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Actual chemical states of single-atom metal on reducible supports remain a fiercely debated topic under reactive environments. Herein, we demonstrate that the single-atom Pt on Co3O4 surface undergoes an in-situ reconstruction to form isolated Pt-Co bimetallic sites via reducing coordination number of Pt—O in the presence of hydrogen from both simulations and in-situ X-ray photoelectron spectroscopy. The modified chemical states of Pt greatly promoted H2 activation, thus delivering a significantly high turnover frequency of 7,448 h−1 (19.5 times over Pt nanoparticles on Co3O4) for hydrogenation of cinnamaldehyde. The satisfactory selectivity of 95.2% towards cinnamyl alcohol was ascribed to a tilted adsorption configuration of reactant on the catalyst surface via aldehyde group. We anticipate that the recognitions on in-situ reconstruction of single-atom catalysts (SACs) under the reducing conditions benefit the design of highly-performed hydrogenation catalysts. [ABSTRACT FROM AUTHOR]

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/CoBOx 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 CoBOx 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. Precisely controlling the spatial intimacy of multiple active sites in heterogeneous catalysts can significantly affect the selectivity and activity. Here the authors show a binary active site of single atom Pt and Lewis acidic B with spatial intimacy enables a highly selective nitrile-to-secondary imine transformation. [ABSTRACT FROM AUTHOR]

Selective hydrogenation of halonitrobenzenes into haloanilines represents a green process to replace the environmentally unfriendly non-catalytic chemical reduction process in industry. However, this transformation often suffers from serious dehalogenation due to the easy break of carbon-halogen bonds on metal surfaces. Modulations of the electronic structure of the supported Pd nanoparticles on Lewis-basic layered double hydroxides have been demonstrated to promote catalytic activity and selectivity for hydrogenation of halonitrobenzenes into haloanilines. Mechanism studies suggest that Pd with the enhanced electron density not only improves the capability for hydrogen activation, but also generates the partially negative-charged hydrogen species to suppress the electrophilic attack on the carbon-halogen bond and avoid the dehalogenation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Spillover hydrogenation is achieved by constructing the dual-active site catalyst. • Hydrogen and reactants are selectively activated on PtCo alloys and CoBO x support. • The selective hydrogenation is occurred via hydrogen spillover from metal to support. • A high TOF of 2479 h−1 is two orders of magnitude over PtCo/C at room temperature. • A 94.5 % selectivity of cinnamyl alcohol is also obtained at room temperature. Highly efficient hydrogenation of substrates with strong absorption on metals at low temperatures is a long-term pursuit. However, due to the scaling relationship of high binding energies on metals, the poor activity and/or selectivity are frequently observed. Herein, we described a strategy of hydrogen spillover to enable highly selective hydrogenation at low temperatures by constructing the dual-active site in PtCo alloys supported on hydroxyl-abundant cobalt borate (CoBO x), delivering a high TOF of 2479 h−1 (two orders of magnitude over PtCo/C) and 94.5 % selectivity of cinnamyl alcohol at room temperature. Experimental and theoretical investigations suggest that hydrogen and reactants are activated on PtCo alloys and second active sites on CoBO x support, respectively. Hydrogenation sequentially occurs on CoBO x via hydrogen spillover from metal to support. Easy desorption of surface-bounded products substantially re-generates the active sites. Spillover hydrogenation on dual-active site provides a novel strategy for energy-efficiently selective hydrogenation. [ABSTRACT FROM AUTHOR]