Ordered single active sites for cascade hydrogenation and hydroformylation reactions

Metal single-atom catalysts offer improved activity and selectivity due to their unique electronic and coordination properties compared with bulk metals. However, many single-atom catalysts suffer from randomly dispersed active sites and limited electron-donating ability due to bonding with electronegative elements or less reactive metals. Here we demonstrate that Mg-rich intermetallic Mg 29 TM 4 (TM = Pd, Rh, Ir, Pt) nanocatalysts overcome these limitations. These materials feature periodically dispersed, electron-rich single-atom sites of noble metals within a uniform chemical environment. Mg 29 TM 4 exhibits high activity and selectivity in C 2 H 2 semihydrogenation (Mg 29 Pd 4 ) and olefin hydroformylation (Mg 29 Rh 4 ), with Mg 29 Rh 4 achieving high regioselectivity for branched aldehydes (branched:linear > 200:1). Kinetic and density functional theory studies suggest that the Mg–TM ensemble enables precise control over carbon–carbon multiple bond adsorption and activation, enhancing both activity and selectivity. Furthermore, the ternary Mg 29 Pd 1.3 Rh 2.7 catalyst, with its synergistic Mg–Pd and Mg–Rh dual single-atom sites, efficiently catalyses a cascade reaction involving phenylacetylene hydrogenation followed by hydroformylation.