Tandem Catalysis of Ammonia Borane Dehydrogenation and Phenylacetylene Hydrogenation Catalyzed by CeO2 Nanotube/Pd@MIL-53(Al).

Heterogeneously catalyzed, selective hydrogenation in the liquid phase is widely used in industry for the synthesis of chemicals. However, it can be a challenge to prevent active nanoparticles (e.g., palladium) from aggregation/leaching and meanwhile achieve high conversion as well as selectivity, especially under mild conditions. To address these issues, a CeO2 nanotube/Pd@MIL-53(Al) sandwich-structured catalyst has been prepared in which the MIL-53(Al) porous shell can efficiently stabilize the palladium nanoparticles. When this catalyst was used in a tandem catalytic reaction involving the dehydrogenation of ammonia borane and the hydrogenation of phenylacetylene, remarkably, the hydrogen released from the dehydrogenation of ammonia borane boosted the catalytic process, with 100 % conversion of phenylacetylene and a selectivity of 96.2 % for styrene, even at room temperature and atmospheric pressure, within 1 min. This work therefore provides an alternative strategy for balancing the conversion and selectivity of liquid-phase hydrogenation reactions.

Metal-Organic Framework (MOF)-Derived Carbon-Mediated Interfacial Reaction for the Synthesis of CeO2 -MnO2 Catalysts.

CeO2 -based catalysts are widely studied in catalysis fields. Developing one novel synthetic approach to increase the intimate contact between CeO2 and secondary species is of particular importance for enhancing catalytic activities. Herein, an interfacial reaction between metal-organic framework (MOF)-derived carbon and KMnO4 to synthesize CeO2 -MnO2 , in which carbon is derived from the pyrolysis of Ce-MOFs under an inert atmosphere, is described. The MOF-derived carbon is found to restrain the growth of CeO2 crystallites under a high calcination temperature and, more importantly, intimate contact within CeO2 /C is conveyed to CeO2 /MnO2 after the interfacial reaction; this is responsible for the high catalytic activity of CeO2 -MnO2 towards CO oxidation.

Surface hydrophobization of zeolite enables mass transfer matching in gas-liquid-solid three-phase hydrogenation under ambient pressure.

Attaining high hydrogenation performance under mild conditions, especially at ambient pressure, remains a considerable challenge due to the difficulty in achieving efficient mass transfer at the gas-liquid-solid three-phase interface. Here, we present a zeolite nanoreactor with joint gas-solid-liquid interfaces for boosting H2 gas and substrates to involve reactions. Specifically, the Pt active sites are encapsulated within zeolite crystals, followed by modifying the external zeolite surface with organosilanes. The silane sheath with aerophilic/hydrophobic properties can promote the diffusion of H2 and the mass transfer of reactant/product molecules. In aqueous solutions, the gaseous H2 molecules can rapidly diffuse into the zeolite channels, thereby augmenting H2 concentration surround Pt sites. Simultaneously, the silane sheath with lipophilicity nature promotes the enrichment of the aldehydes/ketones on the catalyst and facilitates the hydrophilia products of alcohol rediffusion back to the aqueous phase. By modifying the wettability of the catalyst, the hydrogenation of aldehydes/ketones can be operated in water at ambient H2 pressure, resulting in a noteworthy turnover frequency up to 92.3 h-1 and a 4.3-fold increase in reaction rate compared to the unmodified catalyst.

Co Nanoparticles Embedded in Mesoporous Walls of Carbon Nanoboxes for Rechargeable Zinc-air Batteries.

Design of non-noble metal electrocatalysts with high catalytic activity and stability to replace commercial Pt/C is crucial in the commercialization development of Zn-air batteries (ZABs). In this work, Co catalyst nanoparticles coupled with nitrogen-doped hollow carbon nanoboxes were well designed through zeolite-imidazole framework (ZIF-67) carbonization. As a result, the 3D hollow nanoboxes reduced the charge transport resistance, and the Co nanoparticles loaded on nitrogen-doped carbon supports exhibited excellent electrocatalytic performance for oxygen reduction reaction (ORR, E1/2 =0.823 V vs. RHE), similar to that of commercial Pt/C. Moreover, the designed catalysts showed an excellent peak density of 142 mW cm-2 when applied on ZABs. This work provides a promising strategy for the rational design of non-noble electrocatalysts with high performance for ZABs and fuel cells.

Highly dispersed Pt species anchored onto NH2-Ce-MOFs and their derived mesoporous catalysts for CO oxidation.

Simultaneously maximizing the dispersion of noble metals and demonstrating optimal activity are of significant importance for designing stable metal catalysts. In this study, highly dispersed ultrafine platinum (Pt) particles with a size of <1.5 nm anchored onto a mesoporous CeO2 structure have been synthesized by coordinating Pt ions with amino groups in NH2-Ce-MOFs, followed by high-temperature calcination. It was found that the presence of -NH2 groups in Ce-MOFs played a crucial role in anchoring Pt species with high dispersion on the MOF framework. Interestingly, the anchored Pt species were beneficial for the formation of Ce-Pt sites during the conversion from Ce-BDC to CeO2. As a result, the as-prepared catalysts held dense surface peroxo species, responsible for boosting CO oxidation at low temperatures.