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Supramolecular Tuning Enables Selective Oxygen Reduction Catalyzed by Cobalt Porphyrins for Direct Electrosynthesis of Hydrogen Peroxide

preprint
submitted on 18.12.2019 and posted on 23.12.2019 by Peter T. Smith, Younghoon Kim, Bahiru Punja Benke, Kimoon Kim, Christopher Chang

We report a supramolecular design strategy for promoting the selective reduction of O2 for direct electrosynthesis of H2O2. Specifically, we utilized cobalt tetraphenylporphyrin (Co-TPP), a non-selective oxygen reduction reaction (ORR) catalyst, as a building block to assemble the permanently porous supramolecular cage Co-PB-1(6) bearing six Co-TPP subunits connected through twenty-four imine bonds. Reduction of these imine linkers to amines yields the more flexible porous cage Co-rPB-1(6). Both Co-PB-1(6) and Co-rPB-1(6) cages produce 90-100% H2O2 from electrochemical ORR catalysis in neutral pH water, and we attribute this high selectivity to site isolation of the discrete molecular units, as the analogous Co-TPP monomer generates only a 50% mixture of H2O2 and H2O from electrochemical ORR under the same conditions. The ability to control reaction selectivity in supramolecular structures beyond traditional host-guest interactions offers new opportunities for designing such architectures for a broader range of catalytic applications.

Funding

Lawrence Berkeley National Laboratory DE-AC02-05CH11231

Institute for Basic Science IBS-R007-D1

History

Email Address of Submitting Author

peter.smith@berkeley.edu

Institution

UC Berkeley

Country

United States

ORCID For Submitting Author

0000-0002-8892-3752

Declaration of Conflict of Interest

The authors declare no conflict of interest.

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