Photocatalytic Reduction of CO 2 to CO in 100%: The Synergistic Effect of Nickel and Europium in Heterometallic Clusters

Abstract Heterometallic transition‐rare earth metal (3d‐4f) clusters with synergistic catalytic activity are rarely identified. Herein, two families of closely related 3d‐Eu clusters were designed to analyze the role of Eu(III) ions during the photocatalytic reduction of CO 2 into CO. The M 24 Eu 8 family, where M = Co or Ni, shows much lower activity (CO production 5838 µ mol g −1 h −1 ). This is due to the two additional Eu(III) ions in the apical position of the latter which are very active for converting CO 2 into CO. Moreover, we found the nickel analogues are better than the cobalt ones, especially for Ni 24 Eu 10 which exhibits 100% CO selectivity and very high efficacy of 6545.3 µ mol g −1 h −1 , while the Co 24 Eu 10 only shows 55% CO selectivity. Therefore, the coexistence of both apical Eu(III) and Ni(II) ions has been experimentally revealed to be critical for this exceptional catalytic performance of the Ni 24 Eu 10 cluster. As such, this work unambiguously reveals a synergistic effect of bimetallic catalysts and may open a new avenue for more sophisticated reaction design by using the heterometallic coordination clusters.