Boosting CO 2 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 CO 2 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 π-interaction with a pyrene-appended Co(II) catalyst for visible light–driven CO 2 -to-CO conversion. The results of 1 H NMR titration, time-resolved fluorescence/absorption spectroscopies, quantum chemical simulations, and photocatalytic experiments clearly demonstrate that the dynamic π–π interaction between sensitizer and catalyst is highly advantageous in photocatalysis by accelerating the intermolecular electron transfer rate up to 6.9 × 10 5 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.