Uniform single atomic Cu1-C4 sites anchored in graphdiyne for hydroxylation of benzene to phenol.

For single-atom catalysts (SACs), the catalyst supports are not only anchors for single atoms, but also modulators for geometric and electronic structures, which determine their catalytic performance. Selecting an appropriate support to prepare SACs with uniform coordination environments is critical for achieving optimal performance and clarifying the relationship between the structure and the property of SACs. Approaching such a goal is still a significant challenge. Taking advantage of the strong d-π interaction between Cu atoms and diacetylenic in a graphdiyne (GDY) support, we present an efficient and simple strategy for fabricating Cu single atoms anchored on GDY (Cu1/GDY) with uniform Cu1-C4 single sites under mild conditions. The Cu atomic structure was confirmed by combining synchrotron radiation X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and density functional theory (DFT) calculations. The as-prepared Cu1/GDY exhibits much higher activity than state-of-the-art SACs in direct benzene oxidation to phenol with H2O2 reaction, with turnover frequency values of 251 h-1 at room temperature and 1889 h-1 at 60°C, respectively. Furthermore, even with a high benzene conversion of 86%, high phenol selectivity (96%) is maintained, which can be ascribed to the hydrophobic and oleophyllic surface nature of Cu1/GDY for benzene adsorption and phenol desorption. Both experiments and DFT calculations indicate that Cu1-C4 single sites are more effective at activating H2O2 to form Cu=O bonds, which are important active intermediates for benzene oxidation to phenol.

Tunable synthesis of hexagram-shaped hematite iron oxide microcrystals with shape-dependent magnetic properties.

Uniform hexagram-shaped alpha-Fe2O3 microcrystals with tunable morphologies were fabricated by a facile hydrothermal method followed by annealing in air. The highly anisotropic hexagram-shaped alpha-Fe2O3 particles with the higher coercivity forces and remannent magnetizations showed weak ferromagnetic behaviors at room temperature and displayed the typical shape-dependent magnetic behaviors.

Synthesis, self-assembly, and high performance in gas sensing of X-shaped iron oxide crystals.

X-shaped goethite iron oxide crystals were synthesized by a surfactant-free mild hydrothermal synthesis method with the aid of fluorine ions. The X-shaped goethite crystals could readily self-assemble into microscopic hollow spheres through an oil-water interface induced self-assembly method. X-shaped hematite crystals were obtained by phase topotactic transformation of the goethite precursors. The gas sensor properties of X-shaped hematite iron oxide were investigated, and the mechanism for excellent sensor properties was discussed.

Superb adsorption capacity and mechanism of flowerlike magnesium oxide nanostructures for lead and cadmium ions.

A facile method based on microwave-assisted solvothermal process has been developed to synthesize flowerlike MgO precursors, which were then transformed to MgO by simple calcinations. All the chemicals used (magnesium nitrate, urea, and ethanol) were low cost and environmentally benign. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution TEM, and N(2) adsorption-desorption methods. These flowerlike MgO nanostructures had high surface area and showed superb adsorption properties for Pb(II) and Cd(II), with maximum capacities of 1980 mg/g and 1500 mg/g, respectively. All these values are significantly higher than those reported on other nanomaterials. A new adsorption mechanism involving solid-liquid interfacial cation exchange between magnesium and lead or cadmium cations was proposed and confirmed.

Synthesis of cyclic carbonates: catalysis by an iron-based composite and the role of hydrogen bonding at the solid/liquid interface.

Say it with flowers: Flower-like Fe(3)O(4)@Fe(OH)(3) composite catalysts show good activity and stability in the synthesis of cyclic carbonates from epoxides and CO(2). The role of hydrogen bonding between the surface hydroxyl groups of the solid and the epoxides at the solid/liquid interface is proposed as a key factor in activating the epoxide and stabilizing the ring-opened carbonate intermediates.