Spatial intimacy of binary active-sites for selective sequential hydrogenation-condensation of nitriles into secondary imines.

ABSTRACT: Precisely controlling the spatial intimacy of multiple active sites at sub-nanoscale in heterogeneous catalysts can improve their selectivity and activity. Herein, we realize a highly selective nitrile-to-secondary imine transformation through a cascaded hydrogenation and condensation process by Pt₁/CoBO_x comprising the binary active sites of the single-dispersed Pt and interfacial Lewis acidic B. Atomic Pt sites with large inter-distances (>nanometers) only activate hydrogen for nitrile hydrogenation, but inhibit condensation. Both adjacent B…B on CoBO_x and neighbouring Pt…B pairs with close intimacy of ~0.45 nm can satisfy the spatial prerequisites for condensation. Mechanism investigations demonstrate the energetically favorable pathway occurred on adjacent Lewis acidic B sites through the nitrile adsorption (acid-base interaction), hydrogenation via hydrogen spillover from Pt to B sites and sequential condensation. Strong intermolecular tension and steric hindrance of secondary imines on active sites lead to their effective desorption and thereby a high chemoselectivity of secondary imines.

SUBMITTER: Zhang S 

PROVIDER: S-EPMC8184996 | biostudies-literature | 2021 Jun

REPOSITORIES: biostudies-literature