Tuning the coordination neighbors of the metal center is emerging as an elegant approach to manipulating the performance of supported single-atom catalysts in heterogeneous catalysis. Herein, atomically dispersed Pt species with different coordination neighbors hosted on nitrogen-doped carbon (NC) and graphitic carbon nitride (C3N4) are constructed through an impregnation-activation approach. Advanced characterization techniques including X-ray electron microscopy, X-ray absorption spectroscopy, and high angle annular dark-field scanning transmission electron microscopy reveal the different nature of active sites induced by the hosts: i.e., the Pt-N-x configuration in NC but both Pt-N and Pt-O coordinations in C3N4. H-2-D-2 exchange experiments and electron microscopy further evidence that Pt/NC exhibits a high propensity for H-2 splitting and high thermal stability of the Pt species against agglomeration, whereas Pt/C3N4 cannot dissociate H-2 and the Pt atoms easily aggregate in the reductive stream. Consequently, when applied in the selective hydrogenation of 1,3-butadiene, Pt/NC exhibits higher selectivity to butenes and excellent stability, but Pt/C3N4 behaves as a nanoparticle analogue favoring deep hydrogenation. The superior selectivity patterns of the single Pt atoms over Pt nanoparticles are rationalized by the inversed adsorption strength between the H-2 and 1,3-butadiene molecules at different metal sites, which is substantiated by the kinetic studies.
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