Selectivity Modulation of Encapsulated Palladium Nanoparticles by Zeolite Microenvironment for Biomass Catalytic Upgrading

Metal nanoparticles encapsulated in zeolite have been recently developed as a special type of catalyst that shows significant advantages in activity, shape-selectivity, and stability over conventional supported catalysts. The selectivity modulation of encapsulated nanoparticle catalysis by the zeolite microenvironment is theoretically possible but not addressed yet. Here, we report the in situ encapsulation of sub-nanometric palladium species within MFI-type zeolites, which exhibit high activity and good stability in the hydroconversion of furfural as a model reaction of biomass upgrading. Remarkably, different products, e.g., furan, furfural alcohol, and 1,5-pentanediol, from furfural hydroconversion can be obtained when silicalite-1, Na-ZSM-5, and H-ZSM-5 are employed as hosts of palladium nanoparticles, respectively. Density functional theory calculations and spectroscopy investigations reveal that both the adsorption of furfural and the activation of hydrogen are significantly affected by the zeolite microenvironment, leading to different reaction pathways. Our work presents an elegant example of catalytic selectivity modulation of encapsulated metal nanoparticles by tuning the zeolite microenvironment.