CO 2 /CO-to-C 3+ products electrochemical conversion for dinuclear cuprous molecular catalysts Naonari Sakamoto , Keita Sekizawa, Soichi Shirai, Takamasa Nonaka, Takeo Arai, Shunsuke Sato, Takeshi Morikawa Toyota Central R&D Labs., Inc., Japan CO 2 reduction reaction (CO 2 RR) is considered one of the most promising technologies for addressing climate change and energy depletion, as it synthesizes valuable chemical products and fuels from greenhouse gases. By using molecular metal complex catalysts in electrochemical CO 2 RR combined with photovoltaics [1-3] , we have achieved a 20% conversion of solar energy to chemical energy for CO 2 [2] and a 13.7% conversion for HCOOH [3] . The high catalytic activity is due to the characteristics of molecular catalysts, which can control the electronic/chemical environment of the catalytic active site by appropriately selecting organic ligands that can be freely modified. Compared to molecular catalysts that produce CO and HCOOH, there are surprisingly few reports of molecular catalysts that can produce multi-electron reduction products (ethylene, ethanol) that involve C-C coupling reactions. Furthermore, it is known that C 2 products forming molecular catalysts decompose during the reaction and change into metal, so the precisely controlled active sites cannot be fully utilized. In order to achieve highly efficient C 2 products formation using molecular catalysts, it is important to develop molecular catalysts that are structurally stable during the reaction. This study demonstrated a Br-bridged copper dinuclear molecular catalyst with high robustness for CO 2 /CO reduction reactions, producing C 3+ products, including C 3 H 7 OH beyond C 2 products [4] . Operando XAFS and various spectroscopic analyses show that the dinuclear molecular catalyst maintains a stable Cu(I) state during the reduction reaction, preventing decomposition. Operando spectroscopic analysis using localized surface plasmon resonance identifies key C 2 and C 3 coupling intermediates essential for C 3 production. Reaction intermediates obtained by 13 CO 2 -labeled operando analysis were also corroborated. DFT calculations propose a mechanism where the reaction proceeds at room temperature to form C 3 coupling species. The transition state structures resulting from this mechanistic analysis suggest that the progression of C-C coupling in the Cu dinuclear molecular metal complex is facilitated by forming a CO 2 /CO-reduced intermediate species that bridges the two Cu active sites. The bridging intermediate can adjust the Cu-Cu distance during the reaction, attracting reducing species to one Cu side and accepting substrate to the other Cu side. C 3 H 7 OH is formed through C-C coupling in flexible Cu binuclear structures at the bridging site. The discovery of a robust molecular catalyst for C 3+ production provides a molecular design guideline for developing next-generation catalysts for multicarbon CO 2 reduction products. References 1. T. Nishi, N. Sakamoto, K. Sekizawa, T. Morikawa, S. Sato, ChemSusChem 2025 , 18, e202401082. 2. K. Sekizawa, S. Sato, N. Sakamoto, T. M. Suzuki, T. Morikawa, ChemRxiv , 2024 , 10.26434/chemrxiv-2024-brj46. 3. J. Jung, K. W. Lee ‡ , N. Sakamoto ‡ , S. Kaliyamoorthy ‡ , T. Wakabayashi, K. Kamada, K. Sekizawa, S. Sato, T. M Suzuki, T. Morikawa, S. Saito, EES Catal , 2025 , 3, 254-258. ‡ These authors contributed equally to this work. 4. N. Sakamoto, K. Sekizawa, S. Shirai, T. Nonaka, T. Arai, S. Sato, T. Morikawa, Nat. Catal., 2024 , 7, 574-584 .
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