Catalytic ammonia synthesis on HY-zeolite-supported angstrom-size molybdenum cluster

Abstract

The development of new catalysts with high N₂ activation ability is an effective approach for low-temperature ammonia synthesis. Herein, we report a novel angstrom-size molybdenum metal cluster catalyst for efficient ammonia synthesis. This catalyst is prepared by the impregnation of a molybdenum halide cluster complex with an octahedral Mo₆ metal core on HY zeolite, followed by the removal of all the halide ligands by activation with hydrogen. In this activation, the size of the Mo₆ cluster (ca. 7 Å) is almost retained. The resulting angstrom-size cluster shows catalytic activity for ammonia synthesis from N₂ and H₂, and the reaction proceeds continuously even at 200 °C under 5.0 MPa. DFT calculations suggest that NN bond cleavage is promoted by the cooperation of the multiple molybdenum sites.