Journal Article Ahead of print
PubMed: 42221526 DOI: 10.1039/d5sc06873h
Impacting the balance between CO 2 and proton reduction by control over aggregation in a model π-conjugated N-heterocycle - proflavine.
Chem Sci
Authors: Yana Reva, Jonas Färber, Yifan Bo, Maximilian A Thiele, Christian Hanke, Ayşe Günay-Gürer, Maximillian Herm, Johannes A C Barth, Dirk M Guldi
Affiliations
- Department of Chemistry and Pharmacy, Profile Center FAU Solar, Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg 91058 Erlangen Germany.
- Department Geographie und Geowissenschaften, Geozentrum Nordbayern, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) Schlossgarten 5 91054 Erlangen Germany.
Abstract
In this study, we investigated the mechanistic factors that govern the selective photocatalytic reduction of CO 2 over protons within a simple π-conjugated N-heterocycle, proflavine. Diluted conditions, where aggregates of 65 nm are formed, favored the selective CO 2 photo-reduction, while the gradual transition to concentrated conditions enabled photo-reductive H 2 generation. Proton reduction is coupled to larger aggregates, in which an alternative photo-relaxation pathway is active. We used transient absorption spectroscopy to corroborate that at low proflavine concentrations the presence of an electron donor triggers the one-electron reduced proflavine to perform the direct CO 2 reduction. At high proflavine concentrations, protonation of the one-electron reduced proflavine was favored due to a positive shift in basicity in larger aggregates with sizes over 1 µm. In turn, H 2 abstraction began with a pair of one-electron reduced, protonated, intermediates. Our study demonstrates an effective approach to limiting water reduction, a key challenge in advanced metal-free organic photocatalysis.
MeSH
Proflavine