Yanan Zhu

Hierarchical flowerlike magnesium oxide hollow spheres with extremely high surface area for adsorption and catalysis

Three-dimensionally hierarchical flowerlike MgO hollow spheres with an extremely high surface area of 343 m(2) g(-1) were prepared through a facile and environmentally friendly solvothermal route. The maximum adsorption capacity at natural pH reached 569.7 mg g(-1) for the removal of arsenic in water, which is the highest among all of the reported adsorbents. In addition, flowerlike MgO hollow spheres also displayed excellent catalytic activity and stability for the Claisen-Schmidt condensation reaction as a solid base catalyst.

Nitrogen, phosphorus and sulfur co-doped ultrathin carbon nanosheets as a metal-free catalyst for selective oxidation of aromatic alkanes and the oxygen reduction reaction

Carbon materials have attracted considerable interest as metal-free heterogeneous catalysts owing to their superior physicochemical properties, including low cost, stability, and easily tailorable structures as well as excellent catalytic activity. In this study, we have designed an efficient method to produce ultrathin carbon nanosheets (∼2.2 nm) with multi-heteroatom (nitrogen, phosphorus and sulfur) doping and a high surface area (up to 1198 m2 g−1). This method employs poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) as the main carbon source and N,P,S-doping sources, while g-C3N4 nanosheets act as the morphology template, extra N doping source and porogen. The doped carbon nanosheets are an excellent metal-free carbocatalyst for selective oxidation of aromatic alkanes in aqueous solution and electrochemical catalyst for the oxygen reduction reaction in an alkaline medium.

Surfactant-Free Palladium Nanoparticles Encapsulated in ZIF-8 Hollow Nanospheres for Size-Selective Catalysis in Liquid-Phase Solution

Encapsulation of surfactant‐free Pd nanoparticles (NPs) in the metal–organic framework material ZIF‐8 hollow nanospheres was achieved. Pd@ZIF‐8 hollow nanospheres showed excellent size‐selective catalytic properties in the liquid‐phase hydrogenation of olefins. As a result of the uniform pore size of the ZIF‐8 shell (apertures of 3.4 Å), the catalyst showed high activity for the hydrogenation of 1‐hexene (1.9×8.2 Å) but very low activity for larger molecules such as cis‐cyclooctene (5.3×5.5 Å), trans‐stilbene (4.2×11.3 Å), and triphenylethylene (9.1×9.2 Å). Other surfactant‐free noble‐metal nanoparticles could also be employed to produce NPs@MOFs for catalysis.

In situ facile loading of noble metal nanoparticles on polydopamine nanospheres via galvanic replacement reaction for multifunctional catalysis

Noble metal nanoparticles (Pd, Ag, Pt, Au) with small and relatively uniform sizes were loaded on polydopamine nanospheres through in situ galvanic replacement reaction in aqueous solution. No additional reductant, surfactant or organic solvent was needed. X-ray photoelectron spectroscopy results revealed that the amount of quinone increased, while the amount of phenolic hydroxyl decreased on PDA nanospheres, indicating that the galvanic displacement reaction occurred between catechol groups and noble metal ions. The as-prepared PDA/Pd exhibited high catalytic activity and excellent stability in styrene hydrogenation. Moreover, PDA spheres retains the photo-thermal effect to serve as a nano-sized heater to accelerate the catalytic reactions under near-infrared illumination.

Preparation of Magnetic Tubular Nanoreactors for Highly Efficient Catalysis

We report an efficient and controllable route to prepare magnetic tubular nanoreactors composed of a mesoporous SiO2 shell with iron-noble metal nanoparticles inside. The key of this method is to design and fabricate Fe nanoparticles encapsulated in a mesoporous SiO2 shell. Making use of a galvanic replacement reaction between Fe and noble metal ions, all of the noble metal nanoparticles are loaded inside the mesoporous SiO2 shell, and thus nanoreactors are formed. Taking Pd as an example, the prepared Pd-Fe@meso-SiO2 tubular nanoreactor exhibits a high catalytic activity and excellent reusability for styrene hydrogenation under mild conditions. This study provides a facile route to fabricate magnetic nanoreactors with enhanced catalytic properties.

Size-selective adsorption of anionic dyes induced by the layer space in layered double hydroxide hollow microspheres

Flower-like cobalt aluminum layered double hydroxide (CoAl-LDH) hollow microspheres were synthesized via a one-step solvothermal method without any template. An Ostwald ripening mechanism was proposed for the formation of hollow nanostructures. These flower-like CoAl-LDH hollow microspheres had a high surface area and exhibited excellent selectivity for anionic dyes. The limited space between LDH layers offered size selectivity for adsorbate molecules. For the small molecule methyl orange, the maximum adsorption capacity reached 816.0 mg g−1 under ambient conditions, while for larger molecules such as Eosin B, the adsorption capacity was only 95.1 mg g−1. All these features make the flower-like CoAl-LDH hollow microspheres an excellent adsorbent in water remediation.

One methyl group makes a major difference: shape-selective catalysis by zeolite nanoreactors in liquid-phase condensation reactions

The precise sizes of zeolites’ micropores can induce sharp shape/size-selectivity with precision of less than 1 A in gas-phase reactions, e.g. methanol to olefin reactions (MTO). However, it is still a major challenge and an unachieved task in liquid-phase reactions. In this study, we demonstrate that shape-selectivity with one-methyl-group-precision can be realized in Knoevenagel condensation reactions on basic active sites encapsulated in zeolite crystals. Furthermore, Pd nanoparticles can also be introduced to the interior of hollow zeolite crystals, resulting in a multifunctional and shape-selective catalyst in a one-pot Knoevenagel condensation–hydrogenation cascade reaction.

Excellent selectivity with high conversion in semi-hydrogenation of alkynes using Pd-based bimetallic catalysts

A series of active‐carbon‐supported PdPb and PdCu bimetal catalysts were prepared for the selective semihydrogenation of alkynes in the liquid phase. The Pd0.33Pb0.67/C catalyst showed the best performance for various alkynes under mild reaction conditions (room temperature and ambient H2 pressure) and achieved 100 % conversion with 98 % selectivity to alkenes. In particular, over‐hydrogenation was avoided at complete alkyne conversion.

Controllable synthesis of carbon encapsulated iron phosphide nanoparticles for the chemoselective hydrogenation of aromatic nitroarenes to anilines

Selective hydrogenation of nitroarenes is an important chemical transformation to obtain functionalized anilines as key intermediates for pharmaceuticals and fine chemicals. Compared to the well-studied noble metal catalysts, heterogeneous catalysts based on low-cost transition metals are rarely reported. In this study, we developed an efficient and controllable route to synthesize a new kind of heterogeneous catalyst of iron phosphide nanoparticles encapsulated in a doped carbon matrix for the chemoselective hydrogenation of aromatic nitroarenes to anilines. Making use of the chemical reaction between Fe atoms in a MIL-88B-NH2 core and phosphorus atoms in a poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) shell, iron phosphide nanoparticles encapsulated in a doped carbon matrix were successfully prepared through direct calcinations of a Fe-MOF@PZS core@shell precursor at 900 °C for 2 h under an Ar atmosphere. Due to the relative high surface area and porous structure as well as small nanoparticles, the prepared catalyst showed high catalytic activity, excellent selectivity and recyclability for the hydrogenation of aromatic nitroarenes to anilines.

Chiral Metal-Organic Framework Hollow Nanospheres for High-Efficiency Enantiomer Separation

Chiral ZIF-8 hollow nanospheres with d-histidine as part of chiral ligands (denoted as H-d-his-ZIF-8) were prepared for separation of (±)-amine acids. Compared to bulk d-his-ZIF-8 without a hollow cavity, the prepared H-d-his-ZIF-8 showed 15 times higher separation capacity and higher ee values of 90.5 % for alanine, 95.2 % for glutamic acid and 92.6 % for lysine, respectively.