Journal
ACS CATALYSIS
Volume 11, Issue 5, Pages 3073-3083Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.0c05003
Keywords
selective O-2 reduction; cobalt corrole; H2O2 production; reaction mechanism; efficient catalysis
Categories
Funding
- MEXT (Japan) [16H02268]
- NRF of Korea through the CRI [NRF-2012R1A3A2048842]
- Basic Science Research Program [NRF-2020R1I1A1A01074630]
- Xi'an Key Laboratory of Organometallic Material Chemistry
- Fok Ying-Tong Education Foundation for Outstanding Young Teachers in University
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This study reports a highly efficient and selective method for reducing O-2 to H2O2 using a cobalt corrole catalyst, which shows good stability of the product.
Selective and efficient catalytic two-electron two-proton (2e(-)/2H(+)) reduction of dioxygen (O-2) to hydrogen peroxide (H2O2) has been achieved less successfully than four-electron four-proton (4e(-)/4H(+)) reduction of O-2 because of the instability of the H2O2 product in the presence of metal catalysts. We report herein a highly efficient 2e(-)/2H(+) reduction of O-2 by ferrocene (Fc; one-electron reductant) and 9,10-dihydro-10-methylacridine (AcrH(2); two-electron reductant and an NADH analog), with a cobalt corrole complex, [Co-III(tpfc)(Py)(2)] (1), in the presence of HClO4 in CH3CN at 298 K, affording a large TON (50,000) and a high turnover frequency (275 s(-1)) with 100% selectivity in producing H2O2. The H2O2 product yielded in the 2e(-)/2H(+) reduction of O-2 using AcrH(2) as a reductant was stable for more than 5 h even in the presence of 1. Detailed kinetic analysis revealed that the rate-determining step (rds) for the 2e(-)/2H(+) reduction of O-2 by Fc with 1 in the presence of HClO4 in CH3CN was the proton-coupled electron transfer from Co-III(tpfc) (2) to O-2 to produce a cobalt(III) corrole radical cation, [CoIII(tpfc(+))](+) (3), which was detected by EPR. When ferrocene was replaced by AcrH(2), the rds became the electron transfer from AcrH(2) to 3, coupled with the deprotonation of AcrH(2)(center dot+) (ET/PT), followed by fast ET from AcrH(center dot) to 3. To the best of our knowledge, this is a report of a highly efficient Co-corrole catalyst that retains its cobalt(III) oxidation state for the 2e(-)/2H(+) reduction of O-2 in producing H2O2 with a high selectivity.
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