W-O-Nb Heterostructure-Mediated Brønsted acid sites Enabling Enhanced NH3 Activation for Efficient Reductive Amination

The competitive adsorption and activation of H 2 and NH 3 molecules presents a fundamental challenge in catalytic reductive amination for sustainable amine synthesis. In this study, we address this issue by constructing a Ni/NbW 0.3 catalyst featuring a W-O-Nb composite oxide support designed to selectively enhance NH 3 adsorption and activation. Comprehensive characterization confirms that W doping creates a unique NbW x O (5/2+3x) structure with abundant W-O-Nb bridges, which generates strong Brønsted acid sites. These sites significantly enhance NH 3 protonation, thereby selectively promoting the rate-determining hydroammonolysis step by enhancing nucleophilic addition on the Schiff base intermediate. Hence, the Ni/NbW 0.3 catalyst delivers 99.9% yield of furfurylamine from the reductive amination of furfural, with a formation rate of 0.025 mol·g⁻ 1 ·h⁻ 1 under mild conditions (60 °C, 3 MPa H 2 , 0.4 MPa NH 3 ). Kinetic analyses reveal that the W-O-Nb structure substantially reduces both the activation energy (26.9 kJ·mol⁻ 1 ) and NH 3 reaction order (0.58), while poisoning experiments verify the essential role of Brønsted acid sites. The catalyst also demonstrates broad substrate adaptability and excellent recyclability. This work provides fundamental insights into the relationship between acid site engineering and reductive amination kinetics, establishing the W-O-Nb heterostructure design as an effective strategy for developing advanced amination catalysts.