Photocatalytic liposomes are a promising supramolecular platform for artificial photosynthesis,^[1] but the understanding of reaction mechanisms and surface dynamics between membrane-bound molecular components still remain a challenge. In this presentation, we will report the photocatalytic CO₂ reduction performance of a series of 3d transition metal terpyridine and porphyrin catalysts immobilised on liposomes,^[2-4] and briefly about their use in (photo)electrocatalytic CO₂ reduction.^[5] Time-resolved spectroscopy was utilised to provide new insights into electron transfer processes taking place between the electron donor (sodium ascorbate) and membrane-bound photosensitiser and catalyst molecules. The most active molecular photocatalyst system, containing a cobalt porphyrin, was studied by (spectro)electrochemistry and density functional theory to gain a better understand of its enhanced performance compared to the other studied assemblies, and to propose a possible reaction mechanism for CO₂ reduction.^[4] Furthermore, the same cobalt porphyrin catalyst is successfully utilised in a (photo)electrochemical device that can simultaneously reduce CO₂ and reform plastic waste.^[5] Therefore, our findings demonstrate the great potential of liposomes as versatile photocatalytic scaffolds. We also show how the same molecular catalyst can be utilised successfully in photocatalytic and (photo)electrocatalytic systems, and illustrate the power of combining time-resolved and in situ spectroscopic techniques to understand molecule-based systems.

References:

[1]         Pannwitz, A.; Klein, D. M.; Rodríguez-Jiménez, S.; Casadevall, C.; Song, H.; Reisner, E.; Hammarström, L.; Bonnet, S., Roadmap towards solar fuel synthesis at the water interface of liposome membranes. Chem. Soc. Rev. 2021, 50, 4833-4855.

[2]         Wang, Q.; Warnan, J.; Rodríguez-Jiménez, S.; Leung, J. J.; Kalathil, S.; Andrei, V.; Domen, K.; Reisner, E., Molecularly engineered photocatalyst sheet for scalable solar formate production from carbon dioxide and water. Nat. Energy 2020, 5, 703–710.

[3]         Zhang, X.; Cibian, M.; Call, A.; Yamauchi, K.; Sakai, K., Photochemical CO₂ Reduction Driven by Water-Soluble Copper(I) Photosensitizer with the Catalysis Accelerated by Multi-Electron Chargeable Cobalt Porphyrin. ACS Catal. 2019, 9, 11263-11273.

[4]         Rodríguez-Jiménez, S.; Song, H.; Lam, E.; Wright, D.;Pannwitz, A.; Bonke, S. A.; Baumberg, J. J.; Bonnet, S.; Hammarström, L.; Reisner E., Self-Assembled Liposomes Enhanced Electron Transfer for Efficient Photocatalytic CO₂ Reduction. J. Am. Chem. Soc. 2022, 144, 9399-9412.

[5]         Bhattacharjee, S.; Rahaman, M.; Andrei, V.; Miller, M. Rodríguez-Jiménez, S.; Lam, E.; Pornrungroj C.; Reisner, E., Photoelectrochemical CO₂-to-fuel conversion with simultaneous plastic reforming. Nat. Synth (2023). in print (https://doi.org/10.1038/s44160-022-00196-0).