Strong Visible‐Light‐Absorbing Cuprous Sensitizers for Dramatically Boosting Photocatalysis

Developing strong visible‐light‐absorbing (SVLA) earth‐abundant photosensitizers (PSs) for significantly improving the utilization of solar energy is highly desirable, yet it remains a great challenge. Herein, we adopt a through‐bond energy transfer (TBET) strategy by bridging boron dipyrromethene (Bodipy) and a CuI complex with an electronically conjugated bridge, resulting in the first SVLA CuI PSs (Cu‐2 and Cu‐3). Cu‐3 has an extremely high molar extinction coefficient of 162 260 m−1 cm−1 at 518 nm, over 62 times higher than that of traditional CuI PS (Cu‐1). The photooxidation activity of Cu‐3 is much greater than that of Cu‐1 and noble‐metal PSs (Ru(bpy)32+ and Ir(ppy)3+) for both energy‐ and electron‐transfer reactions. Femto‐ and nanosecond transient absorption and theoretical investigations demonstrate that a “ping‐pong” energy‐transfer process in Cu‐3 involving a forward singlet TBET from Bodipy to the CuI complex and a backward triplet‐triplet energy transfer greatly contribute to the long‐lived and Bodipy‐localized triplet excited state.