Associative-Distal Mechanism of the Haber–Bosch Process on a Ferrierite Catalyst with Spatially Isolated Dual Molybdenum Sites

The prevailing dissociative mechanism in the Haber–Bosch (H–B) process requires high temperatures to break the N≡N bond. How to dramatically promote the catalytic activity via mechanism innovation on earth-abundant catalysts is vital to achieving the ambient conditions of the H–B process. Herein, we theoretically identify an associative-distal mechanism within the large pore of a ferrierite catalyst anchored with dual Mo(II) active sites [L-2Mo(II)/FER], which is highly distinct from those previous mechanistic studies. With a much lower energy barrier for the N2 hydrogenation to N2H (0.73 eV) than direct N≡N bond breaking (1.38 eV), this catalyst enables a dominant associative distance mechanism for efficient ammonia synthesis. Microkinetic modeling results show a much higher turnover frequency (TOF) on L-2Mo(II)/FER than the step sites of the Ru catalyst at temperatures of 373–673 K. This work illustrated the high feasibility and crucial role of the associative-distal mechanism in the H–B process within porous catalysts anchored with multiple active sites, showcasing a successful catalyst design with a tailored reaction mechanism.