Hydrogenolysis Cleavage of the Csp2–Csp3 Bond over a Metal-Free NbOPO4 Catalyst

Abstract

Ru/NbOx catalysts, which combine the merits of facile hydrogen activation, a strong binding ability to the benzene ring, and the presence of Brønsted acid sites, were well investigated toward Csp2–Csp3 bond cleavage in the utilization of lignin and aromatic plastics (Chem 2019, 5, 1521; Angew. Chem. Int. Ed. 2021, 60, 5527). Herein, we unlock the ability of a bare NbOx catalyst in the dissociation and activation of a hydrogen molecule and further hydrogenolysis of the robust Csp2–Csp3 model compounds. In situ diffuse reflectance infrared Fourier transform and density functional theory calculations reveal that H2 can be dissociated and the stable surface hydride species can be produced over Nb2O5 through heterolytic and homolytic cleavages of H2 due to the existence of surface oxygen vacancies. Furthermore, the NbOPO4 catalyst with rich oxygen vacancy and Brønsted acidity not only allows the conversion of phenylcyclohexane to monocyclic compounds but also enables the conversion of polystyrene to arenes with a high selectivity by cleaving the Csp2–Csp3 bond. This study provides and proves the unique ability of the NbOPO4 catalyst in heterolytic and homolytic cleavages of H2 and the hydrogenolysis of robust Csp2–Csp3 bond containing compounds, including plastics, which would help to design low-cost metal-free hydrogenolysis catalysts.