Charged Macromolecular Rhenium Bipyridine Catalysts with Tunable CO2 Reduction Potentials

Swagat Sahu; Po Ling Cheung; Charles W Machan; Steven A Chabolla; Clifford P Kubiak; Nathan C Gianneschi

doi:10.1002/chem.201701901

Charged Macromolecular Rhenium Bipyridine Catalysts with Tunable CO₂ Reduction Potentials

Chemistry. 2017 Jun 27;23(36):8619-8622. doi: 10.1002/chem.201701901. Epub 2017 Jun 5.

Authors

Swagat Sahu¹, Po Ling Cheung¹, Charles W Machan¹, Steven A Chabolla¹, Clifford P Kubiak¹, Nathan C Gianneschi^{1

2}

Affiliations

¹ Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.
² Materials Science & Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.

PMID: 28467613
DOI: 10.1002/chem.201701901

Abstract

A series of polymeric frameworks with functional assemblies were designed to alter the catalytic activity of covalently bound Re^I electrocatalysts. Norbornenyl polymers containing positively charged quaternary ammonium salts, neutral phenyl, or negatively charged trifluoroborate groups were end-labelled with a Re^I fac-tricarbonyl bipyridine electrocatalyst via cross metathesis. Electrochemical studies in acetonitrile under an inert atmosphere and with saturated CO₂ indicate that the quaternary ammonium polymers exhibit a significantly lower potential for CO₂ reduction to CO (ca. 300 mV), while neutral polymers behave consistently with what has been reported for the free, molecular catalyst. In contrast, the trifluoroborate polymers displayed a negative shift in potential and catalytic activity was not observed. It is demonstrated that a single catalytically active complex can be installed onto a charged polymeric framework, thereby achieving environmentally tuned reduction potentials for CO₂ reduction. These materials may be useful as polymer-based precursors for preparing catalytic and highly ordered structures such as thin films, porous catalytic membranes, or catalytic nanoparticles.

Keywords: CO2 reduction; cross metathesis; electrochemistry; macromolecules; ring-opening metathesis polymerization.