Periodic Reporting for period 4 - CLEANH2 (Chemical Engineering of Fused MetalloPorphyrins Thin Films for the Clean Production of Hydrogen)
Reporting period: 2024-11-01 to 2025-04-30
The CLEANH2 project addressed one of the most pressing global challenges of our time: the growing energy and environmental crisis driven by dependence on fossil fuels. The transition to sustainable energy sources requires efficient and affordable technologies for clean hydrogen production, a key energy carrier for a carbon-neutral future. Among various approaches, solar-driven water splitting offers a particularly attractive pathway to generate hydrogen directly from water using sunlight, without producing greenhouse gases.
CLEANH2 aimed to design and engineer a new generation of polymer catalysts based on metalloporphyrins—complex molecules that Nature employs to perform essential catalytic functions in photosynthesis and respiration. Owing to their conjugated molecular structure and the ability of their central metal ions to switch oxidation states, metalloporphyrins are highly promising for driving the oxidation and reduction reactions involved in water splitting. However, the potential of these molecules has been limited by the absence of efficient synthetic strategies to assemble them into conductive and durable conjugated polymer thin films suitable for heterogeneous catalysis.
Building on the team’s previous breakthrough in gas-phase synthesis and deposition of metalloporphyrin-based conjugated polymer thin films, CLEANH2 set out to develop high-performance electrocatalytic and photocatalytic materials for the clean and cost-effective production of hydrogen from water and sunlight. The project’s key objectives were to (i) understand the structural and electronic features that determine the catalytic activity and stability of metalloporphyrin-based conjugated polymers; (ii) develop synthetic routes to precisely tailor their microstructure and electronic properties; and(iii) demonstrate their performance in solar water-splitting systems for sustainable hydrogen generation.
By achieving these goals, CLEANH2 contributed to advancing the fundamental understanding and technological readiness of metalloporphyrin-based conjugated polymer thin films, paving the way for next-generation solar hydrogen production technologies that are both efficient and sustainable.
CLEANH2 aimed to design and engineer a new generation of polymer catalysts based on metalloporphyrins—complex molecules that Nature employs to perform essential catalytic functions in photosynthesis and respiration. Owing to their conjugated molecular structure and the ability of their central metal ions to switch oxidation states, metalloporphyrins are highly promising for driving the oxidation and reduction reactions involved in water splitting. However, the potential of these molecules has been limited by the absence of efficient synthetic strategies to assemble them into conductive and durable conjugated polymer thin films suitable for heterogeneous catalysis.
Building on the team’s previous breakthrough in gas-phase synthesis and deposition of metalloporphyrin-based conjugated polymer thin films, CLEANH2 set out to develop high-performance electrocatalytic and photocatalytic materials for the clean and cost-effective production of hydrogen from water and sunlight. The project’s key objectives were to (i) understand the structural and electronic features that determine the catalytic activity and stability of metalloporphyrin-based conjugated polymers; (ii) develop synthetic routes to precisely tailor their microstructure and electronic properties; and(iii) demonstrate their performance in solar water-splitting systems for sustainable hydrogen generation.
By achieving these goals, CLEANH2 contributed to advancing the fundamental understanding and technological readiness of metalloporphyrin-based conjugated polymer thin films, paving the way for next-generation solar hydrogen production technologies that are both efficient and sustainable.
Over the course of CLEANH2, significant progress was achieved in the design, synthesis, and application of metalloporphyrin-based conjugated polymer thin films as functional catalytic and sensing materials. The project combined advanced chemical vapor deposition techniques with molecular design strategies to create novel polymeric architectures with tunable electronic and catalytic properties.
The main achievement of CLEANH2 lies in the deep understanding and control of the chemical engineering of metalloporphyrin-based conjugated polymer thin films. The project developed methodologies to tailor their electronic structure, enhance charge transport, and increase their specific surface area, leading to improved catalytic activity. A key breakthrough was the successful heterogenization of fused porphyrin tapes for catalytic applications — a major step beyond the state of the art. Before CLEANH2, fused porphyrin tapes had only been studied in their dimeric form as homogeneous catalysts in solution.
Through the use of oxidative chemical vapor deposition (oCVD), the project demonstrated the ability to extend the π-conjugation length of porphyrins to form highly conjugated metalloporphyrin-based polymers, which could be directly integrated as thin films on virtually any substrate. This approach provides a scalable route to producing advanced catalytic materials for photoelectrochemical and electrocatalytic devices.
In addition to the investigations on water splitting reactions (HER and OER), CLEANH2 successfully developed highly active and selective metalloporphyrin-based conjugated polymer thin films for the electrochemical reduction of nitrate (NO₃⁻) to ammonia (NH₃). These materials exhibited exceptional performance, achieving ~95% Faradaic efficiency and current densities exceeding 300 mA·cm⁻² at –0.58 V_RHE. These results represent a major advance in the development of molecularly engineered catalysts for sustainable nitrogen conversion, offering a promising pathway for decentralized ammonia production using renewable electricity.
Beyond metalloporphyrins, CLEANH2 also demonstrated that oCVD polymerization can be extended to a wider range of polycyclic heteroaromatic compounds. This approach enabled the creation of novel conjugated polymer compositions that cannot be synthesized through conventional solution-based routes due to solubility limitations. Notably, the oCVD of several benzothiadiazole-based compounds yielded highly photoactive conjugated polymer thin films, which were successfully employed in the fabrication of thin-film heterostructures for photoelectrochemical water splitting.
The findings of CLEANH2 have been disseminated through peer-reviewed publications, conference presentations, invited talks, and collaborations within the catalysis and materials science communities. The methodologies developed for vapor-phase synthesis of metalloporphyrin-based conjugated polymers open new opportunities for scalable, solvent-free fabrication of catalytic devices. These advances lay the groundwork for the exploitation of CLEANH2 results in the fields of solar fuel generation and environmental remediation technologies.
The main achievement of CLEANH2 lies in the deep understanding and control of the chemical engineering of metalloporphyrin-based conjugated polymer thin films. The project developed methodologies to tailor their electronic structure, enhance charge transport, and increase their specific surface area, leading to improved catalytic activity. A key breakthrough was the successful heterogenization of fused porphyrin tapes for catalytic applications — a major step beyond the state of the art. Before CLEANH2, fused porphyrin tapes had only been studied in their dimeric form as homogeneous catalysts in solution.
Through the use of oxidative chemical vapor deposition (oCVD), the project demonstrated the ability to extend the π-conjugation length of porphyrins to form highly conjugated metalloporphyrin-based polymers, which could be directly integrated as thin films on virtually any substrate. This approach provides a scalable route to producing advanced catalytic materials for photoelectrochemical and electrocatalytic devices.
In addition to the investigations on water splitting reactions (HER and OER), CLEANH2 successfully developed highly active and selective metalloporphyrin-based conjugated polymer thin films for the electrochemical reduction of nitrate (NO₃⁻) to ammonia (NH₃). These materials exhibited exceptional performance, achieving ~95% Faradaic efficiency and current densities exceeding 300 mA·cm⁻² at –0.58 V_RHE. These results represent a major advance in the development of molecularly engineered catalysts for sustainable nitrogen conversion, offering a promising pathway for decentralized ammonia production using renewable electricity.
Beyond metalloporphyrins, CLEANH2 also demonstrated that oCVD polymerization can be extended to a wider range of polycyclic heteroaromatic compounds. This approach enabled the creation of novel conjugated polymer compositions that cannot be synthesized through conventional solution-based routes due to solubility limitations. Notably, the oCVD of several benzothiadiazole-based compounds yielded highly photoactive conjugated polymer thin films, which were successfully employed in the fabrication of thin-film heterostructures for photoelectrochemical water splitting.
The findings of CLEANH2 have been disseminated through peer-reviewed publications, conference presentations, invited talks, and collaborations within the catalysis and materials science communities. The methodologies developed for vapor-phase synthesis of metalloporphyrin-based conjugated polymers open new opportunities for scalable, solvent-free fabrication of catalytic devices. These advances lay the groundwork for the exploitation of CLEANH2 results in the fields of solar fuel generation and environmental remediation technologies.
Among the major achievements of the CLEANH2 project, the development of highly active and selective fused metalloporphyrin thin films for the electrochemical reduction of nitrate (NO₃⁻) to ammonia (NH₃) represents a substantial advancement beyond the state of the art. This breakthrough was not originally planned but emerged naturally from the project’s core research, reflecting the inherent catalytic versatility of metalloporphyrins—molecules that Nature itself has optimized for fundamental biological transformations such as photosynthesis (chlorophylls), respiration (cytochromes), and metabolism (vitamin B₁2).
By achieving precise control over the electronic and structural properties of fused metalloporphyrin thin films, CLEANH2 established a powerful platform for mimicking complex enzymatic processes and tackling other key catalytic reactions of industrial and environmental relevance. This ability to engineer catalytic activity and selectivity at the molecular level marks a decisive step toward the rational design of multifunctional, bioinspired catalysts for sustainable chemical transformations.
Importantly, this achievement laid the scientific and technological foundation for the successful SUN2CN EIC Pathfinder Challenge 2024 proposal, entitled “Solar-to-X devices for the decentralized prosumption of renewable fuels, chemicals and materials as a climate change mitigation pathway.” Building directly on the advances of CLEANH2, the SUN2CN project aims to develop a standalone Solar-to-X device that converts simple, low-energy molecules found in waste streams—such as nitrate (NO₃⁻) and carbon dioxide (CO2)—into valuable carbon–nitrogen (C–N) compounds using only sunlight as the energy source. These C–N chemicals, including urea and methylamine, are essential to agriculture and pharmaceutical production, contributing directly to human health and well-being.
Overall, CLEANH2 not only achieved a significant scientific leap in the field of molecularly engineered catalytic materials but also paved the way for a new generation of solar-driven conversion technologies.
By achieving precise control over the electronic and structural properties of fused metalloporphyrin thin films, CLEANH2 established a powerful platform for mimicking complex enzymatic processes and tackling other key catalytic reactions of industrial and environmental relevance. This ability to engineer catalytic activity and selectivity at the molecular level marks a decisive step toward the rational design of multifunctional, bioinspired catalysts for sustainable chemical transformations.
Importantly, this achievement laid the scientific and technological foundation for the successful SUN2CN EIC Pathfinder Challenge 2024 proposal, entitled “Solar-to-X devices for the decentralized prosumption of renewable fuels, chemicals and materials as a climate change mitigation pathway.” Building directly on the advances of CLEANH2, the SUN2CN project aims to develop a standalone Solar-to-X device that converts simple, low-energy molecules found in waste streams—such as nitrate (NO₃⁻) and carbon dioxide (CO2)—into valuable carbon–nitrogen (C–N) compounds using only sunlight as the energy source. These C–N chemicals, including urea and methylamine, are essential to agriculture and pharmaceutical production, contributing directly to human health and well-being.
Overall, CLEANH2 not only achieved a significant scientific leap in the field of molecularly engineered catalytic materials but also paved the way for a new generation of solar-driven conversion technologies.