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Ultralow Loading Cobalt-Based Nanocatalyst for Benign and Efficient Aerobic Oxidation of Allylic Alcohols and Biobased Olefins
No full textThe synthesis of alpha,beta-unsaturated ketones from aerobic oxidation of allylic alcohols and biobased olefins serves as an important topic in green and sustainable chemistry. In this work, we report the utilization of a sacrificial template ZIF-8 for preparation of mesoporous Co-0.05/N-C material with an ultralow cobalt loading of 0.05 wt %, in which the excellent catalytic performance in aerobic oxidation of alpha-pinene and cinnamyl alcohol was achieved with an 85% yield of verbenone and a yield of cinnamaldehyde, respectively. The results of control experiments and several characterization investigations further illustrate that the sacrificial template ZIF-8 plays a key role to disperse well metallic cobalt in the Co-0.05/N-C-800 catalyst and an appropriate cobalt content of 0.05 wt % is beneficial for benign and efficient aerobic oxidation of various allylic alcohols and biobased olefins. In addition, the Co0.05/N-C-800 catalyst also exhibited good stability and reusability for recovering and reusing at least six times without obvious decrease in catalytic activity. The presented efficient nanocatalyst thus triggers facile synthesis of a series of alpha,beta-unsaturated aldehydes/ketones in high yields
Non defect-stabilized thermally stable single-atom catalyst
No full textSurface-supported isolated atoms in single-atom catalysts (SACs) are usually stabilized by diverse defects. The fabrication of high-metal-loading and thermally stable SACs remains a formidable challenge due to the difficulty of creating high densities of underpinning stable defects. Here we report that isolated Pt atoms can be stabilized through a strong covalent metal-support interaction (CMSI) that is not associated with support defects, yielding a high-loading and thermally stable SAC by trapping either the already deposited Pt atoms or the PtO2 units vaporized from nanoparticles during high-temperature calcination. Experimental and computational modeling studies reveal that iron oxide reducibility is crucial to anchor isolated Pt atoms. The resulting high concentrations of single atoms enable specific activities far exceeding those of conventional nanoparticle catalysts. This non defect-stabilization strategy can be extended to non-reducible supports by simply doping with iron oxide, thus paving a new way for constructing high-loading SACs for diverse industrially important catalytic reactions
High order harmonic generation in solids: a review on recent numerical methods
No full textInteraction of intense lasers with solid materials offers an alternative way to achieve high-order harmonic generation (HHG). Since the underlying mechanisms of the harmonic emission remain uncertain, a large number of theoretical studies have been proposed to explain the experimental findings in this fast-growing field. Here, we review the primary numerical methods and present a brief perspective of HHG in solids
