Direct dehydrogenation of propane (PDH) has already been implemented worldwide in industrial processes to produce value-added propylene. The discovery of earth-abundant and environmentally friendly metal with high activity in C−H cleavage is of great importance. Co species encapsulated within zeolite are highly efficient for catalyzing direct dehydrogenation. However, exploring a promising Co catalyst remains a nontrivial target. Direct control of the regioselective distribution of Co species in the zeolite framework through altering their crystal morphology gives opportunities to modify the metallic Lewis acidic features, thus providing an active and appealing catalyst. Herein, we achieved the regioselective localization of highly active subnanometric CoO clusters in straight channels of siliceous MFI zeolite nanosheets with controllable thickness and aspect ratio. The subnanometric CoO species were identified by different types of spectroscopies, probe measurements, and density functional theory calculations, as the coordination site for the electron-donating propane molecules. The catalyst showed promising catalytic activity for the industrially important PDH with propane conversion of 41.8% and propylene selectivity higher than 95% and was durable during 10 successive regeneration cycles. These findings highlight a green and facile method to synthesize metal-containing zeolitic materials with regioselective metal distribution and also to open up a future perspectives for designing advanced catalysts with integrated advantages of the zeolitic matrix and metal structures.
PtCu-based alloy nanomaterials have shown great potential in methanol oxidation reaction (MOR) owing to the lower cost and good anti-poisoning ability. However, the dissolution of non-precious metal makes them suffer from severe stability issues, greatly impeding the practical application of direct methanol fuel cells. Herein, PtCuIr aerogels are successfully fabricated through a one-step NaBH 4 reduction strategy to anchor trace Ir on PtCu aerogels based on compositional engineering, which serves as advanced electrocatalysts to achieve enhanced electrocatalytic performance toward MOR. Particularly, the optimized PtCuIr aerogels show extraordinary stability and the mass activity maintains 71.2% of the initial value after 20,000 s chronoamperometric measurements. Density functional theory calculations certify that the doping of trace Ir considerably lowers the adsorption energy of CO-containing substances and thus enhances the MOR activity. By employing the vacancy formation energy of the surface Pt as the descriptor, it is revealed that the robust stability of PtCuIr aerogels originates mainly from the stronger bond between Ir and Pt/Cu atoms, where Ir acts as an ″adhesive″ to prevent the dissolution and leaching of atoms. The breakthrough of the highly stable MOR catalyst could open an avenue for affordable and durable fuel cells.
The
aromatization-driven redox-neutral cascade [1,5]-hydride transfer/spirocyclization
and cascade [1,5]-hydride transfer/hydrolysis from para-quinone methide in HFIP were developed. These protocols enabled
the synthesis of azaspirocyclohexadienones and ortho-benzylated anilines in good to high yields under mild conditions,
featuring room temperature, additive-free, and good functional group
tolerance.
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