Intermetallic Pd-Sn Nanoparticles on Supports with High Metal Loading Facilitated by the Metal-Metal Bond for High-Performance Cooperative Catalysis.

Atomically monodispersed intermetallic catalysts comprising highly accessible active sites are ideal heterogeneous catalytic materials. Designing such types of nanocatalysts on carbonaceous supports with high loading, however, remains a formidable challenge. Demonstrated herein is an effective synthetic strategy to produce highly dispersed intermetallic Pd-Sn nanoparticles on various supports with high catalyst loading (upto 24 wt % Pd and 18 wt % Sn) using a discrete bimetallic Pd-Sn complex, which in turn is highly superior as compared to conventionally used methods using individual metal salts. Synergistic cooperative interaction between sub-5 nm Pd-rich particles, supports, and large intermetallic Pd-Sn particles allowed their electronic cross-talk, displaying a much higher reaction efficiency with an entirely different selectivity toward a product, which is highly unlikely in the case of comparable individual components or sequentially impregnated bimetallic materials involving in a catalytic/photocatalytic dehydrogenation, hydrogenation, tandem (de)hydrogenation, and amidation reaction. The designed synthetic strategy has the potential to contribute to the development of atomically monodispersed intermetallic high-loading functional materials for advanced electro- and photocatalytic applications.

Nanoscale Ni-NiO-ZnO Heterojunctions for Switchable Dehydrogenation and Hydrogenation through Modulation of Active Sites.

Catalysts consisting of metal-metal hydroxide/oxide interfaces are highly in demand for advanced catalytic applications as their multicomponent active sites will enable different reactions to occur in close proximity through synergistic cooperation when a single component fails to promote it. To address this, herein we disclosed a simple, scalable, and affordable method for synthesizing catalysts consisting of nanoscale nickel-nickel oxide-zinc oxide (Ni-NiO-ZnO) heterojunctions by a combination of complexation and pyrolytic reduction. The modulation of active sites of catalysts was achieved by varying the reaction conditions of pyrolysis, controlling the growth, and inhibiting the interlayer interaction and Ostwald ripening through the efficient use of coordinated acetate and amide moieties of Zn-Ni materials (ZN-O), produced by the reaction between hydrazine hydrate and Zn-Ni-acetate complexes. We found that the coordinated organic moieties are crucial for forming heterojunctions and their superior catalytic activity. We analyzed two antagonistic reactions to evaluate the performance of the catalysts and found that while the heterostructure of Ni-NiO-ZnO and their cooperative synergy were crucial for managing the effectiveness and selectivity of the catalyst for dehydrogenation of aryl alkanes/alkenes, they failed to enhance the hydrogenation of nitro arenes. The hydrogenation reaction was influenced by the shape, surface properties, and interaction of the hydroxide and oxide of both zinc and nickel, particularly accessible Ni(0). The catalysts showed functional group tolerance, multiple reusabilities, broad substrate applicability, and good activity for both reactions.

Tetrametallic Copper Complex to Nanoscale Copper: Selective and Switchable Dehydrogenation-Hydrogenation under Light.

A discrete, photoactive, ultrafine copper nanocluster of fewer than hundreds of atoms with stimuli-responsive switchable redox-active states is highly desired to control two different antagonistic reactions. Herein, a mixed-valent tetrametallic copper complex (C-1) of N-O-N Schiff base ligand is disclosed, in which the five different Cu-Cu interactions were used to generate photoactive nanoscale copper [LCu0 n , S-1] through the reduction of coordinated imine to the amine of C-1. The presence of a ligand provides stability and helps to homogenize the material (S-1) in the organic solvent. The cluster showed stimuli (O2 /light)-responsive switching between its reduced (S-1) and oxidized [LCu0 n-m CuOm , S-2] states that allows it to serve as a highly and poorly active (bistate, relative rate >5-12 fold) catalyst for the dehydrogenation of alcohols to aldehydes and hydrogenation of nitroaromatics to amino aromatics under the light.