High-Density Catalytic Sites Grafting on 2D-Metal Oxides for Acceptorless Alcohol Dehydrogenation.

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Installing well-defined high density single-atomic catalyst (SAC) sites is highly desired for the synergistic cooperative effect in efficient chemical synthesis but elusive to synthesize due to unavoidable atomic segregation into clusters or particulates. We implemented a 2D-nanoconfined SAC grafting strategy. Inside a bilayer silica envelope, single metal hydroxide layer, pre-loaded with the catalytic metal (Pt, Pd, Ir) precursors, underwent controlled thermal conversion to the homogeneously embedded SACs decorated onto the in-situ generated 1 nm-thin transition metal oxide (TMO) nanosheet. Ultranarrow confined slit-space exclusively availed laterally emerging cation vacancies of TMO host, as atomic scale sockets to capture SACs within 2D-plane while vertically restricting the atomic aggregation into nanoparticulates. High density SACs stably decorated on isolated TMO nanosheet, could be obtained in a controllable manner. Well-defined SACs on TMO were conveniently employed for acceptorless dehydrogenation of a variety of alcohols with quite high activities outperforming reported catalysts. In-depth, mechanistic investigation revealed the dramatic enhancement in acceptorless dehydrogenation reaction rates by following distinct reaction pathways (concerted or stepwise) depending on the density of SACs cooperativity effect. Such advantageous effect is distinct from the reactions on isolated metal sites in low-density SACs or nanoparticle surface.