Partial hydrogenation of anisole to cyclohexanone in water medium catalyzed by atomically dispersed Pd anchored in the micropores of zeolite

Cyclohexanone is an important raw material for manufacturing nylon and other chemicals. The sustainable conversion of biomass derived molecules to cyclohexanone is desired but still challenging. Herein, a palladium single atom catalyst anchored in the micropores of zeolite (namely Pd₁/ZSM-5) is designed and exhibits remarkable catalytic activity in transforming anisole to cyclohexanone in water medium (H₂O), without using of organic solvent or halogen promoter. The selectivity to cyclohexanone is 91.2% and the turnover rate (TOR) is 400.8 h⁻¹ at 453 K. The Pd sites, acid sites, and microporous confinement environment of zeolite cooperate to promote the partial hydrogenation to cyclohexanone, and inhibit further hydrogenation as the side reaction. H₂O not only acts as the solvent, but also participates significantly in the partial hydrogenation. Moreover, as revealed by isotope labelled experiments (D₂O and H₂¹⁸O), the water participated hydrogenolysis and the consequent partial hydrogenation mechanism is proposed.