Boosting chiral carboxylic acid hydrogenation by tuning metal-MOx-support interaction in Pt-ReOx/TiO2 catalysts
ABSTRACT Engineering the surface microenvironment by tuning the binary interactions between a supported metal with a secondary metal oxide (MO x ) or support has been a common method for improving the catalytic performance of supported metal catalysts. However, few studies have investigated the ternary interactions among the metal, MO x , and support. Here, we report for the first time the formation of metal-MO x -support interaction (MMSI) in reducible TiO 2 -supported PtReO x catalysts, affording 87% yield and 100% ee in the tandem hydrogenation of an aqueous chiral cyclohexane-1,2-dicarboxylic acid into the corresponding diol; the catalytic activity is eight times higher than that obtained with non-reducible support counterparts in the same reaction via traditional batch synthesis with multiple steps and unfriendly reagents. Detailed experimental and computational studies suggest that the TiO 2 crystalline phase-dependent density of the oxygen vacancies induces different Pt-ReO x -TiO 2 interactions, which dominate the electron transfer therein and tune the adsorption strength of the carbonyl moiety of the substrate/intermediate, thus promoting the hydrogenation activity and selectivity. In addition, the strong MMSI endows the optimal rutile TiO 2 supported PtReO x catalyst with an outstanding lifetime of 400 h in a fixed-bed reactor under acidic aqueous conditions and ensures efficient applications in the selective hydrogenation of aliphatic dicarboxylic acids and functional carboxylic acids. This work provides a promising strategy for the development of efficient and stable supported catalysts for the selective hydrogenation of diverse C–O and C=O bonds.
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