Deposition of noble metals into small and medium pore zeolites remains challenging due to a lack of synthetic methods for metal incorporation. Solvated forms of noble metals typically are unable to fit within the pore openings of such zeolites and largely deposit on the surface preventing their inclusion by traditional incipient wetness impregnation or cation-exchange methodologies. However, once the metal is successfully incorporated, the sterically restrictive environments have been shown to stabilize clusters, single atoms, and small nanoparticles against agglomeration. As post-synthetic modification of zeolites with these metals is challenging, methodologies for metal incorporation during zeolite synthesis have been investigated. A major challenge in metal incorporation under the high pH and elevated temperatures typical of zeolite syntheses is the propensity for noble metals to precipitate from solution as metal hydroxide aggregates or nanoparticles. Ligation of metal precursors with multidentate or otherwise strongly binding ligands has been shown to help prevent precipitation and allow for incorporation of the metals into zeolite structures during synthesis, albeit in different forms (single-atoms, clusters, particles, etc.) of the deposited metal. Recently, N-heterocyclic carbenes (NHCs) have been shown to have extraordinary stabilizing effects as ligands to gold. As such, NHC-Au complexes may serve as ideal precursors for metal incorporation into zeolites without precipitation of hydroxide domains or formation of large nanoparticles and warrant investigation for this purpose.

Gold carbene complexes as precursors for gold incorporation in small or medium pore zeolites <i>via</i> metal entrapment during zeolite synthesis

256th National Meeting (2018)

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Gold carbene complexes as precursors for gold incorporation in small or medium pore zeolites via metal entrapment during zeolite synthesis