Photoreduction of carbon dioxide to carbon monoxide with hydrogen catalyzed by a rhenium(I) phenanthroline-polyoxometalate hybrid complex.

A phenanthroline ligand decorated at the 5,6-position with a 15-crown-5 ether was used to prepare a metalorganic-polyoxometalate hybrid complex Re(I)(L)(CO)(3)CH(3)CN-MHPW(12)O(40) (L = 15-crown-5-phenanthroline, M = Na(+), H(3)O(+)). X-ray diffraction, (1)H and (13)C NMR, ESI-MS, IR, and elemental analysis were used to characterize this complex. In the presence of Pt/C, the polyoxometalate moiety in Re(I)(L)(CO)(3)CH(3)CN-MHPW(12)O(40) can oxidize H(2) to two protons and two electrons which in the presence of visible light can catalyze the photoreduction of CO(2) to CO with H(2) as the reducing agent instead of the universally used amines as sacrificial reducing agents. An EPR spectrum of a stable intermediate species under reaction conditions shows characteristics of a PW(V)W(VI)(11)O(40) and a Re(0) species with a tentative assignment of the intermediate as Re(0)(L)(CO)(3)(S)-MH(3)PW(V)W(VI)(11)O(40).