Coupling Ruthenium Bipyridyl and Cobalt Imidazolate Units in a Metal-Organic Framework for an Efficient Photosynthetic Overall Reaction in Diluted CO 2 .

Artificial photocatalytic CO 2 reduction, using water as the reductant, is challenging mainly because it is difficult for multiple functional units to cooperate efficiently. Here, we show that the classic photosensitive and H 2 O-oxidizing ruthenium bipyridyl units and CO 2 -reducing cobalt imidazolate units can be incorporated into a metal-organic framework using a classic organic ligand, imidazo[4,5- f ][1,10]phenanthroline. Under visible light without additional sacrificial agents and photosensitizers, the overall conversion of CO 2 and H 2 O to CO and O 2 was achieved by the multifunctional photocatalyst in the CH 3 CN/H 2 O mixed solvent with a high CO production rate of 11.2 μmol g -1 h -1 and CO selectivity of ca. 100%. Thanks to its ultramicroporous structure with moderately strong CO 2 adsorption ability, the photocatalyst also exhibited high performances with CO/CH 4 production rates of 5.15/0.62 and 4.26/0.20 μmol g -1 h -1 in the gas phase with pure and even diluted CO 2 , respectively. Photoluminescence emission spectroscopy and photoelectrochemical tests confirmed that the photosensitive and catalytic units cooperated well to give suitable photocatalytic redox potentials and fast electron-hole separation.