A Doughnut-Like Eu30 Catalyst for CO₂ Photoreduction with Turnover Numbers Over Ten Million

Polynuclear metal clusters can be potentially high-performance catalysts for the CO₂ reduction owing to the unique spatial structures among multiple active centers. Herein, two 30-nuclear doughnut-like lanthanide clusters (Eu30 and Dy30) were synthesized via in situ tandem reaction following a stepwise annular growth mechanism. In contrast to the Dy-based analog, Eu30 serves as a high-performance catalyst in visible-light-driven CO₂-to-CO conversion with 98% selectivity and a record-high turnover number reaching 1.720 × 10⁷, a rare case with only lanthanide metals as the active centers. Experimental and computational results indicate that the excellent performance of Eu30, as the first example of pure lanthanide cluster catalyst, can be attributed to its high redox activity with an appropriate LUMO energy level.