Interplay\nBetween Metal and Acid Sites Tunes the Catalytic\nSelectivity Over Pd/Nanodiamond Catalysts

Metal and acid sites are two of the\nmost crucial catalytically\nactive components in heterogeneous catalysis. While variations in\nthe size, morphology, and heterogeneity of metal species, or the manipulation\nof the strength, location, and density of acid sites, could significantly\nimpact the catalytic performance, the combination and interplay between\nthese sites are even more critical and have been a recent research\nfocus. To achieve highly efficient and selective synergistic catalysis,\nit is desired to design a catalyst capable of orchestrating the sequential\ntransformation of all reactants and intermediates at different active\nsites. In this study, we demonstrate that both acid and metal (Pd)\nsites can be introduced onto a nanodiamond@graphene (NDG) support\nparticle through simple air oxidation and metal salt deposition-precipitation\nmethods, respectively. The presence and assembly of these two catalytically\nactive sites significantly alter the reaction network for the cyclohexanol\nconversion reaction. Under this strategy, the selectivity toward designated\nproductscyclohexene, phenol, and benzenecan be precisely\ntuned by the presence and patterning of these two sites on the nanodiamond\nparticles. Specifically, we show that the catalyst with both acid\nsites and Pd ensemble sites, i.e., Pd/NDG, can efficiently convert\ncyclohexanol through consecutive dehydration and dehydrogenation reactions\nto form benzene with high selectivity (>80%). These findings underscore\nthe potential of integrating metal and acid sites to design advanced\ncatalysts with tailored reactivity and selectivity, paving the way\nfor more efficient and versatile catalytic processes in industrial\napplications.