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.
