Coupling Cross-Dimensional Ru1–Run Sites in Confined Nanoislands to Overcome the Limitation of Coadsorption and Diffusion in Tandem Reactions

Integrating different reaction sites offers prospects to address the difficulties in single-atom catalysis and helps overcome the limitation of scaling relations for coadsorption. Here, we coupled different dimensional Ru1 and Run active sites on confined Co nanoislands for the reductive amination of 5-hydroxymethylfurfural (5-HMF) to 5-aminomethyl-2-furanyl alcohol (AMF), constrained by the disequilibrium in the adsorption of NH3/H2. Ru clusters trigger an ensemble effect by multipoint-bonding with NH3 and thus become more conductive to dissociate NH3 to NH2* than Ru1 both thermodynamically and kinetically, which releases Ru1 for activating H2 to enhance local H* coverage. Furthermore, intimate active sites in confined spaces enable the timely diffusion of NH2*/H* to react with imine intermediates adsorbed on nanoislands in the di-σC,N configuration. With confined cross-dimensional sites overcoming the limitations of competitive adsorption and diffusion, Ru1+n@Co/MMO exhibits a record-high AMF production rate (295 g·gRu–1 h–1) without the requirement of high NH3/H2 feeding, and it exhibits a mass specific activity even higher than that of single-atom Ru1@Co/MMO.