Synthesis of 3,3’‐(Ethane‐1,2‐diylidene)bis(indolin‐2‐one) Promoted by Thermally‐activated Electron Transfer and Photoreduction of CO2 to CH4 and CO

Abstract

AbstractA Sonogashira coupling reaction leads to the formation of a serendipitous product C with the 3,3’‐(ethane‐1,2‐diylidene)bis(indolin‐2‐one) unit. To our knowledge, our study provides the first example demonstrating that electron transfer between isoindigo and triethylamine can be thermally activated and can be employed in synthesis. The physical properties of C suggest that it possesses decent photo‐induced electron‐transfer capabilities. Under the illumination of 136 mW cm−2 intensity, C yields ≈2.4 mmol gcat−1 (per gram of catalyst) of CH4 and ≈0.5 mmol gcat−1 of CO in 20 h in the absence of additional metal, co‐catalyst, and amine sacrificial agent. The primary kinetic isotope effect suggests that the bond cleavage of water is a rate‐determining step in the reduction. Moreover, the CH4 and CO production can be boosted as the illuminance increases. This study demonstrates that organic donor‐acceptor conjugated molecules are potential photocatalysts for CO2 reduction.