Periodic Reporting for period 3 - CLEANH2 (Chemical Engineering of Fused MetalloPorphyrins Thin Films for the Clean Production of Hydrogen)
Periodo di rendicontazione: 2023-05-01 al 2024-10-31
The CLEANH2 project stands in the general context of the current worldwide energy and environmental crisis. It aims to engineer a new generation of conjugated microporous polymers based on fused metalloporphyrins for the low-cost, clean and efficient production of hydrogen from solar water splitting.
The CLEANH2 concept relies on the gas phase reaction of metalloporphyrins to engineer new heterogeneous catalysts with remarkable hydrogen production yields. Metalloporphyrins, selected by Nature to fulfil the main catalytic phenomena allowing life (photosynthesis and respiration), are attractive molecules for water splitting owing to their highly conjugated structure and central metal ion, which can readily interconvert between different oxidation states to accomplish oxidation and reduction reactions. For efficiency and sustainability considerations, it is highly desirable to employ metalloporphyrins in conductive assemblies for heterogeneous catalysis. Nevertheless, due to the lack of synthetic approach, the design and application of conjugated porphyrin assemblies is a largely unexplored topic in view of the plethora of available porphyrin patterns.
The central idea of CLEANH2 builds upon our recent advance in the gas phase synthesis and deposition of directly fused metalloporphyrins coatings. Progress in our approach is expected to open the way for the construction of powerful catalytic and photocatalytic materials. To achieve this, the key challenging goals of this project are: 1) the engineering of the microstructure and electronic structure of directly fused metalloporphyrins thin films; 2) the use of the full potential of directly fused metalloporphyrins thin films for the unmet, clean and high quantum yield overall water splitting for hydrogen production. The outcomes of CLEANH2 will be foundational for the engineering of directly fused metalloporphyrins systems and their implementation in advanced technological applications related to catalysis and solar energy.
The CLEANH2 concept relies on the gas phase reaction of metalloporphyrins to engineer new heterogeneous catalysts with remarkable hydrogen production yields. Metalloporphyrins, selected by Nature to fulfil the main catalytic phenomena allowing life (photosynthesis and respiration), are attractive molecules for water splitting owing to their highly conjugated structure and central metal ion, which can readily interconvert between different oxidation states to accomplish oxidation and reduction reactions. For efficiency and sustainability considerations, it is highly desirable to employ metalloporphyrins in conductive assemblies for heterogeneous catalysis. Nevertheless, due to the lack of synthetic approach, the design and application of conjugated porphyrin assemblies is a largely unexplored topic in view of the plethora of available porphyrin patterns.
The central idea of CLEANH2 builds upon our recent advance in the gas phase synthesis and deposition of directly fused metalloporphyrins coatings. Progress in our approach is expected to open the way for the construction of powerful catalytic and photocatalytic materials. To achieve this, the key challenging goals of this project are: 1) the engineering of the microstructure and electronic structure of directly fused metalloporphyrins thin films; 2) the use of the full potential of directly fused metalloporphyrins thin films for the unmet, clean and high quantum yield overall water splitting for hydrogen production. The outcomes of CLEANH2 will be foundational for the engineering of directly fused metalloporphyrins systems and their implementation in advanced technological applications related to catalysis and solar energy.
Since the beginning of the project, fused porphyrin tapes chelating various metal cations and bearing different substituents have been synthesized via chemical vapor deposition. Interestingly, the proposed CVD approach enables the simultaneous synthesis, deposition and integration of fused porphyrin tapes for practical applications. Fused porphyrin tapes have been implemented for the first time as heterogeneous catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The intermolecular and intramolecular dehydrogenative coupling of metalloporphyrins enable the efficient separation and transfer of the charge carriers, considerably reducing the overpotential required for performing HER or OER.
The influence of the central metal cation and substituent on the polymerization reaction and side reaction (demetallation, remetallation) has been exemplified. Beyond, the influence of the central metal cation and substituent on the electronic and optoelectronic properties of the formed fused porphyrin thin films has been elucidated, enabling to engineer the band gap, positions of the frontier energy levels and charge carrier type of the fused porphyrin thin films for improved catalytic properties.
Beyond the deposition of previously reported fused porphyrin chemistries, the copolymerization of multiple porphyrin monomers was demonstrated to readily produce entirely new porphyrin systems that cannot be reached via conventional solution-based approaches due to insolubility, phase segregation or different reactivity ratios. In particular, fused porphyrin tapes chelating different metal cations and substituted with different groups are synthesised in one-step. In addition, we demonstrate how the copolymerisation of porphyrins can influence the regioselectivity of the oxidative coupling, enable higher electrical conductivities and yield the formation of donor-acceptor structures with narrower band gaps. Particularly, the present work paves the way to the engineering of multi-metallic catalysts for HER, OER or CO2 reduction and other important chemical conversion reactions. Indeed, heterometallic porphyrin conjugated polymer thin films hold great promise for multi-metallic electrocatalysis. Bimetallic porphyrin polymers are notably reported to exhibit better catalytic oxygen evolution reaction activity than their monometallic counterparts due to synergetic interactions between iron and nickel centres.
The influence of the central metal cation and substituent on the polymerization reaction and side reaction (demetallation, remetallation) has been exemplified. Beyond, the influence of the central metal cation and substituent on the electronic and optoelectronic properties of the formed fused porphyrin thin films has been elucidated, enabling to engineer the band gap, positions of the frontier energy levels and charge carrier type of the fused porphyrin thin films for improved catalytic properties.
Beyond the deposition of previously reported fused porphyrin chemistries, the copolymerization of multiple porphyrin monomers was demonstrated to readily produce entirely new porphyrin systems that cannot be reached via conventional solution-based approaches due to insolubility, phase segregation or different reactivity ratios. In particular, fused porphyrin tapes chelating different metal cations and substituted with different groups are synthesised in one-step. In addition, we demonstrate how the copolymerisation of porphyrins can influence the regioselectivity of the oxidative coupling, enable higher electrical conductivities and yield the formation of donor-acceptor structures with narrower band gaps. Particularly, the present work paves the way to the engineering of multi-metallic catalysts for HER, OER or CO2 reduction and other important chemical conversion reactions. Indeed, heterometallic porphyrin conjugated polymer thin films hold great promise for multi-metallic electrocatalysis. Bimetallic porphyrin polymers are notably reported to exhibit better catalytic oxygen evolution reaction activity than their monometallic counterparts due to synergetic interactions between iron and nickel centres.
The heterogenization of fused porphyrin tapes for catalytic application represent a significant progress beyond the state of the art. While these compounds were only investigated in the dimer form as homogeneous catalysts, the CVD of porphyrins enable to expand the conjugation length (forming long oligomers or polymers) and integrate them as thin films on virtually any substrate to form advanced and up-scalable catalytic devices.
The ability to easily perform the molecular engineering of porphyrin-based conjugated polymers represents a breakthrough in the field. Indeed, the careful selection of the central metal cation and/or substituents provides a simple method to tune the degree of conjugation, porosity, frontier energy levels and charge carrier type of the porphyrin-based conjugated polymers, driving the catalytic performances. Beyond, we demonstrated how the copolymerization of multiple porphyrin monomers to produce entirely new porphyrin systems that cannot be reached via conventional solution-based approaches due to insolubility, phase segregation or different reactivity ratios. In particular, fused porphyrin tapes chelating different metal cations and substituted with different groups are synthesised in one-step. In nature, the proximity of different metal cations in metalloproteins such as superoxide dismutase (combining copper and zinc cations), carbon monoxide dehydrogenase (combining iron and nickel) or cytochrome c oxidase (combining copper and iron) gives rise to cooperative catalytic effects.
The second part of the CLEANH2 project will focus on improving the photocatalytic properties of the porphyrin-based conjugated polymers, notably via the copolymerisation of electrocatalytically active porphyrin moities with photoactive moities.
The ability to easily perform the molecular engineering of porphyrin-based conjugated polymers represents a breakthrough in the field. Indeed, the careful selection of the central metal cation and/or substituents provides a simple method to tune the degree of conjugation, porosity, frontier energy levels and charge carrier type of the porphyrin-based conjugated polymers, driving the catalytic performances. Beyond, we demonstrated how the copolymerization of multiple porphyrin monomers to produce entirely new porphyrin systems that cannot be reached via conventional solution-based approaches due to insolubility, phase segregation or different reactivity ratios. In particular, fused porphyrin tapes chelating different metal cations and substituted with different groups are synthesised in one-step. In nature, the proximity of different metal cations in metalloproteins such as superoxide dismutase (combining copper and zinc cations), carbon monoxide dehydrogenase (combining iron and nickel) or cytochrome c oxidase (combining copper and iron) gives rise to cooperative catalytic effects.
The second part of the CLEANH2 project will focus on improving the photocatalytic properties of the porphyrin-based conjugated polymers, notably via the copolymerisation of electrocatalytically active porphyrin moities with photoactive moities.