Synergistic Metal-Acid Unit for Boosting Tandem Catalysis via Efficient Transformation of the Key Intermediate

The rational design of metal-acid bifunctional systems, which integrate (de)hydrogenation and acid-driven functionalities, holds great potential for steering tandem hydroconversion (HDC) processes. However, thermodynamic instability and unpredictable kinetic bifurcations of intermediates often compromise the target product selectivity. Herein, we reported a dual-confinement architecture that spatially encapsulates palladium nanoparticles and Keggin-type phosphotungstic acid (HPW) within a USY zeolite (denoted as Pd@HPW@USY), achieving geometrically optimized metal-acid proximity for regulation of the key intermediate in benzene hydroalkylation (HDA). Systematic investigations revealed that the spatial proximity of metal-acid sites facilitated the rapid migration of metal-generated cyclohexene to adjacent acid sites, where the enhanced protonation capability of confined W–OH acid sites of HPW (compared with conventional Al–OH acid sites in zeolites) promoted cyclohexene activation. The dual-confinement catalyst exhibited 73.8% selectivity and 47.3% yield toward cyclohexylbenzene, surpassing conventional catalysts with suboptimal spatial configurations: Pd/HPW/USY (40.9%, 25.5%), Pd/HPW@USY (51.6%, 30.5%), and Pd@HPW/USY (65.4%, 40.2%). In addition, Pd@HPW@USY exhibited superior cycling stability in the benzene HDA reaction. It is demonstrated that the synergistic interplay between spatial proximity and functional matching governs alkylation-dominated pathways for the key intermediate cyclohexene. This work establishes a paradigm for engineering metal-acid multifunctional systems, offering alternative opportunities for complex tandem reaction network manipulation.