C3 Product Formation from CO₂ by Br-Bridged Dinuclear Cu(I) Complex Electrocatalyst

Molecular metal complex catalysts are highly tunable in terms of their CO₂ reduction reaction (CO₂RR) performance due to their flexible molecular design. However, metal complex catalysts face challenges in their structural stability, and it has not been possible to synthesize high-value-added C3 products due to their inability to perform C–C coupling. In this presentation, we show a CO₂ reduction reaction catalyzed by a Br-bridged dinuclear Cu(I) complex. The Faradaic efficiency was found to be ~50% for C2 products and 12% for propanol at 1.8 V vs Ag/AgCl. Using operando XAFS analysis, we confirmed that during the CO₂RR, the metal complex structure is maintained without forming Cu metal. Operando spectroscopic analysis for the CO₂RR with ¹³CO₂ and using surface plasmons enabled the identification of intermediates important for C3 formation. Investigations using DFT calculations revealed a mechanism that can explain both the operando measurements and energetics. The results suggest that the catalyst produces C3 products by forming an intermediate species via C–C coupling between two Cu centers and flexibly varying the distance between them.¹⁾ To the best of our knowledge, previous examples of a molecular catalyst that generates C3 products from CO₂ have remained elusive. The achievement of C–C coupling by the CO₂RR in a metal complex that can freely adjust the electronic state of the reaction center and the reaction environment while maintaining its structure may be a major step towards the selective synthesis of higher value-added multi-carbon products.<br/><br/>References:<br/>[1] N. Sakamoto, K. Sekizawa, et al., <i>Nat. Catal.</i>, <b>2024</b>, <i>7</i>, 574-584.