Electrocatalytic proton and CO2 reduction: Metal based fused diporphyrins with proton relays for efficient catalysis

Project Information

MC-FMP-ECAT

Grant agreement ID: 894082

DOI

10.3030/894082

Project closed

EC signature date 24 November 2020

Start date 1 March 2021

End date 28 February 2023

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 162 806,40

EU contribution

€ 162 806,40

Coordinated by

UNIVERSITY OF STUTTGART
Germany

Periodic Reporting for period 1 - MC-FMP-ECAT (Electrocatalytic proton and CO2 reduction: Metal based fused diporphyrins with proton relays for efficient catalysis)

Reporting period: 2021-03-01 to 2023-02-28

Summary of the context and overall objectives of the project

- The project “Electrocatalytic proton and CO2 reduction: Metal based fused diporphyrins with proton relays for efficient catalysis” explores the design and development of dinuclear metalloporphyrin catalysts for sustainable hydrogen production and CO2 reduction at laboratory scale. Fused porphyrins are unique structural motifs in which two monoporphyrin units are connected via β–β, meso–meso, β′–β′ triple covalent linkages that allow seamless delocalization and storage of electrons across extended multimetallic ligand scaffolds. The project sought to investigate the impact of covalent linkages on the optical, electronic, (spectro)electrochemical, magnetic and electrocatalytic activities of metal complexes of bis-porphyrins.
- The development of catalysts for the sustainable production of hydrogen is one of the most pressing issues of current time. Different catalysts investigated over the years are still plagued with problems related to overpotential, catalytic efficiency and widespread applicability. Therefore, studies on the coordination chemistry, electronic and catalytic properties of the fused porphyrins are expected to open a new avenue for the design of efficient catalytic systems for electrochemical small molecule activation reactions.
- Overall objectives of the MSCA IF project are: a) development of effective synthetic protocols for the synthesis of first row transition metal complexes of bimetallic triply fused and monomeric metalloporphyrins; b) tuning the functional groups to study the effect and address solubility problems; c) establishment of electronic structures of the complexes and exploration of the catalytic activity of the metalloporphyrins in electrocatalytic proton and CO2 reduction; d) Quantification of catalytic parameters, analysis of catalytic efficiency for comparison with monomeric complexes and elucidation of the mechanistic pathway for establishing a structure-activity relationship.
- The study revealed a positive influence of extensive electron delocalization on the higher activity and lower overpotential of the fused metalloporphyrins in proton reduction than the mononuclear complexes. In addition, the influence of a subtle change in the peripheral substituents on the solubility and catalytic efficiency was also highlighted.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

- The overall work of the MSCA project was performed according to the individual work packages: a) WP1 involved the development of synthetic methods for various precursor materials and transition metal (Cu, Ni, Co and Fe) complexes of metalloporphyrin monomers in appreciable yield and their characterization; b) WP2 included the design and modification of the effective synthetic strategies for the binuclear triply fused metalloporphyrins. The incorporation of selective functional groups through a comprehensive structure-activity analysis to improve solubility and low yields. Simplified purification techniques to minimize the loss of complexes during post-synthetic workup. A wide range of instrumental and theoretical techniques were employed to successfully determine the electronic structure of the complexes; c) WP3 comprised the study of the catalytic activity of the dinuclear and mononuclear metalloporphyrins in electrochemical proton and CO2 reduction reactions. Collaborative networks were established with colleagues from the Institute of Physical Chemistry to perform various experiments to substantiate and determine the electronic structures of these frameworks. The data obtained from the measurements showed a significant increase in catalytic activity and reduction in overpotential for the dinuclear complexes compared to the mononuclear complexes; d) WP4 encompassed evaluation of the catalytic parameters and the elucidation of the mechanistic pathway for the comparison of the catalytic activity between mono- and dinuclear metalloporphyrins. In addition, together with colleagues from the host research group, the candidate was involved in setting up a gas chromatography, bulk electrolysis and designing new cells for in situ EPR. Theoretical insights into the mechanism were gained via active collaboration with the institute’s theoretical research group. Evaluation of the catalytic parameters revealed a significant enhancement in the turnover numbers and Faradaic efficiency of the expanded metalloporphyrins. In addition, various strategies were successfully employed to address the problems associated with these moieties, such as insolubility and low product yield to a considerable extent. In addition, we have also used the setup to successfully demonstrate electrochemical CO2 reduction using a Ru-based molecular catalyst.
- Part of the project has already been published in three international peer-reviewed journals (Chem. Eur. J., 2022, 28, e202104550, ChemSusChem, 2023, 16, e202201146 and Chem. Eur. J., 2023, e202300405), while the remaining results will also soon be published. In addition, the results of the projects were presented at three international conferences (ICPP-2022, Madrid, ICOMC-2022, Prague and 55th DCHEMA-2022, Weimar) either in the form of poster or a talk. While, various aspects of the project were also discussed at the Open Science Day of the University of Stuttgart for various high-school and bachelor students.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The MSCA project was designed to perform a comprehensive analysis of fused metalloporphyrins. The investigation conducted in this project utilized these unique molecules as catalysts for electrochemical proton and CO2 reduction reactions and set a benchmark for the further use of these molecules in the development of improved catalytic systems. Moreover, analysis of the electronic structures and the elucidation of the mechanistic pathway provided a rationale for why this class of molecules needs to be further investigated. Several key aspects of the projects encompassed; a) standardization of purification techniques for convenient access to these molecules, b) a detailed article summarizing various properties of all the fused porphyrinoids that could serve as a reference for further studies, c) the outcome of this project enabled the researcher to draft a proposal for the further investigation on a similar type of molecules in a SFB funded projects, e) introducing high school and undergraduate students to the biological relevance of metalloporphyrins.
In addition, the results of the project have been disseminated to a wider audience through conferences and scientific forums to attract the attention of the scientific community. The collaborative network with multidisciplinary research groups was established. The supervision of a bachelor student (thesis defended in summer 2022), a research intern and a PhD student, contributed to the overall academic growth of the researcher. In addition, involvement in teaching the Inorganic Chemistry course (winter semester 2021 and 2022) for first year environmental engineering students and participation in different workshops, namely the ARPE EPR summer school (summer 2021) and the Metal-Radical interaction workshop (summer 2022), equipped the researcher with a range of new expertise. In summary, this MSCA funding not only provided technical details regarding the usefulness of fused metalloporphyrin in energy-related small molecule activation, but also contributed to the overall maturity of the researcher.

A workshop involving researchers from Institute for Inorganic Chemistry and Physical Chemistry

Oral presentation, group photo and abstract at ICPP-2022 conference

Conference abstract (ICOMC-2022) and poster presentation in German chemical society Catalysis conf.