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Streater DH, Kennehan ER, Wang D, Fiankor C, Chen L, Yang C, Li B, Liu D, Ibrahim F, Hermans I, Kohlstedt KL, Luo L, Zhang J, Huang J. Control over Charge Separation by Imine Structural Isomerization in Covalent Organic Frameworks with Implications on CO 2 Photoreduction. J Am Chem Soc 2024; 146:4489-4499. [PMID: 38327095 DOI: 10.1021/jacs.3c10627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Two-dimensional covalent organic frameworks (COFs) are an emerging class of photocatalytic materials for solar energy conversion. In this work, we report a pair of structurally isomeric COFs with reversed imine bond directions, which leads to drastic differences in their physical properties, photophysical behaviors, and photocatalytic CO2 reduction performance after incorporating a Re(bpy)(CO)3Cl molecular catalyst through bipyridyl units on the COF backbone (Re-COF). Using the combination of ultrafast spectroscopy and theory, we attributed these differences to the polarized nature of the imine bond that imparts a preferential direction to intramolecular charge transfer (ICT) upon photoexcitation, where the bipyridyl unit acts as an electron acceptor in the forward imine case (f-COF) and as an electron donor in the reverse imine case (r-COF). These interactions ultimately lead the Re-f-COF isomer to function as an efficient CO2 reduction photocatalyst, while the Re-r-COF isomer shows minimal photocatalytic activity. These findings not only reveal the essential role linker chemistry plays in COF photophysical and photocatalytic properties but also offer a unique opportunity to design photosensitizers that can selectively direct charges.
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Affiliation(s)
- Daniel H Streater
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53233, United States
| | - Eric R Kennehan
- Magnitude Instruments, 200 Innovation Boulevard Ste. 224, State College, Pennsylvania 16803, United States
| | - Denan Wang
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Christian Fiankor
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Liangji Chen
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Chongqing Yang
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Bo Li
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Daohua Liu
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Faysal Ibrahim
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Ive Hermans
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Kevin L Kohlstedt
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Long Luo
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Jian Zhang
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Jier Huang
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53233, United States
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
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Guyot M, Lalloz MN, Aguirre-Araque JS, Rogez G, Costentin C, Chardon-Noblat S. Rhenium Carbonyl Molecular Catalysts for CO 2 Electroreduction: Effects on Catalysis of Bipyridine Substituents Mimicking Anchorage Functions to Modify Electrodes. Inorg Chem 2022; 61:16072-16080. [PMID: 36166597 DOI: 10.1021/acs.inorgchem.2c02473] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Heterogenization of molecular catalysts on (photo)electrode surfaces is required to design devices performing processes enabling to store renewable energy in chemical bonds. Among the various strategies to immobilize molecular catalysts, direct chemical bonding to conductive surfaces presents some advantages because of the robustness of the linkage. When the catalyst is, as it is often the case, a transition metal complex, the anchoring group has to be connected to the complex through the ligands, and an important question is thus raised on the influence of this function on the redox and on the catalytic properties of the complex. Herein, we analyze the effect of conjugated and non conjugated substituents, structurally close to anchoring functions previously used to immobilize a rhenium carbonyl bipyridyl molecular catalyst for supported CO2 electroreduction. We show that carboxylic ester groups, mimicking anchoring the catalyst via carboxylate binding to the surface, have a drastic effect on the catalytic activity of the complex toward CO2 electroreduction. The reasons for such an effect are revealed via a combined spectro-electrochemical analysis showing that the reducing equivalents are mainly accumulated on the electron-withdrawing ester on the bipyridine ligand preventing the formation of the rhenium(0) center and its interaction with CO2. Alternatively, alkyl-phosphonic ester substituents, not conjugated with the bpy ligand, mimicking anchoring the catalyst via phosphonate binding to the surface, allow preserving the catalytic activity of the complex.
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Affiliation(s)
- Mélanie Guyot
- DCM, CNRS, Univ Grenoble Alpes, Grenoble 38000, France
| | | | | | - Guillaume Rogez
- CNRS, IPCMS, University of Strasbourg, Strasbourg 67034, France
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