Affiliation: | 1. Department of Chemistry, University of California, Berkeley, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720-1460 USA;2. Department of Chemistry, Pohang University of Science and Technology, Pohang, 37673 Republic of Korea Center for Self-assembly and Complexity (CSC), Institute for Basic Science (IBS), Pohang, 37673 Republic of Korea;3. Center for Self-assembly and Complexity (CSC), Institute for Basic Science (IBS), Pohang, 37673 Republic of Korea;4. Department of Chemistry, Pohang University of Science and Technology, Pohang, 37673 Republic of Korea |
Abstract: | We report a supramolecular strategy for promoting the selective reduction of O2 for direct electrosynthesis of H2O2. We utilized cobalt tetraphenylporphyrin (Co-TPP), an oxygen reduction reaction (ORR) catalyst with highly variable product selectivity, 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 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, whereas the Co-TPP monomer gives a 50 % mixture of H2O2 and H2O. Bimolecular pathways have been implicated in facilitating H2O formation, therefore, we attribute this high H2O2 selectivity to site isolation of the discrete molecular units in each supramolecule. 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. |