions and using visible light, the process offers a sustainable and energy-efficient alternative to the century-old Haber–Bosch method. Beyond its immediate environmental benefits, this advancement spotlights the transformative potential of plasmonic catalysis in building a greener chemical future, inspiring new research at the intersection of materials science, photonics, and catalysis.

Given the monumental challenge of meeting global fertilizer demand while combating climate change, innovations like this could not be timelier. By mimicking nature’s enzymatic finesse and reimagining catalysis through light-driven pathways, the researchers have opened a promising avenue toward decarbonizing a vital industrial process. As scientific and engineering communities rally around such breakthroughs, the prospect of sustainable ammonia production inches closer from visionary concept to tangible reality.

Subject of Research:
Atmospheric-pressure ammonia synthesis using plasmonic gold-ruthenium catalysts activated by visible light.

Article Title:
Atmospheric-pressure ammonia synthesis on AuRu catalysts enabled by plasmon-controlled hydrogenation and nitrogen-species desorption.

Article References:
Yuan, L., Bourgeois, B.B., Begin, E. et al. Atmospheric-pressure ammonia synthesis on AuRu catalysts enabled by plasmon-controlled hydrogenation and nitrogen-species desorption. Nat Energy (2025). https://doi.org/10.1038/s41560-025-01911-9

Image Credits:
AI Generated

DOI:
https://doi.org/10.1038/s41560-025-01911-9

The demand for specialized polymeric materials continues to accelerate across diverse sectors, from electronics to energy storage. Traditional polymer synthesis methods, while effective, often lack flexibility and environmental compatibility when tailoring polymers with complex functional groups. Postfunctionalization—a strategy that modifies pre-formed polymer backbones by introducing new moieties—has emerged as a promising route to circumvent these challenges. Unlike conventional techniques that rely heavily on radical intermediates, limiting the scope of feasible chemical modifications, the method developed at the Institute of Science Tokyo pioneeringly introduces a radical–polar crossover mechanism, broadening the chemical landscape for polymer modification.

At the heart of this advancement lies an organophotoredox catalyst, specifically 12-phenyl-12H-benzo[b]phenothiazine (Ph-benzoPTZ), which mediates the transformation under blue LED light irradiation. The process initiates with the formation of an electron donor–acceptor complex between the catalyst and polymer-bound phthalimide ester groups. Upon photoexcitation, electron transfer disrupts the phthalimide ester, releasing carbon dioxide and generating carbon-centered radicals along the polymer backbone. This pivotal step is followed by a secondary electron transfer, transforming these radicals into carbocation equivalents—highly reactive positively charged intermediates rarely accessible in polymer postfunctionalization.

These carbocation species exhibit remarkable reactivity toward trialkyl phosphites, serving as nucleophiles to introduce phosphonate ester functionalities directly onto the polymer chain. The incorporation of phosphonate groups is particularly significant due to their inherent chemical robustness and ability to impart flame retardancy and thermal responsiveness. Importantly, the process accommodates a range of trialkyl phosphites, including those bearing chloro and trifluoromethyl substituents, underscoring the method’s versatility and potential for tuning polymer properties via tailored functionalization.

One of the notable achievements of this technique is its success in modifying poly(methacrylate) derivatives containing phthalimide ester functionalities. These modifications result in copolymers comprising diethyl isopropenylphosphonate, propylene, and methyl acrylate units, which have proven difficult to synthesize through standard radical polymerization methods. Moreover, the strategy effectively functionalizes precursors composed of styrene and phthalimide monomers, achieving functionalization degrees ranging from 7% to 21%. This level of control heralds new opportunities for designing polymers with bespoke architectures and functional group distributions.

Professor Inagi emphasizes that such postfunctionalization advances address critical limitations in copolymerizing olefins with activated vinyl monomers, a longstanding challenge due to poor olefin incorporation and harsh reaction conditions typically required. By elegantly circumventing these obstacles, the method enables phosphonate groups’ integration into olefin–methacrylate copolymers under mild, sustainable conditions, significantly expanding the attainable polymer chemical space.

The applications of these phosphonate-functionalized polymers are multifaceted. Their inherent fire-retardant characteristics make them ideal candidates for enhancing safety profiles in materials used in electronics and building sectors. Equally compelling is their potential role in lithium-ion battery technology; by acting as flame-retardant additives, these polymers could mitigate risks associated with battery fires, addressing an urgent safety concern in energy storage devices. Additionally, the temperature-responsive behavior of these materials opens avenues for smart coatings and responsive membranes, facilitating their adoption in cutting-edge technological applications.

A central advantage of this organophotoredox-catalyzed radical–polar crossover mechanism is its reliance on visible light as a sustainable energy source, eliminating the need for harsh reagents or elevated temperatures typically involved in polymer modification. The mild reaction conditions preserve polymer integrity while affording high selectivity and functional group tolerance. This methodological elegance further promotes environmentally benign practices in polymer chemistry, aligning with global efforts toward green and sustainable material synthesis.

The collaborative nature of this research, involving scientists from both the Institute of Science Tokyo and Kyoto University, highlights the interdisciplinary approach necessary to tackle complex chemical challenges. The study, published in the renowned journal Angewandte Chemie International Edition, serves as a testament to the innovative spirit driving contemporary materials science and photochemistry, combining strategic catalysis with polymer engineering to unlock unprecedented molecular transformations.

Looking forward, the research team aspires to extend their strategy to incorporate a broader spectrum of functional groups, thereby constructing next-generation polymers with diverse and tailored functionalities. Such endeavors promise to accelerate advancements in material performance and sustainability, impacting fields ranging from biomedicine to environmental technology. The modularity and tunability inherent in this photoredox-induced postfunctionalization herald a new paradigm for smart material development.

In sum, this pioneering organophotoredox-catalyzed postfunctionalization approach not only overcomes traditional limitations in polymer chemistry but also embodies the confluence of sustainability, innovation, and functionality. By leveraging the power of visible light to orchestrate complex radical and polar intermediate transformations, the research paves the way for a new class of high-value polymers with far-reaching implications across science and industry. As we strive for materials that meet the evolving demands of modern technologies, methodologies like this exemplar demonstrate how fundamental chemistry can propel us toward a smarter, safer future.

Subject of Research: Not applicable

Article Title: Organophotoredox-Catalyzed Postfunctionalization of Poly(methacrylate) Derivatives via Radical–Polar Crossover Phosphonylation

News Publication Date: 15-May-2025

Web References:
https://doi.org/10.1002/anie.202507572

Image Credits: Institute of Science Tokyo

Keywords

Materials science, Materials engineering, Engineering, Polymers, Chemical compounds, Chemistry