Precise immobilization of metal single atoms into a porphyrinic metal-organic framework for an efficient alkene hydrosilylation

Alkene hydrosilylation is one of the most concise and atom-economical methods to synthesize organosilicon molecules. Herein, we reported the precise immobilization of metal single atoms (M-SAs; M = Ru, Rh, Ir, Pd, Pt, and Au) into a porphyrinic metal-organic framework (MOF) of PCN-222 (PCN = porous coordination network), and then applied the resultant MOF composites of M-SAs@PCN-222 to alkene hydrosilylation. Under solvent-free conditions, Pt-SAs@PCN-222 displayed an especially high catalytic efficiency with the turnover frequency up to 119 s-1 and the maximum turnover number of 906,250 at room temperature. Experimental and theoretical studies revealed that there existed strong interactions between Pt-SAs@PCN-222 and the substrates, which helped to condense the substrates in the cavities of the porous catalysts. Further density functional theory calculations and molecular dynamics simulations disclosed that PCN-222 could transfer electrons to Pt-SAs to enhance the silane oxidative addition and drive the reaction to proceed smoothly via Chalk-Harrod pathway.