Mercaptoamine-assisted Post-encapsulation of Metal Nanoparticles within Preformed Zeolites and their Analogues for Hydroisomerization and Methane Decomposition

We report a general synthetic strategy for post-encapsulation of metal nanoparticles within preformed zeolites using post-synthetic modification. Both anionic and cationic precursors to metal nanoparticle are supported on 8- and 10-membered ring zeolites and analogues during wet impregnation using 2-aminoethanethiol (AET) as a bi-grafting agent. Thiol groups are coordinated to metal centers, whereas amine moieties are dynamically attached to micropore walls via acid-base interactions. The dynamic acid-base interactions cause the even distribution of the metal-AET complex throughout the zeolite matrix. These processes encapsulate Au, Rh, and Ni precursors within the CHA, *MRE, MFI zeolite, and SAPO-34 zeolite analogues, for which small channel apertures preclude the post-synthesis impregnation of metal precursors. Sequential activation forms small and uniform nanoparticles (1-2.5 nm in diameter), as confirmed through electron microscopy and X-ray absorption spectroscopy. Containment within the small micropores protected the nanoparticles against harsh thermal sintering conditions and prevented the fouling of the metal surface by coke, thus resulting in a high catalytic performance in n-dodecane hydroisomerization and methane decomposition. The remarkable specificity of the thiol to metal precursors and the dynamic acid-base interaction make these protocols extendable to various metal-zeolite systems, suitable for shape-selective catalysts in challenging chemical environments.

Automated summary

We present a general synthetic approach for encapsulating metal nanoparticles within preformed zeolites using post-synthetic modification. The encapsulation process involves supporting anionic or cationic precursors onto the zeolite framework using a bi-grafting agent, resulting in the formation of small and uniform nanoparticles. The encapsulation provides protection against thermal sintering and coke fouling, leading to high catalytic performance in hydroisomerization and methane decomposition.