One Iron for Two Iron Sites in a Metal-Organic Framework Toward Simultaneous N-H Activation under Mild Conditions.

Iron-based catalysts play an important role in the ammonia industry. As one of the most abundant iron minerals, FeO containing Fe and Fe sites is widely distributed in the earth's crust and even on exoplanets, theoretically giving it both economic and catalytic potentials in ammonia synthesis. However, in the absence of specific active co-catalyst and harsh conditions, FeO is impossible to achieve ammonia synthesis alone. Here, we designed to activate the relatively inert Fe and Fe sites in FeO with a third Fe site inlayed in a coordination framework (MIL-101(Fe)) to achieve the unpresented multi-site collaborative catalysis. In-depth mechanism study confirmed the roles of three different Fe sites in N activation, H activation, and product transfer, respectively. Efficient N-H activation to NH on the FeO-based catalytic system has been achieved at extremely mild conditions. Our research provides a theoretical basis and a new strategy for designing efficient non-noble metal-based ammonia synthesis catalyst with minimized energy consumption.