Boosting CO2 photoreduction by π–π-induced preassembly between a Cu(I) sensitizer and a pyrene-appended Co(II) catalyst

The design of a highly efficient system for CO2 photoreduction fully based on earth-abundant elements presents a challenge, which may be overcome by installing suitable interactions between photosensitizer and catalyst to expedite the intermolecular electron transfer. Herein, we have designed a pyrene-decorated Cu(I) complex with a rare dual emission behavior, aiming at additional z -interaction with a pyrene-appended Co(II) catalyst for visible light-driven CO2- to- CO conversion. The results of 1H NMR titration, time-resolved fluorescence/absorption spectroscopies, quantum chemical simulations, and photocatalytic experiments clearly demonstrate that the dynamic z-z interaction between sensitizer and catalyst is highly advantageous in photocatalysis by accelerating the inter-molecular electron transfer rate up to 6.9 x 105 s-1, thus achieving a notable apparent quantum yield of 19% at 425 nm with near -unity selectivity. While comparable to most earth-abundant molecular systems, this value is over three times of the pyrene- free system (6.0%) and far surpassing the benchmarking Ru(II) tris(bipyridine) (0.3%) and Ir(III) tris(2-phenylpyridine) (1.4%) photosensitizers under parallel conditions.